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VOYAGE OF HM Ss. CHALEENGER

ZOOLOGY-—VOL. XIX.

ON THE

SCREEN PIEErG “RESULTS

OF THE

VOYAGE OF H.M.S. CHALLENGER

DURING PES YOR Sat 87 3-7 6

UNDER THE COMMAND OF
Captain GEORGE S. NARES, R.N., F.R.S.

AND THE LATE

Captain FRANK TOURLE THOMSON, R.N.

PREPARED UNDER THE SUPERINTENDENCE OF

THE LATE

Sie Ca WY VILL Es LE OMS Oe Kents AE: RaSeattcs

REGIUS PROFESSOR OF NATURAL HISTORY IN THE UNIVERSITY OF EDINBURGH
DIRECTOR OF THE CIVILIAN SCIENTIFIC STAFF ON BOARD

AND NOW OF

JOHN MURRAY

ONE OF THE NATURALISTS OF THE EXPEDITION

ZooLOGY—VOL. XIX.

Published bp Order of ber Majesty's Government

PRINTED FOR HER MAJESTY’S STATIONERY OFFICE
AND SOLD BY
LONDON :—EYRE & SPOTTISWOODE, EAST HARDING STREET, FETTER LANE
EDINBURGH :—ADAM & CHARLES BLACK
DUBLIN :—HODGES, FIGGIS, & CO.

1887

Price Twenty-five Shillings.

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FOR HER MAJESTY’S STATIONERY OFFICE.

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CONTENTS.

I.—Report on the Nemertea collected by H.M.S. CHaLLencer during the years
1873-1876.

By Dr. A. A. W. Husrecut, LL.D., C.M.Z.S., Professor of Zoology in the
University of Utrecht.

(The Manuscript was received in Instalments between 12th October and
18th November 1886.)
I1.—Report on the Cumacga collected by H.M.S. CHAaLLenGcEr during the years
1873-1876.
By Professor G. O. Sars, of the University of Christiania.
(The Manuscript was received in Instalments between 11th October and
15th December 1886.)
I1J.—Report on the PHyLiocaripa collected by H.M.S. CHALLENGER during the years
1873-1876.
By Professor G. O. Sars, of the University of Christiania.
(The Manuscript was received 15th January 1887.)
.—Report on the PTERopopa collected by H.M.S. CHaLLencer during the years
IV.—R the P llected by H.M.S. C luring the y
1873-1876.—First Part.

By Pav PEtseneEr, D.Sc. (Brussels).

(The Manuscript was received 15th November 1886.)

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EDITORIAL NOTES.

Tuts Volume contains Parts LIV., LV., LVI., and LVIII. of the Zoological
Series of Reports on the Scientific Results of the Expedition.

Part LIV.—On the return of the Expedition the specimens of NEMERTEA,
along with the Annetpa, were placed in the hands of Professor W. C. M‘Intosh,
F.R.S., for description. In the year 1884, however, Professor M‘Intosh’s
time being fully occupied with the Annetipa, Professor A. A. W. Hubrecht,
of the University of Utrecht, was requested to undertake the investigation and
description of the Nemertea, and the results of his labours are presented in

this interesting and valuable Report.

Parts LV. and LVI. are respectively Reports on the Cumacra and
Paytiocaripa, by Professor G. O. Sars, of the University of Christiania, who
has already contributed a most excellent Memoir on the Scuizopopa collected
by the Expedition, which forms Part XXIX. of the Zoological Series of
Reports.

Part LVIII.—This Memoir, which is the first instalment of the Report on
the Preroropa, by Dr. Paul Pelseneer of Brussels, treats of the Gymnosomata,
and embraces a critical examination of all the genera and species of this
little known order of pelagic aimals. The Report will be completed by
subsequent Parts dealing with the Tuucosomara and with the Anatomy of

the whole class.

JouNn Murray.

CHALLENGER Orrice, 32 QuEEN STREET,
Epinsurau, 9th February 1887.

THE

VOYAGE OF H.M.8. CHALLENGER.

ZO OMOGY:

REPORT on the Newertea collected by H.M.S8. Challenger during the
Years 1873-76. By Dr. A. A. W. Huprecut, LL.D., C.M.ZS.,
Professor of Zoology and Comparative Anatomy in the University
of Utrecht.

IN PROD UC LON:

Ir was in September 1884 that the collection of the Challenger Nemertea was handed
over to me for investigation, on the express condition that the whole of the MS. and
plates were to be ready within fifteen months.

I mention this, not only with a view of finding an excuse for omissions and curtailings
which cannot fail to have been occasioned in this Report by its rather rapid elaboration,
but at the same time in order to be able at the earliest moment to express my thanks to
Professor W. C. M‘Intosh of St. Andrews, in whose hands the Nemertea were placed on
the return of the Expedition, for his suggestion that the working up of this group should
be entrusted to me, his own time being fully occupied with the description of the Annelida
of the Expedition.

He moreover placed at my disposal such notes as he had already found occasion to
make upon the contents of the collection, some of them referring to species which he
recognised as new to science. When in the following Report these notes are made use
of, such passages will be specially indicated.

The material, as it was put into my hands, was contained in about thirty small bottles,
and was without exception preserved in spirit. It looked far from promising from a

(ZOOL, CHALL, EXP.—PART LIV.—1886.) Hhh 1
th

2 THE VOYAGE OF H.M.S. CHALLENGER.

systematist’s point of view. Hardly any traces of coloration were visible, no external
appendages distinguished the different species, no definite shape, marked out by hard
portions of the integument, which facilitate the recognition of representatives of so many
other divisions of the animal kingdom, were anywhere noticeable.

The majority of the specimens in the collection were cylindrical or flattened fragments,
generally truncated, and rarely so intact that it was possible at first sight to distinguish
between head and tail. The cephalic slits of those specimens which belong to the group
of the Schizonemertea, and the mouths of many of the fragments, were the only external
marks that could serve both for the discernment of what was posterior and anterior,
and for a rough and provisional arrangement of the forms as they were probably related
to each other.

The various figures on PI. I. will give a general impression of the appearance of the
fragments just alluded to. I more especially insist upon the poor aspect presented by
the preserved material of the Nemertea in order to impress the reader with the fallacy
of pronouncing an unfavourable judgment on a collection of marine invertebrates by
relying merely upon the external appearance of the specimens. For I can hardly
sufficiently emphasise the exceedingly good state of preservation of the large majority
of the Challenger Nemertea. They were, indeed, in so perfect a state that the
internal anatomy of all the fragments could be determined, and in very many cases
delicate histological details could be revealed with as much facility as if the specimens
had been captured a few days instead of ten years ago. I feel the more called upon to
make this statement, and to express my admiration for the extreme care which the
scientific staff have so evidently given even to unattractive and small-sized fragments,
as it has been occasionally stated (even in certain of these Reports) that the Challenger
material was sometimes unfit for the minute investigation of internal anatomical struc-
tures. So far as the collection of Nemertea is concerned, this statement is absolutely
unfounded.

The study of the fragments and complete worms constituting this collection was only
possible by aid of the microtome. This instrument was very freely made use of, and the
most important improvement to which it has been subjected by Caldwell, whose
automatic microtome was available, has enabled me to go into many more details than
would otherwise have been possible. The total number of sections through different
specimens of the Challenger material which have been prepared in the drawing up of this
Report amounts to 19,560. They were all of them stained with Ranvier’s picrocarmine.

As already mentioned in the Narrative of the Voyage,’ the number of Stations from
which the Challenger obtained Nemertea is more than twenty. It cannot be said that
any of the three large subdivisions of the group is limited to any special region of the
globe, although representatives of the very lowest and most primitive genera of Palzo-

Narr. Chall. Exp., vol. i. pt. ii, p. 831, 1885.

REPORT ON THE NEMERTEA. 3

nemertea are as yet only on record from the Atlantic and the Mediterranean. It is,
however, very probable that these genera (the Carinellidee) are cosmopolitan, and have
as yet only escaped detection because even in the region from which they are known
they count among the rare forms.

I have here only to add that in drawing up the list of the Challenger Nemertea, I
will follow the subdivision into larger groups that was proposed by myself several years
ago (VIL, p. 204),* and will successively treat of the Paleeonemertea, Hoplonemertea, and
Schizonemertea. It may be remarked that in the first named group, which contains the
most primitive and least differentiated representatives, the genera Valencinia and Eupolia
(=Polia) were also provisionally placed. These two may be looked upon as, to a
certain degree, transitional forms. New light has been thrown by the Challenger
material upon at least one of these genera, and it appears advisable to let them stand in
that subdivision, however far they may differ in certain respects from the typical
Paleeonemertea, such as Carella, Carinoma, Carinina, &c., and however strong their |
affinities may be in other respects either to the Schizonemertea or to the Hoplonemertea.

1 The heavy numerals refer to the Bibliography at the end of the Report.

DESCRIPTION OF THE GENERA AND SPECIES.

NEMERTEA.

A. PALZONEMERTEA.
Family CARINELLID4.
Carinina, n. gen.

Closely allied to Carinella, from which it differs in the presence of a distinct
posterior brain lobe, situated with the rest of the brain and nerve-stems in the integu-
ment, outside of the body musculature. A ciliated canal penetrates into this posterior
brain lobe.

Carinina grata, un. sp. (Pl. I. figs. 1-38; Pls. I, IIL, IV.; Pl. VI. figs. 1-3; Pl. XI.
figs. 1, 2).

Two specimens of this new genus and species were obtained in the dredge, both from
considerable depths, and from the same part of the Atlantic Ocean, namely, to the east
of the United States (Stations 45, 47). The bottom is recorded to be blue mud, and
the depth 1240 and 1340 fathoms respectively. This is the greatest depth from which
Nemertea have been brought to light, and it is worthy of notice that this deep-sea form,
which is at the same time the representative of a new and distinct genus, should be
characterised by peculiarities of structure, hereafter to be more fully recorded, which
are diametrically opposite to certain of the most striking features of the pelagic genus
Pelagonemertes and of other forms that generally occur close to the surface. The most
striking of these characters is the exceptionally strong development of muscular tissue
in the body-wall, and coincident with this, the considerable reduction of the inter-
muscular connective tissue, which in the surface forms becomes a gelatinous matrix in
which both the internal organs and the musculature are embedded.

It can hardly be doubted that this opposite line of development is to a large
extent influenced by the much more considerable resistance to be overcome by an animal
that has to move about at so great a depth of water.

Of the external appearance of the fragments of this new species little need be said.

6 THE VOYAGE OF H.M.S. CHALLENGER.

They are reproduced both in the Narrative of the Cruise (vol. 1. pt. i. p. 831) and
on Pl. I. figs. 1-8. There is no trace of longitudinal lateral slits—so characteristic of
the Schizonemertea—but a terminal crescentic groove (marked out by darker pigment and
by more profuse ciliation in one of the two specimens) was present in both. The pro-
boscidian opening could be easily detected in both specimens, the subterminal mouth in

one of them.

Incomplete as was the information that could be gathered from superficial examina-
tion, very interesting data came to light after the two specimens had been transferred to
the microscopic slides. From specimen @, which was dredged at Station 45, a con-
tinuous series of transverse sections was made, whereas specimen b, from Station 47, was
cut transversely along the region behind the brain, nearly horizontally through the
brain and tip of the snout, and longitudinally through that region of the body where
the nephridia are found.

It is very striking that in all these sections the cellular integument is of a consider-
able thickness when compared with the muscular (PI. II.; Pl. XL. figs. 1, 2). In it we
may distinguish several strata successively characterised (Pl. IV. fig. 1) by an accumu-
lation of nuclei, by profuse integumentary gland-cells, &e., which will be more fully
described in another chapter of this Report.

Curiously enough the contents of the deeper glands have a well-marked green
colour in the anterior portion of one of the body fragments of specimen b, whereas
they are brownish-red in the posterior portion, the whole fragment having first been
stained with picrocarmine.

A homogeneous basement-membrane separates the integument from the subjacent
muscles. This membrane is more deeply stained than other portions of the intercellular
substance and thus stands out very clearly.

In the outermost cellular layer, distinct unicellular, flask-shaped glands are present
(PL IV. fig. 1), although they are not so numerous as in many Schizonemertea, These
facts authorise us to look upon the integument of Carinina as similar in all its
essential elements to that of other Nemertea. We will further insist upon this similarity
when describing Hupolia and Cerebratulus.

Before we pass from the integument to the muscular investment of the body we have
to mention the central nervous system, which is found outside the homogeneous basement
layer just referred to. Where the tissue of brain and nerve-stems takes its course in
the deeper layers of the integument, it is directly applied against the subjacent muscles,
the basement-membrane being indistinct if not interrupted beneath these central parts of
the nervous system (PI. IIL. fig. 7).

In addition to the two lateral stems, each transverse section reveals the presence of a
dorso-median thinner nerve-stem, corresponding to what I have formerly termed the
proboscidian sheath-nerve.

REPORT ON THE NEMERTEA. G

There is, moreover, positive evidence as to the presence of a delicate nervous plexus,
situated just outside of the basement membrane already alluded to, and which, judging
from the available fragments, is present throughout the whole length of the animal.
The transverse sections also show that a second nervous plexus may be presumed to be
present just outside the inner layer of circular muscles. The details of this will be
discussed hereafter when considering the nervous system.

Passing forwards along the lateral nerve-stems we find them in every section fixed
to the subjacent muscles by semicircular fibres indicated in figs. 7 and 8 on PI. IIL.
Anteriorly the stems pass insensibly into the brain, which, as a mere thickening of the
lateral stems, has as yet only attained to a very low degree of differentiation. In this
respect the brain much resembles that of Carinella, from which, however, it differs in a
very important point, viz., the presence of a posterior lobe into which penetrates a
ciliated duct ending blindly and communicating with the exterior.

This posterior lobe is situated, as is the anterior one, outside the muscles of the body-
wall (Pl. VI. figs. 1-3), the inner channel is coated by a ciliated epithelium, differing in
texture from the surrounding nerve-cells. The latter, however, can hardly be sharply
distinguished from adjacent cells of a more indifferent character, and belonging to the
lower strata of the integument.

The muscular elements partaking in the formation of the body-wall are kept distinctly
apart from the tissue, which we have described as the integument, by the homogeneous
membrane above mentioned. Below this membrane we find a thin, circular, muscular
layer (Pl. XI. figs. 1,2, 8), then follows the much thicker layer of longitudinal fibres (a),
and finally an inner layer, thinner again, of circular fibres (6). The comparative thickness
of these two latter layers throughout the cesophageal region may be gathered from
Pl. Il. fig. 5. In the two circular layers the fibres appear to be more elosely set than in
the longitudinal. In the outer circular layer the direction of all the fibres is, however, not
perpendicular to the body-axis, a very regular network of other fibres which have their
direction at an angle of 45° both with the longitudinal and the transverse axis, being closely
interwoven with this layer. These are, however, not massive enough to form a distinct
layer by themselves. The homogeneous intercellular substance, which is also present here
between the bundles of muscular fibres, and which stains very distinctly with picro-
carmine, is of course best visible when the bundles are widest apart. Such a portion is
ficured in Pl. III. fig. 6. This intercellular substance is also seen to be again traversed
by radial fibres passing between the two circular layers; nuclei are, moreover, present
both in the intercellular substance and enclosed along with the bundles of fibres.

Within the muscular body-wall are lodged—(1) the proboscis and its sheath; (2) the
intestine ; (3) the blood-spaces; (4) the nephridia; and (5) the generative sacs. The
space not occupied by any of these is entirely filled up by a tissue, which I will call the
gelatinous tissue, and regarding which more ample details will be given in the chapter

8 THE VOYAGE OF H.M.S. CHALLENGER.

dealing with the anatomy of the group. It is wholly continuous, and a body-cavity in
which the above-named organs may be said to float, or to be suspended, is totally absent.

A rapid survey of the peculiarities which these five systems present must complete
this descriptive account of the new genus. The aperture for the proboscis, which is
situated terminally, leads into an anterior cylindrical compartment, which remains passive
when the proboscis is protruded or retracted. It is coated by ciliated cells, and at the
posterior end the anterior insertion of the proboscis into the body musculature takes
place (Pl. II. fig. 8; Pl. III. fig. 5). Although the name is etymologically not wholly
adapted for the purpose, I still am inclined to adopt for this compartment, which is
present in all Nemertea, the name of rhynchodeeum. ‘This name as clearly separates it
from the cavity of the proboscis or its sheath, as that of stomodzum and proctodeeum
distinguishes certain portions of the intestine of other invertebrates from the mid-gut.

The rhynchodseum of Carinina has a great resemblance to that of Carinella, more
especially because of the wide and much distended blood-space which wholly surrounds
it, and in which it is kept in place by numerous strings of tissue starting from the
muscular body-wall and inserting themselves on the muscular investment of the
rhynchodeeum (PI. III. fig. 5; cf TX, pl. i. fig. 2). From the same figure it may be
gathered that the internal cellular coating of the rhynchodeeum is more than one row
of cells thick, and that these cells have a clear and distended aspect, with a comparatively
small nucleus.

The proboscis itself is inserted in a very simple way in the muscular tissue of the
body-wall. The muscular investment of the proboscis curves round at an angle of 90°,
and becomes continuous with the longitudinal muscular layer of the body-wall. The
details of this arrangement may be gathered from PI. III. fig. 5, and it will there also be
seen how the protruded proboscis remains fixed to the body all along this annular point
of attachment. Thence it extends backwards as far as the proboscidian sheath permits,
which, in the forms allied to Carinella, is only the anterior portion of the body. It is
drawn back again by its retractor. How far backwards the proboscidian sheath reaches
in Carinina could not be made out, as I only possessed two small anterior fragments,
in neither of which the proboscidian sheath terminated. The proboscis itself could be
examined with detail in the single specimen which was cut longitudinally. An anterior
and a posterior portion of different textures are exceedingly distinct. They are separated
from each other by a constriction. In the posterior portion the cells are eminently
glandular, high and flask-shaped; in the anterior portion they are less high and appa-
rently less glandular (PI. II. figs. 1, 2). Great differences in aspect, but not in actual
texture, are of course occasioned by the different stages of contraction in which the various
parts of the proboscis happen to be,

The mouth, situated ventrally close to the anterior extremity, was very small in both
specimens. The cellular coating of the cesophagus is very distinct, and the direct

REPORT ON THE NEMERTEA. 9

application of the cesophageal epithelium against the muscular tissue most marked
(Pl. IV. fig. 8), not even a basement membrane separating the two, whereas a suspension
of the intestine by means of the gelatinous tissue is of common occurrence in other
forms. The longitudinal sections prove that further back the intestine does not con-
tinue as a straight tube as it sometimes does in Paleonemertea, but is constricted
(PL. IV. fig. 2), the constrictions and resulting cxeca being, however, much less marked
and prominent than in the Schizonemertea and Hoplonemertea.

Right and left of the intestine are situated the two longitudinal blood-spaces, which
are direct continuations of the blood-spaces already noticed in the head, and which com-
municate with these by passages that are encircled, together with the proboscis and its
sheath, by the annular nerve ring formed out of the right and left halves of the brain
and their superior and inferior commissures.

The arrangement of these spaces has been fully described for Carinella by Oudemans,'
and I may refer to that description, the arrangement being on the whole very much the
same. There is no median dorsal blood-vessel in Carinina, and there is a very distinct:
internal epithelium to the longitudinal blood-spaces, two of which are figured on Pl. LV.
figs. 2, 5, 6.

Transverse vessels of communication are not present in these two forms. I may
perhaps remark that my researches (XIV.) on the development of one of the Schizo-
nemertea have rendered it probable that also in the Paleeonemertea we shall have to
look upon the blood-spaces in the same light as upon the cavity of the proboscidian
sheath, viz., as a direct derivative or continuation of the blastoccele, for which cavities
(in the adult state) I have proposed the name of archiccele.

The nephridia are situated partly in the anterior portion of the blood-spaces, another
portion traversing the muscular body-wall and leading to the exterior.

In the portion of the paired nephridia exclusive of this excretory duct we may
distinguish two distinct parts, one a continuous tube of varying dimensions, formed out
of very regularly arranged cells with large nuclei, but not in any way forming a series of
perforated cells such as are known in the nephridia of both Turbellaria and Discophora.

These cells are distinctly ciliated and figured on PI. IV. figs. 4-6, Ne. The structure
of the second part of the nephridium is not so easily unravelled, and my preparations
of the two specimens do not suffice to reveal all the details. I find it to consist of
a cellular mass of spongy appearance protruding along a certain distance into the blood-
space, here and there giving evidence of a tubuliform structure, no internal funnels being,
however, anywhere recognisable (Pl. IV. figs. 4-6, NV. sp.).

I must here remark that the researches of Oudemans, who described in detail the
arrangement of the nephridia of Carinella and Carinoma,? render it very possible that in

1 Quart. Journ. Mier. Sci., Suppl. volume, 1885.
2 Loc. cit., p. 71, pl. i. figs. 4,55 pl. ili. figs. 56, 57.

(ZOOL. CHALL, EXP.—PART Liv.—1886.) Hhh 2

10 THE VOYAGE OF H.M.S. CHALLENGER.

Carinina internal communications between the biood-spaces and the nephridian channels
exist, communications by which the cavity of the blood-spaces is thus directly connected
with the exterior. As I have, however, remarked, I could not detect the presence of
similar communications in my two specimens.

The aspect of the spongy portion of the nephridium and its connection with the
canalicular portion, as well as of this with the exterior, is represented in Pl. IV.
figs. 1, 2, 4.

As to the generative apparatus of Carina, 1 can only observe that one of the
Challenger specimens is a male, that the fragment contains only two sperm-sacs in its
posterior portion, and that these communicate with the exterior, each by a separate pore.
Whether in Carinina the sperm-sacs are disposed metamerically as in most Nemertea,
or irregularly distributed beneath the dorsal integument as in Carinella, could not be
made out from this specimen.

The general distribution of integumentary and muscular tissue, as well as of the
cavities of the intestine (D), the proboscidian sheath (Ps), and the blood-space (b/) in the
body of Carinina is indicated by the various figures of Pl. I. The proboscis itself is
here indicated by Pr, the rhynchodeeum by a#Pr.

Family EuPoLIIpD&.

Eupolia, n. gen.
Poiia, dele Chiaje.

Integument generally thick in comparison with the body musculature, the two layers
of contractile fibres of the integument never coalescing with the outer larger one of longi-
tudinal body muscles as in certain Cerebratuli. Proboscis and proboscidian sheath thin
and inconspicuous. Brain-lobes compact, posterior lobe long, wedged in between the
superior and inferior ones. Often a commisssure of the longitudinal nerve-stems below
the anus. No longitudinal cephalic slits but transverse grooves as in many Hoplo-
nemerted.

The necessity for creating a new generic name for the species of Palzonemertea |
am now about to discuss is evident from the following considerations. The generic name
Polia, when it was applied by delle Chiaje to a genus of Nemertea which he introduced
into science (Polia delineata heing the typical species of this genus) had already been
preoccupied in Zoology by Ochsenheimer, who in 1826 so designated a genus of
Lepidoptera. This reason alone suffices to reject it henceforth from Nemertean nomen-
clature, and this rejection is also facilitated by the fact that the same generic name has
been used by other naturalists, such as Quatrefages (XXVIIL), Schneider (XXXL), &e.,
for Nemertea widely different from delle Chiaje’s type. It was an error of judgement on

REPORT ON THE NEMERTEA. itil

my own part, when giving my critical revision of Nemertean genera and species (VIL),
to retain the name Pola in that list, although I was aware of its inapplicability according
to the accepted rules of nomenclature. I retain delle Chiaje’s Polia delineata as the
type species for Hupolia.

Eupolia delineata, (delle Chiaje) Hubrecht (PI. VII. figs. 9, 10).

This species, which is very common in the Mediterranean, more especially at Naples,
is represented in the Challenger collection by one fragmentary specimen, captured at St.
Vincent, one of the Cape Verde Islands. The fragments showed no head, but the
characteristic colouring of the specimen by thin brown stripes on a lighter brown back-
ground, was still so distinct in the spirit specimen, that even in the absence of a head, I
do not hesitate to identify this form with the above-mentioned species, especially after com-
paring the sections through the fragments with those through Mediterranean specimens.

In one of the fragments, which is the tail, a terminal commissure between the two
nerve-trunks can be demonstrated; by a curious twisting of the fragment the sections
seem to prove this commissure to lie above the intestine. Such a commissure is
found in other species of Nemertea (e.g. Amphiporus, Drepanophorus), but a close
inspection soon reveals that here, and also in other Hupolix, the posterior commissure is
indeed found below the posterior portion of the intestine instead of above it.

In M‘Intosh’s preliminary notes on the Challenger Nemertea, I find a notice made
of this specimen to the following effect :—‘‘ The specimen is incomplete, neither head nor
tail being present. The body is firm and rounded, measuring about 45 mm. in length
and about 8 mm. in diameter at the wider part anteriorly The body is closely
striated longitudinally, dorsally, and ventrally by alternate white and brownish belts, the
pigment constituting the latter being situated on the inner side of the basement layer of
the cutis, which forms a simple stratum.”

oso sale Vist Vales. 4 ieee

Eupolia geardi, (M‘Intosh) Hubrecht (PI. I. fi
I. fig. 12).

Pee Vitis 45 5s 8.5 el Xs fesiGise Ele:
Kuborlasia giardii, M‘Intosh, in litt.

This new species, which shows interesting peculiarities, is represented by one
specimen, which was cut up into different portions when I first examined it, so that I
can only give a sketch of the head but no figure of the animal 7n toto.

A well-marked peculiarity of this species of Hupolia is its shortness, which even
surpasses that of Hupolia curta from Naples.

The head shows (see Pl. I. figs. 7-9) a faint annular constriction, not contmuous in
the median ventral line. In this constriction the right and left external openings
leading into the posterior brain-lobe are situated. Judging from what we find in other

12 THE VOYAGE OF H.M.5. CHALLENGER.

Eupoliz, I suppose that this constriction is not so marked in the living animal, but that
here, as in the Mediterranean species, two very shallow, strongly ciliated grooves in the
integument, curving laterally round both sides of the head, were present, and that, during
the process of preservation in spirit, the fold just mentioned made its appearance in the
region where normally these transverse grooves are situated,

What immediately distinguishes Kupolia giardii from its congeners is the thickness of
the circular muscular layer in the cesophageal region.

In M‘Intosh’s preliminary MS. notes on the Challenger Nemertea, I find the
following remarks upon this specimen, which he perfectly recognised as a new species
(the specific name giardii is taken from M‘Intosh’s provisional label), without, however,
at that time referring it to delle Chiaje’s Mediterranean genus.

“A comparatively large form, measuring about 40 mm. in length, with a diameter in
its widest part of 6°55 mm. This specimen is colourless, bluntly rounded at each end
and somewhat fusiform in outline.

“The anterior end is almost truncate, with a dimple in the middle, caused by the
proboscidian aperture, and there are traces of a transverse and a vertical groove, thus
forming a cross at the tip of the snout.

“ The latter is separated from the body by a well-marked fold which probably indicates
a furrow, and which on each side does not quite reach the mouth. The mouth occurs on
the ventral surface somewhat behind the foregoing furrow and in the form of a triangular
dimple. A small aperture (anus) is situated at the dorsal margin of the blunt posterior

end. . . . . The small size of the proboscidian sheath is remarkable. It has an
external layer of circular fibres and an inner layer of longitudinal muscular fibres. Both
are thin. It is continued to the posterior third. . . . . In the middle and towards

the posterior third the body-wall presents a decided change from the foregoing—the
alimentary cavity forming a large central space and the solid wall is considerably
diminished in proportion.”

In studying the sections of this species several additional points of interest came to
light. ‘Those concerning the brain-lobes will be discussed in the paragraph treating of
the nervous system in general; the general aspect of the brain as it may be gathered
from a reconstruction of the sections is figured on Pl. V. The outline of the whole of
the lobes and that of the internal fibrous core are here figured side by side in order to
show the relations of the parts and the actual position of the ciliated canal that penetrates
into a separate part of the brain-lobes more clearly. There is a terminal commissure
between the longitudinal nerve-stems below the anus (PI. VII. fig. 8).

The right and left longitudinal nephridial ducts (Pl. VI. fiz. 9, Nep.) communicate
by deferent ductules (PI. VII. fig. 5, Nep.) with the exterior. Of the latter there are
several; in the available transverse series through the head and cesophageal region |
count five to the left and seven to the right, some of these (sections 298-325 left and

REPORT ON THE NEMERTEA. 13

303-308 right, as well as 448-485 left and 450-485 right) being unmistakably opposite.
The duplicity of these deferent ductules, as figured on Pl. VII. fig. 5, is the exception ; it
was only noticed in this one case, all the other ductules being single.

As to the generative ceca I find in this specimen (which is a male) that they are
very full, and that dorsally and ventrally they assume a conspicuously lobed and arbor-
escent appearance.

The integument offers many points of interest which will not be detailed here as they
will be more fully described in the paragraph devoted to it.

Eupolia australis, n. sp. (PI. I. fig. 6; Pl. VIL figs. 1-8, 7).

From M‘Intosh’s notes on this specimen I copy the following :—~

“Another type of a whitish colour, measuring about 19 mm. in length and about
2 mm. in its widest part in front. The body is tapered from the wide anterior region to
the fractured posterior end. It is rounded in front, somewhat flattened towards the pos-
terior region. The head having been retracted forms a short blunt cone projecting from
the folds of the wider nuchal region. No trace of furrows exists, but the mouth seems
to be at the bottom of the transverse dimple at the base ventrally. . . . . The inner
longitudinal (muscular) layer is peculiar, for its fibres are somewhat regularly arranged,
in long, parallel, and cccasionally pennate fasciculi, which in transverse section run
inward from the former coat. There is a slight hiatus in the dorsal middle line above the
proboscidian sheath, . . . . The proboscidian canal is somewhat thin.

The specimen is a male and the sperm-cells form large masses.”

The sections showed that the species was distinct from Hupolia giardii, which comes
from the same locality, as also from the Japanese Hupolia nipponensis, which will be
described below. They furnish the following data which it may be of use to recapitulate,
in order to facilitate identification of the species when it is again captured in the same
waters, and may then be described with its external coloration, of which no indication can
here be given.

The primary difference between every section of Hupolia australis and all the other
species of Hupolia here described is found in its integument. That portion of the integu-
ment which lies outside of the secondary basement membrane, 6 (Pl. VII. figs. 1-3), is
by far the most prominent and the thickest portion, whereas in the other Hupolie it
attains only half or even less of the thickness of the whole integumentary layers that are
found outside the primary basement layer, Bct (Pl. VII. figs. 5, 9). In correspondence
with this the secondary basement membrane is much thinner in these latter species than
it is in Hupolia australis.

The regular distribution of the blood-spaces round the cesophagus, and just behind it,
is such that in addition to the medio-dorsal and the two ventral blood-vessels (br) it

14 . THE VOYAGE OF H.M.S. CHALLENGER.

would appear as if there were two other longitudinal ones, situated right and left of the
proboscidian sheath (Pl. VII. fig. 1). This may perhaps also turn out to be a special
feature of this species.

Certain other peculiarities observed concerning the intestinal system must for the
present be passed over in silence, for want of material to verify them. It may, however,
be added that the nervous plexus and the dorso-median nerve are much less conspicuous
(though present) in Lupolia australis than in Hupolia npponensis, where the plexus is
in some places very thick (Pl. VII. fig. 11).

In this respect Hupolia australis more resembles Hupolia giardii, where the plexus
is not so very prominent, although the dorso-median nerve (PI. VIL. fig. 4) is distinct
though not massive (cf, Pl. XI. fig. 12).

Eupolia nipponensis, n. sp. (PI. I. figs. 4, 5, 10; Pl. VII. figs. 6, 11, 12).

By this name I wish henceforth to designate a species of which fragments, partly
heads, partly posterior body regions, which obviously belonged to different specimens,
were collected by the Challenger in the Japanese waters.

The series of sections reveal enough of common characters to deter one from assigning
the fragments to different species.

The species is characterised by certain features already alluded to in the foregoing
description of Hupolia australis. If it resembles Hupolia giardi in the disposition of
the different layers of its integument, it differs from this species in the absence of the
unusually thick circular muscular layer (Pl. VI. fig. 9) found in the cesophageal region
of the latter species. The deeper layers of the integument are most conspicuously
developed and vacuolated.

That its nervous plexus is more conspicuous than that of the other Hupoliw was
noted before, and I may add that in the available sections a very good horizontal aspect
was obtained of the brain-lobes, which showed these to differ in certain minor but still
easily verifiable pomts from those of Eupolia giardii. The upper lobe appears to be
much more cylindrical; so does the inner fibrous core. There is no superior additional
gyrus to the superior brain-lobe with special fibrous core corresponding to what is
described and figured for Hupolia giardii (Pl. V. figs. 1, 5, 7-9; Pl. VI. fig. 8).

The connection between the posterior brain-lobe carrying the ciliated canal and the
rest of the brain is, however, very intimate; they are soldered together along a very
extensive surface. ;

As to the proboscidian sheath, one of the sections clearly demonstrates how exceed-
ingly thin and delicate it is, and how the separation of its cavity from that of the
blood lacuna is even difficult to observe.

In this as in other species of Huwpolia the distinction in the cesophageal epithelium

REPORT ON THE NEMERTEA. 15

between the layer of ciliated cells immediately surrounding the lumen and the deeper
layer of granular gland-cells is very marked.

There is no muscular layer in the cesophagus as in Hupolia giardi (Pl. VI. fig. 9)
or in Cerebratulus corrugatus (Pl. XIII. fig. 6); the thick layer of glandular cells just
alluded to may here and there show a longitudinal fibre in addition to the radial ones
that serve to suspend it in the circum-cesophageal lacuna ; for the greater part these cells
project freely into this cavity and are bathed by the fluid it contains.

B. HOPLONEMERTEA.

Amongst the Hoplonemertea collected by the Challenger none are so different from
those that are at present known as to necessitate the establishment of a new genus. Still
several of them present certain notable points of interest by which our knowledge of
this order of worms is extended, and which at the same time offer valuable material for
more general speculations.

The three genera Drepanophorus, Amphiporus and Tetrastemma, to which all the
Challenger Hoplonemertea belong (when we except Pelagonemertes) appear to be very
cosmopolitan; the same remark, however, applymg to the Schizonemertean Cere-
bratulus, as will be shown in the sequel.

Family AMPHIPORIDA.
Drepanophorus, Hubrecht.

The mouth and the aperture of the proboscis are separate openings. The exceedingly
muscular proboscidian sheath communicates with lateral spaces that are metamerically
placed, and have thin cellular or membranous walls. The armature of the proboscis
often conforms to an aberrant type.

Drepanophorus rubrostriatus, Hubrecht.

This species, although not represented by complete specimens, was dredged by the
Challenger off St. Vincent, Cape Verde Islands, in July 1873. M‘Intosh identified the
fragments before they came into my hands, and remarks upon them in his preliminary
notes as follows :— .

“Two fragments of a form apparently closely related to Drepanophorus rubrostriatus,
the two measuring about 14 mm. by about 3 mm. in breadth. The colour of the animal
is reddish-brown on the dorsum, with longitudinal pale stripes.

“The ganglia and cephalic sacs are remarkably distinct and fer nerve-cords have a
cellular investment. A very remarkable feature is the presence of large granular tubes
which communicate with the cavity of the proboscis.

16 THE VOYAGE OF H.M.S. CHALLENGER.

“The structure of the proboscidian sheath is peculiar, since the longitudinal fibres are
. i) . OR .
clasped in spaces made of the circular coat and in transverse section the lining is
papillose.”

Not only the remains of the external coloration but also the internal anatomy

\\\\

\ \ WY
XW RX
WY \\ LAN \\\ SSS
\ AN WS NY . SX SQ
NN UI QXSSS
WA AAS
fia, 1.—Armature of the proboscis of an adult Drepanophorus serraticollis. H, curved handle of stylets with muscle-

fibres attached to it; s¢, nail-shaped stylets in action; s¢’, nail-shaped stylets in accessory reservoirs, the number of
these reservoirs more or less corresponding to that of the active stylets, and also increasing with age.

convinced me of the identity of this fragmentary specimen with the Mediterranean
species, which has, moreover, already been found by Langerhans at Madeira. Although

REPORT ON THE NEMERTEA. 17

the Challenger specimen contained no proboscis (which had apparently been expelled), I
cannot refrain from giving a woodcut of the curious and divergent armature of the
proboscis as it was observed by me both in young and in older specimens of Drepano-
phorus from the Mediterranean. In young specimens the number of pointed stylets
and of reserve sacs is less considerable. This proboscidian armature is certainly one of
the most marked and distinctive features of the genus, although, as we shall presently
see, I feel justified in assigning other species to it even when the presence of a similar
armature has not been definitely demonstrated.

The specimen was a female ; the generative products are, however, yet very far from
ripe.

Drepanophorus serraticollis, Hubrecht (Pl. IX. figs. 5, 6; Pl X. fig. 5; Pl. XI.
10s Sin el eX freee leexey aig. 17):
Drepanophorus serraticollis, Hubrecht, Aanteekeningen over Anat. van eenige Nemertinen,
Utrecht, 1874.

Concerning the specimens here referred to this species, I find the following notice in
M‘Intosh’s preliminary MS. :—

“Two specimens were dredged at Station 162 (off East Moncceur Island, Bass Strait),
38-40 fathoms, sand, length about 30 mm., with a diameter of about 7 mm., but both
are broken.

“The ventral surface is marked by a median and two lateral longitudinal grooves.

“Externally the dorsum is tinted of a pale madder-brown without stripes. A darker
patch runs in the centre of the head in front of the cephalic furrows. The under surface
is pale.

“The head is wider than the neck and seems to have been somewhat bluntly conical.
The aperture for the proboscis is slightly inferior. It is marked by a prominent ridge
indicating the cephalic furrows, which slope slightly forward on each side to the middle
line, where they are separated by a short interval. Inferiorly they slope more distinctly
forwards and inwards, and are separated by a wide interval, from which a median ridge
goes forward to the proboscidian aperture. In front of this furrow, both dorsally and
ventrally, there are a series of secondary furrows about thirteen or fourteen in number,
running forward from the main groove. ee

“In regard to the structure of the proboscis it agrees with the others of the genus,
presenting no stylets.

‘“«The proboscidian sheath presents a regularly interwoven or basket-like pattern of
circular and longitudinal fibres, and the inner surface is papillose in transverse section.
No diverticula seem to be present. . . . . Many ova are found partially projecting
through apertures a little external to the nerve-cord and corresponding to the very evident

raised line on the ventral surface.”
(ZOOL. CHALL, EXP.—PART LiIv,—1886.) Hhh 3

18 THE VOYAGE OF H.M.S. CHALLENGER.

It needs no comment that it is at the least rather hazardous to identify with the
Mediterranean species (which seems also to have been examined and figured by Quatre-
fages when he gave the description of his Cerebratulus crassus), a specimen in which the
proboscis, as well as its armature, is absent. Still the transverse sections offer such a very
close resemblance to those of actual specimens of Drepanophorus serraticollis, that it
would be again hazardous to establish a new species for the fragments, of which the colora-
tion affords a less decisive clue than in the case of the foregoing Drepanophorus rubro-
striatus—the madder-brown hue referred to by M‘Intosh being all that is preserved of
the uniform though bright coloration which the specimen must have had when alive, if
it agreed in this respect with the Mediterranean Drepanophorus serraticollis.

I have, moreover, hazarded the identification with the foregoing specimens of a third
fragment collected in the Kerguelen waters, of which not only the proboscis but also the
head was absent. Here, too, the internal characters enabled me to refer the specimen
to the genus Drepanophorus (the transverse ceca of the proboscidian sheath being in
this case the guiding feature).

The systematic position of this specimen thus only rests upon the similarity of the
transverse sections and on the general yellow hue of the fragment, darker on the dorsal
than on the ventral surface.

The very thick-walled proboscidian sheath with its delicate lateral sacs, different in

certain respects from that of a new species of Drepanophorus hereafter to be described, is
figured on Pl. X. fig. 5.

Drepanophorus lankesteri, n. sp. (Pl. I. fig. 22; Pl. IX. figs. 1, 2, 10; Pl. X. figs.
2,45 Pl OX, figs.) 5 PIS XLV: figs: :95 a0 = Sele xeverhi og 3):

Of the three species of Drepanophorus contained in the Challenger collection, this is
without doubt in several respects the most remarkable. One specimen measuring 30
mm. in length and 3} mm. in breadth was obtained; it was dredged at Station 49, in
the waters of Nova Scotia. As to its colour when alive, the spirit specimen allows of
no other certain conclusion than that the dorsal surface is darker than the ventral, which
may have been whitish. No special markings are now traceable on the dorsal integument,
and we may thus surmise that its natural colour, which has been only partly preserved
in spirit, was in life brown or red.

If I nevertheless feel justified in creating it a new species, it is because certain internal
characters are so well marked as to allow of no confusion with the species of Drepano-
phorus hitherto known.

The two characteristic features which immediately attract attention in studying a
series of sections through this species are, first, the presence of a series of transverse
commissures (P], IX. fig. 10) metamerically placed at intervals of about 0:2 to 0°15 mm.,
and connecting the two longitudinal nerve-stems all along their course below the intes-

REPORT ON THE NEMERTEA. 19

tinal ceca. Close to the posterior end of the body I cannot vouch for their presence; their
extreme tenuity, and a folding of the sections, preventing the transverse commissures, if
present, from being seen. Nor could I make out with certainty in the one specimen
available, whether the longitudinal stems themselves coalesce above the anus as they do
in the other Hoplonemertea, but on @ priori grounds, I can hardly doubt their doing so.

Anteriorly, the transverse commissures were present even in the immediate neigh-
bourhood of the brain, up to the point where the so-called vagus nerve branches off and
stretches forwards towards the cesophagus.

Although, on the whole, they have a very regular course, and are situated at equal
intervals, still a few irregularities in these commissures must be noticed ; some of them
branching into two, others being connected with the preceding or the succeeding commis-
sure by a small bundle of nerve-fibres.

The significance of this nervous arrangement will be discussed further on.

The second characteristic to which I wish to draw attention is the presence of trans-
verse czeca belonging to the proboscidian sheath. Although they are present in other
species of Drepanophorus, so that we are justified in looking upon their presence as one of
the typical generic characters, still I never found their walls so markedly developed as in
Drepanophorus lankestert. Generally the walls are exceedingly thin and membranaceous
(e.g., Drepanophorus rubrostriatus); here, however, they attract attention by the thick
cellular coating which immediately reveals its presence both in longitudinal and in trans-
verse sections. On Pl. X. fig. 4, the nature of this arrangement is clearly shown. Another
peculiar feature of these ceeca of the proboscidian sheath is that I have found a few of
them coalescing peripherally with the one preceding or following them by means of a short
longitudinal extension, which allows these few successive ceca to intercommunicate not
only by means of the proboscidian cavity, but also by means of this distal connection.

The muscular body-wall of this, as of most other Hoplonemertea, may be shown to
contain, in addition to the two layers a and B (cf. Pl. XI. fig. 8), certain cross fibres
not forming a definite layer, but arranged at angles of 45°, and visible in sections parallel
to the surface.

The openings of the longitudinal canals of the nephridia to the exterior are situated
. ventrally, posteriorly, and at the same time terminally; this constitutes another difference
as compared with Drepanophorus rubrostriaius which has been already described and
figured by Oudemans.’ On one side of the specimen investigated two openings of the
nephridial duct piercing the integument are at all events observable, although somewhat
more internally, before these deferent ducts have pierced the muscular body-wall, they
coalesce. There is a very close proximity between the anterior nephridial ramifications and
the lateral longitudinal blood-vessels. They do not, however, intercommunicate, nor do,
as was supposed by M‘Intosh, the proboscidian sheath-ceeca and the blood vascular system.

1 Loe. cit., pl. i. fig. 7.

20 THE VOYAGE OF H.M.S. CHALLENGER.

Eyes are present in Drepanophorus lankesteri. In the (detached) posterior lobes of
the brain there is a double canal as in most other Hoplonemertea, the one branch taking
its course along the glandular cells, the other in the ganglionic part of this brain-lobe.

As to the sexual elements, they are in this species enclosed in sacs that are ventrally
situated, and although I have only one specimen at my disposal, which is just beginning
to ripen, I still believe I may lay it down as a rule for the species that the gemital ceca
are arranged in pairs in the vicinity of each nerve-stem, so that four are very often
simultaneously met with in one section. This is, as we will presently see, a more compli-
cated arrangement than that which obtains in the other species of Drepanophorus, but it
is a simplification of the more profuse and less regular distribution of the genital sacs, as
it occurs in Aimphiporus moseleyr.

Amplhiporus, Ehrenberg.

Stylet in the proboscis of the normal shape. Oral and proboscidian aperture con-
fluent. No lateral ceca to the proboscidian sheath. Numerous longitudinal nerves in
the proboscis as in Drepanophorus.

Amphiporus moseleyi, n. sp. (PI. I. figs. 20, 21; Pl. IX. figs. 4, 7-9, 11; Pl. X.
Hoss el eV. tes, Wt l2;, 20):

Professor M‘Intosh has drafted the following notes on a provisional examination of the
specimens before they were handed over to me, which I may here be allowed to insert :—

“A large flattened species, the largest specimens about 68 mm. in length, and about
12 mm. at the broadest part. The body in those best preserved is somewhat flattened
and with an acute edge along both sides of the tip of the tail. Anteriorly the body is
thick and rounded both dorsally and ventrally, but posteriorly it is much flattened. In
the preparation the anterior end is more pointed than the posterior. The ventral surface
throughout is flatter than the dorsal.

“The larger specimens are deprived of much of their cutaneous tissue so that they
are comparatively pallid; in one (the smaller) the dorsum is of a dull blackish-grey ;
while the ventral surface is either whitish or pale greyish. The lip of the snout is pale,
and from this a pale line runs backwards to the tail on each side. This is not altogether
due to pigment, for in those devoid of cutis a very evident whitish band is found along
the anterior third, but it becomes indistinet posteriorly.

“The head is somewhat truneated anteriorly and marked by a series of eyes which
are rather deeply seated. In the large specimens these form a marginal band on each
side along the antero-lateral margin of the snout. In the smaller a series begins on each
side of the median line of the snout and runs in a tolerably straight line backwards to

the slight narrowing of the furrow, while a somewhat triangular area superiorly is covered

REPORT ON THE NEMERTEA. ; Zi

with similar eyes. The posterior boundary especially being so distinct as almost to
make a special row.

‘Behind these a band of similar eyes runs upwards and slightly forwards, a consider-
able interval on the summit of the dorsum separating those of each side.

“The cephalic furrows slope outwards and backwards on each side to the margins
dorsally, and from the latter point are continued ventrally outwards and forwards.

“So far as can be observed in this form only a single aperture exists for the proboscis
and mouth. This forms a well-marked slit in the ventral surface, a little behind the
tipoftHe snout. . . = .

“Th minute structure the proboscis corresponds to that of the typical form
the stylet is simple and normal.”

To this description of the external characters I have nothing to add, but may proceed
to remark that the examination of the internal structure by means of sections has
revealed the significance of the white lateral stripe, noticed by Professor M‘Intosh as not
being due to pigment. It is, indeed, a peculiar feature by which this species is
characterised, and which I have hitherto not observed in other Nemertea. All along the
extent of this lateral and longitudinal whitish line (Pl. IX. fig. 8) the sections show
the presence of numerous glandular (or sensory ?) cavities, opening to the exterior by very
numerous pores piercing the integument, and both accumulated at, and limited to, the
region where the dorsal musculature merges into the ventral (Pl. XV. fig. 11), and where,
as in so many Hoplonemertea, the muscularity of the body-wall is reduced to a minimum,
i.e., in the right and left lateral line. In the posterior portion of the body these organs
were no longer present ; anteriorly, however, they could be traced even in the head (PI. X.
fig. 3, gls.). Further details about their structure will be given in the anatomical part of
this Report.

The other chief peculiarities of the species which are revealed by a study of the
sections, and which must be briefly enumerated in this summarising description, are :—
the situation of the longitudinal nerve-stems, in the portion of the body where the
intestinal cxeca are clearly developed, above these ceca about one-third or halfway
between the lateral margin and the proboscidian sheath. It should be remarked that
this arrangement is the opposite of what is observed in Drepanophorus, where the
longitudinal nerve-stems, as elsewhere described, have their course below the intestine, or
below the lateral ceca. The significance of this different arrangement will be elsewhere
discussed ; in itself it is a feature very much facilitating the discrimination of Amphi-
porus moseleyr from other Amphipori, where the nerve-stems are found much more
strictly laterally, at least in those hitherto known. There is a very distinct commissure
between the longitudinal stems above the anus.

Another most characteristic feature which may generally be distinguished in every
transverse section of the animal, especially when it is ripe for reproduction, is the situation

22, THE VOYAGE OF H.M.S. CHALLENGER.

a hl

of the numerous reproductive receptacles. These are not situated alternately between
each pair of intestinal ceeca right and left, as we find in the majority both of Hoplo-
nemertea and Schizonemertea. In Amphiporus moseleyi, the distribution of the genital
receptacles appears to follow a more primitive arrangement, and offers many points of
similarity with what obtains in the Paleeonemertean Carinella, where there is not yet a
regular metamerical arrangement of the genital sacs, but where there are short independent
cavities, irregularly distributed under the dorsal body-wall, which they pierce \by means
of short ducts. The outer openings of these ducts are seen on the dark dorsal ‘surface of
the animal as so many fine white dots irregularly spread between the transverse aind longi-
tudinal white lines that form such well-defined external markings in the species in question.

Amphiporus moseleyi, as will be seen on comparison of figs. 4 and 7 of Pl. IX.,\has its
generative sacs distributed very much in the same way, with this difference, however,
that generative pores are situated not only on the dorsal but also on the ventral surface
of the animal. When the animal is very ripe and the generative sacs are overfilled, it is
manifest that this specific character may be more easily detected im every transverse
section than in young or unripe specimens. As many as seven separate sacs/in one
section were noticed. Both the male and female sex were found to agree in this respect.

Another character peculiar to nearly all Amphipori—the coalescence of the oral and
the proboscidian aperture into a common wider opening, situated just below the tip of
the snout—is also met with in Amphiporus moseleyi.

Amphiporus marion, n. sp. (Pl. IX. fig. 3; Pl. X. fig. 1; Pl. XV. figs. 14, 15).

A second species of Amphiporus is represented in the Challenger collections by two
specimens, the larger coming from Marion Island, and having been collected on December
26, 1873; the other from Christmas Harbour, Kerguelen, at a depth of 120 fathoms.

The place at which the first specimen was obtained was an inducement to dedicate
this species, in preference to any other of the novelties of the Challenger, to the indefatig-
able naturalist of Marseilles, so well known by his numerous researches in the field of
invertebrate morphology.

Aimphiporus marioni, was one of the larger sized specimens, measuring 54 mm. in
diameter anteriorly in its widest region. The body musculature may be said to be
stronger than in most of the other Hoplonemertea (cf. Pl. IX. figs. 1-6); the longi-
tudinal muscular layer shows a very marked pennate arrangement of the bundles (Pl. X.
fig. 1) between which the gelatinous tissue penetrates, carrying with it massive nerve-
stems which assume a more or less flattened, plexus-like arrangement, just between this
longitudinal layer a and the circular layer B (PI. X. fig. 1, ne). The proboscidian sheath
is also very muscular; the proboscis has the stylet of the normal Amphiporean shape.

The nephridial system is comparatively short and has one pair of deferent ducts

REPORT ON THE NEMERTEA. 23

situated at the posterior extremity; the longitudinal canal is anteriorly very copiously
branched (Pl. X. fig. 1, Nep).

There is a very thick basement membrane (P) to the integument, and very strongly de-
veloped gelatinous tissue (Gt) inside the muscular body-wall. Curious granular enclosures
(inc) occurring in this tissue, both in the head and in the body, will be elsewhere described.

The longitudinal nerve-trunks are not wholly lateral but nearly so; there are no
ventral commissures between them.

The generative caeca assume the ordinary character of paired dorsal receptacles meta-
merically distributed between the intestinal ceca. The generative pores are dorsal and
situated above the nerve-trunks.

The ova, present in both specimens, are in both of them characterised by a curious
refractive body constantly present in addition to the nucleus, and staining deeply

?

with picrocarmine. This “ paranucleus” can be seen to be present at the very earliest
stages of the development of the eggs which came under observation; stages at which
the eggs could still hardly be distinguished from the surrounding cellular elements in

the wall of the generative ceca (PI. XV. figs. 14, 15).

Family TETRASTEMMID &.
Tetrastemma, Ehrenberg.

Eyes four ; arranged so as to indicate a square or oblong. Specimens generally small.

Tetrastemma agricola, Willemoes Suhm.

Of this species, collected by Suhm in Bermuda (Mangrove swamps, Hungry Bay) and
which is the only Land Nemertean procured during the voyage, no specimens have been
preserved, although Suhm tells us that he collected a good many of them. So I must
content myself with reproducing the chief points of its anatomy as they were made out
by him in the Ann. and Mag. Nat. Hist. for June 1874. At the same time I have repro-
duced one of his figures in woodcut. Suhm writes (Joc. cit., p. 409):—

“The largest of these worms have a length of 35 mm. by 2 mm. in width. They are
of a milky-white colour. Their movements are slow and sometimes catterpillar-like ;
they shoot out their long proboscis, fix it at some distant point to which it adheres by
means of its papillee, and draw their body after them. Their skin is filled with rod-like
bodies as described by Max Schultze and others, and is covered on the outside all over
with cilia. In the front we find two pairs of eyes, one of them near the entrance of the
proboscis, the other smaller one further out ; they consist of a fine granulated pigment,
imbedded in a colourless substance, which holds these granules together, in which, how-
ever, a regular lens could not be observed; underneath these eyes is seen the prominent
centre of the nervous system (fig. 1,4); it consists of two lobes and a ring which connects

24 THE VOYAGE OF H.M.S. CHALLENGER.

them and encircles the proboscis. From the lobes depart the two lateral nerves (7) and

some other cephalic nerves, which were not quite clearly visible. . . . . The cephalic
fissures or ciliated sacs. . . . are either very small or wanting entirely. Sometimes

a folding of the skin seemed to indicate their presence ; but in the contractile bodies of
these worms it is very difficult to say whether you have a small cephalic fissure or a
folding of the skin before you.

“Underneath the ganglion, on the under surface, is the semicircular opening of the

mouth (0) leading into an intestinal tube (¢), which runs through the whole length of the
animal, without showing anything particular, and is terminated by an anus (a).
The proboscis is divided into two portions—
the papilligerous part and the glandular part.
At the bottom of the former we find a peculiar
spine . . . . this spine is remarkable
because it differs in form according to the sex
of its owner. In the male it has a rounded
base and is pear-shaped (fig. 2, pr’),* while in
the female the base has sharpened angles (fig.
3, pr’)... I do not think that such sexual
differences have hitherto been observed in
Nemerteans.

“The ovaries and testes are, as usual, situ-
ated between the intestine and the walls of the
bodys som eee Le, establish
for it the specific name of agricola, as
there is probably no described marine species
of Tetrastemma with which it could be
identified.

Fic, 2.—Tetrastemma agricola, Willemoes Suhm, 0, mouth ; “|, however, do not attach much import-
g, brain; m, lateral nerve; 72, intestine; P¢ 1, rhyn-

chodwum ; P¢2, papilliferous; P24, glandular part of ance to this point, as the object of these lines

the proboscis; 3 and ca, region of the stylet and 5 :

reservoir. is only to show that in America also land
Nemerteans exist. Hitherto they were only known from the Pelew Islands, where
Semper has found another, to which he has given the name of Geonemertes palxensis.
I think it is highly probable that land Nemerteans exist to a greater extent in tropical
countries than has hitherto been supposed, and that from their hidden life, and the
impossibility of preserving them, they have hitherto escaped the attention of travelling
naturalists. Especially in such islands as the Bermudas, where the earth of the lower
grounds contains a great deal of salt, it may easily be imagined how marine animals have
taken to terrestrial habits; and it was interesting for me to see that one Tetrastemma

1 These figures referred to by Sukm have not been here reproduced.

REPORT ON. THE NEMERTEA. 25

when put into salt water would live there for twenty-four hours, but when put into fresh
water died after a few hours time. Fresh water, however, poured over the earth which
contained them, did not damage them in the least.”

