^^:'i^l8a«i'i!l8|iltl^'^''
S CI i^/v/ o /93f
HARVARD UNIVERSITY
LIBR,A.RV
MUSEUM OF COMPARATIVE ZOOLOGY.
DEPOSITED KV
ALEXANDER AGASSIZ.
-V 73-
;i7Z
J^rjF fc,, zees-
\l t » N n(, i; A I'll
IJIM'I ISII MAIMN i: ANN KI.IDS.
Vol I NKMKI; I IM.A
roLVc II/K'IA AMI'IIIN(»MII).K TO SKiAMONID.K.
WILLI Wl ( \K\11( II \LL M. 1\ lo^ll M !• Km\.. LEr«K. ixit. ras. r«xE. rj.*
PBoraani* or ■4rr«4L ■i»tii«i ■• ma csitUMfrf »r *t *ai>«««* i<i«>t-Ti>« <ir tm* i xiTiKsirt ■raat ■ *■» or m* u«m ■*■!■■ iu«n«Arn«*. >• > . ..••>'i»'. >• > •«>■ - iB*Tirit- ■■rwarKK
T<> T«« T«4«ruau niMMIMIoS raHBB UMIt* !'• r «Tirir ■■■■■*
<»r TUB r«»«(B« k>*BD r»>B -■•il^^v. i»-»;-i»"'-
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*■(• MILK rt
lit I II 4 111 fill ;* luillii Kill 1 L' i \l
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PRINTED BY AULAKll \NI) KON. LONIKIN ANI. liiiKKINU.
COXTKNTS OF VOL. I.
NEMKUTINKA.
KN()IM>A.
AmI'IIII'uKIU.K
Aiiipliiponis
'IVtrastoinina
ProsorliDclunusi
NcllU'l'tl'S .
LiNKiii.t; Linens Horlasiii
ANOI'LA.
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LlNKlD.t: (ctmtinwid) |
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(JiM-ebnituIus |
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155 164 |
Micnini Meckelia |
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174 |
Cakinklliu* |
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17(i |
Carinella |
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Valeiieiiiia . |
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Cei'hai.hthhicikJ'; |
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Cephaldthvix |
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203
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208 21.SA
POLVCH^TA.
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A.MI'IIIMiMin.V. . . . . |
. 219 |
Poi- |
YNOiu.t: (cuiUinued) |
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I'araiiiphinoine . |
. 221 |
Aiitiiioe |
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Kiirytlioe . . . . |
. 224 |
Phyllaiitinoe |
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Spiutlicr . . . . |
. 227 |
iScali.setosus |
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iMil)hrusyiie |
. 238 |
ilaliiigrenia lialdsydiia |
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ArHHuiPiTiD.t; . . . . |
. 240 |
Polyuoe |
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A))hr()(lita . . . . |
. 241 |
iMiipo |
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La;tniatoiiice |
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Acliiilot^ |
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HiTinione . |
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Pol.Y.NolD.K . . . . |
270 |
Faiithalis . |
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Lepidonotus |
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Gattyaiia . . . . |
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SlOALIONlI)* |
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Eunoa |
2!) 1 |
Stiieiielais . |
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Lagisca ... |
2i',s |
Eusthenelais |
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Acantliicolepsis . |
. 311 |
Sif,'aliuii |
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Harinothoe |
. 313 |
Leanira |
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Kvariie |
. 353 |
Pholoe |
I'AiiK
305 370 372 37y 384 389 395 396
399 400
40t» k)7 425 t27 4:!4 4-3t!
• Not iiK-ludiiig the lntii"liutioii, for whidi see pp. ix-xii of Part I.
\
THE
EAY SOCIETY.
INSTITUTED MDCCCXLIV.
T/ih Volume is ismrd /o fhe Subscribers to the Ray Society /o/- t/ie Year 1872.
LONDON
MDCCrLXXIII.
A
MONOGRAPH
OP THE
BRITISH ANNELIDS.
°l/'A • ^ PAET I.
THE NEMEETEANS.
BY
W. C. MCINTOSH,
M.D., F.R.S.E., F.LS., ETC.
LONDON: I'RINTED FOR THE HAY SOCIETY.
MDCCCLXXIII. 5^
PEiKTED nr
J. E. ADrARD, BAHTHOr.OMKTV CLOSK.
TIIK
RAY SOCIETY.
INSTITUTED MDCCCXLIV.
'Flih Volume is issued to the Subscribers to the Ray Socikty fur the Year 1S73.
LONDON
HDCCCLXXIT.
(
^
T
MONOCiKAPll
OF TlIK
BRITISH ANNELIDS.
PART T Continued.
THE NEMEBTEANS.
Pages 97— 213d ; Plates XI— XXIII.
liV
W. C. MCINTOSH,
M.D., F.K.S.E., F.L.S., ETC
LONDON: I'RINTED FOR THE RAY SOCIETY.
MDCCCLXXIT.
MCZ LIBRARY HARVARD UNIVERSITY
"Ambridg^ ma -a
CAMBRIDGE
PEISTED Br J. E. ADLAKD, BAHTHOLOMEW CLOSE.
Jl r b i c a t c ir
THE MEMORY OF
I..
THE AUTHOR'S ARTIST, FELLOW-OBSERVER,
SISTER.
PREFACE.
The following fasciculus may be described as the First Part of a Monograph of the British Annelida, a department of native Zoology which more than any other required investi- gation, and whose neglected condition formed the author's chief inducement to attempt something for its improvement.
So little was known in this country with respect to the Ncraerteans, while their structure and zoological affinities opened up so many interesting questions, that they could scarcely be passed over in such a treatise. Accordingly they have been examined — both in the living and preserved conditions — with as much care as tlic circumstances of the author admitted. He hopes, moreover, tluit tlie publication of the skilful and laborious coloured drawings of the external configuration of these worms (which were so kindly executed by her to whom the work is dedicated) will assist in rescuing them from the comparative obscurity in wliich they have hitherto been involved in this respect, both in Britain and on the Continent. lie has endeavoured to render the other parts of the treatise worthy of the delicacy and beauty of these figures.
The species of the group are, on the whole, distinctly marked, so that comparatively little difficulty has been experienced in discriminating them ; indeed, the chief variation in the majority is in colour, which, of course, obscures none of the essential characteristics.
Considcral)le addition.s may be expected to the list of species subsequently described (though the dredge has been used and the coast-line minutely examined at many points from the Shetland to the Channel Islands), and not a little new matter in regard to anatomy and development ; but, with such a field as the whole Annelida before him, the author could not devote more time to the group. As no freshwater species has yet been found in this country, such a habitat especially should be diligently explored. The author, however, will be satisfied if he has paved the way for a more extensive and accurate study of these beautiful and interesting forms, whose life-histories and structure so amply reward investigation.
The Nemcrteans have received so little attention from British zoologists that the author's list of contributions in this respect cannot but be small, and it is solely to the ceaseless care of a friend that he has been enabled to pursue the investigation with that completeness necessary for the elucidation of their anatomy and zoology, an investigation demanding an abundant and ever- ready supply of healthy living animals. Mr. Parfitt forwarded a few living specimens from the Devonshire coast, and Dr. llowden of Montrose, Prof. E. P. Wright of Dublin, Dr. Gray,
xii PREFACE.
Dr. All)eit Cihitlicr, and the late Dr. Baird of tlie British .Museum, .Mr. G. S. Brady of Sunderland, Dr. Carrington of Ecclcs, Mr. J. ¥. AVhitcaves of the Natural History Society, Montreal, and Prof. Dickie, Aberdeen, have also aided him by the communication of preserved examples or otherwise. Mr. Gwyn Jeffreys included some in his rich collections of Zellandic Annelids, and, in conjunction with Dr. Carpenter and Prof. Wyville Thomson in the celebrated " Porcupine-" Expeditions of 1SG9 and 1 870, he secured a most valuable collection of Annelids and Xemcrteans, which was most courteously placed at the author's disposal by these gentlemen. To all these he begs to return his sincere thanks for their valued assistance, and specially to Dr. A. Gunther, for his exertions in 1869. He has also to remember the many valuable hints in the microscopic department of this work received from the experienced hands of the late Dr. Eraser Thomson of Pcrtli. Nor must he omit to acknowledge the steady encouragement given throughout these researches by Prof. G. Busk, whose cordial support at an early period was a source of the greatest satisfaction.
He has further to thank Professors Dc Quatrefages of Paris, E. Grube of Breslau, Kolliker of Wurzburg, and Van Bcncdcn of Louvain, Mr. Alex. Agassiz of America, and Dr. Malmgren of Ilelsingfors, for their esteemed aid, by the communication of papers and otherwise. Two others, unfortunately, have since been early lost to science, viz. Professors W. Keferstein of Gottingcn and E. Claparede of Geneva. The former did much to place Nemertcan anatomy on a proper basis, and his conscientious original investigations gave promise of great advances in this as well as in other departments. M. Claparede, again, was, perhaps, the most distinguished investigator of the Invertebrates, especially the Annelida, of bis time, and his splendid work both with pen and pencil will make his name enduring.
To the list of these losses he has now to add tiie lamented Dr. Baird, whose excellent labours amongst the collection of Amielida in the British Museum will long be remembered, no less than his genial and kindly aid to all interested in zoology.
For the delay in the issue of this portion of the work — a delay originating in the printing of the Plates — the author is not responsible, since it was ready at the end of 1SG9. He has to thank the Council of the Ray Society for their liberality in regai'd to the Plates, and Mr. Ford for his masterly touch in their execution.
MuRTHLY; September, 1S73.
CONTENTS.
PREFACE ....
GENERAL REMARKS
Physiognomy of the Group
Colour ....
Relation of Colour to Sex
HABITS ....
Native Haunts
Modes of Progression
Method of Preserving Alive in Glass Vessels
Changes which ensue in Confinement
PAOB
vii
4
4 5 6
7
POOD
HISTORY OF THE LITERATURE ON THE NEMERTEANS
ANATOMY AND PHYSIOLOGY' OF THE GROUP Generalized Plan or Archetype
I. ANATOMY OF THE ENOPLA
1. Cutaneous System
2. Body-wall ....
3. Proboscidian Sheath
4. „ Aperture .
42 42
4.3
4:J 45 47
no
z
CONTENTS.
5. Proboscis
A. Anterior Region
B. Middle Region
a. Marginal Stylet-sacs
h. Ejaculatory Duct
c. Central Stylet and its Ajjparatus
d. External Granular Glands
e. Reservoir
c. Posterior Region
/. Varieties in the Structure of the Proboscis : —
Structure op the Proboscis in Amphiporus pulcher
„ „ A. spcctabilia
„ „ A. hasialm
„ „ A- bioculatua
„ „ Tetrastemma melanocephala
„ „ T. Robertiana
„ „ T. Candida
„ „ T. dorsalis .
„ „ T. vermicula
T.Javida .
„ „ Prosor/ioc/imus Ctaparcdii
„ „ Nemeries ffracili)!
„ „ N. Neesii
„ „ N. carcinophila
g. Review of previous Interpretations of the Proboscis
D. Reproduction of the Proboscis
6. Digestive System
a. Mouth
b. Oesophagus
c. Digestive Cavity proper
7. Vascular System
8. Nervous System
a. Ganglia
b. Great Lateral NerA'e-Trunks
9. Eye-specks 10. Cephalic Furrows and Sacs
PAGE
51
51
54 55 57 58 59 59
Gl
63 64 64 65 65 66 66 66 66 66 07 07 68 69
70 74
75
75 75 77
79
81
81 83
84
85
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•V |
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CONTENTS. |
xi |
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riGB |
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11. Generative Syste.m ..... |
87 |
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a. Male Organs ..... |
87 |
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b. Female ,, ...... |
88 |
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12. Phenomena of the Deposition of thk Ova and Spermatozoa |
89 |
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13. Development ...... |
90 |
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ANATOMY AND PHYSIOLOGY OF THE ANOPLA |
9.T |
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1. Cutaneous System ..... |
05 |
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2. Body-wall in the LineiJa .... |
97 |
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„ „ Cariiiellicia .... |
9S |
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„ „ Cej)halothricidcB .... |
99 |
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3. Proboscidian Aperture ..... |
101 |
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4. „ Sheath and Chamber |
101 |
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5. Proboscis in the Lineidm ..... |
102 |
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„ „ Carinellidce .... |
104 |
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„ „ CcphalothricidcB .... |
105 |
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6. Digestive System ..... |
106 |
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a. Mouth ...... |
100 |
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b. (Esophageal Divi.sion ..... |
106 |
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c. Aliineutuiy Cavity proper .... |
107 |
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7. Nervous System in the Lineida .... |
109 |
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„ „ Cariiicllida .... |
110 |
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„ „ Cephalothricidcs |
110 |
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8. Cephalic Fissures ..... |
111 |
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9. „ Sacs ..... |
112 |
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10. Eye-specks ...... |
113 |
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11. Vascular System in the Z//?e/ttfe .... |
113 |
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„ „ Carinellida |
114 |
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1, „ Cephalothricida |
114 |
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12. Organs of Reproduction .... |
lie |
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a. Male Elements ..... |
IIG |
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b. Female „ ..... |
116 |
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13. Mode of Deposition of Ova .... |
117 |
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14. Development of the Lineidts .... |
117 |
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„ „ Pi/liditim-form .... |
120 |
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„ of Cephalothrix .... |
123 |
xu
CONTENTS.
III. REPRODUCTION OF LOST PARTS AND THE ENTIRE ORGANISM
FROM FRAGMENTS . . 125
IV. PARASITES
V. CLASSIFICATION
VL SYNOPSIS OF FAMILIES. ORDERS, GENERA. AND SPECIES
VII. HOMOLOGIES
BlPALIUM
Balanoglossus VHI. GENERAL DISTRIBUTION OF THE NEMERTEANS IX. DESCRIPTIONS OF THE GENERA AND SPECIES
AmPHIPORUS LACTIFLOREUS „ PDLCHER
„ spectabili8
„ hastatus
„ biochlatcs
Tetrastkmma melanocepuala „ Robertian^
„ CANDIDA
„ VEllMICCLA
„ FL.WIDA
„ dorsalis
Prosorhochmus Clapakedii Nemertes gracilis
„ Neesii
„ carcinophila LiNEUS marinus
„ GESSERENSIS
„ SANGUINEUS
„ LACTEUS
,, BILINEATUS
128 130
134
138 142 144
151
153
156 158 160 102 103 165 100 167 169 170 172 174 176 178 ISO 181 185 188 190 191
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//" |
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CONTENTS. xiii |
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rAOB |
||||
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BOKLASIA EuZABETH.Ii |
. 193 |
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Cerebratui.us ANGULATUS |
195 |
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MiCRURA FUSCA |
19G |
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„ FASCIOLATA |
197 |
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„ PURPUREA |
200 |
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„ AURANTIACA |
201 |
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Meckema ASULCATA |
202 |
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Carinella annulata |
203 |
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„ LINEARIS |
206 |
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Valencinia MNEFORMIS |
207 |
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Cephalothrix linearis |
208 |
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APPENDIX |
213a |
COUNCIL AND OFFICERS ELECTED 19th SEPT., 1873.
|)rtsil!tn(.
SIH I'iriLIP DE MALPAS GREY EGERTON, BART., M.P, F.E.S.
cr Itlcmbcrs of Council.
Joseph Beck, Esq.
Dr. B HAITI! WAITE, F.L.S.
Dr. T. Spexceu Codbolb, F.R.S. M. P. Edoewoiitii, Esq., F.L.S. C. H. Gattt, Esq., F.L.S., G.S. Febdinakd Guut, Esq., F.L.S. Dr. GiJNTUEn, F.R.S. Dr. J. B. Hicks, F.R.S. R. Hudson, Esq., F.R.S., G.S. J. GwTN Jeffhets, Esq., F.R.S. H. Lee, Esq., F.L.S.
Sir J. LnBBOCK, Bart., MP., F.R.S.
B. McLachlaj*, Esq., F.L.S.
H. T. Mennell, Esq., F.L.S.
F. P. Pascoe, Esq., F.L.S.
Dr. P. H. Pie-Smith.
Dr. P. L. Sclater, F.R.S.
H. T. Stainton, Esq., F.E.S.
Chables Stewabt, Esq., F.L.S.
Professor Tensakt, F.G.S.
Capt. Chas. Tyleb, F.L.S.
Dr. E. Hakt Vinek, F.L S.
frnsurcr.
De. S. J. A. SALTER, F.R.S., F.L.S., 1, Plowden's Buildings, Temple, E.G. REV. THOMAS WILTSHIRE, M.A., F.L.S., P.G.S., 25, GranvUle Park, Lewisham, S.E.
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THE NEMEKTEANS.
GENERAL REMARKS.
The Nemerteans are elongated non-bristled worms very plentifully distributed on all our coasts ; yet, if not entirely overlooked, they have been generally regarded with a suspicion or aversion even more profound than that ljestowed,on the true Annehds ; apparently, on the one hand, from their supposed resemblance to the forms that live parasitically in the bodies of the higher animals ; and, on the other, from the intricacy of their structure, and the obscurity which shrouded their relations with surroimding groups. The appearance of the large species, indeed, has frequently given rise to feehngs of superstitious wonder not unmixed with dread in the minds of the public ; and some authors even have been more careful to indulge in the same vein in their narratives, than to increase our knowledge of the structure and economy of these interesting animals. They have especially received slight notice from British zoologists.
Cuvier first applied the name Nemertes' to designate the Lineus marinus of Montagu, and several subsequent writers have with propriety given the title Nemerteans to the Order, in which the name has been so long familiar. It is synonymous with the Tcrelitlaria of Dc Blain\ille, the Annclosi Polici of Delle Chiaje, the Cedoidina of ffirsted, the Miocala of De Quatrefages, the Aphcala of Blanchard, and the Turbdlaria BhijHchocala of others.
They have a soft, more or less elongated body, richly ciliated throughout, and the head is usually distinguished from the rest of the animal. The eye-specks and lateral slits (when pre- sent) arc situated in the flattened snout.
The Nemerteans for the most part frequent the sea, though a few aberrant forms occur in fresh water. The British species, so far as yet observed, are all marine ; one of them, moreover, having the semi-parasitic habit of a dweller in tubes attached to the hairs of the abdominal feet of female Carcini. This peculiarity amongst the Nemerteans was first noticed by Delle Chiaje,
' Nemertes, one of the sca-nymphs (Mediterranean as distinguished from the Oceaiiides) — daughters of Nereus ami Doris.
1
2 THE NEJIERTEAXS.
who found his PoUa lelropltlfialmu (a Tefrastemmrt with hirgc eyes) in great abundance in the respiratory cavity of " yfucidia wnviwellata." Leuckart and Pagenstecher also state that the former got at Nice a pale Tetrasleiniiin in all the stages of egg, young and perfect animal — living parasitically in the body-cavity of PIiuUuhui mamilhiris ; such, however, in all probability, being only a coiilirmatioii of tlic foregoing. A. Agassiz, again, found a species of Plit/inria, which he thinks identical with the Planaria angulata of Midler, on the under surface of the base of the fail ill L'nnulus. This habit liad also been observed in another Planaria, that frequents Veh'lla in tiie Atlantic, l)y Lesson in his /oology of the ' Voyage autour du ]\londc snr la corvette La (,'oquille ;' and by Schneider in the case of Anoplodium parasila (one of the Rhab- dococla), which inhabits Jlolothuria iuhulom. Further observations will in all likelihood lead to the discovery of parasitic species in the Medusae. Such do not seem to be true parasites like the Entozoa, but may ajjpropriately be grouped luider the comprehensive title " Commensalisnie," reeeiitiy constituted by Prof, van Ikneden — in an interesting lecture delivered before the Royal Belgian .\cademy. The animals included under this head do not ])rey ujjon the juices of their hosts; iiiit, like tlic Adanma attached to the shell containing the Pngurm, or the accompanying Nereilcpas, tliey simply live together for their mutual comfort and convenience.
Comparatively few specimens, and these generally the largest forms, are to be found in our museums ; and even such examples, if named at all, are often specifically confounded, the same animal, p.//., Lineus marinus, being characterised by many names. In looking over such col- lections, indeed, one meets with a curious nomenclature; thus I have found a large Sipunculus labelled ' Scrpcnfaria,' a Bipaliuiii ' Jlech'/iri,' an elongated S//Nri/jfa and a Tania rcs|)ectively termed 'Lineus,' and not a few distinguished by the anil)iguous title of 'leech.' This confusion is partly due to the great changes that ensue on placing the animals in spirit. Specimens mea- suring feet or even yards in length shrink to short processes a few inches long, and the contour of the head is often indistinguishable on account of its retraction within the anterior portion of the body. Moreover, altiiough the worm is in a manner preser\'ed, it is generally unfit for dissection, and the colours freciueiitly fade. While difficulties thus beset the investigator of specimens in museums, the obstacles to the satisfactory examination of the living forms are scarcely less per- plexing ; and though I would not fully endorse the description of Sir J. Dalyell, yet there is much truth in his observations: — "That many woiTUS have no external prominences rising above tlic smoothness of their skin, or depressions sinking into it. That neither specks nor eyes, nor the position of the mouth can be discovered in the living specimens ; that the student of animated nature cannot destroy his subject, and if perishing in his possession, it often goes so speedily to decay, that it is impossible, w'ere he even a skilful anatomist, to avail himself of dissection."
The colours of many species of the group are of such beauty as to attract even the casual observer, while in tliis respect also they widely deviate from their supposed allies the parasitic worms. The richest purples appear on velvety skins of deep brown or black, each of the soft and nioliilo2,folds giving shades that vary in intensity and lustre. Bright yellow contrasts with dark brown ; white w ith veruulion, brown and dull pink ; while individual uniformity is charac- terisetl by such hues as rose-pink, white, green, yellow and olive, the gradations of colour in the various parts of a single specimen being so subtle that enthusiasm as well as skill is necessary in the artist who sets himself to the task of faithful delineation. Our indigenous species as a whole do not seem to be less brilliantly coloured than those of warmer climates, if we may judge from
GENERAL REMARKS. 3
Sclimarda's plates, and the descriptions of other authors. Thus as regards beauty and variety of colouring the Neniertcans vie with any other grouj) in the invertebrate series ; while in the silky sheen and ever-changing iridescence of the active cilia, with which their whole bodies arc covered, they surpass in some respects tlieir gaily tinted superiors — the true Annelids.
The sexes of the Nermeteans do not appear to be distinguished by any peculiarity of shading, except where the ova or spermatozoa are observed through the translucent tissues of the adults. Tiic reflections in regard to the bright colouring of these forms are somewhat cursorily treated by Mr. Darwin in his recent work.^ These animals, he says, like naany other invertebrates, " appaienlly stand too low in the scale for the individuals of cither sex to exert any choice in selecting a partner, or for the individuals of the same sex to struggle in rivalry." The Nemerteans, however, are not devoid of sexual instincts, and the deposition of ova by a female, even at some distance from the male, gives rise to the immediate discharge of his special secretion. Thus ]Mr. Darwin would be furnished with the facts for stating that the best developed and most forward individuals would have most chance of securing numerous and healthy progeny. Their colours are not due to blood or bile, but arc strictly skin-products, yet it would be as easy (or as ditiicult) to prove them advantageous to the creature as to demonstrate that the pale blood of some animals, the green or red of others, has been formed (as to colour) by natural or sexual selection. Indeed, there is scarcely a limit to the range of theory on such subjects, and it is hard to decide the one way or the other. The argument that the bright colours may be of use in leading their enemies to recognise them as unpalatable will scarcely suit, since fishes feed readily on some of the brightest. Neither can the proposition, available in the case of the soberly clad bhnd beetles, be of service, since some of the most gorgeously tinted {<■.()., Carindla annnlatuwiA Linens bilineatus) are devoid of eyes ; nor are the animals coloured in any special manner so as always to resemble their surroundings, as may be noticed in the olive-green and reddish varieties of Z///c/is(/essereMsis. Tcfra-ifcu/ma Candida, on the other hand, assumes a greenish hue in certain instances amongst the littoral algge, and the food of the translucent Cepludotlirix has a wonderful effect in colouring the cells of its alimentary region. Some of the most vividly tinted species live in obscni'e" crevices and creeks, where light can rarely enter. The bright reddish ova, again, of JiiipMjwrus 2Mlc!ier, which shine through the pellucid integuments, must render the female for a period a more conspicuous object than the male or undeveloped animal.
Though Prof. Grnbe's boatman saw the head oi Linens mariniis 'shine,' and ^ iviani states that Pliinaria relusa is uniformly luminous, none of the Rritish Nemerteans show this property.
There are, so far as at present known, thirty-one species of Nemerteans inhabiting the British Islands, and described in the following pages. The majority have been previously found ; a few are new to Britain or to science.
' ' The Desceiit of :M;ui.' &c.
HABITS.
HABITS.