Tetrastemma fuscum, Willemoes Suhm (nec CArsted).

A second species of Tetrastemma was noticed by Suhm during the first year of the
Challenger cruise. In the paper just referred to, in which he describes Tetrastemma
agricola, it is noticed in the following words:—

“T may here also add that on our cruise from the Bermudas to the Azores I found
parasitical Nemerteans on Nautilograpsus minutus, one of the gulf-weed crabs. They
were small brownish animals, and occupied especially the underside of the crab, under
the abdomen of which I found most of them. They did not exceed the length of 2 mm.
and in none of them could I see genital organs. In fig. 4 I have figured one of these
small parasites, which probably also belong to the genus Tetrastemma, though the second
pair of eyes is only punctiform, situated on both sides of the proboscis. Nervous system
and digestive apparatus do not present anything particular, and the proboscis
(fig. 4, pr", pr”), is remarkable for its shortness.

“T do not think that these worms attain their full size on the crab, but believe them to
be young parasitical stages of some Nemertean which possibly lives on the gulf-weed.”

In his journal, of which an abstract is given in the Narrative of the Cruise, vol. i.
p- 169, Suhm further remarks about this species :—

“The worm presents no modification induced by parasitism ; it appears to be a new
species, and from its colour may be called Tetrastemma fuscum. . . . The ganglia are
especially large and conspicuous. . . . The proboscis is very short, and distinguished
from all other species I know of by having the stylet-sac placed close behind the ganglion
and just above the mouth. . . . Length 0°75 mm., breadth 0°25 mm.”

Suhm was apparently not aware that the specific name which he gives to his specimen
was preoccupied for another Tetrastemma, as early as 1844, by Cirsted for the species
that is now known as Tetrastemma dorsalis.

No specimen being preserved, the special features enumerated by Suhm do not justify
me in proposing a new specific name. For completeness’ sake it was, however, necessary
to mention his observations.

Family PELAGONEMERTID4.
Pelagonemertes, Moseley.
Pelagonemertes rollestoni, Moseley.

It was indeed a novel and startling fact when detailed news’ appeared regarding the
capture by the Challenger naturalists of a pelagic Nemertean, which, in addition to other

1 Ann. and Mag. Nat. Hist., ser. 4, vol. xv. p. 165, 1875 ; vol. xvi. p. 377.
(ZOOL. CHALL. EXP.—PART Liv.—1886.) Hhh 4

26 THE VOYAGE OF H.M.S. CHALLENGER.

characteristic differences, was recognisable by a change in the constitution of its tissues,
similar to that which is noticed in pelagic animals belonging to other groups, when
compared with their non-pelagic allies, viz., the hyaline transparency of the body, with
undiminished, or even with rather increased bulk. The first specimen captured was a
ripe female, the second a very young female. No further specimens were met with. The
first specimen, though somewhat lacerated, was preserved ; the second was observed alive
and figured, but was destroyed. Before mentioning the results which have been obtained
by a careful microtomy of the available specimen, I will here insert in full the interesting
descriptions with which Professor Moseley furnished us as early as 1875,’ soon after
the specimens were captured, and when he had been able to observe them in the fresh state.
His first article? On Pelagonemertes rollestont rans as follows :—

“This remarkable form was found in the trawl, together with a number of deep-sea
animals, from 1800 fathoms, near the southern verge of the South Australian current,
lat. 50° 1’ S., long. 123° 4’ E., March 7, 1874. Its appearance at once pronounced it a
pelagic animal, the body being gelatinous and transparent as in Salpa, with the
exception of the alimentary canal, which stood out in relief, being of a deep burnt-sienna
colour (as is the nucleus in many Salpx), and the region of the sheath of the proboscis,
which was less transparent than the remainder of the body. The animal was living
when obtained, and when placed in fresh sea-water gave evidence of life by a feeble,
regular, peristaltic contraction of the external muscular tunic, which increased on
irritation ; the proboscis was also protruded and retracted several times.

“The animal was about 4 cm. long and 2 broad, and 5 mm. in thickness. Hence its
dimensions, and especially its thickness, render it unfavourable for a perfect examination
of its structure under the microscope whilst in the entire condition. As only one
specimen was procured, and as this was believed to be unique, no dissection was resorted
to, excepting the removal of a small portion of the epidermis and external muscular tunic
for microscopic examination. Hence the investigation of the structure of this Nemertine
necessarily remained an imperfect one, and the affinities of the animal amongst other
Nemertines could not be determined.

“The animal is leaf-like in shape, narrowing to a blunt point at the posterior
extremity, and commencing abruptly at the anterior. The proboscis is protruded from the
summit of a protuberance occupying the middle region of the anterior extremity. The
mouth is situate on the ventral surface of the body, just posterior to the aperture for the
proboscis. It is a simple aperture with a plaited margin composed of five or six folds.
It is the commencement of a short muscular tube, the cesophagus, which was seen to
pass behind the most anterior prolongation of the main mesial digestive canal, but the
communication of which with the latter was not traced. The digestive system stands

1 Ann. and Mag. Nat. Hist., 1875, No. 87 and No, 96.
* The figures which accompanied the article have all been reproduced on PI. I. figs. 24-27.

REPORT ON THE NEMERTEA. ; 27

out very conspicuously in the fresh condition of the animal, from being of the deep
burnt-sienna colour already mentioned. It consists of a broad, flattened mesial canal,
somewhat broadest in the middle region of the body, anteriorly ending in a bluntly
terminated cecal prolongation, and posteriorly narrowing gradually. As the posterior
part of the animal was somewhat injured it could not be determined whether the canal
terminates in an anus or not.

“The mesial canal receives on either side lateral tributaries in pairs, which tributaries
remain simple for some distance of their horizontal course, and then break up into
ramifications. The most anterior pair of lateral canals is split up into by far the most
ramifications. The ramifications become less and less in each pair towards the posterior
extremity of the body, some of the most posterior lateral canals being simply bifureate,
and one merely enlarged at the extremity. There are thirteen pairs of lateral canals
in all.

“The nervous system was plainly seen in part. A pair of rounded ganglia lie on the
ventral and lateral surface of the sheath of the proboscis, being a little posterior in position
to the mouth. A commissure passes above the cesophagus and between it and the
proboscis-sheath. From the ganglia a pair of fine simple nerve-cords pass in a curved
course down to the posterior extremity, where their termination could not be ascertained.

“The cords cross ventrally the lateral digestive canals about the pomt where
ramification commences. Further connections of the ganglia could not be ascertained.

“The specimen obtained was a female. <A series of ovaries, consisting of pear-shaped
masses of minute ova, were present, situate between each of the pairs of lateral digestive
tubes immediately external to the nerve-cord on each side. The masses of cova are
contained in small cavities in the gelatinous internal body-tissue. When pressure was
exerted the ova issued from small corresponding apertures on the ventral surface, and the
small empty cavities remained. The ova were spherical, about °28 mm. in diameter, and
appeared composed of fat-globules and granular matter.

“The proboscis-sheath, which is wide and capacious, is very plainly seen on the dorsal
aspect of the body, and dimly through the thickness of the body from the ventral aspect.
It has a firm muscular attachment at its orifice, and bundles of muscular fibres (apparently
retractor) are attached to it here on either side (pl. xv. fig. B, 1=Pl. I. fig. 24). The
proboscis itself is, when retracted, coiled up in the usual manner within its sheath, as
seen in fig. p(=PI. L. fig. 25). It could, unfortunately, not be ascertained whether the
proboscis is armed or not. It was never entirely retracted, but a small portion of it always
remained exserted.

“The outer surface of the body of the Nemertine is covered with a hyaline, very thin
integument, which is thrown into numerous folds and wrinkles, which are so arranged
along certain lines around small spaces nearly free from them as to produce on the surface
of the body an appearance of a series of small polygonal areas, separated by fine reticular

28 THE VOYAGE OF H.M.S. CHALLENGER.

network (fig. p= fig. 27). This condition of the surface was most conspicuous about the
anterior part of the body, but the body was much lacerated by the meshes of the trawl,
and, therefore, I cannot say whether the whole integument is in this condition in the fresh
state or not. The folds and plaits in the integument are so sharp that they give the
appearance under the microscope of somewhat spindle-shaped bodies with sharply pointed
extremities (fig. c, 1, 2,3=fig. 26). At first I supposed that these bodies were urticating
organs, resembling those of Bipalium, but on carefully teasing up a portion of the integu-
ment with fine needles, and being unable to isolate a single one, I concluded that they
were mere folds. They are, however, of remarkable appearance, from their extreme
abundance and the manner in which they cross each other at all angles. They are well
preserved in glycerine preparations of the skin hardened in picric acid.

“Beneath the integument is some granular glandular matter. Immediately beneath
the integument, and in close adherence to it, is the muscular tunic, evidently the
homologue of the cutaneous muscular system of Bipalium and other Planarians. As in
these, the outermost fibres are circular in direction, the inner longitudinal.

“The muscular tunic encloses the entire body. It is thin, and in the fresh condition
of the animal transparent and inconspicuous, but becomes opaque when the animal is
hardened in picric acid. The inner longitudinal layer consists of stout bands of fibres
running parallel to one another. The outer circular fibres are far less developed, and are
not gathered into bundles, but cross one another slightly obliquely in their transverse
course, forming a slight meshwork over the longitudinal fibres.

“ Beneath the muscular tunic and between its meshes the body mass is filled up with
a gelatinous, hyaline, structureless matter, imbedded in which lie the viscera and the
muscles attached about the orifice of the sheath of the proboscis. Internal muscles, except
those referred to, were not observed.

“ No eyes or other sense-organs were found, and ciliated sacs were not seen.

“From the circumstance of the only specimen of Pelagonemertes having been much
lacerated, and from the animal not having been dissected, it will of course require further
examination. In the specimen as procured there was a deep constriction of the body at
about the junction of the first with the second fourth of its length. This, it appeared
pretty evident, had been caused by the meshes of the net. The posterior extremity
was somewhat injured, and its form may not be quite correctly given. Ciliated sacs
may be present, and the structure of the proboscis might throw light on the affinities of
the animal.

“The form of the digestive system is the most remarkable feature about Pelago-
nemertes in its close resemblance to that of Dendrocela. In other respects Pelago-
nemertes is thoroughly Nemertine in structure, being merely modified for pelagie existence.
It is remarkable that the gelatinous hyaline mass of the body is not tegumental in
character, but apparently homogeneous with internal structures.

REPORT ON THE NEMERTEA. 29

“The occurrence of a peculiar burnt-sienna colour in many very different pelagic
animals is remarkable. With many the colouring may be explained as_ protective
resemblance to the oceanic seaweeds. For its occurrence in others, such as Salpa and
Pelagonemertes, in an otherwise hyaline body, there may be some common cause, possibly
also protective.

“Diagnosis of the genus Pelagonemertes, H. N. M. :—Body leaf-shaped, gelatinous,
hyaline. The anterior extremity of the body broad and abrupt, the posterior narrowed
to a point. The digestive canal with thirteen pairs of lateral ramifications, as in
Dendrocela. Integument thin and hyaline, with a thin muscular tunic immediately
beneath it, consisting of external circular and internal longitudinal fibres. The animal
free-swimming, oceanic.”

Moseley’s second article, which appeared nine months later, was again accompanied by
figures, which will be found reproduced on Pl. I. figs. 23, 28-31, The contents were as
follows :—

“On June 5, 1875, in lat. 34° 58’ N., long. 139° 30’ E., about halfway between
Vries Island, Oosima, and Cape Sagami, the trawl was used by H.M.S. ‘Challenger’ in
from 755 to 420 fathoms. A young specimen of a peculiar pelagic Nemertean, which has
been described by me (Ann. and Mag. Nat. Hist., ser. 4, vol. xv. p. 165, March 1875)
under the name of Pelagonemertes Rollestoni, in honour of my friend and instructor
Professor Rolleston, was found by Dr. von Willemoes Suhm adhering to the net, and by
him handed over to me for examination. The adult specimen before procured and
described was in a similar manner found adhering to the trawl-net after a deep-sea
dredging by Dr. von Willemoes Suhm.

“The animal was very much smaller than the one obtained before, measuring only
13 mm. in extreme length, and 11 mm. in extreme breadth, and about 1 mm. in extreme
thickness. It was in good preservation when found, and living, and, being extremely
transparent, much more of its structure could be observed than in the case of the more
full-crown specimen. Unfortunately, an attempt to preserve the specimen by treatment
with perosmic acid and subsequent action of glycerine failed, and the specimen perished.
The trawl came up late in the evening, when only an hour of daylight remained; the
examination made was thus a hasty one.

“The animal showed the same feeble pulsating movements which had been shown by
the adult.

“The external gelatinous investment of the body was perfectly transparent, and none
of the peculiar corrugations of a thin superficial epidermic layer were visible as in the
adult specimen. The contours of the body were well preserved, including those of the
hinder portion, which was broken in the specimen before obtained.

“The forepart of the body is wide, with rounded margins; the posterior narrowed,
with a series of indentations on its margin corresponding to the successive pairs of

30 THE VOYAGE OF H.M.S. CHALLENGER.

diverticula of the digestive tract. At the extreme hinder termination of the body is a
shallow notch, at the bottom of which is the anus.

“The mouth, which is a simple opening at the apex of a small, short, conical
protuberance, was situate just in front of the nerve-ganglia on the ventral surface of the
body (it is not shown in the figure, which represents the animal from the dorsal aspect).

“The central canal of the digestive tract terminated in front in a wide, rounded, blind
end, and tapered gradually to the anus at the posterior end of the body.

“The lateral diverticula in this young specimen were evidently in an immature
condition, and the successive pairs showed successive stages of development, the most
anterior being the most fully formed. This most anterior pair is the only one which
shows a commencement of ramification at the peripheral extremities. The ramifications,
so ample and well marked in the adult worm, are seen here to be developed as ceecal buds
from the outer ends of the long diverticula. The diverticula themselves, of which five
pairs were present in the young specimen here figured, arise, as can be seen from the
figure (pl. xi. fig. 1 = Pl. I. fig. 23), as simple lateral buds from the central digestive tube.
These buds gradually increase in length, their peripheral ceecal ends being always larger
than the tubes connecting these with the central digestive tract, and eventually these ceecal
ends give off buds and form ramifications. A shght enlargement in the rectum, situate
just anteriorly to the anus, and shown in the figure, probably represents the spot where a
sixth pair of diverticula were about to bud off from the digestive tube. The diverticula,
with the exception of the first pair, were not placed exactly opposite one another, the
right diverticulum in each pair being situate anteriorly to the corresponding left one.

“The digestive tract was filled with a dark reddish-brown matter, consisting of large
granules and oil-globules. The contents of the diverticula were darker and more opaque,
and contained numerous clear oily globules of a bright yellow and bright red colour,
mingled with similar opaque globules (fig. 4, a= fig. 28). The brightly coloured globules
exactly resembled those of the main tract. Similar coloured globules occur in larval
Nemertines, and I have observed them also im a marine Planarian larva, possibly that of a
Thysanozoon, or the Planarian larva described by Johannes Miiller from the Mediterranean,
supposed to be that of Hurylepta (Claus, ‘Grundziige der Zoologie,’ p. 286).

“The sac of the proboscis corresponded exactly with that described in the adult. It
was here found to terminate posteriorly in a blunt point at a short distance from the
hinder end of the body. The fluid contained in it appeared transparent and without
corpuscles. The proboscis itself could be carefully examined in the present transparent
specimen. It was without stylets and quite simple, invaginated in the usual manner ; it
was not seen fully protruded, but when so protruded must be slightly longer than the
animal’s body; it has an outer pellucid gelatinous investment, and an inner muscular
layer (fig. 5=fig. 29). No retractor muscle was observed to be connected with it.

“The nervous system consists of two pairs of ‘ganglia, of which the upper are by far

REPORT ON THE NEMERTEA. 31

the larger and give off the stout nerve-cords. The cords stretching backwards on either
side unite with one another above the rectum at the hinder end of the body. The nerve-
ganglia are shown enlarged in fig. 3(=fig. 30). Nosense-organs of any kind were detected.
On the outer margin of the large superior ganglion (fig. 3) a series of elongate pellucid
cells were arranged side by side perpendicularly to the curved surface which they form.
Abundant fine nerves were given off from the entire length of the nerve-cords to the
surface of the body, the muscles, &c., arising both from the inner and outer margins of
the cords. At the origins of these nerves from the cords there are very slight swellings
on the margin of the cord, but these do not contain any nerve-cells. The nerves are very
fine, hyaline, with a nearly rectilinear course, and they generally divide into two near
their points of distribution ; they are never tortuous or much ramified. Terminal organs
on the surface of the body in connection with the nerves were carefully sought for but
could not be found.

“ A pair of vascular trunks follow the course of the nerve-cords through the body, lying
internally to them and beneath them. The vessels unite with one another posteriorly, as
do the nerve-cords; their course is undulating. Just behind the nerve-ganglia the
vascular trunks are enlarged into wide reservoirs. No branches of these vessels were
seen, and though the animal was living when examined, no pulsation in them was
observed. The vessels had a pellucid wall, in which were imbedded elongate oval nuclei
(fig. 4, b=fig. 28), but which otherwise appeared structureless. No motion of any fluid
within the vessels was seen.

“ Although the specimen under description was evidently so immature, well-developed
ovaries were present, the specimen being a female, as was the adult one before obtained.
The ovaries follow in their disposition the vascular trunks so closely as to appear as if
connected with them. The ovaries are simple ovoid sacs with a distinct wall (fig. 2 = fig. 31),
filled with ova (in various stages of development) and granular matter. A dark irregular
fissure appeared on the centre of each ovary as viewed from the dorsal surface, which I
believe to be an opening by which the cavity of the organ communicates with the exterior,
thus dorsally. The ovaries were not quite regular in disposition, an extra anterior one
being developed on the right side of the body. In the interspace between the most
anterior and larger pair of intestinal diverticula and the next posterior pair were four pairs
of ovaries, whereas in the succeeding corresponding interspaces were only single pairs of
these organs. In the adult specimen described in the ‘Annals’ (March 1875) a single
ovarian sac only was present in each interspace between the diverticula of the digestive
tract. It would therefore seem probable that on further development three pairs of
diverticula would have budded out between the first and second pairs in the present
specimen.

“The muscular system consists of a series of excessively fine transversely or circularly
disposed fibres, which are external in position to a series of broad band-like longitudinal

32 THE VOYAGE OF H.M.S. CHALLENGER.

muscles. The longitudinal muscular bands are in close relation with the proboscis-sac,
Their exact disposition was not made out, and their arrangement, as shown in the figure,
will possibly need correction.

“On the whole, Pelagonemertes is a form of considerable zoological importance. In
the flattened form of its body, and in its dendroccelous digestive tract the animal
resembles Planarians. Amongst the Rhabdocceles the Prostomex possess an exsertile
proboscis like that of Nemertines, but such an organ is present in no Dendroceele. In
all particulars—in being unisexual, in the simplicity of the generative organs, in the form
of the nervous and vascular systems and of the proboscis, in the position of the mouth and
presence of an anus—in all essential structures Pelagonemertes is most distinctively a
Nemertine. Only in its remarkable dendroccele intestine does it differ from all other
Nemertines, and (but this is of far less importance) in the modification of its tissue into
the peculiar hyaline gelatinous condition which is characteristic of so many otherwise
most widely differing pelagic animals.

“The development of the dendroccele intestine is very remarkable, in that the lateral
ramifications are apparently to be regarded as a series of buds occurring successively
from before backwards from a previously straight digestive tract, such as exists in other
Nemertines. In this the digestive tract differs entirely from that of dendroccelous
Planarians, such as Leptoplana tremellaris, in which, as we know from the observations
of Keferstein (‘ Beitriige zur Anatomie und Entwickelungsgeschichte eimiger Seeplanarien
von St. Malo, Abhandl. der k. Gesellschaft der Wiss. zu Gottingen, 4ter Band,
Gottingen, 1868, Taf. ii. figs. 19, 20, 21, text p. 34), ‘the great yelkballs arrange them-
selves in the embryo with regularity and map out the form of the future digestive tract,’ the
peripheral ramified part of the tract being formed at the same time as the central portion.

“The peculiar form of the front of the body of Pelagonemertes may be regarded as an
instance of the excessive formation of the head lappets of many Nemertines. In having
no ciliated sacs and an unarmed proboscis, Pelagonemertes resembles Cephalothriz, but
the animal must evidently be placed in a new family of Nemertines, for which I propose
the term Pelagonemertidee, thus characterised :—

“ Animal pelagic in habit. Body gelatinous, hyaline, broad and flattened. Proboscis
unarmed. Ciliated sacs absent. Special sense-organs absent. Digestive tract dendro-
ceelous.

“The occurrence of a second specimen of Pelagonemertes off Japan shows that the
animal has a wide distribution. It was found on both occasions adhering to the trawl-
net, and is, from its very slight consistency, easily overlooked. Hence it may have
been often missed by us, and probably is as widely distributed as other oceanic forms.
Since it has never been taken by former observers of pelagic animals nor by us in the
tow-net, it is very probable that it occurs only in deep water, and does not come to the
surface ; it is, however, most evidently not an inhabitant of the sea-bottom.

REPORT ON THE NEMERTEA. 33

“ Postscript.—Since the above was written, my attention has been directed by
Dr. von Willemoes Suhm to Lesson’s original figure of Pterosoma in the ‘ Zoology of the
Voyage of the Coquille’ (which work we have been able to consult, with a splendid series
of similar publications, in the Hawaian Government Library at Honolulu), and to the
many points of resemblance between Pterosoma and Pelagonemertes.

Fic. 3.—Pelagonemertes rollestoni, Moseley, enlarged, viewed from the dorsal surface ; the proboscis is partly extruded,
P, proboscis ; PrS, sac of proboscis; IP, invaginated portion of proboscis within the proboscis-sac ; G, superior nerve-
ganglion; NC, nerve-cords; V, vascular trunk (the upper V points to an enlargement of the vessel lying just
posteriorly to the superior nerve-ganglion); I, intestine ; D, diverticula of intestine ; 0,0, ovaries; CM, circular
muscles ; LM, longitudinal muscles.

«“ Pterosoma plana is described by M. Lesson, ‘Voyage de la Coquille, Zoologie,’
Paris, 1830, p. 254, and figured, pl. iii. figs. 3 and 3 bis. Pterosoma was obtained in
great abundance by Lesson between the Moluccas and New Guinea, August 31, 1828.

“The animals measured 3 inches and some lines in length, 18 lines in breadth, and
3 to 4 lines in thickness. In general form and gelatinous structure Pterosoma resembles

(ZOOL, CHALL, EXP.—PART LIV.—1886.) Hhh 5

3 THE VOYAGE OF H.M.S. CHALLENGER.

Pelagonemertes further, in that a series of polygonal areas are marked out on its surface.
The spirally wound organ, described as a tube, which is indicated in the figure of
Pterosoma, can scarcely be anything else than the proboscis of a Nemertine, the mouth,
at the extreme end of the body, being probably the aperture of the proboscis-sac, and the
fusiform nucleus the sac itself. On the other hand, it is ditticult to conceive that Lesson,
with a number of specimens available for examination, could have missed seeing the very
conspicuously burnt-sienna-coloured ramified intestine of Pelagonemertes had such been
present in his Pterosoma. Further, in Pterosoma,a pair of elongate, closely opposed
eyes are described and figured, having transparent coloured corneee.

“On the whole, now that a pelagic Nemertine is known to exist, there seems little
doubt that the animal seen and figured by Lesson was a Nemertine and not a Mollusc,
but it seems to have been a distinct form, with a pair of eyes and an unbranched digestive
tract.”

For the sake of facilitating reference to Lesson’s two figures of Pterosoma, in which
Moseley is so strongly inclined to see a second species of pelagic Nemertine from the

tropical seas—a supposition in which I entirely concur—I have reproduced these on
Lelk MAUD Eei args 108 2)

The single available specimen of Pelagonemertes, when it came into my hands in
September 1884, was no longer entire, but consisted of two fragments of the body, and
of three small fragments of the proboscis. Both body-fragments were slit open on the
ventral side, the internal surface of the digestive tract, and partly that of the proboscidian
sheath, having thus been laid bare. The terminal portion of the body was missing
(vide Moseley, supra). My friend Professor M‘Intosh, who made these incisions and
examined the specimen before it came to me to be sectionised, has made the following
notes :—

“The structure of the cutis corresponds with that of other forms. In the preparation
the transparent gelatinous basis-substance for the most part alone remained, the granular
cells and clear mucous or gelatinous contents of these spaces having escaped. Beneath
this layer is a remarkable deep investment of basement tissue, which forms an elastic
investment all round the body. Numerous ducts, often having a zig-zag appearance,
pass through this coat.

“The muscular layers of the body-wall, as Professor Moseley observes, are compara-
tively thin, The external circular fibres are hardly to be distinguished in ordinary
transverse sections, and form a thin layer outside the longitudinal. Such a condition
contrasts strongly with the well-marked circular coat in Amphiporus lactifloreus. The
longitudinal muscular coat is likewise comparatively thin, though it is better developed
than the circular.

“ Proboscis.—In the preparation the proboscis is partly extruded, and issues in the
same manner as in the ordinary form. It is streaked by longitudinal lines externally.

REPORT ON THE NEMERTEA. 35

“In minute structure the anterior region quite corresponds with the typical form,
presenting externally a layer of elastic fibrous tissue, which in transverse section presents
a series of circular fibres. The external longitudinal muscular coat is well developed.
The reticulated layer cuts the foregoing layer into sections, as usual in most other forms,
and the connecting bands seem to be broad, the longitudinal belts rounded in transverse
section, The condition of the specimen, which is imperfectly preserved, however,
probably causes this layer to be more prominent, and the separation between the two
longitudinal coats wider. The inner longitudinal muscular coat has the usual thickness
and appearance, and the same may be said of the inner circular muscular coat. The
basement layer is very largely developed, and fills up a considerable part of the central
area. It is somewhat regularly streaked by a radiating series of granular channels.
Occasionally tortuous and numerous granular cells occur in it. The central granular
glandular tissue has mostly disappeared, but in minute structure it corresponds with that
in other forms.

“The middle region of the organ presented no visible stylets, but otherwise it agrees
in general configuration with the typical form, though less definitely formed. The glands
of the posterior region are largely developed.

“The posterior part of the proboscis sheath had a quantity of flocculent material
microscopically presenting numerous granular, and often nucleated cells, mixed with
granular material ; such might be connected with the proboscidian gland.

“The mouth, as Professor Moseley observes, forms a well-marked aperture with a
frilled margin. It is proportionally the most distinct aperture yet observed. The
minute structure of the cesophageal region is similar to that of other forms, and it
terminates similarly:

“The dendritic arrangement of the digestive system, Professor Moseley states, is the
most remarkable feature about Pelagonemertes, indeed it differs from all other
Nemerteans. The condition of the organ in the other forms, however, renders the
arrangement less striking. In Nemertes gracilis, for instance, it is considerably divided.
Microscopically it agrees with other forms in cells, &c. Professor Moseley describes a
distinct anus in the young form, but the specimen may have been incomplete posteriorly.
It is certainly unusually distinct. The vascular system offers no particular feature of
interest so far as observed, and seems to follow the ordinary arrangement. ‘The lateral
vessels appear to vary a little from the ordinary relation to the nerve-cords, being often
internal rather than inferior, but probably such is due to the yielding nature of the
tissues. The inner lining of the vessels is granular, and a few granular cells appear in
the centre, but the nature of such is problematical.

“The nerve-trunks are enveloped in a coating of nerve-cells. The branches from the
ganglia and nerve-cords are remarkably distinct, presenting a clear sheath and granular
axis cylinder. The gelatinous interstitial substance extends between the muscular

36 THE VOYAGE OF H.M.S. CHALLENGER.

substance and fills up the central area of the body in transverse section to an unusual
extent, as pointed out by Professor Moseley.

“ Besides the organs mentioned by this author within the body-cavity, a large number
of granular nerve-cords run outwards to the surface (muscular wall), besides fine fibres,
which are very apt to assume a coiled or zig-zag appearance. Some of these much
resemble blood-vessels, but they are probably nerves, and they divide into fine branches
towards the muscular coat.

“The proboscidian sheath or chamber is very large, and its anterior aperture would
seem to be unusually distinct. The structure of the parts in unrolling of the organ is
the same as in the others, and the wall of the chamber presents continual circular internal
longitudinal fibres; the posterior region of the proboscis is firmly fixed as usual to the
internal wall of the proboscidian sheath at its narrow posterior end. The fibres of
attachment are short, so that the cul-de-sac of the posterior chamber is brought close to
the surface of the wall of the sheath. From the appearance of the parts posteriorly, it is
possible that the region is in process of repair after laceration. Indeed, it is not unlikely
that both anterior and posterior ends can easily be repaired after rupture, and that might
account for the absence of eyes (see Lesson’s Pterosoma, ‘Voyage of the Coquille’).
Such gelatinous forms are especially prone to rupture, and sufficient is known of the
recuperative power of the Nemertean to render repair rather than permanent injury the
rule. The proportionate size and firmness of the proboscidian chamber, with its glistening
internal surface, are certainly remarkable, and, on the whole, my impression is that the
form is incomplete posteriorly.”

All the fragments of Pelagonemertes that came into my hands were carefully treated
with staining reagents, hardened, imbedded and sectionised. The sections were all trans-
verse. Pl. VIII. fig. 3 represents one of the average sections with parts of all the important
gelatinous basis. No sufficient sections of the brain

co)
were available, nor were distinct traces found of a nephridial system. The integument

organs imbedded in the common

was in most parts of the surface wholly deficient ; in a few others its general correspond-
ence in transverse section with what is typical for the Hoplonemertea could be verified.

Certain other striking particulars, also visible in this section, and on the whole only
confirmatory of what we already knew by Moseley’s and M‘Intosh’s observations, are
(1) the absence of a dorsal median blood-vessel; (2) the ventral openings of the generative
sacs; (3) the numerous transverse fibres, both contractile and nervous, running in
different directions through the body-jelly. Further, it may be observed, even with a
rather low power, that each of the ripe ova is surrounded by numerous small follicle cells
(Pl. VIII. figs. 3, 11), and that the nucleolus is often only represented by very numerous
small chromatin spheres.

By the aid of stronger powers the details also represented on Pl. VII. by
figs. 4-15, can be more fully studied, and of these mention will successively be made in

REPORT ON THE NEMERTEA. ay

the different paragraphs, which are more especially devoted to the internal anatomy of the
different representatives of the species, that are here described in their systematic
arrangement.

C. SCHIZONEMERTEA.
Family Lineip &,
Cerebratulus, Ren.

To this genus I wish to refer all the Schizonemertea collected by the Challenger. I
have elsewhere (VII) insisted on the difficulty of distinguishing the genera Cerebratulus,
Lineus, Micrura, &e., of which perhaps the two first may be distinguished by an
ontogenic difference (Pilidium or Desor-larva). And even this distinction is not
definitely established. It is simply impossible to refer spirit specimens to any one of
these genera rather than to any other, and having formerly included Micrura as a
synonym amongst Cerebratulus, I now even feel inclined to do the same with Lineus.
What value has a generic distinction when it can never be of any use to a taxonomist 2
And why should a developmental difference, such as that which obtains between a
Pilidium and a Desor larva, not be sufficiently honoured by a specific distinction ?

As to describing new species in this genus, it is even more difficult than in any other,
because of the number already existing, which are partly solely distinguished by their
coloration in life, a character not available in determining the Challenger specimens.
Hence, only in seven cases can I hold myself justified in referring the fragments to separate
species, six of which are new. The remaining fragments and heads, which clearly show
the Cerebratulus type (eg., Pl. XV. fig. 8), I will not specifically distinguish ; what
remarks I have to make about them will appear when treating of the anatomy, and
will then be noticed as pertaining to the genus Cerebratulus in general.

Following the order of succession of the stations at which the Schizonemertea were
successively dredged during the expedition, we will now proceed to describe them.

Cerebratulus truncatus, n. sp. (Pl. I. figs. 11, 12).

This species, collected on the coast of Nova Scotia, and, as we refer a specimen from
Bermuda to it, also frequenting the ocean in the vicinity of those islands, was captured
May 8, 1873 (Le Have Bank), and once more, on May 20 of that year, when it came
from a depth of 85 fathoms at Station 49.

The anterior part of these two specimens is figured on Pl. I. figs. 11, 12, the first
being a side view, the second a ventral view, the latter more considerably, the former
about four times enlarged. From both figures it is seen that the mouth is small and close

38 THE VOYAGE OF H.M.S. CHALLENGER.

to the tip of the head, which is more or less truncated, that the cephalic slits are compara-
tively short, extending on to the anterior surface of the head, where they do not, however,
coalesce, but leave a small interval in which the proboscidian aperture is situated.

This is all that can be said of the external appearance,

The internal structure further confirms the supposition which the external characters
point to, viz., that these two specimens belong to the same species. Thus, certain chief
points in the series of transverse sections made through both the specimens coincide to a
degree that may be judged of by the following table :—

Tu Specimen a. In Specimen 0.

The superior brain commissure is situated in section No. : 30 34
The inferior brain commissure is situated in sections No... 35-39 38—44
Canal of the posterior brain lobe is situated in section No. . 43, ol
The mouth begins in section No... : : : 55 60
The mouth ends in section No. : : : : 84 105
First appearance of nephridia in section No. . : : 97 112

In specimen a (May 8, 1878) there are noticed four transverse deferent ducts to the
longitudinal nephridial duct on the left side (in sections 138, 175, 217 and 278), and four
on the right side (sections 147, 191, 217 and 278).

In specimen b (May 20, 1873) there is a less regular arrangement, some of the
deferent ducts being double, z.e., two at the same level or in the same section. Once in
this specimen this is so arranged that in the one section (No. 197) there are four deferent
ducts cut nearly throughout their whole length. In the portion of the cesophageal region
sectionised, which, however, does not embrace the whole nephridial region, I count in this
specimen on the left side six deferent ductules (sections 112, 144, 156, 159, 197, 207), and
to the right also six, which are only partly opposite to the left ductules (sections 142, 168,
178, 180, 197, 208). In judging of this apparent discrepancy it should not be lost sight
of that the short distance separating the two ductules 156 and 159 on the left is still
symmetrically repeated on the right side in 178 and 180, though somewhat further
backwards.

A commissure uniting the two vagus nerves after they have left the brain and before
they have yet reached the cesophagus was distinctly noticed.

The histological details of the intecument fully correspond to the type of Cerebra-
tulus corrugatus, which will hereafter be more fully described and figured (ef. Pl. XIII.
fig. 6), and which is diagrammatically represented in fig. 9 of Pl. XI. as differing from
figs. 10 and 11.

One of the specimens showed a very curious pathological degeneration, which I will
however, only touch upon very briefly. The muscular tissue on a restricted but ring-
shaped region not far behind the head, and only as far as the circular and longitudinal
muscular coats are concerned, is replaced by (or gradually passes into) a homogeneous:

REPORT ON THE NEMERTEA. 39

gelatinous mass, in which granular spherical bodies with large and distinct nuclei
(about one-fifth of the diameter of the body-wall on this spot) seem to be suspended.
Is this a local injury? Are these bodies enclosed gregarines or other parasitical
unicellular organisms ?

These questions can as yet only be formulated but not answered, and I would call
the attention of future observers dealing with fresh material to similar cases, which no
doubt must be accompanied by some externally visible distinction between the tissues.

Of the Bermuda specimen, which I refer to this species only with doubt, and which
measured 33 mm. in length by 25 mm. in diameter, the integument was very imperfectly
preserved ; still it corresponds in the remaining characters with the other specimens of
Cerebratulus truncatus. There are also points of agreement in the structure of the
proboscidian sheath.

The transverse blood-vessels are very thick-walled in this specimen, a feature more
particularly due to the basement-tissue below the inner epithelial lining.

Cerebratulus medullatus, n. sp. (Pl. XI. fig. 10; Pl. XII. figs. 9, 10).

It is hardly consistent with the most lenient rules of zoological nomenclature, and it
is certainly not consistent with those which | have myself advocated in my introduction, to
establish a new species on a fragment which has neither head nor tail! Still, as I have been
rather careful on other occasions, and that especially with regard to genera, I may be trusted
to be anxious to guard against superfluous additions to an already cumbersome synonymy.
The reasons by which I am guided in putting up this mutilated spirit fragment as the
type of a new species are purely morphological, and, as will be seen in the paragraph
treating of the nervous system, the peculiarities offered by this species are of sufficient
morphological interest to give it a place by itself, and (in at the same time naming it) to
direct the attention of collecting naturalists to this form.

It came up in the same haul of the dredge as did one of the specimens of Cerebratulus
truncatus just described, viz., at Station 49, off Nova Scotia, from a depth of 85 fathoms.

In sections it is, however, immediately seen to be distinguished from the foregoing
species by several features, the first of which concerns the integument. Instead of the
integument being separated from the longitudinal outer muscular layer by a more or less
massive expanse of basement-tissue (PI. XIII. fig. 6), the integument itself being divided
into a superficial and a deeper glandular layer (which are separated by a secondary
basement membrane and an expanse of fibres, such as is found in Cerebratulus
corrugatus, Cerebratulus truncatus, &c., also in the Challenger collection), our present
species has the superficial layer of the integument immediately apphed to the outer
longitudinal muscles, from which it is thus only separated by the outer secondary basement
layer just alluded to (PI. XII. fig. 10). This fact causes the integument in transverse

40 THE VOYAGE OF H.M.S. CHALLENGER.

sections to appear very thin in comparison to that of other species. However, closer
inspection reveals (as will be more fully discussed in the paragraph devoted to the
integument) that the deeper glandular layer is not wholly deficient, that it has only
become intercalated amidst the outer longitudinal muscular layer, which im this species is
not very massive, and that its cellulo-glandular elements thus reach amongst these muscle
fibres, even as far down as the nervous layer just outside the circular muscular coat
(cf., Pl. XIL figs. 2, 10). The strong affinity which these eland-cells possess for staining
reagents brings this out in the sections very clearly.

Nor is this the only distinctive feature of Cerebratulus medullatus; the second, and
none the less important, is that in the nervous plexus just alluded to, the dorso-median
longitudinal thickening, which I shall presently, in the anatomical part of this Report,
designate as the medullary nerve, is exceptionally massive (cf, Pl. XI. fig. 10; Pl. XII.
fiz. 9), being about one-third to one-fourth of the thickness of the fibrous core of the
lateral longitudinal nerve-trunks, Amidst the fibres of this dorso-median stem a few
nuclei, more faintly coloured and marking the presence of nerve-cells, are also seen,

In longitudinal sections through the same specimen, the unusual size, distinctness,
and marked individuality of this nerve-stem was also very obvious.

No other features of this species will for the present be enumerated. The specimen
on which it is founded was of the female sex.

I sincerely hope that the points here enumerated may enable American naturalists,
when recapturing specimens of the species, to recognise it and to give us indications of its
zolour and other peculiarities in life, of the shape of its head and cephalic slits, and of its
brain lobes and proboscis.

Cerebratulus longifissus, n. sp. (Pl. I. fig. 16; Pl. XV. figs. 1, 9, 10).

No other Schizonemertea were collected between the last-mentioned station and
Marion Island (Station 1444). A Cerebratulus was here brought to ight, which it will
in future be easy to recognise by the fact of its having uncommonly long cephalic slits.
The specimen, which was perfect, and is also characterised by its comparative shortness, is
figured on Pl. L fig. 16. On inspecting it with the naked eye the mouth was found to
be small and to be situated anteriorly; the proboscidian aperture occupied the place
indicated in the figure, whereas on the dorsum of the animal, just behind the end of the
slits, two rows of sublateral, very small pores were noticed, being visible as extremely small
white punctures. These rows were continued very far backwards. Although, on account
of their reaching so very far forwards, they might at first sight be taken for the exterior
openings of the nephridial system, the sections showed that they are indeed the
generative pores. Moreover, that the cephalic slits, though long, are comparatively
shallow, especially in their posterior portion, and that the canals leading into the posterior

REPORT ON THE NEMERTEA. 41

brain-lobes do not open out in the lower angle of the fissure but far forwards, in agree-
ment with the situation of those lobes.

It will perhaps best serve the purpose of conveying an idea of the relative situation
of the more important organs in the head and trunk to give, as was done for the fore-
going species, the number of the section of the whole transverse series (into which head
and anterior cesophageal region were cut up) in which these organs occur.

We then find:—

Section 30. First appearance of the lateral blood-
lacune in the head.

Sections 64-66. Superior commissure of the brain-
lobes.

Sections 71-78. Inferior commissure of the brain-
lobes.

Section 86. Left canal from cephalic fissure into
posterior brain-lobe.

Section 87, Right canal from cephalic fissure into

Section 71. The median blood-vessel enters the
proboscidian sheath.

Sections 350-360, It again leaves it.

Sections 129-159. Mouth.

Section 129. First appearance of the nephridial
canals just above the level of the longitudinal
nerve-trunk.

Sections 355-400. Left deferent ducts of nephri-
dial system.

posterior brain-lobe.
Sections 84-104. Left posterior brain-lobe.
Sections 89-105. Right posterior brain-lobe.

Sections 329-335. Right deferent ducts of nephri-
dial system.

These two deferent ducts (the only pair) are seen in the same section which still
shows the cephalic fissures. The ducts do not, however, open out into these fissures, but
just above them. This also proves how far the fissures reach, all along the cesophageal
region. In the 410th section the end of the cephalic fissures may be said to be reached,
the whole of the nephridial system, excretory ducts and all, being thus situated within
the region of the fissures.

Another specimen from the same locality was without a head, and though the
principal points of comparison are thus deficient, I feel confident, by the internal
characters which are shown by the sections, that we may look upon this specimen as
belonging to the same species.
interesting points with regard to the generative organs, which will be more fully discussed
in the paragraph devoted to those parts.

Another feature by which the species is--if not distinguished from its neighbours—

It was exceedingly well preserved and showed certain

at least characterised as far as the fragments allow us to judge, is the great thickness
of the transverse connecting vessels between the medio-dorsal vessel and the two lateral
ones.

Cerebratulus corrugatus (M‘Intosh), Hubrecht (Pl. I. fig. 17; Pl. XI. fig. 9; Pl XII.
figs. 3, 4; Pl. XIII. figs. 1-6; Pl. XIV. figs. 2-4).

This species, which was first described by M‘Intosh in the Transactions of the Royal
Society for 1879 (extra vol., p. 262), has again been recognised by this author as occurring

(Z00L. CHALL. EXP.—PART LIv.—1886.) Hhh 6

42 THE VOYAGE OF H.M.S. CHALLENGER.

amongst the Challenger Nemertea. I have already indicated (p. 37) why I wish to bring
it under the genus Cerebratulus, rather than under Zineus, where M‘Intosh placed it.

The following notes were made by him concerning the Challenger specimens.

“ Dredged in considerable abundance in Royal Sound, Kerguelen, January 27, 1874,
in 25 fathoms.

“Stat. 149, off Christmas Harbour, Kerguelen, 120 fathoms, small specimens.

“ Stat. 151, off Heard Island, 7th Febr. 1874, 75 fathoms. Some reach the length of
200 mm., and much contracted forms have a diameter of about 15mm. In the cesophagus
of one was a blackish mass of sand-grains, sponge-spicules, Diatoms, and mud.”

In M‘Intosh’s previous publications the description of Lineus (Cerebratulus) corru-
gatus contains the following characteristic features :—

“Body rather abruptly poimted anteriorly, and more gradually posteriorly. The
cesophageal region is marked externally by a series of prominent and somewhat regular
rugee, which sweep from the mouth dorsally and ventrally.

“ Colour dark olive throughout, with the exception of a white band, which crosses the
anterior border of the snout, and passes backward to the posterior third of the lateral
fissure, where it bends dorsally and terminates.”

“The special characters are the very large mouth, with the prominent rugee, which

show that the animal probably possesses unusual powers of cesophageal protrusion—a
supposition borne out by the great development of the external circular muscular fibres,
the dorsal longitudinal coat, and the other fibres of the organ. The internal glandular
lining is also very firm.”

A couple of figures are added, one a section of the proboscis, the other a section of the
ventral body-wall. The latter should be compared with our fig. 6 on Pl. XIII. It will
then be seen that M‘Intosh’s “ pigmentary layer, divided by a definite black band,” is
our superficial and deeper layers of the intecument (Jsg and Idq). The “ black band”
between them is no other than our external secondary basement membrane. What
M‘Intosh designates as the “curious translucent stratum cut into somewhat regular
spaces” is our basement layer proper (B), comparable to that of Hupolia and Carinina,
and radially traversed by bundles of contractile and nervous fibres, which bring about the
“yeoular spaces” alluded to.

On the whole, our two figures will be seen to correspond very well, only M‘Intosh
omits the nervous layer and the innervation of the cesophagus. The large mouth and
folded lips were very conspicuous in the Challenger specimens, the head of one, seen from
the ventral surface to show the mouth, being figured on Pl. XIII. fig. 5.

The different series of sections which I have made through four specimens of Cerebra-
tulus corrugatus were very instructive in several respects, although they all conform to
the well-known Schizonemertean type. It is especially the considerable development of
basement tissue of the integument (Pl. XIII. fig. 6, B), which not only brings out the

REPORT ON THE NEMERTEA. 43

distinction between the outer longitudinal muscular layer y and the integument much
more clearly than is so often the case in other Schizonemertea, where these two have be-
come blended, but which also enables us to trace the course of radial nerve-fibres coming
from the plexus or the longitudinal stems, and innervating (after having traversed the
muscular layer y and this basement tissue) the glands and sense-cells of the integument.
Cerebratulus corrugatus is, moreover, the species in which, for this reason, I was able to
determine the direct part which the longitudinal nerve-trunks take in the innervation of
the skin (Pl. XIV. fig. 2), whereas, even in this very favourable specimen, I never
noticed the faintest trace of a similar participation of nerve-branches directly springing from
these stems in the innervation of the subjacent musculature. In that case such branches
would have to take an opposite course, and would have to traverse in the first instance
the circular muscular layer 8. This was never observed. It will be seen in the paragraph
more especially treating of the nervous system, as well as in the chapter devoted to
general considerations, that this fact is, in my opinion, not without morphological
importance.

The specimen of Cerebratulus corrugatus is also of great importance in demonstrating
the relation of the medio-dorsal medullary nerve and the branches springing from it at
right angles as so many thickenings of the plexus (PI. XIII. fig. 2).

Cerebratulus parkeri, un. sp. (Pl. XIV. fig. 5; Pl. XV. figs. 5, 16).

A well-preserved specimen of a Schizonemertean was collected in the New Zealand
waters, which, I think, may safely be looked upon as belonging to a distinct species.

I have dedicated this species to the naturalist who of late years has done so much for
our knowledge of the New Zealand fauna, and whose anatomical preparations and zoologi-
cal collections from those regions have excited the admiration of visitors to the Colonial
and Indian Exhibition of 1886.

The head and anterior body fragments of Cerebratulus parkert are thus described in
M‘Intosh’s preliminary notes :—

“A fragment of the anterior portion, measuring about 34 mm. in length, and about
7 mm. in diameter at its flattened and widest region. The cephalic furrows and mouth
conform to the ordinary type. The body is somewhat rounded anteriorly ; flattened
towards the posterior end of the fragment.

“Transverse sections of the rounded anterior region show that the muscular walls of
the body are greatly thickened . . . . the longitudinal muscular fibres form a very
thick coat all round, especially, as usual, opposite the nerve-cords. . . . . The
circular muscular coat is uniformly thick, the longitudinal layer within it being excavated
superiorly by the large channel for the proboscis, and laterally by the very large and
a little below each nerve-trunk. The thickenéd part of

very muscular vascular canals

44 THE VOYAGE OF H.M.S8. CHALLENGER,

this coat is just beyond the proboseidian canal, while the thinnest part is in the median
line above it.

“The proboscidian sheath has a remarkably thick wall, which is chiefly composed of
an interwoven circular coat, presenting an irregular looped appearance in transverse
section. The fibres in thin sections seem to anastomose. On the inner surface of this
coat are some longitudinal fibres, with a glandular epithelial coat internally.

“ Posteriorly the body-cavity is greatly dilated by the presence of a vast series of ova,
so that all the muscular coats are much thinned, and the digestive canal contracted. The
inner longitudinal coat is especially affected, three thickenings only being left, viz., one
on each side of the proboscidian sheath, and one in the middle line ventrally. The ova
are compressed into various angular forms, between vertical partitions which occur at
short intervals in the region, and which fill up the entire area, except the small space for
the proboscidian and digestive canals superiorly.”

For some farther particulars concerning this species, I refer to the description of Cere-
bratulus macroren that is still to follow, and where the points of agreement and of differ-
ence between these two evidently closely related species will be more fully entered upon.

A second specimen, also from the New Zealand waters, shows that the conspicuous
development of the secondary basement layer of the integument, and the considerable
thickness of the medullary nerve, are further characteristic features of this species.

Cerebratulus angusticeps, n. sp. (Pl. I. fig. 15; Pl. XIV. figs. 1, 6; Pl. XV. fig. 4).

This is another Schizonemertean from the New Zealand waters (Station 1674, Queen
Charlotte Sound, June 27, 1874; 10 fathoms). Its head is figured on Pl. XV. fig. 4.
In M‘Intosh’s preliminary notes this fragment is referred to in the following words :—

“A fragmentary form, resembling in shape C. angulatus, and with an acutely pointed
snout. The diameter of the widest flattened region is about 4°5 mm. The colour is dull
yellow, with a darker stripe down the middle of the dorsum. . . . . The vascular
trunks lie opposite the nerve-cords, and this in the angular lateral region. The external
longitudinal muscular coat is largely developed, and the fibres are uniformly fine. The
very much produced lateral angle of the body is mainly composed of this coat. In such
forms the lateral nerve-cord seems to be much flattened from above downwards.”

The sections which I made of this fragment, horizontally through the head and trans-
versely through the trunk, were in many respects very instructive. To the flattened and
pointed shape of the head they added an internal distinctive feature of the species in the
unusual size of the posterior brain-lobes, which, although in intimate connection with
the superior brain-lobes in the same way as in the Schizonemertea, in general equalled
or even surpassed the latter lobes in length. Pl. XIV. fig. 6, gives a representation of
this, illustrating, at the same time, how in a horizontal section the blood-space (c.0./.)

REPORT ON THE NEMERTEA. 45

surrounding the cesophagus may very evidently be seen to be in direct connection with
that in the head—a fact known to Blanchard, and for the first time fully described by
Oudemans (Joc. cit.), but never adequately figured. This figure, at the same time,
demonstrates the projection of the posterior brain-lobe into this blood-space, by the con-
tents of which it is thus bathed.

Another figure reveals how the sections of Cerebratulus angusticeps were important in
another respect, viz., that of the medio-dorsal medullary nerve and the transverse branches
springing from it in metamerically arranged pairs (Pl. XIV. fig. 1). Nor was this
recularity exceptional in the region figured; it was characteristic wherever these trans-
verse nerve-tracts (which will be discussed more fully in their relation to the plexus in
the special paragraph) were met with, and was thus equally distinct ventrally and dorsally.
Ventrally, however, there is no median longitudinal stem.

On the other hand, the transverse tracts in Cerebratulus angusticeps may be traced
as high up as the lower brain-lobes, which they connect till just behind the strong
ventral commissure of these lobes.

These transverse commissural trunks are distinctly separate from those by which the two
stems of the vagus nerve are united close to their origin and in front of the mouth. The latter
(cf. Pl. XIV. fig. 5) are also present as distinct commissures in Cerebratulus angusticeps.

With respect to the nephridia, which often offer certain points of comparison for the
different species, I must state that the anterior part of the longitudinal duct is very
distinctly seen in the horizontal sections through the anterior extremity of the body, and
occupies its usual position in the circumeesophageal blood-space, whereas its size or its
histological details showed no special features. The deferent ducts of the nephridial
system were not contained in this section, nor in those made through the remaining
fragments of the further portions of the body. They were very probably situated in the
intervening part, which was sacrificed by M‘Intosh in drawing up his preliminary notes,
and I cannot thus state with certainty whether these ducts were single or more
numerous, terminal or not.

To Cerebratulus angusticeps I must refer another specimen which came up in the
dredge at Station 168 from a depth of 1100 fathoms. It was much torn and lacerated
(Pl. I. fig. 15), a phenomenon which it would, however, be rash to attribute to the depth
from which it was brought up, although the possibility of that being the cause cannot be
wholly excluded. The reasons for identifying the specimens with Cerebratulus angusticeps
are the following, and are deduced from the comparison of the sections :—(1) The length
of the superior brain-lobes stands to that of the posterior in the same (uncommon) rela-
tions as in the specimen above described ; (2) the ventral and parallel commissures of the
inferior brain-lobes are similarly very conspicuous ; (3) certain histological details of the
superior brain-lobes and ciliated canal, and also of the nerve plexus, are identical ; (4) the
aspect of the rhynchodzeum is very similar.

46 THE VOYAGE OF H.M.S. CHALLENGER.

Cerebratulus macroren, n. sp. (Pl. I. figs. 18, 14, 18, 19; Pl. X. figs. 8,9; Pl. XI.
osreb fos. 13:2) 7,.85 PL OUT Sigs, 7k ee eee toe 7 nose tele,

BI e figs.+253, 19).
From Japan, at Station 232A, a Schizonemertean has been brought home by the
Challenger Expedition, which I was first inclined to regard as identical with Cerebratulus
parkert, but which I have reluctantly been obliged to distinguish specifically

reluctantly,
because there being no possibility of giving outwardly visible distinctive features of
colour or shape, J must indicate an anatomical difference as the principal point of
distinction between the two; and all the more reluctantly because of a second specimen,
which, dredged at 700 fathoms off New Zealand (Station 169), was identical with the
Japan specimen, and differed from its much closer geographical neighbour in this very
same point. I could not, however, evade assigning the latter specimen to the species
now about to be described, knowing by experience that if the confusion created by the
unnecessary multiplication of specimens is often very troublesome, the premature com-
bination under one name of forms that afterwards may be shown to be different is often
quite as apt to lead to inextricable confusion, when characters which, as a matter of fact,
only belong to cne of them, are attributed to both.

About this second specimen M‘Intosh’s rough notes contains the following passage :—

“A small Lineus, presenting the ordinary external characteristics, and of a dull
yellowish hue, somewhat brownish on the dorsal surface in front. It was tapered from the
snout backwards. The cutis has a simple areolar structure ; the gelatinous contents were
slowly extruded in the sections after mounting, as cylindrical or clavate, translucent gela-
tinous processes. ‘The basement tissue is largely developed as a translucent belt all round.”

Of the larger specimen from Japan, the head is figured (PI. I. figs. 18, 19). The
cephalic slits are perhaps comparatively a little longer than are
those of Cerebratulus parkeri (Pl. XV. fig. 5), although the New
Zealand representative (Pl. I. figs. 13, 14) is again very similar,
even in this respect, to Cerebratulus parkeri.