In their native linunts these animals exhibit considerable diversity of Iiabit. The majority, however, live under stones tliat lie on a muddy or sandy l)ottom, between tide-marks, eitlier in pools or moist phiccs, and, as scarcely a vestige of them is at any time seen unless a stone is upturned, tlieir period of activity is probably during full tide. As their haunts indicate, they are fond of the shade, but I do not know that for this reason they are to be called, after Do Quatre- fagcs and others, nocturnal aniniiils. Thus Linens viarinus is observed occasionally gliding amongst the seaweeds of a warm and sunny tide-pool.
Hundreds of some of the common forms, such as Lineus ffcsserensis and Cephalothrix linearis, may be found under a single stone, sometimes in tangled masses, amidst the muddy sand so common in such ])laces. Tclrantcmnia ilornalis is gregarious, in vast flocks, on Ceramiinn and other alga- dredged in the Laminarian region ; and Prosorhochmus Claparedii is frequently found in groups in fissures of the rocks near low-water mark in the Channel Islands. Lcidy, in his ' Marine Invertebrata of Rhode Island and New Jersey,' also describes his Nemerlcs socialis as very abundant, often in masses, about the roots of corallines, between tides, at Point Judith. The larger and rarer forms occur either singly or in pairs, such as Nemcrtes Xeesii and Micrura, which haunt tlie fissures of rocks near low-water mark. The great Linens viarinus, again, is often solitary, and the largest specimens almost always so, as well as limited in numbers — size, as in some of the higher forms of marine life, being thus inimical to profusion ; and it may be noticed that a diligent search for a lengthened period in one locality diminishes verj' scnsiljly the number of large examples. Other Nemerteans frequent the coralline ground or its neighbourhood, such as Micrura purpurea. Cerebral ulus anijulatus, Aniphiporus pulclier, and A. speciahilis, and they are partial to empty bivalve shells. Stones placed near the verge of low water, and covered with a profusion of algous and zoophytic life, furnish numerous specimens of the small Tetrasfemmce, which apparently dcliglit to crawl amidst the roots and branches, no doubt attracted by the abundance of tiie other animal organisms that like themselves seek shelter and safety in these miniature forests. One of the best modes of collecting such small forms is to chip off at the proper season — for their abundance is probably periodic — shelving fragments of rock, and carry them home for immersion in shallow vessels of sea-water, when the worms leave their retreats and crawl to the water-line of the basin, after the manner of Itissoce, Slcenece, and other small Mollusca. The same may be said of the roots of the tangles dragged from the rocks near or beneath low-water mark, such treatment being often the only safe mode of procuring perfect specimens of Carinella annulata, JS'emertes Neesii, and N. (/racilis, which generally inter- lace their lengthened bodies with the radicles. No richer ground for Nemerteans of rare size and beauty probably exists than the intricate roots of the vast tangles that envelop the muddy masses of horse-mussels in Bressay Sound, where Forbes and Jeffreys have each done such good work by aid of the old drag of the Zetlandic fishermen. Colonies composed of examples of different species, such as Lincus marinus, L. gesserensis, Micrura fasciolafa, JL purpurea, IVeuwrfes IVeesii, and Amphiporus pulchcr, are occasionally met with in the same root; while the hollows of the rough roots of Laminaria bulbosa give shelter to select pairs or solitary individuals.
UAliiTS. 5
Empty liinpct-sliells that acUurc to the under stirfacc of stones in tidal pools are also favourite liirkiiiL; places for these aiiiuials. Although many of the smaller forms fashion gelatinous or inenibianons tulles with faeility on sea-weeds and stones, one Hritish species alone may he said to inhabit a tube or burrow not secreted by itself, viz. Borhimi ElisahelkcB, which was found at Tlcrm in a jjit or burrow of clay; and in tliis, as in other respects, the species is jjeculiar. A foreign example, the Slbvpnonia aurantiaca of Girard, is also stated to dwell in vertical tubes in sand, near Fort Johnston, Carolina.
The group, as a whole, is composed of animals l)y no means inactive, for they glide swiftly about in their native sites, only their length sometimes proves a l)arrier to their rapid disappear- ance from a particular spot. Crustaceans, starfishes, and nioUusks, indeed, are but clumsy athletes when compared with the Nemerteans, whose bodies, dc])rived of all external ])roteetion, covered with cilia and endowed with exquisite sensibility, seem the very essence of mobility. On a solid surface, the chief mode of progression is by crawling, the body being thrown into a number of minute undulations, or else rendered more boldly moniliform by evident waves, which pass from the snout backwards. Some of the more active small species, again, such as Tetrasfemma caiididti, frequently glide over the surface of glass so smoothly that scarce a wrinkle is noticed in the soft outline of their bodies, which, for the time, seem to be propelled by an invisible agency. In progression, the body is extended in a rectilinear manner, or else thrown into one or more graceful curves ; while the snout is closely applied to the surface, or occasionally rolled from side to side. If a Nemertean, for example, Jiiiphiporiis lactijloreiis or Linens yesiiercimk, is raised from the surface on which it crawls, it will generally be observed that it clings most pertinaciously by the anterior end ; indeed, it would appear that the lips exercise a kind of sucker-action, or, at least, that the under surface of the flattened snout does so. The bodies of several of the elongated forms resemble a semifluid yet coherent substance that can be drawn through any aperture, bent romid any angle, and looped, coiled, or twisted in the most elaljorate maimer. In the more slender species, such as Cepludoihrix linearis, the mobility greatly resembles that of the tentacular processes of the Tercbella, and I have been puzzled at least once, on lifting stones and sea-weeds from the dredge and placing them in water, by the independent and Nemertean motions of the spotted tentacles of T. nehuhsa, the owner of which was for the time invisible. In the same species the living animals in confinement often group themselves into rounded masses, which become veritable Gorgon's heads when the constituent members push forth their struggling snouts. The larger kinds also, such as Ncinertcs Neesii and N. yracilis, follow a similar habit ; and, when the water is changed, it is an interesting sight to watch the heads of the individuals slowly emerging, softly and with ease, from the apparently inextricable coils. In few other groups bf animals can such extreme conditions ensue between contraction and extension, and this not by the agency of sea-water, but by the extraordinary shrinking of the muscular substance, and the mobility of the other tissues of the animal. Specimens, measuring only a few inches in contraction, stretch with ease to the length of several feet ; and irritants cause a large Linens marinus, several yards in length, to shrink without injury into as many inches, while shorter forms become quite baccate. If a large example of the last-named Nemertean be held over spirit, the body seems to disappear swiftly on touching the liquid, and the hand with the sluiuiken mass lapidly ap[)roaclics the surface. On viewing the motions of these animals, the observer will often be forcibly reminded of the graphic descriptions of the arms of Plcurobrachia, given by the elder Agassiz.
6 HABITS.
Like many of tlu; tnu; Annelids tliey also progress by floating on the surface of the water, either erawling up the side of the vessel, and thereafter pushing their snouts outwards from the water-line ; or, if the water is shallow, raising their heads upwards from the bottom and gradually extending their snake-like bodies along the surface. As in the case of the Nudibninchiate .Molliisca, a track of mucus is constantly left behind them in this position, and in the same mMmur tliey can be suspended by it. So abundant, indeed, is this mucus, that in jars containing numerous vigorous specimens of Linem gcsHerenms a perfect gelatinous mesh- work is formed nciar the surface of the water, and even throughout the entire vessel. I had carefully tested by personal observation the correctness of the explanation given by Messrs. Alder and Hancock of the modus operandi by which the Nudibranchs crawl on the surface of the water, and the same explanation is very evidently applicable to this class. The adhesion of the body to the mucus gives the animal sufficient purchase for the use of its facile muscles, for it need scarcely be mentioned tliat the water has no influence in lessening the attachment. Hence the remark of M. de Quatrefagcs, that NcmerlcH glides through the water by means of excessively fine vibratile cilia, which me protruded from every part of the surface of the body, caimot meet with our support. When anxious to view the ventral aspect to advantage, no difficulty has been experienced in making many thus float on the surface of the water in the shallow trough of a large dissecting microscope, for by constantly irritating the animals in their endeavours to crawl along the bottom of the vessel, and arresting their progress, they at last pushed their snouts upwards, and sought refuge by this mode of progression.
While possessing the power of crawling and floating just mentioned, some species also swim freely through the water, and this habit in Britain is especially characteristic of the fonns which inhabit deep water ; indeed, I am not at present aware that littoral species exhibit it in any degree, though there is nothing inimical in their conformation. This habit has been noticed in the Ccrebratulus viart/iiialus of Nardo, the Meckelia aiiraiiliaca of Grube, and by M. de Quiitrefages, in his Polia bembi.r, dredged off" the coast of Sicily. Four British species, as far as at present known, show this mode of progression, viz. Jmphijjorm spedabilui, A. pulcher, Micrura fusca, and Cerebraliilus (inguUitus. \Vhen irritated, each throws itself on its edge, and by alternate lateral strokes of the tail propels itself rapidly through the water with a serpen- tiform wriggle. Thus, tlicir mode of swimming closely resembles that of the freshwater Kcplidh, and difl'ers from the horizontal flapping of their allies, the Planaria?, which M. Duges compares to the motion of the Kays. The British species above noted are characterised by their somewhat short and broad form, and especially by the production of the lateral margins into a thin edge throughout the greater part of the body.
Many of the Xemerteans, as [Nl. de Quatrefages mentions, are very hardy in confinement, Tf the observer is at all experienced in the management of such animals. It is not by the well- calei dated adaptation of plant to animal life, of nicely balanced conditions supposed to be favourable to the healthy continuance of marine existence in these artificial states, that the experiment is always successful. Pure sea-water in clean glass vessels, and, in some instances, a clean shell w empty Bahinus, with a little sand or gravel on the bottom, constitute the most suitable aquaria. Unless the vessel is large, only one or two examples shoidd be placed in each, and this is a point of great importance ; indeed, in the case of rare or valuable specimens, solitary confinement has generally been resorted to as most advantageous. I have thus been enabled to keep alive at a great distance from the sea-coast numerous individuals of Linens marinus, L.
11 A HITS. 7
ffessereiisis, L. sanguineus, Amphiporus lacliflomus, Micrura jmrptirea, M.fftsciolnta, and others, as well MS to observe various interesting phases in their development. The vessels were always placed in a cool, and, if possible, in a darkened position, in accordance with the habits of the animals in tiieir native sites ; but the sea- water was not changed more iVei[uenlly than I'onr or ti\ c times a year, and in some cases not at all. Such confinement generally blanched the snout oi Lineus mnrinm, so as to render the groups of eyes visible. The pallor of the up|)er and under surfaces of the snout in this sj)ecies is peculiar, for the other parts of the animal are not ali'ected. It occurs chiefly in the region of the cephalic sacs, across the entire breadth of the snout, and extends forward at the margins to the tip ; the pigment of the centre of the snout anteriorly, both dorsally and ventrally, and the reddish hue in the region of the cephalic pits remain. I have kept this species, indeed, so long that the snout has become completely etiolated, with the exception of the eye-specks and the reddish coloration of the cephalic fissures. Moreover, throughout an inch of the anterior part of the body, the ventral surface had assumed a pale pink colour, and the six dark stripes on the dorsum were separated by a ground-colour of the same pale hue, which, besides, here and there interrupted the longitudinal dark bauds. In the instances, again, of Amphiponis ladijloreus and the pale Tetrn- stenmcc, the opacity of the cutaneous textures is considerahly increased ; and as the two latter are generally best adapted for the investigation of certain minute details, it always became necessary to send to the rocks for a fresh supply. This opacity in the pale species is due to an increase of yellowish colouring matter in the cutaneous cells, and the deposition of brownish-red pigment, a change probably arising from a more frequent exposm-e to the sun's rays. In some specimens of A. ladijloreus under these circumstances, a general augmentation also occurs in the reddish pig- ment of the ganglia and anterior portions of the lateral nerves. A similar alteration ensues in other species, such as Carindla annulatu and Linens bilineatus, the former changing from pale brick- red to deep brownish red, and the latter from pale-pinkish buff to brown, thus intensifying the contrast with the pure white lines present in each case. This variety of tint, from exposure or seclusion, likewise occurs in their native hamits. Thus, for example, specimens of YA'(?w/t';-/f.yi\ee.!)//, from a chiidv in the Gouliot Caves of Sark, have a much paler aspect than those from an ordinary tidal })ool. The rule, however, has many exceptions, for in the same caves very dark olive speci- mens oi Linens gesseretisis S.XQ found, while a variety of a pale reddish hue lives under stones beneath the open sky at the mouth of one of them. After protracted confinement without food, the longer forms generally lie coiled in an intricate mass on the bottom of the vessel, or, if only moderately elongated like Micrura, rest as a double band, and th(;ir bodies diminish in bulk to a very great degree. Under the same conditions the smaller species, such as Tetrastemma and Promrltodiinus, are often found at the margin of the water, and some having receded too far from their element become dried on the side of the jar. The latter accident especially occurs amongst groups of recently captured specimens, which have not yet attained the experience necessary for their preservation in this artificial habitat. Some sustain life under almost complete abstinence for very long periods, such as a year or eighteen months, their bodies being apparently supported by the slow absorption of their own tissues, so that, as before mentioned, their size is greatly reduced. There is, indeed, no structure in the bodies of the majority that is not capable of such change, and thus decrease, in every respect, is easily attained. I have not snflicient facts to enable me to make generalisations on the subject of their longevity ; but the larger Nemerteans, e. (/. Linens wnrinns, Tj. gesserensis, and Z. snnguincus li\e for several years, even under very unfavourable circumstances, in confinement. With ordinary care, also, they can be
8 FOOD.
carried alive from remote parts of the country, as from the Channel Islands to Scotland, and from Slictliind, witliout the loss of a single example of any of the species.
If, tlicreforc, animiils so large live for a protracted [)eriod in very limited supplies of salt water without a trace of food, our wonder is diminished at the apparent paucity of nourishment in the abysses of the Atlantic for the sustenance of the Foraniinifera and other minute organisms mentioned by Dr. Carpenter, since, putting aside for the moment the dissolving jellies and ciliated young of certain of their neighbours, they have free access to the trackless ocean and all its contained organisms.
Under certain irritants, as, for instance, great impurity of the water in the case of recently captured animals, the common Linetis gcHserensis turns itself inside out, so that the inner surface of the digestive chamber can be viewed without dissection. This also occasionally occurs on placing it in alcohol. The extreme shrinking of Lincun iiKirinim on iiiinicrsion in spirit is also some- times due to a literal doul)ling of its body, one fold of which is tlirust within the other, the outer being in its normal position, but the inner having its alimentary surface external. Cephalothrix linearis is killed by fresh water in a few minutes, the body being swollen by contraction and con- torted. Aniphiporus laciiforcnx lives a little longer, though it never moves from the spot, and only thrusts its snout hither and thither for a short time, and dilates its mouth. Lineus f/ctsscreims does not crawl after immersion, but lies helplessly on the bottom of the vessel, a swollen body- wave piK'ising rapidly from before backwards for some seconds, as if sickly, then all is still. In most cases, as noticed by M. de Quatrefages, a copious exudation of mucus takes place, and disintegration speedily ensues, the specimens becoming pulpy in a few hours. Tiicy are not less hardy, however, than the higher Annelids under the same circumstances.
FOOD.
The Nemerteans throughout ai-e a carnivorous and predaceous race, either capturing living prey or devouring suitable portions of dead animals. Sir J. Dahxll observed Linens marinus and his Gordiiis minor viridis icc^m^ on frasrnicnts of mussel, the former also entering the tube of AmjihUrUe [Sabella) to devour the tenant, and M. de Quatrefages (after Cuvierand others), in his " Rambles," * narrates that the former species is neurished by sucking the Anomia, a feat, however, that seems to me to be involved in obscurity. The erroneous interpretation of the proboscis of the Enopla (which he took for an alimentary organ) of course exonerates M. de Quatrefages in a manner from criticism in regard to the feeding of the animals. It may be observed, however, that the thrusting out of the proboscis noticed by him in Polia mandilla {Amjilnporus lactifloreus) may have been due to other causes than hunger, and that the adherence of the same organ to a Cyclops for a quarter of an hour may be otherwise explained than on the sup- position of suction. !Mr. Kingsley gives a very graphic but not ver}' accui'ate (since he says the proboscis assists in prehension) description of a specimen of the same species in the act of devouring a fish. Lineus marinus, indeed, would appear to have a very indiscriminate appetite, for not oulj' does it devour its vertebrate and bristled superiors, but a specimen in the island of Herm swallowed an example of Ascidia intcsfuialis about an inch long and half an inch broad, which had been put into the same vessel. Mr. William Thompson, who did so much for the fauna of Ireland,
1 Escelleutlv translated by the accomplished Miss E. C. Otte. London, 1857.
HISTORY OF THE SUBJECT. 0
mentions that Captain Fayrcr, R.N., got an individual of the same species holding on to a bait of B/'ccuiiim lanlatinn on his long line, while fishing for cod off Portpatiick. In confinement the LincidcE readily feed on fragments of mussel. As soon as a specimen has come in contact with a suitable portion, the mouth is enormously dilated, the inner surface of the first part of the oesophageal region thrust outwards, and the bolus, although of considerable size, rapidly swallowed. The snout of the animal during this process is curved backwards, doubtless to afford assistance by its tactile properties, but there is no extrusion of the proboscis. They also feed on dead specimens of Nereis jiclagica, JIarmothoe. imhricata, and other annelids, ejecting the bristles and indigestible portions /;<??• anion, and tlie only inconvenience which they suffer from the spines and bristles is an occasional perforation of the digestive tract and body-wall, and the formation of a vesicle in the cutaneous textures, through which the offending structures arc by-and-by extruded. One specimen of L. r/esse/'ensh under examination boldly seized the head of a large Nepldh>j>i, upwards of an inch longer than itself, and partially engulphed its prey. IMany, moreover, greedily swallow their fellows, and hence it is dangerous to leave examples of rare specimens together in a vessel, as the larger generally make a meal of the smaller. While thus predatory and voracious, they are in turn tolerant of much injury ; for instance, a specimen of L. gesHcrensis had its head and anterior portion seized and confined in the stomach of a Scifjarlia troyhdytes for about ten minutes, yet the worm afterwards got free, and crawled about as if nothing had happened. In CepJialothris the contents of the digestive tract are easily observed, and in confinement often consist of frag- ments of each other. I have not been so successful in seeing the Enopla feed, but they probably take similar novuishment. Several of the large forms, such as Linens hilineaius, have been found in the stomachs of haddocks and flounders caught oft' St. Andrew's Bay.
Their hardihood when confined in vessels without food has alrcadv been described.
HISTORY 01' THE LITERATURE ON THE SUBJECT.
The early authors on Zoology, while conversant enough as a rule with a few of the con- spicuous Annelids, altogether omitted to notice the Nemertcans. Thus no mention is made of them by Linnaeus, Scba, Blumenbach, Svvamnierdam, and others.
In 175S the Rev. William Borlase, F.R.S.,' introduced the Nemertcans to our fauna l)y the following description of Linens jnariniis : — "Eig. xiii, Plate xxvi, is the long worm found upon Careg-Killas, in Mount's Way " (Cornwall), " which, though it might properly enough come in among the anguilli-form fishes, which are to succeed in their order, yet I chusc to place here among the less perfect kind of sea animals; it is brown, and slender as a wheaten reed; it measured five feet in length (and perhaps not at its full stretch), but so tender, slimy, and soluble, that out of the water it will not beiu- to be moved without breaking; it had the contrac- ^tile power to such a degree that it would shrink itself to half its length, and then extend itself as before." A rough engraving of L. marinus accompanies this account.
Certain " marine insects " from amidst Sertularians and other Corallines are represented in Tab. iv of Raster's " Opuscula," - vol. i, 1702, one of which, fig. 9, is a Nemertean, probably Tetrastemma Candida. No further mention is made of the animal.
1 ' The Natural History of Cornwall,' p. 2.")5, tab. 20, f. 1.3. Oxford, 1758. - B.\sTEKj 'Opuscula Subscciva.' Haarlem^ 17G2.
10 HISTORY OF THE SUBJ?:CT.
P. S. Pallas,' ill tlic year ITCH, (k'scrli)C(l a Nemerteau of a bluish-whitc colour under the name of Lumbricus uxyurus, which I am inclined to identify with Amphiporm laclijlorens, from a carcfnl examination both of the fignrcs and text. He mistook the proboscis for an intestine, as jiiaiiy snbsccjucnt anthors have done, Imt he observed that the organ was bathed in fluid, thus recognising a very important element in the anatomy of these animals. He interpreted the stylet- region as the stomach, and detected three mu.scular bundles proceeding from the posterior end of the latter, so as to. fix the organ to the integmnents. The intestine, again, terminated in an anus at tiic anterior pore. The medulla or nervous trunk fonned a simple white cord, he said, without ganglia. AVhilc there is much that is erroneous in the foregoing description, there is also a con- siderable amount of penetration and judgment evinced by the learned author, for he appears to have made out the jjroboscidian fluid, the dilated region of the stylets, and the muscular ribands; and it is clear that this observer would not have omitted to notice the mouth and lateral fissures if his specimen had been a typical form of the Anopla. In the same work" he also figures a Ncraertean resembling Linens i/essereiiais, but the only reference thereto occurs in the explanation of the Plate, viz., " Alia Luuibrici marini species, tota atra."
The next important contribution Avas from the ])cn of the distinguished naturalist, O. F. Midler,-' who in the first part of his "Vcrmium," published in 177;5, grouped the Nemerteans under the Second Division of his worms destitute of tentacles (Serpentes), and in the third head (Mutica). In his second part, published in 1774, they were included, along with Gordius, Ascaris, llirudo and others, in the first subdivision (Mutica) of his Gens Ilchninthica. Three or four of the counuon species were for the first time described (some of them more than once) as Fasciola.
In the new edition of his " Natural History of Fresh and Salt Water Worms,"* published in ISOO, the same author describes a single example of the Lineida- imder the name of ' Der Strci- mische Rod-Aat,' a species no doubt identical with Linens ffesserensix. He did not discriminate structure further than by supposing the lateral slits at the anterior end to be connected with the anus, and the ventral papilla (mouth) the male organ of generation. His figures are quite recognisable.
This naturalist-' in a subsequent publication (1770) enumerates the Xcmerteans under his sixth Class (Vermes), and third Order — Mollusca. It is difficult to determine with precision the species referred to in this work, unless in those cases in which further mention in the " Zoologica Danica" confirms the diagnosis. He arranged them with the Planariac according to the number of eyes, but erroneously placed Lineus (/esserensis, Amphiporus pulcher, and others, under the group of eyeless forms.
The acute and painstaking Dutch naturalist, Martin Slabber," noticed a Nemertean, under the name of Gordius marinus, which is evidently one of the Anopla, having in his figure (where
1 P. S. Pallas, 'Miscellanea Zoologica,' pp. IIG — 14", pi. 11, figs. 7 and 8.
= Op. cit, p. 216, pi. 11, fig. 9.
3 0. F. MuLLER, 'Vcrmiuru Terrestrium et Fluviatilium.' Havniae et Lipsise, 1773-4.
-• ' NaturgcschicLte einiger Wurm-Arten des siissen u. salzigeu Wassers.' Neue Ausgabe. Ko- penhagen, 1800.
^ O. F. Mdller, ' Zoologiffi Danicae Prodromus.' Havnise, 177G.
<^ ' Natuurkundige verlustigingen behelzeude microscopise -n-aarneemingen,' &c., Blad. 61, PI. 8, f. 1. Haai'lcm, 1778.
illSTOllY OF THh: SUBJECT. " U
tlu' animal is seen on its edge) a conspicuous lateral fissure. It appears to be related to MicruTU J'usea.
In 17S0, Otho labricius/ following O. F. Miillcr, placed the Nenicrtcans in the genus Planaria, under his sixth Class "Vermes." lie mentions Planaria uvyulata, P. rubra, P. viridis, P.fiisca, P. caudata, and P. Candida, most of vvliicli had been previously described in the ' Zool. Danic. Prodr.' of 0. F. Milller. Under tlic luad of Planaria fusca [Lineus ffcssercnsin) he corrects certain statements of the latter author, wholiad only seen spirit-preparations. He con- sidered the aperture of the proboscis to be the mouth, and the tube itself the intestine. He also noticed that it lived in nmiibers under stones.
Linnaeus seems to have had little or no acfpiaintance with Nemerteans, which were either tinknown or confounded with other animals, and it was only after the labours of O. F. .Miiller and others had brought them into view that they were noticed in Gmelin's edition of the ' Systema Naturae,'" published in 1788. They were grouped by Gmelin along with the Planarians under the Genus Planaria, one of tlie divisions of his Class Intestina. They thus became associated with intestinal worms, Lumbrici, Sipuncnli, and leeches. They were classified as follows: — (1) Those without eyes ; (2) those with one eye ; (;3) those with two eyes ; (4) those with three eyes ; (5) those with four eyes ; (6) those with many eyes. The animals, however, were so little under- stood that this arrangement is not to be depended on. Nothing new was introduced in Dr. Turton's translation of this edition of the ' Systema.' ^
Otho Fabricius, retm-ning to the subject in 1798 described* three Nemerteans under the names of Planaria ancjulata, P. fitarescens, and P. Candida, from Greenland. Like I'allas he considered the proboscis to be the alimentary organ, though he correctly interpreted the mouth in the Lineidce, and the anus in both.
In the following year, 1799; Jens Rathke '" alludes to six species of the group, viz., Planaria hadia, P. lalcrilia, P. mnfjuinca, P. carnea, P. alropnrpurea, and P. linearis. The fii'st two I have not satisfactorily made out, the third probably refers to Lineus san(/uineits, the fourth to a variety of L. (/esserensis, the fifth may be L. jnarinus, while the sixth is Cephalotlmx linearis. Three of the species are figured.
Lamarck, in his ' Systeme des Animaux sans Vertcbres "^ mentions onl}' one Nemcrtean, viz., the Planaria rosea of 0. F. .MiiUer.
L. A. G. Bose ' classified the Nemerteans with the Planarians luuler the true worms with elongated articulated bodies, but without external organs, placing them with the Gordii and leeches. In regard to species he follows 0. F. JM idler.
Montagu was the next British naturalist after Borlase who paid attention to tlie Nemer- teans.' In 1804 he gave a good superficial description of the worm mentioned by the former, under the name of Gordius rnarinus, with remarks on its habits. He was, moreover, the
' Otho r.Miiucius, 'Fauna Grocnlandica.' Ilafiiitc et Lipsiac, 1780.
- CImelin's, 'Liunseus Syst. Nat.,' torn, i, pars, vi, p. .308". Lcipsia;, 1788. Editio decirae tertia, aucta, rcformata. ■' London, 1802.
' 'Skrivter af Naturhistoire Selskabet,' 4de bind, 2dct hefte, p. 52 et seq. Kiobenliavn, 1798.
'' " Jattagelser liculiorende til Jndvoldcormcnos og lilddyreucs Naturhistoire." ' Skrivt. af Natur- hist.,' Sclsk. V, 1 heft., pp. 83, 8|.. Kiobenliavn, 1791).
« Paris, 1801. ' ' Hist. nat. des Vers.' Paris, 1802.
" ' Description of several Marine Animals found on tlic South Coast of Devonshire.' Trans. Linn. Soc., vol. vii, pp. 72 and 73.
12 HISTORY OF THE SUBJECT.
first to describe Carinella annitlala. JIc followed previous authors in classing these and allied forms under the ' Intcstina.' The same species, termed respectively the Liiie-worin and the Hair- worm, appeared, from Montaj;u's descriptions, in Dr. Turton's ' British Fauna.' They were arranged in a similar manner under Class V, Vermen, and Order I, Intenlina, but were placed under different genera, the former being alone, and the latter associated with Gordius aqttaticus and G. aryillaceus.
It is from the interesting manuscript, however, which the relatives of Col. Montagu have placed in the Library of the Linnean h^ocicty, that we gather how much and how closely the esteemed observer examined the Nemerteans. In this work he describes more than a dozen species, not a few of them for the first time, and the majority so truly, that it is with a sense of relief and satisfaction that one rises from its perusal. Little can be added to his account of the external appearance and habits of the animals ; and, though he did not enter into their anatomy, he correctly interpreted the mouth and anus in the Anophi, and was too cautious an observer to locate the former organ in the same position in the Enopla. He explains that, though he termed the species above mentioned Gorilli, this was only a provisional name until further discoveries of species shoulil put him in a position to frame correct generic characters. To the description of the genus Llncus he appends the following remarks on the Nemerteans : — " Their use and general economy arc little known, but we may conclude they contribute partly to the food of some fishes, and in their turn keep within bounds some smaller beings, and thus serve to support an equili- brium in the great scale of nature." A volume of carefully coloured figures, by the skilful hand of Miss E. Dorvilie, accompanies the manuscript.
0. r. M idler in his great work" described several new species, and gave figures of others mentioned in his previous works, grouping them still under the genus Vhinariu. Two of his forms, viz., Plaiiariu viridi-s and P. rubra were communicated by the author of the 'Fauna Grrenlandica ;' the others were P.filaris, P. rosea, P.Jlaccidti, P.gesscrenm, and in the fourth volume P. C. Abildgaard contributed another — Plannria dorsalis. The author observed the proboscis, the cephalic fissures, and the ventral slit in the Anopla, and likewise gave the correct position of the anus. This work then noticed seven species, most of them in a recognisable condition as regards description and figures, the latter especially deserving praise for their faith- ful delineation.
In 1806 J. Sowerbys gave the title Linens lonffissimus to the Black Line-worm, which now bears the name of Liiieus marhii/s. He first heard of it from Col. Montagu, and afterwards from Mr. Simmons, who sent specimens from Edinburgh. In his description he correctly located the mouth, and observed the longitudinal streaks on the body, as well as the tendency of the broken posterior end to decay, while the anterior remained alive. He mentions that the fishermen pull them in as they would a rope, but never find the posterior extremity, and that they esti- mate their length at twelve fathoms. A coloured engraving of the animal accompanies the description.
In 1811 Professor Jameson* included Linens lonijissimus in his ' Fauna of the Frith of Forth,'
mentioning that the worm was not inicommon on oyster-beds.
^ ' British Fauna, coutainiug a Compendium of the Zoology of the British Islands, arranged according to the Linnean System.' Vol. i. Swansea, 180".
- O. F. MuLLER, 'Zooiogica Dauica.' Havnite, 1/88—1806. ■" 'The British Miscellany.' London, 1806, p. 15, plate 8. * ' AYernerian Memoirs.' Vol. i, p. 557. Edinburgh, 1811.
HISTORY OF TFIK SUBJECT. 13
Avery sliglit notice of the Nemerteans occurs in Pennant's ' British Zoology' (edit. 1S12), two only being mentioned, and those previously described by Montagu.
Some remarks on the habits of LlnouHmnriniis were made l)y Ihc Rev. Hugh Uavies in ISlo. He observed that tlie animal was sensitive to light, though he couhl not discover eyes. He also considered that the spiral form was purposely assumed by the worm during progression, for he could not perceive how its amazing length could otherwise be transported. He thought it by no means improbable that it reached the length of twelve or even fifteen fathoms.' An almost verbatim report of this paper appeared nc.\t year (1S16) in the 'London Medical and Physical Journal,' p. 207.
In the same year Olcen,- in his " Lehrbuch," brings in this well-known species {Linens marinus) after Nais and Lumbricus, under the name of Borlasia co/t/lirE. He correctly describes the mouth, and gives a short resume of what was known with regard to the Devonshire specimens, and a small outline of the species.
Lamarck, in his ' Histoire Naturelle des Animaux sans Vertebres,' 1S16, like other writers about this time, copies the arrangement of 0. V. Midler. He did not think that the I'lanarise were annelids, but that they approached the leeches.^
Cuvier, imaware of the names previously given to these animals by Sowerby and Oken, for the first time applied the term Nemertes* in 1817 to designate the species described by Borlase. He groups the animal in the second class (of his Zoophytes) "Les Intestinaux" {Enfozoa, Rudolphi), and in the first order of this class, " Les intesfi/ia/'.r cavUnires," along with very heterogeneous companions, such as Lerna-a and others. He thus separated them from the I'lanarians, which he placed under the head of the " Intestinaux par enchi/mateux." The sole species known to him was the Nemertes Borlasii, Cuvier, which, he says, insinuates its anterior extremity (by which he in the first instance means the tail, since he mistook the anterior for the posterior end) into Anomiae, for the purpose of sucking the contents, a feat, it appears to me, of somewhat dubious veracity. In his second edition he left the Prostomac amongst the Planarians, following, according to M. dc Quatrefages, Duges in this respect. In Griffith's edition " of the ' Regne Animal' of this author little further information is given. Of Nemertes it is said by way of description, " It is a worm extremely soft and elongated, smooth, slender, flattened, ajid terminated at one extremity by a large blunt point, pierced Ijy a hole ; widened, and broadly opened at the opposite extremity, by which it fixes itself. Its intestine traverses the whole length of the body. Another canal, l)robably connected with generation, winds along its parietes, and finishes at a tubercle on the margin of the wide aperture. 'SVSl. Dorbigny and de Blainville, who have seen this animal living, assure us that the wide aperture is the mouth." Besides repeating the remark aI)out the sucking of the Anoraia by Nemertes Borlasii, it is further explained that the animal remains sunk in the sand, and is " more than four feet long," neither of which observations adds in any way to our knowledge. The only point of interest in this description is the cautious correction of the mistake which Cuvier made in holding the anterior as the posterior end of the worm. In the iilus-
' 'Some Observations on tlic Sea Loug-Worm of Borlase, Gordins marinu.i of ilonta.' Trans. Linn. Soc., vol. xi, p. 292.
- 'Lehrbuch dor Naturgeschichte, Dritter Tlicil, Zoologie.' Erstcr Abthcil. Sec. Jena, 1815, p. 3C5, tab. xi, fig. 1.
^ 'Hist. nat. des anim. sans vert.' Paris, 1810, &c.
' Cuvier, ' Regne Animal.' Tome iv. Paris, ISl".
5 Vol. xii, p. 4G8. London, I83i.
14 HISTORY OF THE .SUBJECT.
trated edition of the ' Regne Animal/' by the disciples of the great master, .M. de Quatrefages gives exactly the same description, and repeats certain of the fignrcs — to be alluded to iiereafter.
Schweigger, in his ' Handbucli der Naturgcscliielite,' follow^ Cuvier too closely, for he now describes Borlnsia ani/lia as having a membranous disc posteriorly, and either occurring in a free state, or by aid of this disc adhering to Anoraiaj."
Dr. Fleming,' in 1822, represents the Nemerteans by Linens, one of tlie genera of his family Gordiiisida-, the other genus being Gordius. He correctly observes that in Lineup the mouth is a longitudinal slit placed under the snout, but makes no further remark than that several species inhabit this country.
A very considerable increase to the knowledge of these animals was made by the investi- gations of the celi'bratcd Italian naturalist Stefano Delle C'hiajc, who, in the second volume of his ' iMemoric,' ' published in 1825, gave somewhat detailed descriptions of two Nemerteans, for which he constituted the genus Folia, named after the comparative anatomist Giuseppe S. Poli. In his sketch of tiio anatomy of Folia siphunculus, he mentions two muscular coats unScr the skin, an inner of longitudinal fibres, and an outer of transverse (circular). From the mouth springs a muscular rugose gullet (speiseriihre of the Germans), having an inner nuicous coat and a fibrous layer. The alimentary canal has the same diameter, and extends throughout till' entire length of the animal. In each articulation we have a right and a left sac or pouch in connection with the alimentary tube, into which the food may enter. Above the digestive tract is fo\md a canal containing a long proboscis, which has four fibrous coats, and an internal nuicous one covered with papilliE. The proboscis, moreover, is fixed to the wall of its sac by a muscular band. lie imagines this to be an organ of touch, and states that when free its motions are so vermiform that one might easily mistake it for a Lumbricus or Ecliiiiorh/nchiis. In regard to the circulation, he observes that two arteries arise from the triangular lobe of the head, and proceed along the sides of the body, while two sacs, which have the function of hearts, occur at their commencement. In the angle of the basis are three slight whitish elevations, in connection with a whitish thread, which nms down to the middle of each artery. From the cud of the mouth springs a very small vein, which gives branches to the lateral sacs (of the digestive cavity). In his other species {Folia lineafa) he describes a prehensile disc around the anus, and the occurrence of pores on the ventral sm-face, analogous to the respiratory sacs of Sipuncidus, but the position of the form is doubtful. This author therefore has the merit of being the first to anatomise these animals in a scientific manner, and to interpret fairly the physiology of the parts. He recognised the true mouth of his examples (which belonged to the Anopla), the general arrangement of the digestive tract, and the presence of distinct muscular layers in the body-wall. The errors he fell into with regard to the circulatory system may be easily explained, since he worked only with dead animals, or, at least, not with those capable of being employed as transparent living objects. The anal "sucker" in F. lincatu may have been due to someeversion of the digestive canal, if the species pertained to this order.
1 ' Regne Animal Illust.' Zoophytes, texte et atlas, p. 65, plates 33 and 34. Paris.
- ' Handbucli der Naturgeschichte der skelettlosen umgegliederten Thiere.' "\'on Dr. August Fricdricli Schweigger. Leipzig, 1820, p. .")91.
5 ' Philosopliy of Zoology,' vol. ii, p. 605.
' S. Delle Chiaje, ' Memorie siiUa storia e notomia degli animali senza vertebre del Eegno di Xapoli.' Napoli, 1823—1820. 4 vols. (Vol. ii, p. 406.)
HISTORY OF TIIH SUBJECT. 15
In his third volume, puhlislicd in 1S:}8, he describes several other Ncmerteans. Amongst these in all probability falls also his Planaria siphunculiix. J have not been able to identify his Polia punctata; the size and colour of the proboscis, and the thin edges of the body in his figure,' would lead nic to place it near Micrura fusca. His Polia oculata is allied to Lincm sanguineus, but the occurrence of eiglit large eyes on each side, and the somewhat wide and flat- tened nature of the snout in his enlarged figure,^ make it doubtful. The identification of Polia cwrulcscens is also difficult"; but his Polia yeniculata is the Cerehraiulus (/eniculatus of M. do Quatrefages.
In 1829 the same author figures three species in his fourth volume, viz., Ophi/ocrpluilns murcnoidcs,^ Tuhuhnms poli/morplius,'^ and Cerehraiulus hiliiiealus^' but I cannot find reference thereto in his text farther than the simple explanation of the plate. 0. murenoides may be a variety of Lincus marinus, or else a species with which I am unacquainted. Tuhulanus poli/morphus has a broad hastate head with lateral fissures. There are no stripes on the brownish groiuid-colour. In his descripti(m of the figure (9) of C. hilineaius he terms the everted pro- boscis " sifone genitale." In a section of the proboscis of this species, he shows at least external circular and median longitudinal fibres, although in some other respects he is obscure, since he speaks of an accessory cavity — prdbablyfrom the invagination of the proboscis. A representation' and accompanying explanation are also given of the ovaries of Poli(t siphunculus, m which the author shows a general accjuaintance with their position.
An abstract of Dellc Cliiaje's observations was given in 1832 in Oken's ' Isis.'^
P. S. Leuckart^ in 1828 established the genus Meckelia for the reception of a species {Meckelia somatofomus) which he found in a runlet connected with the ]\Iediterrancan. This species was evidently a true example of the Anopla, from the description given of its cephalic fissures and mouth, and therefore it is wrong to apply the generic title to a family so diverse as that containing the Gordius annulatus of Montagu.
In the same year Dr. George Johnston commenced a series of papers" on this department of British Zoology, and he proved a most able and persevering expounder of the habits and general structure of the group, rescuing them from the almost total obscurity in which they were shrouded in this country, and giving a fresh impetus to their investigation. Errors, doubtless, he made, but they were not more striking than those of many of his contemporaries, and not a few of his successors. He described on this occasion three species, viz. Planaria Jlaccida, P. tinicolor, and P. ladiflorca. The first refers to Nemertes Neesii. The second may be Linens sanguineus, though he himself does not seem to have been quite sure as to what it was, since no notice is taken of it in his subsequent writings. The last is Amphiporuslactijloreus. The first came from deep water, the last from the littoral region.
M. Ant. Duges established the genus Prostoma, also in 1S2S, to designate what appears to
1 Op. c-it., vol. iii, p. 172, tav. 13, f. 1 1. - Op. cit., tav. 11, fig. 1.
^ Op. fit., vol. iv, tav. 62, figs. G, 7, and 13 — 15. ,
» Op. cit., tav. 62, figs. 8 and 12.
* Op. cit., tav. 62, figs. 9 and 16.
* Op. cit., vol. iv, p. 37, and tav. 5.3, fig. 7.
" Isis, 1832, heft. 6, p. 617, taf. 10, figs. 3—5, and IP— 11\
* 'Breves animalium quorundam maxima ex parte maiinorum descriptiones, F. S. Lcuckart.' Heidelbergte, 1828.
» ' Zoological Journal,' vol. iii, pp. 428 and l^O.
16 HISTORY OF THE SUBJECT.
be u freshwater Ncmciteaii {Prostomn clopHinoides), which lie discovered in French streams.' He found that it dili'ered entirely in type from the Planarians which he had lieen describing, since it did not possess their gastric ramifications, but had a simple alimentary tube (proboscis), forming several convolutions. The latter organ commenced in front by a probably exsertilc mouth, and terminated posteriorly in a rounded anus.
In the same year (1S28) M. de Blainvillc' placed the Nemertcans along with the I'lanarians under the Class Knlomozouirvs apoilei ou Vers, in the Sub-class ^Parcnlomozoaircn ou Siib-Jliintli- daircs, and in his fii-st Order Aporocephala. He established his first Family, Tcretularia, for their classification, but associated with them Boncllia, a Gepliyrean. His genera of true Nemertcans were TiihuJanuH (Renicr), Oph'wcepludiis (Quoy and Gaimard), Cerehralidus (Renier), Borlnisi'i (Oken), LohUdhrum (De Blainville), and Proshmn (Dugcs). lie correctly described the mouth in the Anopla (to which group almost all his species, with the exception of Prostoina, belonged), and the general characters of the animals. His figures of Borlaaia anglia in the Atlas are fair.
Dr. G. Johnston ■ continued his observations on Planaria in 1S20, describing Plnnarla octocidala, P. qiiadrioculald, P. bioculala, ami P. fili/onnis. The first mentioned refere to Linens sa»//uineiis, the second to Tctrasteiiima Candida, the third to L. ffcssercnm, and the fourth to Cephalothrix linearis. His accounts are short, but easily recognised.
In 1830 M. Duges jjublished descriptions' of four species of Prosloina, and gave certain anatomical details. One of these, however (now called P. chpsinoideum), was mentioned in the previous paper ; the second, P. lumbricoideuw, is probably Tetrasleiiima Candida ; the third, P. candidum, MiiUcr, appears to be the same species ; and the fourth, P. armatum, has so many eye-specks that, if the description is correct, it is a species with which I am unacquainted. His anatomical investigations were made on the latter. He confounded the proboscis with the diges- tive system, ami the nervous with the circulatory system.
Professor Iluschke^ in a notice of the anatomy of Noto»permu8 drepanensig (Cerebralulus (/enicuhdm, Dc Quatref.), from tufts of CoraUina officinalis on t\\c shores of Sicily, published at this time, mentions that there arc two muscular coats under the skin, an external longitu- dinal and an inner circular; the inner longitudinal muscular coat having escaped observation. He truly interpreted the alimentary canal, with its post-ganglionic mouth and terminal anus, but mistook the proboscis for a male organ, which, however, he correctly located in a sheath between the muscles of the body-wall and the digestive tract. The lateral fissures of the head he likewise connected with the generative organs, and described and figured the nerves as semen-canals. This appears to be an example of the Anopla, and hence we are enabled to predicate as to its probal)le structure.
In the same vear (1830) Professor Leuckart,* in a further note on bis Meckelia somaiotomus, calls the aperture of the proboscis the genital organ, but he cori-ectly names the mouth. He states that the genus Mcckelia closely resembles Borlasia.
In the following year (1831) our knowledge of the group received a considerable accession
' ' Ann. des so. nat.,' Ire Ser., vol. 15, p. 140, pi. 5, figs. 25 and 26, ■ ' Diet, des So. nat.,' vol. 57, pp. 573—577. 18.28. ^ ' Zoological Journal,' vol. iv, 1829, pp. 56 and 57. * 'Ann. des sc. nat.,' Ire Ser., vol. 21, p. 73, pi. 2, fig. 1—6.
" ' Besclireibung und Anatomic eines neuen an Sicilien gefundenen Meerwurms.' Isis, 1830, heft. C, pp. G81— 3, taf. 7, figs. 1—6. 6 Isis, 1830, heft. 6, p. 575.
iriSTORV 01'' THE SUBJECT. 17
from tlic laljDiirs of the illustrious Ehrcuberg,' wlio formed tliciii willi others into a distinct class, which ho termed Puytozoa Turbellaria. It is true he included \mder this head animals, such as the Gordii and Naidiiia, which are widely dissociated from the typical group, and, in his arrangement, placed apart genera allied in tlu; closest maimer, yet his contrilmtion forms an ejxich in the literature of the Nemerteans. He characterised the Turbellaria briefly as " Evcr- tebrate apodous animals, creeping; often with retractile vibratile hairs; with a distinct intes- tinal tube ; separate vessels without hearts, rarely with a mobik^ dorsal and abdominal vessel ; hermaphrodite or with distinct sexes, oviparous and spontaneously fissile ; excreting a copious mucus." The Nemerteans were placed entirely under his second order, Rhabdocoela, that is, Turbellaria with a simple cylindrical or conical intestine, having the mouth at one end and the anus at the other. The family Micrurca he grouped under the second section [Monostcrea] along with the Gordii, but he more consistently classed all the other Nemerteans described by him under the third section, Amphiporina. Ilis arrangement is thus, as follows : —
Section II. — Monosterea.
Fam. ^licrurea.
Gen. Disorus, Micrura, and Polystemma.
Section III. — Gyratricina.
Gen. Orthostoma, Gyratrix, Tetrastemma, Prostoma, Heraicyclia, Ommatoplea, Am-
phiporus. Fam. Nemertina. Gen. Ncmcrtes, Notogymiuis.
The want of an anatomical basis for his classification rendered errors unavoidable, but his descriptions of the species are characterised by care and lucidity, and his figures arc good. He erroneously considered the proboscis to be the intestinal canal, and its aperture the mouth, while the actual mouth in the Anopla he termed the genital opening. In the Enopla he could not of course find the latter. He correctly noticed the presence of an anus. Since he states that he saw a reddish viscus in Tefrasteiiimn fiamdum on each side in front of the proboscis (which reddish mass he took for an ovarium), it is probable he alludes to the ganglia. The stylet- region of the proboscis entirely eluded his notice.
The arrangement of this author is implicitly followed in the twelfth edition of Lamarck's ' Ilistoire Naturcllc des Animaux sans Ycrtelu-es.' '
Dr. George Johnston described and figured' in 1833 CarincUa annulaia under the name of CarincUa trilineata. He was unaccjuainted with the previous description by Montagu in the ' Linnean Transactions.' Like many others he also called the proboscidian aperture the mouth, while the true mouth escaped his notice. lie rightly stated that the anus was terminal.
Quoy and Gairaard in the same year give an account, with figiu'cs, of several Nemerteans in their zoology of the ' Voyage dc la Corvette I' Astrolabe.' None of their species, however, seem to be
' ' Symbolffi Phjsicte. Aniiu. cvcrtcb. cxclus. inscctis.' Ser. prima. Bcrolini, 1831. 2 ' Hist. Nat. des Animaux sans Vert.' 12th edit., par Deshayes et H. M. Edwards, vol. iii, pp. GIO— 613. Paris, 1840.
' Loudon's ' Mag. Nat. Hist.,' vol. vi, p. 232.
3
18 HISTORY OF THE SUBJECT.
identical wiili tlic British forms. They correctly iiitei-preted the mouth in the Anopla, but erroneously considered the aperture of the proboscis a genital pore, representing, moreover, as a parasite (Plate m, fig. 14) the proboscis escaping from the mouth of a specimen of Borhsia IricuKpidula. A Tclirixlemiiia, with a deeply notched snout and four large eyes (" Uorlasie ii quatre points "), which they took in the sea near Aniboyna, was found inhabiting an Analifa, hut \vli( till r it occuiicd there accidentally or otherwise we are not informed. The worms are placed under the Zoopiiytes in the group "Vers Apodes."'
In Ib3'!i Dr. George .lohnston published further interesting observations on the genus Ncmertes,^ mentioning nine species as occurring on British shores. His general anatomy rc'uiaiiis us ])eforc, the proboscis being described as the alimentary organ; but he rightly observed that one section of the worms had and another had not stylets in the proboscis; and accordingly this formed the basis of his classification. He termed the true alimentary chamber the general cavity of the body, though he (jualified this description by saying that the lateral cieca were parts of the digestive system. He also observed that the ova were independent of these cajca, and were developed between tiicm and the skin, fie, however, thought the mouth in Linens san(fuincus a nerve-ganglion, and in the entire group called the ganglia "hearts." He discovered the gregariniform jjiirasites infesting Linens, though he could not make out tlicir nature. Two plates of very fair figures accompany this paper, from the pencil of his accomplished lady. If M. de Quatrefages found that his species — Polia purpurea, ' Voy. cu Sicilie,' ii, p. lii — approached very closely the Neinerlrn or Borlasia purpurea of this author, it must have belonged to the Ano])la, and have had lateral fissures.
W. S. Maclcay, in his remarks on the Annelida in Sir R. Murchison's ' Silurian System ' (1839), considered the Nemerteans as aberrant annelids, classifying them along with the Lnud)rici and leeches, under the group Jpoda, in which the body was without a distinct head or feet. The " Nemcrtina " were further characterised as aquatic, without eyes or antennae, and with indistinct articulations, which, indeed, were only visible in contraction. Special reference is made to the long vermiform impression in the Cambrian Rocks of Llampeter, which is termed Nemerfifes Ollivantii, Murchison ; but, so far as I can judge from the description and plate, this is a veiy doubtful Nemertean.'