The internal anatomical character, to which I alluded just now
as being a distinctive feature, by which the species differs from
Cerebratulus parkeri, is the size of the longitudinal nephridial
ducts, which are exceptionally conspicuous (both in the Japanese
and in the New Zealand specimens), and which have their deferent
i ducts leading to the exterior situated at the very hindmost end,
Fic. 4.—Nephridial ducts A ' .

and their communication Whereas in Cerebratulus parkeri there are two deferent ducts, the

with the exterior. a, for : 3
Cerebratulus parkeri;b, for one situated very closely behind the other, and placed about the

Cerebratulus macroren. 5 : x - ‘
middle region of the longitudinal canal. The accompanying wood-
cut diagrammatically illustrates this difference between the two species. Oudemans

(loc. cit.) has already demonstrated that the number of deferent ducts to the nephridial

REPORT ON THE NEMERTEA. 47

system increases with age; there thus might remain one chance that the New Zealand
specimen of Cerebratulus macroren could still be assigned to Cerebratulus parkeri, if
we assume that increase in growth can have brought about a further extension backwards
of the principal nephridial duct, and at the same time the appearance of a second deferent
duct immediately behind the first. For the present this assumption appears to me to be
more strained than my own, which unites the New Zealand and the Japanese specimens
by laying more stress upon the large size of the longitudinal tube, combined with the
terminal situation of the deferent duct.

The further peculiarities that reveal themselves on studying the microscopic sections,
certainly show that the two species, Cerebratulus macroren and Cerebratulus parkeri,
cannot be very far apart. Both have in common the very thick and homogeneous secondary
basement layer beneath the outer clandular layer of the integument (PI. XI. fig. 11).

It would also be difficult to point out salient points of disagreement in the muscular
body-wall, the proboscidian sheath, and the proboscis which would hold good when
respectively comparing the head, the cesophageal, or the posterior body region.

Cerebratulus, sp. inc. (Pl. X. fig. 7; Pl. XV. figs. 6-8, 18.)

At the close of our systematic description of the Schizonemertea I must mention
certain fragmentary specimens, which have all the aspect of belonging to distinct species,
but which I cannot venture definitely to unite with any of the species here described, or
with such as have been published elsewhere. The fragments here alluded to are mostly
without a head, and some of them of not inconsiderable size. I will discuss them in the
order of the stations at which they were obtained.

The first was procured in the Kerguelen waters. It is important, in consequence of
peculiarities in its integument, which will be more fully discussed in the paragraph devoted
to this system. A part of a section was figured on Pl. X. fig. 7, and from that section it
may also be gathered that the dorso-median medullary nerve is comparatively very massive.
This might eventually prove that it was related to Cerebratulus medullatus ; the differ-
ence in the integument, though important from a morphological point of view, hardly
justifying the establishment of a different species, supposing all the other characters,
external and internal, might prove to be identical. That difference might then be con-
sidered as indicative of a variety.

The second Cerebratulus, about which I must remain in doubt, was obtained among
the Philippine Islands (off Zebu). M‘Intosh has made the following notes about
these fragments :—‘‘ Fragments of a large species. The fragments in all measure over
100 mm., with a diameter of 12 mm. at the widest part. . . . . The carrying of
the vascular trunks far inwards towards the ventral middle line seems to be a feature

- . in this form.”

48 THE VOYAGE OF H.M.S. CHALLENGER.

There were further no particulars, nor any features deviating from the general type
of Cerebratulus to be gathered from these fragments.

Numerous other fragments, of which one was a head, were obtained at Kobé (Japan).
Three of these are figured on Pl. XY. figs. 6, 7, and 8. Sections were duly made of these
fragments, but do not give much additional light beyond the general result that we have
a Cerebratulus before us, which cannot be definitely identified with any of the species
hitherto described. The vicinity of the Japanese waters to scientific centres from which
accurate descriptions of the Japanese marine invertebrates may probably be expected
ere long, makes it all the more advisable to refrain for the present from creating or
identifying species from these regions of which sufficient data cannot yet be obtained from
the available fragments. Still the specimen figured on Pl. XV. figs. 6 and 7 deserves some
attention. The fragment, on which longitudinal and transverse white stripes were
visible, as indicated in the figure, was also distinguished by a peculiar rigidity. Trans-
verse sections (Pl. XV. fig. 7) showed that this phenomenon was occasioned, or at all
events accompanied by, an extraordinary development of intermuscular gelatinous tissue.
The section figured, when compared with that of Pelagonemertes (Pl. VIII. fig. 3), will
demonstrate this, and at the same time show it to possess the arrangement of muscular
layers and other peculiarities that are typical for Schizonemertea. These muscular layers
are, however, exceedingly reduced in thickness, and occupy a very inconsiderable fraction
of the vertical or horizontal diameter. The proboscidian sheath is, in the fragments
investigated, thin and unimportant; in more posterior sections there are indications
of its place being taken by more irregularly shaped, cellular material, without a lumen.
I am, however, not satisfied with the details that could be gathered from these fragments
concerning these important morphological points, and must refrain from more particularly
insisting upon them. ‘The transverse blood-vessels are exceedingly numerous and tor-
tuous—the latter phenomenon causing their lumen to be transversely cut a large number
of times in every section; these apparent perforations of the gelatinous tissue giving a
very peculiar appearance to most of the sections.

Another reason why I do not venture to establish a distinct species upon these
peculiar fragments, is the fact that I found them to be very considerably infested by a
large unicellular parasite (probably a Gregarine) which was not (as the Gregarines that
infest Nemertea generally are) found in the intestine, but which was present in consider-
able numbers in all the different tissues, both without and within the muscular layers.
When surrounded by gelatinous tissue, there was always a well-marked space round the
parasite in which it was contained.

There was no distinct capsule, and the free space may perhaps not have existed
during the life of both host and parasite. When first noticed, these unicellular parasites,
with very distinct nuclei and granular protoplasm, might have been mistaken for ova;
not only their distribution throughout the animal as isolated individuals, but also the

REPORT ON THE NEMERTEA. 49

presence of true ova in the fragments, which proved to have belonged to a female
individual, definitely excluded the possibility of any confusion on this head.

The question arises, whether the peculiar appearance of the different tissues recorded
above might be pathological, and somehow in causal relation to the infesting parasites.
It is this which necessitates extreme caution in the identification of these fragments. I
may here remind the reader that another case, presumably of a parasitic organism (also
unicellular, but of much smaller size) infesting the different tissues, was met with in
Amphiporus marion.

The last fragmentary specimen which I wish to record may, for all I know, have
belonged to the common Cerebratulus marginatus. It was collected in the Atlantic
Ocean, at Station 321, off the Brazilian coast. It was a very large and flattened speci-
men, but without head or tail. In M‘Intosh’s notes I find these fragments referred to as
follows :—

“Two fragments, respectively 70 and 108 mm. in length, and with a transverse
diameter ranging from 21 to 24 mm., the vertical (in the centre) being only 5 or 6 mm.
The dorsal surface was dull olive, with a dark median band, the greater part of the
breadth being marked by fine transverse striz, leaving only the borders untouched.
Various transverse lines, passing quite across the body, also occurred ventrally. The
median line and the borders had each a smooth belt, the rest beg marked by the closely
arranged and tranverse lines. A median ridge occurred along the ventral band.”

The ova of this species, polygonal by reciprocal pressure, and surrounded by a gela-
tinous outer layer (capsule), are figured on Pl. XV. fig. 18.

(ZOOL, CHALL, EXP,—PART LIv.—1887.) Hhh 7

a0

THE VOYAGE OF H.M.8.

CHALLENGER.

List OF THE STATIONS AT WHICH THE DIFFERENT SPECIES OF NEMERTEA
COLLECTED BY THE CHALLENGER WERE OBTAINED.

Distin-
pushing) Date. Latitude and Longitude. Pi Nature of Bottom. Species collected.
Station.
1873
45 May 3 | 38°34’ 0” N., 72° 10’ 0” W. 1240 | Blue mud Carinina grata.
47 AS 7 | 41°14 0" N., 65° 45’ 0" W. 1340 | Blue mud oA 5
a Ag 8 | Le Have Bank, N. Scotia 75 on Cerebratulus truncatus.
49 ee) 6208) 43878402 N. 163848900" W. 85 | Gravel, stones Drepanophorus lankesteri, Cerebratulus
truncatus, Cerebratulus medullatus.
June Bermuda Cerebratulus truncatus, Tetrastemma
agricola,
3 Bermuda to Azores ies Gulf weed Tetrastemma fuscum.
July St Vincent, Cape Verde Islands S60 Eupolia delineata, Drepanophorus rubro-
striatus.
1444 | Dec. 26 | 46° 48’ 0" S., 387° 49’ 30” W. 69 | Volcanic sand Cerebratulus — longifissus, | Amphiporus
MATLONE,
1874
149 | Jan. 9 } 49°8'0"S., 70°12’ 0” W. (Acces- 20 | Volcanic sand Amphiporus moseleyt.
sible Bay)
149m) 5; 21) 49° 87.108.5770> 1670" W. 80 | Volcanic sand Cerebratulus corrugatus.
06 >» 9», | Royal Sound, Kerguelen Ree Amphiporus moseleyi, Drepanophorus serra-
ticollis, Cerebratulus corrugatus.
»> >, | Christmas Harbour Cerebratulus sp. inc. (medullatus?), Amphi-
porus moseleyt.
151 | Feb. 7 | 52°59’ 30”S., 73° 33’ 30” E. 75 | Voleanic sand Cerebratulus corrugatus.
158 Mar. 7 | 50°1'0”S., 123° 4’ 0” E. naa oe Pelagonemertes rollestoni.
162 | Apr. 2 | 39°10’ 30”S., 146° 37’ 0” E. 88 | Sand and shells | Drepanophorus serraticollis.
167A} June 27 | 41° 4’ 0"S., 174° 19’ 0” E. 10 | Mud Cerebratulus parkeri, Cerebratulus angusti-
ceps.
168 | July 8 | 40° 28’ 0"S., 177° 43’ 0” BE. 1100 | Blue mud Cerebratulus angusticeps.
169 SLOW tS eS 4407 See 92.227\07 ih. 700 | Blue mud Eupolia giardii, Cerebratulus macroren,
ELupolia australis.
1875.
209 | Jan. 22 | 10° 14’0" N., 123° 54’ 0” E. 95 | Blue mud Cerebratulus sp. inc.
232 | May 12 | 35°11’ 0” N., 189° 28’ 0” E. 345 | Green mud Cerebratulus macroren, Cerebratulus sp.
inc., Eupolia nipponensis.
June 5 | 34° 58’ 0" N., 139° 30’ 0” E. off Pelagonemertes rollestoni.
Japan
1876.
821 | Feb. 25 | 35° 2’0'S., 55° 15’ 0” W. 13 | Mud Cerebratulus sp. inc.

A glance at the foregoing table shows that the very large majority of Nemertea were
captured in shallow water, and that they may, as a rule, be said to belong to the
The most aberrant new types are the pelagic Pelagonemertes, and the
genus that has come from the greatest depth, Carinina grata.

The interesting peculiarity of a strongly developed medullary nerve, which is much
less conspicuous in the European species hitherto investigated, occurs in species so widely
apart as the waters of Nova Scotia (Cerebratulus medullatus), of Kerguelen (Cerebra-
tulus sp. ine. (medullatus ?), of New Zealand (Cerebratulus parker), and of Japan (Cere-
bratulus macroren).

If we group the species according to geographical distribution, we find as novelties
in the American part of the Atlantic—

littoral fauna.

Carinina grata, Drepanophorus lankesteri, Cerebratulus medullatus, and Cere-
bratulus truncatus.

REPORT ON THE NEMERTEA. 51

Off Marion Island :
Amphiporus marioni, Cerebratulus longifissus.

Off Kerguelen :
Amphiporus moseleyi, Cerebratulus corrugatus.
Off New Zealand :!
Eiupolia giardi, Eupolia australis, Cerebratulus parkeri, and Cerebratulus
angusticeps.

Off Japan :
Hupolia nipponensis and Cerebratulus macroren.

It might have been expected that a collection of Nemertea from different parts of the
globe, preserved in spirit, would prove to be less valuable for our intimate knowledge of
genera and species, and for our elaboration of the systematic arrangement of this group, than
it would be for anatomical and histological purposes. Where external specific characters
have come to be totally effaced, the details of the internal framework remain most per-
fectly preserved for microscopic investigation. In the preceding pages we have encoun-
tered difficulty in attempting specifically to determine the fragments forming this
collection, and we have at the same time seen that only in four cases (Hupolia
delineata, Drepanophorus rubrostriatus, Drepanophorus serraticollis and Cerebratulus
corrugatus) coincident with extraordinarily favourable circumstances, was identification
possible with species already known.

That nevertheless new species could be established with certainty must merely be
ascribed to the fact that the distinguishing internal specific characters, gathered by means
of microtomy, were so marked and so divergent. Still we cannot picture to ourselves
the appearance of these new species when alive and in the fresh state.

As just noted, we have in this collection a much more reliable basis for the
study of the anatomical and histological details. We must, indeed, recognise that we
have to thank the exceedingly well-preserved collection of Challenger Nemertea for
several new facts and suggestive results, to the description of which we will now devote a

new chapter.

1 Mention is made in M‘Intosh’s Monograph (XTX., p. 96) of a New Zealand Nemertean, distinguished by Baird as
Lineus nove-zelandiz, I have nowhere been able to find any description of this species by that author. After personal
inspection of Dr. Baird’s specimen, which is preserved under that name in the British Museum, I do not, however, feel
justified in identifying with it any of the Challenger specimens from New Zealand. Externally it much more resembles
Cerebratulus corrugatus, and if this latter species is really encountered in New Zealand, Baird’s name will have to be
dropped altogether.

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ANAT OMT CAT SEN VRS i Gea PON'S:

INTEGUMENT.

By ‘“‘integument” I wish to designate the cellular layers as they are found outside
the more or less stratified connective tissue, which is known as the basement membrane.
The latter is of very varying thickness, and, for reasons to be given subsequently, will be
treated in another paragraph. Glandular structures of the integument, whether enclosed
within the cellular layers just alluded to, or stretching inwards between the muscles
and piercing a secondary basement membrane, hereafter to be described, only by means
of their communicating ducts with the exterior, will also be treated of here.

Commencing with a description of the integument of the Palzeonemertea, it will be well
to take the more important genus of which representatives are found amongst the Chal-
lenger Nemertea, viz., Carinina, as a type. This is all the more desirable as we shall here
find the central nervous system still clearly belonging to the integument, its constituents
imperceptibly merging into those of the deeper cellular layers of the skin, and also lying
outside of the basement membrane.

The two specimens of Carinina at my disposal revealed the same features with respect
to their integument, although in one of them the granular secretion in the glands that
form part of it is much more copious. When we leave out of consideration the basement
membrane, that can be easily detected in the sections by the uniform and deep red
tint it acquires by the staining reagent (picrocarmine), we can roughly distinguish four
constituent strata in the integument not in any way separated by sharp boundary lines,
but characterised by the presence of different histological elements which we will now
proceed to describe more fully. It will be understood that the absence of fresh material
and the scanty supply of spirit specimens has necessarily limited the exact discrimination
of these histological elements.

Of the four strata alluded to, the one adjoining the basement membrane is extremely
important, being the seat of those cellular modifications which must be looked upon
as the differentiation of the central nervous system within the domain of the integu-
ment. This position—it was already noticed in the description of the species given

54 THE VOYAGE OF H.M.S. CHALLENGER.

above—remains the same in the adult, and we have in this more superficial situation of
the central nervous system one of the surest indications of the more primitive position
that ought to be assigned to Carinina and the allied genera, when compared with the
other Nemertea.

The intermixture of integumentary and nervous tissue is none the less evident
in the medio-dorsal longitudinal nerve than in the lateral stems. The first named nerve,
which in former publications (IX, X) I have, not wholly adequately (cf p. 182), desig-
nated as the proboscidian-sheath-nerve, can readily be distinguished in my transverse
sections of Carinina as a delicate stem. It is not situated, as in the Schizonemertca, just
outside the circular and below the outer longitudinal muscular coat, nor, as in Drepano-
phorus, Amphiporus marioni, &c., below the basement membrane just outside the same
circular muscular coat, but it lies in this case actually outside the basement membrane,
and forms part of the deepest layer of the cellular integument. Further, a plexus-like
distribution of nervous tissue between dorgo-median and lateral nerve-stems obtains in
this species, as was more fully described elsewhere for the Schizonemertea, connecting
the three longitudinal stems and spreading round the body as a cylindrical investment.
It must be remarked that this plexus-like arrangement is thus necessarily situated in the
very layer of the integument with which we are occupied, and it may be added, that in
numerous transverse sections of Carinina the presence of fibrillar nerve-tracts in this layer
can be easily demoustrated, and these exactly resemble those that are met with in the
nervous plexus of Schizonemertea. This plexus has, since my first notice of its presence
(IX, X) been again observed by Dewoletzky (11) and other naturalists, and will be more
fully discussed in a succeeding paragraph.

The plexus here alluded to merges into the lateral nerve-stems. I may here once
more emphasize the fact that the whole system les outside the basement membrane. At
.the same time, however, the lateral stems would seem to be separated, though very
incompletely, from the integument by bundles of fibres which bind them down to the
underlying layer of circular fibres (Pl. II. figs. 7, 8.)

In the vicinity of the brain-lobes it is impossible to distinguish between the cells
of the deepest intecumentary layer and the nerve-cells. With respect to this layer I
have further to state that its nuclei are less conspicuous, its cells paler, and the boundary
lines of the latter less easily distinguished than in the other layers. Extremely delicate
fibrillar tracts were already noticed as occurring in it.

The next layer to this, when we pass outwards, is the glandular layer of the integu-
ment. It is the thickest of the four, being alone often as massive as the three others
taken together. The large, flask-shaped, and tubular glands it encloses contain a thick
granular secretion, which is partly stained brownish-yellow, partly dark red in my pre-
parations (Pl. IIT. figs. 3, 7, 8, gv; Pl. IV. fig. 1; Pl. VI. figs. 1-3). The ducts leading
to the exterior penetrate the two outermost layers. The presence in the most peripherally

REPORT ON THE NEMERTEA. 5d

situated of the two latter layers of similar though much shorter glandular cells (PE V es fioss te
Pl. VI. fig. 2, #), immediately contiguous with others of a larger size, makes it a subject
for inquiry whether these are connected by transitional forms to those larger ones which
form the layer we are now describing. This involves the not unimportant question,
whether the glands constituting this layer are or are not unicellular. While I am inclined
to accept the latter proposition, I feel that the question can only be solved by the aid of
a careful inquiry into fresh specimens.

The layer external to the glandular is one in which very numerous and deeply stained
nuclei are heaped together. These nuclei occupy several rows in one section. The same
may be said to apply, as will be indicated further on, to the corresponding layer of deeply
staining nuclei in the integument of the Hoplonemertea.

The very outermost layer bearing the cilia clearly contains, in Carinina, the same
elements as will be described more in detail (vide infra, pp. 58, 61) for the Schizonemertea,
2.e., nervous end-cells, alternating with supporting cells, “ Stiitzzellen.”

This layer, containing fewer nuclei and less granular protoplasm, is more transparent in
transverse sections, and distinguished by fine radial striz, indicating the boundary lines
between the contiguous cells. The four layers here described are not equally distinct in all
sections, nor are they equally well marked in all the sections figured. Thus, for example,
in fig. 4 of Pl. III. the glandular layer is feebly developed, and the two external layers are
so indifferently preserved that their distinctive character, just described, fails to attract
attention. The chief points enumerated can, however, even there, be easily ascertained.
The partial absence, or, at any rate, temporary indistinctness of these eland-cells in certain
portions of the integument can also be observed in tangential sections, such as the one of
Pl. Ill. fig. 8. There, too, the groups of glandular cells to the right and the left are
separated by a band of integument, in which they are decidedly absent. The same figure
shows the different ways in which the contents of these gland-cells react on staining
agents ; those to the right in this section have decidedly yellowish contents, whereas the
contents of the group on the left had a deep carmine tint.

This description of the integument of Carmina must now be followed by that of
Eupolia, the only other genus of Palzeonemertea contained in the Challenger collection.
The interesting genera Carinella, Cephalothria and Carinoma, are not represented
in those collections and certain intermediate characters displayed by these genera, which
serve to justify the identification of the different layers, which as I am going to propose
can only be touched upon as far as they elucidate the phenomena. This I will defer
till after the detailed description of the integument of Hupolia.

Instead of four layers it would not be difficult to distinguish eight in the integument
of this genus, not all of them separately and clearly represented in every section, but
sometimes (e.g. Pl. VII. fig. 5, 9) sufficiently distinct. This arrangement may be looked
upon as a further differentiation of an earlier phase, corresponding to that of Carinina,

56 THE VOYAGE OF H.M.S. CHALLENGER,

the chief difference being that the basement membrane upon which the whole integument
rests, is not here, at least not in all specimens, so clearly defined, nor comparatively so
structureless, as it is in Carinina, and as we shall again find it in the Hoplonemertea.
Moreover, identification is somewhat obscured by the appearance of a second, homo-
geneous, very thin basement membrane, which has also a strong affinity for the staining
reagent, and which we must be careful separately to distinguish, if we wish to establish
an adequate comparison between the parts in the different genera. This second basement
membrane (B, in Pl. VIL figs. 2, 3, 5, 6, 9; b, im Pl. XI. fic. 2; Pl. XIII. fig. 6) divides the
an external one, comprising the peripheral sense-cells and

integument into two strata
ciliated cells, the unicellular glands, and the layer of deeply-staimed nuclei; and an
internal one, containing the longer and more tortuous glands, the deepest integumentary
tissue, and, moreover, at least two very thin layers of fibres.

If we count the thin basement membrane alluded to for one layer, this makes three
strata externally and four internally to it—eight altogether.

The different aspects of these strata may be gathered from the figures on Pl. VI. Fig. 6
shows the three layers outside the membrane B, and though the histological elements
were not isolated, it was very obvious that large unicellular glands were here pouring
their secretion to the exterior. The very outermost layer was here, as in all Nemertea,
formed of strictly radially arranged cells, with far less distinct nuclei, whereas between
and just below the secreting cells strongly stained nuclei give to this part of the integu-
ment the peculiar radially striped appearance which it has when viewed with lower
powers (figs. 2, 3, 5, 9). This same peculiarity is only less visible in fig. 6 because
of the very copious discharge of secretion in the gland-cells. From figs. 5 and 9
it is sufficiently obvious, however, that these glands are not the only ones, but that
in the layer indicated by Gi the darkly-stained secretion of more deeply lying, larger,
and more irregularly-shaped glands is unmistakable, and is also seen to communicate
with the exterior by fine tortuous tubes piercing the superposed membranous and cellular
strata, about ten of these ducts being specially indicated in fig. 5. Their direct passage
into the respective glands is not always visible in one section, the course of the tubes being
tortuous. The same glands, though also present in the sections shown in figs. 2 and 3, are
there less marked, because the secretion has not yet so distinctly accumulated. Here, too,
the reference letters G7, point to the stratum in which we find them imbedded. A second
constituent of this stratum is seen in cells similar to the secreting cells in the unripe
stage (figs. 2, 3), but having afterwards a very distinctly vacuolated character, and
then forming the surrounding and sustaining tissue for the functional glands. They
might, then, best be designated as vesicular connective tissue (“ blasenformiges
Bindegewebe”), with hardly any intercellular substance. The comparative thickness
to which this part of the integument may attain is best understood from Pl. VII.
fies. 5,9, Gi. That there is a sharp line of demarcation between it and the gelatinous or

REPORT ON THE NEMERTEA. 57

lamellar connective tissue of the basement layer Bet, upon which the whole of the integu-
ment rests, may here be specially insisted upon, and is indicated in the same figures.

Finally, I have to mention the two layers of fibres which, though very delicate, form
in Hupolia very constant and characteristic parts of the integument. They are imme-
diately applied against the inner surface of the supernumerary basement layer B—an
outer layer of circular and an inner one of longitudinal fibres. Fig. 9 (Hupolia
delineata, long. sec.) shows them to be more conspicuous than figs. 2, 3 (Hupolia
australis). Fig. 9 moreover, serves to demonstrate that the pigment, to which in this
species the peculiar longitudinal brown stripes are due, is accumulated in the same
stratum of the integument, where these fibrous layers are found; the section represented
shows an unpigmented zone between two pigmented ones. The pigment is granular, and
appears to be limited to this stratum. It was not met with in the other species of Hupolia.

That I am justified in looking upon the integumentary arrangement of Hupolia as a
higher differentiation of a lower type, which in general resembles the integument of Cari-
nina, must now be shown by a short account of the condition of things in Cephalothrix
and Carinoma, two other Palzeonemertea, both of them inhabitants of the European seas.

Cephalothrix shows an advance in differentiation upon Carinina, by the deeper
situation of the lateral nerve-stems (Pl. XI. fig. 15), imbedded in the outer longitudinal
muscular layer. Still it deserves special attention, that in this genus the medio-dorsal
nerve is still situated in the deepest layer of the integument (Pl. XI. fig. 5) outside
of the basement membrane, and that, at the same time, the integument wholly answers
to the description that we have given of the integument of Carinina.

Carinoma, whilst generally agreeing with Cephalothrix in the situation of the lateral
nerve-stems, no longer retains the longitudinal medio-dorsal nerve as part of the integu-
ment, but in a somewhat deeper situation, enclosed in the basement-membrane. It
also shows very decided complications in the structure of the integument. Whereas the
basement layer is most closely similar to that of Carinina and Carinella, the outermost
integumentary layer is much more distinctly cellular, provided with unicellular glands,
and separated from the deeper glandular layer by the development of two layers of
muscular fibres that were first noticed by M‘Intosh (XXIV), and by him interpreted as
two accessory muscular layers of the body-wall. They are such, in fact, although I feel
confident that we may look upon them as forming an integral part of the integument,
and as being, together with it, wholly of epiblastic origin. Not wishing to give a figure
of Carinoma, which does not form part of the Challenger collection (the diagrams on
Pl. XI. may, however, be consulted), I must needs appeal to the confidence of the reader
that a glance at a transverse section of the integument of Carinomea carries with it the
conviction that it is, in this respect, truly the most conclusive intermediate form between
Carinina and Eupolia, so that we are amply justified (1) in declaring the basement
membrane (B of Pl. II. figs. 3, 4, 7; Pl. IV. fig. 1) to be not homologous with the one

(ZOOL, CHALL, EXP.—PART LIv.—1887.) Hhh 8

58 THE VOYAGE OF H.M.S. CHALLENGER.

also lettered B on Pl. VII., but to be so with the deeper layer, Bet of the latter plate ;
and (2) in comparing the glandular structures of Carinina more especially with the
deeper layer of glands of Hupolia, and in looking upon the unicellular glands of the
latter as more particularly developed in the outermost layer. These latter are then
comparable to the smaller and superficial unicellular glands which are met with in
Carinina (PI. IV. fig. 1). Similar considerations concerning the homology of the differ-
ent portions of the integument can be applied, as we shall see in the sequel, to the
Schizonemertea, their integument in so many points resembling that of Hupolia, and
being thus also linked to that of Carinina by intermediate forms, such as Carinoma.

Amongst the Hoplonemertea it is most difficult to obtain specimens in which the
integument is in a fair state of preservation. Even in the specimens that have been
treated with special care, it is a rare occurrence to find a portion of the integument in
which its different layers can be clearly made out.

From what I have noticed in the Challenger specimens, there is a certain amount of
uniformity which must first be noticed and compared with what obtains in Paleeonemertea
and Schizonemertea. Sharply distinct from the basement-membrane, which, after removal
of the integument, would even show a more or less honeycombed surface, are the deeper
cell-layers of the integument, the rounded bases of these cells fitting into the honeycomb-
like pits in the basement-membrane just alluded to (PI. X. fig. 2). These cell-layers,
with very distinct nuclei, are in thin sections many rows thick. The nuclei are, however,
never so close together as they are in the subsequent layer, which is generally situated
about halfway between the basement-membrane and the ciliated surface (Pl. X. fig. 1).
On teasing out the elements of this layer, we find long spindle-shaped cells, considerably
thinning out at the ends, and only bulging at the spot where the deeply stained nucleus is
situated. These nuclei, again arranged in several rows even in the thinnest transverse
sections, are there disposed so as to fit close between each other, the thin ends of the cells
being directed one towards the outer surface and the other towards the deeper layers
before mentioned. It cannot be doubted that sense-cells, which very generally have a
similar shape and position, are among these (cf: Dewoletzky, II). Towards the outer
surface, the remaining stratum of the integument has the peculiar radially streaked
appearance already described for the Palzeonemertea; nuclei being rarer in this layer
than in the two foregoing. Finally, the cilia are implanted upon the outer margin of
this region, and teased preparations reveal the presence of special cells with a nucleus of a
very much paler hue, and very faintly coloured. Only ina few preparations have the ciha
been well preserved; a cuticula upon which they are implanted, as elsewhere (XIV)
described in embryonic stages, was also only noticed in certain favourable sections.

These are the principal features marking the integumentary system of the Hoplone-
mertea. A few further details, however, may still be added. The deepest layer (PI. X. fig. 2)
contains fibrous nerve elements, not distinetly indicated in the figure. The absolute

REPORT ON THE NEMERTEA. 59

thickness of the layers, above described as integument, does not vary very much in smaller
and larger-sized individuals. Also, in the tip of the tail, where growth is continually
going on, and where the newly formed parts are thus, in the first instance, found, the
integument is very much in advance of the underlying tissues in obtaining its definite
size. For example, in Drepanophorus lankesteri I find the cellular integumentary layer
(the basement membrane not included) to be on the thickest part of the body, 0°15 mm.
(.e., one-twentieth the horizontal diameter in this region), and close to the tail end 0-1
mm. (7.e., one-tenth the horizontal diameter in this region). In the largest specimens of
Amphiporus moseleyi, which have more than twice the length and more than two and a
half times the transverse diameter of Drepanophorus lankesteri, I find the integument
to measure 0°12 to 0°15 mm.

Both in specimens of Amphiporus moseleyi and in one of Amphiporus marioni, as
well as in one of Drepanophorus, it is easy to demonstrate glands in the integument by
the evident presence of the secretion, partly extruding towards the exterior, partly still
enclosed between the deeper layers (PI. X. fig. 2). These glands are, however, neither so
massive, nor do they form such a conspicuous layer as in Carinina, above described.
Whether they may be regarded as unicellular, and as comparable to the superficial ones
already mentioned in the integument of Hupolia, and also present in the Schizonemertea,
or whether they are more directly homologous to the deeper glands of that division,
is for the present difficult to decide by means of the preserved material in the Challenger
collection. Histological investigation of fresh specimens will be necessary to clear up
this point. Drepanophorus serraticollis would certainly tend to a direct comparison
with the flask glands of Cerebratulus, &c. In a general way, however, the Hoplone-
mertean integument offers more analogy to the more primitive arrangement than to the
higher differentiation of the layers in Hupolia and the Schizonemertea.

One further detail deserving mention is the presence of a granular deposit (pigment ?)
in the lower cell-strata of the integument of the last mentioned specimen of Drepano-
phorus. This deposit is different from the one hereafter to be mentioned in the tissues of
Amphiporus marion. A deposit comparable to the latter was absent in the specimen
of Drepanophorus here alluded to. The granules have more resemblance to the pigment
granules of Hupolia delineata, described above, and may probably be looked upon as such.

While we see that the Hoplonemertean integument is directly connected—at least in
general outlines—with that of the Paleeonemertean genera Carinina and its allies, the
Schizonemertea are linked to the primitive stock by the intervention of Hupolia and
Carinoma,

Certain Schizonemertea (e.g., Cerebratulus corrugatus) in some portions of the
integument reveal a complete uniformity with what we have described for Ewpolia ; a
stratified basement layer separating the outer longitudinal muscle-bundles of the body-
wall from the layer of vesicular tissue sustaining the deeper skin glands, these glands

60 THE VOYAGE OF H.M.S. CHALLENGER.

communicating by tortuous tubes with the exterior, and being separated from the outer-
most eell-layers with unicellular glands by a special secondary and continuous, though
thin basement layer (Pl. XIII. fig. 6). Below the latter, longitudinal and circular fibres
proper to the integument are also present, corresponding, even in their more massive
development, to those of Carinoma.

There appears to me to be no doubt that this same arrangement holds good for the
ereat majority of Linet and Cerebratuli, and the only reason why the separation of
the parts is often less marked is the stronger development of the outer longitudinal
muscles of the body-wall, concordant with the disappearance of the connective tissue
separating the integument and body musculature, and also the fusion to a smaller or
larger extent of the longitudinal muscle-fibres proper to the integument with those of the
body-wall. From this it inevitably results that the line of separation between the
body-wall and the integument seems to be formed by the external, secondary basement
membrane, the deeper glands having the appearance of being imbedded within the longi-
tudinal muscles of the body (PI. XI. figs. 10,11; Pl. XII. figs. 2 and 10). That this
is a secondary arrangement, and that the real and original line of separation was another
one, has been demonstrated in the foregoing pages.

It is not necessary, after the detailed description of Expolia given above, once more fully
to discuss the same details for those Schizonemertea that wholly correspond to the same
type of integument. In those species in which the more developed longitudinal muscular
layer more or less effaces the boundary line between integument and muscles (Cerebratulus
macroren, Cerebratulus medullatus, &c.), the characteristic and sometimes massive layer
of vacuolated cells surrounding the deeper glands is considerably reduced. The other con-
stituent parts have retained their original character, with the exception of the thin muscu-
lar strata of the integument, which are no longer separately recognisable (PI. XI. fig. 10).

The integument is generally very completely preserved in the cephalic fissures; it
may here be noted that there, too, the deeper gland-structures of the integument may be
noticed, although they are much more sparingly set. In a few cases it would appear as
if they are wholly absent, and as if only the outer integumentary cell-layer is preserved in
the cephalic fissures ; others, again (PI. XIV. fig. 11), offer special differentiations in the
region of the cephalic fissures of the glands, which may there be united in paired accumu-
lations. I must also mention a somewhat aberrant type of integument, as we find it
represented in a Cerebratulus sp. inc. (medullatus?), from Kerguelen Island. The integu-
mentary layers offer more general resemblance to what obtains in the more prunitive
Paleonemertea (Carinina, Cephalothrix, &e.) than to Hupolia. Eventually it might be
said to retain a more primitive embryonic condition. I have at least described a develop-
mental phase of the integument very similar to what I am now about to describe for
adult forms, as occurring in the ontogeny of Lineus obscurus (XIV). The integument
in question may, however, also be looked upon in another light, 7.e., as in no way

REPORT ON THE NEMERTEA 61

more primitive, but rather as a special differentiation of the normal type of the Schizo-
nemertean integument, the result being an apparent simplification. This simplification
(Pl. X. fig. 7) consists in the absence of the deeper layer of gland-cells below the
superficial secondary basement membrane b. The whole integument of this species would
thus only seem to correspond to the very outermost layer (the layer of the unicellular
flask glands) of the other Schizonemertea. I have, indeed, the conviction, that far
from being more primitive, this condition may be linked with what obtains in other
Schizonemertea and in Hupolia by such transitional forms as Cerebratulus medullatus,
&c. (Pl. XII. figs. 10 and 2; Pl. XI. figs. 10, 11). These species have evidently well-
developed glands belonging to the deeper layer; and whilst the glands are on all sides
surrounded by the longitudinal muscles, they at the same time penetrate more deeply
into this layer, even at a few points touching the nervous stratum, which is superposed
upon the layer of circular muscular fibres (Pl. XII. fig. 10). The special character of the
integument of Cerebratulus sp. ince. (medullatus ?), and the deceptive reminiscences it
evokes of the more primitive stages of the integument may well be said to be due to the
strong secondary basement membrane. Thus in this species the layer of the deeper
glands seems to have altogether disappeared.

Before passing to another paragraph, I cannot refrain from pointing out the many
points of resemblance that may be noticed between the integument of the Polyclada,
now so well known, thanks to A. Lang’s beautiful monograph, and of certain Nemertea,
viz., those in which the integument is secondarily simplified as in those last discussed.
Our external layer of unicellular glands is evidently comparable to what Lang and Griff
eall the “ Schleimstibchenzellen” or ‘ pseudorhabdites,” and these in their turn are
compared by Lang, on very plausible grounds, with the “ Rhabditenzellen,” in which the
peculiar rod-like enclosures of the integument are found. The highly refractive, uniform
contents of what I have called the unicellular glands, their general shape and properties,
wholly coincide in their semi-viscous nature with what are described by Lang as the
“ Schleimkérper,” and looked upon by him as merging into true glandular structures.

The Nemertean layer of deep glands is also found in the Polyclada, below the
(also secondary ?) basement membrane. So is the layer of nuclei regarded by Lang as
belonging to a continuous stroma, by which both sense-cells and gland-cells are sustained
and which was recognised by me in all the subdivisions of Nemertea. The figure given by
Lang (XVI; Pl. XI. fig. 11) would fit very well for different genera of Nemertea ; only
in Nemertea the rod-like viscous bodies are not subdivided into superposed blocks. More-
over, the tactile and sensory cells in the integument, as Lang describes and figures them,
more especially for the tentacular integument, offer without doubt a close analogy to
that outermost layer of the Nemertean integument, with its triangular cells (tip down-
wards), which is also found in the vast majority of species where the skin is uninjured,
which is uniformly distributed over the body, and which, if mdeed sensory, as appears

62 THE VOYAGE OF H.M.S. CHALLENGER.

to me most probable, would go a long way to explain the high degree of sensibility of
every portion of the Nemertean body-wall.

MUSCULAR SYSTEM AND CONNECTIVE TISSUE (GELATINOUS TISSUE,
BASEMENT MEMBRANE, &c.).

In describing in the foregoing paragraphs the integument and its varied constituents,
glands, sense-cells, ciliated cells, &c., the tacit assumption has been made that the structures
there described might be looked upon as so many derivatives of the epiblast. Although
reliable embryological data are as yet very scanty, my own experience on this head
(XIV, XV) appeared to me to afford justification for this assumption. However, I agree
that the question, whether the thin layers of longitudinal or circular fibres, that, more
especially in Hupolia and Cerebratulus corrugatus (Pl. VII. figs. 5, 9; Pl. XIII. fig. 6),
form so intrinsic and conspicuous a part of the integument, are also epiblastic derivatives,
or whether they are due to mesoblastic elements, is open to dispute, and cannot be solved
for the present on any other than the a priori arguments just alluded to. Hence, if I
look upon the tissues that are treated of in the present section as essentially meso-
blastic structures, I wish it to be well understood that this distinction may after all not
be a final one.

I have purposely omitted discussing the basement membrane of the integument under
the head of the integument, because it appears to find its more natural place amongst
what we are now going to describe: the tissues between the outer cell layers and the
intestinal epithelium, 7.e., the muscular body-wall and the connective tissue (better,
gelatinous tissue, ‘ Full-Gewebe”). The latter is not only present in the space between
the body-wall and the intestine (so far as it is not encroached upon by the generative,
blood-vascular, or nephridial systems), but also between the individual muscle-bundles,
when these are not very closely applied against each other, and outside of these, between
the muscles and the integument, as the so-called basement membrane above mentioned.

The question as to the exact nature of this tissue is, in my opinion, a very important
one. It represents the tissue which in Ccelenterata fills the space between epiblast
and hypoblast, the “jelly” of Medusee and Ctenophora, with its multifarious inclusions
of muscular, fibrous, and eventually nervous nature. This jelly is the more im-
portant since its distribution, in the way above defined furnishes a strong argument for
the view, also held by me, that the Nemertea are devoid of a body-cavity comparable to
that of Arthropods, Annelids, and of Vertebrates. The only body-cavity proper to the
Nemertea is the modified segmentation cavity, the archiccelome, as I have elsewhere pro-
posed to call it (XIII, XIV). Of the cavities of the generative sacs and of the nephridia
mention will be made in the respective paragraphs.

REPORT ON THE NEMERTEA. 63

It will be well to consider this connective tissue more closely before we pass to the
description of the muscular layers of the body-wall. From the foregoing it may already
be inferred that there is a direct continuity between the different parts of this gela-
tinous tissue, be it situated close to the intestinal epithelium or to the integument, and
that this continuity is more or less completely interrupted by the muscular layers.
We may thus conclude that it will be most prominent in those species that have the
muscular body-wall reduced to a minimum, whereas it will be hardly visible in species
that have a very strongly and massively developed musculature. This is indeed the case,
Pelagonemertes offering a very striking example of the first category, Carinina of the
second,

Although the latter species is by far the most primitive, I would hesitate very much
in at the same time regarding the relation of the gelatinous tissue to the body-muscu-
lature of this deep-sea form as typically representing the original arrangement. Both
species mentioned represent an extreme; the normal starting point may be more easily
derived from what we find in Kupolia and in most Hoplonomertea. It then becomes
obvious that our gelatinous tissue, though uniform and continuous, still appears in three
principal modifications, which, however, are often connected by transitional phases having
the characteristic features of more than one of these modifications.

The first of these modifications is found between the muscles and the integument,
the second in the midst of the muscular bundles, the third between the muscular invest-
ment and the internal organs.

The first modification just alluded to appears in Carinina (as also in Carinella and
other Palzeonomertea not collected by the Challenger) as a wholly homogeneous base-
ment layer, on which the deeper cell layers of the integument are implanted, partially
honeycombing it in the way above noticed. It is strongly stained by picrocarmine, and in
Carinella traversed along circular and longitudinal tracts by nervous tissue. In Carinina
the corresponding tracts are still situated in the deeper layers of the integument itself.
Nuclei are very rare. What is a distinct basement layer in the more primitive Palzeo-
nemertea just named, retains this character with but little change in the Hoplonemertea.
One change which is revealed at first sight is a distinct though exceedingly fine stratifica-
tion, that becomes apparent in the basement membrane of nearly all Hoplonemertea.
Along with this we very often find included in the Hoplonemertean basement layer
distinct and sometimes numerous ‘nuclei. The other inclusions in it, as they are
fieured on Pl. X. fig. 1, B, appear to be parasitic unicellular organisms infesting
this particular specimen (see p. 49). Besides the exceedingly fine stratification which is
parallel to the surface of the body, and which is often thrown into wavy folds, there are
numerous radial tracts that would seem to transverse this basement layer, but are often
only due to slight differences in texture and coloration, or to hardly susceptible folding or
contraction (Pl. VIII. fig. 13). Where actual radiating fibres can be demonstrated, they

64 THE VOYAGE OF H.M.S. CHALLENGER.

sometimes are found to be extremely thin nerve-stems connecting the cellular integu-
ment with the central nervous system, whereas in other cases their spiral coiling and their
affinity for staining solutions permits us to define them as contractile or elastic fibrils. It
is, however, not to these radial fibrils that the extreme plability and continual change
in thickness of the basement membrane of the Hoplonemertea can be ascribed. This
phenomenon must be an inherent quality of the tissue itself, and may be studied in every
transverse section, where the outer boundary line of the basement membrane is only
very rarely parallel to the inner one. Generally it is strongly undulated, in accordance
with the folds and wrinkles into which the integument may be thrown, not only during
life, but also when the animal is preserved in spirit. The consequence of this undulation
is, that in several places the integument much more closely approaches the muscular
body-wall than in others, where it is kept very widely apart, the basement membrane
being in the first case compressed ; in the second, extended to its utmost limit.

Together with this extension and contraction, the fine parallel stratification changes
its aspect, becoming more coarse, and sometimes so coarse that it might be difficult not to
look upon the basement layer as composed of fibres. A confusion with subjacent mus-
cular layers would in some cases be pardonable. A comparison of longitudinal and
transverse sections reveals, however, the fact that it is indeed no fibrillar, but a stratified
condition. Another change accompanying these phenomena of extreme plasticity is the
change in colour, the staining appearing far more intense when the strata are in the
contracted than when they are in the expanded condition. The nuclei remain visible in
both cases. How the change of shape and the successive expansions and contractions
are actually brought about in this homogeneous though laminated tissue, which has more
the appearance of being intercellular ground substance than anything else, must here
remain an open question, which we shall again meet when treating of the contractions of
the muscular body-wall.

In Pl. VUI. fig. 13, and Pl. X. figs. 1, 2, different aspects of the Hoplonemertean
basement membrane are given. I will now pass to those of the Palzeonemertean genus,
Eupolia, that in so many respects leads over to the Schizonemertea. In certain speci-
mens of this genus an arrangement, more or less corresponding to what has just been
described, was in a few cases met with, the basement membrane being of about the same
thickness all round, finely striated, with imbedded nuclei, and sharply separated from the
integument (Pl. VIL figs. 3, 9, Bet).

In other cases the membrane separating the muscles and the integument is much
more folded, more irregularly striated, and less characterised as a separate band of distinct
tissue (Pl. VII. figs. 2, 5, Bct; Pl. X. fig. 6, B). Especially in these latter cases it is
quite clear that this band of tissue, to which the name of basement membrane can only
be applied with particular restrictions, imperceptibly passes into the connective tissue
found between the longitudinal muscular bundles of the outer layer, where it is moulded

REPORT ON THE NEMERTEA. 65

between these bundles, and also carries in the nephridial regions the terminal deferent
portions of the nephridial ducts (Pl. VII. fig. 5, Nep). The originally cellular nature of
this connective tissue is retained in the head and in the anterior portion of the trunk,
where the outer longitudinal layer of muscles is not less thick, but certainly contains a
very much smaller number of fibres, because of the permanence of the intermuscular
cellular stroma just alluded to. A comparison of figs. 2 and 3, Pl. VIL, the one taken
through an anterior, the other through a more posterior region of the trunk of a Ewpolia,
will elucidate this, as will also the comparison of fig. 5, Pl. VII., with the more enlarged
fig. 6 of Pl. X. (taken from the same specimen), which represents a section through the
region marked #ct in the former figure situated further forwards, and thus decidedly cellular
as far as concerns the intermuscular tissue. One important fact is clearly mdicated in this
latter figure, viz., that the cells situated between the muscle bundles of the outer longi-
tudinal layer (y.v/), although their general aspect, vacuolation and arrangement very
much resemble that of the similarly vacuolated cells of the deepest layers of the integu-
ment (Jdvl), may nevertheless be immediately distinguished from these by their much
larger nucleus. The same fact follows quite as unmistakably, though somewhat less clearly,
from Pl. VII. fig. 2. It gives some support to the hypothesis, that the whole of the deeper
cell-rows of the integument, vacuolated or otherwise, being substantially different from
the subjacent mesoblast cells, may be looked upon as epiblastic. However, this question,
which pertains more to an ontogenetic than to an anatomical investigation, may safely
be left out of further consideration. This basement tissue of Hupolia, much less
regularly arranged than in Hoplonemertea and in the Carinellidee, is thus still directly
homologous with that of the latter.

A secondary external homogeneous basement layer is found immediately below the
outer stratum of unicellular glands of the integument ; in the paragraph devoted to the
integument the comparison with Carmina, Carinella and Carinoma has been already
instituted, and it was at the same time shown in what way these different arrangements
may be identified with one another.

In the anterior portion of the body the stratified basement layer Bet (Pl. VIL) fuses
with the sparse intercellular tissue that is present round the vacuolated cells, and
appears to be a direct continuation of it. In the posterior portion, however, where the
muscular bundles are more strongly developed, this stratified tissue appears more limited
to the region between the muscles and the integument, principally because here the
character of the intermuscular tissue is also changed and becomes more homogeneous,
although it is here and there traversed by radial fibres, is also provided with nuclei, and
contains numerous nerve-tracts. The general aspect, and the effect of the staiming
reagents, show this intermuscular tissue to be identical with the homogeneous,
more or less gelatinous tissue, that is observed between the outer longitudinal
bundles of Carinina (PI. Hl. fig. 6). The cells, of which traces are found

(ZOOL, CHALL, EXP.—PART LIv.—1887.) Hhh 9

66 THE VOYAGE OF H.M.S. CHALLENGER.

around the nuclei contained in this homogeneous intercellular substance, show a very
delicate granulation, and it is often very difficult to decide whether a given one
belongs to the nervous network, or whether it is a more indifferent cell, appertaining
to the gelatinous ground-substance. In the former case the connection with the nerve-
plexus is of great advantage in the decision, and but for this such a decision would often
be wholly impossible. The fibres generally offer less difficulty, the delicate nervous fibres
being. sufficiently distinct from the elastic or contractile fibrils. The intermuscular
homogeneous tissue of Hwpolia, and its inclusions in the region somewhat behind the head,
are figured in Pl. VII. figs. 4, 5. In its deepest part, immediately surrounding the
circular muscular layer, we find the nervous stratum, that will be more fully discussed
further on. We must mention this, because in certain of the Schizonemertea (Pl. XII.
fiz. 10), to whose basement membrane and intermuscular tissue we have now to direct
our attention, glandular structures belonging to the integument reach as far down as this
layer ; a factor which we have to keep well in view when discussing the tissues to which
this paragraph is devoted. This is all the more necessary, because in that case the other
deeper cellular components of the integument are reduced in number, whereas the
outer longitudinal muscular layer having become more compact and dense, the imter-
vening region between these two, the region Bet of Pl. VII., has vanished from view.
The secondary basement membrane (#) is then the sole representative of such a
structure, and might easily, but as [ hope I have demonstrated, imjudiciously, be
looked upon as homologous with the basement membrane of Carinina, Carinella, &e.
(Ge PLS):

An arrangement of the basement membrane, wholly comparable to what we have
deseribed in Hupolia, is found in such Schizonemertea as Cerebratulus corrugatus
(Pl. XIII. fig. 6, Bb). In most of the others the strongly developed and massive
outer longitudinal muscular coat so much encroaches upon the deeper layers of the
integument in the way just noticed, that it is no longer possible clearly to distinguish
between the two integumentary muscular strata (J7em) and the subjacent one constituting
the body-wall (y). The extreme representatives of this development are figured on Pl. X.
fig. 7, and Pl. XII. fig. 10.

We now resume our examination of the gelatinous tissue, which we have as yet
only examined as subintegumentary basement membrane (Carinina and Hoplonemertea),
or also as intermuscular substance (Hupolia and Schizonemertea) in its further partici-
pation in the muscular investment. In the cireular and inner longitudinal layers gela-
tinous intermuscular tissue is unmistakably present, and its presence is revealed both by
the nuclei and by its peculiar homogeneous appearance, but at the same time, owing to
the far greater compactness of these last named muscular layers, when compared with the
outer longitudinal one of Hupolia, the position of the connective jelly is much more sub-
ordinate, and its presence less easily demonstrable. Still it may be observed in the larger

REPORT ON THE NEMERTEA. 67

species that, besides the distinctly granular cells included in it, striation in nearly every
direction forms a prominent feature of this intermuscular substance.

Inside the innermost muscular coat the gelatinous tissue appears in the third modifica-
tion which we have established for it. This modification is in many respects the most im-
portant, and at the same time most liable to a considerable amount of variation according to
the species we happen to examine. It has been already noticed that of all Nemertea Pelago-
nemertes shows it in its fullest development, whereas the eminently muscular Carinina is
only very sparsely provided with it. It will thus be safest first of all to examine it in
Pelagonemertes, and to indicate by what features the other genera differ and gradually
lead to grades of development as far down as Carinina.

The most striking feature in examining any section of Pelagonemertes, either with
low or high powers, with a special view to the gelatinous tissue inside the muscular body-
wall, is the homogeneity of this tissue, the comparative scarceness of nuclei, and the
uniform imbibition of the staining reagent, by which it has obtained a delicate rose colour.
A comparison with the medusoid jelly, or, more distantly, with the intercellular substance
of cartilage, is here inevitable.

This general feature being established, the secondary characteristics are—(1) the
imbedded nuclei of this jelly; (2) the fibres forming part of its substance, other fibres tra-
versing it in apparently tubiform channels; (3) differences in the coloration of the jelly in
different regions, and lastly, a fibrillation of the utmost tenuity, only visible by the aid
of very high powers, which appears in different regions of the apparently homogeneous
jelly, other and large portions, however, retaining the homogeneous aspect even with
these high powers, though then not appearing wholly limpid but cloudy, perhaps an indi-
cation of a yet finer fibrillation escaping the analysing power of our objectives when
studied, not in the fresh state, but in Canada balsam.

The different coloration of the jelly in different regions is partly arbitrary, 7.e., darker-
coloured patches are irregularly seattered throughout the general lighter hue. At certain
places the darker staining is, however, constant, viz., contiguous to those regions where
the jelly is interrupted. Thus the channels above alluded to, in which nerve-fibres and
others take their course through the jelly, are marked by a double boundary line of
darker colour (PI. VIIL fig. 6, 7”), corresponding to the tract along which the continuity
of the jelly is interrupted for the passage of these fibres. These nervous tracts being
exceedingly numerous, the transversely or obliquely cut ends of similar distinctly red tubes
are discovered in every section (Pl. VIIL. fig. 3). Moreover, all round the two principal
nerve-stems (figs. 6, 8), and bounding the cavity of the proboscidian sheath (Pl. VUI.
fiz. 12, B), the blood spaces (fig. 8, bl), and the cavities in which the generative products
are lodged (fig. 8), the same continuous dark red tint, which that portion of the jelly has
acquired by the picrocarmine, is observed.

A peculiarity which I have further to notice in the sections, is the different hue that

68 THE VOYAGE OF H.M.S. CHALLENGER.

has been acquired by two superposed layers of the basement membrane of Pelagonemertes
(Pl. VIII. fig. 18, B, B’); the outer one being darker than the inner. I have no
explanation to offer of this phenomenon, nor of the fact shown by the same figure
(Pl. VIII. fig. 13) that the same phenomenon is repeated just below the basement
membrane, the jelly between the bundles of longitudinal muscles being much darker than
that which is found inside. The latter, into which the former gradually merges, is not
specially indicated in fig. 13. Mention ought here to be made of what is marked dy in
that figure, and what appears to be im several cases (PI. VIII. fig. 5) a central cavity
enclosed by peculiar cells, of which the nuclei are specially distinct. I must leave it
undecided whether these structures, radially directed towards the surface of the body, are
the same as the masses dr (Pl. VIII. fig. 4), which I see in a glycerine preparation of the
integument made by Professor Moseley on board the Challenger from the fresh animals,
and also whether these structures might be looked upon as glandular, and comparable
to similar gland-masses in the jelly of Amphiporus moseleys (Pl. XV. figs. 11, 12).

That the course of the fibrils traversing the jelly is in no way strictly limited to
certain directions, but that we find them now parallel to the proboscidian sheath, now to
the intestinal wall, now convergingly directed against the generative ducts, is sufficiently
demonstrated in Pl. VIII. figs. 3,8. A very large number are, however, radially directed
towards the surface, and though it was not observed in one section, it might perhaps be
possible to find dorso-ventral fibres uniting both surfaces. That the nerve-stems, spring-
ing from the lateral cords N (Pl. VIII. fig. 3), are indeed encased in a tubular space
bounded by darker stained gelatinous substance, is best seen in fig. 6 of the same plate,
as well as the fact that in the immediate neighbourhood cells and fibres (f) form part of
that substance.

In the other Hoplonemertea this continuous jelly, though much less prominent, has
very much the same character as in Carinella, with the exception that no special tubi-
form tracts for the passage of nerves, &c., are as distinct as they are in Pelagonemertes.
The passage of radial fibrous tracts through the gelatinous tissue is, however, everywhere
demonstrable (Pl. X. figs. 1, 2), as is also the origin of these fibres out of cells (Pl. X. fig. 2),
and the continuity of the gelatinous stroma with that contained between the muscular
bundles of the body-wall. The Challenger Nemertea not offering anything very special
in this respect, I will postpone a more circumstantial discussion of this tissue for the
monograph which I am preparing for the Naples series.

Similarly I may rapidly call to mind that, in the Schizonemertea, where this gelatinous
substance is best observed in the posterior region of the body, and better in large speci-
mens than in small ones (PI. XV. figs. 7, 10), it offers the same characters. Anteriorly, where
the cireumeesophageal blood-space is present, it does not play any conspicuous part ; pos-
teriorly, however, it carries not only the tubular continuations of this space (the three longi-
tudinal blood-vessels) but also the other internal organs, to all of which it is closely applied.

REPORT ON THE NEMERTEA. 69

Here, again, its generally homogeneous character, with the addition of the same
cellular and fibrous inclusions (intermediate stages between the two being similarly
represented) as were noticed above, gives it an aspect similar to the corresponding tissue
in the other groups of Nemertea.