In IS to Professor E. Gruljc' made some observations on the Nemerteans of the Adriatic, describing several species, two of which are figured, viz. Polia delineata, Delle Chiaje, and 3Ieckelia annulata, Grube. The latter, however, is the Notospermus drepanensis of Huschke ; and, while I am not acquainted with the Borlasia annulata of Ehrenberg, another Avhich he mentions, his Borlasia viridis appears to be allied to LIneus ^esseremis. Under Ehrenberg's name AwpMporus, he also refers to what, in all probability, is an example of the Enopla ; but the identity of this form, or the succeeding new eyeless type Akrostomuni Sfannii, Grube, cannot be determined. This veteran investigator of the annelids and their allies recognised the correct situation of the apertures of the proboscis, mouth, and anus. He observed that the
' ' Vovage de deoouverts de L' Astrolabe — sous le commandement de M. J. Dumont D'Urville.' Zoologie, par MM. Quoy et Gaimard, tome quatrietne. Paris, 1833.
- "Miscellanea Zoologica," 'Mag. Zool. and Bot.,' vol. i, pp. 529 — 538, pis. xvii and xviii.
^ ^lurcliison's ' Silurian System,' vol. ii, p. 699, pi. xxvii, f. 4.
^ ' Actiuieu, Echinodermeu und "Wiirmer des Adriatischen und Mittelmeers,' pp. 57 — GO, figs. 7, 7a, 8, and 8a. Kouigsberg, 1840.
HISTOKV 01' THE SUBJECT. I'.i
former had a special sheath, and tliat it was not connected with the ahmentary system, which lay beneatli it.
Dariiiii tlu! same year (ls41) tlu" vahiahlc ' Dcscrizione e Notoniia Animali Invertcbrali,' of Delle Chiaje, was published at Naples, containing further and Jn:portant observations on the Nemerteans. It lias, indeed, been aptly said by the lamented Professor Claparedc, that the productions of this autiior form zoological mines, from which succeeding investigators mayiiuarry out much that is new and rare. In this fine woi'k the author dcscriljcs the Nemerteans as AnndoHi Polici, and considers they offer certain analogies with the leeches, on account of the structure of the alimentary canal, wliik; in the form of tlieir bodies they approach the Planari;e. A good description is given of the digestive tract and its " hepatic sacs," M'ith their varying arrangement, e.g. " })innatitid-bifurcate" in Folia ddineata, and bifid in PoVta rosina ; but lie falls into the error of regarding the stylet-region of the prol)oscis in the Eiiopla as the stomach, and exhibits an imperfect and inverted figure of the region (Tal). 104, fig. 22 ; vol. v, p. 42) in the Prodoina catididum of Duges. He, however, correctly interpreted the relations of the proboscis to its sheath, the anatomy of the generative organs, and sliowed an elaborate series of branching transverse arteries between the dorsal and lateral vessels iu PoUa sifoncello. ]\Iany species are described and figured, and for the first time he notices the semi-parasitic habits of Polia tetroph- thalmala, which he found in tiie respiratory cavity of " Ascidia mammellata." Besides the new species, the descriptions and remarks concerning the old enable us to determine more clearly their nature and relationships.^
Mr. W . Thompson ' contributed at this time, under the head of " Additions to the Fauna of Ireland," an account of some species of Nemerteans, viz. Nemertes gracilis, N. lacfiflorea, Carinella trilineata, and Gordius annidaim. The two latter refer to the same species, viz. Carinella annidalu, the one being Dr. Johnston's name, the other .Montagu's prior title.
In P. Gaimard's ' \'oyages en Scaiidinavie, en Lapoiiie,' ^ licc, considerable attention is devoted to the Nemerteans ; but, as only the plates of this work could be procured in the British Museum, its examination is incomplete. However, as none but he who is conversant with the anatomy of the parts can correctly represent in a drawing so minute and complex structure as is found in the proboscis of the Enopla, we may with propriety make a few remarks on these plates. In Plate c, most of the figures, from 1 to 20, seem to pertain to Amphiporm pulcher, and tiierefore the slit which is shown behind the ganglia in fig. 9 is erroneous. The entire animal is well represented in fig. 20. Figs. 23, 24, and 28 belong to a species resembling Ncmertea gracilis. Fig. 1 of Plate d would do for Amphiporus lactijloreiis. The whole of Plate k is devoted to the Nemerteans, and in this tiie structure of tiie proboscis of the Enopla is detailed. In Plate f a curious form is delineated (figs. 1 and 3), with a spear-shaped snout, a flattened body and widened tail. It appears to be an intermediate type between the Nemerteans and Planarians, and proliably is a swimmer. The drawings were made by G. Boeck.
CErsted,* iu the fourth volume of ' Kroycr's Xaturhistorisk Tidsskhft' for 1S42-43, wrote
' 'Descrizione e iiotomia animali invertcbrali della Sicilia citeriore osservati vivi ncgli auni 1822 — 1830/ da S. Delle Chiaje. Napoli, 1811.
2 'Ann. Nat. Hist.,' vol. vii, 1841. p. 482.
^ ' Voyages do la Commissioa Scientificiuc du Nord eu Scandinavia, en Laponie, au Spitzberg et aux Faroe, sur la corvette La Kecherclie.' Paris, 1812, &c.
* Kroycr's ' Naturhistorisk Tidsskrift,' Fierde Bind. Kiobenhavn, 1842—184.3.
20 HISTORY OF THE SUBJECT.
a paper on Pliiiiaria and Neniertes, promulgating those views, which afterwards were given at length in his ' Entwiirf,' and which therefore need not be further alluded to here. The Nemer- teans especially are curtly dealt with.
11. Hatiike, in a very excellent structural chapter in 1843,' amended the errors of Dr. Johnston in regard to the mouth in Linens, and described correctly the digestive system, the position and relations of the proboscis and other points. He was inclined to think the proboscis an organ of touch.
In the same year (1843) we have the forerunner of a series of elaborate investigations by M. de Quatrcfagcs,'' who notified to the Academy that he had found separate sexes in the Nemerteans, with the development respectively of ova and spermatozoa, as in the Annelids. He promised to make known the complete results at a future period.
M. Milne Edwards,'^ in reporting on the papers of M. de Qualrefages, in 1S44, states, with regard to the Nemerteans, that the latter found that they approached the Annelids in the general distribution of their vascular system, the leeches in the structure of their buccal apparatus, and other |)oints in their organisation; yet their reproductive organs were analogous to those of many helminths. Their nervous system he compared to that of the " Lingules," and he likened tiieir digestive system (with a c;ecal termination) to that of the lower helminths and zoophytes. The majority of these homologies are placed on no reliable data.
In 1844 A. S. CErsted contributed a valuable addition to our knowledge of the Nemerteans and allied genera.' He classed the Nemerteans as the fourth sub-order {CeHtoidina) of his order Apoda, the others in their respective jjositions being (3) Tremalodina (Hirudinea and Plaiiariea), (2) Jcanthocephalina (Siphunculacea), and (1) Nematoidina (Gordiea). The sub-order Cegloidiiia was thus characterised : — " Body linear, rounded rather than flattened, much longer than broad, indistinctly marked by soft annulations, covered with vibratile cilia; distinct muscles, but no true nerves (?). Eyes 2, 4, G, 8, 10, many or none. Respiratory organs absent or in the form of lateral iissures on the head, which conduct the water to the proximity of the hearts. Complete circulation with two hearts. Digestive tube simple, with the aperture of the mouth situated ventrally (rarely terminal), and a terminal anus. Sexes separate ; in each a stimulating copulating organ. Testicles and ovaries similar in structure except as regards contents (ova or spermatozoa), numerous, and placed laterally in each segment." The author thus confounded the ganglia with hearts, and hence was led to believe that the cephalic fissures were connected with respiration, in so far as they permitted a closer relation between the sea-water and the contents of the supposed hearts. He had a fair notion of the digestive system, but he misinteqireted the physiology of the proboscis. He arranged the sub-order into two families and eight genera, thus : —
' ' Beitriige zur Fauna Norwegeus,' &c., pp. 231 — 237. - ' Comptes llendus,' torn, xvii, Dec, 1813, p. 124. '^ ' Ann. des sc. nat.,' Seme ser., torn, i, pp. 20-21.
■* ' Eutwurf einer systematischeu und speciellen Beschreibung der Plattwiirmer,' &c. Copenhagen, 1811.
HISTORY OF THE SUBJECT. 21
I. Fam. Nemiciu'INa.
Mouth inferior ; anus terminal.
(1) Body filiform, cciually attenuated at either extremity (head indistinct) ; no respiratory fissures.
a. Mouth and ovaria or testicles consideral)ly removed froin tiie snout.
Genus 1. Cophahihrix. h. Moutli and ovaria or testicles not mucli rrinovcd from the snout. Genus 2. Astemma.
[■2) Body linear, rounded, more or less dilated anteriorly (head distinct), respiratory fissures distinct or none.
a. Head distinguished from tlic body, no respiratory fissures.
Genus 3. Borlasia. h. Head not distinguished by a constriction from the rest of the body, respiratory fissures more or less distinct.
a. Eyes in grou[)s. Genus 4. Polysiemma. p. Eyes S — 1(3, biserial. Genus 5. Nemerfes. y. Eyes 4. Genus 6. Tetrasicnviia.
(3) Body linear-oblong, flattened, equally obtuse at either extremity, respiratory fissures distinct. Genus 7. Cerehratulus.
II. Fam. Ampuiporina.
Aperture of the alimentary tulje terminal. Genus 8. Amp/iiporus.
The foregoing classification, being founded on external appearances, could not be expected to stand, the more ^o as the writer's knowledge of the anatomy of the groups was imperfect.
In this author's ' Inaugural Dissertation'' (for M.A.), published about the same time, mention is made of the Nemcrtcans and other marine animals occurring in the Sound — in the various zones, viz. those of the Trochi, Gymnobranchs and Buccini (corresponding with the Littoral, Laminarian and Coralline of Forbes). Little or no additional information on the subject is obtained in this work, mainly on account of the difficulty in recognising his species. He does not note the presence of any in the Laminarian zone.
Mr. H. Goodsir, in 1845, made some remarks on certain of the Anopla, viz. Serpentaria fragilis and "Nemertes gracilis," but his observations are characterised by serious structural defects, apparently from too limited observations.- He termed the nerve-ganglia and cords the testicles, and this upon the faith of his microscopic researches. He considered the alimentary canal, again, a space common to the respiratory, digestive, and generative systems; his digestive tract being the proboscis. He thought that in Serpentaria each of the " annuli," or fragments, contained all the elements of the perfect or original animal, \ iz. a male and female generative aj)paratus, the
' ' De regionibus marinis.' Havnise, 1844.
- " Dcscriptious of some Gigantic Forms of Invertebrate Animals from the Coast of Scotland," ' Ann. Nat. Hist./ vol. .xv, p. 337, pi. 20, f. 1—3. I8t5.
22 HISTORY OF THE SUBJECT.
cavity common to the generative, digestive, and respiratory functions, and a small dorsal vessel analogous to the intestinal canal of Nemertes.
A very interesting brochure on the Nenicrtcans' was contrihuted by Prof. Kulliker in 1S45, a paper, I may remark, which has received too little attention from some continental writers. After indicating the ordinary characters of the groiij), the author gives a general account of their anatomy, correctly describing the mouth, alimentary canal and anus, the situations of the ganglia and tlic branches of tiie lateral nerves. He also notes the occurrence of lenses in the eyes of certain species. He is in error, however, when he states that he found two hearts with coloured blood in the head of Nemcrks roscus , and that the proboscis is attached to the wall of the body posteriorly. He observed the stylet -apparatus in several species. His classification of the Neinerteans was founded, somewhat curiou.«ly, upon the presence or absence of a sheath to the ])rol)oscis, thus : — (1) With the proboscis floating freely in the body-cavity; body ciliated, and smoothly rounded. (2) With a smooth body, and the proboscis confined in a sheath. The latter group he again subdivided into (a) those with a flattened head and lateral furrows, and {h) those having neither a flattened head nor lateral furrows. He describes ten species, most of which are stated to be new. One of these is the strange Nemertes carcinophila, which he found in an apparently [)arasitic condition amongst the ova of the common shore-crab.
Dr. .Fohnston, in his 'Index to the British Annelides ' ° (1846), described a few additional Nemerteans ; but this paper does not require further mention at present, except to observe that he arranged his species under five genera, viz., Borlasia, Linens, Serjjentaria, Meckelia, and Prustojiia, which were comprehended by the Sub-family Linina of the Family Planar'uuht . 'IViljc Nemertinea and Order Apoda.
In tlie same year (184C) M. de Quatrefages published his obsenations on the Nemerteans,* but as a more complete edition of his acute and comprehensive labours (especially as regards figures) subsequently appeared, I shall in the meantime reserve further criticism. A notice of this paper, with an appendix of his classification, was given in Froriep's ' Neue Xotizen.'* Before the appearance of the foregoing, he had also made some remarks on the proboscidian fluid and circulation of the Nemerteans in his " Note sur le sang des AnncUdes " in the previous volume (V) of the ' Annalcs.'
This author observes' that he had found in the rocks of Solenhofen certain imprints which he considered difficult to attribute to other than Nemerteans. The impressions indicate cylindrical coiled animals, resembling these worms after immersion in alcohol. In the chips of stone from Strasbourg he thought the forms referable to the Genus Borlasia, and especially resembling Linetts marinus.
In 1847 the celebrated J. Miiller" described and figured Pylidium gyrans, as a larva from Heligoland ; but he did not then find out its connection with the Nemerteans, and indeed was in doubt as to its actual relations.
' ' ^'erhaudlungen der Schweizerisclien Naturforsclienden gesellschaft bei ihrer Versammlung zu Chur, 1844,' pp. 89—93. Cbur, 1845.
- ' Anu. Nat. Hist.,' vol. xvi (Supplement), pp. 433 — 462, pi. xv.
' " Etudes sur les types inferieurs de I'embranchement des anneles. Memoire sur la FamiUe des Nemertiens" (Nemertea). ' .\un. des sc. nat.,' 3eme ser., Zool., torn, vi, pp. 173 — 303, pis. viii — siv.
* Froriep's 'Neue Notizeu,' bd. xxxix, 1846, p. 276. From the ' lustitut,' No. 660, 26 Aug., 1846.
5 " Soc. Philom. Extr. Proces verb. 1846." ' L'lustitut,' xiv, 1846, No. 664, p. 154.
6 ' Arcliiv fur Auat.,' 1847, p. 159, taf. vii, f. 1—4.
IIISTOin' OF THE SUBJECT. 23
Dr. Joseph Leidy ' in tlic saiia' year (1847) imhlishid iioto on wlial appears to be a small freshwater Nemertean {Prostoma maryinatum), l)Ut his leiiiarks are so indefinite that they arc of comparatively little value.
I'rey and Lcuekart next made some excellent observations, in their ' lieitrilge ' (1847), on the structure of the Nemerteans.^ They described the ciliated coating, and pointed out that in these animals the spike-cells (Nesselorgane) present in (he I'lanariae were wanting. They mentioned two museular coats — an outer longitudinal and an inner circular coat, and that the nerve-trunks lay on the inner side of the latter. The diti'ei'ences in regard to the ganglia of Tetrastemma and Horlasia w^ere shown, the authors demonstrating the shape of the organs in the former by a drawing from Tetrastemma variabilis, of which, however, no additional mention is made. The cephalic sacs in Borlasia {Linens) were thought to be appendages of the ganglia. They did not enter into the structure of the proboscis further than to mention that it has longitudinal and circular museular fibres ; but they correctly observed that its muscular ribbons were attached to the wall of its sheath, within which sheath a fluid with corpuscles existed. They did not know whether the generative products escaped through the body-wall, or by rupture at the posterior end, as in Arenicola ; and at any rate rupture of the body-wall might ensue for this purpose, for it was not very likely that these products escaped into the body-cavity. Lastly, they compared the Nemerteans with the Flukes and Trematoda. On the whole they correctly appreciated most of the structures detailed by them.
The only book of Renier's which I have been able to examine is the posthumous volume on the zoology of the Adriatic, edited by Professor G. Mencghini (1847).'' In this work the mouth of the Anopla is thought to be the genital opening, and the aperture for the j)ruboscis the mouth. Little attention is paid to the proboscis, and the anatomy of the group in general is much less precise than that of Delle Chiaje. The drawings, also, which accompany the text, are indifferent. Six species are described, only one of which, however, appears to be British, viz., Siphonenteron elegans (Kenier), which Meneghini avers is identical with the Valencinia oriiala of De Quatrefages, and therefore with the common Carinella annulata of Montagu.
E. Blanchard in 1847 gives a brief but important notice of the structural position of the Nermeriina, Ehrenberg.'' After having shown the principal differences between the Anevormes {Bdellomorp/ia, Bendrocala, and Tremaioda), the Cestoidea and the Helminths, he contrasts the whole with the Nemerteans. (1) \\\ regard to the Nervous system. He considers the cephalic ganglia of the Nemerteans analogous to the sub-intestinal ganglia of the other annelids ; and states that their disposition quite differs from that of the Anevormes in general, and the Planarians in particular. They have no closer analogy with the Nematoidea in this respect. (2) The Circulalory system, he observes, 2)resenls nothing in conunon. (3) Digestive system. He follows i\I. de Quatrefages in describing the digestive canal (proboscis) as simple in the Nemerteans, whereas in the Planarians it is branched. (4) Ge?ierative system. He agrees with the former author also in regard to his designating the Planariae and Trematoda Turhellaria monoiques,
' ' Proceed. Acad. Nat. Sc. Philadelph.,' vol. iii, 1847, pp. 251-3.
- " Zur Kcnntniss vom Bau dor Ncmertincn," ' Beitriige zur Kenntniss Wirb. Thicrc,' &c., pp. 71 — 8 and 150, taf. i, f. 14—10. Braunschweig, 1847.
^ ' Osservazione postume di Zoologica Adriatica del Professore Stefano Andrea Renier,' edited by Prof. G. Meneghini. Venezia, 1847.
* 'Ann. des so. nat./ Seine ser., Zool.j torn, viii, pp. 123 — 127, pi. ix, f. 5.
24 HISTORY OF THE SUBJECT.
vvliilu the Nemertcans arc Turhellaria dio'iqueit. As regards the separation of the sexes, the Neraerteans ajjjjroach the Nematoda, but the configuration of their organs is entirely dissimilar. He hints at otlicr difl'ercnccs in connection witli the teguments and form of the body, but adds that in a rigorous examination these are of secondary importance. He concludes witii the following remarks: — "Thus having shown how the N'emerteuns differ from the I'lanarians in their entire organization, having exhibited these difTcrences to be profound and characteristic, having demonstrated how fin- they diverge from the Ncraatoda in essential structure, we arrive at the necessary conclusion that the Nemertcans constitute a group (juite unlike those with which we have been contrasting them, and that their attinities do not hnk them more closely to the Nematoda and Anevormes in general than to the Planarians in particular." The author thus rather exaggerated the gulf between the latter and the Nemertcans, being misled by the erroneous observations of M. de Qiiatrcfages on the digestive system.
In the same paper M. IJlanchard goes on to describe CerebraluUts lit/uricua, one of the Anopla, chiefly with respect to its circulation. He mentions that on account of the delicacy of Nemertean tissues he had to add a small proportion of a salt of mercury to the sea-water, so a.s to enable him to inject the vessels. He states that the dorsal vessel shows no ramifications, but passes forwards to the cephalic region to unite with the two lateral vessels by the communications aroiuid the p^)i)oscis and nerve-centres, the latter being bathed by the circulating fluid. He contrasts this arrangement with the ob.servations of M. de Quatrefages, but he was not aware that essential differences exist in this respect between the Anopla and Enopla. He saw trans- verse ramifications between the lateral vessels, and appears to have noticed the network in the (Esophageal region, though he speaks of an internal lateral vessel, of whose presence we are unacquainted. He thought that transverse ramifications of the longitudinal vessels existed in all the Nemertcans, for he also observed them in Polia (fcniculata, Delle Chiaje, and in a Vcdencinia of undetermined species ; and agreed with M. de Quatrefages as to the presence of proper walls to the vessels. The Nemertcans, therefore, have a vascular network comparable with that in the Anevormes, presenting nevertheless differences in anatomical disposition. The circulatory apparatus in these worms is perhaps more complete than that of the Aporocephales (Planarians) or the Trematoda ; for the dorsal vessel seems to carry the blood forwards, and the lateral backwards, though the oscillations arc irregular. He would place the Nemerteans, consequently, in a division adjoining the Anevormes, both on this account and the higher development of their nervous system.
Von Siebold,* in 184S, took the bold step of severing the Nemerteans from the Planarians by the intervention of the Rotatoria ; and though we would not approve of such disjunction, the soundness of his decision in separating them from the Helminths can scarcely be questioned. He arranged them as the first Order of the Ringed worms : —
Order I. Apodes. — Body without bristles. Sub-order 1. Nemertini. — Body posteriorly without an anus (Ausangeorgane) ; head often with lateral respiratory fissures.
His information is derived from Rathke and other observers.
This author subsequently gave abstracts of various papers ou the Nemerteans in the ' Archiv fiir Naturgeschichte.' "
1 ' Lehrbuch der Yergleichcuden Anatomie,' von Y. Siebold u. Stannius. Berlin, 1848. -' ' Archiv fur Naturgeschichte/ 1850, p. 382, &c.
inSTOIJV OF TITK SIJBJECJT.
zij
In a subsequent paper in tlio 'Annalcs' for 1S49,' M. Blancliard adopts the general anatomy of the Nemcrteans given by M. de Quatrefages, and agrees with the latter in thinking that till' affinities of the group lie rather Mith tlio Ilcliniiitlis than the Planarians, on account of the erroneous view with regard to the c;ccal nature of the digestive traet. Moreover, in all the known Aporocephales (Planarians) tiic sexes arc united in one individual, whereas in the Nemerteans they arc separate. The latter likewise have a veritable oesophageal collar, which is wanting in the former. H<! ju'oposcs the name Aplocala as distinctive of the characters of the group (the simplicity of their intestine), and thinks that the title Nemerteans should be applied only to a tribe or family. No fresh observations arc produced in this paper, and the errors in regard to the digestive system arc rendered more conspicuous.
]\[. de Quatrefages at this time published his valuable and extensive observations, begun at the Iks ChuMsey in 1841, and carried on subsequently at St. ]\Ialo, St. Vaast-la-Hougue, Brehat, Sicily, &c., on the anatomy and zoology of the order, with additional coloured plates, in the second volume of the ' Voyage en Sicilic,' the joint work of IMilne Edwards, Blanchard, and himself.- The author, after giving an account of the history of the group, proceeds to treat of their characteristics and classification thus : —
Nemcrtiaiw. — Nervous system distinct, composed of two lateral lobes united above by a slender commissure, beneath by a broad sub-cesophageal commissure, and giving origin to two isolated longitudinal nervous trunks. Circulatory system shut; circulation complete. Alimentary tube simple ; proboscis exsertile ; intestine CKcal. Sexes separate ; reproductive organs placed at the sides of the al)donunal cavity, and occurring throughout the entire length of the body. Surface quite smooth, covered with vibratile cilia as follows :
lie distinguishes his six genera
Nerve-trunks entirely lateral in position
NEMERTL\NS
!Mouth terminal
Body very long
^ Body short
Mouth subterminal, inferior Valencinia.
Very flat .... Borlasia.
More or less rounded Nemertes.
] Very proteiform . . Folia.
y_ Form less variable . Cerebratulm.
^ Nerve-trunks sublateral CErstedia.
This arrangement, from the inaccuracy and limited extent of his observations in regard to the position of the nerve-trunks in the various groups, is useless ; and the subordination into genera rests upon an equally unreliable basis. Not a few in his list of thirty-two species are forms previously known, though described as new worms — several more than once ; and it is to be remarked that some of the very common specimens, e.y. Linens (^esseren>ii>> and L. sanguineus, are not mentioned, or else are so described as to be unrecognisable.
He characterises the animals as chiefly nocturnal in their habits, with the exception of Polia
' " Rccherches sur I'Drgauisatiou dcs Vers/' 'Aun. ties sc. nat.,' 3me ser., Zool., torn. .\ii, pp. 28—35.
2 ' Recherches Auatomiqucs ct Zoologiqucs faitcs pendant un Voyage sur Ics cotes dc la Sicilie ct sur Ics divers points du littoral de la France,' par MM. II. Milne Edwards, A. de Quatrefages, et Euiile Blanchard ; deuxieme partic, pp. 85—220 ; pis. is — ssiv, par A. dc Quatrefages. Paris, 1819.