It cannot be denied, and has been already noticed above, that from a morphological
point of view there are certain strong points of resemblance between the gelatinous tissue
of the Nemertea and the jelly of the Meduse. I was very desirous to know whether this
would also apply to the chemical constitution, and owing to Professor Krukenbere’s kind
aid Tam now able to make definite statements on this head. Having sent him a small
quantity of the Nemertean jelly, he kindly examined it and writes as follows :—

“Tn accordance with your desire I have attempted, as far as it is possible, chemi-
cally to solve the question, whether the jelly of the Nemertea is more closely allied to
that of the Medusz or to the collagenous substances, such as I have with certainty
demonstrated in Sipunculus nudus (Vergl. physiol. Studien., i. 1882). As collagenous
tissue is digested by trypsine, on/y in case of its having before been treated with acids
or been boiled with water (Ewald and Kiihne), I tested the reaction of the Nemertean
jelly towards this ferment. It proved to be very easily digested by trypsine, and would
thus have to be regarded as a true proteid substance. Wholly in accordance with this
result is the intense red colour which the tissue acquires when boiled with Millon’s
reagent ; whereas, on the contrary, tissues that contain more collagen are only faintly
stained, and pure collagen is not stained at all by Millon’s reagent. Moreover, the
Nemertean jelly is not acted upon as are the collagens (‘leimgebendes Gewebe’) by
boiling water, nor does it furnish, when treated with diluted acids and soda, such reducing
solutions as are the so-called mucins (Hyalogene, mihi). The Medusa-jelly consists of true
proteid bodies. A similar substance is the vitreous body of the eye of vertebrates, and
I am thus fully prepared, after the experimental results obtained, to agree with you in
regarding the Nemertean jelly as an analogous product to the jelly of the Meduse, and
similarly of an albuminoid nature.”

We now pass to a discussion of the muscular layers. We will first discuss the general
distribution of muscular tissue, and reserve histological remarks for the conclusion.

In discussing the muscular layers of the body-wall of the Nemertea, considerable
confusion still obtains in the writings of most of the older authors, and I must confess
that it took me a long time to see my way to a safe basis of comparison of the layers,
that may sometimes be only one, sometimes no less than five in number, three or two
being also very common occurrences. An outline of the homologies of the muscular layers
was given by myself in the article Nemertea in the recent edition of the Encyclopedia
Britannica, and in the views there propounded I have no changes to make, only certain
further additions have been rendered possible by the aid of the Challenger material.

1 Krukenberg, Vergl. physiol. Studien., ii., 1 Abth., pp. 23-84.

70 THE VOYAGE OF H.M.S. CHALLENGER.

In all Nemertea, to whatever order or genus they may belong, there is one muscular
layer that is always present. This layer may, indeed, be looked upon as identical through-
out the whole series, and consists of longitudinal muscle-fibres. It is the longitudinal
layer of Cephalothriz, in which genus definite or conspicuous circular layers sometimes
appear to be absent (Pl. XI.); it is the only longitudinal layer of the Carinellidee—the
longitudinal layer of muscle-fibres in the integument of Carinoma not being here taken
into account, as indeed belonging to another system—and it is the so-called inner longi-
tudinal layer of Polia, Valencinia, and of all Schizonemertea. In Pl. XI. this layer has
uniformly been lettered a. I hold it to be the most primitive of all the Nemertean
muscular layers, both on account of its constant presence and on account of the fact that
in the posterior region of the body, where growth in length of the animal takes place, it
often appears before the other layers that are present in addition to it in the anterior
region of the body.

The layer second in importance to it (morphologically speaking) is a layer of circular
fibres marked 8, of very varying thickness, and which in the Carinellide and the
Hoplonemertea is immediately subjacent to the basement membrane, and external
to the layer a. The very outermost fibres of this circular layer often take a differ-
ent course, making an angle of about 45° with the longitudinal body axis, instead of
being perpendicular to it. This, then, being the case in two directions, a decussation
of this exterior portion of the layer, especially in Hoplonemertea and Carinellide, is
often noticed.

Outside of the circular layer 8 there is in the Schizonemertea and in Polia and
Valencinia the outer longitudinal layer y, sometimes exceeding in thickness the two
layers just noticed, and offering very varying conditions as to the compactness of its
bundles. In most cases it remains entirely distinct from the two thin epiblastic muscular
layers (see pp. 57 and 60) that make their first appearance in Carinoma, and are very
generally present in Polia, Valencinia, and the Schizonemertea (Pl. VII. figs. 5, 9, ef;
Pl. XII. fig. 6, Zvem). In some of the latter, however, a fusion occurs between the
outer bundles of the longitudinal muscular layer y, and those that are decidedly of
integumentary origin and significance, as was already noticed in discussing the integu-
ment. It needs no explanation that these latter species offer more difficulties in rightly
interpreting the relations between muscular system and integument than many others
(Pl exe fies Lexie tie, 10);

The difference in compactness just alluded to is often dependent upon the degree of
development of the deep glandular layers of the integument. Sometimes these glands
penetrate the whole depth of the muscular layer, reaching as far down as the nervous
stratum (PI. XII. figs. 2, 10); sometimes the muscles are kept further apart by the
gelatinous ground substance, as was more fully discussed in a preceding paragraph.
Eupolia may on the whole be cited as an example in which the degree of compactness of

REPORT ON THE NEMERTEA. 71

this muscular layer remains at the lowest level (Pl. VI. figs. 2,5), in Cerebratulus
corrugatus I found it very compact, and composed of very delicate fibres (Pl.
XIII. fig. 6).

Another additional muscular layer, which is not found in all but only in certain
Nemertea, is marked 6 in the figures of Pl. XI. Itis an inner circular layer, and in the more
primitive types (Carmina, Carinella, and Carinoma) it may even become exceedingly
massive. It is directly applied against the longitudinal muscular layer a; it forms at the
same time the dorsal wall of the proboscidian sheath, the exceedingly thin ventral wall of
which is in these species formed by fibres of the same inner circular layer that branch off,
and are directed inwards between the space for the proboscis and the cesophagus or intes-
tine, thus creating a floor to that proboscidian space. The inner circular layer is continued
ventrally, and embraces the other internal organs as well. In Carinoma, where the
layer has such a considerable thickness in the proboscidian and cesophageal region, and
where it has disappeared in the posterior region of the body, leaving only the longi-
tudinal and outer circular layers, the conclusion is of course tempting that the special
development of this layer is in a certain functional connection both with proboscis and
cesophagus. And if we then find that in the Schizonemertea this layer is absent, but
that, on the other hand, there is a circular muscular coat to the proboscidian sheath and
that this sheath has been raised to greater independence, and remains dorsally connected
with the rest of the muscular body-wall in exactly the way it would be if it were the
modified remnant of a restricted portion of the inner circular layer, we are led to the
further hypothesis that these two may indeed be homologous. Thus all the transverse
sections of the dorsal body-wall of Schizonemertea on Pl. XI., were they to be completed
by adding the circular muscular layer of the proboscis-sheath immediately applied against
them in the median line, would very strongly resemble the figures given of Carinoma
and Carinina.

I will not at present venture to decide whether any of the muscular layers of
the cesophagus, noticed both in Hupolia and Cerebratulus (Pl. VI. fig. 9, oe.m; Pl. XII.
fig 6, mto), may also be looked upon as derivatives of this inner circular layer, but will
only add that in Hoplonemertea such a musculature is hardly developed; whereas, on
the contrary, the circular muscles of the proboscidian sheath have attained a very high
importance, and are even more independent of the dorsal muscular body-wall than they
are in Schizonemertea (Pl. IX. figs. 1-9; Pl. X. fig. 1).

Here, too, I would be tempted to hazard a comparison between the absent inner
circular layer and the musculature of the proboscidian sheath,

The detailed histology of the Nemertean muscular system is hardly in its place here,
and may perhaps be more fitly reserved for the monograph that will shortly appear
in the Naples series.

One point must, however, be mentioned, as its definite establishment seemed im-

72 THE VOYAGE OF H.M.S. CHALLENGER.

portant to the Hertwigs,! viz., the question whether the delicate longitudinal fibres
composing the longitudinal muscular layers, and which in transverse sections are often
arranged in rings (PI. IIT. fig. 6; Pl. XIII. fig. 6), have their matrix cells between them
or not. Having very often succeeded in demonstrating an evident nucleus in the midst
of this ring of cut fibres, and having constantly observed a difference in the effect of the
staining reagent upon this central space and upon the connective tissue surrounding the
muscle bundles, I must answer this question in the affirmative.

Finally, two points deserve a short notice in this place. First, that the layer a
of the longitudinal Nemertean muscles is very often separated into two, a right and a left
half, by a dorso-median, sometimes also by an additional ventro-median solution of con-
tinuity. It is very marked in the primitive Paleonemertea, especially in those cases
where this layer is the preponderating component part of the body musculature (cf.
Pl. XI.); it is very rarely wholly absent in Lupolia and the Schizonemertea ; it is less
marked or even absent in the Hoplonemertea. In how far this separation may have
general morphological significance, will be discussed in the chapter devoted to general
considerations.

The second point on which I shall offer speculative remarks in that chapter (cf p. 127)
has again reference to the same muscular layer. Sometimes it was observed that in this
layer darker patches of contracted fibres alternate with hghter ones in which these
contractions were absent (Pl. XV. figs. 9,10). As this phenomenon of contraction was
not wholly local but stretched all round the body in rings, the question must be considered
whether we have here successive waves of contraction preserved at the moment of death,
or whether the phenomenon has a deeper significance, is more permanent and indeed
allows of direct comparison with myotomes. The comparative rarity of the phenomenon
for the present prevents us from very emphatically advocating the latter view.

How the circular layer of the Schizonemertea only stretches to the posterior brain-lobes,
how the longitudinal muscles decussate in all directions m the head, how the develop-
ment of the cephalic musculature is ontogenetically separated from that of the body
musculature, are points already known to former investigators of the anatomy and
embryology of the group. The fact of their having found ample discussion and mention
m other monographs, and the Challenger material not having furnished new points of
interest, will explain my silence in this Report on these and other points (such as the
muscular dissepiments, the musculature of the cephalic slits, &c.) connected with the

muscular system.
! Die Celomtheorie, p. 37.

REPORT ON THE NEMERTEA.

“I
ee

NERVOUS SYSTEM.

With respect to the nervous system, I am indebted to the Challenger collection for
very valuable additional data. In former publications (IX, X) Ihave dwelt at length
on the peculiar arrangement of nervous tissue in the Nemertea as I had found it to exist
in specimens that were obtained at Naples; I am now enabled to give a more exhaustive
description of this important system, and will commence by a short account of certain
points in the latest investigations into the nervous apparatus of the lower forms of animal
life, in order the better to explain the bearing upon questions of general morphology
which the arrangements as we find them in the Nemertea may happen to have.

The general and important conclusions arrived at by Kleinenberg in his classical
Memoir on Hydra, conclusions which have since found their way into handbooks and
textbooks as Kleinenberg’s Theory of the neuro-muscular cells, have of late years been
emendated by O. and R. Hertwig. These investigators have propounded a general hypo-
thesis on the phylogenetic development of the nervous system, which in their treatise
Das Nervensystem und die Sinnesorgane der Medusen (Leipzig, 1878), is formulated

(p. 170) as follows :—

: “We assume that in all Metazoa the ectoderm from which the (animal) nervous
system, with its motor and sensory terminal apparatus, has originated, was primitively
constituted of a simple layer of homogeneous cells in the same way as may be
noticed everywhere in the earliest ontogenetic stages. We further assume that these
cells, or at least part of them, have at an early period entered into mutual connection
by protoplasmic processes, and have thus formed a more closely connected cell-stratum.
According to our hypothesis, and on the principle of division of labour between the cells
thus connected, there has been gradually developed a primitive nerve system out of
this connected stratum. Whilst certain of these cells secreted contractile substance,
others were provided on their surface with tactile hairs, and a third set acquired very
numerous connections, the simple epithelium cells of the one-layered ectoderm thus
becoming gradually and more or less simultaneously differentiated into epithelial muscle-
cells, sense-cells, and ganglion-cells. Their protoplasmic connections, modified into
specific nerve substance, have part passu become converted into a plexus of nerve fibrils.
When, later on, the ectoderm became constituted of more than one layer, the ganglion-
cells were the first (of all the three elements just mentioned) to separate from the
surface epithelium and to acquire a deeper situation.”

Balfour, in his Comparative Embryology (vol. ii. p. 333), accepts the leading features of
this important hypothesis, partly substituting it for the earlier suggestion of Kleinenberg.

The latter, in his latest publication,’ revindicates his original theory against the

1 Zeitschr. f. wiss, Zool., Bd. xliv. p. 204.
(ZOOL. CHALL, EXP.—PART LIv.—1887.) hh 10

74 THE VOYAGE OF H.M.S. CHALLENGER.

Hertwigs’ objections, and maintains that these naturalists have furnished arguments in
favour of his hypothesis rather than of their own interpretation (loc. cit., p. 205). Kleinen-
berg holds that the naked nerve-cells of Hydra, that are in mutual and direct communica-
tion, may transmit a stimulus by contact without the intervention of a delicate network
of inter-cellular protoplasmic threads forming a network. He, moreover, holds that the
epithelial cells had all of them the double significance of nerve-cells and muscle-cells, 7.e.,
were true neuro-muscular cells before further division of labour set in, whereas the
Hertwigs maintain that this division of labour took place between epithelial cells that were
not yet physiologically so far differentiated.

A nerve plexus, which covers a very large surface, was actually demonstrated by
the brothers Hertwig not only in Actinia and other Coelenterata but also in the
Cheetognatha. Of the latter O. Hertwig says :‘—

“ By the fact of the nerve-fibres crossing and decussating in the most complex and
diverse ways, there is formed a nerve plexus which spreads over the whole surface of the
body, and in which the above described nerve-stems represent the single collecting tracts.”

A more or less similar plexiform arrangement of nerve-tissue has since been demon-
strated in nearly all the lower groups of invertebrates, Annelids*? and Arthropods
excepted. Thus in the works of Lovén, Greeff, Teuscher, Ludwig, and Carpenter the
nervous system of the Echinoderms is described as offering many analogies with the type
propounded as the most primitive by the Hertwigs.

Nemertea, Turbellaria, Trematodes, and Cestodes can now be very fully compared, as far
as their nervous system is concerned, with Hertwig’s starting point, when we consider the
results obtained by myself (IX, X)—which were afterwards confirmed (II) by Dewoletzky
—for Nemertea; by Lang, Graff, and Pintner for Turbellaria, Trematodes, and Cestodes.

Among aberrant forms one of the most striking examples of a thick epiblastic nerve-
plexus with longitudinal collecting tracts is offered by Balanoglossus, as described by
Spengel and more lately by Bateson. We shall have occasion again to refer to this
interesting nervous system further on.

For Mollusca, remnants of a more or less plexiform arrangement were found to exist
in the Amphineura by myself* (Proneomenia) and by Haller‘ (Chiton), and also in other
groups of Mollusca by Semper,’ Simroth,° and others.

1 Die Cheetognathen, p. 34.

? Lately Fraipont (Archives de Biologie, 1884, p. 274) has demonstrated the presence of an intermuscular nervous
plexus in Polygordius, Protodrilus, and Saccocirrus, and thus opened the possibility of also bringing the Annelids within
the region of comparison so far as this point of their organisation goes. Bergh describes a nerve-plexus in the larval
Aulostoma (Arbeit. Zool. Zoot. Inst. Wiirzburg, Ba. vii. p. 238). As to Arthropods there are facts which also point in the
same direction, ¢.g., that Hoek mentions “a continuous network of ganglia and nerves” on the inner surface of the in-
tegument in Pycnogonida (Zool. Chall. Exp., pt. x. p. 116).

3 Niederliind. Archiv f. Zool., Suppl. Band, 1881. 4 Zool. Anzeiger, No. 76.

® Archiv f. Mikr. Anat., Bd. xix., p. 124, 1877; Arbeit. Zool. Zoot. Inst. Wiirzburg, Ba. iii., 1877.

6 Zeitschr. f. wiss. Zool., Bd. xxxii. p. 304.

REPORT ON THE NEMERTEA. 75

For Vertebrates a plexiform arrangement is known to exist in the embryonic stages
of Amphibia, since the researches of Remak and Stricker, and has lately been fully com-
mented upon by Geette and Baldwin Spencer.

The last writes :'—“ There may be said to exist in the Amphibian embryo a complete
superficially-placed nervous sheath, out of which not only the central nervous system but
all the sense organs of both head and trunk are formed, and which gradually disappears
as these reach their full development.” And further on :—‘“ Along certain lines the cells
of the nervous layer proliferate, and it is by this proliferation that the rudiments of the
cranial nerves are laid down” (cf. p. 183).

The significance of this plexiform arrangement of the embryonic Vertebrate nervous
system will be discussed in the chapter devoted to General Considerations, and also the peri-
pheral plexus of the adult Amphioxus, which lately has been more fully described by Rohon.”

Hence, since my former publications above cited, the necessity has grown more and
more obvious of not looking upon the brain-lobes and the lateral nerve-stems of the
Nemertea as the nervous system, but, though recognising their significance as more highly
developed centres, to admit the presence of a most complicated and intricate network of
nerve-tissue, originally—and in the more primitive species still—belonging to the
integument. This network is most fully developed in the Schizonemertea. In Carinina
its situation in the integument makes it more difficult to observe; still I succeeded in
demonstrating it both here (cf p. 54) and in the other Carinellidz, In the Hoplonemertea
the plexus has been replaced for the greater part by distinct nerves, of which the majority
show a metameric arrangement.

We will now pass to a more detailed description of this network, thereby purposely
inverting the natural order by reserving the centres for the last. This apparent dis-
crepancy disappears, however, when we look upon the network as the most ancient
nervous arrangement, in which the centres have only gradually come forward.

When once the eye has been trained by repeated observation to notice this particular
nervous tissue of the Nemertea, it is comparatively easy to distinguish it from the
surrounding tissue. The peculiar punctate striation, the yellowish tint of the fibrous
elements, the very pale carmine hue of the nuclear ones, immediately reveal the presence
of nerve-tissue in sections, longitudinal or transverse, that have been made through

specimens stained with picrocarmine.

And when we take for our starting point, and as a basis for further description, one
of the Schizonemertea of the Challenger, e.g., Cerebratulus corrugatus (PL. XIVe tess; 4:
Pl. XIII. fig. 6, pl), we observe in all transverse sections that the two lateral nerve-stems
are in continuous connection with each other by nervous tissue that spreads out all round
the circular muscular layer 8, both dorsally and ventrally. Immediately outside of

1 Some Notes on the Early Development of Rana temporaria, Quart. Jour Micr. Sci., Suppl., 1885.
2 Denkschr. d. k. Akad. d. Wiss. Wien (math.-nat. Cl.), vol. xlv.

76 THE VOYAGE OF H.M.S. CHALLENGER.

this nervous layer the longitudinal muscular coat y is situated. There is, moreover,
present a third longitudinal nerve-stem, also situated, as are the two lateral ones, in this
plexus, but medio-dorsally in the vertical plane that passes through the animal. It is
this nerve which I have in a former publication (IX) proposed to call the proboscidian-
sheath nerve, but of which I will, in the chapter devoted to General Considerations, offer
a modified interpretation (p. 131) and which I will henceforth call the medullary nerve.

The nerve-plexus uniting the three longitudinal nerve-stems, as a cylindrical coat of
tissue between the longitudinal and the circular layers of muscles, cannot be separated or
spread out flat, nor can we succeed in getting horizontal sections of it, just because of
this cylindrical curvature. A portion of it may, however, be contained in the few
consecutive sections passing in a horizontal plane through the medio-dorsal nerve or
elsewhere, tangential to the cylindrical surface of the nerve-plexus.

From such horizontal sections figs. 2, 3, and 4 of Pl. XIII. and fig. 1 of
Pl. XIV. have been taken, and where the plexus (n. pl) is touched right and left of the
medio-dorsal nerve m, it has wholly the appearance of a dense network, the meshes of
which are more especially due to the fact that radial bundles of contractile tissuae—by
which the muscular layers and the integument are held together, and which may even
pass from the dorsal to the ventral body-wall of the animal—pierce the nerve-plexus.
The longitudinal dorsal nerve stands out very boldly in the midst of the plexus. It
is extremely important, and may be verified in any other surface section of the nerve-
plexus, that from this dorsal nerve spring, both right and left, at more or less regular
distances, thicker tracts of nerve-tissue (tr. 7.), also forming part of the plexus, but being
straight instead of tortuous, and having altogether the character of metamerically arranged
nerve-stems that are not yet recognisable as independent structures, but that are fairly
on the way to special differentiation as so many chief conducting tracts of nervous
energy in the midst of the plexiform nervous tissue which binds them together.

The presence of these transverse stems may also be noticed in transverse and longitu-
dinal sections as a local thickening of the plexus, but as the whole stem is rarely attained
in one transverse section, this thickening may be followed in consecutive sections, and is
found stretching from the medio-dorsal down to the lateral nerve-stems.* How far these
transverse stems may be said to be metamerically arranged, everyone may judge for
himself by consulting fig. 1 of Pl. XIV. The chief tracts are certainly symmetrical,
2.€., spring from the longitudinal dorsal medullary nerve at opposite points, and about

the same distance may also be seen to separate each successive pair from the foregoing,
Other transverse bundles, some thinner, some thicker, some more obliquely placed, &c., but
all similarly forming part and portion of the plexus, are, however, visible between the

1 Von Kennel, who has so considerably advanced our knowledge of the Nemertea, appears to have observed, as early
as 1879 (Die in Deutschland gefundenen Landplanarien, p. 39), the presence of certain of these transverse dorsal
nerve-stems (commissures, v. Kenn.). He did not, however, notice or describe the nerve-plexus, nor the fact of the
existence of a ventral connection, both by means of the plexus and of ventral metameric stems.

REPORT ON THE NEMERTEA. Ute

principal ones, and it is this fact that more or less obscures the metamery here alluded to
(Pl. XIII. figs. 2, 4). This metamery in the nervous plexus is of the same character as
the metamery that is noticed in the intestinal arrangement, in the nephridia, in the
generative organs, and in the blood vascular system of the Nemertea; it may indeed be
called incipient. To its significance, for the important question of the origin of seemen-
tation, we shall have occasion to return by and by.

Amongst the forms in which I found the metamery to be very distinct, Cerebratulus
angusticeps stands foremost (Pl. XIV. fig. 1). And I must here call attention to the fact
that the transverse stems here described are not only dorsally, but also ventrally, most
regular and conspicuous, uniting the longitudinal nerve-stems below the intestine by a
regular series of transverse commissures in the plexus, which is the primary connecting
medium. It is important to note that there is no ventro-median longitudinal stem in
Nemertea opposite the dorso-median one; and not less important, that the same favourable
species just named enables me to establish with certainty that the ventral transverse stems
reach much further forwards than might originally be expected. The mouth alone inter-
feres with their course; they are, however, found immediately before as well as behind it,
and whilst in front of the mouth the lateral stems very soon merge into the lower brain-
lobes, it is clearly seen that the transverse commissures are still recognisable, 7.¢., that the
lower brain-lobes are united by thin ventral commissures, separated by a very short
distance, till close up to the massive ventral commissure that has been hitherto regarded
as the only ventral connection between the brain-lobes. The thin commissures just
described are, however, not directly connected with the fibrous core of the brain-lobes,
which is, on the contrary, directly continued into the massive inferior commissure, but
they seem to derive their fibres from the outer cellular coating of these lobes. They pass
underneath the two vagus stems, where these spring from the lower brain-lobes, and
where these are in their turn, in front of the mouth, united by transverse commissures,
as was noticed above (p. 38, 45; cf Pl. XIV. fig. 5).

The histological description of the plexus may be very short, and has already been
touched upon in the beginning of this section. Fibrous and cellular nerve-tissue aré
very regularly intermixed, the direction of the fibres follows that of the tracts in which
they are found, and the fibres are, on the whole, closer together than they are often found
in other Platyelminthes, where the designation of the nerve-stems—before they were
recognised as such

as “ spongiose strands” (spongidse Balkenstriinge) was current, and not
inadequate. The nerve-fibres, however, are not so closely bound together, that the
bundles are not very frequently found to be pierced by radial contractile fibres, as was
noticed above, and is rendered evident by comparison of Pl. XIII. figs. 3, 4, 7 That
this intermixture is indeed a primitive character may safely be concluded, if we observe
that Lang in his monograph on the Polyclada (XVIII) specially mentions similar
features in the nervous arrangement of that group of Turbellaria, and also if we remem-

78 THE VOYAGE OF H.M.S. CHALLENGER.

ber that in Carinella the passage of strong contractile fibres, even through the substance
of the brain, was already known (IX).

Of the cellular elements enclosed in the plexus the nuclei alone are conspicuous, and
it is rare to find, either in the plexus or in the medullary nerve, distinct cell outlines
(multipolar or other) round these nuclei, such as they are very often found in the brain.

The nuclei characteristic of medullary nerve and plexus have exactly the same dimen-
sions and shape as those that constitute by far the greater portion of the cellular coating,
both of the brain-lobes (Pl. XIII. fig. 1; Pl. XII. figs. 1-4) and of the lateral nerve-stems.
The direct continuity between the nerve-fibres of the plexus, and those forming the axis
of the lateral nerve-stems, can be demonstrated in all well-preserved sections, at any rate
in those species where the plexus is well developed (Pl. XII. fig. 2). Nor is the continuity
with the fibres of the medullary nerve subject to any doubt (Pl. XII. figs. 3, 4).

This medullary nerve, a dorso-median thickening in the plexus, may be traced back-
wards down to the hindmost extremity of the body, forwards up to the brain-lobes, and
even in front of these. A section of that foremost extremity of the medullary nerve can
hardly be distinguished from that of an ordinary cephalic nerve, but for its median
situation, and greater size and distinctness. It is here independent, 7.e., not enclosed in
the plexus, which does not stretch further forwards than the brain-lobes, or than the
layer of circular muscles. The latter is known to cease in the region of the brain. The
connection of the brain-lobes with the plexus, and with the medullary nerve, is much more
intimate than I was hitherto inclined to believe. Certain specimens of Cerebratulus col-
lected by the Challenger (Pl. XII. figs. 7, 8; Pl. XIII. fig. 1) permit me to form a definite
judgment on this question. We there see that the anterior prolongation of the medullary
nerve bends downwards in the region of the dorsal commissure of the brain-lobes, and
enters into connection with a nervous stratum which may, in this region, be either con-
sidered as a median portion of the brain, or as an anterior thickening of the plexus.
Large ganglion-cells can be detected in it, also fibrous nerve-matter, both of them in the
most intimate connection with the nerve-cells and nerve-fibres of the brain-lobes (Pl. XII.
figs. 7, 8).

From this anterior thickened region of the plexus, in which a transverse core of fibres—
the dorsal commissure of the brain-lobes—takes its course (Pl. XIII. fig. 1), other fibres are
seen to start in the direction of the body-axis and to arrange themselves into a longitu-
dinal tract, which is also provided with nerve-cells, and which becomes the medullary
nerve (PL XIII. fig. 2). My former statement (IX), that the medullary or proboscidian
sheath nerve emerges from the dorsal commissure (loc. cit., pl. i. fig. 1), although
exact, must thus be amplified in the way just described. I may add that a direct passage
of fibres of the medullary nerve into those of the commissure, though sometimes noticed,
is not always a constant phenomenon, Fig. 1 of Pl. XIII shows a state of things in
which the fibres belonging to the plexus and medullary nerve appear to be more or less

REPORT ON THE NEMERTEA. 79

independent from those of the brain commissure that is seen to pass under it, and to
have a different texture and arrangement.

Our observations on the nerve-plexus would not be complete if we did not allude to
the very elaborate branches that pass out from it into the superposed muscular layers
which they innervate. Some of them can even be traced as thick radial nerves piercing
these muscles, and spreading out into the integument (PI. XIII. fig. 6,7). Similarly the
underlying muscular layers receive fine nerve-twigs out of the plexus, which are thus
directed inwards as well, and first penetrate into the circular layer 8. For this reason
they are best seen in longitudinal sections. The peripheral nerve system of the Schizo-
nemertea has thus—as was already fully indicated in a former publication (K)—a totally
different character from that of the Hoplonemertea. The profusion of radial nerve-stems

springing from the plexus, every transverse section showing a great number of them, may
convince us of the high degree of elaboration to which the nerve system of this group
attains, and of which the great sensitiveness and quickly reacting movements of the worms
themselves are the outwardly visible tokens.

Nor may we omit to record the important fact, which was first observed in a Challenger
specimen of Cerebratulus corrugatus, that in the region of the long slit-like mouth
and cesophagus (behind the region where the very strong nerve, to which the name of
vagus-nerve has been given (V, TX), leaves the inferior brain-lobes on its way to inner-
vate the cesophagus) we can observe that from the plexus distinct nerves become detached,
pierce the circular and inner, longitudinal muscle layers (8 and a), cross the circum-
esophageal blood-space and enter the tissue of the wall of the blood lacunz and of the
cesophagus to assist in innervating these important organs. The morphological significance
of this fact will be further insisted upon later on (cf: pp. 134, 142). The phenomenon
is figured on Pl. XIV. figs. 3, 4.

We have now traced the facts concerning the plexus and the medullary nerve. In a
general way these descriptions may be said to be applicable to the plexus of Carinina,
which, however, as was already noticed, is a less favourable object for study. It would
seem as if in this species the nervous tissue, passing inwards amidst the muscles, again
spreads out into a second plexiform arrangement between the muscular layers a and 6.
This phenomenon, however, requires confirmation in more specimens than the two that
have been available for the present investigation.

One point alone requires a few words of further elucidation before we can pass from
the nerve plexus to another paragraph, viz., the question as to whether the name of
proboscidian sheath-nerve, formerly given by me to what I now propose to call the
medullary nerve or the Nemertean medulla, must for the future be dropped altogether.
It certainly must, if we wish to retain it for the longitudinal nerve originally so called ;
but, curiously enough, I have now been able to make out the presence of another longi-
tudinal nerve to which the name may very properly apply.

80 THE VOYAGE OF H.M.S. CHALLENGER.

This nerve is furnished with fibres directly passing downwards out of the medullary
nerve (PI. XIL. fig. 9; Pl. XV. fig. 1); it is situated below this, and is entirely parallel to it.

In one case of a very large specimen of Cerebratulus it appeared in its turn to
be splitting up into two parallel nerve-stems. This proboscidian sheath-nerve more
especially deserves its name because of its situation immediately above the muscular wall
of the proboscidian sheath, into which it may be seen to give off fibres. It is not noticed
in Carinina, Carinella, or the Hoplonemertea, but itis in Carinoma, Eupolia, and all the
Schizonemertea. Its absence in the two first-named genera would appear unaccount-
able if we did not remember that in both of them the proboscidian sheath is of hardly
any importance, being extremely thin-walled (cf. Pl. IL. figs. 4-7). And in this case it
is all the more natural that in the cesophageal region of Carinoma it has become specially
developed, being here even thicker than the medullary nerve, and about as thick as
the lateral nerve-trunks of this species (Pl. XI. fig. 6). This is another example
of sudden increase of a portion of the nervous system, and at the same time of the
existence of a very marked degree of supremacy to which certain apparently subordinate
parts of the organism may all at once attain. This unexpected change of size of the
proboscidian sheath-nerve in one species is certainly a valuable fact for a hypothesis that
will in a further chapter be enunciated (p. 133), according to which the possibility of a
decrease in size of the lateral nerve-trunks is supposed to have been accompanied by an
increase in significance of the medullary nerve.

The fact that in this region of Carinoma the proboscidian sheath-nerve comes into
the foreground so strongly that it might easily be mistaken for the medulla, may probably
be ascribed to the massive development of the inner circular muscular layer 8, which in
Carinina, Carinella and Carinoma acts at the same time as part of the wall of the
proboscidian sheath. The fact was already noticed as a peculiar feature of the species
by M‘Intosh (XXIV), when he first described Carinoma (under the name of Valencinia
armandt).

That a proboscidian sheath-nerve is wholly absent in the Hoplonemertea is still more
easily accounted for. From the moment the brain and longitudinal trunks of the ances-
tral Hoplonemertea were no longer lodged in the midst of the muscular tissue of the
body-wall, but have come to be situated within the gelatinous tissue that fills up the space
inside this muscular body-wall, not only has the plexus disappeared and been replaced
by the remaining metameric nerves described above, but at the same time the innervation
of the proboscidian sheath has altered. This innervation is now brought about by the
peripheral and metameric nerves, which, in favourable cases (Pelagonemertes, &c.), may
be seen to send fine twigs into the muscular tissue of that wall. With this freer develop-
ment of the peripheral nerve-system, the special arrangement by which the innervation
of the proboscidian sheath is brought about, as long as the nerve-sheath is the source
from which all peripheral nerve-fibres take their origin, has at the same time disappeared.

REPORT ON THE NEMERTEA. 81

It is certainly all the more remarkable that in the Hoplonemertea we nevertheless
find such very distinct traces of the medio-dorsal medullary nerve, notwithstanding the
disappearance of the plexus. And more remarkable still that this remnant—not dis-
tinctly traceable in only one specimen of Amphiporus, whilst other specimens of the
same species still have it, and whilst it 1s even very conspicuous in Drepanophorus and
others—should occupy the same position as it does in the most primitive Palzeonemertea,
2.€., In or even outside the basement membrane of the integument. This is another
argument for directly deriving the Hoplonemertea from the Palzeonemertea. Cephalothrix
may be said to fill up part of the distance which separates Carinina and Carinella from
the Hoplonemertea as far as the situation of the nerve-system is concerned (cf. Pl. XI.
fig. 5), whereas Hupolia may be said to do the same with respect to the ciliated grooves
on the head, and partly also to the posterior brain-lobe, its glandular investment, and the
long duct leading from it to the exterior.

We must now pass on to the description of the brain-lobes and the lateral nerve-stems.

Tt is known that these offer the lowest degree of specialisation in the more primitive
genera of Palzeonemertea, e.g., Carinella. For this genus the brain- and nerve-stems
have been sufficiently described before (IX), and, in comparing this with what we find in

Al.

Fic. 5.—Side view of the brain of Carinina in outline, reconstructed from the sections. The fibrous core is indicated by a
dotted line. A./., anterior lohe; P.l., posterior lobe ; Co., ventral commissure ; Ln, Lateral nerve-stem.

Carinina, the latter genus must be recognised as representing in this respect a somewhat
higher scale in the developmental series. This higher development finds its expression in
the presence of a posterior brain-lobe, comparable to the same lobe of the Schizonemertea
which was often designated as the side organ, although it is formed of nerve-substance
directly merging into that of the brain. Carinella inexpectata has been formerly
shown (VIII) to possess a ciliated passage leading into the brain-substance, without any
special differentiation of that portion of the brain into which this ciliated channel pene-
trates. In Carinina such a differentiation has set in, and the brain-substance, into which
a ciliated canal leads, has become a separate lobe.’ In consequence of this we are,
moreover, enabled to draw a general—though by no means a sharply defined—distinction
between the portion of the brain-mass with which this accessory lobe is in contact, and

1 Chapuis has lately noticed posterior brain-lobes in a Cephalothrix (Arch. d. Zool. Exp., vol. iv. p. xxi., 1886). His
description is, however, very incomplete.
(Z00L. CHALL. EXP.—PaRT Liv,—1887.) Hbh 11

82 THE VOYAGE OF H.M.S. CHALLENGER.

that which is continued into the lateral nerve-stems, 7.e., an incipient distinction between
a pair of upper and a pair of lower lobes, respectively limited by the dorsal and ventral
brain commissure; the whole forming a ring round the proboscis and its sheath. A
side view of the brain of Carinina—reconstructed from a series of sections—is given
in the accompanying woodcut, in which the very thin dorsal commissure is not
indicated. A comparison with figs. 4 and 7 of Pl. V. will at once show the relation of this
stage of differentiation to that to which Hupolia has attained. In the Schizonemertea
the separation between upper and posterior lobes is more marked still than in Eupolia
(Pl XIV. fig. 6); in the Hoplonemertea they are definitely separated, and only con-
nected by one or more nerve-strands (Pl. IX. fig. 10), their situation being then some-
times behind, and even sometimes before the rest of the brain.

The ciliated canal penetrating into the posterior lobe of Carinina is simple (not
divided in two as in certain Hoplonemertea), and provided with a high, ciliated epithe-
lium of its own. It is figured in figs. 1 to 3 of Pl. VI. Certain glandular cells, g/. br, are
seen in this same figure to have become specially developed in connection with this
posterior lobe and its ciliated canal. Similar glandular cells also form a characteristic
feature of the posterior brain-lobes of Schizonemertea and Hoplonemertea. In Carinina
it is evident that these glandular cells are derivatives, or at least morphological equiva-
lents, of the deeper glands G7, of the integument.

The nerve-cells themselves, out of which the brain is built up, still undoubtedly
belong to the integument, and it is exceedingly difficult, if not impossible, to draw a
sharp distinction between the outermost brain-cells and the surrounding integument-cells.
In the figures just cited this difference has been artificially very much accentuated in order
to bring out more distinctly the outline of the brain ; for the same reason, the integu-
ment in this figure was on purpose not fully worked up.

The inner core of the brain is fibrous, so is the core of the longitudinal stems, where,
however, the attempt at a distinction between nerve-cells and cells of the surrounding
integument is equally hazardous (PI. ILI. fig. 8). This fibrous core is in direct continuity
with the nerve-plexus, that spreads out in the deeper integumentary layers.

A vagus nerve passing from the lower portion of the brain on both sides towards the
cesophagus is also distinct in Carinina (Pl. VI. fig. 1, Nv). The passage of contractile
fibres through the brain-substance is unmistakable, though less evident than in Carinedla.

Passing on to the description of the nerve-centres of Hupolia, we immediately recognise
the difference resulting from the fact that here the brain is imbedded inside the muscular
layers, as is also the case in all Schizonemertea. =

Our description of the brain of Hwpolia may be based upon the figures of Pl. V., which
were obtained not de visu, but by reconstruction from a series of sections.’ Figs. 1-4

? For the making of these and many other series of sections, and for assistance in the reconstruction above alluded to, I
am indebted to the kindness of Dr. Oudemans, my former assistant, now director of the Zoological Garden at the Hague.

REPORT ON THE NEMERTEA. 83

and 8 represent the whole of the brain tissue, figs. 5-7 and 9 the fibrous core, as it is
enclosed by the nerve-cells, the limit of this cellular investment being given in outline in
the latter figures. It must, however, from the first be remarked, that this outline should
be completed by the plexus, and by the median medullary nerve. They are not indicated
in these figures, although both of them are found along the whole length of the lateral
nerve-stems, and reach forward as far as the region of the dorsal brain commissure.

It is seen at a glance that the fibrous core repeats the external folds and prominences
of the brain-masses, that.the lateral nerve-stem is continued into the lower lobe, and
that the upper lobe is distinguished by a prominent fold of its surface, a gyrus (fig. 1,
SL), into which a separate knob of the fibrous core is seen to pass, and by two other
fibrous projections—the one stretching towards the blunt end of the posterior lobe, the
other running forwards and accompanying the ciliated canal, which is also marked in
outline in fig. 6, and (in red) in fig. 5. The canal cc, in figs. 2, 3, 4, 8, is the exterior
portion of this duct. The different thickness of dorsal and ventral brain commissure may
be gathered from figs. 1, 3, 8, 9; from the latter two, the fact that the nerve-fibres are
very strongly preponderant in these commissures over the cells. Close behind the ventral
commissure the nerve for the cesophageal wall, vg, the so-called vagus nerve, is seen to
leave the common fibrous core of the brain, whereas the nerves for the proboscis (pn)
spring from the inner surface of the ring, where the fibrous core turns up from the ventral
to the dorsal commissure (figs. 5, 9). The vagus nerve is soon after its origin connected
by transverse fibres with its opposite neighbour; this vagus commissure is sometimes
repeated ; it will be again referred to in the general considerations on the nervous system.
The cephalic nerves that leave the brain and innervate the head are only very imperfectly
rendered in these figures; their number is far greater than might be concluded from
figs. 5, 6, an.

The aspect of several portions of the brain of Hupolia, in transverse section, is repre-
sented in Pl. VI. ;

It will there be noticed that fig. 4 represents an anterior section through the inferior
brain commissure and the point of innervation of the proboscis, fig. 5 one just behind
this, cutting the dorsal commissure and the vagus root at the same time. The exact
situation of these sections will be best understood by comparing them with PI. V. fig. 9,
where the respective positions of the commissural ring, the proboscidian nerve, and the
vagus are clearly indicated. Fig. 7 is a transverse section lying further backwards,
almost in the level where the dotted line, SZ, in Pl. V. fig. 4 terminates, whereas the
section fig. 8 lies again somewhat behind this, at a point where the “gyrus” of the superior
brain-lobe actually divides the central fibrous nerve-substance into an upper and a lower
portion. These sections, at the same time, show the difference in size between the
brain-cells and the glandular elements partaking in the constitution of the brain, along
the superficial part of what I have called the posterior brain-lobe (side-organ, auct.).

84 THE VOYAGE OF H.M.S. CHALLENGER.

The brain of the Schizonemertea was fully discussed in a former publication (Ix). The
Challenger Schizonemertea all conform to this type, with the additional facts alluded to
above in connection with the medullary nerve. The difference in the size of the ganglion
cells in different regions of the brain, as it appears in’ PLOxitigs 7,8; and Pl xa
fig. 1, is much more marked in certain species of Cerebratulus than in others. The
larger sized nerve-cells appear to be principally peripherally and anteriorly situated ; that
they are absent, or less numerous, in certain other species, may be seen by comparing
Pl. XII. fig. 1, with the above mentioned figures. The relative distribution of fibrous
and cellular nerve-matter in the brain need not be any further described in detail after
our foregoing description and figures of Hupolia, The size and shape of the posterior
lobe is, however, somewhat different in the Schizonemertea. This will be obvious by com-
paring pl. i. fig. 1 of the treatise referred to (IX) with our present figures of Hupolia.

Not having been able to study any of the Challenger species alive, we should have to
be content with reconstruction from section series, if I were to enter more fully into the
discussion of the respective differences, and for that reason I wish to restrict myself
to these general remarks.

One other point connected with the posterior lobe and its ciliated duct deserves
special mention, viz., the observation I was able to make that the duct which leads from the
bottom of the cephalic slits into the nerve-tissue of the posterior brain-lobe (inside the
brain-lobe it very generally has an S-shaped, and, at the same time, a spiral twist, thus
being very often as in Pl. XIV. fig. 6, cut in three places, all in one section), and which is
clothed in the neighbourhood of its external opening with an epithelium directly con-
tinous with, and similar to, that of the outer surface, not only shows certain differences
in its epithelium, as we pass further inwards (Pl. XIV. fig. 11), but also offers certain
complications, which we have now to consider. These complications very distinctly con-
cern the participation of deeper cellular layers of the integument. As indicated by g/ in
Pl. XIV. fig. 11, these deeper layers segregate and form a ring-shaped or cushion-shaped
addendum to the simple epithelial tube. It must be doubted whether they communi-
cate with the exterior, as do the deeper glands of the integument, although this
deserves special attention, because of the glandular significance which must be attached,
according to Dewoltezky (II), to the strongly refractive cells present on the posterior
surface of the hinder brain-lobe (cf. p. 94). The epithelium has undergone still more con-
siderable alteration when it passes inside the posterior brain-lobe. Its nuclei are distinct
(Pl. XIV. figs. 6, 7, 8), but instead of direct cell partitions we may observe a fine striation
vertical to the axis of the ciliated canal (fig. 8). This feature, known to former observers
(IX, figs. 35, 36), may here be more especially alluded to, because in Hoplonemertea
(Pl. XIV. fig. 10) we find that the discharge of glandular products from the deeper gland-
cells takes place between the interstices of this striated region. This discharge into the
lumen of the canal is a point that is put beyond doubt by numerous Challenger sections.

REPORT ON THE NEMERTEA. 85

The fact that the canal is single in the Schizonemertea, whereas it is double in the
Hoplonemertea, was known before (IX). It was also found to be confirmed in all the
Challenger species ; the bifurcation of the canal taking place in such a manner, that the
one branch passes through the distinct nerve-cells, forming the greater mass of the lobe,
whereas the other one immediately penetrates—more peripherally—amongst the much
larger glandular cells overcapping the foregoing. Carinina corresponds with the Schizo-
nemertea in having the canal single.

Having considered the central fibrous substance of the brain in the Paleonemertea and
Schizonemertea, we have only to add that the Challenger Hoplonemertea have also con-
firmed the fact that here this fibrous core is less complicated, the brain-lobes being
at the same time more compact, the cephalic nerves very numerous. In Cerebratulus angus-
ticeps (PI. XIV. fig. 6) the fibrous core is very massive and conspicuous also. As to the
innervation of the numerous eyes, I have no new observations to record (cf V and IX),
nor as to that of the proboscis, with the exception of the fact that in Drepanophorus
and Amphiporus I could distinguish numerous nerves springing from the brain-ring and
corresponding to the numerous longitudinal trunks in that organ. This point, which was
left in doubt by v. Kennel (XVI), is thus definitely settled. The phenomenon was parti-
cularly distinct in one specimen of Amphiporus moseleyi that had retained its proboscis.
It has only been partly figured in Pl. IX. fig. 10, where only two are indicated, so as not
to obscure the diagrams.

As to the innervation of the cesophagus, little need be said as far as the Schizo-
nemertea are concerned, the well-known strong and double vagus nerve being constantly met
with. Distinct nerve-branches are seen to take their course in the walls of the cesophagus
(Pl. XIV. figs. 3, 4); it was already noticed above (p. 79) that these may be partly
traced to separate branches springing independently from the nerve-plexus, whereas for
the other part they are ramifications of the so-called vagus.

Nerves to the intestinal canal, very easily detected in the cesophageal region, could
not be traced with the same accuracy and distinctness in the post-cesophageal region of the
intestine, most probably owing to the extreme tenuity which these fine and delicate nerve-
twigs may here have obtained. It cannot be determined atipresent whether this portion of
the intestine also receives branches from the cesophageal vagus system or only directly
from the plexus, now that the existence of such a double method of innervation (Cerebra-
tulus corrugatus) has been actually demonstrated for the anterior regions of the intestine.
On @ prior? grounds, I look upon the latter arrangement as by far the most probable."

The course of the vagus is somewhat modified in Drepanophorus, and perhaps in
Amphiporus. I find the strongest nerve-stem, connecting the brain with the cesophagus,
in Drepanophorus, running forwards instead of backwards (PI. IX. fig. 10). Other smaller

1 Tt should here be noticed that Kleinenberg (loc. cit., p. 114) has also failed to detect visceral nerve-branches to
the endodermal intestinal epithelium of the Annelid, Lopadorhynchus.

86 THE VOYAGE OF H.M.S. CHALLENGER.

stems leave the brain in corresponding regions of the lower brain-lobe, z.e., along the surface
turned towards the proboscidian sheath, and run in the direction of the cesophageal
epithelium. This secondary innervation, though different in morphological aspects, is
more or less homologous with the facts above disclosed in the case of Cerebratulus corru-

gatus. That the vagus proper—the massive and thick stem—is here turned forwards
may be a consequence of the change in the situation of the mouth, which in the Hoplo-
nemertea is no longer behind the brain, but in front of it. This gradual change of
position may very possibly have drawn the vagus-stem with it. In concluding our
remarks upon the brain I have only to add that the well-known difference between
Schizonemertea and Hoplonemertea with respect to the connection between anterior and
posterior brain-lobes (side organs) also obtains in the Challenger specimens. The latter
are connected in Drepanophorus and Amphiporus with the brain by one or more fibrous
commissures.

Another difference several times observed between the fibrous brain-tissue of these
two Hoplonemertean genera on the one hand, and Cerebratulus, Eupolia, &ec., on the
other, is a marked increase in compactness of the fibres, so much so that the fibrous
character of the central portions of the brain has often more the aspect of Leydig’s
“ Punktsubstanz,” and even shows a still more delicate and more compact texture by

?

the appearance in this “ Punktsubstanz” of regular patches with very faint outlines,
which apparently are still more compact regions of this tissue.

The longitudinal nerve-stems, which are the posterior continuations of the lower
brain-lobes, hardly need any special mention. It must only be insisted upon that in
them, as well as in the brain-lobes, there is no absolute distinction between the cellular
envelope and the fibrous core, but that imside this core nuclei are invariably scattered,
which bear testimony to the absence of any such definite boundary. Still, there is
generally a homogeneous and very thin layer between the cellular coating and the fibrillar
core, a kind of membranous neuroglia, through which the fine processes of nerve-cells may
be seen to take their course in groups, which then become lost amongst the fibres of the
core. Then, again, certain favourable sections (Pl. XII. fig. 2) very distinctly show the
course of nerve-fibres inside this fibrous core that are not longitudinal, and thus puncti-
form in transverse sections, but that are interwoven at right angles with the latter and
continue their way into the nerve-plexus. The transparent sheath of the fibrous core
of the nerve-stem is more distinct in Cerebratulus than in either Palzeonemertea or
Hoplonemertea. It is rarely encountered in the brain, where fibrous and nervous elements
are more intimately interwoven (cf: Pl. VI. figs. 4-8; Pl. XII. figs. 7, 8; Pl. XIV. figs. 7, 8).

Outside of the stems there is another accumulation of homogeneous connective
tissue arranged as a protecting envelope round the nerve-stems. This is much more
conspicuous in the brain-lobes, and more so in the Hoplonemertea (Pl. XII. fig. 5) than
in the Schizonemertea (Pl. XII. fig. 2; Pl. XIV. fig. 2). Still in the latter it is far more

REPORT ON THE NEMERTEA. 87

conspicuous than in Carinina, where we have already pointed out the apparent absence
of any sharp or distinct boundary line between the cellular brain-tissue and the sur-
rounding cellular tissue of the integument.

We cannot pass on to the description of the peripheral nerves without first referring
to the terminal portion of the lateral nerve-stems, known to terminate at the posterior
end of the body, right and left of the anus in the Schizonemertea, but also known to
meet in a connecting commissure above the anus in several Hoplonemertea (TX). This
commissure was found by me in several Challenger species, but at the same time I was
able to verify the unexpected fact that in Hupolia the fibrous cores of the longitudinal
nerve-stems are also posteriorly united by a commissure. What most especially
deserves attention in this posterior commissure of Hupolia is, that it is found below the
anus, the longitudinal stems and the commissure, together with the brain, thus forming
an immensely elongated ring round the intestine, whereas in most of the Hoplonemertea
alluded to, all the portions of the nerve-system may be said to remain above the intes-
tine. This is, indeed, very emphatically the case in Amphiporus moseleyi, where we find
(Pl. IX. fig. 4) not only the brain and the anal commissure above the intestine, but also
the longitudinal stems, that take their course above the intestinal ceca. Nevertheless,
in Drepanophorus the anal commissure is above the intestine, although here the
longitudinal stems are diametrically opposite in position, 7.e., below the intestinal czeca.
They were for this reason considered (IX) to furnish a transition stage to the ventral cord
and cireumcesophageal ring of Annelids and Arthropods, a consideration which derives
very strong support from the existence of transverse commissures that will hereafter be
described. At all events, these very curious differences—the anal commissure of Hupolia
is figured on PI. VII. fig. 8—furnish another proof of the extraordinary plasticity which
we meet with in the group of the Nemertea, with respect to the morphology of the most
important components of the system; a plasticity and diversity which are at the same
time indicative of the primitive and low scale on which the Nemertea may be said to
find themselves.

Coming now to the peripheral’ nerve-system, I may note that I have already, some
years ago (X), stated that it is difficult to apply this name in its generally accepted
significance to the arrangement which we find in Schizonemertea and in Palzeonemertea.
It is, however, applicable to that of the Hoplonemertea. Here only we find distinct
metamerical peripheral nerves leaving the longitudinal nerve-stems at regular intervals,
and innervating the body musculature, the integument, the internal organs, &e.

In the Schizonemertea and Paleeonemertea the cephalic nerves, starting from the brain,
are directly comparable with those of the Hoplonemertea, but the rest of the peripheral
system is here represented by the plexus and its innumerable branches and twigs, which
are directed upwards and downwards, serve for the same purpose, and render the peripheral
arrangement in this group so primitive and so important. Still, in very large specimens

88 THE VOYAGE OF H.M.S. CHALLENGER.

of Schizonemertea (Pl. XIV. fig. 2) I could observe that from the thickened part of the
plexus, which forms the longitudinal stem, fine nerve-branches also take their origin, and
pass directly to the periphery. The essential difference between Schizonemertea and
Hoplonemertea in this respect nevertheless remains the same as above formulated.

We may now turn to the Hoplonemertea. The different species contained in the
Challenger collection confirm the well-known facts about the metamerically placed pairs
of peripheral nerves of the Hoplonemertea, some of which are turned dorsally, others
ventrally, and which, dividing dichotomously, finally spread out im very numerous
bundles of nerve-fibrils, serving for the innervation of the environing regions. In addi-
tion they also furnished me with certain important new points. To begin with the latter,
I will first draw attention to the two longitudinal nerve-stems of Drepanophorus
lankesteri, which are situated, as is characteristic of this genus, below the intestinal
ceca (Pl. IX. figs. 1, 5, 6), about midway between the lateral margin of the body and
the median ventral line. These stems in transverse section very much resemble those
of other Hoplonemertea. One of them is figured on Pl. XII. fig. 5; from this it may be
seen that the nerve-cellular coating is generally not distributed as a sheath all round the
fibrous core, but as a double band applied upon this core at two diametrically opposite
points. The participation of this cellular coating in providing the outgoing peripheral
nerves with delicate nerve-fibres is distinctly seen in this section, as is also the direct
continuity of other portions of the peripherally directed nerve-fibres with those of the
core.

When in Drepanophorus lankesteri I followed some of these peripheral nerves in
their further course, by examining the consecutive sections in which they are continued,
I was struck by the very remarkable fact, never noticed before, that some of them
did not dichotomise—or at least very rarely—and did not taper towards the periphery,
but passed directly under the intestine from the one longitudinal nerve-stem into the
other, a distance in this specimen of 14 mm. This was an unmistakable com-
missure, Which could in no way be compared to the well-known commissure above
alluded to, which connects the two longitudinal stems above the anus. And not
only was one such ventral commissure present, but on closer inspection I found a
great number of them, and by registering the respective distances at which they
were present, the one behind the other (about + mm.), I was forced to the conclusion
that we here have before us a system of very regular metamerically placed commis-
sures between the longitudinal stems, and forming a nerve-ladder (Pl. IX. fig. 10),
which is very directly comparable to that of Sabel/a and other species among Annelids,
and to that of Proneomenia and Chiton among Molluses. In a few of these commissures
I detected dichotomy and fusion of one of the branches thus formed with the fore-
going or with the following commissure, a peculiarity also known to exist in Chiton, but
evidently of rarer occurrence in Drepanophorus lankesteri. Moreover, I may also men-

REPORT ON THE NEMERTEA. 89

tion that in certain commissures it was clear that fine nerve-twigs spring from them and
serve to innervate the surrounding tissues, their significance thus not being solely com-
missural. The different facts just recorded are represented semi-diagrammatically on Pl.
IX. fig. 10, which was reconstructed from the very large number of sections which I
have of this species. It is, moreover, seen in this reconstruction how other peripheral
nerves spring from the longitudinal stems as well, some being directed upwards or
downwards, some towards the side or inwards. These peripheral stems are metamerical,
as are the commissures, a metamery which, though not absolute, and sometimes broken
by certain irregularities, is still more advanced towards perfect regularity than is the
incipient metamery which we observe in the nerve-tracts that are noticed inside the
plexus of the Schizonemertea, and that were more fully described above. The transverse
commissures between the lateral stems may be noticed to go up quite close to the brain-
lobes, as indicated in the diagram on Pl. IX. fig. 10. Both in this respect and in the
fact of their existence, they call to mind the ventral commissural tracts in the plexus of
Schizonemertea. I have no doubt that the two systems are homologous, the commissures
having subsisted im Drepanophorus lankesteri although the plexus has disappeared.
Finally, it must be mentioned that as yet I have looked for them in vain in other species
of Drepanophorus, or in other Hoplonemertea. My other specimens of Drepanophorus
are, however, less well preserved than is the one specimen of Drepanophorus lankesteri.