4
26 HISTORY OF TlIK SUBJECT.
■mandilln [Amphiporua lacfi/loreiis),am\ notices the ease with which the latter species can be kept in confinement. lie remarks that his captive specimens thrust out their proboscides and stylets, probably for the ])urj)ose of cupturinj? the Infusoria that swarmed in his vessels. Moreover, he also saw a liUlu J'olia attack a Cyclops. I am, however, of opinion that all the interesting motions he witnessed in such cases were accidental, and not due to predaceous habits. There is no wonder he found no debris of food in the proboscis, since this is not at all an alimentary organ, lie observed their tolerance of ])ressurc between glasses under the microscope, and the fatal result of immersion in fresh water, l)ut gave no remarks of importance in regard to the reproduction of lost parts.
In the second division of the memoir he discourses on the anatomy of the Nemcrteans, and it may suffice at present only to allude to his results. He was certainly one of the first to anatomise the animals in a truly scientific manner, and his drawings of structure, though scarcely accurate, are very beautiful. He is wrong in averring that a fibrous layer exists in connection with the dermal tissues ; his muscular coats of the body-wall (external longitudinal and internal circular) agree neither with the arrangement in the Enopla nor with that in the Anopla; the description of flie general cavity of the body is obscure and misleading, and he located the corpuscular fiuid there instead of in the proboscidian sheath; he altogether went astray in his interpretation of the proboscis, which he took for a digestive system (dividing it into proboscis, oesophagus, and intestine), and even his anatomy of the organ (proboscis), as it exists, is erroneous. He only examined the circulation in the Enopla. He confounded the generative with the true digestive system, and, indeed, fell behind the early observations of Duges in this respect.
In the third part he treats of the analogies and zoological affinities of the Nemcrteans, which he regarded as the degraded representatives of a more elevated type. While descanting on their general structure and relations, he observes that the organic apparatus presents the same complication in the large Z/z/ras as in the minute 7t'/rfl«/'e;//;//ff, but the elements (of such structure) undergo a degradation in the latter ; a statement which is somewhat obscure, since the types of the forms differ entirely. For the same reason his comparison of the integuments of Borlas/a angVue, Nemcrfes hahneci, and ToJin fihnn, is fallacious. He points out that no part of the vascular system is in immediate contact with the respii'atory surface, while the vessels arc always plunged in the licjuid of the abdominal cavity, which he therefore considers as the active agent in nutrition. He compares this corpuscular fluid to the chjh, for, he says, into it the products of digestion are transmitted directly from the alimentary tube (proboscis) ; further, it resembles the l^mjili, because it receives the internal products of the organism ; finally, it is like the blood, becau.se it is the direct ao-ent in the nutrition of the es2;s, and, since it bathes the muscular coats of the body, it is also charged with their nourishment. With so formidable an array of functions for this (proboscidian) fluid, it is no wonder he asks — whether the contents of the blood-vessels merit the name of blood ? He was not aware, however, that this fluid is enclosed within a special muscular sheath, and nowhere comes in contact either with blood-vessel, body-wall, or ovaries.
With regard to systematic arrangement, ]\I. de Quatrefages retains the class Turbellaria of Prof. Ehrcnberg, exclusive of Gordiits and Nais, and which he would apparently link on to the Trematoda of ]\I. INIilne Edwards. He does not altogether place the Plauarise and Distomae together, but mentions that if fiu'ther researches should reveal the same vascular apparatus in the
HISTORY OF THE SUBJECT. 27
former as M. Blanchard has found in the latter, tlien there is no obstacle to their sequence. He rcn-arded the li/idbdocccla as iiiterincdiatc between tiic Pianarians and Nenierteans ; rcsemljling the former by the general disposition of their genital organs, the union of the sexes, and the organs of the senses; the latter by tiic simplicity of the digestive canal and the disposition of the vascular and nervous systems. He places the Ncmerteans uiidir the second sub-class of the Turlicilaria, for wliich lu; advances the term Minca-Jn} tlnis :
Class. Suh-classes. Orders.
f r Intestine ramified . . . Dendroceela.
I TuRHELLAltlA " MoNOKlUES " -|
I, Intestine simple . . . JthaMoctela.
[
TuKiiELLAniA "DioiuuEs" Mioctela.
Various authors have followed more or less closely the descriptions and classification of De Quatrefages. j\lilne Edwards, for instance, in 1S59 gives a summary of the views then known with regard to the Nenierteans, but inclines to the side of his distinguished countryman. Hence he observed that he considered it premature to decide as to the presence or absence of an anus, and to declare the fundamental structure of the digestive apparatus. This publication of M. de Quatrefages constitutes an important era in Nemertean literature, and, notwithstanding its errors, shows tliat the talented author strove to extend our knowledge of the structure of obscui'e inver- tebrate animals, at a time when such work was less common, and the instruments for minute research less complete.
In 1849 R. Leuckart" describes a Nemertean under the name oi Amp/ii/jonts Neesii, Oirst., M'liich in all probability refers to the common British form. He correctly locates the position of the mouth in the Anopla, but he does not define its position in the former (one of the Enopla) further than by mentioning that it is on the ventral surface, and in the form of a small fissure without swollen lips. The other species, \\7.. Ncmertes fasca, N. annelkda, and Folia canescens, described in this paper, I have not been able to determine.
The publication of the ' Systcma Helminthum ' of C. M. Dicsing in 1850 is chiefly interesting in regard to his classification of the group.' He arranged the Xenierteans as the third tribe of his second order [Turbellaria) of his first sub-class and section Achactkelmiathu. He characterised them as worms having a very contractile body, for the most part flattened or rounded, much longer than broad. No anus. Sexes distinct. This triljo (Xemertinea) he divided into four sub-tribes, according to the presence or absence of lobes or tissures, viz., Ilolocfphala, Lohocephala, Ptichocephala, and Hhnfjadoccphala, distinguishing the genera according to the presence or absence of eyes, position of the mouth, so-called genital aperture, and other evident external characters. The complete confusion apparent in the incongruous grouping of the genera by the author makes it advisable to dwell no longer on this phase of Nemertean history. His classi- fication is quite worthless, and could only have been constructed by one almost totally unac- quainted with the animals otherwise than from descriptions, which, unfortunately, were too often misleadiu";-
D"
' From jutiow, to diminisli, and kihWu, intestine.
- "Zur Kenntuiss dcr Fuiuki von Island," ' Arcliiv fur Naturges.,' 1819, p. 149.
•'' 'Systema Helminthum,' vol. i, pp. 182 and 183, and pp. 238 — 277. Viiidobonse, 1850.
28 HISTORY OF THE SUIJJECT.
A valnalile paper on the ciiil)ryology of Nemcrtes was produced by E. Desor in 1650,' whicli for tlu; first time disclosed the remarkable development in certain of the Anopla. His observations were made on a species, from the shores of New England, allied in the closest manner to the common IJiitish Linem (/t-HHcremu. The ova are laid in the form of flask-siiaped cajisules, each of whicli contains from one to seven yolks. Desor discovered that after a time the yolk becomes ciliated, and that the young Uncus emerges from this ciliated investment, so that just before extrusion there are two spheres of ciliation, viz. the external coating, and the skin of the contained embryo.
Dr. Joseph Leidy " described in 1850-51 a species of Rhynchoscolex (72. «>«/;/ra), which is prol)ably a Nemertean, and a new genus, Emea, constructed for the reception of a freshwater species from the neighbourhood of Philadelphia. He calls the proboscis the alimentary tract, and the stylet-region a gizzard armed with a dental apparatus. In the former, he states, are numerous villosc appendages (evidently referring to the glandular papilla." of the proboscis). He recognised the proboscidian fluid and its corpuscles, but he defined it only as occupying the interior of the body. His statement that the generative system consists of two tortuous and capacious tubes is also open to doubt.
In a second paper in the same volume Mie mentions il/<?cXe//a /ac/ea, n. s., a form which can swim like an eel. This is evidently one of the Anopla, yet he terms the mouth the generative aperture.
In a third communication* he makes some amendments in the description of his genus Emea, apparently after having seen the memoirs of Dc Quatrcfages. He now observes that the mopha(jm is styliferous, being " furnished at its bottom with a single spine or nail-like tooth, and four others on each side in a rudimentary condition, enclosed in a sac." He likewise says that the intestine becomes obliterated posterioily, whereas he formerly stated that the mouth and aims were terminal.
In a paper remarkable only for the unsoundness of the views contained therein, Mr. Charles Girard, in 1S51, proposed to class the Nemerteans and Planarians with the MoUusca, and not with the Annelids at all." It is scarcely necessary to enter into his theories, but it may be inte- resting to note that this reformer rests his conclusions on so many grounds (with special reference to the Xenierteans) as the following : — Their soft, glutinous, ciliated body ; their simple nervous system, consisting of a small number of cephalic ganglia ; their eye-specks, development and habits.
Dr. Max S. Schultze published an important work during the same year on the Turhdlaria of Ehrenbcrg, accompanied by exquisitely engraved copper plates." The Xemerteans, however, were but briefly alluded to in the third part of the treatise, under the heads of Prorliynchus stapialis and Tctrastemma obscuriim respectively. The former is chiefly interesting on account of the atrophied condition of the proboscis and its stylet-apparatus, which the author considered to be an aggressive organ, poison being instilled into wounds by the contraction of the posterior chamber. It forms an advantageous comparison with the aberrant Nemertes carcinophila.
' 'Boston Journ. Xat. Hist.,' vol. vi, No. 1, pp. 1—12, pis. 1 and 2.
- 'Proceed. Acad. Nat. Sc. Philadelph.,' vol. v, p. 125.
s Ibid., pp. 223 and 22^.
■* Ibid., pp. 287 aud 288.
5 ' American Journ. So.,' 2nd ser., vol. xi, No. 31, pp. 41—53.
Beitriige zur Naturgescbichte der Turbellarien.' Erste Abtheilung. 7 pis. Greifswald, 1851.
6 (
HISTORY OF 'rilK SUBJECT. 20
IMany valuable remarks occur in the article on Telrasiemma ohcurum concerning the proboscis, the dcvelopnunt of the stylets, the position of the mouth, the digestive and circulatory systems. lie over-estimated the relation of the marginal stylets to the central, for he thought that the former supplied new organs to the latter. He also confounded the circulatory with a water-vascular system. He, however, exhibits great care and accuracy in his observations, which put Nemertcan anatomy on a sounder footing than it had hitherto held.
He divided the Turbellaria into two sub-classes, thus :
Classis Turbellaria. I. Sub-classis Aprocla.
\ . Ordo Dendrocoela. •1. „ Rhabdocoela.
II. Sub-classis Procfucha.
1. Ordo xVrhynchia.
2. ,, Rhynehococla (Nemertina).
This classification has been adojjted by Dr. Rud. Leuckart in the appendix to Van der lioeven's ' Handbuch der Zoologie.'
Dr. Thomas Williams, in his 'Report on the British Annelida,' at this time' propounded several erroneous statements in relation to the anatomy of the Ncmertcans. Thus, while correctly regarding the sacculated chamber as connected with the digestive system (though he denied the existence of an anus), he called the ganglia " hearts," and wrongly averred that the " oesophageal intestine" (proboscis) terminated in a distinct papillose outlet situated a short distance behind the cephalic extremity of the body, as in the Sipunculidse. His attempt to prove the homology between his " closed alimentaiy chamber " and the spongy mass in Tania rests upon no secure foundation, and does not stand the light of the correct investigations of that period or the present; and the same remark applies with respect to his grouping Co/t////* with the Nemerteans.
An interesting addition to our knowledge of the development of the group was made by Dr. W. Busch, who at this stage gave a drawing and description of a novel animal from the harbour of Trieste, on which he bestowed the name of Alardus c.audatusr This is evidently the young of a Micrura, and J. ^liillcr afterwards connected its growth with that of his Fylidiim. Dr. Busch termed the aperture of the proboscis the mouth, did not recognise the proboscis (though its position is indicated in his figure), and was puzzled by the cephalic sacs, which, as usual in the young of the Anopla, were very large.
Dr. Thos. Williams in 1S52 again introduces the subject of the Ncmertean "chylaqueous fluid," in his paper "On the Blood-proper and Chylaqeous Fluid of Invertebrate Animals."' Here he also confounds the corpuscles in the proboscidian sheath with the contents of his " alimentary caeca."
1 ' Keport of the Brit. Assoc.,' 1851, pp. 238, &c., pi. xi.
"- ' Bcobachtungeu iiber Anat. u. Entwickelung einigcr wirb. Seetliicrc' Berlin, 1851, p. Ill, taf. xi, f. 8.
= 'Philos. Transact.,' 1852, part ii, p. 027, pi. xxxii, f. 25.
30 HISTORY OF THE SUBJECT.
During the same year (1S52) Dr. Max Miiller' gave an account of certain structures froiu the |)rol)oscides of an luiknown McrlccUa and Alardus caudalux, wliich lie termed l)acillary bodies, and some of those from tiie lirst-mentioncd form contained long urticating threads. Tiiesc bodies arc the elements of the glandular papillae, and I have not as yet seen such (urticating) organs in the British species, although fine processes and mucus-threads occasionally project from the summits of the papillae imdcr pressure.
Tn the zoological sketches of Dr. Max Schultze, published at this time,- the researches of E. Desor on development are reviewed and corrected from observations on Nemerles oHvacca, a species which the author considers identical with Dr. Johnston's form {Lineus yesserenm). He also issues a very important scheme for the arrangement of the Nemerteans, which scheme is founded on the basis advanced by Dr. .lohnston many yeare before, viz. the absence or presence of stylets in the proboscis. It is as follows :
A^emerftnea.
Central nervous system consisting of two ganglia on each side, an anterior and posterior, wliicii iia\c two commissures, a superior and inferior, between which the proboscis passes.
Anopla. Enojjia.
Proboscis without stylets. Proboscis with stylets.
The ganglia united at their anterior border by a long Anterior border of the ganglia rounded. The dorsal
and slender dorsal commissure. The lateral nerve-trunk commissure in the form of a small band between the
springing from the anterior portion of the nntcriorgnnglion, dorsal surfaces of the ganglia. The lateral nerve-trunlis
80 that the posterior end is rounded. The ventral com- forming a cnntinuation of the posterior ganglia. The
missure common to both ganglia. ventral commissure common to both ganglia.
On each side of the head is a large and often very The long cephalic furrow absent ; but there are ciliated
shallow fmrow, having a small ciliated pit at the posterior pits, end.
Though his classification is by no means complete, it certainly marks a decided advance on the schemes of his predecessors.
lew modern naturalists have done more to advance our knowledge of the habits of these unfamiliar forms than tlu' late Sir John Graham Dalyell, whose patience and perseverance— not devoid of intuitive skill — are worthy of all praise. In the second volume of his ' Powers of the Creator' (1853),^ he describes about twenty British species. Several of these, however, refer to diti'erent states of the same animal, but all can be readily identified with the exception of Feniii- culus crassiis. He grouped the Nemerteans under three genera, ^^z. fourteen under Gordim, five under Vermicuks, and one under Planaria. He thought they might be classified thus : — (1) Those wanting specks or eyes; (2) those where specks of an indefinite number were evidently present ; (3) those with two eyes ; and (4) those with four eyes. If this worthy natm-alist had lived to superintend the publication of the volume, several inaccuracies which had been overlooked in his earlier notes would have been corrected, as, for instance, the remark under
1 'Observat. Auatom. do Vermibus qiiibusdam maritimis.' Beroliui, 1852. - ' Zeitsch. fiir wiss. Zool.,' Bd. iv, p. 179. 1852.
The Powers of the Creator displayed in the Creatiou/ &e., vol. ii. London, 1853.
.■> (
TTTRTOUy OK TUK SUBJECT. 31
Linens mariiiiis, that lie was not aware tlic animal liad a proboscis, for he distinctly refers to this organ in otiier species. He also correctly observed the tiue mouth in the Anopla, since he saw the animals feeding, and recorded many interesting facts with regard to the deposition of ova. The great Clordinsfrfif/ills has not been procnred since he found it, so far as can be ascertained. The figures in this work are executed with care, and most are coloured. R. Leuckart, in his abstract of the literature of the Turbellaria for ISTjS' furnishes the synonyms of the majority of the species described by this author.
In the same year (1853) Charles Girard gives descriptions of some new Xemerteans from the coasts of the Carolinas, for which he establishes several genera." He interprets the true mouth in the Anopla as the aperture of the generative system, while he terms the proboscidian aperture the mouth. The description of his Stinpsonia, as it appears in this paper, differs from Bipalium in several important particulars.
Dr. Thomas Williams'" likewise published, in 1S5;3, an account of the method of aquatic respiration in invertebrate animals, and specially refers to the " Nemcrtidrc " as having the whole of the digestive chamber filled with a corpuscular fluid, which, he states, carries out this important function. He shows a drawing of the alimentary system of a species named Nemertes camillee, which may be synonymous either with N. gracilis or N. Nec-sii, probably the former. He still erroneously places the anus towards the anterior end, and avers that the organization of the "Nemertine Annelida" conforms in every essential particular to that of the Cestoid Entozoa.
Next year C. Gegenbaur * mentions that he frequently found Pylidium gyrans at Messina, and gives remarks on its structure. From his description it would appear that he found the Ncmertean Fijlidiuiii, but did not quite interpret its full relationship. He noticed that it differed from the Echinoderm-Py?V/»;;«, and at first thought that the whitish oval body in its interior had been swallowed, but the occurrence of others of the same species convinced him of the connection between the two.
In his 'Archiv'for 1854 J. j\Iiiller adds still further to our information on the develoj)- ment of the Nemertean Pi/liclium:' He recognises the identity of the contained body with the Alardus caudatus of Dr. Jkisch, and gives a somewhat better figure of the worm, with a normal arrangement of the caudal process ; and his remarks on its structure are likewise more correct. He mentions the fact that Micriira J'asclohda, Ehrcnberg, has a terminal process, but does not state the identity of the two, since his young form possesses only two eyes, whereas the former has ten. In this paper he also notes certain experiments with hot water which he performed on Meckelia somatotomus, Leuckart.
Dr. E. Grube," in his introductory remarks on the Nemerteans (in 1855), criticises the interpretations of the proboscis adopted by ^I. de Quatrefages, and points out that the true digestive apparatus lies below the former, each system opening by a definite aperttn-c in the snout of the Anopla. He thought it prol)al)le that the Nemerteans used the proboscis after the manner of
' 'Archly fiir Naturges.,' 1859, pp. 18" and 188. - 'Proceed. Acad. Nat. So. Philadelphia,' vol. vi, 1853, pp. 365-367. ^ 'Ann. Nat. Hist.,' 2nd scr., vol. xii, pp. 341, &c., plate xiii, figs. 1 and 2. * 'Zeitsch. fur wiss. Zool.,' Bd. v, 1851., p. 345. = ' Archiv fiir Anat.,' 1851, pp. 75— 84., taf. 4, f. 2—8.
« " Bemcrkungen iibcr cinige Helminthcn u. :Mccrwiirraer," 'Archiv fur Naturges.,' 1855, pp. 145—152, taf. 7, f. 1—4.
32 HISTORY OF THE SUBJECT.
the clcj)liaut, viz. for stjuiitiiig fluid containing prey into tlieir months. In tliis paper several species are descriljcd, viz. (1) Meclcelia annuluta, the greenish form with white stripes previously mentioned, which, if it had a terminal process, would be closely allied to Micrura fcusciolala. (2) Mcch'lia auraiiliaca, a species (of ^licrura) with a caudal process. (3) Opldocephalus auripundatm, one of the Anopla. (4) Ncmerlen j)urpun-a, Johnst., probably a reddish variety of LintniH gesserensis. (5) Ncmertes laclea, a species intimately connected with the Lineus lacteus of Montagu.
In the same year (1855) W. Stinipson' gave descriptions of some Nemcrteans from the China, Japan, and other seas. He considered the month to l)e the genital fissure. Two of his species, viz. Valcncinia annulnta and McckcUa olivucea, seem to be identical with those found in Britain, at least so far as one can judge from descriptions. External characters are chiefly relied on, and tiie accounts of the species are comparatively meagre.
Dr. J. E. Gray," in 1S.")7, made a few remarks on a large Linem, which he had received from J\lr. Beattie, of Montrose. He correctly called the longitudinal slit the mouth, and pro- visionally termed the animal L. Beatlicei. Four lithograpiiic figures are given in the plate connected with this jjaper, the three upper from the ventral surface of the snout in various degrees of contraction, and the fourth a side view in semi-contraction. The preparation in the British I\Iuseuiu is labclk'd by Dr. Baird " Serpcntaria frarjiliny and in all probability he is correct. It is a very large specimen, although fragmentary.
In the ' Icones Zootomicac ' of Cams, Dr. Max Schultzc contributes a paper on the structure of the Ncmcrtcans, chiefly of Tctrastcmma obscunim? He supplies no definite account of the floor of the anterior chamber of the jjroboscis, or of the stylet-region, and the structure of the latter is not advanced in detail beyond his previous description. The marginal stylets are still termed reserve-stylets. No oesophageal division of the digestive tract is shown. He has endea- voured to reconcile his older and incomplete representation of the circulatory system with modem views by carrying the lateral trunks (which, in his previous figure, resembled the pale l)order of the proboscidian sheath) into the snout, and introducing a central vessel from end to end. As might be expected under the circumstances, however, some confusion occurs ; thus, the central vessel is carried forward in the snout in front of the ganglia to the middle of the arch, instead of sending off the anastomotic behind the ganglia to join the lateral vessels. The arrangement of his water- vascular system is something quite different from anything seen in our examples. In his former delineation I considered he had mistaken the ordinary blood-vessels for a water-vascular system, but now, since he has put in the three main trunks as an entirely distinct series, our decision is the more acciu-ate. The author is somewhat confused in this matter. He gives two new figures, one of wliicli {Tctrastemma) correctly indicates the proboscidian bodies in the interior of the proboscidian sheath, while the other is by no means a characteristic figure of Lineus (/esserensis, inside a sheath of o\a.
^Ir. Beattie,* without reference to the Nemerteau previously sent to Dr. Gray, goes on, in the 'Proceedings of the Zoological Society' for 1S5S, to relate that he had received a very long
1 ' Proceed. Acad. Xat. Sc, Pliiladelphia,' vol. vii, pp. 381 and 389. 1855. - 'Proceed. Zool. Soc' part xxv, 1857, p. 210, Anuulosa, pi. 47. ' ' Icones Zootomic.T,' J. V. Cams, part i, tab. 8, f. 10 — 15. Leipzig, 1857. ■* ' Proceed. Zool. Soc.,' part ssvi, 1858, p. 307.
HISTORY OF THE SUBJECT. 33
example of Lineus lon^issimiis, which after four days' captivity produced a cream-coloured young; one is inches long, and about two thirds of a line or I'^tii of an incii in diameter. This " young animal" lived about a week after its ex])ulsion. Dr. Gray atkls that Dr. Haird had examined the specimen produced, and thinks it very probably the true offspring of the Nemertes. An examination in the British Museum shows that the "young animal," or "tubus cibarius," as the latter lamented observer afterwards named it, is the proboscis, probably, of Cerebratulus angulatm.
In the 'Archiv fiir Anatomic' for the same year, Dr. A. Krolin^ repeats and 'confirms Miiller's observations on the Ncmertean Pylidhun, and it may be mentioned that this author independently discovered the connection of the structure with a Turbellarian in 1S51. The editor (J. Miiller) appends a note to this paper, stating that Micrura of Ehrenbcrg is identical with Alardm, Busch, and he gives a list with the synonyms of four species of Micrura.
An elaborate article on the Ncmertean Pi/Iidiiim subsequently appeared in the same volume of the 'Archiv' (185S) by Leuckart and Pagenstechcr, who found two species at Heligoland, viz. P. gyrans of IMiiller, and another which they termed P. auriculatum? They traced most minutely the develoj)ment and relations of the various organs in the embryo of P. gi/rans (one of the Anopla), but the origin of the Pj/Hdium itself had hitherto cscaj)cd notice. Their species had no style or caudal process after extrusion. Two eyes are developed before the worm separates from the Pylidium. Their account was the best on the subject until the appearance of E. Metschnikoff's recent paper.
In the same year (1858) W. Stimpson gave in his 'Prodroinus' a list, with brief descrip- tions, of the Nemerteans collected in the United States' expedition to the Northern Pacific, and grouped his species under old and new genera, which were arranged to suit the views of the author. His classification is as follows : —
A. A ventral aperture situated under the head or neck. No eyes.
a. Lateral fissures on the sides of the head.
1. Body of the ordinary form.
Under this group he places Lineus, Sowerby, Cerebratulus, Renier, MecJceUa, Auct. limit., and Serpentaria. The statement concerning the absence of eyes is erroneous.
2. Body rolled at the edges. — Dijjlopleura.
b. No lateral fissures.
1. Proboscidian aperture terminal. — Taniosoma, n. g.
2. Proboscidian aperture subterminal. — Valcncinia.
B. No ventral aperture. Eyes two or many.
a. Fissures or furrows at the margins of the head. — DicJiilus, n. g., Tetrastemma,
Hemp, and Ehrcnb., Cephalonema, n.g., Emplectonema.
b. ^A'ithout pits or furrows.
1. Eyes two. — Biphmma, Dicelis, n. g., Polydcmma, Hemp, and Ehrcnb., Polina, n. g., Tatsnoskia, Cosmoccphala.
' ' Archiv fiir Anat.,' 1858, pp. 289—293.
- 'Archiv fiir Auat.,' 1858, pp. 5G9— 587, taf. 19.
34 HISTORY OF THE SUBJECT.
By his first great division, based on the presence or absence of the ventral aperture (liy vvliicli lie {jrobably means the mouth), the Eiiopla are in a rough way separated from the Aiioplii, l)ut the classification, being founded on external characters, fails just where it is most wanted. The autlior considerably extends the limits of the known species, and gives an interesting chronological list of the genera.'
])r. E. Graefl'e- next furnishes an account of a yellowish-green Tetrastemma from Nice, which is remarkable in having lenses to its eyes, and in possessing what he terms otolithes. The presence of the latter organs, if no misconception occurred, is something very different from anything seen by us in the British Nemerteans, but is analogous to the otolilhes described by several authors in other invertebrates, such as the MoUusca.
Dr. Thomas Williams, in a mor|)hological paper, published in 1858, committed some serious errors in his interpretation of the Nemcrtean generative organs, which, he said, coincided in shape, place, and structure, with the ovarian or female series of the llirudinei.' Moreover, he asserted (hat they corresponded in number not with the caeca of the alimentary canal, but with the aunuli of the body, a statement requiring some further proof, since it is very doulitful if the term annuli can be used in any sense with respect to the Nemertean body, which is not in truth segmented. His re|)resentation of the ovaria or female segmental organs in PoHa quadriociilala is imaginary, for the organs are reversed, made bifid at one end, and filled with minute cells, — conditions at variance with nature. He thought that the Nemerteans should be separated from the Planarians by a very wide interval ; indeed, he affirmed that they had only one character in common, viz. the ciliated integument. This cannot be supported in the sense he means, though the gap between the two is by no means narrow.
Gegenbaur ' the following year arranged the Nemerteans under the sub-class Plalyel- minthes, order 3, Turbellaria R/ii/nchocala. He followed De Quatrefages in regard to the general anatomy of the animals.
Selmuuda at this time described many foreign Nemerteans, which he had collected during his voyages, in a finely illustrated work.' He divided the order Nemertinea into two sub-orders — based on the absence or presence of the " respiratory organs," and termed respectively Ahranchiala and liliocJniiobranv/iiafa. The former he portions into families according to the shape of the head ; the latter is similarly divided, in conformity with the number of the snp|)osed branchial furrows or fissures. He gave the opinion, in his introduction, that the structure of the stylet-region of the proboscis might be of service in classifying the smaller species, but was utterly useless in the larger forms, and those preserved in museums, hence he was obliged to take the former mode of discrimination. But it is impossible to study such animals with any degree of accuracy as spirit- preparations, without first having investigated them as living subjects. It is imnecessary to give
' " Prodromus descriptiouis Animalium Evertebratorum, quae in Espeditione ad Oceanum Pacificum Septentrioiialcm, a Republica Federata missa," &c., part ii, Turbellarieorum Nemertineorum ; 'Proceed. Acad. Nat. Sc.,' Philadelphia, 1858, pp. 159— 1G5.
- ' Beobachtuugeu iibcr Kadiateu u. Wiirmer in Nizza,' pp. 53 and 54. Zurich, 1858.
^ "On tlie Structure aud Homology of the Reproductive Organs of the Annelids," 'Philos. Trans.,' 1858, pp. 131— 13.^, pi. 8, f. 24..
* ' Grundzuge der Vergleichenden Anatomic.' Leipzig, 1859.
^ ' Neue Turbell., Eotat. u. Anneliden beobaclitet u. gesammelt auf einer Reise um die Erde, 1853 bis 1857,' i, 1 ; lutrod., pp. xiii aud xiv, and pp. 40 — 16. taf. 9 — 11. Leipzig, 1859.
HISTORY OF THK SUBJECT. 35
iiiinuti' details of the classification, since it appears to be little else tlian a confused grouping. In tlio liist place, it has not yet been proved that these furrows and fissures are branchial ; secondly, the locating in the family llnlorcphaln genera so widely divergent as Valencinia, De Quatrefages, and Oinwaloplca, l']hi'eiil)erg, the arranging under two ditt'ereiit sub-orders of the closely allied forms (Erstedia and Telrmfrmmu, and tin; statement tiial in Micrura the head is furnished with a single terminal transverse fissure, are certainly sufficient to shake our faith in the author's knowledge of the subject.
An interesting contribution to the anatomy and zoology of the Turbcllaria was published by M. van Bencden in 1S60,' the Nemerteans occupying the first part of the memoir. He correctly observed the apertures of the generative organs along the sides, but erroneously con- sidered that the proboscis floated in the general cavity of the body. He had good reasons for supposing that the coat of the digestive tract combined the functions of the liver as well as an alimentary organ {)roper. His anatomy of the cephalic sacs in the Anopla was inaccurate. He discovered that some of the endiryos in Nemertes communis were ciliated in the ova before laying; and his observations on the developnient of Fo/ia involuta {Nemertes carcinophila, KoUiker), form the most valuable portion of the memoir, though he was wrong in supposing that one form was evolved out of the other, like a scolcx engendering a proylottis. lie also made the mistake of placing the mouth of the Enopla (ex. Poiia obsciira) behind the ganglia, instead of in front of them. His memoir is illustrated by four lithographic plates, some of the figures being coloured.
E. Claparede, in his remarks on Tefrastemma varicolor, CErst., and another from Skye," in ISGl, clearly pointed out the duct to the marginal stylet-sacs. He considered the latter to be the receptacles for stylets rejected from the central ap|)aratus, and he combated the contrary view held by Max Schultze. While he observed the cavity of the reservoir, he fell into the error of calling the posterior chamber the muscular retractor of the organ. He also notes the form of the papilhe in the proboscis of Ccplialothrix Uneala.
In ls()2 Diesiiig produced a 'Revision ' of the Tiirbellaria,^ the Nemerteans being placed nnder the second Tribe Rhynchocalu, some of them occurring after the Families RhynchoHcolecidea and Gyratricina in his sub-tribe Rhynckocala Aporocephala, and the rest under a second sub- tribe B. Porocephala. The former contains the families Borlasiea, Ommatopliora, ^fkriirca, Ilypoloba, and. Acroloba ; the latter Prorhynch'uUe, Emeidea, Typ/ilonoiicrlinea, Loxorrhochmidea and Eunemertinea. The confusion and errors in this brochure are not fewer than in the preceding, and render it almost beyond the pale of criticism.
The most important and at the same time the most recent publication of note on the Nemerteans is that of Professor Keferstein, from observations made at St. Vaast-la-Hougue.* It will be necessary to enter somewhat minutely into this contribution, which marks another era in Nemertean literature. He first treats of their classification as follows : —
' ' Roclicrrlics sur la Fauiie Littoralc dc Bclgique/ extrait du tome xxxii des ' Memoircs de I'Acadeuiie iloyale des Sciences de Uelgique/ 18G0.
- ' Recherches Anat. sur les Anelides, Turbellaries, &c., observes dans les Hel)rides.' Geneve, 1861.
' " Revision der Turbellarien, Abthcilung Rhabdocoelen." ' Sitzungsb. d. Kais. Akad. d. wissensch. Wien.,' 1862, pp. lU'J— 201. and 217—306.
^ 'Zeitsch. fiir wiss. Zool.,' Bd. xii, pp. 51—90, taf. 5—7, 1862,
36 HISTORY OF THE SUBJECT.
Or</er.— NEMERTINEA.
Sub-order I. — Nemi'.rtinua exopla, Max Schullze.
Proboscis furnished with a stylet-apparatus.
Fam. 1. — TkemacephaliD;E.
The fissures of tlic head short, of a transverse (linear) form, or funnel-shaped. Brain with the superior ganglion less elongated than the inferior, and separated by an almost free border from tlic latter; the lateral nerve springing from the posterior end of the inferior ganglion, or almost a continuation thereof.
(a) TretnacephaJidcB without the lobe-shaped front of the head.
Gen. 1. Volia, Delle Chiaje, 1825. Head easily distinguished from the body, narrowed anteriorly, without eyes. Mouth near the anterior end. Body diminished posteriorly.
Gen. 2. Borlasia, Oken (char, reform.). Head not distinguished from the body, mostly with eyes. IMouth in some removed the breadth of the head from the anterior end. Body less diminished jiosteriorly, and generally somewhat short.
Gen. 3. (Erstcdia, Quatref., 1846. Head not distinguished from the body ; lateral nerves coursing near the median line, not, as generally, entirely confined to the sides.
(b) Tremaceplialida with the lobe-shaped head anteriorly.
Gen. 4. Micrura, Ehrenberg, 1S31. Head not distinguished from the body; anteriorly with a transverse fissure, so as to form an upper and under lip, between which the proboscis emerges. With eyes. Mouth situated about the breadth of the head from the anterior end.
Gen. 5. Frosorlioclimus, gen. nov. Head not distinguished from the body, snout with three lobes, the anterior border being heart-shaped, with the third lobe placed dorsally (over the notch). The track of the proboscis separates the inferior lobes anteriorly. With eyes. Mouth placed a pair of head-breadths from the anterior end. Body moderately long and contractile.
Gen. 6. Lohilabrum, Blainville, lb2S. Head not distinguished from the body, anterior end with four lobes ; this anterior end is separated into an upper and a lower lip, between which the proboscis passes ; and, again, the border is heart-shaped (emarginate), the upper more deeply than the under, so that it seems to be provided with two teutacula.
Sub-order H. — Nemertixea anopla, Max Schultze. Proboscis not supphed with a stylet-apparatus.
Fam. 2. — RHOCHMOCEPHALIDiE.
The cephalic fissures are long, and occupy the entire side of the head. Brain with the upper ganglion covering the inferior completely ; the lateral nerve springing from the side of the inferior ganglion in front of its posterior and pointed ending.
HISTORY OF THE SUBJECT. 37
(a) R/wchmocephalidcB without tlie lobc-shapcd snout.
Gen. 7. Linens, Sowerby, 1804. Head easily distinguished from the body, somewhat broad. Mostly without eyes. Cephalic fissures extending to the mouth. Posterior part of body almost pointed, fiat, very long and contractile, sonietimcs knotted.
Gen. S. — Cerebratulii-s, Renicr, lb07. Head not distinguished from the body, somewhat smaller, but ending bluntly. Cephalic fissures extending to the mouth. Body not smaller towards the posterior end, flat, moderately long and slightly contractile.
Gen. 9. — Nemertes, Cuv. (char, reform). Head not distinguished from the body. Cephalic fissures long, extending to the mouth. Mostly with eyes. Body flat, moderately long and con- tractile.
(b) — RhochmocephalidtB with the lobe-shaped snout.
Gen. 10. — Opliiocephalus, Dellc Cliiaje, 1829. Head distinguished from the body, some- what smaller, but ending bluntly, the snout having a deep median groove on the dorsal and ventral surfaces, so that it appears bilobed. Cephalic fissures long, extending to the mouth. No eyes. Body long.
Fam. 3. GYJINOCEPHALID.i!.
The cephalic fissures entirely lost. Brain like that in Polia, but the superior ganglion covers the inferior much less. The lateral nerve proceeds from the entire side of the inferior ganglion, or is almost a continuation thereof.
Gen. 11. — Cephalothrix, Q^Irsted, 1844. Head not distinguished from the body, very long and pointed. The mouth lies more than the breadth of a head from the anterior end. Body rounded, very long, filiform, and very contractile.
No fault can be found with the primary subdivisions or sub-orders (after Max Schultze), and the family-name Tremacephalida, as applied to the AmpMporini, is not seriously wrong, but the sub-families and genera of this portion require complete reformation. His criterion of the " absence of the lobe-shaped snout" does not stand the author in good stead if we may judge from the genera he has thrown together in the sub-family. The first of his genera [Polia] seems to me to be in a questionable position, since the Nemertean described by Delle Chiaje under the name of Polia siphunculiis is, so far as I can make out, one of the Anopla. The second genus, Borlasia, has a very unfortimate name ; for, while I agree with the author as to the propriety of preserving the title commemorative of the early English naturalist, it certainly ought not to be bestowed on a group of Nemerteans totally difierent in structure from that form {Linens marinus) to which the name was originally given by Oken. The author has simply followed De Quatrefages in the formation of the third genus CErsfedia, the anatomy of which, especially the position of the nerve- trunks, difl'ers in no respect from the type of the Enopla. A still more serious error has been committed with the fourth genus, Micrura, this being a true member of the Anopla, and having no connection with Tetrastemma, Ehrenbcrg, or other representative of the Enopla. The fifth genus, Prosorhochmm, may be allowed to stand, as descriptive of a curious example of the Enopla, closely allied to Tetrastemma, discovered by the author. The sixth genus, LobUahrum, was constituted by De Blainville for a form pertaining to the Anopla, and, therefore, is quite out of place in its present position. There are, perhaps, fewer errors of commission in his second
38 HISTORY OF THE SUBJECT.
sub-order [Nemertinea Anopla), though his description of the family requires some additions, and the application of the test of the "lobe-shaped snout" is of no moment. The {jenus Linem is good, but Ccrebratulm, the next or eighth genus, requires further examination. The ninth genus, Nemertes, seems quite superfluous, for tiie Nolosjjermux drrpfinensis of lluschke will fail under other genera. It appears to be an example of the Anopla. The tenth genus, Oplnocephnlm, is also very much open to doubt, since the Ophyocej)halm murenoides of Delle Chiaje may be a variety of Linem marinnx. His third family (Gpnnocephalida) is certainly worthy of separation, and the sole genus, Ccphalolhrix, is satisfactory.
The second part of his memoir is occupied with a description of several species. Amongst these, his Borlasia xplendida, n.s., is the Cerebratulm spectabilin of De Quatrefages ; Nemerles odoculata, n.s., had often been descril)ed before ; while CepIifiloHiriw oci-Ilalu, n.s., and C. lony'iH- sima, n.s., may conveniently, as well as correctly, be included under the well-known form Cephalulli rid' linearis.
The third division is devoted to the anatomy of the group. He did not recognise the differences existing in the nuiscular system of the body-wail of the various types ; the position of the mouth in the Enopia was misunderstood ; and he had no correct knowledge of the tme relations of the muscular sheath of the jirolioscis, or of the minute anatomy of the wall of the latter. He did not discriminate with sufficient accuracy the cephalic sacs and the posterior ending of the ganglia in Lineus. While the author went astray in these and several other anatomical ])oints, he made advances of considerable interest in others, so that his paper is a valuable and most praiseworthy contribution on the Nemertcans. Keferstein's classification, with all its imperfec- tions (and a few superadded), has been adojjted by J. V. Cams in his ' Handbuch der Zoologie.'
Uiesing now issued a third brochure on the subject,' bringing the literature up to the time ; but he did not alter his arrangement, except when introducing " new " genera, many of which, however, had previously appeared in his publications. On the whole, the labours of the writer Imvc chiefly been of value in rendering us acquainted with the various papers relating to the Nemerteans ; and it will be the safest course for the investigator simply to regard these works in this light, and to remember that the author had the disadvantage of being unacquainted with the living animals, and strove to be of use to science even when attacked by a great misfortune.
E. Claparede, in a memoir published shortly after Keferstein's, makes some furtlier remarks on Prosorhochnms Claparedii. He mentions that he had seen ova in the body of the adult worm, and doubts the coiTectness of Professor Keferstein's statement, that he had found three stvlet-sacs in a young specimen, since there are only two in this and other Nemerteans. He also describes a new s})ecies of Telrastemma, viz., T. mannorafum, whicli, however, is only the T. dorsalis of Abildgaard ; and, lastly, he adds a note on (Ersfedia pallida. His obser\ations were made on the coast of Normandy.
In the following year. Dr. Cobbolds did not hesitate to place the Turbellaria amongst the Sterelmintha ; yet I am unable to find out any sound reasons in his description for this grouping, to which I am inclined to object. He arranges them as the first order, Turbellaria, under the
1 ' Nachtriige zur Revision dcr Turbellarien.' Sitzungsb. d. Kais. Akad. d. wissensch. TTien, 1863 (46 Bd.), p. 5.
" ' Bcobaehtungen iiber Anat. u. Entwicklung. wirb. Thiere,' &:c., pp. 23 and 24, taf. r, f. 10—14. Leipzig, 1SG3.
s ' Entozoa : An Introduction to the Study of Helminthology,' &c., cliap. i. Loudon, 1864.
IIISTUIIV UF THE SUBJECT. 39
first sub-class (if liis llcliiiiutlis {Stcrcliiiiiitlia), the; second order being the Tremaloda. He states that " the TiirhcUaria come nearer to the Tri'iuatoda than tliey do to the Suctorial Annelids, wiiich latter, be it reiueiubcred, are furnished with a complete intestinal tube and anus; ami, moreover, their characters, by the intervention of the I'lanarians, are too closely linked on to the Trematoda to permit llieir being elevated by themselves into a separate class." lie divides the Turbellaria into two families, Planariadm and Nemertida. Further, " in common with the Trcmidoda, the Turbellarians have their bodies composed of soft parenchymatous tissue, and in this loose substance the various specialized organs are lodged, without the intervention of any perivisceral cavity. Some of the animals have a flattened form, others are cylindrical, while a third kind are renuu'kably attenuated, and more or less barred by transverse rugae, which form, as It were, a series of spurious joints or articulations. The mouth and digestive apparatus are well developed, but there is no certain evidence as to the existence of an anus in any of the species." It is not the case that the Turbellarians (any more than the Flukes) have their bodies composed of " soft parenchymatous tissue," for their cutaneous and muscular systems are highly developed and differentiated ; and, while the Planarians are no doubt allied in external form, and in the branched condition of their digestive system, to the Trematoda, yet they are still more closely connected with the Nemerteans, which diverge so much from any parasitic worm recorded by this or any other author. With as much reason, I fear, we might place Sayitta amongst fishes, and Amphioxus amongst worms, as assert that " the Nemertidse very closely resemble the common tapeworms, or Cestodes, proj)erly so-called — not only by their band-like forms, but more particularly by their tendency to disitlay transverse ruga), which, as before remarked, acquire a certain degree of regularity." 1 1 is observations on the anatomy of the Nemerteans are behind date ; and in the recent ' Supplement ' ' he seems to have avoided the subject altogether. From what I have seen of the structure of the Flukes and Tapeworms, there would apjjcar to l)e a considerable margin left for the minute anatomical investigators of the future.'
The Nemerteans are placed by Dr. Johnston, in the ' Catalogue of the British Museum,' under Ehrenbergs order Turbellaria, forming the second sub-order Teretidaria of De Blain- ville.' Considerable errors still remain in the author's views as to the structure of the group ; thus the mouth is stated to be terminal, and to give passage to the proboscis ; while the anus is said to open well forward on the ventral surface in some, and in others at the posterior extremity. The mouth in the Anopla is called a genital orifice. Little is added to the information previously published by the author or others uj) to the time of his lamented death ; and thus the work is thrown far behind date. His two genera, CephalolhrLv and Axtcmiiia, are synonymous, while the others pertaining to the Enopla and Anopla are so mixed up that the value of the work is greatly impaired. Several species are described more than once under different names. Still further confusion is propagated in the Appendix by the observations, under the general characters of the Terelularia, that there is no anus; that there are two hearts; and that the female aperture (often mistaken for a mouth) is situated, " sometimes below the head, sometimes large and sucker-like, sometimes posterior and nearly terminal, when it has been mistaken for an
1 London, 18C9.
' The recent paper on the latter group by Professors Sommer and Landois bears out the above remark, which was penned more than three years ago. See 'Zeitsch. f. wiss. Zool.' for March, 1872.
' 'A Catalogue of tlie British Non-Parasitical Worms in the Collection of the British Museum.' Loudon, 1865.
40 HISTORY OF THE SUBJECT.
amis." The early structural observations of Dr. Johnston arc also reprinted from ' Loudon's Magazine,' the ' Magazine of Zoology and Botany,' &c., with the plates, and quotations made from tlic work of Sir J. Dalyeli. It would not be just to state that this treatise advances British science; but much nmst be overlooked in the circumstances of its publication. Its value chiefly lies in being the only English work on the subject.
Dr. Baird, in the 'Proceedings of the Zoological Society for 18G6,'' gives an account of a new species of Mona;cious worm, which is evidently one of the Anopla allied to the Gordius/rayilia of Sir J. Dalycll [Ccrrbratiilus n)if/uhttiiH),\\'\\\\ the margins of the body produced as in the swimming forms. 'J'hc author stated that the ventral slit led into the " visceral cavity," and agreed with many others in regarding the proboscis as the alimentary canal, and its aperture in front, the mouth.
The observations of Mr. Alex. Agassiz' carry those of the experienced Prof. Loven' a stage further with respect to the development of a curious larva, which the former regards as Nemertcan. The most remarkable feature is the discovery of a kind of retrograde n)etamor- phosis which the young animal undergoes, whereby it loses its segmented form and its tentacles, and assimies the simple outline (but not the structure) of a Nemertcan. Further remarks on this interesting communication will be found elsewhere.
In 18C7 the author published a short paper on the Grcgariniform Parasite of Borlasia.* The occurrence of this parasite was observed in several species, together with certain other parasitic ova in gelatinous mucus, which occupied the alimentary tract of the worms. Pseudo- navicellae were also mentioned. Various notes were further communicated in the author's Reports to the British .Vssociation.'
Professor Ket'crstein in IbGS made known the singular fact that, in one of the Enopla from St. Malo, he had found the anterior generative sacs filled with spermatozoa, and the j)osterior with ova ; thus establishing the occurrence of hermaphroditism in this formerly dioecious group.* A F. Marion, the following year, observed the same fact, also in one of the Fnopla — from deep water oil' Marseilles.' This species had four eyes, each furnished with lenses ; and it differed from that described by Kcferstein fmther in not having the male and female organs arranged in separate parts of the body.
In the same year, a paper on the reproduction of lost parts in the Nemerteans was com- municated by the author to the Liunean Society.^ In this it was shown that each of the fragments into which JJtieus sarii^uiiieus breaks becomes a perfect animal. Allusion was also made to the curious manifestation of acidity presented by the majority of the Nemerteans, and a few exceptions noted in a paper on the boring of the Annelids.*
> ' Proceed. Zool. Soc.,' Feb. 13, 1866.
^ " Ou the Young St.iges of a few Amielids," ' Ann. Lvce. Nat. Hist. N. York/ vol. viii, June, 1866; and ' Ann. Nat. Hist./ 3rd ser., vol. xix, p. 208.
' 'Ann des so. nat.,' ser. 2, xviii, p. 288. 1848.
* ' Jouru. ^Micros. Sc.,' vol. xv, u. s.. Trans., p. 38, pi. ii. April, 1867.
5 'Kept. Brit. Assoc.,' 1867, p. 92; and ' Kept. Brit. Assoc.,' 1868, p. 3-10.
« ' Archiv fiir Naturges.,' 1868, p. 102, taf. 3, f. 1 and 2 ; and 'Ann. Nat. Hist.,' ser. -1, vol. i, p. 229.
7 'Ann. Nat. Hist.,' ser. 4, vol. iv, p. 136.
8 'Proceed. Linn. See.,' Zool., vol. x, pp. 251 — 253, tab. 7. " ' Ann. Nat. Hist.,' ser. 4, vol. ii, p. 293.
HISTORY OF THE SUBJECT. 41
In 1SG9 a memoir was published by the author on the anatomy of the British Ncmerteaiis (comnuuiicatcd to tlic Royal Society, I'dinburgli, in April, ISOS), in whieji many facts were recorded, it is believed, for tlie first time.' Their minute structure, from the skin to the pro- boscis, was described, the chief varieties indicated, and observations on the development of a few species appended. In this year also the outlines of a classification, founded on anatomical data, were brought under the notice of the same socicty.-
Exccllent researches, by Dr. Elias ^letschnikofi", on the development of the Ncmcrtean PijVi- diiim, from the deposition of the ovum from whieli the latter is evolved onwards, have recently appeared.' His observations were made on tlic ova of an cIon^atL d, whitish example of the Anopla at ^lessina, and on a species of PijUdiam from Odessa ; and his paper is illustrated by finely executed steel engravings. The chief details will be found xmder the head of the development of the Anopla, and therefore need not be further alluded to at present. In his summary many suggestive comparisons are drawn between the development of the Nemertean Tylidium and the well-known phases in the growth of the Tapeworms.
The veteran naturalist, Professor E. Grube, in his most interesting brochure,^ recently pub- lished, on the marine fauna of St. Vaast-la-Honguc, refers to certain common Nemcrteans found there. He observes that his boatman stated that the head of Linens innrinus was luminous, but this he did not personally witness. He also notices a blood-red flat worm, Proceros scint/iiinolenfus, Qfg., with cephalic furrows.