Another peculiar feature of the peripheral nerve-system of the Challenger Hoplo-
nemertea, which has also remained hitherto unnoticed, is most favourably observed
in Amphiporus marion, although I afterwards noticed it in other Hoplonemertea. It
is figured on Pl. X. fig. 1, ne, and consists in the fact of a peripheral stem, which
has taken its outward course away from the longitudinal nerve-trunk, and which
has penetrated amongst the pennate fasciculi of longitudinal muscle-fibres of the layer
a, spreading out in a plane parallel to that of the body-surface, and thus forming a kind
of local plexus between the muscular layers a and B. It must for the present remain an
open question whether this arrangement, which can be noticed in different regions of the
game section, and which in no section was absent, must be regarded as a primitive
feature connected with the plexiform arrangement which must have obtained in the
ancestral forms of the Hoplonemertea, or whether it is merely a special adaptation,
having arisen in certain Hoplonemertea, and being in some way subservient to the
innervation of the muscular investment or the integument. At all events it is a peculiar
arrangement, and, as such, deserves special mention.

How intricately and yet how regularly the peripheral nerve-system of the Hoplo-
nemertea may be said to be distributed can also be gathered from Moseley’s figure of
Pelagonemertes, which we have copied on Pl. I. fig. 23, where the peripheral nerves
are seen to spring, two at a time, from the lateral trunks, which here, too, are united
posteriorly by a commissure above the anus.

(ZOOL. CHALL. EXP.—PART LIv.—1887.) Hhh 12

90 THE VOYAGE OF H.M.S. CHALLENGER.

One peculiarity, finally, deserving special mention is the presence in the majority of
well-preserved specimens of Hoplonemertea of a medio-dorsal longitudinal nerve homo-
logous to the medullary nerve described above (cf: p. 81, and Pl. XI. fig. 8). Its connection
with the rest of the nervous system could not be satisfactorily made out, although traces
of a connection with the dorsal brain commissure were not wanting in many specimens.
Its presence is, however, significant, and its retention in the Hoplonemertea, where the
arrangement of the nerve-system has so considerably deviated from the primitive Palzo-
nemertea and Schizonemertea, must prevent us from underrating its morphological
significance. This will be more fully entered into in the chapter of General Considera-
tions at the end of this Report.

SENSE-ORGANS, ACCESSORY GLANDULAR STRUCTURES, AND ORGANS
OF UNKNOWN SIGNIFICANCE.

The most conspicuous sense-organs of the Nemertea are without doubt the eyes.
Although eyes are absent in very many genera and species, and although in some species
pigment spots at the tip of the snout are regarded as such, other genera have very well-
marked and numerous eyes, with a hyaline hemispherical refractive body, a layer of visual
rods, and an optic nerve connecting the eye with the brain-lobes. These more highly-
developed eyes were previously known to occur in the Hoplonemertea, and the Challenger
material has confirmed these general conclusions. The most primitive of the Palzeo-
nemertea, Carinina, is not provided with eyes. Nor do I find traces of eyes in those
species of Hupolia which were contained in the collection, and of which the head was
studied in sections. Hupolia giardii is among these. However, it is known from
other researches (VIZ) that different species of Hupolia have often very numerous eyes,
increasing in number with the growth and the age of the animal, and, moreover, that
these eyes resemble those of the Hoplonemertea in many respects. Nor were the Schizo-
nemertea of the Challenger provided with eyes that revealed their presence in the
microscopic sections, although I would not venture to affirm the total absence of eye-
like structures or pigment spots. In this respect the fresh animal often shows at
a glance what is very difficult to demonstrate in the series of sections, e.g., the
number and disposition of the eyes or pigment spots. As, moreover, these data can
hardly be of any taxonomic value for the determination of the Schizonemertea, I think
I may pass on to the discussion of the eyes of the Challenger Hoplonemertea.

They have the characteristic histological arrangement already described and figured
by myself in a former publication on the subject (IX, fig. 42). A posterior layer of rod-
like elements, which is in direct connection with the optic nerve, is enclosed by pigment,

REPORT ON THE NEMERTEA. ot

and the whole completed into a more or less oval cup-form of which the anterior part
shows very distinct cellular elements with nuclei. Distinct lenticular structures, which
were formerly noticed in Mediterranean Nemertea, could not be certainly made out
in the Challenger specimens. What varies most is the pigment coating the posterior
hemispherical surface. Sometimes this pigment is intensely black, and so extremely fine
that it looks almost homogeneous (Aimphiporus moseley’), whereas in other cases (Amphi-
porus mariont) the pigment granules are uncommonly coarse and large sized, the colour
being in this case a brownish-green rather than black.

In discussing the further sense-organs of the Nemertea, a great significance must
certainly be ascribed to the sensory elements distributed in the skin, and primarily
serving for tactile functions. With respect to this organ of sense, the spirit specimens at
my disposal have, however, revealed no new facts of importance. I have only convinced
myself—as has been already noticed both when describing the cellular integument and its
innervation—of the presence of distinct sense-cells in all parts of the integument. They
have the well-known form of the sense-cells described by the Hertwigs, by Lang, and by
others in the Ccelenterata, in the Platyelminthes, &c., and it is to them that the
extreme delicacy of the tactile sense, which is revealed in living specimens of Nemertea,
must be ascribed. Bateson’s fig. 777 of Balanoglossus comes very close to what was
observed in the Nemertea in connection with these sense-cells. Their direct innervation
by nerve-fibres, starting radially from the plexus in the two more primitive groups, has
been noticed above (cf. Pl. XIII. fig. 6 ; Pl. XIV. fig. 2). Sense-cells with distinctly longer
and stiffer hairs, such as I have been able to observe in living specimens from the Bay of
Naples, have not come under my notice in the Challenger sections. The similarity
with Balanoglossus, just alluded to, is increased if we consider Bateson’s figs. 70, 75, and
79, and compare them with the integument of Carinina. The similarity is significant. In
sections of Balanoglossus made by myself I was very much struck by this resemblance,
reaching from the cilia down to the nerve-plexus and subjacent muscles.

Another question I wish to allude to here, and which has been pressed upon me by
certain of the Challenger specimens, is whether the terminal transverse furrow which
is encountered at the tip of the head in Carinina (PI. I. fig. 1-8; PL II. fig. 1), which
is also distinctly seen in certain Amphipori (Pl. IX. fig. 9), has not also primarily a
tactile significance. And, in addition to that, I wish to ask whether we might not look
upon this terminal groove, which lies more or less in a horizontal plane passing through
the animal, as having preceded the paired longitudinal cephalic furrows which form the
distinctive feature of all the Schizonemertea. When considering the probability of this
suggestion, the following points should not be lost sight of—(1) that in certain
Cerebratult these cephalic furrows do meet at the tip of the head (Pl I. figs. 13.
14, 18,19); (2) that the furrows in this case are comparatively short (figs. 13, 14);

1 Quart. Journ. Micr. Sci., June 1886.

92 THE VOYAGE OF H.M.S. CHALLENGER.

(3) that in Carinina the opening through which the proboscis is everted lies ventrally to
this furrow; (4) that in most Cerebratuli the proboscidian opening would similarly lie
ventrally to the point of meeting of the lateral cephalic furrows if we supposed these to
meet at the tip of the snout; (5) that in a few cases the opening appears to have shifted
into the central part of the fissure; (6) that in other Cerebratuli the fissures, though
continued on the anterior and apparently truncated portion of the snout, do not wholly
fuse (Pl. I. fig. 12), but that just in the interval the proboscidian opening is situated ;
(7) that again im other Cerebratuli this anterior truncated portion is wholly devoid of
any continuation of the fissures, which in their turn may be exceedingly deep and long
(PL I. fig. 16); (8) that in the Amphipori alluded to (Pl. IX. fig. 9) the common
opening for proboscis and digestive cavity is also situated ventrally to the terminal fold ;
(9) that in Hupolia transverse and very shallow cephalic fissures are found, which very
strongly resemble those of the Hoplonemertea (even in the presence of short and numerous
secondary grooves perpendicular to the principal groove), and which similarly contain the
opening that leads into the posterior brain-lobe, as is the case in Carinina and the
Hoplonemertea, and that even yet in certain Hupolix a trace of a terminal horizontal
furrow has been retained (PI. I. fig. 7).
Tabulating these different facts, the case would appear to stand thus :—

Carinella annulata, one terminal shallow horizontal groove, two transverse lateral
ones, no ciliated canal.

53 inexpectata, (VIII) terminal groove uncertain, transverse lateral grooves,
ciliated canals into the brain-substance opening out into these
orooves,

Carinina, . : . terminal groove present, lateral grooves, with openings of
. ciliated canal leading into a separate posterior brain-lobe.
Amphiporus, —. . terminal groove present, lateral grooves, with openings of
ciliated canal leading into a separate posterior brain-lobe.
Eupolia, . . hardly a trace of terminal horizontal groove, lateral grooves as
in the Carinellidze and Hoplonemertea.
Valencinia, . no grooves at all, simple round opening for ciliated canal.
Schizonemertea, . two longitudinal (never transverse!) cephalic grooves which in

some cases are wholly separate, in other cases meet at the tip
of the snout, and might then in their entirety be compared to
a terminal horizontal groove such as that of Carmina.

If the latter conjecture be true, “.e., if we may suppose the lateral furrows of the
Schizonemertea to be derived from an ancestral phase, in which a terminal groove like
that of Carinina was separated into two halves which deepened and widened on both
sides of the head, reaching down as far as the opening of the ciliated canal into the

REPORT ON THE NEMERTEA. 93

posterior brain-lobe, then, indeed, Carinina may be said to represent—also with respect
to the fissures and grooves on the head—a stage of development in which both the
characteristic features of the Hoplonemertea and the Schizonemertea are still present in
combination. In deviating from the original arrangement, the Schizonemertea would
have gone a longer way than would the Hoplonemertea, some of which still answer to
the original type of structure found in Carinina.

I now wish to consider more closely certain details of these different cephalic fissures,
which cannot be discussed in a more appropriate place than in the section treating of
the sense-organs, although their exact significance must for the present remain unsolved.
In spirit preparations the ciliated coating of the body is generally never better preserved
than in these furrows ; and the cells carrying the cilia, as well as their nuclei, are in most
cases exceedingly distinct. However, in a few cases it is only the superficial layer of
the integument that is thus continued as a clothing of the inner surface of these furrows.
In most cases I could observe the deeper layer of integumentary glands (Schizonemertea)
to be continued, although less compact, along the whole inner surface of the cephalic slits.
Generally these deeper glandular layers appear to have undergone some special modifica-
tion in connection with the canal that opens out at the bottom of the furrow, and leads
into the brain-substance, a modification which may already be noticed in so primitive a
genus as Carinina, which, however, with respect to this apparatus, may be said to be
more differentiated than the allied genus Carinella.

We find in Carinina (Pl. VI. figs. 1-3) that all round the bottom of this groove (Cg)
there is a marked increase of the number of nuclei in the integumentary tissue; and
although these nuclei can scarcely be said to belong to the layer of the deeper glands (c/-
Pl. IV. fig. 1 £, and the paragraph on the integument), but rather to the one exterior to
this, the fact of their accumulation in this marked way, just along the inner surface of
the cephalic groove, is a most reliable indication that the integument is In some way
modified in adaptation to the significance of these grooves. In PI. VI. fig. 1 a distinctly
pointed shape is assumed by this wedge-like or horse-shoe-shaped accumulation of nuclei,
and a fibrous band connecting them with the intermuscular tissue is even visible, more or
less clearly, separating—at least in this section—a posterior brain-lobe Br’, into which
the canal passes, from the anterior brain-mass Br (cf. woodcut, p. 81). The glandular
layer is, however, not indifferent or neutral during these changes in the exterior nuclear
one; and although the two specimens at my disposal do not permit me to unravel the
whole of the modifications it undergoes, I may still be permitted to observe that in figs.
2 and 3 of PI.VI. its participation (Gi and gl.br) cannot be denied, whereas a comparison of
all the three figures here given makes it appear very probable that these glandular elements
(gi.br), derived from the deeper layer of the integument (G7), play a part with respect
to the posterior brain-lobe of Carinina, which may best be compared to the glandular
investment of the posterior brain-lobe, as it is encountered in all the other Nemertea

94 THE VOYAGE OF H.M.S. CHALLENGER.

(cf. Pl. VI. figs. 7, 8; Pl. XIV. figs. 6-8, 11). What the physiological meaning of this
glandular investment may be must remain unsolved for the present, although we will
return to this question further on. Carinina demonstrates that, as the brain-lobes are
direct derivatives of the integument, so is the glandular investment of the posterior one.
I may here note that, in studying the development of Lineus obscuwrus, 1 have (XIV)
been able to determine the fact that the glandular investment and the nerve-cells of the
posterior brain-lobes also arise in that species out of the same mass of embryonic
cells.. Moreover, I must add that the glandular significance of this investment was for
the first time more emphatically brought forward by Dewoletzky in a short notice on the
Nemertea (II), Although I cannot accept all the conclusions to which this naturalist
arrives with respect to the apparatus of which we are here treating, and must demur
when he rejects the specially adapted respiratory significance which the brain canal must
necessarily have in very many species, still it is only fair to call attention to his inquiry
into the nature of this cellulo-glandular investment.

The only point which has still to be noticed, and which is partly a repetition of what
has been already described in the paragraph on the nervous system, is the fact of the actual
observation by myself in Drepanophorus lankesteri, from the Challenger collection, of
the passage of the contents of part of these glandular investing cells into the lumen of
the canal (Pl. XIV. fig. 10). Moreover, one point should not be lost sight of, viz., that
between the glandular cells that form an actual investment of the posterior lobe (and
which in Carinina could be identified with the deeper glandular structure of the integu-
ment) and the actual integumentary glands, there exists in Schizonemertea a constant
and considerable difference, even with respect to the affinities for staining reagents, and
still more in the general aspect. The case of Carinina is on this account all the more
interesting. We must only be careful not to look upon the exceptional case which I was
able to observe and to figure (PI. XIV. fig. 11, gl), in which an additional glandular (7?)
ring surrounds the ciliated canal after it has passed out of the brain-lobe on its way to
the exterior, as.one of transition. I hardly think that this special adaptation, which has
been already noticed above (p. 60), pertains to the layer of the deeper skin-glands ; and
though I am not prepared to offer a definite opinion, I am much more inclined to compare
this curious accumulation of distinct and nucleated cells with a similar accumulation
which we have also noticed in Carinina, and have there encountered more peripherally
but still surrounding the ciliated canal (Pl. VI. figs. 1-3). In either case the physiological
significance of the arrangement cannot at present be decided.

And to a certain extent this may also be said to be the case with respect to the whole
of the posterior brain-lobe. As long as it went by the name of side-organ—which, how-
ever, did no justice to its intimate connection with the brain—it was generally regarded
as a specific sense-organ of unknown function (Quatrefages, M‘Intosh, &c.). Later on I
published a paper (IX) in which the attempt was made to show that, in a very large number

REPORT ON THE NEMERTEA. 95

of cases, the ciliated canal is adapted to give the oxygenated sea-water access to the
hemoglobiniferous nerve-tissue. At the same time (loc. cit., p. 35) I did not deny all sensory
significance to the organ, but repeated that we had not found any specialised sensory
epithelium in it, and could not judge of what kind the sensory impressions might be that
were carried by the apparatus to the animal’s sensorium. Since then I have been able
to fix the exact mode of origin of the apparatus in at least one species of Nemertea
(XIV, XV), and may here recall to mind that the central lining of the canal most
decidedly takes its origin as an invagination of the epiblast. This invagination second-
arily coalesces with the brain. In these two ontogenetic data we have only very vague
indications. They allow of a comparison both with olfactory and with auditory pits.
Strange as it may seem, I do not see that the first comparison has many more @ priori
arguments for it than the second. Otoliths, it is true, have not been found in this lobe,
but who can tell what purpose the minute concretions, formed by the ensheathing
gland-cells, and sometimes accumulated inside the lumen of the canal, may serve ?

We have, however, to suspend our judgment. Graeffe’s, Keferstein’s, and Claparéde’s
observations on the existence of special otolith capsules in the Nemertea require further
confirmation. They may, perhaps, have mistaken the highly refractive globules in the
gland-cells of the posterior brain-lobe for otoliths.

One more point may be mentioned, viz., that the comparison of the cavity of these
lobes with a branchial slit of Balanoglossus, &c. (cf. Bateson, loc. cit.), which I tenta-
tively attempted in a former paper (IX, p. 33) has to be definitely abandoned, now that
the epiblastic origin of the cavity has been indubitably shown by myself and afterwards
by Salensky (XIV, XXX), and since on this point the statements of earlier authors as to
the hypoblastic origin of this cavity (Barrois, &c.), which led to my former suggestion,
have to be definitely abandoned.

If the comparison with a gill-slit is no longer tenable on morphological grounds, this
in no way changes my views as to the physiological importance that must be attached to
the direct respiratory function of the nerve-tissue, which can nowhere be so perfectly
accomplished as in the posterior canalised lobe. I have no doubt, however, that in some
species—more especially of Hoplonemertea—its significance as an organ of sense may
supersede its importance as a respiratory chamber, the hemoglobin, though present in
these species, being there much more diluted, at any rate colouring the brain less intensely
red, and the connection between posterior and anterior lobes being at the same time less
intimate.

Having now discussed all those parts of the organism which we have any
sometimes even questionable—right to consider as sense-organs, I must pass on to those
which are of a still more dubitable nature, and which fall under the head for which the
further part of the superscription of this section was intended.

Since in some cases I find them in the head and directly innervated by the brain, since

though

96 THE VOYAGE OF H.M.S. CHALLENGER.

in another case they are at the sides of the head stretching backwards for a not incon-
siderable distance, but always exactly at the lateral margin, and because a glandular
epithelium plays an important part in their constitution, there is indeed some, though
of course very distant, analogy with the glandular parts of the posterior brain-lobes which
we have considered before. I do not wish to attach any importance or significance to
this analogy for the present, for we have no sutlicient data; but I mention it by way
of explanation as to how I come to intercalate the description of these parts of the
organism in this place.

The first structure which I have to mention occurs in the head of Drepanophorus
lankesteri, and something analogous to it was noticed by former observers (XVI) in
Geonemertes palaeensis. In the Challenger specimen the horizontal sections through the
precerebral region demonstrate, when viewed with low powers, the presence of a lobulated
mass which is imbedded in the gelatinous ground-substance and partly traversed by
contractile fibres that radiate through the head in so many directions. When higher
powers are applied, this mass is dissolved into groups of cells enclosing more or less
circular free spaces, which, being present in consecutive sections, represent a system of
canals coated by the cells just mentioned, the whole forming a kind of spongy tissue. A
branch by which this canalicular system communicates with the exterior could not be
made out in my specimen, although von Kennel has found such an opening in his
Geonemertes, and thus I do not wish to lay too much stress on the fact of my being
unable to rediscover it in the only Challenger specimen in which I found this structure.
The cells are much more granular and at the same time larger than the surrounding cells
of the intermuscular gelatinous mass ; the nuclei are large and distinct (Pl. XV. fig. 13).
It must be noted that the character of the cells and the aspect of the organ differ very
essentially from von Kennel’s description. It is the situation that is correspondent.

A similar precerebral glandular lobulated organ was found by me in Drepanophorus
rubrostriatus from the Mediterranean, though not in the Challenger specimens of this
species, in which, as was remarked above, the head was deficient. A special innervation
by nerve-fibres belonging to the cerebral nerves was in both cases made out.

The second structure to which I alluded as occurring in Challenger Hoplonemertea
was found by me in the different specimens of Amphiporus moseleyi, both in transverse
and horizontal sections. It may shortly be characterised as being an accumulation of
short, saccular tubes, blind posteriorly and opening to the exterior by a distinct neck,
which pierces muscular layers as well as basement membrane, its internal epithelium then
fusing with the integument. These short flask-like sacs sometimes internally coalesce
with each other, the same interior cavity then communicating outwards by more than
one duct. This, however, appears to be more or less exceptional. They are very
numerous, though short, at the tip of the head (Pl. X. fig. 3, gl.s). They become larger
when we follow them further backwards, where we find them situated laterally in that

REPORT ON THE NEMERTEA. 97

region of the body where the dorsal musculature passes into the ventral, and where the
intervening layer of muscular tissue is either very thin or even (sometimes locally)
absent, at least as a special layer. In every transverse section some three or four of these
glandular flasks are simultaneously cut (Pl. XV. fig. 11). They show no further variety
of structure, but are not found along the whole length of the body. In the hinder half
at least I have not detected them. The histological constitution of these flask-shaped
glands is difficult to make out in the spirit specimens. The epithelium clothing them
had a very much changed and deteriorated aspect, and only in certain favourable regions
could I definitely establish the fact that it was built up of largish cells with large nuclei
(Pl. XV. fig. 12), the contents of the cells being granular like those of the cells of the
median precerebral organ before described. Innervation was not so clearly traced here,
though in the head these flask-shaped organs certainly receive fibres from the very
numerous cerebral branches there present.

Having once determined the presence of the organs just described and their situation,
it was found that their presence is even externally traceable in the specimens of Amphi-
porus moseleyi (see Pl. IX. fig. 8) by a white line running backwards from the tip of the
head along the comparatively sharply edged margin of the body (see pp. 20, 21). Whena
transverse section is made in this region with a razor, the naked eye can trace this white
line extending inwards for a short distance as if the pigment occasioning it were very
thickly applied. Viewed with the microscope, it is then easily seen that this white
spot breaks up into the accumulated flasks as above described, which are surrounded
and supported by the gelatinous tissue. In such a section the latter tissue is much more
transparent and homogeneous, thus bringing out the glands as white lateral spots in this
transparent imbedding mass, in which also the rest of the internal organs may be seen
to be suspended, and which is dorsally and ventrally limited by the body musculature
and the integument.

It may finally be noticed that I have never succeeded in finding the necks of these
flasks that lead to the exterior wholly free and open, as I have the canal of the posterior
brain-lobe or the excretory duct of the nephridia. These very numerous necks of the
flask-shaped organs are always filled with a mass that has a streaked and fibrous appear-
ance. I mention this because it partly contributes to establish my conviction that the
physiological significance may indeed be glandular, and that the secreted, viscid mass,
passing out perhaps more copiously when the animals are immersed in spirit, remains
fixed in this passage to the exterior.

If it be not premature—as I consider it to be—to establish any comparison between
these organs and parts of the organism of Vertebrates, one would certainly be reminded
of those canals in the head which are known as the “Schleimcaniile,” and which are
continued along the sides of the body as the lateral line. The significance which of late
has been more and more definitely assigned to these organs in the Vertebrates, as

(ZOOL. CHALL, EXP.—PaRT Liv.—1887.) Hhbh 13

98 THE VOYAGE OF H.M.S. CHALLENGER.

accessory to the sense-organs forming the system of the lateral line, a sensory epithelium
being protected by and combined with them, has no direct parallel in Amphiporus
moseleyi, although it cannot be denied that the flask-shaped glands are in the immediate
vicinity of and on a level with the lateral nerve-trunks.

The absence of these glandular structures in the Paleeonemertea and Schizonemertea
hitherto observed, renders the suggestion of any close homology very hazardous. Still,
I would not wholly refrain from pointing out the distant kind of parallelism which may
be noticed, and which has certainly contributed to induce me to consider these
organs in the paragraph devoted to the sense-organs, a proceeding which future inves-
tigations may perhaps show to have been wholly unfounded. The significance of this
parallelism will once more be discussed, when, in the chapter of General Considerations,
there is further scope for speculation.

PROBOSCIS AND PROBOSCIDIAN SHEATH.

Concerning this important organ, so very fully described by M‘Intosh in his
Monograph on the group (XIX), the Challenger material has not revealed any startling
peculiarities. Nevertheless, it deserves some closer consideration, because certain points,
e.g., the exact mode of the anterior attachment of the proboscis in these worms, could
be studied more favourably by me in certain of the Challenger sections than ever
before. Moreover, the Russian naturalist Salensky has lately! propounded certain
views concerning the proboscis and its sheath which deserve consideration and refutation.

I will first describe the facts with respect to the proboscis which we notice in the
Challenger Nemertea.

Carinina has a proboscis which, in transverse section, reveals the remarkable
peculiarity that the primitive order of succession, according to which in the body-wall
we meet with (1) integument, (2) longitudinal nerves, (3) musculature, also obtains in
the proboscis, the innervation of which takes place through the intervention of two
longitudinal nerves, which are so situated as to be enclosed by the internal cellular
epithelium (Pl. II. figs. 11, 12), just as is the body nerve-stem in a section of the
trunk. This fact, though it cannot be looked upon as a direct confirmation of the
hypothesis advocated by me after I had become acquainted with Graff's Monograph
on the Rhabdoccela, viz., that in the Nemertea also the proboscis should be looked upon as
a gradual derivative of an original continuation of the body-wall, which has become
introvertible like the snout of the Rhabdoccela proboscidea, still throws a very favourable
light on these views. And this is further the case when we notice that in many Schizo-
nemertea there is also an order of succession of the layers in the proboscis-wall which is

1 Zeitsehr. f. wiss. Zool., Bd. xliii. p. 509.

REPORT ON THE NEMERTEA. 99

similarly more or less a repetition of the same arrangement in the body-wall (Pl. XV.
fig. 2, a’, B’, npl., y’).

In addition to the peculiarity just described, there is another morphological consider-
ation which tends to show that this interpretation of the significance of the proboscis
is indeed the right one. When we consider a horizontal section through the region of
insertion of the proboscis in the head (Pl. III. fig. 5), we see that in Carinina the mode
of fixation of the proboscis is exceedingly simple, its longitudinal muscular coat being in
direct continuity with the longitudinal muscle-layer of the body-wall. Somewhat in
front of the transverse cephalic grooves, about on a level with the anterior brain-lobe,
we see certain of the fibres of this longitudinal coat, instead of pursuing their course
onwards towards the tip of the head, bending inwards, traversing the space which I have
termed (XIII, XV) the archiccele, and then running backwards as the longitudinal fibres
of the proboscis. Other fibres, parallel to those just referred to, do not contribute
towards the formation of the proboscis, but continuing in their original direction, take
part in the formation of the muscular wall of the head (PI. III. fig. 5). It certainly
deserves remark that the same comparatively simple arrangement is met with in the
much more highly differentiated Hoplonemertea, as a glance at fig. 3, Pl. X. will show.
There, too, the longitudinal musculature (a) of the body-wall is partly continued towards
the tip of the head, where it partly bends round and largely contributes to the formation
of the muscular layers of the proboscis. I suppose this way of stating the facts is more
in accordance with their actual relations, than to say that the longitudinal musculature
of the proboscis is internally inserted upon that of the body. Here also the direct
continuity of body-wall and proboscidian-wall, the latter appearing merely as an inverted
portion of the former, is forced upon our attention, as is in the same way the direct
continuity of the exterior integument J, through that of the rhynchodeum Rh to that
which clothes the proboscis itself, and which on the eversion of that organ forms the
exterior surface.

We must now consider these different parts more in detail. Commencing with the
rhynchodeeum (cf. p. 8), we find in the Paleeonemertea and Schizonemertea its walls bathed
by the blood-spaces in the head, as may be gathered from a comparison of the figures in
Oudemans’ paper (KXVII) on the blood-vascular system. This is no longer the case in
the Hoplonemertea, where these blood-spaces are replaced by the distinct vascular loops.
The proboscidian walls, fusing anteriorly with the musculature and the external epithe-
lium of the head, are different in the different subdivisions. Contractile fibres and cellular
elements, the materials of which the rhynchodzeum is built up, are present in Carinina
in quite a different relation from that in which they occur in Cerebratulus or Am phiporus.

In Carinina, as a glance at Pl. III. fig. 5 will show, it is the cellular elements (4 Pe)
that are extremely preponderant. These cells are vacuolated, more than one layer thick,
different in aspect from the true proboscidian epithelium, and held together by a fibrous

100 THE VOYAGE OF H.M.S. CHALLENGER.

coating, which is attached by radial fibrous bands to the cephalic musculature. The
rhynchodeum is thus suspended in the cephalic blood-space, as was formerly (IX)
described by me in Carinella.

The histological difference between the vacuolated cells of the rhynchodeeum of
Carinina and the cells of the outer integument, is less than that between the former and
the epithelium of the proboscis proper.

A comparison between figs. 3, 4 of Pl. IIL, fig. 1 of Pl. IV., and figs. 1-3 of Pl. VI. will
sufficiently demonstrate this, vacuolated cells playing a very prominent part in the outer
strata of the integument in Carinina. Still the three epithelia (external, rhynchodeeal,
and proboscidian) are immediately contiguous, the passage from the one to the other
being gradual and only in the latter case relatively abrupt.

In the rhynchodzeum of the Schizonemertea and Hoplonemertea the cellular and ciliated
layer of the rhynchodzeum of the earliest Paleeonemertea has been relegated to the back-
ground, and the whole has become more a muscular sheath, in which the muscles have,
however, a different arrangement in the first and in the second group. The increase in
muscularity is in the Schizonemertea more a regular thickening of the fibrous investment,
whereas in the Hoplonemertea it is much more massive in one region than in the other.
In this way an annular and massive muscular sphincter (as it may be adequately termed)
arises in the posterior part of the rhynchodeeum (Pl. X. fig. 3, Sp. Pr.).

In this muscular sphincter longitudinal and circular fibres are very intimately inter-
woven, more or less in basket fashion, as indicated in the figure. Moreover, the
connection with the general musculature of the head is again brought about by radial
bundles, also visible in the figure.

Of the Schizonemertean rhynchodzeum no special figure is given; it answers to the
short description which was given above, it can be well observed in several figures in
M‘Intosh’s monograph, and, like the rhynchodeeum of the other groups, it reaches back-
wards just as far as the implantation of the proboscis in the musculature of the head.
The epithelium of the rhynchodzeum is in most cases distinctly ciliated.

The proboscis itself has been the subject of so detailed study and so elaborate
description by M‘Intosh and other investigators, that I must necessarily restrict myself
to those few points on which the Challenger material furnishes certain deviations or
additions.

The inner epithelium of the proboscis of Carinina shows considerable differences
according to the region under observation. In front there are papillee of a more or less
arborescent shape, on which a coating of fairly large cells, with distinct nuclei, and
partly vacuolated, is present. Posteriorly the cells are lower and more closely set (PI.
III. figs. 1, 2, Pe). This may be partially the result of a different state of contraction,
by which the anterior portion is thrown more into folds.

The difference is, on the other hand, further accentuated by the presence of a con-

REPORT ON THE NEMERTEA. 101

striction in the proboscis, which I observed in the longitudinal sections of the only specimen
of Carinina that had retained its proboscis.

I cannot affirm that this constriction was natural, 7.e., that it would also be found in
fresh specimens. Since, however, I have formerly described (VIZ) similar constric-
tions in the proboscis of Carinella and Valencinia, there are many @ priori grounds
for also accepting its normal occurrence in Carinina. At the same time it more or less
coincides with the change in the character of the epithelium just noticed.

The epithelium of the proboscis of certain Schizonemertea was known to be charac-
terised by the presence of nematocysts. In a former publication (VII) I showed that
the observation of Max Miiller, who first noticed urticating elements in Cerebratulus
urticans, might be extended to nearly all Schizonemertea, although the size of these
elements is generally considerably below that of the type species just mentioned,
Miiller has given good figures of the shape of the elements in his species; of the others
no figures have hitherto been given, and fig. 2 of Pl. XV. is intended to show the situa-
tion of packets of urticating elements, batteries, as they might be called, in a transverse
section of the anterior part of the proboscis, rather than to furnish particulars concerning
the histology of these nematocysts. They are seen to be situated close to the free surface
of the cells, and to be of different sizes on the dorsal and on the ventral surface of the
proboscis. Three batteries are figured lying free in the lumen of the proboscis; when
seen from the side they have the aspect of a brush with close hairs seen in the same way,
when seen from above they appear to be more or less circular, and each of the elements
composing the battery is then found to be represented by a fine dot instead of by a
straight line, as was the case in the side view.

In the spirit specimens of Cerebratulus more than these general facts could not be ascer-
tained. I may add that fresh specimens from the Mediterranean showed that each of the
elements out of which such a battery is composed has a spindle-shaped form, being more
or less pointed at both ends and somewhat bulging in the middle, and that from one of
the pointed ends—which in its natural position is directed away from the proboscidian
epithelium—the fine urticating thread may be observed to issue. This thread is, in most
cases, comparatively short. While in Cerebratulus urticans there is hardly any doubt
that each urticating element may act independently of the others, it is not improbable that
in some species, as the one here described, they remain connected in batteries by whose
joint action, when the proboscis is projected, delicate animals may be wounded or para-
lysed upon extrusion of the proboscis, and may thus fall an easy prey to the proprietor
of this formidable weapon.

As to the more detailed histology of this epithelium, I wish to withhold further remarks
till I am enabled to publish the observations on the fresh specimens examined at Naples.
Similarly the curious and very adhesive epithelium of the foremost portion of the
Hoplonemertean proboscis which I have formerly described (IV, V), which was well

102 THE VOYAGE OF H.M.S. CHALLENGER.

known to M‘Intosh, Graff, and other observers, and which I have again met with in
the Challenger Hoplonomertea, cannot be more circumstantially described. Moreover,
the stylets in the different Hoplonemertea did not offer any remarkable deviation from
the well-known type, and though the transverse sections gave very clear details regarding
the arrangement of the muscle-fibres in the muscular bulb, about the epithelium of the
glandular duct that conveys the probably venomous secretion of the posterior cavity to
the base of the stylet, &c., these are only confirmations of facts already known and
need not be recapitulated here. The shape of the stylets was mentioned when the
species were described; those of Drepanophorus, though not obtained from an actual
Challenger specimen, are represented in the woodcut on p. 16.

The muscular walls of the proboscis differ in the various genera, and these differences
speak for themselves when we compare figs. 11 and 12 of Pl. IL, and figs. 1, 2, and 5
of Pl. IIL. (Carinina), fig. 11 of Pl. VI. (Eupolia), fig. 7 of Pl. VIII. (Pelagonemertes),
fig. 6 of Pl. XIL (Amphiporus), and figs. 2 and 3 of Pl. XV. (Cerebratulus). These latter
show the muscular layers of the proboscis of the Schizonemertea to be a repetition of the
muscular layers of their body-wall: a circular layer between two longitudinal ones, the
circular layer giving off fibres at diametrically opposite poles to the external membranous
sheath (b), and moreover, a nervous plexus (7. pl), which is also situated between the outer
longitudinal muscular coat y’ (that just below the epithelium), and the circular one f’.
This nerve-plexus does not go all round, at least it cannot be distinctly made out except
throughout one-half of the circumference. It is also traversed by radial fibres, and is again
replaced by definite longitudinal stems when we examine a transverse section of the
proboscis further back (Pl. XV. fig. 3). These longitudinal stems are characteristic of
certain species of Cerebratulus, and a plexus, even a far more complete and cylindrical
one than the one figured (Pl. XV. fig. 2) for Cerebratulus macroren, is characteristic of
others. The nerve-stems enter the proboscis at its point of insertion, and spring from
the right and left extremity of the ventral brain commissure.

In the posterior regions of the proboscis of Hupolia, of Pelagonemertes, and of nearly
all the other species, the musculature appears to be reduced to a simple longitudinal
layer, carrying the epithelium on one side, and being held together by an ensheathing
membrane on the other (PI. VI. fig. 11, and Pl. VIIL fig. 7).

In Carinina there is an additional circular layer, and the remarkable fact, which has
been already noticed above, of the situation of the nerves still enclosed in the epithelium.

In Amphiporus, Drepanophorus, and Pelagonemertes (anterior portion) the
proboscis-wall exhibits the notable complications corresponding with the curious dis-
position of the nerves in the proboscis, and which was described in sufficient detail
by M‘Intosh (beaded layer) (XIX, XX), myself (EX), von Kennel (XVI), and
Graff (111). To von Kennel the merit is due of having definitely established
the nervous significance of the parts in question. The innervation may here be

REPORT ON THE NEMERTEA. 103

said to represent a plexus with numerous longitudinal thickened portions or stems.
The passage of the nerves from the brain into the proboscis can very rarely be well
observed, because the proboscis is nearly always extruded and torn off when the
animal is killed. I may, however, repeat what was noticed above (p. 85), viz., that in
Amphiporus moseleyi, more particularly, this doubt has now been dispelled. I can
observe in my sections that, instead of two strong nerves innervating the proboscis, as
in the Paleonemertea and Schizonemertea, a much larger number of branches leave
the brain-ring and enter the proboscis in the region of its attachment. That these may
dichotomise and give rise to a larger number of longitudinal stems has been already
stated by von Kennel (XVI).

This nervous plexus and the longitudinal stems subdivide the longitudinal muscle-
layer into an outer and an inner portion, the latter (when the proboscis is everted) being
again subdivided into as many longitudinal columns as there are nerve-stems in the
proboscis (Pl. XII. fig. 6). Outside and inside of this longitudinal layer there is a
circular layer of fibres, outside of the exterior one of these the epithelium.

As to the nerve-stems and the plexus, one specimen of Amphiporus marioni showed
very distinct cellular accumulations just between each nerve-stem, as if a longitudinal
tract of nerve-cells alternated with one of nerve-fibres in the plexus. For the study of this
phenomenon fresh specimens will be absolutely necessary. The phenomenon itself has
been already noticed, but has not yet been wholly understood, either by von Kennel (XVI)
or by Graff (ITT).

Just as it has been necessary to curtail our observations on the proboscis because of
the detailed information already available concerning this important organ, the probos-
cidian sheath need not be treated at any length in view of the data that are already furnished
by others. It is known to be a closed space surrounding the proboscis, having in the
majority of cases its own muscular wall, by the contractions of which the fluid contained
in the space is driven against the anterior proboscidian attachment. The muscular
sheath thus serves to protrude the proboscis as far as the length of the posterior portion
—acting as a retractor-muscle—will allow it.

There can hardly be any doubt, when we take into consideration all the morpholo-
gical data at our disposal, that the muscles composing the proboscidian sheath gradually
took their origin by the increase and modification of pre-existing muscular elements,
which belonged to the body-wall and to the body-parenchyma before the proboscis,
modified from a tactile organ, as it appears to have primitively been, had yet become
evolved, through the growth inwards of the anterior tip of the body, into an aggressive
weapon, with stylet or nematocysts, &e. We find the shorter proboscides, and the less
significant proboscidian sheaths among the more primitive genera of Nemertea.

Carinella has a short proboscis ; the dorsal wall of its sheath is still a component part
of the musculature of the body-wall; the ventral wall is thin, and only composed of a

104 THE VOYAGE OF H.M.S. CHALLENGER.

few fibres. So it isin Carinina (PI. IL figs. 3, 6,7, 9,10; Pl. IV. fig. 6, Ps). In Eupolia
the proboscis is longer, but the sheath is still most insignificant, as may be gathered from
the figures (Pl. VI. figs. 9,10; Pl. VII. fig. 10). It is a space having internally a cellular
coating very similar to that of the blood-spaces, the cells of this internal epithelial covering
often more or less projecting into the lumen of the sheath. Outside of these cells a few
circular fibres are seen to have developed ; outside of these there is again the body-paren-
chyma, with the enclosed blood-lacunee. There is no doubt that from sections of Hupolia
alone nobody would be inclined to look upon the cavity of the proboscidian sheath as a
very independent cavity, nor is it possible to affirm that the mode of the protrusion of
the proboscis, as it was sketched above, is indeed fully developed in Hupolia and
Carinella. There is no doubt that of all Nemertea observed alive, these two were
never seen to protrude their proboscis spontaneously, and very often even preserved
them in death, when the Hoplonemertea always forcibly expel and even spontaneously
detach their proboscis.

There is, on the other hand, no evidence at all which would justify us in regarding
the arrangement of these Paleonemertea as secondary or degenerated from a higher
differentiated stage. The participation of the body musculature in bringing about
the movements of the proboscis in these lower forms renders this more intelligible.
Only in the more highly differentiated Schizonemertea, and especially in the Hoplo-
nemertea, the muscular walls of the proboscidian sheath undergo a very rapid increase
in bulk, and at the same time become more and more, and in the last-named group
even wholly independent of the body musculature. This increase of an organ so
eminently mesoblastic as the proboscidian sheath, by gradual addition of new fibres that
are even arranged in multiple layers, can thus be traced in all its various stages in the
different genera of Nemertea. Salensky would probably not have made his startling
hypothesis above alluded to, based on ontogenetical observations of a scission in the
proboscidian wall, by which (1) a muscular proboscidian sheath surrounding the proboscis
becomes separated from, and independent of, the musculature of the proboscis itself, and
(2) an isolated coelome—the proboseidian cavity—is originated, if he had been as well
acquainted with the comparative anatomy of the animals about which he writes as he is
with certain details of their ontogeny.

Granting even that the development may, in the species observed by him,
follow the paths he has sketched (my own observations on the ontogeny of Lineus
obscurus (XIV) have led to wholly different results on this head), it is not yet per-
missible to base upon those two ontogenetic observations phylogenetic speculations
wholly at variance with all the facts that are furnished by a comparison of the different
living genera. The woodcuts given by Salensky, in which a Rhabdoccele proboscis and a
Nemertean one are put side by side, look very tempting, but cannot be accepted by me.

1 Archives de Biologie, vol. v. p. 561 ; Zeitschr. f. wiss. Zool., Bd. xliii. p. 508.

REPORT ON THE NEMERTEA. 105

While fully recognising the importance of Graff's observations for our own interpretation
of the Nemertean proboscis, and the genetic relation of this organ to that of the Rhab-
docceles (not direct but collateral), I must as emphatically reject the proposed derivation
of the proboscidian sheath advocated by Salensky.

We must, indeed, represent to ourselves the gradual evolution of the proboscis as
that of an epiblastic organ reaching further and further inwards in successive genera-
tions, and strengthened and completed by a mesoblastic musculature ; and outside of this
the free and independent development out of other mesoblastic elements (primarily
belonging to the body-wall) of the sheath. It has been already noticed elsewhere (XIV,
XV), that if these mesoblastie structures could be traced down to amceboid mesoblast
cells derived im loco out of the subjacent hypoblast, an ontogenetic homology between
the tissues constituting the proboscidian sheath and those forming the notochord of
Vertebrates would be established.

Returning to the proboscidian sheath of the Schizonemertea, we find it to consist of
an outer layer of circular fibres and an inner one of longitudinal (PI. X. fig. 8, m Prs ;
Pl. XV. fig. 1). The former sometimes, when the sheath is thick and contracted, shows
a wavy line. Radial fibres, piercing the two fibrous layers, insert themselves against the
inner epithelium, which covers the whole inner surface, looking towards the cavity of the
proboscidian sheath. Between this epithelium and the muscular layers there is a broad
band of transparent basement tissue (Pl. XV. fig. 1, 6) following the numerous longitu-
dinal folds of the epithelium just mentioned. These folds disappear when the proboscidian
sheath is in distension (Pl. X. fig. 8), a phase that may repeatedly be noticed, even
without any extrusion of the proboscis, e.g., as a consequence of complicated coilings of
the proboscis inside its sheath. It is easily understood that during such distension the
thickness of the subepithelial homogeneous basement layer and of the muscular layers is
considerably reduced. A maximum degree of distension is figured on PI. X. fig. 9, where
the epithelium was no longer separately visible, and even the cesophageal epithelium has
been flattened out, together with the proboscidian-sheath wall.

As will be seen from Pl. XV. fig. 1, we find outside of the outer circular layer of the
sheath the gelatinous body-parenchyma, a thin layer of this even separating the probos-
cidian sheath from the longitudinal muscular layer a, in the midst of which we notice the
true proboscidian-sheath-nerve (pr.sn). In addition, I think it is not unimportant to
remark, that just below this layer of longitudinal fibres, there are strands of circular fibres
which do not apparently belong to the proboscidian sheath, and which, after having been
closely applied against the dorsal musculature in the middle line of the back, radiate
amongst the parenchyma and the intestinal ceca. It is these fibres (and perhaps in
addition to them the circular layer of the sheath itself) which may possibly be looked
upon as representative of the layer § in the Carinellide (cf. Pl. XI.), and which there takes

such a conspicuous part in the dorsal delimitation of the proboscidian sheath.
(ZOOL. CHALL. EXP.—PaRT LIv.—1887.) Hhbh 14

106 THE VOYAGE OF H.M.S. CHALLENGER.

In many Schizonemertea the proboscidian sheath is thus constituted ; in others I find
that a phenomenon, which receives its more final expression in certain Hoplonemertea,
is not wholly absent—I mean the presence of varicosities, in which the inner space of
the sheath is bulged out, without the musculature following. In this way more or less
irregular appendages are brought about, generally along the side or the lower corners,
having the aspect of accessory reservoirs. In Cerebratulus sp. inc. (Pl. XV. fig. 6),
from Japan, it seems as if these appendages in the posterior region of the body
even surpass in size the sheath itself, which is not a very significant organ in that
region of the body, and, moreover, as if these two ceca are filled with a sub-
stance of the nature of which the available spirit specimens do not enable me to
judge.

I do not wish to discuss here the significance of these facts, not having for the present
sufficient material to study them more fully; it is only my purpose to call the attention
of future investigators to the phenomenon, which may be so significant for a correct inter-
pretation of the posterior, often semi-rudimentary portion of the proboscidian sheath.

It has been observed that in certain Hoplonemertea the phenomenon just noticed
finds a more definite and more regular expression. The first observation of this is due to
M‘Intosh, who detected in the proboscidian sheath of Drepanophorus reeular metameri-
cally placed openings, by which the space inside the muscular sheath communicated with
other cavities outside of it, that had no muscular walls (KX).

While M‘Intosh supposed these accessory cavities to establish a communication
between the cavity of the proboscidian sheath and the blood-vascular system, I have
since demonstrated (VIZ) that no such communication exists, but that Drepanophorus
possesses closed membranous sacs communicating with the proboscidian sheath, and
probably serving as reserve spaces for the fluid contents of the proboscidian sheath
during the very powerful contractions and distentions which the organ may undergo. In
the Challenger specimens the same phenomenon was observed, and I have even ventured to
assign all those specimens in which these recular paired appendages of the proboscidian
sheath were found to the genus Drepanophorus, even when I have not succeeded in deter-
mining the armature of the proboscis so characteristic of the genus.

Two sections through the proboscidian sheath of Challenger Drepanophori are figured
on Pl. X. figs. 4, 5.

The curious arrangement of circular and longitudinal fibres, having the appearance of
basket-work in the transverse section, may be understood from these figures, even without
any further description.

Between the musculature and the inner epithelial layer there is again a homogeneous
membrane, with longitudinal folds indicative of the contracted state in which the sheath
here figured was at the moment of its.preservation. In neither of the two was the section
quite vertical, thus only one of the lateral diverticula is cut, instead of the pair that are

REPORT ON THE NEMERTEA. 107

opposite each other. The epithelium which coats the internal cavity of the sheath is seen
to be continued uninterruptedly in these lateral spaces, whereas the musculature is deficient,
and these ceca may thus with propriety be called membranous. There is a decidedly
thicker epithelial coating in the lateral sacs of fig. 4 (Drepanophorus lankesteri) than in
those of fig. 5 (Drepanophorus serraticollis). On the other hand, the musculature of the
proboscidian sheath of the latter is much more massively developed than that of the
former.

One remarkable detail concerning the lateral appendages in Drepanophorus lan-
kesteri, is the fact that I found a few of the anterior ones connected by a short longitu-
dinal communicating tube at their distal extremity, this connection being thus parallel to
the proboscidian sheath itself. Similar connections were not noted further backwards, nor
in any other species of Drepanophorus.

While the proboscidian sheath of Amphiporus marioni (Pl. X. fig. 1) is built on
the same plan as that of Drepanophorus, that of Pelagonemertes is seen to be much
simpler (Pl. VIII. fig. 7). Both are quite freely suspended in the gelatinous tissue,
and only connected with the body musculature in the head (PI. X. fig. 3).

DIGESTIVE APPARATUS.

The digestive canal of the Nemertea cannot be said, from a morphological point of
view, to be very complicated.

Communicating with the exterior by a ventral mouth close behind the tip of the
head and by a terminal anus, it stretches along the whole length of the body, and only two
rather sharply defined regions may be distinguished in it: the cesophagus and the hind
gut or intestine proper. Still, even the mouth is not always an independent structure,
as it is known to become confluent with the opening through which the proboscis pro-
trudes, 7.e., the terminal opening of the rhynchodzeum," in at least two genera (Amphiporus
and Malacobdella?). In that case this common opening is either terminal or nearly so
(Pl. IX. fig. 9), and generally larger than the separate openings in other Hoplonemertea.
This feature is clearly not primitive but derived from that condition in which the mouth
lies behind the brain-lobes on the ventral surface, as it does in the most primitive

1 Rhynchodeum (see p. 8) is the name that may conveniently be given to the passage stretching from the point of
insertion of the proboscis in the head to the level of the exterior opening on the surface of the body through which the
proboscis is seen to be thrust forth. Its walls are marked A Pe in fig. 5 of Pl. IIL; RA. and Sp. Pr. in fig. 3, Pl. X.

? Salensky has lately (Biologisches Centralblatt, 1883, p.740,and Archives de Biologie, vol. v.), in publishing embryo-
logical researches on a certain species of Nemertea, imagined that the feature here alluded to was then and there
discovered by him for the first time, and necessitated the creation of a new genus (Monopora). Although his attention
was drawn to the superfluity of this proceeding (XIV. p. 41), he still retains the name in a later publication (Zeztschr. f.
wiss. Zool., Bd. xliii. p. 481). Still, I am afraid this will not extend its longevity, as all the other anatomical characters
most decidedly conform to Amphiporus.

108 THE VOYAGE OF H.M.S. CHALLENGER.

Carinellidee and in the Schizonemertea, in fact in all Nemertea, with the exception of
the Hoplonemertea. In the latter the mouth is always in front of the brain; it has
thus shifted forwards, the extreme range of this shifting process being reached when
the mouth becomes confluent with the opening of the rhynchodzeum just recorded.

Another difference between the Hoplonemertea and the two other orders of the class,
with respect to the digestive system, is found in the relative position of the cesophagus and
hind-gut. While in the two last-named groups these two subdivisions of the intestine
pass into each other along astraight line and do not overlap, we see that such an overlap-
ping does occur to a more or less considerable extent in the Hoplonemertea. Ina number
of transverse sections the hind-gut is cut when the cesophagus is also still present in the
section, showing that the latter overlaps the former. Still, I should be inclined to adopt
the view that the gradual process by which this came about was not so much a further
extension backwards of the cesophagus, as a tendency of the hind-gut to spread out
and to reach forwards below the cesophagus. This would seem to be indicated by the
fact that in these Hoplonemertea the intestinal ceeca, that properly belong to the hind-
cut, but that have come to be situated below the cesophagus (PI. XV. fig. 20), may even
reach so far forwards as to become situated close to the brain-lobes, a phenomenon which
is never observed in the lower groups, where the whole length of the esophagus separates
the brain-lobes from the hind-gut. Possibly the shifting forwards of the hind-gut and
its diverticula may be a phenomenon that runs parallel with (if not due to the same cause
as) the disappearance of the lacunar blood-spaces round the cesophagus, and the substitu-
tion for them of cylindrical blood-vessels communicating by transverse ducts with the
medio-dorsal vessel. The latter arrangement is also typical of the region of the hind-
gut im the Schizonemertea, where, however, the circumcesophageal portion of the blood-
system is eminently lacunar.

These speculations need not, however, be further insisted upon, and we may now
pass to a description of the cesophagus in the Challenger Paleeonemertea. Here, again,
Carinina offers features of interest. In the first place, the exceedingly close application
of the cesophageal epithelium against the muscular body-wall below and the thin muscular
layer of the proboscidian sheath above is peculiar (Pl. IV. fig. 3). There is no gelatinous
connective tissue between the cells and the bundles of circular muscles, not even a base-
ment membrane, and strong powers are wanted to demonstrate any intervening tissue
between the bundles themselves, so strongly are they interwoven, and so dense are the
muscular layers in this region of the body-wall. Anteriorly there is a sharp bend down-
wards where the mouth is situated, and in front of this a short bulging out forms a
prostomial extension to the cesophagus, which is seen to be cut through in Pl. II. fig. 3.

The cells of the cesophagus, as seen from the section figured, are finely granular, and
below those which actually clothe the lumen there are sometimes seen others also with
large nuclei (Pl. IV. fig. 7) but less granular and with less distinct boundaries. This

REPORT ON THE NEMERTEA. 109

ficure at the same time reveals the presence of a conspicuous cuticula covering the free
surface of the cesophageal cells. It is not streaked, as the figure erroneously indicates,
but homogeneous. On it the cilia are implanted.

Concerning the behaviour of the intestine in the posterior body-regions of Carinina,
nothing can be said, as only anterior fragments were preserved.

In Eupolia the cesophagus has become more independent of the body-musculature
than in Carinina, and in addition to this a separate cesophageal musculature—at least
in Eupolia giardii—is present (Pl. VI. fig. 9, 0e.m). In this cesophageal muscular
investment an inner longitudinal and an outer circular layer may be distinguished ;
between the latter and the body-wall there is the gelatinous tissue, only locally inter-
rupted by the lacunar spaces of the vascular system (in which the nephridia [np] are
suspended), by the dorsal blood-vessel, and by the proboscidian sheath. I mention this,
because there is no evidence that this splanchnic musculature has directly evolved out of
hypoblastic elements, whereas the evidence that it is enclosed in one continuous stroma
with the ‘‘ somatic” musculature—which in Carinina was the only musculature noticed—
and not separated from this by a body-cavity, is very complete. It should, moreover,
be remarked that where this more prominent intestinal musculature makes its appear-
ance (certain Schizonemertea, Hupolia giardi, &c.), the internal circular muscular layer of
the body-wall of the Carinellide (6, Pl. XI.) is no longer present in that situation.
How far thése two may be considered as homologous, must be left undecided as long as
we do not possess more complete ontogenetical data. This cesophageal musculature
was not noticed in all species of Euwpolia, and it is certainly curious that it should be
present in Lupolia giardii, where the body musculature is so exceptionally thick, and
might be expected to serve the purpose of compressing and dilating the cesophageal wall
quite as efficiently as we must suppose this body musculature to do in the Carinellidee.
M‘Intosh, who detected it in Cerebratulus corrugatus, suggests (KXII) that the
oesophageal musculature might assist in a partial protrusion of the cesophagus.

In Eupolia nipponensis and Eupolia australis this special musculature is absent,
and we find, on the contrary, a much more considerable development of the deeper cellular
layers of the cesophageal wall (Pl. VII. fig. 12), and a comparatively sharp demarcation
between the internal ciliated epithelium (Je) and this thick cellular coating (Jm), this
demarcation even sometimes rising to the importance of an apparent basement membrane
(B). Between these cells radial fibres, starting from the body musculature, penetrate, and
solitary tangential fibres may be observed, but a separate muscular investment of the
cesophagus can never be shown to exist. I am not inclined to believe that this difference
may be caused by the age or the size of the individual, one of the specimens of Hupolia
nipponensis being indeed of considerable size and nearly as thick as Eupolia giardia.

The same deep cell-layer is met with in the cesophagus of the Schizonemertea
(Pl. XIII. fig. 6), and is no doubt of glandular significance. Generally many of the

110 THE VOYAGE OF H.M.S. CHALLENGER.

component cells are flask-shaped, the thinner extremity shoving in between the pallisade-
shaped inner ciliated epithelium. Moreover, among the Schizonemertea there appear to
be differences in the development of muscular tissue in the cesophageal wall, sometimes
the cireumeesophageal blood-lacuna directly bathing this cellular coating, sometimes
(eg., Cerebratulus corrugatus) a special muscular investment of conspicuous development
(Pl. XIII. fig. 6, mto) being again present together with very strong nerves (7).

The passage from the cesophagus to the sacculated intestine is more or less gradual, in
the absence of any forward extension of the latter below the former, as was noticed for
the Hoplonemertea.

Macroscopic dissection enables us, nevertheless, to make a clear distinction between
these two portions of the gut, although microscopic investigation of transverse sections
shows that, histologically speaking, the passage is tolerably gradual. The cell layers of
the posterior portion of the intestine have been more than once sufficiently described
(see von Kennel (XVI), pl. xviii. fig. 11), and it is not always easy to show them to
be provided with a nucleus or with cilia. Still 1 do not hesitate to declare that the
whole of the intestine is ciliated, both the central passage and the lateral, generally sym-
metrical ceca. But this ciliation is often rendered inconspicuous by the fact that the
very elongated cells, composing the wall of this portion of the gut, are so overfilled with
small spherical globules as not only to render the ciliation invisible, but even to efface the
traces of the boundaries between the cells, so that in certain cases—both amongst Schizo-
nemertea and Hoplonemertea

it would seem as if the intestinal wall were replaced by a
compact mass of those globules enclosing the intestinal lumen between them. Similar
phenomena were observed by Lang (XVIII) in the Polyclada, and have been described
by other naturalists for other groups of Invertebrates. I will not here enter upon the
question of the relation of this phenomenon to the process of intracellular digestion, which
on a priori grounds may also be presumed to exist in the Nemertea, but will only add
that the nuclei of these high and elongated cells may in favourable specimens be
discerned, and are deeply situated, far away from the surface.

Whilst strong vertical muscle-fibres pass from the dorsal to the ventral body-wall in
a lamellar arrangement, thus constituting what I have termed in a former publication (V)
the muscular dissepiments, placed alternately between the intestinal ceca, these czeca
themselves are destitute of any special musculature. The muscular lamellee just men-
tioned, together with the general body musculature, appear to be sufficient to bring
about all the contractions in the intestinal wall needed for the progress along this
channel of the food swallowed. The intestinal epithelium itself is thus directly implanted
upon the gelatinous tissue, and this phenomenon is no less clear in the Schizonemertea
than in the Hoplonemertea (Pl. VIII. fig. 3; Pl. IX. figs. 1-6; Pl. XV. figs. 7, 10).
Among the latter Pelagonemertes is the most striking example of this, because of the
preponderance of the gelatinous tissue. It has been already noticed in a preceding

REPORT ON THE NEMERTEA. 111

paragraph that this jelly appears to be somewhat denser, and that at any rate it
more strongly imbibes staining reagents, all round the circumference of the intestinal
epithelium where this is implanted upon it.

As to the cesophagus of the Hoplonemertea, I wish to observe that it is less thick and
massive than that of Hupolia and the Schizonemertea, and more resembles the simple
arrangement of Carinina. Its wall is generally only one cell-layer thick, and a distinct
cuticula, as was noticed in Carinina, may also be often observed here. Fig. 1, Oe, of
Pl. X., representing a section of the cesophacus of Amphiporus marioni, gives a very fair
representation of it. Outside the cesophageal epithelium there are indicated in this figure a
layer of flattened cells which I at first expected to form an outer tunic to the cesophagus.
Closer investigation revealed the presence of these cells in all the tissues—they may also
be seen in the basement layer 6 of the same figure—and at the same time convinced me
that these unicellular bodies are parasitic organisms. They infest all the tissues of
their host, and are more abundantly heaped together just outside the cesophageal
epithelium, where nutritive substances may be expected to be more plentiful. Curiously
enough, they were also noticed in the smaller specimens of Amphiporus mariont.
Similar cases of specimens of Nemertea infected with unicellular parasites were noticed
by me on other occasions. There is another case amongst the Challenger material (see
p- 48), but there the parasite is much larger than in Amphiporus marioni, and
altogether differently constituted. It agrees with the former only in the fact of its
presence in all parts of the tissues.

These parasites differ from others which are found in the lumen of the intestine, and
which have already been noticed by former observers.

Another view of the Hoplonemertean cesophagus is given (in longitudinal section)
in Pl. XV. fig. 20. Here, too, the comparative thinness of the walls is conspicuous,
and the connection with the posterior gut portion which stretches forwards under it,
is clearly indicated.

In Pelagonemertes the last mentioned phenomenon could not be observed. The sec-
tions through the mouth and cesophagus were, however, not intact, because of the macro-
scopic dissection to which the specimen had previously been subjected by M‘Intosh.

As to the ceca of the posterior body region little remains to be noticed, but that they
are more regularly distributed as we approach the tail, 7.e., the region where new ceca
are being continually formed. Their metameric and paired arrangement is here more
evident than further forwards, where the degree in which they are filled with food par-
ticles may be more or less different, and may thereby become the cause of a partial, but
not very common, asymmetry.

The innervation of the intestine was for the greater part described in the paragraph
treating of the nervous system. It may be remarked here, in addition, that in transverse
sections of the foremost portions of the cesophagus it is very easy to detect the consider-

112 THE VOYAGE OF H.M.S. CHALLENGER.

able nerve-stems, both of the vagus nerve and of the visceral nerves, by which this is
brought about, and that in longitudinal sections also (PI. XIV. fig. 5) the vagus nerve
may often be followed uninterruptedly for a very considerable distance backwards, being
applied upon the outer surface of the cesophagus, and only gradually dichotomising and
sending delicate nerve-fibres amongst the cesophageal epithelium (cf: Pl, XVI. fig. 1).

Of the two sources of innervation of the intestine, the one by the nerve-stem directly
issuing from the brain-lobes (the so-called vagus nerve) is the most conspicuous, and can
be demonstrated in all species from Carimina to the more specialised Hoplonemertea
without exception. In Carinina it is represented in Pl. VI. fig. 1, Nv; in this species
the visceral nerves (Pl. XVI. fig. 1, w.sy; Pl XIV. figs. 3, 4, vi.) have not been
definitely demonstrated as yet in either of the two available fragments. These latter
nerves are more easily detected in larger Schizonemertea, where the thick nerve-plexus
is itself so much more conspicuous. Cerebratulus corrugatus especially answers this
purpose,

In the Hoplonemertea too the vagus is very evident, and already represented on
Quatrefages’ figures (XXVIII); in Drepanophorus lankesteri I saw its principal stem
running forwards towards the anterior cesophageal portion that passes under the
brain.

In this species we find numerous thin nerves, both from the lower brain-lobes and the
lateral stems, further participating in the innervation of the cesophagus—a state of things
which may be directly compared to the mixed innervation described above for Cere-
bratulus corrugatus.

I cannot as yet supply any definite statement regarding the innervation of the
posterior region of the intestine.

NEPHRIDIAL APPARATUS AND BLOOD-VASCULAR SYSTEM.

Our knowledge of the nephridia of the Nemertea is only of a comparatively recent
date. Though discovered by Max Schultze as early as 1851 in a Tetrastemma (XXXII),
the observations of this naturalist concerning the Nemertean nephridia were for a long ,
time wholly unjustifiably disregarded, and this general scepticism made me very careful
in formulating any definite opinion, when I also discovered in Schizonemertea separate
lumina (IV), which I could hardly account for in any other way than by regarding them
as parts of a nephridial system.

This was afterwards more emphatically done by von Kennel (XVI), to whom is due
all the credit of having rediscovered the nephridia, and of having described their histo-
logical appearance in several different genera. His results were later on confirmed by other
authors (II, III, XI). I have afterwards observed and described (XII) a special modifica-
tion of the nephridial system in Nemertea, in which an indubitable internal opening is

REPORT ON THE NEMERTEA. 115

present. This was found by me in the nephridial system of Carinoma, and these nephridia
thus establish a communication between the internal blood-spaces (archiccelome) and the
exterior. In other genera, Carinella excepted, similar internal communications were,
however, sought for in vain. A very notable and exhaustive contribution to our
knowledge of the Nemertean nephridia was then furnished: by Oudemans (KXVII), and the
Challenger material, which was partly made subservient to that publication, only furnishes
a few additional data here worth recording, most of the peculiarities having been already
mentioned by Oudemans. I hold it to be one of the principal results arrived at by this
author, that he definitely demonstrated the presence in numerous species of Nemertea of
a very large number of exterior openings, connected by short transverse branches with
the principal and longitudinal canals of the nephridial system, and that, at the same
time, he noticed that these transverse canals were paired and opposite, and showed an
arrangement which might most assuredly be compared to an incipient stage of metamery
in the nephridial system.

This fact is most distinctly borne out by the Schizonemertea. The Paleeonemertea
(at any rate the Carinellidee) and Hoplonemertea show an arrangement which presents
different features, although, again, certain Hoplonemertea (Amphiporus lactifloreus)
answer very well to the Schizonemertean type.

A very remarkable form of nephridia is found in Carinina grata. The two fragments
of this species that form part of the Challenger collection both contain this important
structure in toto, so that I am able to figure both transverse and longitudinal sections.
These figures are brought together on Pl. IV., and will first have to be discussed. Two
portions may be distinguished in the nephridia of Carinina. in the first place, a glan-
dular canalicular portion in which numerous delicate tubes appear to be closely applied
together into a larger lobulate mass, which is situated right and left in the blood-space,
not being freely suspended in it, but applied on one side against the muscular layers
(figs. 5, 6), and on the other side, offering a free surface towards the cavity of this blood
space. PI. IV. fig. 4 gives a more enlarged view (Nsp) of a longitudinal section through
this portion of the nephridial apparatus, and, at the same time, enables one to judge of
its extension, the whole of this glandular spongy portion having been reached in
this section. It is, of course, also present in other sections, but does not stretch either
further forwards or backwards.

The furthest blind ends of the anterior ceeca of the digestive canal are found to pene-
trate between the lobes of this glandular mass (Je, fig. 4). These lobes are, moreover,
subdivided by bundles of muscle-fibres detached from the inner circular layer (fig. 5),
against which the whole apparatus is so closely applied (fig. 4, Cm). The cells composing
the glandular portion are filled with a granular protoplasm, and have very distinct large
nuclei. However much I have looked out in my different sections for a definite opening

by which the canalicular system here described might enter into communication with the
(ZOOL, CHALL, EXP,—PART LIV.—1887.) Hhh 15

114 THE VOYAGE OF H.M.S. CHALLENGER.

blood-space (archiccelome) surrounding it, I did not succeed in demonstrating one. Con-
sidering that I had found such openings in Carinoma, and that Oudemans had afterwards
demonstrated them in Carinella, I expected they would also be present in Carinina.
For the present, however, the result of a very attentive search is that they are absent ; at
least no opening is visible which can be said to prove a similar communication beyond all
doubt and by which it might be demonstrated once for all. Questionable points of
communication, which might eventually be interpreted as such, | have not allowed to
influence my testimony, so that, for the present, I must answer the question in the
negative. The case stands in a similar light with respect to the Schizonemertea and
Hoplonemertea, as will be seen hereafter.

If this communication with the blood-spaces is thus not demonstrated, that with the
cavity of the second part of the nephridial system is subject to a much less degree of
doubt ; and though I did not actually see the lumen at the point of communication, I did
see the communication itself as represented in fig. 4. It is then seen that this second
portion is distinguished from the one just mentioned by the presence of a spacious cavity.
This cavity, which may be called the nephridial canal, is first found ventrally to the
glandular spongy portion (figs. 4-6), but then gradually bends upwards as it passes
further backwards along the animal, until it becomes a narrow channel with a very
distinct and ciliated epithelium (figs. 1, 2), which passes at a very strongly inclined angle
(fig. 1) through the successive muscular layers, then makes a very sharp bend towards
the exterior surface, and traversing also the basement membrane and the integument,
opens on the exterior. This exterior opening has not been figured, but is found
in the sections following upon that which is represented in fig. 1. The two exterior
openings of the nephridial system lie on the dorsal surface of the animal, and at the
same time mark the point where the nephridial system reaches furthest backwards, the
glandular portion of it stretching forwards towards the head. That this nephridial canal
may, at all events in its proximal part, be more or less folded, is seen both in figs. 4 and
5, Ne, in the latter figure the lumen having an appearance as if it were doubled.

The nephridial system of our second Challenger genus of Paleeonemertea, Hupolia, is,
as was already known from Oudemans’ researches, more comparable to that of the Schizo-
nemertea than to that which has just been described in Carinina. It offers certain
peculiarities which deserve special mention, Here, too, we may distinguish, as we may
throughout the whole class of the Nemertea, longitudinal and principal nephridial ducts
situated in the blood-spaces or enclosed by the gelatinous tissue (Hoplonemertea), and
transverse or deferent ducts placed perpendicular to the foregoing, varying in number
and somewhat in size, and bringing about a communication between the ducts before
mentioned and the exterior.

Of the aspect and situation of these two portions in a transverse section, a comparison
of figs. 9 on Pl. VI. and 3 on Pl. VII. may convince us. Each of them represents

REPORT ON THE NEMERTEA. 115

about one-half of the thickness of the body-wall of the animal, and though somewhat
differently magnified, the position of the nerve-stem and of the layer em may easily
guide us how to combine them.

It is then seen that in Pl. VI. fig. 9 the longitudinal trunk, situated in the circum-
cesophageal blood-space, is not only cut through, but that even more than one nephridial
lumen (nep) appears in this section, showing that there is a doubling or at least a
branching of the principal nephridial duct in this region. Internal openings of this
system, funnels or anything comparable to them, were not detected by me in Eupolia
geardi or any other Hupolia; there were, however, very definite bends at right angles,
piercing first the inner longitudinal and then the cireular muscular layer, next the
nervous plexus, and then arriving in the outer layer of longitudinal muscles. In this
position the deferent branches of the nephridial system are seen in fig. 5, Pl. VIL,
which, moreover, reveals the important fact that sometimes more than one of them is
found at exactly the same level. I could not make out whether this duplication is in
any way related to that of the longitudinal tube ; I can hardly conceive it to be so, the
increase of the number of deferent vessels being also noticed in other cases, though hardly
as a regular phenomenon. In Hupolia giardii, too, I find it to be exceptional in this
sense, that most of the deferent ducts are single; one section of another species (Cere-
bratulus truncatus) contains the double duct on both sides, making the exceptional
phenomenon at the same time symmetrical. The number of deferent ducts observed in
the Challenger specimen of Hupolia giardii is seven on the right and five on the left
side, the latter being opposite to and symmetrically placed with five out of the seven on
the right. These numbers, however, only apply to that portion of the trunk behind the
head which was transversely cut, and belongs to the same series. I have not followed
up the nephridial apparatus to its posterior portion, but we may feel assured, on the
authority of Oudemans’ researches, that it will on the whole answer to the diagram
given on pl. i. fig. 11 of his treatise. One point deserving mention is that the first
trace of the nephridial apparatus of this Hupolia is visible in about the ninetieth section
behind the tip of the snout. When I add that the upper brain-lobes occupy sections
25 to 45, the forward extension of the nephridia can more easily be imagined. Nothing
special can be said of the deferent or of the principal ducts but that their epithelium is
distinctly one cell thick, nucleated, and unmistakably ciliated. Nor have I any special
discoveries to record with respect to the nephridial system of any of the Challenger
Schizonemertea, and may refer the reader for certain specific peculiarities, number and
disposition of deferent ducts, &c., to the description of the species where I have embodied
these details when they did not appear to have any general significance.

I should like, however, to refer a little more fully to the conspicuous development
at which the main, longitudinal canal of the nephridia has arrived in a certain species
of Cerebratulus (Cerebratulus macroren), where its walls are unusually massive (PI.

116 THE VOYAGE OF H.M.S. CHALLENGER.

XIII. figs. 7-9), although, when these walls are distended by the contents, their
thickness correspondingly diminishes (Pl. XIII. fig. 8). In this species, moreover, it
could be observed that towards the anterior end of this massive nephridial canal it
subdivides into smaller branches (Pl. XIII. fig. 9), applied against the wall of the blood
lacuna, and nearly escaping observation amongst the epithelial cells of these lacunee.
Here, again, no internal opening could be demonstrated ; whereas, at the posterior end,
the nephridial canal, making a sharp curve, passes outwards above the nerve-stems.
We thus observe differences in the nephridial system of the Schizonemertea, which may
be classified under the following heads :—

(a) The nephridial canal may be massive and single throughout the greater part of
its course, only ramifying anteriorly (Cerebratulus macroren, &c).

(b) It may be very copiously subdivided, every transverse section showing a consider-
able number of lumina, the whole thus forming a kind of network, with certain principal
longitudinal ducts, and being suspended against the wall of the circumcesophageal blood
lacuna (Hupolia).

(c) The meshes of this network may be situated in the region between the probo-
scidian sheath and the longitudinal nerve-stems (most Cerebratuli), or they may stretch
ventrally to these nerve-stems (Hupolia).

(d) The ducts leading to the exterior may be one on each side, and these generally
terminal (posteriorly).

(ec) There may be two on each side, and they may then communicate with the chief
longitudinal canal about its middle.

(f) They may be more numerous, often in various phases of distension, and arranged
more or less metamerically. The histological characters are fairly uniform, the lumen is
never excavated in a row of cells as is the case in so many Platyelminthes, in the
Discophora, &c., but is always bounded by a certain number of cells in every section.
Each of these cells has a large and distinct nucleus ; its protoplasm is granular, and the
free surface, which is turned towards the lumen, is ciliated.

We have now to examine the nephridia of the Challenger Hoplonemertea. In
Oudemans’ paper several points concerning them have been already noticed ; other details
referring to the situation and the number of the deferent ducts were mentioned above
when the species were described.

Hence it may here be sufficient to call attention to the fact, made specially palpable
by certain of the Challenger preparations, that whereas the nephridia of the Hoplone-
mertea are no longer suspended in blood lacune, but wholly surrounded by the gelatinous
tissue, they are at the same time much more intricately coiled and ramified, as
can be very easily seen from a comparison of fig. 1 (Nep), Pl. X., with figs. 7,9, Pl.
XHi. This involves, however, no important change in the histology; what we have
noticed under this head in the Schizonemertea holds good for the Hoplonemertea as well.

REPORT ON THE NEMERTEA. 117

Even less remains to be said when we consider the blood-spaces of the Challenger
Nemertea, be they the closed longitudinal and the metameric transverse vessels of the
Hoplonemertea and of the posterior body-region of the Schizonemertea, or the cireum-
cesophageal and circumrhynchodeal lacunze of the latter, or the two spacious lateral
longitudinal cavities of Carinina.

All these points have been dwelt upon at leneth by Oudemans (KXVII), and the
Challenger material furnishes a general confirmation of his results. Doubt cannot be any
longer entertained that these spaces are all clothed by an epithelium,—at any rate by a
special and continuous cellular coating, either applied against the muscular tissue when
this surrounds (Pl. IV. figs. 5,6; Pl. XIII. fig. 6; Pl. XIV. fig. 4), or traverses (PI.
VII. fig. 10) the cavities or against the gelatinous tissue, when it is in this that the
vessel takes its course (Pl. X. figs. 1, 8). In the latter case the structure of the vessel
is still more complicated, so that, as described by Oudemans, there is constantly a tubular,
denser layer of the homogeneous tissue just outside the inner epithelial coating; and
outside this tubular layer, which might be termed the basement layer of the vessel, we
find a second layer of generally more spherical cells, amongst which a layer of fibres, specially
belonging to the blood-vessel, may be seen to make its appearance (Pl. XV. fig. 1, dv).

This same description holds good for the longitudinal vessel, as far as it takes its
course ‘inside the proboscidian sheath (Pl. X. fig. 8). The gradual narrowing of the
circumeesophageal lacunar space into the two ventral vessels shows the passage of the
epithelium of the one into that of the other very clearly.

The difference in the distance along which the medio-dorsal vessel is enclosed in the
proboscidian sheath was mentioned and figured by Oudemans (xxvit) for different
species ; my own observations on the Challenger specimens fit into the same general
outlines ; a few additional data concerning these points are contained in the systematic

description of the species.

GENERATIVE ORGANS.

Certain not unimportant additions to our knowledge of the generative organs
of the Nemertea are due to the Challenger specimens. Among these facts I wish
successively to record :

(a) The irregular distribution in certain species of very numerous generative sacs
enclosed in the gelatinous tissue, and having each its separate external opening, which
are consequently neither paired nor metameric.

(6) The comparatively late period at which the definite external opening is formed,
although long before that time the sac is characterised by a pointed projection reaching
between the muscular tissue and foreshadowing the definite openings, dehiscence of
the body-wall being certainly not the normal way of exit of the generative products.

118 THE VOYAGE OF H.M.S. CHALLENGER.

As to the first point, it has been hitherto the current idea that in the Nemertea the
generative sacs, alternating with the intestinal ceeca, are paired and more or less meta-
meric. This is no doubt the case in the very large majority, and relieves us from
the duty of further describing the position of the generative sacs in Hupolia, the
Schizonemertea and most Hoplonemertea. In other Hoplonemertea, however, we find a
multiplicity of generative sacs in one transverse section (Pl. IX. fig. 4) which cannot
possibly be made to answer to the type just alluded to, and this regularity reaches
its extreme expression in Amphiporus moseleyr. The specimens of this species are
literally full of sacs, which [ was able to notice in their first stages, as well as in their
later development and ripest stages. In each transverse section (Pl. IX. fig. 4) a great
number of them may be seen; in horizontal sections (Pl. IX. fig. 7) the same irregular
multiplicity is met with. Externally I did not notice the openings, but it must be
remarked that only in very ripe specimens are these distinctly present.

Now this aberrant distribution is not wholly limited to Amphiporus moseleyi. There
are even reasons for considering it as an arrangement which has been retained in this species,
but which was common in the more primitive ancestral species of both the Hoplonemertea
and Schizonemertea. Atleast I find it in a similar condition in Carinella annulata, with
this difference, (1) that it is here only in the dorsal half, above the intestine, that the gene-
rative products are found ; and (2) that the external openings are generally very distinctly
visible as numerous irregular whitish dots on the dorsal surface of the animal, in the dark
coloured space between the dorsal median white line and two successive transverse ones.

Whether in Carinina similar conditions exist could not be verified, because the
preserved fragments contain no generative products. At any rate the fact is fully
established for one of the most primitive genera of Paleeonemertea, and this may justify
our insisting upon its having an archaic significance.

With the exception of Amphiporus moseleyi, Drepanophorus lankesteri is perhaps
the only Hoplonemertean in which still another trace of it is preserved, at least if we
may consider the fact that in this species (Pl. IX. fig. 1) two ventral generative sacs
are present on each side, as a reduced phase of the phenomenon, which we have found
represented in Amphiporus moseleyi, instead of looking upon it as a secondary dupli-
cation of primarily simple generative ceca. For myself, I should feel inclined to take
the first view as rather the more probable.

The other Hoplonemertea have not this peculiarity. The generative sacs are paired
and metameric, and if in ripe specimens two of them are cut in one section (PI. IX.
fig. 3) it is generally an indication that the section was not perpendicular. There is then
also found an adequate distance between the external pores.

This same figure clearly illustrates the fact that the generative products (in this in-
stance ova) may attain a considerable development and closely approach the ripe condition
before the generative sac itself communicates by a pore with the exterior, as indicated

REPORT ON THE NEMERTEA. UNG)

in the second of the two propositions above enumerated. At the same time we find the
spot where the pore will appear indicated by a pointed projection of the sac between the
muscles, and it is a fact very worthy of notice that the more we approach this preformed
outward duct, the less ripe are the ova (Pl. XV. fig. 14). The same fact is noticed in
many other Nemertea; Pelagonemertes even shows traces of it (Pl. VIII. fig, 8, ov.) In
Carinella I found it persisting even after the definite pore is established, and the most
plausible explanation appears to me to be this, that the deeper inwards the developing
generative products are situated, the more they are surrounded by the gelatinous tissue,
and the better their conditions of nutrition must be; whereas those which are observed
close to the duct, piercing the muscles, will only gradually increase in size, when in
their turn similar favourable conditions are offered to them.

The fact of the occurrence of definite preformed ducts without pores was observed
by me in Amphiporus moseleyi, Amphiporus marioni, Drepanophorus lankesteri, and
Drepanophorus serraticollis, and of several of these I also had ripe specimens, in which the
fact could be determined that it is, indeed, in the places where these pointed projections
are found that the pores afterwards appear (PI. IX. figs. 5, 6).

In this place I may mention that according to embryological observations (XIV) the
generative sacs are primitively in connection, at least im the species investigated, with the
epiblast by means of a strand of tissue which is not indicative of the ultimate duct.
These strands, however, are situated on the other side of the nerve-stem, and thus are in
no way identical with the projections which were here described and discussed as preced-
ing the definite generative pores.

The duct which pierces the muscles to afford a passage to the generative products is
generally shortened as maturity advances, through the distension of the body by the
ripening of ova or spermatozoa, and the consequent decrease in thickness of the mus-
cular body-wall. Still, in Cerebratulus macroren this duct presented an uncommon
feature, which must here be mentioned, and which is figured on Pl. XV. fig. 19. After
having pierced the circular muscular layer 8, it distends in the layer y to a second
sac-like expansion, which in its turn communicates with the exterior by a small opening.
This was not a local disturbance, but was met with in very numerous generative ducts,
both on the right and left sides of the animal.

In Eupolia and Schizonemertea the ripening sacs, developing in pairs between each
successive pair of intestinal ceeca, are often wedge-shaped, with the sharp edge turned
outwards, and the broad end between the two intestinal ceeca, where these emerge from
the principal longitudinal cavity of the intestine (see woodeut fig. 6, p. 120). And, in
addition to this, another fact is very marked in Hupolia giardu, viz., that dorsally
and ventrally the generative ceca become lobulated or arborescent, sending out short
lobes of indented and irregular shape.

It would, however, lead us too far, and hardly offer any additional interest, to discuss

120 THE VOYAGE OF H.M.8. CHALLENGER.

the changes in shape which the developing generative sac may undergo ; accordingly we
will now consider a few diverging peculiarities of the generative products themselves,
which I was able to observe in the Challenger Nemertea. That they are developed from
the epithelium of the generative sacs has long been known; this
is figured on Pl. XV. fig. 14, in a Hoplonemertean. It was
particularly evident and very distinctly visible in Cerebratulus
longifissus, where it was at the same time also demonstrable that
there is a very sudden decrease in ripeness of the generative
products close to the tail-end, where growth in length of the
animal is going on, and where new generative sacs are being
formed between the intestinal ceca. In this region all the most
different stages of ripeness of the ova may be studied side by side

in the same longitudinal section. The ova of Amphiporus mariont
Fra. 6.—Portion of a horizontal (P], XV, fig. 15) are characterised by the presence, in addition to the
section of a Cerebratulus, i.l. 5

the digestive tract, 7.c., its ar > penitor 1eh 7 1 Bab aa
re vat eeative: fact eee ta) Nucleus, of a round or reniform body, which is stained dark red by

glands; g, gelatinous tissue ; ni erocarmine, and but for this offers a certain analogy to the oil-drop
> g |

T & M., integument and mus-
culature,

in fish egos, being also more refractive than the nucleus, though
not quite so highly as the latter. This paranucleus was already observed in the youngest
eggs (Pl. XV. fig. 15, a); at that time its relative size, when compared to that of the whole
ege, was much more considerable. A second smaller specimen of Amphiporus marioni was
distinguished by the same peculiarity, which may thus in certain cases help to identify the
species, as I did not find the same feature in any other species of Hoplonemertea.

Of the eges of Pelagonemertes it has already been recorded that they are distinguished
by an investment of follicle cells (Pl. VIII. fig. 11); the development of this could also
be traced downwards to early stages, which were present in the same specimen (fig. 10)
side by side with the riper stages.

In the Schizonemertea two facts deserve mention, although their significance cannot
well be discussed as long as fresh specimens are not available. The one is the pre-
sence round the ripe eggs in Cerebratulus, sp. inc. (Pl. XV. fig. 18), and Drepanophorus
serraticollis (Pl. XV. fig. 17) of a hyaline, apparently mucous layer, which surrounds
each ege separately, and which is pressed into a polygonal shape when many ripe eggs
are enclosed together in the same sac. ‘The layer is comparatively thick.

The second fact was observed in Cerebratulus parker, where the peripheral proto-
plasm was much more darkly stained and more coarsely granular, all the eggs having
thus the aspect as figured on Pl. XV. fig. 16.

As to the spermatogenesis I have no new observations to record, spirit specimens
alone rarely presenting favourable material for such researches. These phenomena have,
moreover, been recently fully studied by Sabatier (XXVIIIq).

Hermaphrodite specimens were not encountered by me in the Challenger collection.

GENERAL CONSIDERATIONS.

In venturing at the close of this Report on the Nemertea, collected by H.MLS.
Challenger, to leave the region of demonstrated facts and actual observations, and to
enter upon that of speculation and suggestion, I gladly avail myself of the permission for so
doing granted to me by the editor, Mr. John Murray. I thought it necessary to ask for
‘that permission, because general speculations on the ancestry of the Chordata hardly
appeared to me to fit into the framework of these Reports. My desire in this case to
deviate from a rule which J held to be salutary, was due to the fact that of late these
speculations have been conducted along very varying channels, an entirely new one
having only very lately been opened by Bateson’s important series of papers on Bal-
anoglossus. An attempt to give more depth to one of these channels, and thus to lead
into it the attention of a greater number of my fellow-workers, especially commended
itself to me, since it was my conviction that the lines laid down by myself in former
publications derived considerable support from the Challenger material, and were thus
entitled to a renewed and full consideration.

I would formulate the proposition, to the further development of which this chapter is
to be devoted, as follows :—

More than any other class of invertebrate animals, the Nemertea have preserved
in their organisation traces of such features as must have been characteristic of those
animal forms, by which a transition has been gradually brought about from the archi-
celous Diploblastic (Calenterate) type to those enterocalous Triploblastica, that have
afterwards developed into the Chordata (Urochorda, Hemichorda, Cephalochorda, and
Vertebrata).

It will be seen that this statement excludes the idea of any direct ancestral relations
between Nemertea and Chordata. If any such relation were proposed, it might with
good reason be asked—considering the very extensive variation which is met with
amongst Nemertea—which species or which genus was more particularly pointed to. The
question in itself condemns the proposition which leads to it.

It will, moreover, be seen that this statement accepts the outcome of Bateson’s
researches and speculations, in so far as the points of agreement between Balanoglossus

and Amphioxus are fully recognised. A provisional link between these two, and an
(ZOOL. CHALL, EXP,—PART LiIv.—1887.) Hhbh 16

122 THE VOYAGE OF H.M.S. CHALLENGER.

arrangement of Balanoglossus amongst the Chordata, appears to be quite as justifiable as
the elevation of the Urochorda to their new dignity in zoological classification.

There is, however, a great difference between looking at Balanoglossus as a low type
“amongst the Chordata (in which I fully agree with Bateson) and rejecting the signifi-
cance of the Nemertean type as one of transition in the way above indicated.

There is no doubt that the Nemertea represent a more primitive phase than the
Enteropneusta (Hemichorda). They have no enterocele, and they have no gill-slits ;
but their nervous system shows certain unexpected analogies with that of the higher
Chordata of more intrinsic value than those that obtain between Balanoglossus and the
Chordata in general. Also for the important question, which is so vital in any considera-
tion of the ancestry of the Vertebrates, viz., the origin of metameric segmentation, it
appears to me that the Nemertea offer points very worthy of consideration, The question
of the proboscis and its sheath, as comparable to hypophysis and notochord, was fully
treated by me in another paper, and will here only be very briefly touched upon. In
my opinion, this comparison is all the more forced upon us, now that in other respects
(nervous system, &c.) new evidence of genetic relationship is here brought forward.

The first point I wish to consider is that of metameric segmentation. It has been
specially treated of late years by various authors of renown, with whom I do not wish to
enter at this moment into any lengthy controversy, but will briefly state what may be
gathered for the theory in general, from a careful consideration of the incipient metamery
of the Nemertea.

If we start from a more or less radiate ancestor of the earliest diploblastie type, in
which neither a radial nor a serial repetition of organs or organ systems has yet come
about, and which may indifferently be considered to resemble either a more flattened
Trichoplax or a more spherical gastrula, we may assume that in the course of the
development of other internal organs (towards the formation of which the secondary
accumulation of cells between the two primary layers often so largely contributes) the
radial symmetry may either be further accentuated or may be replaced by a tendency
towards bilateral symmetry. In the latter case we are inclined to ascribe the first impulse
towards this bilateral symmetry to a preference, which slowly establishes itself in the
animal mechanism, for moving in one direction rather than in any other, we., for
generally stretching forward, when moving about, one particular portion of the body.

One impulse of this sort will suffice to lead us to understand, or rather to deduce, a
very considerable number of consequences, which cannot fail to make their appearance
under the influence of natural selection acting upon the organisms that have inherited
this tendency in different degrees. Thus we may understand the narrowing and
lengthening of an animal that moves in one direction in preference to any other; and
sunilarly the development in the nervous system of a centralisation not far away from
the anterior extremity.

REPORT ON THE NEMERTEA. 123

All this has already been stated by Balfour in clearer terms in his Comparative
Embryology (vol. ii. pp. 308, 311), where he describes the gradual steps by which a
radiate medusa-like animal may have passed into a bilateral worm-like form, with two
longitudinal nerve-stems, which are regarded by Balfour as the stretched nerve-ring of
the Medusa.

I fully endorse these views ; only, with respect to the nervous system, I hold it to be
safer to leave out of comparison the already specialised nerve-ring of the Medusa, and
rather to go back to a Ceelenterate nervous system as primitive as that of the Actiua,
where the plexus, both of the epiblast and the hypoblast, with an increase in density im
the region of the mouth and the tentacles, may be said to be the fair representative of
one of the lowest starting points. In this the plexiform arrangement predominates.

Now we find in all the lower invertebrates various though distinct nerve tracts
that are being specialised in this plexiform nerve-tissue according to the modes of motion
of the animal, and according to the general shape of the body.

Thus in the Medusee, which move about in the water by annular contractions of the
lower portion of the bell-shaped body, one of the nerve-rings already alluded to was
demonstrated by the Hertwigs to innervate the musculature by which this is brought
about.

In the Ctenophora the nerve-system is less satisfactorily known, but still Lang does
not hesitate to bring them into genetic relationship with the Polyclada (KVIII). Among
the latter, Gunda, with its two longitudinal lateral stems, may be looked upon as
an extreme term in this series.

Another series may indeed be supposed to have derived longitudinal stems from a
ring which became extended to form lateral cords, as the animal passed from the radial
to the bilateral symmetry, in the way suggested by Balfour. Still, even in this case, a
nerve-plexus may be expected to be co-existent with or to have preceded the nerve-ring.
The longitudinal stems originating from the anterior thickenings of the plexus that
innervate the sense organs and the tip of the head (specially sensitive in connection
with the forwardly-directed movements of the body), would all the more probably be
preserved and increase in development, as during this forward movement they form a
right and a left centre for the reception of outward stimuli. In the same way those
of the radially-arranged stems of the Polyclada that are parallel to the longitudinal
body-axis, and mark out right and left, are more strongly developed than the others,
presumably on account of their importance in connection with the well-directed movements
of the body in response to external agents.

‘Tn the ancestral Mollusca, I think we may assume with great probability the presence
of four longitudinal stems—two latero-dorsal, and two latero-ventral ones ; in the ances-
tral forms of Annelids and Arthropods two, which have oradually coalesced ventrally, as
was first suggested by Gegenbaur. Again, in Nematodes differently situated longitudinal

124 THE VOYAGE OF H.M.S. CHALLENGER.

stems in what was originally a uniform plexus are preserved; whereas, in ancestral
Nemertea, two lateral longitudinal trunks in the plexus were undoubtedly characteristic
features.

That one medio-dorsal stem in this plexus, in which all the impressions made by out-
ward agencies on both halves of the body might be concentrated, and from whence the
corresponding movements might be regulated, will more fully answer the purpose than
two lateral stems, however they may be united by an intervening plexus, is @ priori
probable, and would explain the first impulse towards the formation of such a longitu-
dinal concentration in the uniform plexus.

And when once such a dorso-median stem is present, in addition to two lateral ones,
a strugele for supremacy, presided over by natural selection, may lead to a diminution
of the lateral stems, and to an increase of the dorso-median one.

This, in my opinion, as will be more fully developed below, was the case in the ances-
tors of the Chordata, traces of this struggle and of the competing structural elements
being duly preserved.

If we suppose the bilateral symmetry to be established in one of the lower re-
presentatives of the Metazoa, and the type to go on increasing in length in the course of
generations ; then this increase, indeed, exposes it to very different, and perhaps more
numerous dangers and enemies than would threaten it were the same bulk concentrated
in a spherical or radial circumference. And if, even in the latter case, injuries to the
specimen might prove fatal were it not provided with strong powers of regeneration
(cf: Star-fishes, Ophiurids, Crinoids, &c.), still it needs no comment that, when bilateral
symmetry and increase in length so considerably enlarges the surface which is open to
attacks, and so enormously facilitates the rupture of the specimen, or the severing of
parts by rapacious enemies preying upon it, similar regenerative powers are none the
less required to insure the persistence of the type.

These dangers, continually threatening the existence of the specimens, and thus in-
jurious to the species, counteracted as they are by regenerative processes (power of repro-
duction of lost parts), I hold to be at the base of all those cases of metamery in the animal
kingdom which do not fall under the head of strobilation, the latter being comparatively
rare with respect to the former. Incipient metamery, once established by this cause,
may further differentiate in the most diverse directions (heteronomous segmentation, &c.),
even after the absolute cessation of the causes that in the first instance have provoked it.

The explanation has, moreover, the advantage of being applicable to radial as well as
to serial metamery.

These propositions must now be more fully developed. The power of reproduction of
lost parts comes, without doubt, under the general laws of formation and growth. We
find it even in the lowest Protozoa. If the material which heredity has accumulated, either
in such a unicellular being or in the egg of a Metazoon, and out of which the elements of

REPORT ON THE NEMERTEA, 125

the different organ systems will gradually develop, is hereditarily so disposed that a
compensation for the loss of important parts is facilitated, this will, of course, constitute
an advantage. Such a compensation may, ¢.g., be obtained where the generative pro-
ducts are developed in very many separate centra, and not in one closed sac. Injury to
the latter will, ceteris paribus, be more fatal than an equivalent injury destroying one
or more of the former. The same holds good for diffused instead of concentrated
nervous centra, for the case of liver saccules to the intestine, instead of one compact liver,
for numerous apertures and deferent ducts to the nephridial system instead of one, &e,
And all this is still more evident when we have before us a long, bilaterally symmetri-
cal animal, which is easily snapped in two. In this case it must be of pre-eminent
importance, that the remaining halves, which may in their turn be severed by the same
cause into smaller parts, possess sufficient power of reproduction to repair the damage.
Now, it cannot be doubted that an equal distribution of the important components of
the organism (nervous centra, generative organs, nephridia, intestinal appendages, &c.)
throughout the whole length of the animal meets this requirement. Any severed portion
will then be provided with these more important parts, and will be more or less adapted
for a separate and individual existence.

The formation of a new mouth and of new brain-lobes in a fragment of this descrip-
tion remains, of course, quite as wonderful and inexplicable as before, but still we cannot
fail to see that such an arrangement as here indicated must somehow be beneficial to the -
species, and that we need not stop short with Bateson,’ when he says that “ the repetition
of various structures is one of the chief factors in the composition of animal forms. . .. .
The reason for their appearance is as yet unknown, and the laws that control and modify
them are utterly obscured.” Obscurity is not exchanged for broad daylight, but some-
thing is gained when we can see that a growth of the principal organ-systems in separate
and more or less independent batches, which in an elongated and bilaterally symmetrical
animal insensibly passes into the phenomenon of incipient metamery, may be of the
highest value for the persistence of the species.

Now this is actually the way in which we find the important organ-systems distributed
in the lower Nemertea. And out of this more irregular distribution a gradual metamery, in
some incipient, in others more complete, is seen to evolve within the boundaries of the class.
Even the nephridial system, in the primitive forms provided with only one opening to
the exterior, participates in this tendency towards metamery, and acquires a greater
number of apertures, serially arranged in pairs, thereby also tending towards a diminution
of damage when artificial division into two takes place in the nephridial region. The meta-
mery, the regular and serial repetition of parts, is thus seen to be of great importance in
aiding towards repair after damage to a lengthened bilateral form, in the same way as
the radial repetition of parts facilitates repair in the Echinodermata. In both cases the

} Bateson, The Ancestry of the Chordata, Quart. Journ. Micr. Sci., vol. xxvi. pp. 545, 546, 1886.

126 THE VOYAGE OF H.M.S. CHALLENGER.

destruction is only partial, the other homonodynamic portions temporarily ministering,
thanks to their more independent relation to the injured region.

When the faculty of repair of damage, occasioned by the severing of the animal into
two or more portions, has in the course of generations become more and more complete, it
can be readily understood that it becomes at the same time a defensive instead of being
only a curative process. An animal that at the approach of danger can separate in two or
more parts, each of them capable of reproducing an entire new animal, evades this danger
very effectively by doing so; whereas another that is attacked in the same way and does
not possess this faculty, is laid hold of, shaken about, and wholly or partly swallowed.
So in the Nemertea there is indeed a very strong faculty of spontaneous division
combined with the faculty of repair’; and anybody who has observed a fresh and living
Cerebratulus, with its extremely delicate sense of touch, commence to rupture into two,
in preference at the spot where it was grasped with the forceps, cannot fail to see in this
a defensive action.

This mode of self-defence may in quite another respect be useful to the species,
because at the same time it serves for propagation. Thus we see that the passage of
this defensive process to that of reproduction by fission is so gradual, that it would be
impossible to decide in every case what name should properly be applied to it. It cannot
well be denied that in all probability ours is only a special case, in which the power of
reproducing the species by a process of fission, reaching down as far as the unicellular
ancestors, has come to be regulated by other motor forces than growth and—if it may
not be called voluntary fission—still may be regarded as sudden and spontaneous fission,
brought about by external influences, of a threatening nature to the further existence of the
specimen. This regulation is no doubt a consequence of selection. Schizogony having
once been established, it must have been further beneficial to the species, on the grounds
that were developed above, that the internal organs should be present in multiple num-
bers, and this having once come about it is easy to understand, that a regular, rigorously
metamerous arrangement of this multiple material, still more fully answers the same
purpose, and is gradually evolved under the influence of selection.

Thus we may be said to be able to follow the appearance of metamery in a bilateral
animal, along all the gradual steps by which it is evolved, and many of these steps have
remained fixed and permanent in different Nemertean genera.

The last system that will participate in this metamery is the muscular system, and a
rash conclusion—such as is not rare in these days of ontogenetic fetichism—might lead
to the rejection of the views concerning metamery here developed, on the consideration
that it is exactly the metamery of the muscular system which appears first of all in the

' Both M‘Intosh and Barrois have observed and described very peculiar cases of repair in Nemertea, where the
head, brain, side-organs, &c., were reproduced on a headless trunk-piece. These experiments are well worthy of careful

repetition. It might be that only those fragments: in which a portion of the cesophagus was retained were capable of
repair of the head. 5

REPORT ON THE NEMERTEA. 1 7/

-_

ontogenetic development of Vertebrates. I will not circumstantially refute this argu-
ment, but will only remark that in Polygordius and other Cheetopods, which are
representatives of a group of animals in which segmentation reaches such a very high
degree of perfection, the longitudinal muscular layer of the body-wall is as yet continuous
in the adult, and not divided into metameric sections, as it is in certain Arthropods and
in Vertebrates. Now let us consider contractions of the inner muscular layer a of the
Nemertea, the only layer that is common to all of them, from Carinella to Cerebratulus
and from Cephalothrix to Pelagonemertes. This layer also corresponds with the longi-
tudinal muscular layer just alluded to of other lower worms, such as Polygordius, and,
as was noticed in our paragraph on the muscular system (cf p. 72), its contraction is
sometimes very distinct in favourable sections.

We then see the contraction marked out as so many successive blocks of contracted,
thickened fibres, separated by intervening parts of non-contracted fibrous tissue (Pl. XV.
figs. 9,10). The sections demonstrate that the phenomenon persists throughout the
whole breadth of the animal, z.e., that successive rings of contractile tissue alternate with
intervening rings in which no contraction is observed. This phenomenon is thus in a
certain degree comparable to an arrangement in distinct myomeres.

It is not unimportant that it was especially noticed in the fundamental muscular
layer, and it may at the same time be remarked that it appears, from what I have as yet
been able to observe myself, that the number of these rings in a given length of the
animal, is the same, or a multiple of the number of intestinal czeca and transverse
nerve-tracts in the plexus; in other words, that the incipient metamery of the internal
organs is in a definite relation to these phenomena—which might also deserve the name
of incipient metamery—in the muscular layers.

For the present the fact is, however, not yet definitely demonstrated that these
successive blocks are indeed present as such in the living animal. The possibility is still
open that they may be waves of contraction which have been fixed at the moment of the
immersion of the animal in the preserving fluid. For this reason I will not lay any
undue weight on this observation.

The ideas concerning the origin of metamery here expressed, and advocated for
several years in my university lectures, differ from those of Lang (XVIII) and
Sedgewick,’ in so far as they do not recognise the primary importance of the so-called
ccelomic sacs—the paired archenteric diverticula of Amphiowus—for the solution of this
question.

The question of the Vertebrate ccelome, so full of obscurities and difficulties, is
purposely left out of consideration here, where the relation to archiccelous ancestral
forms is discussed, and where an attempt is made to show that it is indeed probable that
the impulse towards the establishment of metamery is due to forces for which the

1 A. Sedgwick, On the Origin of Metameric Segmentation, Quart. Journ. Mier. Sci., vol. xxiv. p. 43, 1884.

128 THE VOYAGE OF H.M.S. CHALLENGER.

archenteron was not the only, nor perhaps the most important part of the organism to
act upon.

Still more different are they from those advocated by Perrier’ and Cattaneo,’ who
have adhered to and extended the idea already held by others, but by them most actively
defended, “that the metamery of Arthropods, Vertebrates, and a great many Vermes,
has originated out of the multiplication by transverse fission of very simple primitive
worms which were not metamerous. The products of this transverse fission remaining
connected together have then formed a chain of individuals, or a linear colony; later on
the unity of the chain has become more definitely established, the single individuals at
the same time becoming different both in form and in function, and the foremost
individual thus becoming the head of the series. Each segment (metamere) thus repre-
sents a reduced individual ; a metameric (segmented) animal is the result of the more or
less complete fusion of single individuals into an individual of higher order.”

Emery, from whose paper *I have translated the foregoing sentence, has very success-
fully combated these propositions. This author, however, adheres to Lang’s views in
ascribing to the archenterie pouches, the “ gemmation ” as Emery calls it (Joc. cit., p. 18) of
the intestine, the most important and initial significance for the first origin of metamery,
“the sexual glands and excretory canals being in relation to the intestinal diverticula,”
and following the lead. I have above explained why I cannot adhere to this argumen-
tation, which brings the ccelome and the sacculated intestine too strongly into the fore-
ground, and why I rather suppose incipient metamery to have been antecedent to either
of these (e.g., Carinella). On the other hand, many views contained in Emery’s im-
portant paper coincide with my own. Thus he writes (loc. cit., p. 11), speaking of that
interesting marine Triclade, Gunda segmentata :—

“The metamery of Gunda is thus manifestly the consequence not of the ‘symbiotic’
fusion of a colony of equivalent ‘ parts’ (meridi), but of the ‘autobiotic’ differentiation
and perfectioning of one ‘ part’ (meride);” and further on (p. 15) :—‘‘ When I consider
the facility with which certain worms break into one or more pieces even spontaneously,
it appears to me that this capacity for rupture may well have been the origin of the
reproductive purpose of transverse scission in similar elongated organisms. The rupture,
in the first instance accidental, could have contributed to the more rapid multiplication of
the organism, being followed by the regeneration of the parts that were deficient in the
separate fragments. This process of rupture might further have been so perfected that the
spot best adapted for rupture, with a view to the best condition of the fragments, was
prepared in advance. Inthe more perfect evolutional phases of the process, which are at
the same time those that have till now been more carefully investigated, the new head is
formed anteriorly to the rupture, or at least its essential parts are pre-established.”

1K. Perrier, Les colonies animales, Paris, 1881.
2 G. Cattaneo, Le colonie lineari e la morfologia dei Molluschi, Milano, 1883.
3 C, Emery, Colonie lineare e metameria, Napoli, 1883.

REPORT ON THE NEMERTEA. 129

My own views emphasise the presence of a peculiar process of development of the
internal organs, running parallel to this predisposition for rupture in a particular spot
—the spot which will correspond to the outwardly visible demarcation between the future
segments. They thus go one step further—and, in my opinion, a very essential step—
in the attempt to explain the origin of metamery in the lower Platyelminthes, these
bilateral descendants of radiate Coelenterata, and at the same time predecessors of both
Chordata and Appendiculata.'

This view of the origin of metamery also affords an explanation for the very different
degrees in which we find metamery or segmentation expressed in the different divisions
of the animal kingdom. The incipient metamery which we have traced (and which we
have pictured to ourselves as arising through natural selection amongst those forms,
which, while developing in length, find metamery to be a protective peculiarity) imme-
diately creates, by the fact of its existence, new and variable material for selection,
again to be acted upon. And whilst metamery develops in one direction in one line of
descendants, the other line brings to the foreground a different set of advantageous
combinations, each of them again the stock of new and varied forms. In other words,
metamery once established in its most primitive form, and intimately connected with
spontaneous fission under the influence of external agents, has been of very great
moment in the bringing about of new and endless variations of animal life. And it is
rational, when we have before us, say one of the lowest Vertebrata, in which nobody
will deny the presence of distinct metameric segmentation, to conclude that this metamery
must necessarily be in many respects redueed, and that in the ancestral forms it must
have been far more complete, must have stretched forwards along the whole of the head,
must have been more forcibly expressed than it is now—in all the cephalic nerves, in
the nephridia, the gill-slits, &c.;—all this on the presumption of the existence of an
ancestor so completely and exemplarily segmental as to throw no light on the origin of
segmentation and metamery, unless by the aid of Perrier’s and Cattaneo’s exaggerations.
Such conclusions must, however, necessarily be made by those who follow Dohrn’s and
Semper’s lead concerning the phylogeny of the Chordata.

Bateson, in taking Balanoglossus as his starting-point, finds the acknowledged points
of resemblance in the metamerous gill-slits, &c., and adds to them important data con-
cerning the metamerous ccelomic diverticula. Still, for a general view on the origin of
metamery, Balanoglossus offers no points that we do not find more strongly represented
and more forcibly expressed in the Nemertea. It certainly deserves mention that long

1 Gegenbaur, in his Grundriss der Vergleichenden Anatomie (1878), hints at similar explanations to those advocated by
Emery and myself, when he says (p. 64) :—‘ Die Metamerie . . . . lisst Zustiinde des Beginnes und der nicht aus-
- gefiihrten Beendigung mannichfach erkennen . ... In dem Maasse als ein Metamer die Abhingigkeit vom Gesammt-
organismus durch die Ausbildung seiner eigenen Organe aufgiebt emancipirt er sich vom Ganzen und gewinnt die
Befithigung freier Existenz,” Further on he speaks of incipient metamery as “eine stellenweise, fiir den Organismus
praktisch werdende Ausbildung” of the different organ systems.

(ZOOL, CHALL, EXP.—PART LIV.—1887.) Hhh 17

150 THE VOYAGE OF H.M.S. CHALLENGER.

before Bateson drew renewed attention to the numerous points of agreement between
Balanoglossus and the Chordata, M‘Intosh had done the same for Balanoglossus and the
Nemertea, a separate paragraph of his monograph (XIX) being devoted to the discussion
of these homologies.

Sedgewick (loc. cit.) holds the unsegmented worms to be wholly “neghgeable
quantities,” at any rate superfluous links in the chain that connects the Chordata with
the antecedent Diploblastic stages. In my idea both these authors, valuable as certain
of their suggestions are, have not been thoroughly aware of the necessity that, in all
discussions on the origin of metameric segmentation, we must attempt to grasp at data
that give a clue to the possible action of natural selection in the gradual evolution of
metamery. ‘This clue appears to me to be far more distinctly contained in the views here
advocated than in the other hypotheses.

It may further be remarked, now that we have once more alluded to Bateson’s
phylogeny of the Chordata, that even this naturalist does not feel justified in wholly
rejecting the Nemertea from the Vertebrate pedigree. Whilst in the text of his
article (loc. cit., p. 566) he does seem to prefer this negative alternative ; still,
in the subjoined diagram of the general relationships of Urochorda, Hemichorda,
Cephalochorda, and Vertebrata, the Nemertea are introduced

with a point of
as a side branch lower down on the common parent stock.

interrogation, however
Now, this being concordant with my own views of the Chordate phylogeny,—
the point of interrogation excepted,—it is necessary to inquire why there is this
discrepancy between Bateson’s speculations in the body of his treatise and the
hypothetical pedigree at the end of it. It appears to me that this is due to his
hesitation (Joc. cit., p. 555) in accepting the views hitherto entertained and advocated
by myself as to the phylogenetic connection between the Nemertean and the Vertebrate
nervous system. For this hesitation Bateson has good reasons, and while I appreciate
the soundness of them, I hope in the remainder of this chapter to remove the reluctance
of him and others to accept the phylogenetic significance of the Nemertea, thanks to
new light that may be thrown on the evolution of the central nervous system of
the Chordata by the observations above recorded on the nervous system of the Challenger
Nemertea.

It is to these speculations on the nervous system that we now have to turn our
attention.

As will be seen from the terminology introduced in the paragraph on the nervous
system (p. 76), and as it is now time more fully to develop, I am inclined to attach
considerable morphological importance to the arrangement of the different constituent
parts of the nervous system in the Nemertea. In former publications (X, XIc) I have
repeatedly insisted on the significance of certain points in the anatomy of the Nemertea,
when considering the general question of the relationship of the Chordata to their

REPORT ON THE NEMERTEA. 131

unknown invertebrate ancestors, and I have insisted not only on the possibility of the
homology between the Nemertean proboscis and the hypophysis cerebri of the Verte-
brates, but I have, even earlier still, attempted to show that the nerve-system of these
two groups might be considered in a common light, as was first indicated by Harting
in his Leerboek van de Grondbeginselen der Dierkunde of the year 1874. Further
reference to the hypothesis here alluded to is found in Balfour's Monograph on the
Elasmobranch Fishes (pp. 170-172), in my own publications (IX, X), and in Balfour's
Comparative Embryology* (vol. ii. p. 258). I will not here enter upon this hypothesis
more fully, but will briefly state that it attempted to consider the central nervous system
of the Vertebrates as a possible median coalescence of two nerve-trunks, that were lateral
in the primitive ancestors of the Vertebrates, in the same way as the coalesced ventral
nerve-cord (Bauchmark) of Annelids and Arthropods may be considered with Gegenbaur
as having arisen out of a double lateral trunk, which in certain, still more highly differen-
tiated forms have fused ventro-medially.

A strong argument against the first-mentioned hypothesis is the fact that the spinal
cord ontogenetically always makes its appearance as a median unpaired plate or thicken-
ing, a very faint trace of a possible double origin of this plate being hitherto only
observable in one species of Amphibia, Triton teniatus ; whereas in all other vertebrates,
Amphioxus and the Cyclostomata not excepted, the unpaired origin is most evident.
The bilateral symmetry or the full-erown brain and spinal cord is a much later feature,
and can hardly be regarded as the expression of a primary coalescence of two separate
halves to form a median whole.

Tam the more inclined to abandon this hypothesis, because I will attempt to show
that we can establish phylogenetic comparisons between the Chordate and the Nemertean
nervous system on a much more simple basis ; comparisons which at the same time cover
a far more extensive ground than did those of Harting, Balfour, and myself, which I
have just alluded to.