A few notes on the Nemerteans are appended to a paper by Professor Ehlcrs " On the Vermes collected in the Sea of Spitzbergen." ' Three new species are described from spirit- preparations, but tliis is a somewhat unsatisfactory mode of examination, unless careful accounts are kept of tlie animals in life.
' ' Trans. Eoy. See. Edinb.,' vol. xxv, ii, pp. 305 — 106, pis. iv — xiv. - ' Proceed. Roy. Soc. Ediub.,' vol. vi, pp. 545 — 548.
■* ' ;Mem. dc I'Acad. Imp. dcs Sc. de St. Pctersbourg,' vii° s cr., torn, xiv, no. 8, 18G9. •* 'Mittheilungpu ubcr St. Yaast-la-IIouguc u. s. IMeeres-, bcsouders s. Auuelidenfauna.' ■' 'Aun. Xat. Hist.,' 4tli ser., vol. viii, p. 60. Transl. from the 'Sitzungsb. der pbrs.-medic. Soc. zu Erlangen.,' June ~, 1S71.
42
ANATOMY AND I'll VSIOLOGY.
Fig. 1.
ANATOMY AND PHYSIOLOGY.' General Conception, or Archetype of a Neviertean.
AKCHETYPE OF A XEMERTEA:s'. Fig. 1. In its ordinary condition. Fio. 2. In transverse section.
a. Proboscis. ao. Aperture in snout for proboscis. d. Cutis en masse. e and e. Muscular coat* of tbe body- wall, f. SuiKTior commissure. g. Inferior commissure. h. Ganglia. j. Digestive chamber. n. Lateral nerves. o. Muscular sheath for proboscis. od. Proboscidian chamber containing corpnsdes. p. Dorsal blood- vessel r. Lateral blood-vessels. or. Ovaries. x. Muscular ribbons.
1 A description of the anatomy of the group was published by the author in the ' Transactions of the Royal Society of Edinburgh' (vol. xxv) ; but so many additions, both in text and drawings, were necessaryj that this could not be allowed to stand. Accordingly the whole has been rearranged.
ANATOMY OF THE ENOPLA. 43
Thk essential character or archetype of a Ncmertcan may be thus described: — A soft vermi- form l)o(ly, covered with cilia, and furnished with a thick t^landular cutis, beneath which the body-wall is composed of several strong, specially disixjsed muscular layers. Tlirougli the centre of the body-cavity (and entirely beneath tlic nerve-commissures in front) passes the digestive canal, wliicli has two well marked divisions, an oral ajierture anteriorly, and an anal posteriorly, and is richly ciliated throughout. The nervous system consists of two conspicuous cephalic ganglia, united by a double commissiu'e, and giving off posteriorly a large lateral nerve-trunk, which passes backwards on each side to the tail. The circulatory system is composed of a series of closed contractile vessels. Along the median line of the dorsum lies a special muscular sheath, containing a complicated proboscis, and a highly organized corpuscular fluid, both the sheath and the proboscis passing between the commissures of the ganglia in front. The sexual organs are in the form of sacs, placed between the muscular wall of the body and the digestive canal.
I. — Anatomy of the Enopla. 1. Cutaneous System.
Tlie body of every example of the order is rmiversally covered with cilia, the motion of which may be very well observed in some of the larger forms by placing them in good light under a lens. The proboscidian aperture, the mouth, and the tij) of the tail, arc generally furnished with longer cilia. The ciliary motion is most active in the cephalic furrows of this group.
\\\ Amphiporus lacfijtoreus the skin is somewhat opnqnc, and presents a cellular, or cellulo- granular apj)earance (Plate X, fig. (i), the entire field being definitely covered with glandular cells, and the reddish pigment, when present, grouped in irregular granular masses. I have not been able to demonstrate the cuticle as a separate structure, on account of the softness and delicacy of the tissues. On removing a portion of skin from a living specimen, and ])lacing it under moderate pressure, it presents the aspect of a series of ovate or spatludate cells (Plate X, fig. o), which contain soft and minutely granular contents, interspersed with large, clear masses of mucous or gelatinous matter, having a similar figure, the latter becoming more abundant as the pressure increases. There are also numerous pigment- and other gramiles scattered over the field. Changes, however, rapidly ensue under pressure, and the contents of the cuticular spaces or areohc pass rapidly to the nearest free border, and there accumulate as mucous ami granular circular masses (Plate X, fig. 7 a, li). A transparent gelatinous basis-substance, having a reticulated aspect, remains after the extrusion of the foregoing elements from the skin.
"When a transverse section is made of the integument, after hardening in spirit and mounting in chloride of calcium, the ajipearance (Plate X, fig. 4) is as follows : — In rapidly prepared and newly fitted specimens, a structureless nuicous fihn is sometimes observed to separate from the exterior of the skin, as indicated by the double outline at the edge of the figure. Chloride of calcium dissolves this ; and it has not been seen in those hardened in chromic acid. This is not an cpidenn, l)ut only an exudation of transparent nuicus, and it is also oliscrvcd in the living animal under pressure. The areolar cutis {a) is now much altered, and streaked perpendicularly, an appear- ance due to the collapsed condition of the spaces, the contents of which to a greater or less degree
44 AXATOMY OF THE EXOrLA.
have escaped, ami tlnis grcatci' pioiniiicnce is given to the hyaline interceliuhir substance. It is granular tlirouglioiit, especially towards the outer and inner edges. In many transverse sections, ])rcssiirc of the thin glass cover causes a change in each of the preparations, so that the more cclhdar appearance of tlic outer edge is partly due to the fact that the texture is seen from with- out, aiuhiot laterally. Towards the inner edge, the skin in this state sometimes assumes a crenate aspect, and adjoins a pale and structureless basis-layer (i), which separates it from the suljjacent muscular walls of the i)ody. In longitudinal sections of the textures, particularly in those much hardened, or slightly exposed to air, spurious annulations are caused by the folding inwards or wrinkling of the skin (Plate XVI, fig. 2) ; but such crenations do not affect the muscular layers, and iiave no connection with the diverticula of the digestive chamber, or, as supposed by some of the older authors, with true annuli. A thin longitudinal section from the surface of the integu- ment shows a scries of meshes with crenated edges, the size of the spaces being variable. In JVemcrfcs Ncesii and N. (gracilis, the cells or areolae of the skin arc smaller than in ,7. lactijlorcun ; the former having nuich dark pigment in its cutaneous textures dorsally ; and the surface in N. gracilis sometimes presenting the appearance of microscopic mosaic work, from the beauty and fineness of its areola;. In a young specimen, a])parently of Amphiporus speciabili«^ transverse section demonstrates that while most of the longitudinal pigment-belts on the dorsum are in the cutaneous tissues outside the circular (external) muscular layer, two very well-marked stripes lie quite within both the latter and the longitudinal muscular coat. They are placed on each side of the arch of the proboscidian sheath, and doubtless are the cause of the daiker appearance which characterizes the median bands when viewed from the dorsum. Similarly, in l^etrasiemmu Roheiiiana; the rows of pigment, constituting the two brown stripes on the dorsum, are at the inner border of the cutis — touching the circular muscular coat ; while the median white stripe is placed within the longitudinal layer, exactly over the proboscidian canal. The reddish- brown pigment in the Zctlandic variety of Tctraalemma Candida is also chiefly developed towards the inner margin of the cutis. Much brownish colouring matter is produced in the skin of the pale Amphiporidae after prolonged confinement, and thus fresh examples from the rocks are always necessary for the more minute investigations. This is well marked in Prosorltocfniiits, where the pigment-cells and granules form a kiiul of meshwork by the looping of the rows.
The chief function of this elaborate glandular arrangement is, no doubt, the secretion of the abundant mucus, so characteristic of these animals, and ^\\\c\\ is often of a most tenacious descrip- tion. I have seen a specimen of A. lactifloretis rapidly form an investment by this means, when placed in a vessel containing a little sand ; and whether the sand-particles simply adhered to the gelatinous mucus by accident or otherwise, the animal took full advantage of the protection. The silky sheaths of Tetrastemmct dorsalis are also examples of this cutaneous secretion. The same habit of tube-forming is extensively followed by the Amphiporidae of our southern shores, apparently to protect themselves from the increased danger of desiccation. On placing a living specimen on a glass slip, and causing it to emit some mucus, the secretion proves to be a minutely granular fluid, intermingled with a few larger corpuscles ; and it is produced by the entire surface of the skin, both in this grou[) and in the Planariae, not by any special portion thereof, as supposed by ^Ir. Darwin in the latter animals. One of the densest tubes is formed by JVemerfes carcinoj)hiIa, KoUiker, (Plate VI, fig. 5, and more highly magnified in fig. 6), and this has an
^ This specimcu was kindly scut, with other forms, by ilrs. Ceilings, of Sark.
MUSCLES OF THE BODY-AVALL. 45
areolar aspcrt, from tlic distribution of tlic granules or glolmles at intervals on llie surface. ^Moreover, wiien viewed in profile, these globules arc found to be elevated above the f^;;neral sur- face, liki" a scries of low pale warts. The tniies are attached to the hairs of the abdominal feet of female crabs {Cnrciiiiis nimiias) bearing; ova, and arc evidently of intrinsic importance to the species, bolii as a protection against injury and desiccation. The very great change which ensues in tiie appearance of preparations deprived of the cutieular layer shows how important this is in giving character to the group. An interesting feature in regard to the skin of the Enopla (in c(Jmmon with the Anopla), is the reaction which ensues on testing with litmus-paper. An acid indication occurs in Amphiporus lacfifloreus, Tdrastemma melanocephala, and Ncmerlen gracUit!:, amongst others, while a reaction not less distinctly alkaline is found in jhnpliijjorux pulcher and Nemertes Necsii.
In regard to the c'hcmical composition of the tubes secreted by these animals it may be remarked that Professor IL Grubc submitted those of Cerelratulus crasswi IVom Cherso to Dr. Lothar .Meyer, who pronounced them to be formed of a substance closely allied to chitine. Tubes made by various British species are not much affected by strong acetic acid, and become pulpy only by prolonged action of Liquor potassce.
The description of the tegnmentary structures given by M. de Quatrefagcs differs materially from that just noted, a discrepancy arising [)artly from his confoiuiding the structure of the Enopla with the Aiu:)pla, and partly from incorrect observations. His separation of the skin into two layers, the exterior composed of smaller, the interior of larger cells, is not evident in AiDpliiporus. Snudler cells sometimes do occur towards the ciliated surface, but the entire integument jjroper is continuous as a single layer. The only representative of his " fibrous" coat, which is described as lying within the former, is the structureless basement-layer. Max Schultze figures a small portion of the skin of his Tt'{ra.slei)imnobscurum,s\\o\\mgi\ series of large cells under the epidermis, with a few granular bodies interspersed, but the view is diagrammatic.
2. Muscular Structure of Ihe Bod/j-wali.
A very distinct belt of circular muscular fibres (Plate X, fig. 4, c), as in the Oligochaeta, occurs under the basement-layer of the cutis. The fibres arc compact throughout, and less bulky than the next coat, with which their filaments do not mix. The succeeding layer (</) forms a powerful investment of longitudinal muscular fibres, and, in transverse section, is generally somewhat crenaled on the inner border, and fasciculated throughout. The inter- fascicular substance is transparent and structureless, and evidently as mobile and contractile as the fibres themselves. Numerous fibrous bands stretch fiom the inner surface in connection with the various contents of the body. In common with the Anopla, the nniscular tissue is furnished with a delicate yet complete sarcolemma. Thus there arc only two distinct muscular coats of non-striated fibres around the body of the Enopla, making an essential diflerence in this resj)ect between them and the .Vnojila, to which (latter) previous observers have for the most part confined their investigations. It will I)e observed, moreover, that in the general order of their muscular layers the Enopla agree with the Oligoclu'eta.
Anteriorly the body-wall terminates in a rounded snout of the usual cutaneous textures, pre- senting in transverse section (Plate X, fig. 1) an areolar and granular appearance, the soft
46 ANATOMY OF THE ENOPLA.
contents of the areolae Imvinff for the most part escaped. The aperture for the proI)()Scis perforates the tissues just at the veiitnil border of the tip. A reniarkaljle interlacement of Mbrcs, occupying almost the entire cephalic region, occurs in front of the ganglia (Plate X, fig. 3). Powerful bands (1) pass below both tlie buccal cavity and the tube for the proboscis, meet, and cross each other in an oblique manner, making afterwards, liy their diverfrence, extensive lateral con- nections ; indeed, it will be observed that towards the inner muscular layer the fibres just mentioned form a broad fan-shaped arrangement. Some (2) pass upwards by the side of the central canal, and mingle with those descending from this region, while others (-3) curve downwards to the ventral wall. Those (4) meeting al)ove the central canal intersect each other obliquely in the middle line, so as to constitute a firm arch ; and, besides, there are some transverse fibres (5) which cross over the canal and spread out laterally. Another series (0) shnits downwards and inwards on each side of the cavity, and forms a firm junction inferiorly. The arrangement of these bands and fibres is so intricate, that each seems to blend with the other, imd make a continuous anastomosis of contractile meshes. In addition to these obliciue and radiating tii)res, a powerful longitudinal scries is interwoven with them in a complex manner, besides the denser grouping (e) at the margin (which indicates the inner muscular coal of the body), and the glandular masses in the centre. It will be observed that the bands wiiicli pass ])ciieatli tiie central canal are the most powerful, and offer a much greater resistance to the bulging of the jjroboscis and its sheath than the superior fii)res, so that in extrusion the organ is mainly directed upwards (Plate X, fig. S). The inferior commissure of the ganglia is thus some- what protected by the arrangement of the fibres in front of it. The blood-vessel (Plate X, figs. 3 and 9, /) lies on each side in a sheltered angle between two series of fibres ; and its ealilirc would not seem to be much interfered with except in extreme protrusion of the proboscis, though this is not of much consequence in the economy of these worms. All the oblitjue or transverse fibres are connected with the body-wall and the inner muscular layer, as are also the longitudinal at the tip of the snout. This elaborate interlacement provides in the best possible manner for the varied changes which the region undergoes during protrusion and retraction of the proboscis, and the ordinary motions of a tactile and mobile, yet not too yielding snout. The ai-rangement of the oblique and circular fibres around the longitudinal layer of the central canal must also act the part of a constrictor, and adapt the cavity to its ever-varying calibre. On the whole, the stroma in this group, from the greater predominance of cellular and gramdar elements, is less dense than in LiiicKS, and the interlacement of the fibres, though not more complex, is more beautiful, because possessing greater distinctness and regularity.
The posterior end of the body does not present this intricate arrangement, but the muscular fibres blend together and close in the cavity, with the exception of the small and sometimes indis- tinct ojjening of the great digestive chamber. The modes of fracture of these mnseidar coats in certain of the Ainphiporida; in a sick and perishing condition are interesting, the animal being separated into a number of beads, from the constriction and rupture of the body-wall at somewhat regidar intervals.
In specimens of Amphijwrns puIcJier from which the cutaneous textures have been removed by improper preservation, the muscidar coating has a glistening aspect, and is marked by a con- spicuous double row of genital pores along each side. This glistening appearance of the muscular layer on removal of the cutaneous tissues is also seen in certain Planarise.
]\I. de Quatrefages described the muscular coats both in Borlasia and Xemertes (especially
PROBOSCIDIAN CHAMBER. 47
iiistniicinn; Ncuiortcs bdlniva, our N. //racilis), as consisting of " external longitudinal and internal triuisverse" libres. In the I^nopla, as just mentioned, it is cxaetly the reverse, the cireular iil^rcs being external, and the longitudinal internal. He also represented another layer, within the internal, as forming an aponeurosis, apparently referring to the iibrous prolongations from the internal or longitudinal coat. Physiologically, it is certainly a better arrangement for an animal possessing only two muscular coats, to have the longitudinal fibres internal, for, on the occur- rence of rupture, they, as well as the otlier tissues, are clasped by the circular; whereas, in the supposed arrangement of M. de (Juatrefages, the longitudinal are beyond the reach of the constricting belt. Other organs also in the same animal, such as the proboscidian sheath and long posterior gland, have their circular fibres exterior to the longitudinal.
The actions of this muscular system are very varied, and include swimming or floating on the surface of the water, an action performed, as in the Nudibranchiate moUusks, by aid of the mucous exudation, and not, as stated by iM. de Quatrefages, chiefly by the cilia.
3. Proboscidian Sheath or Chamber.
In the Enopla this chamber originates just in front of the ganglionic commissures, and continues without interruption nearly to the posterior end of the worm. It is reco"-nised in the living animal under the lens, or even with the naked eye, as that forming a pale dorsal streak, and containing a transparent thud. The commencement of the cliaml)er is constituted by a fold (Plate XV, fig. 4, a) from the tube of the proboscis becoming attached to the parenchyma of the head, or, in other words, instead of a canal {ab) simply hollowed out in the cephalic tissues, free and distinct walls to the proboscis become apparent at this point. The reflection is the anterior boundary of the proboscidian chamber under ordinary circumstances, and it is against the obstruction so formed that the wave of proboscidian fluid first impinges in the evolution of the proboscis. The cavity gradually increases in diameter, and again diminishes towards the posterior end, where it terminates in a distinct cul-de-sac, a short distance in front of the tail. Its general appearance varies much (Plate XV, fig. 3, and Plate X, fig. 10), according to the position, degree of extension or contraction of the animal, sometimes almost clasping the elongated proboscis, at others havin" its attenuated walls stretched over the doubled organ.
The various transverse sections of the worms also render the relations of the cavitv more apparent. Like the proboscis, its anterior end passes through the ring formed by the arch of the superior commissure, the inferior commissure and the sides of the ganglia. The nervous matter must thus occasionally be very much stretched, or else the proboscis is rarely launched out. This will Ije more particularly noticed in the description of the ganglia, and a reference to Plate X, fig. b, will sulllee for the present. The inferior commissure separates it entirely from the ciliated oesophagus (Plate XI, fig. I). In structure the wall of the chamber is distinctly muscular, as evinced by its ever- varying condition. The fibres, however, are much less powerful at its commencement (Plate XI, fig. 1, o) than they afterwards become (Plate XI, fig. -l, o). Externally it is furnished with a layer of circular, and internally with a series of longitiulinal muscular fibres, both again becoming thinner posteriorly. The comparatively large size of the chamber during life has probably caused several observers to err, by confounding it with the supi)osed general cavity of the l)ody. This may readily be understood by examining a
48 ANATOMY OF THE ENOl'LA.
transverse section {e.y., Plate X, fig. 10) of an animal wliicli lias l)ecn preserved with a tlistcnded clianiijcr ; then, indeed, it seems to be tiie cliief cavity of the body. The presence of tlic reproductive elements also has a considerable influence in modifying the size of the space, which in llic rij)e animal is pressed upwards and towards the median line, while in the spawned worm it expands freely in all directions. It is a mistake, however, to suppose, with M. dc Quatre- fagi's, that no chamber exists posteriorly in the ripe animal, for it holds the same anatomical relations from the ganglia to the tail as at other seasons, only its calibre is encroached on poste- riorly, and the consequent distention by the proboscis and fluid makes it more conspicuous in front. Tlic chamber is not continued throughout the body in long species, such as Nemerles Necnii and X. f/racilis, and is absent in the aberrant K. carcinophila.
Ill the foregoing cavity the proboscis floats in a clear fluid, apparently first noticed by Pallas, rich in JMigc flattened corpuscles, which possess n minutely granular appearance. In the living animal these generally have a fusiform outline, from a slight enlargement in the middle (Plate X, iig. 15, i). They arc also accoinpaiiied by certain globules and granules. The corpuscles vary in size, and frecjuently adhere together in a dying animal, from the very coagulable nature of the transparent fluid in which they float ; and occasionally flbrinous shreds may be obsened attached to them under the same circumstances. The fluid, indeed, is highly organized, and very diflerent from sea-water, to which Dr. T. Williams compares it. When the proboscis has been gently j)rotruded under chloroform, the corpuscles in the interspace may by-and-by be seen grouping together, so as to form stellate bodies resembling miniature Solasters, spiked bodies like tlioriiapplcs, flattened structures with pectinate ends, and various other forms. In Telrademma iiielanocep/iala the corpuscles are comparatively small, some being clear, spindle-shaped bodies, others granular and rounded. The enormous increase of cells and granular masses in the pro- boscidian fluid, after the rejection of a proboscis, is well seen in this species. In other Tetrastemmce the corpuscles (Plate X, fig. 14), though similar in shape to those of A. lacHjloreiis, are comparatively large ; and in a variety of T.favida, which I am inclined to regard as the Polia mm/uiriibra of ^I. de Quafrcfages, they are tinged pinkish or reddish by transmitted light (Plate X, fig. 11). All arc not similarly tinted, some being pale, otiicrs yellowish, while many are bright red, the colour in each case being in the nucleus. Globular bodies and granules are present, a.s ill Ampliiporus. The skin of this specimen contained many minute reddish pigment-specks, so that to the naked eye it had a delicate salmon-pink appearance. Reddish granular masses occa- sionally occur in the proboscidian chamber oi A. lactiforeiis, and in various species of Tetrastemma, generally associated with reddish specks in the skin,' and it is curious that a rejected proboscis assumes the same hue by transmitted light. After extrusion into the water, the shape of the cor- puscles soon alters, and they adhere together and become translucent.
Amongst the authors who have alluded to the proboscidian chamber, Delle Chiaje and Grube seem to have possessed a fair knowledge of its arrangement and structure. CErsted, again, gives a small figure of a transverse section of his Nolospennus flaccidus, and characterizes the cavity as " caiialis in quo penis est," indicating by a blank beneath what is evidently the digestive tract. He thus did not advance the physiology of the parts further than Hiischke, who called the pro- boscis a male organ, and the nerves semen-canals. His interpretation of structures, however, is more distinct in his section explanatory of the Family Amphiporiua, in which the digestive cavity • 111 the rcddisL-brown Zetlandic variety of T. Candida the proboscidian chamber contains many brownish-red pigment-masses.
PROBOSCIDIAN CHAMBER. 49
is correct])- ullmlcd to. The reflection of the wall of the proboscis l>cforc-mcntione(l, in front of the ganglionic conimissurcs, is the only harrier (and a very effectual one) that separates the probos- cidian chamber from the tissues of the head. In no species has such a cephalic diaphragm as represented by M. de Quatrefages been found; but the ciliated oesophagus, to be described hereafter, takes its place, and leads one to infer that the distinguished naturalist has misinterpreted the structure. Besides, the head is not a hollow organ, re(piiring such definition from the other parts of the body. The same author, while explaining a transverse section oi Nemertes Borlmii, shows a canal surrounding the proboscis; but in liis description he confounds it with the general cavity of the body, and figures the proboscis occupying the centre of the latter posteriorly. This account, no doubt, refers to one of the Anopla, but he states that the same arrangement occurs in the Ami)hiporidae, and represents in a Polia a series of transverse fibres as forming a platform {plancher) at the anterior and ui)|)er portion of the general cavity of the body, indicating its presence in his figures by a dark shading. No such arrangement of transverse fibres has been seen by me, but the characteristic ciliated cesophageal chamber occupies this situation. The somewhat erroneous views he entertained with respect to the relations of the corpuscular fluid of the proboscidian chamber may be understood by a glance at one of his figures, which depicts in Polia sanguirubra the proboscidian bodies floating in what he terms the genital cavity, and in which the genital caeca are supposed to lie. I cannot corroborate his state- ment that these corpuscles become much more numerous at the epoch of reproductive activity. The diminished size of the chamber may cause them to crow'd anteriorly, but this is not an increase. Dr. Johnston likewise confounded the proper sheath for the proboscis with the general cavity of the body ; and Dr. Williams, who styled the canal the oesophageal intestine, stated that it opened externally on the side of the body not far from the head, after the manner of the Sipunculidtc. M. van Beneden alludes to the sheath in VoUa obscura, and compares the fluid and corpuscles to pale blood. Prof. Keferstein does not describe the chamber with sufficient clearness, and mentions that the proboscidian corpuscles are placed in the general cavity of the body.