Since in the nervous plexus of all the Nemertea a median longitudinal tract, some-
times of comparatively large size, has now been detected, since even in the Hoplo-
nemertea, where’ the plexus has disappeared, the same medio-dorsal nerve-tract has in
most cases been preserved, and, finally, since from this dorso-median stem metameric and
paired nerve-tracks may be seen to emerge in Paleeonemertea and Schizonemertea, we
must inquire in how far the direct comparison of this medio-dorsal nerve-stem with a
primitive spinal cord may be said to hold good.

In order to do this we must first consider the relation of this stem, to which we have
given the name of medullary nerve or medulla, to the rest of the nervous system, more

1 It may here be remarked that Balfour has omitted to mention that Harting was the first to bring forward this
hypothesis: it is well to be reminded of this when Beard, Bateson, and others similarly ignore this claim to priority of
my venerated predecessor.

132 THE VOYAGE OF H.M.S. CHALLENGER.

especially the brain-lobes.’| In a former publication (IX), where the medullary nerve
was for the first time noticed and described as the proboscidian-sheath-nerve, I traced its
origin to the dorsal commissure between the two lateral halves of the brain (loc. cit.,
pl. i. fig. 1). Thanks to certain very favourable specimens in the Challenger collection,
I have now been able to add new data to this statement. Sections through the brain of
Cerebratulus macroren, Cerebratulus corrugatus and Cerebratulus angusticeps (Pl. XI.
figs. 1, 7, 8; Pl. XIII. fig. 1) show that the condition of things is indeed less simple than
this original statement would imply,—that the medullary nerve is not an eminently fibrous
cord springing at right angles from the eminently fibrous upper brain-commissure, but
that the nerve-tissue constituting the foremost and uppermost portions of the upper
brain-lobes spreads out over a far more considerable surface than the fibrous tract which
is known as the dorsal commissure. This expansion of nerve-tissue, in which the cellular
elements are no less conspicuous than the fibrous, is posteriorly directly continuous
with the plexus above described, laterally with the brain-lobes, anteriorly with the
cephalic nerves springing from these lobes. It attains its fullest development just
before and behind the region where a transverse bundle of fibres uniting the fibrous core
of the lateral brain-lobes forms the well-known dorsal brain-commissure. This commis-
sure is a transverse fibrous tract forming part of a more extensive nerve-plate. To this
expansion of nerve-tissue the presence of nerve-cells gives a more primitive, at any rate
a less specialised, character. These nerve-cells and nerve-fibres are directly continuous
with those of the medullary nerve and (backwards) with those of the nerve-plexus, of
which this nerve is only the median longitudinal thickening. There is even more reason
to look upon the fibres of this medullary nerve as a tract of the general fibrous stroma
not necessarily connected with the fibres of the braim-commissure. In other cases a more
direct continuity between the commissural and the medullary nerve-fibres was however
observed.

In order clearly to understand the relative importance of the different parts of the
nervous system here noticed, the primitive Paleonemertea offer the best starting-point.

Thus in Carinella we find the brain-lobes not yet separated into distinct upper and
lower lobes, nor do we find a posterior lobe (side-organ). The brain is a double lateral
and anterior thickening in the nerve-plexus, situated like it and like the lateral nerve-
stems outside the muscular body-wall in the deeper strata of the integument. The only
difference between the medio-dorsal medullary nerve in this species and the lateral nerves
with their anterior enlargements (the brain-lobes) is its position and its greater tenuity
(Pl. XVI. fig. 1), which, however, does not prevent its being very clearly observable in every
transverse section (Pl. XI. figs. 3, 4). Its connection with the brain-commissure was
already described (IX, p. 25), and figured by me (loc. cit., pl. iii. fig. 31). It must,

' In the course of these considerations a certain amount of repetition of facts already noticed.in the paragraph on
the nervous system cannot well be avoided.

REPORT ON THE NEMERTEA. 133

however, be remarked that in these most primitive Palzeonemertea, the anterior dorsat
brain-commissure is less significant than in the Schizonemertea, and hardly anything else
than the foremost of those numerous transverse metameric tracts in the plexus (dvr,
Pl. XVI fig. 1) which connect the lateral stems with the medullary nerve (dorsally) and
with each other (veutrally).

These important metameric nerve-pairs are most distinctly observed in Carinella.
Here, as in the Schizonemertea, the medullary nerve is also continued forwards in front
of the brain thickenings. This continuation sometimes shows a short bend just on
the level of the commissure, so that both the medullary nerve and its anterior
continuation may be seen in one section. This explains at the same time the arrange-
ment traced on Pl. XII. fig. 8. Posteriorly the medullary nerve can be followed down to
the hindmost extremity of the body. In Hupolia and the Schizonemertea the arrange-
meut remains the same, the metamery of the transverse stems is perhaps more clearly
expressed, the whole plexus and the longitudinal stems are no longer in the integument,
but between the muscular layers. Still the whole of the nervous system also answers to
the general type as represented in the diagrammatic fig. 1 on Pl. XVI.

We have now seen enough of it to understand that a comparison with the central
apparatus of the Vertebrate nervous system cannot indeed be called a strained comparison.
On the contrary, the comparison is much less artificial than was the one which Balfour
was inclined to adopt, and which, as noted above, rendered necessary the acceptance of
the phylogenetic development of the Vertebrate medulla out of a double cord.

And so I do not hesitate to proclaim the medullary nerve of the Nemertea to be a
very important link in the phylogenetic chain, of which the Vertebrate spinal cord is the
outcome. Like the Nemertean medulla, the Vertebrate spinal cord is median, unpaired,
and composed of nerve-cells and nerve-fibres ; like the Nemertean medulla, it is a thicken-
ing in a nervous plexus, originally wholly epiblastic, of which, among Vertebrates, the
Amphibian embryos offer such a striking example. This instructive and suggestive case
was known to Remak and Stricker (as the “ Nervenschicht” of the frog embryo), it was
more carefully studied and elaborately described by Goette (his “ Grundschicht” of the
epiblast, in his Entwickelungsgeschichte der Unke), and it has been again recently
brought into the foreground by Baldwin Spencer, in his latest paper on the subject."
The latter author compares the Amphibian plexus with that of Palazeonemertea and Schizo-
nemertea (Joc. cit., p. 134), as had already been done before him by my friend Professor
Ray Lankester, with whose suggestion I at that time (1880) did not yet venture fully
to associate myself.

The numerous data that have since been accumulated for a direct comparison of
Nemertea with lower Vertebrates appear, however, now to fully justify that comparison

1 Baldwin Spencer, Some notes on the early Development of Rana temporaria, Quart. Journ. Mier. Sci., vol. xxv.
Suppl., p. 123, 1885.

134 THE VOYAGE OF H.M.S. CHALLENGER.

which was first expressed in a footnote to a former paper of mine (X, p. 438). There
can hardly be any doubt as to the existence, consequent upon natural selection, of a
constant tendency in the different component parts of living organisms towards simplifi-
cation and increased efficiency (Roux’s Kampf der Theile im Organismus). This fact
enables us to understand the gradual supremacy of the median cord in the Nemertean
plexus over the two lateral ones. It seems as if it were mathematically demonstrable that
for the delicate adjustment of the impressions from the exterior to the co-ordinated
movements thereby occasioned, one longitudinal central stem in bilateral, lengthened
animals, would be more efficacious than two lateral ones. And if we ask if, at the final
stage of this struggle for supremacy between three longitudinal stems, any remnants of
the lateral cords are yet detectable in the Vertebrate embryos, perhaps even in the adults,
T am inclined to answer in the affirmative. Here I must be allowed to insert a reference
to the three figures on Pl. XVI., which will facilitate the exposition of the further conse-
quences of the hypothesis I am here developing. Fig. 1 represents the chief points in the
nervous system of the Nemertea. The brain-lobes are simple lateral swellings of the
longitudinal stems, as in Carinella; plexus, medulla and transverse stems, together with
brain-lobes and lateral stems, may be considered as forming part of the integument (cf:
Carmina). A double innervation of the respiratory portion of the intestine is indicated ;
one due to visceral branches (vi.sy) springing from the plexus (or from its transverse
tracts), the other to the more specialised nerve (v), which has above been indicated as
the Nemertean vagus nerve. The plexus and its innumerable radial fibres, both sensory
and motor, are not indicated in this figure, nor are the nerve-stems which, when present
(Pl. XIV. fig. 2), pass from the lateral stems directly to the integument.

This figure must now be compared with the two others. Of these, Pl. XVI. fig. 2,
diagrammatically represents the chief points that may be considered as characteristic
of the nervous system of a lower Vertebrate, in which the dorsal and ventral roots of the
spinal nerves (dv and vr) are as yet separate nerve-tracts, in which the sympathetic nerve
system is as yet only represented by visceral branches given off by these dorsal roots
(vi.sy), and in which the polymerous character of a primitive vagus (Vag) is established.

PL XVI. fig. 38, stands for Amphiowus, as far as we know its nervous system, more
particularly through the researches of Rohon and others. It differs from the foregoing by
the absence of a distinct brain swelling, and of a polymerous vagus. A number of spinal
nerves are considered as homologues to the vagus of Vertebrates by Rohon. The
commissural connections between the successive spinal nerves form a plexus, which is
peripherally even much more elaborate, according to Rohon’s figures. This plexus does
not reveal the presence of any distinct lateral longitudinal nerve, nor any ganglia of
spinal or cephalic nerves. The latter (en) may be said to be three in number. Visceral
branches (v7.sy) are given off by the dorsal nerves (dr). The ventral ones, springing from
the lower edge of the medulla, are here represented as shorter stems (v7).

REPORT ON THE NEMERTEA. 135

The opposite half of the system, seen in transparent perspective, as given in the two
other figures, is purposely omitted here, because of the asymmetry of Amphioxus in
this respect.

Now a glance at these figures will convince us that the situation of the Nemertean
medullary nerve in its plexus, and with its set of transverse nerves, is directly compar-
able to the Vertebrate medulla and spinal nerves. The nerve-plexus filling up the
intervening spaces in Nemertea is present as a transitory structure in Amphibian
embryos.

The ulterior appearance of an anterior enlargement forming the Vertebrate brain ;
the higher complication attained by the brain and spinal cord when its mass increases,
but not its dorsal expansion, by the appearance of medullary ridges ; and the formation of
a neural canal by infolding of the neural plate, all these are important developmental
facts which do not in any way weaken the grounds for comparison of the two structures.
They may be looked upon as adaptations to the much more considerable efficiency
and concentration that is gradually attained by the central nervous system as we ascend
higher in the scale of the animal kingdom.

The fact that the neural ridge in so many Vertebrata precedes the appearance of the
spinal nerves, and is inserted along the top of the folds that bend together to form
the neural tube, may be thus interpreted, that during the phylogenetic process
of infolding, the transverse nerve-tracts (dorsal spinal roots) remain attached in the
same way to the medio-dorsal collecting trunk as they did in the ancestral forms, and
are dragged upwards by the infolding process. The ventral roots must be phylo-
genetically linked to the plexus as well; inasmuch as the musculature originally lies
inwards of the nervous plexus, their deeper situation is not surprising.

In the points hitherto enumerated there is entire coincidence between Amphioxus
and the other Vertebrata, as far as their comparability with the Nemertean diagram
goes. Another point of coincidence is the way in which the foremost portion of the
intestinal canal and adjacent blood-vessels are innervated by visceral nerve-stems,
indicated in all the three diagrams by vi.sy.

The claims to validity of the comparison here made between the spinal nerves of
the Chordata and the transverse stems of the Nemertea, should be again insisted on,
now that the researches of Rohon,! Freud,? Schneider, Ransom, and d’Arcy Thompson ’

1V. Rohon, Untersuchungen iiber Amphioxus lanceolatus, Denkschr. d. k. Akad. d. Wiss. Wien, Bd. xlv.

28, Freud, Ueber Spinalganglién und Riickenmark des Petromyzon (Sitzungsb. math.-nat. cl. k. Akad. Wiss. Wien,
Bad. lxxviii., Abth. 3, 1878). This author says (p.154): “Ich kann wenigstensvon den letzten Wurzeln des Caudalmarks
sagen dass ihre Selbstindigkeit so gross ist, dass man von vorderen und hinteren Spinalnerven, anstatt von vorderen
und hinteren Wurzeln reden konnte”; and Wiedersheim in the 2d edition of his Lehrbuch der Vergleichenden
Anatomie (p. 321): “Vieles spricht dafiir dass die Vorfahren der heutigen Wirbelthiere getrennte dorsale und
ventrale Nervenwurzeln besessen haben miissen.”

3 W. R. Ransom and @’Arcy W. Thompson, On the spinal and visceral nerves of Cyclostomata, Zool. Anceiger, No, 227,
July 1886.

136 VOYAGE OF H.M.S. CHALLENGER.

have established for the lower Chordata (Cephalochorda and Cyclostomata) that the
typical chordate spinal nerve is not originally provided with a double root, but that this
double root appears to have arisen by the coalescence of what were primitively m the
eroups just mentioned, separate and alternating dorsal and ventral nerve-tracts.
With these so much simpler spinal nerves the transverse nerve-stems of the Nemertea
undoubtedly offer points of comparison. These Nemertean nerves specially differ from
the Vertebrate spinal nerves in two respects: (1) they give off nerve-fibres in different
directions, which are probably motor as well as sensory and visceral, according to the
different organ systems they terminate in; and (2) they go round ventrally, each of them
forming a loop all round the body. As to the first point of difference just alluded to, it is
the expression of a low and primitive degree of differentiation, and when a step forwards
is made, differentiation of labour will tend to develop certain tracts more particularly con-
taining sensory and visceral nerve-fibres, which are more especially directed towards
the epithelia (the primitive dorsal or posterior roots), and others more particularly
containing motor nerve-fibres, and more especially directed inwards towards the muscles
(the primitive ventral or anterior roots), because the musculature, as was already
mentioned, is originally situated internally to the nervous system.

For the present we can only hold it to be established that the fibres of these three
categories are blended in the Nemertean plexus, without bemg able to determine in
how far the specialisation therem observed, of the appearance of transverse metameric
nerves, may at the same time be accompanied by a commencement of differentiation, such
as has just been alluded to. We may, in other words, not yet assume that among these
metameric stems there is already a tendency to an alternation between such as have
sensory and visceral, and such as have motor predispositions.

Ouly in a few cases may we be justified in saying that certain nerve-tracts belonging
to the Nemertean peripheral system are more especially sensory (Pl. XIV. fig. 2) or
visceral (Pl. XIV. fig. 4), and these no doubt offer important analogies in their situation
and connections to similar nerve-tracts of the Vertebrata.

The second point of difference, viz., the continuity in the ventral median line of the
transverse tracts of the Nemertea, is no doubt a consequence (a) of their origin in a
perfectly continuous plexus, (b) of the cylindrical arrangement of the muscular layers,
which in most cases are uninterrupted both in the dorsal and in the ventral median line.
It is all the more important to notice, that more especially in the primitive Carinellide,
the tendency is very marked towards a scission of this muscular body-wall into a right
and a left half (cf p. 72). A comparison of figs. 4, 5 on Pl. XI. will show this.
In the Schizonemertea, too, and in Hupolia it affects the primitive muscular layer (PI.
XI. figs. 10, 12), in a more or less marked degree,

This longitudinal scission is no doubt the first expression of the phenomenon which
shows us the musculature of the right and left half of the body, developing quite inde-

REPORT ON THE NEMERTEA. 137

pendently in the Chordata. It is easily intelligible how, as this phenomenon gradually
becomes more and more marked, no more ventral connecting fibres across the non-
muscular region were required for the innervation of the musculature of the right and
left half of the body.

The process by which the transverse nerve-tract, with radial nerve-fibres leaving it at
short intervals, both centripetally and centrifugally gradually assumed the form of a
nerve-stem with a dorsal and a ventral branch, such as we find in the spinal nerves, must
have gone on pari passu with those numerous other changes, which we cannot as yet
fully trace, but which must have occurred when (1) the muscular metamery became
gradually established, (2) the dorso-median medullary tract became so preponderant
that an increase in mass, with economy of bulk, was only to be obtained by a process of
folding-in already discussed above, and (3) the attachment of the spinal nerves
(transverse tracts) to the medulla was modified in consequence of this process.

None of these phenomena, however, offer anything that is in any way inconsistent
with, or opposed to, the general theory here developed.

We have now sufficiently insisted on the chief point of comparison here proposed,
viz., that between the Nemertean medullary nerve and its metameric transverse nerve-
cords, and the Vertebrate cerebro-spinal axis and spinal nerves.

If Amphioxus were the only Vertebrate known, we should, recognising the phylo-
genetic importance of the plexiform arrangement still met with in the adult of that
species, admit that, as far as we know at present, the primary lateral nerves with their
anterior swellings of the Vermian ancestors had disappeared in the same measure as the
dorso-median spinal cord had come more and more into the foreground.

But our consideration of other Vertebrates leads us to the conclusion that, when
once the general homology between the two nervous systems is admitted, there may
perhaps be secondary points in regard to which the comparison can be further extended.
And it must be recognised, that if we should also succeed in rendering more or less
probable a comparison in secondary details, this might again be favourably interpreted
for the primary and more important part of the hypothesis.

The search after these secondary points of agreement was instituted by me, when the
question above alluded to presented itself, viz., if any remnant could be traced of the
central nervous system of Nemertea-like ancestors, ¢.¢., of the brain-lobes and lateral
stems, in those Vertebrate descendants in which the medio-dorsal tract had become so
preponderant as to give rise to the unpaired medulla and brain.

It is clear that if it shall be possible to trace any such remnants, and to render their
homology with the Nemertean central nervous system probable, they will have to be
sought for—(a) in the head, as lateral more or less independent nerve-centra, innervating
sense-organs of the integument, and passing posteriorly into parallel longitudinal stems ;
or (b) in the trunk, as longitudinal nerve-stems, in which the central character should

(ZOOL. CHALL. EXP.—PART LIv.—1887.) Hhh 18

138 THE VOYAGE OF H.M.S. CHALLENGER.

be somewhat less marked than in the anterior swelling, but in which the original
significance as parts of the central system should still be indicated either by histological
or by embryological features.

To these latter conditions nothing can answer in the Vertebrate nervous system
excepting the so-called ramus lateralis vagi. It is present in all Vertebrates above
Amphioxus, long and important in the aquatic Ichthyopsida, gradually disappearing
when the aquatic medium is exchanged for an air-breathing existence, and finally only
retained in the higher Vertebrates as the inconspicuous ramus auricularis vagi.

Its course is indeed strictly lateral, and has always been a puzzle to anatomists.
Stannius’ characterises the existence and the course of this sensory nerve along the
trunk down to the tail as “ one of the most interesting facts of anatomy.”

None the less startling is its development. Whilst Balfour attempted in this respect
to bring it on one line with the other parts of the peripheral nervous system, the
corresponding results of Semper, Goette, van Wijhe, and Hoffmann are all in the
contrary direction. They have seen the nervus lateralis appear as an independent
product of the epiblast, arising 7m loco along its whole length, its formation often even
preceding that of the spinal nerves. These results have again been fully confirmed and
definitely established by the latest investigator of the problem, Beard,’ who also gives a
detailed description and figures of the connection between the nervus lateralis and the
vagus ganglion, both of them so much more massive and conspicuous in early embryonic
stages than later on.

And now that we are attempting to find out whether there is a possibility of com-
paring the lateral nerve-stems of lower worms with the nervus lateralis of Vertebrata,
we are naturally led to consider, in the second place, the question whether the anterior
swellings of these lateral stems (the paired brain-lobes of the worm) may have their
morphological equivalents, their remnants, in the set of anterior nervous swellings that
are found in the head on a level with the nervus lateralis, and longitudinally connected
with it; viz., the variable set of ganglia of the cephalic nerves.

As to the origin of these ganglia of the cranial nerves I have no observations of my
own, and must rely on the data of other observers.

It is suggestive to give the opinion of the three latest investigators of the develop-
ment of these organs in different groups of Vertebrates in their own words.

Professor A. Froriep,’? who studied Mammalian embryos, writes (loc. cit., p. 35) :—
“The ganglia (of facialis, glossopharyngeus, and vagus) enter into a peculiar, very inti-
mate connection with the epiderm”; further (p. 40), “these ganglionic connections with
the epiderm must probably be regarded as rudiments of organs which have phylogenetically

1 Das peripherische Nervensystem der Fische, p. 108.

2 The System of Branchial Sense-Organs, &c., in Ichthyopsida, Quart. Journ. Mier. Sci.. November 1885, p. 95.
3 Ueber Anlagen von Sinnesorganen am Facialis, &c., Archiv f. Anat. u. Phys., 1885, Anat. Abth.

REPORT ON THE NEMERTEA. 139

disappeared, and which are only now retained in the ontogenetic development”; then
(p. 43) “for the Gasserian ganglion there is no indication of a connection with the
epiderm”; and, lastly (p. 52), “it appears to be hardly any longer possible to look
upon these nerve-ganglia (Nervenknoten) as simply homologous with spinal ganglia.”

Baldwin Spencer’ writes (Joc. cit., p. 129) concerning Rana temporaria :—< Along
certain lines the cells of the nervous layer proliferate, and it is by this proliferation that
the rudiments of the cranial nerves are laid down” ; further (p. 130), “ the development
of the ganglia at the level of the lateral line, and the fact of their long connection with
the epiblast at this pomt . . . . is of great interest in connection with certain
points in the development of the Elasmobranch nerves.”

Concerning the developmental phenomena in the trunk-region at this period, the spinal
nerves are stated to be not yet visible, “though the nervous sheath is clearly developed
and in this the lateral line”

The author next mentions observations made by him on Dr. Beard’s sections of
Elasmobranch embryos, and goes on to say (loc. cit., p. 1381) :—

“The Gasserian ganglion is, at all events in part, formed directly from the epiblast

the same development takes place in the case of the ganglion of the third and
seventh nerve—in that of the ciliary ganglion the development is particularly clear—
The ganglia arise along a level of the lateral line continued on the head.”

He next says:—‘‘The curious origin of the ganglia of the cranial nerves points
strongly to the conclusion that . . . . their present condition and nature must

be regarded as a secondary and certainly not primitive condition.

“Tn passing, I may just notice that on this supposition an explanation is offered as
to the origin and meaning of the two curious branches which unite respectively the
ganglia of the fifth and seventh and fifth and third cranial nerves ; they may be regarded
as persistent parts of the lateral nerve . . . . in the head.”

In the third place, extracts will be given from Beard’s more extensive paper.” He
writes (p. 97) as an introductory statement :—“< At present we are acquainted with no
Invertebrate nervous system which is built upon the same plan as that of Vertebrates ”;
and then passes to the results of his investigations chiefly carried out on embryos of
Torpedo and a few other Elasmobranchs. I make the following selections (p. 101) :—

“ At the point of fusion” (of the cephalic nerve with the epiblast) “a local thickening
of epiblast has previously taken place. After the fusion has taken place a proliferation
of some of the cells composing the thickening ensues. The proliferated cells form a mass
of actively-dividing elements still connected with the skin. . . . . This mass of
cells is the rudiment of the ganglion of the dorsal root.”

On p. 110 he adds :—* Along with the separation of the (vagus) ganglion from the

1 Karly Development of Rana temporaria, Quart. Journ. Micr. Sct., Suppl., 1885,
2 Branchial Sense-Organs in Ichthyopsida, Quart. Journ. Micr. Sci., November 1885, No. ci.

140 THE VOYAGE OF H.M.S. CHALLENGER.

skin, the sensory thickening begins to grow backwards along the lateral surface of the
trunk. This thickening is the rudiment of the so-called lateral ine. . . . . The
so-called lateral nerve is formed from the deeper portion of the sensory thickening.
. . . . That there is no actual growth backwards of the nerve is obvious enough.”
Recapitulating, we must acknowledge that the mode of origin of the ganglia of the

cephalic nerves, as described by these authors, is certainly a peculiar one—a mode of
development swi generis. One of Beard’s accompanying diagrammatic figures, repro-
duced in Wiedersheim’s second edition (1886) of the Lehrbuch der Vergleichenden
Anatomie as woodcut No. 265, moreover, shows how the position of the cephalic ganglion,
developing as an ectodermal proliferation, is in this early stage eminently lateral, a
conclusion corroborated by the figures of his actual sections. This primitive position is,
of course, gradually lost, and could never be predicted from a study of these ganglia and
their position and significance in the adult animal. Yet it is not without significance,
when seen in the light of the suggestion here brought forward. And that the interpre-
tation of the phenomena in question as given by these authors is not universally accepted,
thus leaving room for new suggestions, is proved by the following citation from Ransom’s
and d’Arey Thompson’s latest article," running as follows :—“ Although the lamprey
presents a well-marked lateralis nerve, it has not also a regular lateral line, for the sense-
organs of the skin are scattered and without segmental arrangement. The sense-
organs do not, therefore, appear to be in direct relation with the spinal ganglia, and the
view of the close connection between them (Spencer, Beard, Froriep) does not receive
support. . . . . It seems more natural to consider the lateralis as a relic of the
extensive and irregular commissure system connecting the posterior roots of Amphioaus.”

Passing from a consideration of the embryonic ganglia to their connection in the
adults, [ must mention the connection of the ramus lateralis vagi with cephalic nerves
anterior to the vagus. I will not here give a description of the numerous varieties pre-
sented by this nervous connection, but merely refer to the arrangement in Vertebrates so
low as the lampreys. We there find, according to Johannes Miiller, the ramus lateralis
originating from the seventh as well as from the tenth pair of cephalic nerves, and if we
compare the very satisfactory figure which was only lately’ given by Ahlborn of this
arrangement, we must recognise that this nervous connection is important, and has more
the aspect of a direct forward continuation of the nervus lateralis than of a sensory branch
from the facialis, establishing a connection between it and the vagus.

Ahlborn mentions the existence of a similar connecting stem reaching further forward
still, and connecting the trigeminus and facialis. How these connections vary in the
different adult Vertebrata will not be discussed here.

The different facts and speculations here brought forward in connection with the

1 On the Spinal and Visceral Nerves of Cyclostomata, Zool. Anzeiger, No. 227, July 1886.
* Zeitschr. f. wiss. Zool.y Bd. x1., pl. xviii.

REPORT ON THE NEMERTEA. 141

cephalic ganglia and the nervus lateralis vagi, may suffice for the present. They may
severally be brought to bear upon the question of the eventual homology of Vertebrate
cephalic ganglia and nervus lateralis, on the one hand, and Vermian paired brain-lobes
and lateral nerve-stems, on the other. The parts here compared, being indicated in figs. 1
and 2 of Pl. XVI. with corresponding letters, Lg and In, a glance at these figures may
further convey a notion of the purport of these speculations.

There is one fact, however, which is not indicated in these figures, which is never-
theless of very high importance for the views here considered, and which I must therefore
develop more in detail.

It is the connection between the successive spinal nerves and the ramus lateralis vagi.

The existence of similar connections between the (eminently sensory and cutaneous)
dorsal roots and the (similarly sensory and cutaneous) lateral nerve is for the first time
mentioned by Ransom and d’Arcy Thompson for Petromyzon in the following passage
(loc. cit., p. 422) :—

“The dorsal rami of the posterior roots pass up (over the lateralis nerve) to the skin
of the back, but appear also to send fibres into the lateralis. (For this statement we at
present rely only on sections, but we hope shortly to test it by dissections of the large
Petromyzon marinus. )”

Tt hardly needs comment that if this observation should be confirmed the fact would
be of the utmost importance for the hypothesis under discussion. We should then be per-
mitted to consider these metameric connections between the dorsal roots and the nervus
lateralis of Petromyzon, as the relics of an earlier stage, still permanent in the Nemertea,
where the metamerically consecutive transverse nerve-tracts similarly unite the medullary
nerve and the lateral stems,

This connection is, as we know, also brought about in the Nemertea by the plexus, in
those parts of it which spread out between the transverse tracts, and it may here be asked
if relics of such a plexus between the successive precursors of the spinal nerves are perhaps
retained, not only in Amphioxus (see above, p. 134, and Rohon, loc. cit., fig. 13), but also
in Osseous Fishes in the numerous superficial nerves described and figured by Stannius,*
or whether we must rather look upon this multiplication of lateral nerves (one of which
is called by Stannius the nervus lateralis trigemini, others, rami communicantes of the
dorsal branches of spinal nerves, &c.) as derivatives from the nervus lateralis vagi.” This
question can, of course, only be solved by careful anatomical and embryological investiga-
tions. That the nervus lateralis was often (Stannius) observed in the Petromyzontidee
only along a part of the length of the body (Schneider and Born, according to Ahlborn,’

1 Das peripherische Nervensystem der Fische, 1849, pls. ii—iv.

2 It should be remembered that Beard is inclined (loc. cit., p. 139) to look upon the superficial longitudinal nerve-
fibres, by which the successive epithelial modifications along the lateral line are often connected (Solger, Bodenstein), as

such derivatives (by longitudinal fission in its very early stages) of the nervus lateralis.
3 Zeitschr. f. wiss. Zool., Ba. xl. pp. 303 and 301.

142 THE VOYAGE OF H.M.S. CHALLENGER.

observed it “bis an das Hinterende des Kérpers”) is not confirmed by modern investi-
gators. Ahlborn’s description (oc. c7t., p. 304) of the variable situation of this nerve in
Petromyzon is very suggestive in connection with the views here advocated. Ransom
and d’Arcy Thompson consider that the regularity of the integumentary sensory
apparatus is not yet established in Petromyzon, as may be concluded from the citation
given above (p. 140).

We have now considered the superficial ramifications of what I may call the lateral
nerve system, both in lower worms and in Vertebrates; we must now turn to the
intestinal, to the visceral branches of this same system, from which other and important
data may be gathered for further elucidation of the hypothesis under consideration.

We have already seen that in Nemertea the typical innervation of the respiratory
portion of the intestine is brought about—(a) by a pair of nerves directed backwards and
springing from the anterior lateral swellings (the brain-lobes) of the lateral nerve-stems ;
(b) by numerous visceral branches starting from the plexus, directed inwards as branches
that spread over the wall of blood-lacunze and intestine,

In the Vertebrata, Amphioxus excepted, we also find that the innervation of the
anterior respiratory portion of the intestine and of the circulatory apparatus is obtained
from two sources, viz., (1) the cephalic nerves, amongst which the vagus nerve is in this
respect the most important’; (2) the visceral branches of the spinal nerves, which are at
the basis of what is afterwards more highly differentiated and separately recognised as
the sympathetic nerve-system.

In Nemertea it is very difficult to determine in the anterior part of the intestinal
wall, which tracts belong to the so-called vagus nerve, which to this system of visceral
nerve-branches.

So it is often in Vertebrata, and the blending together (in both divisions of the
animal kingdom) of two systems, each of them again mutually comparable when separately
considered, is an important point of agreement, and would, if no actual homology were
at the base of it, be a very puzzling coincidence.

It is in this respect highly suggestive that Born notices, as early as 1827, what was after-
wards confirmed by Ahlborn (oe. cit.) and others, that in Petromyzon, 1.e., one of the lowest
Vertebrates, the spinal nerves send out connecting branches towards the pneumogastric
nerves. The existence of superficial metameric connections (Ransom and d’Arcy Thompson,
vide supra) as well as of this set of deeper connections between the transverse and the
latero-longitudinal nerve-stems (n. lateralis and n. pneumogastricus) of Petromyzon would
thus be a most remarkable repetition of the similar arrangement in the Nemertea,
as it has been here for the first time demonstrated.

1 Ventrally these nerves (e.g., the n. hypoglossus) are sometimes commissurally united with their representative of
the opposite half of the body. It must remain an open question whether these commissures are in any way comparable
either to the Nemertean vagus commissures (cf. p. 83), or to the general ventral commissural system of these worms.

REPORT ON THE NEMERTEA. 143

The facts as they lie before us do not, however, admit of any very circumstantial com-
parison so far as the nerves in particular are concerned, and I purposely refrain from
entering into any details. Yetit should be remarked—

(1) That the polymerous root of the Vertebrate vagus nerve is very readily explicable
if we take the Nemertean arrangement as a starting-point (Pl. XVI. figs. 1, 2, vag),
as is also the mixture of sensory and motor elements in this root."

(2) That similarly, if the anterior cephalic nerves (e.g., the fifth) should prove to be
polymerous, this would in no way be astonishing nor difficult to bring into harmony with
that same starting-point.

(3) That the presence of superficial branches to the integument and to the muscu-
lature, and of deeper branches to the intestinal epithelium in those parts that will
contribute to form the cephalic nerves, is similarly foreshadowed in the Nemertea.

(4) That the equivalent of the Nemertean vagus nerve will have to be sought for
in such branches of the Vertebrate vagus as more especially innervate the intestinal
epithelium,’ whereas the innervation of the Vertebrate gill-slits, which marks a later phylo-
genetic stage, in which these perforations of the anterior trunk region have appeared,
may be as well put to the account of more superficial parts of the transverse tracts.

(5) That the common starting-point of the sensory, lateral, and the intestinal
portion of the vagus has also attracted the attention of former observers. Ransom and
d’Arcy Thompson write :—‘ In the embryo dog-fish the second or ventral commissure
described by Balfour, &c., as uniting the roots of the vagus, ventral to the ganglia, is
essentially a sympathetic commissure, whose (visceral) fibres pass on, as described by
Balfour, to form the intestinal branch of the vagus. In that intestinal branch we have
an outflow of visceral fibres, quite comparable to, e.g., a splanchnic branch of the dorsal
sympathetic system. The connection between the origin of the lateralis and this ventral
commissure connecting the vagus roots in the dog-fish, and similarly the relation of the
lateralis to the loops uniting the ganglia of the 5th, 7th, and 10th nerves in
Petromyzon may probably be described as indicating a fusion in this region of
the two great commissural systems which posteriorly are separate, viz., that of the
sensory branches (lateralis) and the visceral or sympathetic.

1 Rohon, Ueber den Ursprung des Nervus vagus bei Selachiern, Arbeit. Zool. Inst. Wien, vol. i. p. 159.

2 T have good reasons, based upon actual observations made by my pupil, Mr. Dobberke, to believe that the ramus —
intestinalis vagi in adult Elasmobranchs may be traced centripetally from its region of innervation of the foremost portion
of the intestinal wall, towards the brain, as a bundle of nerve-fibres running parallel to and combined with those for the
branchial apparatus, but that, nevertheless, this bundle can be separately traced up to the vagus ganglion, without any
further intimate relation to those branchial branches (cf. Beard, loc. cit., p. 110). If this should actually be the case,
the possibility of a direct comparison between the Nemertean vagus nerve and the Vertebrate ramus intestinalis vagt, of
course, comes more closely within ourreach. It need not be insisted upon that if these comparisons prove correct, the
separate intestinal nerve-systems (sympathetic nerve system) of other Invertebrates (Annelids, Arthropods, Molluscs)
cannot be looked upon as homologous with the sympathetic nerve system of the Vertebrates, but would rather be
homologous with that portion of the intestinal innervation of the latter which comes to the account of their cephalic
nerves, in so far as these represent derivatives of the Nemertean vagus, and are marked v in figs. 1 and 2 of Pl. XVI.

144 THE VOYAGE OF H.M.S, CHALLENGER.

““ We agree with Gaskell that the term sympathetic should be suffered to fall into disuse,
as tending to perpetuate the old conception of the primary importance of the longitudinal
nerve-tract ; whereas the leading fact is the metamerically recurring outflow of visceral
fibres, which may or may not be united together by successive longitudinal commissures.”

In the Nemertea this anterior “fusion of the great commissural systems” is
foreshadowed at the point where brain-lobe, lateral stem, and “‘ vagus nerve” meet, or
rather diverge. It has been attempted in figs. 1 and 2 to indicate the points here
alluded to in a general way, special comparisons being, on the grounds that have been
stated, purposely avoided.

If we now turn to Dohrn’s and Semper’s hypothesis we must recognise that no such
satisfactory general comparisons are there possible. Even if we were inclined to accept
the “turning over” of Geoffroy St. Hilaire, by which back and belly became exchanged,
and to admit the braim-piercing cesophagus, regarding the Annelid supracesophageal
ganglion and the ventral nerve-cord as respectively homologous to cerebrum and
medulla, it must still be conceded that we have not then in any way before us a nerve
system offering as many points of comparison with the Vertebrate system as does that of
the Nemertea,

Concerning the Annelids we have no observations by which the cephalic ganglia and
the cephalic nerves are so clearly foreshadowed, none which would throw hight on the origin
of the vagus, its connection with the nervus lateralis and with the anterior cephalic
ganglia, none concerning the sympathetic system and its blending with the vagus system
in the lowest Vertebrates, indications of which are even retained in the highest. Nor is
the ventral nerve-cord of Annelids, with its undeniable double character and double
origin a match, so far as comparison goes, for the Nemertean medullary nerve, with its
transverse nerves preceding the spinal nerves of Amphioxus and the Cyclostomata.

And if we are then asked to consider the lens of the Vertebrate eye as a modified
ectodermal branchial invagination, as the outer portion of what was once a functional
gill-slit," we feel that the ground under our feet is becoming rather uncomfortable, and
that it is bigh time to reconsider whether all these ingenious speculations in which the
most beautifully pliable hypothetical and unknown Annelids play a too conspicuous part
should not be definitely abandoned, and a new departure made by those who are interested
in the phylogeny of the Chordata. In due time arduous and detailed morphological
investigations on the Platyelminthes in general, and on the Nemertea in particular, may
then lead us to more satisfactory conclusions than are the fata morgana that are so
temptingly evoked before our eyes by the ingenious manipulations of the indefatigable
founder of the first and foremost Zoological Station, when, following his lead, we find
ourselves wandering in the barren deserts of that province of phylogeny, in which he
attempts to establish a close connection between Chordata and Annelida.

1 Dohrn, Studien, x, p. 459, 1885,

REPORT ON THE NEMERTEA. 145

All these considerations have induced me to give this rapid outline sketch of the
degree of comparison which I hold to exist between Chordate and Nemertean (more
especially Paleeonemertean and Schizonemertean) nervous systems, although I am per-
fectly aware that there is a growing tendency among those authors at present occupied
with questions concerning the morphology of the Vertebrate nervous system (Froriep,
Baldwin Spencer, Beard, Cunningham, Kleinenberg, and many others) to accept
Semper’s and Dohrn’s views of the Annelidan descent of Vertebrates. Wiedersheim,
in the new edition of his “ Vergleichende Anatomie ” (1886), does not even hesitate to
bring these results in their unripe phase before the more extensive public of students, and
this generally in acquiescent terms. It is curious to see how, e.g., the question of the
cephalic nerves and their comparison to spinal nerves, that of the nerve-roots, the
cephalic ganglia and their respective connecting trunks, have given occasion to the most
diverse twisting and retwisting of the facts in order to bring out a fixed scheme or
diagram, which might then be compared to what obtained in Annelids, and in which
the highest degree of similarity between the respective somites might be obtained, thus
establishing a preconceived idea of the Vertebrate ancestor as a most rigorously seg-
mented animal. The value of these speculations has been already tested above, and I may
be allowed once more to express my conviction that our comparisons between the Chordata
and their lower Invertebrate predecessors may only be looked upon as in any way satis-
factory so long as they remain on a very broad and general basis, and that any very
special homology said to be demonstrated ought for that very reason to be more especially
suspected."

For my part I believe that, along the lines above indicated, a comparison between
Vertebrate and Invertebrate nervous systems will in future prove to be more fruitful, but
I wish to repeat that for the present we can only indicate general points of coincidence
between the two, and must rigorously refrain from making comparisons in detail.

On the other hand, it is suggestive once more to consider what has been recorded
above (p. 89) concerning the nervous system of Drepanophorus lankesteri, when
compared with that of certain Annelids; and we may, I believe, safely come to the
conclusion which was formulated by me seven years ago, but which I now hold to be
much more solidly established, that we have in the Nemertea an important group
through which definite glimpses may be obtained at the sources from which both
Chordata and Appendiculata (Ray Lankester) have respectively sprung. The proposition

1 Bateson (loc. cit., p. 562) seems to take a similar view of the efforts here alluded to. He says :—“No doubt
the cranial nerves may, by arbitrary divisions and combinations, be shaped into an arrangement which more or less
simulates that which is supposed by some to have been present in the rest of the body, but little is gained by this
exercise beyond the production of a false symmetry.”—Dohrn himself, whose suggestions have so largely contributed to
the accumulation of all this conflicting evidence, is now rather in the position of Goethe’s Zauberlehrling, and writes

(Studien, x., p. 468, 1885)—“ Auch auf diesem Gebiet (die Frage nach der Bedeutung der Hirnnerven)bildet die bisherige
. dj < ° on ° ~ L ae Sohiffes ”
vergleichende Anatomie das Bild eines auf stiirmischer See steuerlos herumgeschleuderten Schiffes.

(ZOOL. CHALL. EXP. —PART LIV.—1887.) Hhh 19

146 THE VOYAGE OF H.M.S. CHALLENGER.

first formulated by Gegenbaur, about the phylogenetic origin of the ventral nerve-cord
and cesophageal ring of the Annelida out of ancestors with lateral cords, has obtained new
support from the arrangement which was met with in the species just mentioned. And
just as we have before tentatively discussed the question, in how far remnants of the
lateral cords were retained in those descendants in which the median one had been raised
to the dignity of a medulla spinalis (the Vertebrata), we might now consider whether any
remnants of the median dorsal cord are retained in those descendants in which the lateral
cords have differentiated into brain-lobes, cesophageal ring, and ventral cord (the
Annelida). To this question I have no definite answer to offer, but I may call attention
to the significant fact that the beautiful and exemplary investigations into the embryonic
development of Lopadorhynchus, very recently published by Kleinenberg,’ have
demonstrated the existence in the larva of that Annelid, of a nerve-stem answering to the
conditions here required. It is dorsomedially situated, it is anteriorly connected with
the brain, or rather with a transverse nerve-tract (Kleinenberg’s prototrochal nerve-ring),
which in its turn is connected with the brain,’ it appears to be connected close to the
anus with the ventral cord (the fused lateral stems), and though appearing in early
larval life, and having only a temporary existence, it is regarded by Kleinenberg as
having considerable physiological importance. If the light in which I am inclined to
look at it is not deceptive, its morphological significance also can hardly be overrated.

In closing this chapter of general considerations, we may once more bring before
our minds the proposition with which it was opened. We have here and in the foregoing
chapters adduced facts and arguments which appear to speak in its favour; we will once
more rapidly enumerate the common characteristics of Nemertea and Ccelenterata, as
well as those of Nemertea and Chordata.

The Ccelenterate characteristics that are also found in the Nemertea are the fol-
lowing :—

a. The presence of nematocysts in the proboscidian epithelium.

b. The elaborate nerve-plexus in the integument, and its histological features.

ce. The presence of epiblastic muscle-fibres separate from the general body-
musculature.

d. The presence and the chemical constitution of a sometimes very massive
intermuscular jelly, by which the other internal organs are at the same
time surrounded.

e. The mode of development of the mesoblast (at least in Lineus obscurus),
which is less specialised than in most other Invertebrates.

Jf. The absence of any distinct enterocoele.

1 Zeitschr. f. wiss. Zool., Bd. xliv., Heft. i, ii., October 1886, p. 107; pl. vii. fig. 27a.
* For comparison with the Nemertea, ef. pl. xvi. fig. 1.

REPORT ON THE NEMERTEA. 147

The points of resemblance with the Chordata may be thus tabulated :—

a. The general features of the nervous system.

b. The presence of a homologue of the hypophysis cerebri as a massive and
important organ (the proboscis).

c. The presence of tissues which may have become converted into the notochord
(viz., the material of which the proboscidian sheath is built up).

d. The respiratory significance of the anterior portion of the alimentary tract.

At the base of all the speculations contained in this chapter lies the conviction,
so strongly insisted upon by Darwin, that new combinations or organs do not appear by
the action of natural selection unless others have preceded, from which they are gradually
derived by slow change and differentiation.

That a notochord should develop out of the archenterie wall because a supporting
axis would be beneficial to the animal may be a teleological assumption, but it is at the
same time an evolutional heresy. It would never be fruitful to try to connect the different
variations offered, e.g., by the nervous system, throughout the animal kingdom, if similar
assumptions were admitted, for there would be then quite as much to say for a repeated
and independent origin of central nervous systems out of indifferent epiblast just as
required in each special case. These would be steps that might bring us back a good
way towards the doctrine of independent creations. The remembrance of Darwin’s,
Huxley’s and Gegenbaur’s classical foundations, and of Balfour's and Weismann’s
brilliant superstructures, ought to warn us away from these dangerous regions,

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LIST OF AUTHORS REFERRED TO IN THE TEXT.

I. J. Barrors, Recherches sur l’Embryologie des Nemertes, Ann. d. Sct. Nat., sér. 6, vol. vi, 1877.
II. R. Dewoterzxy, Zur Anatomie der Nemertinen, Zool. Anzeiger, Jahre. iii, 1880, pp. 872-306,
III. L. von Grarr, Geonemertes chalicophora, eine neue Landnemertine. Morph. Jahrb, Bd. v.
p. 480.
IV. A. A. W. Husrecut, Aanteekeningen over de Anatomie, Histologie en Ontwikkelingsgeschiedenis
der Nemertinen, Utrecht, 1874.

V. Untersuchungen iiber Nemertinen aus dem Golf von Neapel, Niederliindisches Archiv
Sir Zoologie, Bd, ii. S. 99.
VI. Some Remarks about the Minute Anatomy of Mediterranean Nemerteans, Quart. Journ.
Mier. Sct., vol. xv. p. 249.
Vil The genera of European Nemerteans critically revised, with Description of Several New
Species. Notes from the Leyden Museum, vol. i. p. 193, 1879.
VIII. New Species of European Nemerteans. Notes from the Leyden Museum, vol. ii.
TX. Zur Anatomie und Physiologie des Nervensystems der Nemertinen, Verhandel. van de
Koninkl. Akad, van Wetenschappen, Amsterdam, 1880, vol. xx.
xX. The Peripheral Nervous System of the Paleo- and the Schizonemertea, one of the layers
of the body-wall, Quart. Journ. Mier. Sez., vol. xx., 1880.
XI. Zur Nemertinen Anatomie, Zool. Anzeiger, Jahrg. iii., 1880, p. 406.
XIa. On the Ancestral Forms of the Chordata, Quart. Journ. Mier. Sci., vol. xxiii., 1883.
XII. Der excretorische Apparat der Nemertinen, Zool. Anzeiger, 1885, p. 51.
<i: Zur Embryologie der Nemertinen, Zool. Anzeiger, Jahrg. viii., 1885, p. 460.
XIV. Proeve eener ontwikkelingsgeschiedenis van Lineus obscurus Barr, Utrecht, 1885.
XV. Contributions to the Embryology of the Nemertea, Quart. Journ. Mier. Sci., vol. xxvi.,

1886.
XVI. J. von Kennet, Beitrige zur Kenntniss de Nemertinen, Arbeit. zool.-zoot. Inst, Wurzburg,
Bad. iv., 1878.
Die in Deutschland gefundenen Landplanarien, Arbeit. zool.-zoot. Inst. Wiirzburg,
Bd. v., 1882.
XVIII. A. Lane, Monographie der Polycladen, Leipzig, 1884.
XIX. W.C. M‘Intosn, A Monograph of the British Annelids—A. Nemerteans, Ray Soctety Publica-
tions, 1873, 1874.

XVII.

xX. On Amphiporus spectabilis, Quart. Journ. Mier, Scz., vol. xv. p. 273.
XXII. On the Central Nervous System, the Cephalic Sacs, and other points in the Anatomy of
the Lineide, Journal of Anatomy and Physiology, vol. x. p. 231.
XXII. Marine Annelida from Kerguelen’s Land, Phil. Trans. Roy. Soc. Lond., vol. clxviii.
(extra vol.), London, 1879.
XXIII. Description of some New Species of Annelida from Kerguelen’s Island, Anz. and Mag.

Nat. Hist., ser. 4, vol. xvii., 1876.

150 »»

XXIV,

XXV.
XXXVI.

THE VOYAGE OF H.M.S. CHALLENGER.

. W. C. M‘Intosu, On Valencinia Armandi, a New Nemertean, Zrans. Linn. Soc, Lond., ser. 2,
vol. i., 1879.

H. N. Mosetey, On Pelagonemertes rollestoni, Ann. and Mag. Nat. Hist., vol, xv., 1875.

On a young specimen of Pelagonemertes, Ann. and Mag. Nat. Hist., vol. xvi., 1875.

XXVIII. A. C. OupEmans, The Circulatory and Nephridial Apparatus of the Nemertea, Quart. Journ, Micr.

Sez., Suppl, 1885.

XXVIII. A. pE Quatreraces, Mémoire sur la famille des Némertiens, Ann. d. Sci. Nat., (3), vii., 1846.
XXVIIIa. A. Sapatier, La spermatogentse chez les Némertiens, Revue Se. Nat. Montpellier, (3), t. ii, 1883.

XXIX.
XXX.
XXXII.
XXXII.

XXXII

W. Satensxy, Recherches sur le développement du Monopora, Archives de Biologie, t. v.

Bau et Metamorphose des Pilidium, Zedtschr. f. wiss. Zool., Bd. xliii. p. 481.

A. Scunemwer, Untersuchungen iiber Plathelminthen, Giessen, 1873.

M. Scuutrze, Beitriige zur Naturgeschichte der Turbellarien, Greifswald, 1851.

. BR. von Wittemors Suum, On a Land-Nemertean found in the Bermudas, Ann. and Mag. Nat.
Hist., ser. 4, vol. xiii. p. 409.

LEAN AD dy OK:

PAGE
INTRODUCTION, : : : é 3 : . ; s 1
I. DESCRIPTION OF THE SPECIES AND GENERA, : . ; ; : is

A, PaLmONEMERTEA—
Carinina grata, 5
Hupolia delineata, 11
eels 11
» australis, 13
» Ripponensis, 14

B, HorpLoneEMERTEA—
Drepanophorus rubrostriatus, 15
0) serraticollis, 17
- lankestert, 18
Amphiporus moseleyt, 20
y mariont, 22
Tetrastemma agricola, : ‘ ; : : ; 5
cs Suscum, , 2 : ‘ : ; : : 25
Pelagonemertes rollestont, . : ‘ : a ‘ ; . 25

C. ScHIzoNEMERTEA—
Cerebratulus truncatus, . : ; F 3 : : : 37
5; medullatus, . : ; : : : 5. ak)
of) longifissus, . : : ‘ ‘ ; : : 40
3 corrugatus, . : , : ‘ : 41
0 parkert, : : : j : : : . 43
a angusticeps, . ‘ : ; . : F 5 44
is macroren, . ‘ : : : . ; : 46
if sp. inc., F ; : : ; : : ; 47
List oF STATIONS AT WHICH NEMERTEA WERE OBTAINED, : ; , : : 50

Il. ANATOMY—

INTEGUMENT, , ‘ : : d ‘ , 18)
Muscunar System, Cairne Teeeeral &e., “ : : ; . Sy
Nervous System, : = te
SENSE-ORGANS, ACCESSORY GuaNpUtar SraveruREs, AND Gneans OF = Unzxown SranIFICANcE, 90
PRoBoscis AND PROBOSCIDIAN SHEATH, : , : : : ‘ . -98
DicestiveE APPARATUS, . : : ; ‘ : A koe
NEPHRIDIAL AND BLoop- svikecenie rene : : : : : . 112
GENERATIVE ORGANS, : F ‘ : 5 : : . a aliley
Il]. GENERAL CONSIDERATIONS, . ; : ; : 2

LIST OF AUTHORS REFERRED TO IN THE TEXT, . ; : : 5 let)

PLATE I.

PLATE I.

‘
Fig. 1. Carinina grata, n. gen. et sp. A ventral view of one specimen. Terminal proboscidian opening visible, as well
as the terminal ciliated groove, the lateral ciliated groove and the ventral mouth. x about 35.

rg
a
IS

i)

Carinina grata, n. gen. et sp. A side view of same specimen, showing the terminal ciliated groove, the lateral
ciliated groove and the ventral mouth. x about 34.

Fig. 3. Carinina grata, n. gen. et sp. A ventral view of another specimen, showing the terminal proboscidian opening,
and the terminal ciliated groove. x about 35.

Figs. 4, 5. Eupolia nipponensis, n. sp. Right and left lateral view of one of the specimens. Natural size.

Fig. 6. EZupolia australis, n. sp. Ventral view of the head. The mouth is very small, the surface transversely wrinkled.
x 4,

Fig. 7. Eupolia giardii, n. sp. Tip of head, viewed from above. x 2.
Fig. 8. Eupolia giardii, n. sp. Dorsal view of the head. x 2.

Fig. 9. Hupolia giardii, n. sp. Ventral view of the head. x 2,

=

Fig. 10. Hupolia nipponensis, n. sp. Another specimen, seen from below. The mouth is very small.
Fig. 11. Cerebratulus truncatus, n. sp. Side view. x 4.

Fig. 12. Cerebratulus truncatus, n. sp. Another specimen, ventral view of tip of head. x 8.

Fig. 13. Cerebratulus macroren, nu. sp. Ventral view of tip of head of New Zealand specimen. x 15.
Fig. 14. Cerebratulus macroren, n. sp. Lateral view of do. do. do. x 15;

Fig. 15. Cerebratulus angusticeps, n. sp. Lateral view of the anterior portion of the lacerated specimen (1100 fathoms).
Part of the proboscis protrudes through a rupture in the body wall. x 14.

Fig. 16. Cerebratulus longifissus, n. sp. Lateral view. Natural size.

Fig. 17. Cerebratulus corrugatus, n. sp. Lateral view of a young specimen. x 2.

Fig. 18. Cerebratulus macroren, n. sp. Ventral view of the Japanese specimen. Natural size.
Fig. 19. Cerebratulus macroren, nu. sp. Lateral view of do. do. do,

Fig. 20. A mphiporus moseleyi, n. sp. One of the specimens, seen in perspective. Natural size.

Fig. 21. Amphiporus moseleyi, n. sp. Anterior part, showing cephalic groove and subterminal opening (indicated by a
cross fold) which leads into the proboscis and the intestine. Natural size.

Fig. 22. Drepanophorus lankesteri, n. sp. Dorsal view. Natural size.

Figs. 23-31. Pelagonemertes rollestont, H. N. M., after Moseley, who explains the figures as follows :—

Fig. 23. “ Pelagonemertes Rollestoni, enlarged, viewed from the dorsal surface ; the proboscis is partly extruded ;
P7.8., sac of proboscis ; 7P., invaginated portion of proboseis within the proboscis sac: G, superior
nerve ganglion ; V.C., nerve cords; V, vascular trunk (the upper V points to an enlargement of the
vessel lying just posteriorly to the superior nerve ganglion); /, intestine ; D, diverticula of intestine ;
A, anus ; OO, ovaries; CV, circular muscles ; LM, longitudinal muscles.

Fig. 24. ‘* Pelagonemertes Rollestoni, from the ventral surface, x 2 diameters. 1, Mouth, with esophagus ; 2, partl
g ) > phag partly

protruded proboscis ; 3, nerve ganglia; 4, nerve-cords ; 5, ovaries; 6, digestive canal. The sheath of
the proboscis is seen through the body lying behind the digestive canal.

Fig. 25. “ Sketch of the proboscis-sheath and contained retracted proboscis, from the dorsal aspect. Retractor
muscles inserted into the commencement of the sheath.

Fig. 26. ‘1, One of the polygonal areas, enlarged, showing the wrinkles of integument producing the appearance.
2, Peculiar appearance of some of the folds of the integument.

Fig. 27. ‘‘ Reticular appearance of the integument observed in certain parts of the body. Natural size.

Fig. 28. ‘‘a, Groups of brightly coloured fatty globules forming the contents of the diverticula of the intestine ;
6, portion of the vascular trunk, much enlarged.

Fig. 29. ‘* Portion of the invaginated proboscis, much enlarged. a, External gelatinous layer ; ), internal muscular
layer ; c, cavity continuous with that of the proboscis-sac ; within these the invaginated portion of the
proboscis with the layers reversed ; 0, internal muscular layer ; @, external gelatinous layer! ; d, central
tube filled with dark amorphous matter (from the proboscis-sac ¢).