The structure of the special corpuscles, and the highly organized condition of the trans- parent licpiid in which they float, point them out as being, in all proliability, concerned in nutrition, as first mentioned by M. de Quatrefages, though he likewise associated generation there- with. Some very interesting questions, however, are raised by their entire absence in Nemertes carci/iopliila, especially to those who, like the late Dr. Williams, think the fluid analogous to the peritoneal or perivisceral fluid in the true Annelids, a fluid, we may remark, which Professor Hu.\ley considers the true blood, while he imagines the red fluid in the branching vessels analogous to the water-vascular system in the Annidoida. If in Nemertes carcinopkUa the proboscidian fluid had been more important in nutrition than that in the vessels, it certainly would not have given way to the latter. It is to be remembered, too, that this absence coincides with the atro|)hied condition of the proboscis itself and all its apparatus. It cannot be affirmed, also, of the Nemerteans, that the fluid in the so-called blood-vessels is devoid of corpuscles, for they occur in several species. Again, I think there can be no doubt the fluid and corpuscles exercise a very important influence on the reproduction of the proboscis, a process hereafter to be described, as well as promote the absorption of the debris of the discarded organ when it happens to be included in the chamber. But, while thus affirming that the fluid has a certain influence on, and bears a certain relation to, the development of the proboscis, it cannot be said to be indispensable to the presence of the latter, since there is a small proboscis in Nemertes
7
50 ANATOMY OF THE EXOPLA.
carcinopliila, wlicre the fluid is altogetlicr absent. In Nemcrles t/racilis and N. Neesii the proboscidian cliamber gives way to the Itlood-vcsscls posteriorly, the latter, therefore, being the more iiii])r)rtant structures. The views of Dr. Thomas Williams in regard to the corpuscular li(jui(l, wliicli lie termed the " chylaqueous fluid," are so much at variance with accuracy, that I cannot pass them over in silence. He remarks that " in the case of the Borlasiadae, I'lanariadae, and Liniadie, the chylaqueous fluid is contained in the digestive caeca and diverticula. In some of the Pliuiariaduj, however, I have proved that a space does actually exist between the digestive diverticula and the solid structure of the body, which is lined by a vibralile epithelium, and into which j)robably the external water is in some way admitted. ]?y this water, thus situated, the contents of the digestive CKca are aerated. The fluid oscillating in these ca-cal appendages of the stomach is thickly charged with corpuscles, whicli, from their regular character, prove this fluid to have already reached a high standard of organization. They occur as elliptical cells in the Borlasia from which the illustration (fig. 25) was taken ; the fluid abounded also in small orbicular points, constituting the ' molecular basis ' of the digestive product. In this worm it is this thud, and not the true blood, that is aerated ; the latter system is too little developed."' This quotation clearly shows that lie was quite unaware the so-called " elliptical cells " are always confined within the proboscidian sheath ; as well as points out the erroneous notion he entertained of the true digestive tract, which in all cases can readily admit salt water (by mouth or anus), if such be required, but certainly not for the purpose of converting it into " a vHal organized fluid." The proboscidian liipiid and corpuscles, as I have previously shown, are very far removed from sea-water, and hence have little analogy with the "chylaqueous fluid" so frequently mentioned by investigators of the Invertebrates.
4. The Aperture for the Extrusion of the Proboscis.
This orifice is situated towards the ventral edge of the tip of the snout, and under favourable circumstances in the living animal, may be seen as a terminal pore, surrounded by a closely set series of radiating lines ; as, for instance, when the snout is bent upwards towards the tube of the microscoi)e (Plate X, fig. 16). The aperture has been called a genital pore by not a few authors, e. y. (Erstcd, Leuckart, and Quoy and Gaimard ; while others, such as Johnston, De Quatref;iges, Busch, '\\'illiams, and Girard, have interpreted it to be the mouth ; indeed, since the proboscis was by many considered the alimentary organ, it could not be otherwise. It is furnished with longer cilia from an early period ; and in the adult these (cilia) form, when the lips are slightly pouting, a very pretty arrangement (Plate XV, fig. 4, a c), similar to the analogous opening in Linens (Plate XIX, fig. 1). The striated ring surrounding this passage in transverse sections of the tip of the snout (Plate X, fig. 1) indicates the special muscular coat pertaining thereto. The canal (Plate XV, fig. 4, ab) proceeds straight backwards from the aperture to a point in front of the commissures of the ganglia, where it meets the differentiated walls of the proboscis (at a) ; and the cilia can be traced to this region, but no further. The tube is simply hollowed out in the tissues of the head, and is quite independent of the motions of the proboscis. It has a series of longitudinal muscular
1 ' Philos. Trans.,' part ii, 185:2, p. 63r, pi. sxxii, f. 25.
PROBOSCIS. 51
fihres beneath tlic ciliated imicoiis surface, and tlic strong oblifjiic and einiilar bands (Plate X, tig. 1) form a very efficient investment. \\\\vn the proboscis is al)oui to be ejected, it commences to fold over, like the turning of a finger of a glove inside out, at the point (Plate XV, fig. 4, a) in front of the ganglionic commissures, a fact wliicli has escaped most observers. In withdrawal also, it may be noticed tiiat, towards the conclusion of the process, the hust wrinkle of the proboscis glides within the terminal aperture, and slowly passes backwards till this point is reached, when it ceases, and the organ is once more in its ordinary condition, any change that afterwards ensues being due to tlic stretching of the shortened tube — a process of simple elongation. Thus the anterior portion structurally and functionally differs from the succeeding, the wall of the proboscis always intervening between it and the proboscidian fluid.
The attenuated coats of the proboscis curve outwards all round, and become fixed to the wall of the foregoing canal and other cephalic tissues just in front of the ganglia; the reflection constituting the poi/ii d'ujjpui against which the wave of proboscidian fluid impinges, when the organ is about to be extruded. The thin anterior wall of the ])roboscis unrolls, the terminal pouch is distended by fluid, and then the organ is rapidly launched forth. To judge from the descriptions and drawings of jM. de Quatrefages, the entire force of this liquid would be thrown against the posterior part of the nerve-ganglia, and the straitened border of his hypo- thetical " diaphragm" would not pass further forward. In my specimens, the waves of the proboscidian fluid debouch readily into the yielding anterior canal in front of the commissures, and then externally into the loop of the extruded proboscis. I have never seen the very pretty lozenge-shaped arrangement of muscular bands in the snout, as figured by ]M. de Quatrefages, and whose function, he states, is to dilate the " oral" orifice, and carry the " gullet" forward ; but the elaborate stroma, shown in Plate X, fig. 3, would amply suffice for this. During the motions of the proboscis, the reflection in front of the ganglia assumes various postures, and it fretpiently does stretch obliquely forward and outward from the tube, especially when that is drawn backwards. On the other hand, when the tube is thrust forward, the fibres slope forward and inward.
5. PROBOSCIS.
I shall divide, for convenience in description, the proboscis of the Enopla into three regions, viz., the anterior, middle, and posterior. The first (Plate XV, fig. 3, a) comprehends the some- what cylindrical portion between the reflection in front of the ganglionic commissures and the commencement of the stylet-region ; the second (b) includes the stylet-region and the well-marked swelling of the great muscular reservoir ; and the third (c) is represented by the long posterior chamber.
A. Jnierior Bet/ion of (he Proboscis.
From the point of reflection backwards, the proboscis gradually increases in diameter until its full size is attained (Plate XIV, fig. 1, and Plate XV, fig. 3), and then it remains nearly cylindrical
52 ANATOMY OF THE ENOPLA.
as far as the stylet-region. The entire organ is proportionally larger than in Lineus, and its anatomy moic apparent ; though I very much doubt, even in this group, if we can assign it the ideal office of a vertdiral column. At tlie point of reflection there is sometimes a kind of OS (Plate XV, fig. 4, a), from the slight folding of the lips of the organ in the early stage of ejection. The muscular fibres arc chiefly longitudinal at the commencement, and if in a partially protruded proboscis a section be made in front of the ganglia (Plate X, fig. 9), the difference between this and the succeeding reticulated portion is very conspicuous. Occasionally the organ assumes a twisted position under examination, so as to give the fibres a spiral appear- ance (Plate XVI, fig. 1, a), and in such a state the structure might fancifully be likened to the spiral arrangement of the muscular fibres in the oesophagus of certain of the higher animals ; but this condition of the proboscis is purely accidental. I fear, however, it has led M. de Quatrefages into an erroneous interpretation of the anatomy of the organ in Polia ylaucn, the [)roboscis of which is described and figured as having regular spiral belts at its commencement. The same autiior again avers that in Polia mulabilis the latter portion consists of two longitudinal muscular coats scjjarafed from each other by a cellular layer, a provision, he explains, for cnal)ling each to act indejjcndently. lie also adds that no circular fibres were seen in this species, in P. filuin and some others. Dr. Johnston, on the other hand, considered the organ to be homogeneous.
In very small specimens of the British examples the transparency of the tissues of the proboscis renders definition of the coats somewhat obscure, especially after mounting in chloride of calcium ; but, so far as I have observed, the structure is as follows : — Externally is a layer of clastic tissue (Plate XI, figs. 4, and 9, g), which is more distinctly striated in transverse than in longi- tudinal sections. Towards its free border, also, certain obscure granular markings observed in the latter sections (Plate XI, figs. 7 and 8, g) show that the course of the external fibres is diU'ercnt from the others ; indeed, in sonie views, the appearance is such as to rai-^^e the suspicion of the presence of the ends of a few fine muscidar fibres, the rest being nearly homogeneous. The next layer is a somewhat narrow belt of longitudinal muscular fibres (/), which may be termed the external JongUndinal miiscnhir coat. It consists of pale, unstriped, muscular fibres. Between this and the other longitudinal layer is a remarkable stratum, the reticulated coat (e), which in transverse sections (Plate XI, fig. 4) assumes a regularly moniliform appearance, from an increase of its constituent substance at certain points. In many longitudinal sections {e.g. Plate XI, fig. 8) the ends of numerous fibres are found in this layer, as if it was composed of circular fibres ; but the appearance is due to intermediate bands which pass between the thicker longitudinal columns. If a thin longitudinal slice from the organ in Amphiporu>i pulcher is hardened and mounted in chloride of calcium, numerous well-marked homogeneous longitudinal belts are seen at regular intervals, and between them are manj- connecting transverse fibres. The ends of the fibres in these sections have therefore been caused by the knife severing the latter series. Thus the tube is surrounded by a complete investment of this elastic meshwork, which, doubtless, has an important physiological bearing on the varied movements of the organ. In the AmpJiiporm grcenlandicus of Oersted, the longitudinal belts of this layer arc somewhat rounded in transvei-se section. The succeeding stratum [d) consists of a powerful series of longitudinal fibres, fully twice as thick as the external longitudinal layer, and which may be termed the {tiner longitudinal muscular coat. In essential structure it resembles the exterior, difiering only in bulk. In sections prepared by hardening in alcohol,
rilOBOSCIS. 53
tlicsc fihrcs, ill coiniiioii with otlicrs in tlic organ, i)rcscnt a coarser appearance in transverse section than after hardening in eliroinic acid. The fiftli layer from without inwards is a strong band of circular fibres (c), the circular muscular coat, which forms a counterpoise to the pre- ceding. Within is a hasemcnl-lai/or {li) of pale translucent texture, best seen in longitudinal sections (Plate XI, fig. S), for in transverse cuts the coat is apt to be confounded with the inner layer of circular fibres. It lias, on the whole, a homogeneous appearance. Upon this layer rest the peculiar glandular papilla^, wliich arise from a distinct margin on its inner edge (Plate XI, figs. S and 0, h). In the ordinary transverse sections of tiic proboscis these organs form en masse a somewhat foliated or frilled arrangement, often of a very symnu'trical appearance. In contracted specimens the entire cavity is filled up by them and their translucent gelatinous mucus. The largest villi or glandular processes (Plate XI, fig. 10) arc situated some dis- tance in front of the stylets, for towards this region they become smaller, and finally the fundus is clothed only by minute papilte. Sometimes they present a coarsely fringed appear- ance, with large granules in their interior; and when the tube has been turned inside out thev have a villose aspect, the tough mucus adverted to above projecting in filaments from their surface under the slightest pressure. I have generally observed, also, towards the first portion of the protruded organ, fine motionless processes like cilia jutting from the apices of the glands, and they are probably homologous with the minute spikes which occur on those of the posterior region after rupture from pressure. I do not think, at all events, that they can be called urticating organs. In Tetraslcunna the glandular papilla; arc leaf-shaped, and somewhat crenated at the border, where there is a regular moniliform appearance from the arrangement of the globules (Plate X, figs. 19 and ;20). Under pressure, they are granular internally, and fur- nished with numerous globular or wedge-shaped mucous masses that refract the light like oil. The same type of structure is found in the proboscides of Ampluiuiiid;c from New Zealand, only the longitudinal bands of the reticulated layer are more numerous than in A. lactiforeus.
The description just given of the structure of this region differs much from that of M. de Quatrefages, almost the only author who has entered into the minute anatomy of the proboscis in the Enopla. He states, like Mr. H. Goodsir, that externally the tube is supplied with a series of transverse muscular bridles, which maintain it in position within the body of the wonn, and he shows a section of the parts in Nemerfcs hahnca, which bears out his description very well ; but he did not observe that, if such bridles existed, they would have to pass through the muscular sheath in which the organ glides, before reaching the body-wall of the animal. His minute anatomy of the proboscis is chiefly taken from the examination of Borlasia ancjVxc, and hence cannot apply in any degree to the Enopla, though lie considered it the type of both. He makes only two muscular layers in the wall of this organ, niul though in his section from B. anglim he indicates " traces de fibres transversales," by a few lines crossing these longitudinal coats, he distinctly observes that they arc not a])parent in the smaller species. The longitudinal fibres are separated, he states, by a transparent homogeneous tissue, which forms a great number of bridles of very elastic fleshy columns, making, in other words, an elastic cellular layer ; and he figures this in the before-mentioned section, adding that this lax cellular arrangement will give the two longitudinal muscular coats that independence of action necessary for the proper performance of their functions. It can only be supposed that he refers to the reticulated layer by this descrip- tion. He mentions a transparent homogeneous coat within his longitudinal muscular layer, cor- responding to the mucous coat of the higher animals, and adds that the papillffi of the latter are
54 ANATOMY OF THE EXOPLA.
all covered with vibratilc cilia. M. de Quatrefages thus describes only four coats, viz., mucous, internal longitudinal, elastic cellular, and external longitudinal ; and if the stays or bridles which he notes as connecting the tube to the body-wall be taken into account, it may be surmised that the muscular sheath for the proboscis is included in his reckoning. No cilia occur in this organ.
B. Middle liegion of Proboscis.
The elongated chamber just described terminates posteriorly in a sort of cul-de-sac, into which three small apertures converge ; one at each side from the marginal stylet-sac, and a centnd (at a, Phitc XII, fig. 1), in the pit of the cavity, connected with the reservoir. The walls of the proboscis undergo a considerable change in this division, especially with regard to the deeper layers. Externally the investing coat from the anterior region is continued on the commencement of the reservoir (Plate XIII, fig. 10), and has a crenatcd border in the contracted state of the parts, wilh transverse markings or rugae ; but this appearance docs not of necessity indicate the presence of circular fibres, for the contraction of the longitudinal layer underneath would cause even a very feebly elastic coat to assume similar markings. The thin subjacent layer of longitudinal fibres is likewise continued to a similar extent on the reservoir, and assists in connecting the divisions. These two layers lie exterior to the stylet-sacs.
The structure of the pit or termination of the anterior chamber (>), Plate XII, fig. 2) requires special notice. The large glandular papilla; of the inner wall gradually diminish in size, as before- mentioned, until the floor is covered only by small, densely arranged and minutely granidar processes, giving the surface, which in the ordinary state of the parts bends backwards all round the stylet in the manner shown in the figure, a smoother appearance. The fibres also become firmly bound together, so as to constitute a s|)hincter for the aperture, and gently curving out- wards and backwards, are lost in the obscurity of the parts caused by the external circlet of glands, somewhat behind the anterior termination of the wedge-shaped investment of the apparatus at the base of the stylet. This floor of the chamber is composed of a series of muscular fibres, whose direction, in the ordinary state of the parts as a transparent living object, is outwards and backwards, but which assume various aspects during the motions of the organ. Thus the floor passes from the conical form with the apex directed backwards to that of a transverse platform ; and in the everted condition has the shape of a cone the apex of which is directed forward (Plate XIII, fig. 14). In the latter position the secure binding of the fibres which surround the central aper- ture just permits the stylet to project, and no more. The whole arrangement constitutes a large muscular pit with very powerful and mobile walls, capable of many and varied alterations of form. In firm contraction of the region the floor of the chamber is pouted forward (Plate XIII, fig. 7), causing a radiated appearance of the fibres, which thus slant outwards and backwards from the central point. A firm constriction of the tube often takes place at the anterior border of the stylet-region, separating the pit of the organ from the more villose or glandular portion in front, and making a double swelling of the parts. Immediately before the marginal stylet-sacs lie some coarsely granular glands, which, however, are less conspicuous than in X. gracilis and others. Prof. Keferstein speaks of this region as having only a longitudinal muscular coat (though the crenated border of the anterior chamber is continued thereon in his figure), and as
PROBOSCIS. 55
possessing much pigmentary and gr:iiiular matter. The latter is not well-marked in A. lactijloreus or Telrasfcmma, since the entire apparatus is cither translucent or white ; but in certain species, as will hereafter be shown, an increase in tlie granular sulistance occtirs. Tlic longitudinal fibres of the last-mentioned author end at the posterior border of the stylet-region.
'I'iiis di\ ision is of tlie same glassy translucency as the reservoir, while both the anterior region and the long posterior are of an opaque-white in the fresh specimen. Externally it has the investing layer (Plate XII, figs. 1 and 2,y) carried from the anterior chamber, and which passes back to the next region. Beneath is a series of very powerful and conspicuous longitudinal muscular fibres (/), apparently to some extent continuous with the most developed longitudinal layer of the preceding region, but few of which pass on to the next. Internally the oblique fibres stretching backwards from the floor of the anterior chaml)er form the band >; (Plate XII, figs. 1 and ~). The rest mingle with the radiating fibres from the central investment. In transverse sections of the anterior part of the region, in the line of the marginal stylet-sacs (Plate XVI, fig. 4), the centre is occupied by the basal granular api)aratus, which is generally thrust forward in spirit-preparations, surrounded by its special investments and a belt of circular fibres. The greater part of the region without is occupied by a dense series of radiating fibres, which form the spokes of the wheel, while the ends of numerous longitudinal fibres fill up the spaces between them. If the section is close behind the floor of the anterior chamber, some of the circular fibres which close in the cavity, and other parts of the proper wall of that division are included, while if the cut is a little further back, the granular glands come in the plane of section. The exterior of the region in all cases is occupied by the elastic and longi- tudinal layers. The alternation of radiating or oblique with longitudinal or nearly longitudinal fibres continues to the posterior end of the investments of the basal apparatus, the only change towards the posterior part being the introduction of the ejaculatory duct, and a few circular fibres to its exterior. The pale region behind the basal apparatus has a very complex structure, consisting of densely interwoven fibres that surround the wall of the ejaculatory duct, those towards the cir- cumference showing an arrangement similar to the anterior portion of the region, viz., having the (cut) ends of fibres in the axils of the radiating sei'ies. In longitudinal sections of the organ these interlaced fibres are chiefly transverse in direction ; and in some preparations there are numerous grannies at the sides, within the somewhat well-defined border formed by the fibres curving backwards (at >;, Plate XII, fig. 2), and which corresponds to the lateral arches of the cavity in A. pulcher. The stylet-region proper is distinctly separated at its posterior border from the reservoir by a pale boundary-line under pressure, so that the parts have a somewhat jointed appearance.
a. The Marginal Slylet-Sacs.
These organs (v, Plate XII, fig. 2) occupy the exterior (covered oidy by the clastic coat and the external longitudinal fibres) of the somewhat solid wall of the section immediately succeeding the anterior region, and often cause a distinct swelling under examination. They are conspicuous by their aqueous translucency, as well as by the nail-shaped stylets in their interior, though the exact position of their long axes is rather diflicult to determine. In ordinary views, when the animal is examined as a transparent object under pressure, their long diameter is antero-
66 ANATOMY OF THE EXOPLA.
posterior, or slightly oblique ; but in the prepared specimen tiiis is often transverse (Plate XI, fig. 5). Each sac is ovoid in outline, lias a thin, transparent, contractile investment (sufficiently tough to prevent the points of the stylets piercing it during the motions of the worm), which lies directly under the su|)(,rficial layers of the division, and a duct passing from its central region to communicate with the pit of the anterior chandjer of the proboscis. The direction of the duct in the position above mentioned {i.e., viewed as a transparent object) is forward and inward, but, like oilier structures pertaining to this variable organ, it is liable to many alterations, and is occasionally nuich stretched and attenuated. It is also slightly narrowed on approaching the sac (Plate XIII, fig. 11, a), and lias at its junction therewith a series of protecting fibres. De Quatrcfages and Max Schultze do not notice the duct at all, and Claparede's figure shows it distorted from pressure in 'rclra-ilemiiia, but Keferstein's rci)resentation is more accurate. Each sac contains a variable number of the characteristic nail-shaped stylets (/3), from three to five — more or less — in difi'erent stages of development, as well as certain clear fluid vesicles (£), globules and granules, and is cpiitc filled by a transparent liquid. The stylets very much resemble a lath-nail of cast-iron, and are formed of a translucent calcareous secretion ; indeed they aj)pcar like spikes of the purest crystal. The head is bulged, rounded at the edges, and somewhat flattened at the toj), an elongated conical spike with a sharp point proceeding there- from. The perfect spike or spikes in these sacs are usually about the size of the central stylet, and there are often three or four that can scarcely be distinguished from each other. Besides the perfect organs, there arc some with heads not fully developed, but complete in other resijccts ; the remainder again present the form of simple spikes of various lengths devoid of any head. In a few instances the centre or axis both of the head and point of the stylet is granular, while the superficial portion is of the usual homogeneous aspect. They seem to be formed by gradual increase of layer upon layer of the calcareous glassy secretion, as is well shown in some specimens mounted in chloride of calcium, which have assumed a stratified, or laminated appearance. Sometimes a process (Plate X, fig. 18), probably the remains of a globule, passes from the head a short dis- tance over the base of the spike, as indicated by Max Schultze in Tetrastemma, though seldom to such an extent in the complete stylet. The knob on the head of the stylet figured by this author must be rare, and probably represents a casual globule. The stylets are dissolved in weak acetic acid, as first noted by M. de Quatrefages, and are roughened or corroded by a strong solution of caustic potash.
In a large animal [A. lacllforeiis) an interesting arrangement of the stylet-sacs occurred on one side, for there were two of nearly equal size (Plate XII, fig. 1), connected with each other at one end, so that an interchange of fluid and granular contents took place. Only one had a duct of communication with the anterior chamber of the proboscis. The opposite side was furnished with a single sac of the usual formation, containing two large and perfect stylets, and a shorter without a head. On the abnormal side the outer sac (in this view) had two well-formed stylets, a larger and a smaller clear globule, besides some other minute globides and granules; the inner, which possessed the duct of communication, had one stylet as large as the preceding, and fully formed ; another somewhat less, but also having a head ; a third slender spike of greater length than the latter, but headless ; and a fourth, rather more than half the length of the last-mentioned. No globule existed in the inner sac. It is interesting to notice the different degrees of perfection of these spikes in relation to what Dr. Max Schultze avers as to their development, viz., that they are the products of the smaller contained vesicles. In the one there were two large globules, and two
PKOBOSCIS. 57
perfect stylets, yet no trace of a developing spike; in tiie oilier tlicrc were tlirce completely formed stylets, yet each varied in length ; while the long sj)ike without a head was fully as long as the largest in that sac — head included. Those in the outer cavity were quite as large as the central stylet. In Tel rant cmma caiuUila I have observed, besides the ordinary stylets, a group of minute ciystalline spines, which had no connection with the clear vesicle of the sac. Thus, at present, though I have very often seen these organs inside, and connected with the fluid vesicles, I cannot altogether support Max Schultze's notion that they must be developed therein ; and this would not signify much, since the entire cavity must act as a secreting chamber, else the large ones could receive no increase after they had outgrown the capacities of the globules. M. Claparede stated, in his ' Rechcrchcs,' that he luul never seen spikes inside those vesicles, but in his subsequent ' Beobachtungen' he figured a developing stylet in a globule in Prosorhochmus ClaparecUi.
In a specimen that had often been under the microscope, I found on one occasion a pair of stylets, apparently from the marginal sac of one side (though this is by no means certain), advanced nearly to the ganglionic portion of the probo.scis. One marginal pouch was at any rate empty, while the other retained its three stylets. The free stylets moved very slowly forward, scarcely any progress being made during an hour's observation. At this time the empty sac contained numerous granules, but no circular or ovoid vesicle. Twenty-four hours after the stylets had disappeared. The sac is now observed to be much less than its fellow of the opposite side, and somewhat shrivelled and undefined ; but it contains a small ovoid vesicle, which is traversed by a minute slender spike, whose long diameter exceeds that of the globule, and therefore it cannot be supposed to be within it. In addition there is a free spike, about a third the length of the former. The larger has assumed the shape of a stylet without a head ; the latter is as yet nearly cylindrical (Plate XII, fig. 3). Whatever the function of these organs in the marginal sacs maybe, there can be no doubt they have nothing to do with the supply of the central apparatus, for that furnishes its own stylet.
b. Ejaculatory Duct.
Through the same region the ejaculatory duct (/() passes to the point where it opens into the muscular space behind the constrictor of the central aperture in the floor of the anterior chamber. The opening (/u') of the duct is generally obscured by the apparatus of the central stylet, unless the observer sees it at the moment of contraction of the powerful muscular walls of the reservoir, when the mucous or villous lining is driven forward so as to render the channel more apparent, and