Fig. 30. “ The nervous ganglia and ring, much enlarged. A, Superior ganglion ; B, inferior ganglion.

Fig. 31, “ One of the ovaries, enlarged. The dark irregular line on the centre represents what is probably an aperture
for the discharge of ova.”

! This figure has been incorrectly lettered by the lithographer, a,b,c furthest to the right should be e,b,a,

siti

The Voyage of HMS “Challenger”

Nemertea. PII

\
i

>W.vd Weyer ltr
CARININA. EUPOLIA.CEREBRATULUS. AMPHIPORUS. PELAGONEMERTES. lath PW.vd Werjer-Utr

PLATE IL. 7

PLATE II.

J. Integument. | Ps. Proboscidian sheath-cavity. AV. Lateral nerve-trunks.

M. Musculature. | Pr. Proboscis. im, cm. Musculature of the proboscis.

bl. Blood-space. | D, Intestinal cavity. de. Epithelium of do.
aPr. Rhynchodeum. | C. Brain-lobes. P.N. Nerve-stems of do.

Po. Proboscidian opening. Comm. Inferior brain commissure. |

Figs. 1-7. Carinina grata, n. gen. et sp. Transverse sections and parts of sections of one of the specimens in which the
proboscis was protruded and ejected from the body—drawn with the camera. The integument and what
pertains to it is tinted light sepia, the nervous system yellowish, the muscular investment of the body red,
the intestinal epithelium grey.

Fig. 1. Section through the tip of the head and the anterior point of meeting (02) of the two lateral blocd-spaces.
The terminal furrow at the tip of the head (cf. Pl. I. figs. 1, 3) has been touched in the left lower
corner of the section.

Fig. 2. Section somewhat further back in which the blood-space shows a right and a left portion, and in which the
anterior wall of the rhynchodzeum (cf fig. 8, aP7r) has been touched, the first indication of the opening
through which the proboscis is thrust forward being also visible in this section.

Fig. 3. Section through the brain thickenings (ec), the ventral commissure and the prestomial blind portion of the
cesophagus.

Fig. 4. Section through the mouth region. To the left the blood-space appears to be locally subdivided by radial
strands of tissue.

Ra

Fig. 5. Section through the wsophageal region. The layer of longitudinal and inner circular muscle fibres are

separated by a thin black line. The blood-spaces are more or less enclosed in the latter layer.

Figs. 6, 7. Two sections, still further back, of the inner circular muscular layer and what is encompassed by it.
These sections show the change in shape which both the proboscidian sheath-cavity and the blood-
spaces undergo in different portions of the body.

a
iQ

ig. 8. Carinina grata, n. gen. et sp. A horizontal section through the head, brain-lobes and proboscidian insertion of
the second specimen, in which the proboscis had remained attached and inverted (c/. Pl. III. fig. 4).

Fig. 9. Carinina grata, 1. gen. et sp. Section further backwards (¢f. fig. 3). (The specimen being curved this section
and the following are no longer horizontal but transverse).

Fig. 10. Carinina grata, n. gen. et sp. Section further backwards still (¢f. fig. 5).

Figs. 9 and 10, when compared with figs. 3 and 5, give an idea of the change effected upon the body musculature
by the inversion and eversion of the proboscis. Some latitude must, however, be left for the fact of the
specimens being different.

Figs. 11, 12. Carinina grata, n. gen. et sp. Two transverse sections through the proboscis, with the external thin homo-
geneous layer enclosing the outer longitudinal (brown) and inner circular (red) muscular layer. Inside the
latter is the proboscidian epithelium. The two strong nerves of the proboscis are still enclosed in this
epithelium, as are the nerve-trunks of the body in the integument.

Nemertea_ Pill

Voyage of HMS “Challenger”

lihPW.vd WeierUtr,

CARININA.

A

PLATE I].

PART Liv. —1887. )—Hhh.

Fig.

Fig.

i)

PLATE III.

. Carinina grata, n. gen. et sp. Longitudinal section through a loop of the proboscis. In the

upper section the proboscidian epithelium (Pe) is much more columnar, in the lower one
it is thrown into folds and much more loosely applied against the musculature.

Carinina grata, n. gen. et sp. A part of the last mentioned region, more considerably enlarged.

Carinina grata, n. gen. et sp. A longitudinal section through the body-wall. Cm, the inner
circular muscular layer (6 of Pl. XL); 2M, the longitudinal muscles (a of Pl. XI.); ec, the
outer circular muscular layer (8 of Pl. XI); B, the homogeneous basement membrane ; WV/,
the deepest layer of the integument, with plexiform nerve tissue (the lithographer has given
too stellate an appearance to these histological elements); G7, the deeper glandular stratum ;
E, the outer stratum of the integument.

Carinina grata, n. gen. et sp. The same, in a region where the gland-cells of the glandular
stratum are all considerably reduced and the basement membrane contracted into waves.
The nervous plexus is not indicated in this figure. Lettering as in fig. 3.

Carinina grata, n. gen. et sp. A horizontal section through the point of insertion of the pro-
boscis in the head. The cellular integument is coloured red. /, the musculature, chiefly
longitudinal, from which fibres emerge to pass backwards into the musculature of the proboscis,
the epithelium of which is marked Pe. Other radial fibres attach the rhynchodeum in the
head, the cellular coating of which (A Pe) is thicker and more vacuolated than that of the pro-
boseis. 1 (upper), blood-space in the head; 7 (lower), space of proboscidian sheath ; cf,
cephalic furrow.

Carinina grata, n. gen. et sp. More enlarged figure of a transverse section'of the body-muscu-
lature. Lettering asin fig. 3. Moreover, ct, hyaline gelatinous tissue between the muscular
bundles, carrying nuclei. Other nuclei are detected in the centre of the muscle bundles.
To the left of the layer Cm there is a faint indication of what is possibly a second internal
layer of plexiform nerve-tissue.

. Carinina grata, n. gen. et sp. Enlarged figure of a transverse section of the lateral nerve-stem.

Nst, the fibrous core with sparse nuclei; Vgc, the cellular investment of the stem, continued
into V/, the nerve plexus, all three still forming part of the deeper layers of the integument,
which by the basement layer B (not passing over the nerve-stem) is separated from the
subjacent muscular layers (ec); Gz, the deeper gland-cells of the integument. The nerve-trunk
is attached by fibres binding it down to the muscular layers.

ig. 8. Carinina grata, n. gen. et sp. The same in tangential section, Lettering as in the preceding figure.

The attaching fibres are seen to be not continuous but arranged im closely set bundles. The
integumentary gland-cells show different colours in the left and in the right half of the
section ; in the intervening region they are not developed; this would thus correspond to
such a region as is represented in fig. 4 in longitudinal section.

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PLATE IV,

PLATE IV.

The basement membrane and the nephridial apparatus are on this plate indicated by a red tint.

Fig. 1. Carinina yrata, n. gen. et sp. A longitudinal section through the body-wall at the point where
the terminal duct of the nephridia (Vc) pierces it. Ld and ec, muscular layers (see Pl. III.
figs. 3, 4); B,basement membrane; /, cellular integument, with superficial and deeper
gland-cells, separated by a layer of closely contiguous nuclei that belong to extremely
elongated cells, placed perpendicularly to the surface.

Fig 2. Carinina grata, n. gen. et sp. Section through a region where the nephridial canal (Vc) is still
enclosed in the blood-space (Bs) in which a distinct cellular coating is observable, and
which is separated from the intestinal ceca (Je) by the inner circular muscular layer (cf,
Cm, figs. 5, 6); LM, the outer longitudinal muscular layer.

Fig. 3. Carinina grata, nu. gen. et sp. A longitudinal section through the oesophagus (Oe). Je, its ciliated
epithelium directly applied upon the muscular layers Cm, LM, and ec (see Pl. III. fig. 3);
PSW, the proboscidian sheath-wall, very thin, with the cesophageal epithelium below
and its own nuclei above it. This fibrous wall is confluent superiorly with the layer of
circular muscles Cm (cf. Pl. IT. figs. 5, 9, 10).

Fig. 4. Carinina grata, n. gen. et sp. Section through the spongy and canalicular part of the nephridium
(Vsp), and the region where it communicates with the principal nephridial duct Ve; Bs, Je,
LM, and Cm, as in the preceding figures,

Figs. 5,6. Carinina grata, n. gen. et sp. Transverse sections of the same system. The nephridia lie in
the blood-spaces (Bs) which have their own cellular coating, and are partly enclosed in the
circular muscular layer Cm. Ps and Oe indicate the respective situation of proboscidian
sheath and cesophagus in relation to the nephridia; Vsp and We as in fig. 4.

Fig. 7. Carinina grata, n. gen. et sp. A portion of the cesophageal epithelium under higher power. Je
fo) J > 5 ] } fo} 5
the granular epithelium cells; ¢, the cuticula with the cilia,

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dcm, Dorsal commissure.
vem, Ventral commissure.
SZ, Superior lobe separated into two | ZN, Lateral nerve-stem, with fibrous core | yx, Innervation for the proboscis.

lappets by a sulcus.

PLATE V.

PL, Posterior lobe. vg, Innervation for the respiratory part
cc, Ciliated canal to the exterior. of the cesophagus (n. vagus).

and cellular coating. an, Cephalic nerves.

Figs. 1-9. Hupolia giardii, n. sp. Reconstructions of the brain-lobes from a series of sections.

Figs

Figs.

Figs.
Figs.

Figs.

Fig.

Figs.

1, 2, 3, 4, 8 represent the outward aspect, viewed from different sides.

. 5, 6, 7, 9 represent the fibrous core ; the extension of the ganglion cells enclosing this core being

indicated by faint outlines.

. Seen from above.
. Seen from below.
. Seen laterally and outwardly.

Seen from behind.
Seen laterally and inwardly (after section of the commissure and removal of the left half).

In figs. 5 and 6 the course of the ciliated canal is specially indicated ; in the former figure
by a red outline.

The Voyage of HMS ‘Challeng er”

Nemertea. PLV

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Lith PW.vd Weyer Utr

Hubrecht et Oudernans del. EUPOLIA

PLATE VI. 9

PLATE VI.

Fig. 1. Carinina grata, n. gen. et sp. The brain as situated in the deeper strata of the integument,
seen in horizontal section (cf. woodcut fig. 5, p. 81). Br, Br, the anterior and the posterior
brain-lobes. The inner fibrous core of these lobes white ; in the anterior lobe traversed by
radial fibres, in the posterior one containing the ciliated canal cc, that opens out in fig. 2 into
the cephalic groove Cy ; Nye, the nerve-cells of the brain-lobes (stretching outwards as far as
the red tint is applied in the figure); g/.lr, glandular cells connected with them; 4, the
outer layer of the integument ; G7, the deeper one with gland-cells ; ec and ZM/, muscular
layers ; bs, blood-lacuna between the cesophagus and the muscular body-wall ; Oe, lumen,
Ie, epithelium of cesophagus ; Nv, branches of the so-called vagus nerve.

Figs. 2,3. Carinina grata, n. gen. et sp. The posterior byain-lobe in following and preceding sections.
Lettering as in fig. 1.

In all these three figures a marked increase of the nuclei in the immediate vicinity of the
cephalic groove is particularly distinct.

Figs. 4-8. Hupolia giardii, n. sp. Transverse sections through different parts of the brain. Com-
pare the figures on P]. V. The fibrous core white, the nerve-cellular coating light red.

Fig. 4. Section through the lower commissure, just in front of the upper commissure. Pr, proboscis, the
innervation of which, proceeding from the two brain-lobes, is noticed in this section (ef. Pl. V.
fies. 5, 9).

Fig. 5. Seetion through both commissures, 7.¢., a few sections further back.

Fig. 6. A few sections still further back, through the point of origin of the vagus nerve (Nv). Prs,
anterior terminal portion of the proboscidian sheath.

ee}
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. Section through superior, inferior and posterior lobe ; the latter coated by the granular glandular
cells gl.br, and with the ciliated canal ce.

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gg

. 8. In the superior lobe the fibrous core has again subdivided, giving off an uppermost stem, the
centre of the outwardly visible superior gyrus (¢f. Pl. V. figs. 5, 7).

Fig. 9. = Hupolia giardii, nu. sp. Part of a transverse section through the cesophageal region,
em and Ilm, the circular and inner longitudinal muscular layer (8 and a of Pl. XI. fig. 12);
PI, the nerve plexus just outside the former; st, the lateral nerve-stem in this plexus ;
Prs, the proboscidian sheath with very thin walls ; dv, the dorsal blood-vessel, situated, as
are a dozen of circumcesophageal lacunar spaces (that communicate with each other), in the
gelatinous tissue between body-wall and intestinal wall. Oe, the lumen of the cesophagus ;
Ze, its ciliated epithelium ; oe.m, its longitudinal and circular musculature ; rep, nephridian
tubes. The thin longitudinal nerve-stem above the proboscidian sheath has been omitted
in this figure.

Fig. 10. Hupolia giardii, nu. sp. A transverse section of the dorso-median portion of the body-wall
at the furthest end of the body. em, zlm, Prs, as in fig. 9. olm, outer longitudinal
muscular layer (y, Pl. XI.); Bet, the much folded primary basement layer ; g, the deeper
glandular layer of the integument; ef, the longitudinal and circular fibres of the same ;
£, the outer layer of the integument (cf. Pl. VIL fig. 5 and Pl X. fig. 6); bv, dorsal
blood-vessel.

Fig. 11. Hupolia giardii, n. sp. Transverse section through the posterior part of the proboscis,
with internal epithelium (Pre), longitudinal muscle-fibres (Lm), and external flattened epi-
thelium (e).

Nemertea. PLVI

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PLATE VII.

Fig. 1. Hupolia australis, n. sp. Diagram of a section through the posterior part of the csophageal
region. Ps, proboscidian sheath with underlying dorsal blood-vessel ; bs, lateral blood-
spaces, continued backwards, but not much further than the cesophageal region ; by, ventral
blood-vessels ; Oc, cavity of the esophagus; Wst, lateral nerve-stems ; /, outer integumentary
layer.

Fig. 2. Hupolia wustralis, n. sp. Section of the body-wall about in the same-region as the diagram of
fig. 1, and in the vicinity of the left ventral blood-vessel. #, outer epithelial layer with
unicellular glands ; B, its (secondary) basement membrane; ef, scattered longitudinal and
circular fibres beneath this; gi, subepithelial glandular layer; olm, outer longitudinal
muscles, as yet very far from being a compact layer ; cm, circular muscular layer; i/m, inner
layer of longitudinal muscles; ct, cellular coating of the cireumcesophageal blood-space.
(Between olm and gi the reference letter Bet, indicating the primary basement tissue
(cf. figs. 3, 5), should be inserted.

Fig. 3. Eupolia australis, n. sp. Section of body-wall of the same specimen, very much further back.
Lettering as in fig. 2. Moreover, Bet, fibrous connective tissue (primary basement
membrane) between gi and olm; Je, epithelium of the intestine; bv, left ventral blood-
vessel. The outer longitudinal muscular layer is thinner, but at the same time much more
compact than it was in the section of fig. 2. The blood-vessel and its surroundings, as well
as the intestinal epithelium, are only represented diagrammatically.

Fig. 4. Hupolia giardii, n. sp. A transverse section through the dorso-median (medullary) nerve-
stem (dm). The nerve-tibres are transversely cut; the nuclei are distinct. /., the
nervous layer, continuous with the median stem; o/m, outer longitudinal muscular layer
with a considerable amount of gelatinous connective tissue (ct) between the separate
bundles,

Fig. 5. Eupolia giardii, n. sp. Portion of a transverse section through the body-wall (ef. Pl. VI.
fig. 9). Only asmall portion of the very thick circular muscular layer cm is here represented.
Lettering as in figs. 2 and 3. st, longitudinal nerve-stem; Wep, two radial ducts of the
nephridia leading outwards, one of them opening to the exterior at neo. The outer
longitudinal muscular layer is far from compact, the secretion of the sub-epithelial glands
gi can be traced piercing the layers, ef, B and ZL.

Fig. 6. Eupolia nipponensis, n.sp. The outer ciliated epithelium (#) and unicellular glands (“ Schleim-
stiibchenzellen ”) secreting their product (wg) to the exterior, supported by the basement
membrane B.

Fig. 7. Eupolia australis, n. sp. Longitudinal section in the posterior region of the body-wall, to show
the generative ducts (gd) leading from the generative sacs (gon) outwards and piercing the
muscular layers (‘Jm and cm) above the nerve-stem (JVs?).

Fig. 8. Hupolia giardii, n. sp. The sub-anal nervous commissures in a horizontal section. J, cavity
of intestine ; Je, epithelium of the same; iV, NV’, the right and left longitudinal nerve-stem
communicating by the transverse commissure ; Z, external epithelium,

Fig. 9. Eupolia delineata, n. sp. Longitudinal section through the body-wall. Lettering as in figs. 2
and 3. e/p, the external longitudinal and circular fibres that belong to the integument and
have the pigment between them.

Fig. 10. Hupolia delineata, n. sp. Section of the proboscidian sheath. Ps, the cavity of the sheath
lined by cells which are again encircled by a very attenuated circular layer ; 0/, blood-spaces
outside of the proboscidian sheath ; c¢s, strings of connective tissue by which the proboscidian
sheath is suspended to the body-wall.

Fig. 11. Eupolia nipponensis, n. sp. Transverse section through the nervous layer (V/). Nuclei are
found imbedded in the nerve-substance and fibrous nerve strings stretch out from it radially
at different points. o/m and cm, the muscular layers.

Fig. 12. Eupolia nipponensis, n. sp. The cesophageal wall, in transverse section. c.7. and i/m, mus-
cular layers of body-wall; bs, blood-space inside of these. The wall of the cesophagus is
constituted of an inner ciliated epithelium Je, a basement layer B, and a thick layer of
glandular cells Jim.

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PLATE VIII.

Figs. 1

Fig. 3.
Fig. 4.
Fig. 5.
Hig. 1 6:
Fig. 7.
Fig. 8.
Ibias “Yh
Fig. 10.
Fig. 11.
Fig. 12.
Fig. 13.

PLATE VIII.

Pterosoma plana, Less. After Lesson, supposed by Moseley to represent a species of Pelayo-

nemertes.
Fig. 1. Seen from above.
Fig. 2. Seen from below. :

Pelagonemertes rollestont, H.N. M. <A transverse section, supposed to be not quite vertical to
the longitudinal body axis, so that to the right one of the digestive, to the left one of the
generative ezeca was touched in the section. Hp, external epithelial layer; B, basement
membrane; LV, layer of longitudinal muscles; J, intestine and its branching diverticula;

longitudinal nerve-stem; 6/, two lateral blood-vessels; Gv, external opening of the
generative cecum; P.S.C, the cavity of the proboscidian sheath ; Ps, the wall of that
cavity. All the internal organs are surrounded by and imbedded in a wholly continuous
gelatinous ground substance, in which a few cells and numerous fibres can be detected,
and which has more e strongly imbibed the staining reagent in the immediate vicinity of
the different organs and tissues that traverse it.

Pelagonemertes rollestoni, H. N. M. <A horizontal aspect of the muscular layers of the body-
wall, from a preparation made of the fresh animal by Professor Moseley. /m, the
longitudinal muscles ; cm, the sparse circular muscular fibres, external to the foregoing ;
dr, granular patches, “eventually glandular structures; ct, the gelatinous connective tissue
visible between the muscle fibres.

Pelagonemertes rollestont, H. N. M.A transverse section of what most probably corresponds
to one of the granular patches of fic. 4, furnishing arguments for looking upon the latter
as glandular. A central lumen (or fibre’), with nuclei surrounding it can be detected.

Pelagonemertes vollestoni, H. N. M. The longitudinal nerve-stem JV, in transverse section.
A branch x gives off smaller nerve-twigs »’ and »”. Nuclei are imbedded in the fibrous
nerve substance. The gelatinous connective tissue is more deeply stained all round, and
at ff has a distinctly fibrous appearance.

Pelagonemertes rollestoni, H. N. M. ‘The posterior region of the proboscis, in transverse
section. //, the longitudinal muscular fibres, externally invested by a basement mem-
brane; #, the epithelium, of which no details could be made out.

Pelagonemertes rollestoni, H. N. M. An empty genital caecum, in transverse section. In
the lower narrower part the epithelium is high and very distinct and a couple of epi-
thelium-cells are becoming converted into ova, ov. NV, the nerve-stem; 0/, the blood-
vessel; Gc, the empty cavity; cfc, connective tissue cells in the gelatinous ground-
substance ; f, fibrous tracks in the same.

Pelagonemertes rollestont, H. N. M. Isolated transversely striated cells from the wall of the
cavity, Ge, in fig. 8.

Pelagonemertes rolleston’, H. N. M. A young ovum.

Pelagonemertes rollestoni, H. N. M. A larger ovum, surrounded by its follicle cells (cf.
fig. 3). No distinct nucleolus, but numerous chromatic granules inside the nucleus.

Pelagonemertes rollestont, H. N. M. Portion of the proboscidian sheath, in transverse section,
under higher power. , the inner homogeneous limiting membrane; /m, longitudinal ;
cm, circular muscular layer; cf, the outer sheet of the gelatinous tissue immediately
applied against the muscles and again more deeply stained.

Pelagonemertes. rollestont, H. N. M. Portion of the outer layers of the body-wall, under still
higher power. The external cellular epithelium has not been represented. B, the thick
basement membrane, below this epithelium, traversed radially by apparent glandular ducts
(cf. figs. 4, 5); B',a deeper portion of the same, less affected by the staining solution, and
carrying connective tissue cells; em, isolated circular, LM, thicker bundles of longitu-
dinal muscular fibres ; d7, probable glandular ducts in the gelatinous ground- -substance
penetrating through the muscles to the exterior.

The Voyage of HM S."Challenger’

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PLATE IX.

J+B8. Integument and basement membrane. Int. Intestine.
M. Body musculature. Gs. Genital sacs, in many cases not yet in open com-
Gt. Gelatinous tissue. munication with the exterior.
Prs. Proboscidian sheath. Prs.div. Lateral diverticula of proboscidian sheath.
IN. Lateral nerve-stem. br. Blood-vessel.

Figs. 1-6. Diagrams of different Hoplonemertea to elucidate (1) the relative extent of integument,

Ayer (fe
Fig. 8.
lute Bh
Fig. 10.
Fig 11.

muscular body-wall and internal gelatinous tissue ; (2) the situation of the genital glands
and their respective openings to the exterior.

Fig. 1. Drepanophorus lankesteri, n. sp. Middle of the body, diverticula of proboscidian
sheath included in the section.

bo

Fig. 2. Drepanophorus lankestert, n. sp. Towards the extremity of the tail, between two

pairs of diverticula of the proboscidian sheath.
Fig. 3. Amphiporus mariont, n. sp.

Fig. 4. Amphiporus moseleyt, n. sp. Numerous genital sacs, both dorsal and ventral,
contained in one transverse section.

Fig. 5. Drepanophorus serraticollis, Hubr.

Fig. 6. Drepanophorus serraticollis, Hubr. Ina further advanced stage of ripeness of
the genital products (with distinct genital openings to the exterior); the diver-
ticula of the proboscidian sheath not touched in this section. In all these
sections the longitudinal blood-vesseis are indicated, the median one below the
proboscidian sheath, the lateral ones close to the lateral nerve-stems. In
Amphiporus moseleyt the lateral nerve-stems are seen to lie above, in Drepano-
phorus, below the intestinal ceca.

Amphiporus moseleyi, n. sp. Diagram of a horizontal section through the body. The
intestine and its ceca are dark grey, the generative cca light grey. The latter are
seen to be very numerous and in no way regularly or metamerically arranged.

Amphiporus moseleyt, n. sp. A specimen with flattened ventral surface. Natural size. A
whitish line from the tip of the snout backwards along the lateral margin marks the exterior
openings of the lateral glands (cf. Pl. XV. figs. 11, 12).

Amphiporus moscleyi, n. sp. Head, seen from below. Longitudinal slit both for the
intestine and the proboscis ; terminal transverse sensory groove and lateral bent grooves
into which the cavity of the posterior brain lobe opens.

Drepanophorus lankestert, n. sp. Diagram of the principal features of the nervous system.
B, brain-lobes; p.Br, posterior brain-lobes (side organs) with their cavity opening to the
exterior at e.0; Ceph.ne, numerous cephalic nerves to the tip of the head, the eyes, &c.,
only a few of them are here indicated in outline ; Prn, nerves for innervation of the pro-
boscis (they are more numerous than is here indicated); Va, outline of vagus nerve
springing from the lower brain-lobes and running forwards towards the cesophagus. The
latter passes beneath the brain-lobes and their double commissure, but above the ladder
commissures (Comm), which metamerically unite the longitudinal nerve-stems (ZV) below
the intestine ; pe.ne, peripheral nerves springing from these nerve-stems.

Amphiporus moseleyi, n. sp. Stylet and accessory darts. A and 2d, 0’, the central stylet and
its two accessory sacs, in position ; /”, bases of two accessory darts, viewed laterally (figure
to the left), and perspectively (figure to the right).

The Voyage of HM.S."Challenger” , Nemertea. Pl. IX.

F Huth, Lith’ Edin?

Hubrecht et de Groot del

AMPHIPORUS. DREPANOPHORUS.

PLATE X.

PLATE X.

Fig. 1. Amphiporus marioni, n. sp. Part of a transverse section through the cesophageal region, indi-
cating the relative importance of the musculature with respect to the integument and the
gelatinous tissue. Prs, proboscidian sheath in contracted state, the outline only partly
worked up to show the interlacement of muscular fibres, the basement layer and the internal
epithelium ; dz, dorsal blood-vessel surrounded by gelatinous tissue, as is the proboscidian
sheath, and Qe, the esophagus with its cellular epithelium. Outside of this there is a layer
of darker fusiform bodies, which are most probably unicellular parasitic organisms. Gt, the
gelatinous tissue ; a, the longitudinal, 8, the circular muscular coat; at ne, a bundle of nerve-
fibres spreads between a and f after having traversed the musculature between two of the
larger bundles of a; B, thick basement membrane with only a few nuclei; J, integument ;
LN, longitudinal nerve: Nep, nephridial tubules; Wep.d, part of the communicating duct
of the nephridia with the exterior; znc, peculiar crystalloid inclosures of a greenish colour,
irregularly distributed in the gelatinous tissue.

Fig.

bo

Drepanophorus lankesteri, n. sp. Part of a section through the tailend. J, the integument, with
an outer layer of sense-cells and supporting cells; granular glands leading to the exterior, a
layer of nuclei and one of deep lying cells with fainter nuclei; B, basement membrane with
imbedded nuclei; a, the longitudinal, 8, the circular muscular layer; G#, the gelatinous
tissue with nuclei and cells inclosed, certain of these being on their way of transformation
into fibres; ZV, longitudinal nerve-stem.

Fig. 3. Amphiporus moseley7, n. sp. Horizontal section through the tip of the snout. Pr, proboscis
and its musculature passing into and being the direct continuation of a, the longitudinal
muscular layer; Pris, the proboscidian sheath: Sp.P7, muscular arrangement in the wall of
the rhynchodzeum constituting a sphincter; Ah, external opening of the rhynchodeum, which
is internally clothed by a layer of cells very gradually passing into the proboscidian epithelium,
and externally into J, the integument; B, basement membrane; 8, circular muscular layer,
obliquely cut; Gt, gelatinous tissue; Br, Br’, left and right brain-lobes ; H#, eyes; gis, lateral
glands, continued along both sides of the animal (ef. Pl. XV. figs. 11, 12).

Fig. 4. Drepanophorus lankester’, n. sp. Proboscidian sheath with diverticula (div.Prs). Prs.ep, epi-
thelium of the sheath, separated by folded basement tissue from the muscular wall.

Fig. 5. Drepanophorus serraticollis, Hubr. Proboscidian sheath with thicker muscular walls and thinner
walled diverticula (div. Prs.).

Fig. 6. Eupolia giardii, n. sp. The boundary line between integument and body musculature. Jdvl,
deeper layer of vacuolated cells of the integument; B, reduced and folded primary basement
membrane ; y.v/, outer longitudinal muscular layer with large vacuolated cells and rare muscle
fibres. The vacuolated cells have larger nuclei than those of the integument (cf. Pl. VII.
fig. 5).

Fig. 7. Cerebratulus sp. inc. (medullatus ?). Transverse section of medio-dorsal region. J, integument;
b, secondary basement membrane; y, outer, a, inner longitudinal, 8, circular muscular layer ;
Prs.ep, epithelium of the proboscidian sheath; PrsN, longitudinal nerve of proboscidian
sheath ; me, nervous layer with median medullary thickening.

Figs. 8,9. Cerebratulus macroren, n. sp. The proboscidian sheath wall and intestinal epithelium wholly
(fig. 9) and half (fig. 8) distended by the proboscis. dv, dorsal blood-vessel (in fig. 8 still
within the proboscidian sheath cavity); Prs.ep, the epithelium of the proboscidian sheath,
supported by a homogeneous membrane, }, and surrounded by muscular layers m.Prs. Ov.ep,
epithelium of the esophagus.

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Rubrecht et de Groot del

CEREBRATULUS

EUPOLIA.

DREPANOPHORUS.

AMPHIPORUS.

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PLATE. XI,
ZOOL. omar, EXP, —PART LIv.—1887,)—Hhh. :

PLATE XI.

Diagrammatic figures to illustrate the situation of the dorso-median medullary nerve, and at the same
time the arrangement of the different layers of the body-wall and their respective relation as to size, &e.

The twelve upper figures are supposed to be taken as transverse sections just above the proboscidian
sheath, and are on purpose all reduced to the same scale, by which process the relative importance
of the integumentary layer is clearly brought out.

The corresponding muscular layers are indicated by the same Greek letters—a is the most important
longitudinal one, common to all; £, the circular; y, the outer longitudinal ; 6 is a circular muscular
layer characteristic of the Carinellide (figs. 1, 2, 3, 6, 13, and 14); it here forms the dorsal wall of the
proboscidian sheath and at the same time it forms part of the body-wall in the anterior part of the
body ; in all the others it has become detached and has possibly developed into the outer wall of the
proboscidian sheath, and as such is not indicated in figs. 5, 7-12. J, stands for the integument ; B, for
the primary basement membrane separating this from the muscles ; , for the secondary basement layer.

The plexus and medullary nerve are indicated by a yellow tint.

Fig. 1. Carinina grata, n. sp.

Fig. 2. Carinina grata, n. sp. More posteriorly.

s

Fig. 3. Carinella.

Fig. 4. Carinella. Further back in the region where the proboscidian sheath does not extend.

Fig. 5. Cephalothrix.

Fig. 6. Carinoma armandi (M‘Int.), Oud. Here the proboscidian sheath nerve lies below the
medullary nerve and is thicker than the latter.

Fig. 7. Carinoma armandi (M‘Int.), Oud. Further backwards in the region where the pro-

boscidian sheath does not extend.
Fig. 8. Amphiporus or Drepanophorus.
In fies. 9-12 the proboscidian sheath nerve is indicated and is seen to be less conspicuous than in
oO
Carinoma.
Fig. 9. Cerebratulus corrugatus, M‘Int.

Fig. 10. Cerebratulus medullatus, n. sp. The deeper glandular layer of the integument has
fused with the outer layer of longitudinal muscles, and the primary basement mem-
brane has thus disappeared.

Fig. 11. Cerebratulus macroren, n. sp.
Fig. 12. Hupolia giardir, n. sp.
The figs. 13-17 have reference to transverse sections of the body-wall in the region of the lateral
nerve-stem.
Fig. 13. Carinella (for Carinina, ef. Pl. IIT. fig. 7).
Fig. 14. Carinoma armandi (M‘Int.), Oud.
Fig. 15. Cephalothrie.
Fig. 16. Cerebratulus.

Fig. 17. Amphiporus.

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PLATE XIl.

Cerebratulus macroren, n. sp. Transverse section through a part of the brain-lobes of the New
Zealand specimen. The medullary nerve (77) is still in connection with the brain-lobes (2/);
prs, the proboscis, passing between the nervous ring formed by the brain-lobes and their
commissures. Superiorly two bundles of longitudinal muscle-fibres are enclosed by the
brain-tissue.

Cerebratulus macroren, a. sp. Transverse section of the body-wall in the region of the lateral
nerve-stem (Japanese specimen). a.f.y, the three muscular layers, the latter with the deeper
integumentary glands embedded between the muscle-bundles (cf. Pl. XI. figs. 10, 11); p/, the
nerve plexus ; }, the secondary basement membrane with the thin layers of integumentary
muscles just below it; J, the cellular integument ; JV, the lateral nerve-stem, into the fibrous
core of which part of the fibres of the plexus may be seen to be interwoven.

Cerebratulus corrugatus, M‘Int. Transverse section of the medullary nerve (7) at a point
where a pair of transverse stems (cf. Pl. XIV. fig. 1) merge into it. m, these nerve-stems
(being thickened tracts in the plexus, pl); pf, nerve fibres radially emerging from these tracts
and having the significance of sensory or motor peripheral twigs ; “h, ‘radial fibres (not
nervous) piercing the plexus (cf. Pl. XIII. figs. 3, 4, xf).

Cerebratulus corrugatus, MUInt. Transverse section of the medullary nerve of another specimen.
Lettering as in the foregoing figure.

Drepanophorus lankesteri, n. sp. Transverse section of the lateral nerve stem (JV), with two
peripheral nerves, pf, springing from it. The fibres of the latter partly emerge from the
ganglion cells, partly from the fibrous core of the lateral stem.

Drepanophorus servaticollis, Huby. A portion of a transverse section through the proboscis. - 1.0’,
the longitudinal muscle-fibres, in two strata, between which les the nerve-plexus np, of
which /z is one of the longitudinal thickenings (nerve-stems) ; 0.c, the outer; 7.c, the inner
layer of circular fibres ; >, transparent basement tissue.

Cerebratulus macroven, n. sp. ‘Transverse section of the superior nervous connection between
the two brain-lobes (Japanese specimen). Nerve cellular elements predominate in this region
whence the medullary nerve is continued both backwards and forwards. 2, the homo-
geneous layer forming an investment to the nerve-tissue ; p's, the proboscidian sheath in
outline.

Cerebratulus macroren, n. sp. A few sections further backwards. The medullary nerve 7 is.
here more distinct, its anterior continuation m’ being on the point of coalescing with it.
Lettering as in fig. 7. pr, outline of the proboscis; Br, fibrous core of the brain-lobe.

Cerebratulus medullatus, n. sp. Transverse section of the medullary nerve (7). _p/, the plexus ;
B and a, the cireular and longitudinal muscular layers; (inner circular muscular fibres
are seen to form the outer layer ‘of the proboseidian sheath) ; pin, the proboscidian sheath
nerve, receiving delicate fibres from the medullary nerve and situated just above the pro-
boscidian sheath musculature,

Cerebratulus medullatus, vn. sp. Integument and muscular body wall. Lettering as in fig. 2.
dgl, the deeper glands of the integument enclosed in the musculature.

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PLATE XIII.

. Cerebratulus corrugatus, M‘Int. Transverse section through part of the superior brain-lobes and

dorsal brain commissure. Part of the fibrous core (h) is represented; its continuation into the
fibres of the commissure (f.co) being distinctly noticed on the left side. On the right this
connection is only visible a few sections further. The bulk of the brain-lobe is seen to con-
sist of nerve-cells of different sizes (7.c/); from these a cephalic nerve (cv) is seen to emerge
on the left, whereas this cellular coating is also continued over the commissure, and there
forms the starting point (m) for the longitudinal dorso-median medullary nerve.

. Cerebratulus corrugatus, MInt. Horizontal section of the same specimen through the medullary

nerve 7. In this section only a portion of the cylindrical nerve-plexus (np/), of which the
medullary nerve is only the median thickening, is visible. The transverse nerve-tracts tr.n,
paired and metamerical, being thicker than the plexus, are cut along a more considerable
surface and thus stand out as separate nerves. The openings in the plexus give passage
to radial, transverse, contractile fibres, as is specially indicated in fig. 4, rf.

Cerebratulus corrugatus, MInt. Portion of a horizontal section through the ventral extension of
the nerve-plexus, 7m, the nerve-tissue of the plexus with nuclei of nerve-cells, and bundles
of radial fibres rf. piercing it.

Cerebratulus corrugatus, MInt. Portion of the same section as fig. 2, more highly magnified.
n, the tissue of the nerve-plexus with delicate fibres and distinct nuclei of nerve-cells, also
visible in the medullary nerve m ; rf, the bundles of radial, contractile fibres.

. Cerebratulus corrugatus, MInt. Ventral view of the head and long mouth with rugose lips of

large specimen. Natural size.

Cerebratulus corrugatus, M‘Int. Radial strip out of a transverse section in the cesophageal region,
Jsq, the outer glandular layer of the integument (with “ Schleimstibchenzellen ”); 6, the
secondary basement membrane below this ; J/cm, the longitudinal and circular muscle-fibres
peculiar to the integument; Jdg, the deep glandular layer just below these; B, the
primary basement membrane of the integument radially traversed by contractile fibres
(rf) and nerve-bundles (7) going towards the integument; y, the outer longitudinal
muscles; p/, the nerve-plexus with fibres and cells, pierced by the radial contractile
bundles 7f; 8, the circular muscular layer; a, the inner longitudinal muscular layer; cos, the
circumcesophageal intercommunicating blood-lacun, clothed by a cellular endothelium ;
mto, the cesophageal musculature; nv, nerve-tissue in the cesophageal wall; pap, an
cesophageal papilla with deeper glandular and superficial ciliated cell-layers.

Figs. 7, 8. Cerebratulus macroren, n. sp. Two sections through the principal nephridial duct of a

specimen from Japan. Contracted (fig. 7) and distended (fig. 8).

Fig. 9. Cerebratulus macroren, n, sp. Anterior tubuliferous proliferation of the nephridia. a, 8, mus-

cular layers as in fig. 6; Nep, nephridian tubules applied against the wall of the circum-
cesophageal blood-lacuna ; Oe, outline of cesophagus wall.

‘

The Voyage of TH. M.S Challenger

Nemertea P] XIII

Lath DW. G, Groot. Utr.
Hubr. et de Gx. del.
_S CEREBRATULUS.

; PLATE XIV, a

Higoeal:
Fig. 2.
Fig. 3.
Fig. 4.
Fig. 5.
Fic. 6.
Figs. 7

Fig. 9.
Fig. 10.
Tite ltl

PLATE XIV.

Cerebratulus angusticeps, n. sp. The medullary nerve (7) and the transverse paired metamerical
nerve-stems (fn). Drawn with the camera. 1 mm. on the same scale is indicated on
the left of the figure.

Cerebratulus corrugatus, M‘Int. Transverse section of the lateral nerve-stem (/V) and body-wall.
a, B, y, the muscular layers ; B, the primary basement membrane, and J, the integument
in outline (cf. Pl. XIII. fig. 6); 7 radial fibres piercing the muscular layers; and pn,
nerve-tracts, of which one (pm) is seen to emerge directly from the lateral nerve-stem and
to innervate the sensory layers of the integument ; 2p/, nerve-plexus.

Cerebratulus corrugatus, M‘Int. Diagrammatic figure of a transverse section in the mouth-region
to show the innervation of the cesophagus and blood-lacune. Oe#, the cesophageal
epithelium; Ps, the proboscidian sheath ; co.l, the cireumcesophageal blood-lacuna. In
the nerve-plexus, which is indicated by a black line, m marks the medullary nerve, and
nl, the lateral nerve-stems ; vz.n, the visceral branches springing from the plexus; 7.va,
the vagus ramifications transversely cut and intermixed with the branches w7.n.

Cerebratulus corrugatus, M‘Int. Part of the same section as fig. 3, more considerably enlarged.
Lettering asin fig. 3; mpl, nerve-plexus ; rf, radial, not nervous fibres ; a.B.y, the muscular
layers ; ¢.o./, the blood-lacunz with cellular coating. The cesophageal epithelium (oe.Z)
is not represented in its whole thickness.

Cerebratulus parkeri, n. sp. Diagram, drawn with camera, of the inferior brain-lobes, Br, and
the vagus nerve (va) springing from them, the two stems being united by a series of trans-
verse commissures co close to their origin. The brain-lobes merge into the lateral nerve-
stem (V); the ventral metameric connections of the latter are indicated by dotted lines,
v.ty.n, those of the brain-lobes being lettered c.t7.n; Oe, outline of the csophageal
epithelium.

Cerebratulus angusticeps, n. sp. Horizontal section of the left upper and posterior brain-lobes
(Br and PBr); c.ol., cl, the free blood-lacuna between the brain, the proboscidian sheath,
and the cesophagus, the boundaries of these’two latter being only indicated by dark shading ;
a, 8, muscular layers ; ¢n, anterior portion of lateral nerve-stem, the ganglion cells of the
cellular investment being here cut; cc, the outwardly directed portion of the ciliated
canal inside the posterior brain-lobes ; cc’, ce”, the deeper portion of the same being cut
in two places, because of the S-shaped curve which this canal makes inside the brain-lobe.
The relatively large size of the posterior brain-lobe, and the preponderance of fibrous
nerve-tissue in the upper lobe, are indicated in this figure.

, 8. Cerebratulus macroren, n. sp. Two transverse sections (a few sections apart) through the

posterior brain-lobe and its investment of large granular glandular cells (g.c/). m, the
outer membranous investment of the lobe; m.c/, the ordinary ganglion cells with fibrous
core in the centre of the lobe; cc, the ciliated canal with an epithelium of its own, more
distinct in fig. 8 than in fig. 7.

Drepanophorus lankesteri, nu. sp. Part of a horizontal section through the upper brain-lobe, with
interior fibrous core (cf.) and outer layer of ganglion cells, m.c/ ; a few of which are much
larger (7C?).

Drepanophorus lankester?, n. sp. Part of a horizontal section through the posterior brain-lobe.
Bm, the outer investment of the lobe; z.cl, the nerve-cells ; cc, the ciliated canal with
its epithelium ; gel, the granular glandular cells ; the anterior ones pouring their contents
into the lumen of the ciliated canal.

Cerebratulus macroren, n. sp. Part of a transverse section through the head, showing the ciliated
canal to the posterior brain-lobe in its course from that lobe (P&r) to the exterior.
gel, the granular glandular cells; ec, the lumen of the canal, coated by an epithelium of
varied histological character as we pass outwards towards /, the external layer of the
integument. At gl. a sort of ring-shaped cushion of peculiar cells may be said to
embrace the canal (¢7., Pl. VI. figs. 1-3). Just behind this the epithelial cells are very
closely set and provided with elongated nuclei, further backwards they are seen to pass
without any sudden transition into those lining the canal, inside the brain-lobe.

The Voyage of H MS Challenger.
: Nemertea PL XIV

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PATE Xa.

1. Cerebratulus longifissus, n. sp. Transverse section through the proboscidian sheath. a, the
inner longitudinal muscular layer of the body wali; pr.sn, the proboscidian sheath nerve;
Pr.S, the lumen of the proboscidian sheath; e, its inner epithelial lining; 6, the homo-
geneous basement membrane of this epithelium, traversed by radial fibres and separatine
the aforesaid epithelium from the muscular layers (an inner longitudinal, and an outer
circular) of the proboscidian sheath; G?, the gelatinous tissue between the proboscidian
sheath, the intestine and the body wall; dv, the dorsal blood-vessel.

2. Cerebratulus macroren, n. sp. Transverse section of the proboscis. 0, the ensheathing mem-
brane ; a’ and y’, the two layers of longitudinal, f’, the layer of circular muscular fibres, the
latter connected crossways at two diametrically opposite points with the membrane / ; .pl, the
nerve-plexus between fp and y'; #, the very high inner epithelium with smaller (¢) and
larger (C) batteries of nematocysts.

Cerebratulus macroren, n. sp. Transverse section of the proboscis much further backwards ;
the proboscis is thinner, the muscular fibres (a) only longitudinal, the epithelium (/)
flattened, the nervous plexus replaced by two longitudinal nerve-stems JV.

. Cerebratulus angusticeps, n. sp. Head. a, from below; 0, side view.

Cerebratulus parkert, n. sp. Head. a, side view; b, from below. x 14.

Cerebratulus sp. inc. Two fragments from Japan. x 2. a, dorsal view; 0}, ventral view.

Cerebratulus sp. inc. Transverse section of one of the fragments of fig. 6. J, the integu-
ment; a, 8, and y, the much reduced muscular layers; iV, the lateral nerve-stems ; Znt, the
intestinal canal and czeca, suspended in the gelatinous ground tissue Gt; Gt’, the same tissue
expanded between the very sparse external fibres of the muscular layer y; PrS, the probos-
cidian sheath ; bv, the blood-vessels.

8. Cerebratulus sp. inc. Lateral view of the head of another specimen from Japan (Kobe).
9. Cerebratulus longifissus, n. sp. Longitudinal section of the tail end. JZ, the integument ;
Int, the intestinal epithelium ; a, f, y, the muscular layers ; mpl, the nerve plexus. This figure
is meant to show the general aspect of the muscular layer a, more highly magnified in fig. 10.
10. Cerebratulus longifissus, nu. sp. The muscle-fibres of the layer a are seen to present a more con-
siderable diameter in successive vertical planes, forming rings round the intestine and alternating
with others in which this increase in diameter is not visible. Nuclei are also more numerous
in the former portions than in the latter; Hp, the intestinal epithelium; G#, the gelatinous
tissue between this and the body musculature, with bundles of radial fibres.

11. Amphiporus moseleyi, n. sp. Transverse section of the lateral region with glandular cavities
(gl), arranged along the lateral line between the dorsal and ventral musculature a, piercing
the circular muscular layer B at e, and suspended by the gelatinous tissue gt. J, integu-
ment; B, basement membrane.

12. Amphiporus moseleyi, n. sp. One of the glandular caca, more considerably magnified, with

granular epithelium and flattened nuclei exteriorly, the latter belonging to the surrounding
gelatinous tissue.

a)

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13. Drepanophorus lankestert, n. sp. A section of similar glandular ceca in the dorso-median region
of the head.

x 14. Amphiporus marioni, n. sp. A very unripe generative cecum, not yet opening to the exterior.

f, Circular, a, longitudinal muscular layer. The cecum reaches down into the gelatinous
tissue, gt.

15. Amphiporus marioni, n. sp. Ova in different stages of development.
16. Cerebratulus parkeri, n. sp. An ovum.
17. Drepanophorus serraticollis, Huby. An ovum.

. 18. Cerebratulus sp. inc. A batch of ova from a ripe generative cecum of a specimen from Station

321. The ova are surrounded by a hyaline membrane (which has erroneously been dotted
by the lithographer) and pressed into polygonal shapes.

19. Cerebratulus macroren, n. sp. Part of a transverse section, in outline. rs, The cavity of the
proboscidian sheath ; Z, integument ; y, 8, the muscular layers ; NV, the longitudinal nerve-stem ;
ge.c, the generative caecum; 0, its exterior opening. The duct to this opening, where it
pierces the layer y, is considerably extended in bulk.

20. Amphiporus moseleyi, n. sp. A longitudinal section through the greater part of the compressed
«esophagus Oe, and subjacent intestinal caca (co).

The Vovage of [LMS Challenger Nemertea Pl. XV.

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PLATE XVI.

PLATE XVI.

Three diagrammatic figures for the comparison of the nerve system of the Nemertea, of the Vertebrata,
and of the Cephalochorda.

Fig. 1. The chief points in the nervous system of the Nemertea. /n, In’, the lateral nerve-stems with
their anterior swellings, the brain-lobes, Lg. The latter are connected in front by a
strong ring-shaped commissure, the former by much thinner but unmistakable
commissures, dvr, metamerically placed both dorsally and ventrally in a continuous
plexus of nerve-tissue, that ensheathes the body. This plexus is no further indicated in
the figure. It moreover carries a longitudinal medio-dorsal nerve-tract m, which is
also continued forwards, in front of the brain commissure, with which it is connected.
Into this medullary nerve m the transverse tracts dvr converge. From the latter (sensu
strictiort from the plexus) radial nerve twigs of sensory and motor significance can be
traced both in centripetal and in centrifugal direction, but these are not indicated in the
ficure. Other similar nerve twigs, indicated by v7.sy, innervate in a similar way the
wall of the cesophagus and of the blood-lacuna surrounding it (cf Pl. XIV. figs. 3, 4).
The innervation of the cesophageal wall is, moreover, brought about by a paired nerve,
v, springing from the brain-lobes, and not strictly separate in its peripheral distribution
from that of the nerves v7.sy. en, nerves to the tip of the head; 1, mouth.

Fig. 2. The chief points in the nervous system of the Vertebrata.

Instead of the medullary nerve we find here in the corresponding situation the
medulla spinalis m and its anterior enlargement, the brain. The spinal nerves are
represented in their primitive condition, 7.¢., with the dorsal (sensory) roots dr, and the
ventral (motor) roots vr, not yet connected into a spinal nerve of higher order.
Anteriorly is represented the union of more than one metameric transverse root into a
complex polymerous vagus nerve, Vay, motor and sensory branches of which are
represented as innervating the branchial pouches of the fore gut (the latter not specially
indicated in the figure). From the vagus ganglion also springs /z, the ramus lateralis
nervi vagi or nervus lateralis ; Iv’, the left nervus lateralis. This nerve is continued
forwards into other ganglionic swellings Ly, representing the series of ganglia of the
cephalic nerves. The visceral branches springing from the dorsal roots and inner-
vating vegetative organs are indicated by v7.sy ; they are supposed not yet to have united
into a longitudinal ‘‘sympathetic nerve.” In front the region innervated by them
overlaps and fuses with that of the intestinal branch v. of the vagus, and of other
cephalic nerves. J, mouth.

Fig. 3. The chief points in the nervous system of Amphiowus.
The medulla spinalis 7 without any considerable anterior enlargement ; en, pairs of
cephalic nerves; d7, dorsal roots; wr, ventral roots; the former springing from the
medulla at a higher level than the latter. The dorsal roots are connected together in a
plexiform arrangement ; they give off visceral branches (v7.sy). M, mouth.

The Voyage of HMS. Challenger,

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THE

VOYAGE OF H.M.S. CHALLENGER.

ZOOLOGY.

REPORT on the Cumacea collected by H.M.S. Challenger during the years
1873-76. By Professor G. O. Sars, of the University of Christiania.

INTRODUCTION.

THE Cumacea obtained during the voyage of H.M.S. Challenger form a comparatively
small part of the rich collection of Crustacea procured during the Expedition, the
number of species amounting to only fifteen. They belong, however, to eight different
genera, and thus most of the leading types of this interesting group are in reality found
to be represented in the collection. The specimens were, as a rule, preserved in the
usual manner in strong spirits; but a few forms had been immediately mounted in
Canada balsam on glass slides, and the examination of these could not, of course, be so
satisfactorily made as in the case of the others. Four of the species were detected by
myself in examining some small samples of dredged material kindly sent to me by
Mr. John Murray.

The specimens were collected partly in the Atlantic, partly in the Pacific, and partly
in the Southern Ocean, especially at Kerguelen Island, where no less than five of the
species were procured. The greatest depth from which Cumacea were procured was at
Station 246, in the North Pacific (2050 fathoms), and the least depth at Flinders
Passage (7 fathoms). Two of the species were, moreover, taken at the very surface of the
sea, off Samboangan, Philippine Islands.

In describing the species I have made use of the terminology adopted in my Report
on the Schizopoda of the Challenger collection,' and have endeavoured to give a more
detailed account of such forms as represent separate groups or families of the order.

1 Zool. Chall. Exp., vol. xiii. pt. xxxvii. p. 3.
(ZOOL. CHALL. EXP.—ParT LY.—1886.) li 1

2 THE VOYAGE OF H.M.S. CHALLENGER.

The eight genera represented in the collection may be referred to seven different
families, viz., Cumide, Vaunthompsoniide, Lampropide, Leuconide, Diastylide, Cumel-
lid and Campylaspide, all of which are also represented in the Northern Ocean. Of
the fifteen species contained in the collection, one only, Diastylis stygia, has been
previously described ; all the others I regard as new, although some of them seem to be

very nearly related to earlier known species.

PrincipaL WoRKS oN CUMACEA.

Kroyer, H., Fire nye Arter af Slegten Cuma. Nat. Hist. Tidsskr., Bd. ii, 1841.

Om Cumaernes Familie. Wat. Hist. Tidsskr.. Ny Rekke, Bd. ii., 1846.

Goonpsir, H., Description of the Genus Cuma and of two New Genera nearly allied to it. Edin. New Phil.
Journ., 1843.

Spence Bare, On the British Diastylide. Ann. and Mag. Nat. Hist., vol. xvii, 1856.

Benepes, P. J. v., Recherches sur la faune littorale du Belgique—Crustacés. Mém. Acad. Sci. Bruzelles,
t xxxiii, 1861.

Sars, G. O., Om den aberrante Krebsdyrgruppe Cumacea og dens nordiske Arter. Forhandl. Vidensk. Selsk.
Christiana, 1864. ;

Beskrivelse af de paa Fregatien Josephine’s Expedition fundne Cumaceer. K. Svensk. Vetensk, Akad.

Handl., Ba. ix., 1871.

Beskrivelse af syv nye Cumaceer fra Vestindien og det Sydatlantiske Hav. K. Svensk. Vetensk.

Akad. Handi., Bd. x1, 1873.

Middelhaveis Cumaceer. Archi 7. Mathem. og Naturvid., vols. iii, iv., 1878-79.

Doxey, A., Ueber den Bau und die Entwickelung der Cumaceen. Zeitschr. d. gesammt. Naturwiss., Bd. v.,
1870.

Norway, A. M., Crustacea Cumacea of the “Lightning,” “Porcupine,” and “ Valorous” Expeditions. Azz.
and Mag. Nat. Hist., ser. 5, vol. iL, 1879.

Boas, J. E. V., Studien iiber die Verwandtschafisbeziehungen der Malacostraken. Morphol. Jahrb, Bd. viii.,
1883.

MORPHOLOGY OF THE CUMACEA.

The morphological relationship of the Cumacea to the other groups of Crustacea is
rather obscure, and hence their systematic position has been much disputed. At first
they were even considered by some of the greatest authorities, as Milne-Edwards, Dana,
and L. Agassiz, as merely larval forms of higher Crustacea. Both Kroyer and Goodsir,
however, clearly showed them to be adult animals, and thus it was necessary to range
them within the carcinological system. These two authors regarded them as lower forms
of Macrura, whereas Dohrn and others seem to be more inclined to associate them with
the Edriophthalmia (Isopoda). 1 think their affinity to either of these groups is so very
slight as to justify the establishment of a distinct order for their reception. More
recently, Dr. Boas has discussed the affinity of the different groups of the Malacostraca
from a phylogenetic point of view, and has been led to the conclusion that the Cumacea
are very nearly related to the Mysidz, and may have descended directly from this group
of Schizopoda. With this view I cannot, however, fully agree. It is undoubiedly a
matter of great difficulty, if not quite impossible, to arrange the recent groups of
Crustacea in a genealogical manner, as most of them in all probability represent very
diverging branches, the origin of which from one or a few ancestral forms may go back
to a very remote period of geological time. The Cumacea would seem to represent such
an isolated branch, and cannot, of course, in my opinion, strictly be derived from any of
the recent groups.

As to the external appearance of these peculiar Crustacea, one would perhaps be most
inclined to associate them with the Podophthalmia, but on closer examination we find
them to differ materially in many points, and even in that important character from
which the name of the above-mentioned group has been derived. The anatomical details
present, on the whole, a peculiar mixture of the podophthalmous and edriophthalmous type.
and the development is rather unlike that of the Podophthalmia, and evidently much
more similar to that of the Isopoda. The oral parts, which are generally regarded as
affording highly important characters, I find—in contradiction to the opinion of Dr. Boas
—very different from those in the Myside, and on the whole constructed on the same
general type as in the Isopoda. On the other hand, the presence of well-developed

4 THE VOYAGE OF H.M.S. CHALLENGER.

natatory exopodites on a certain number of the limbs would seem to remove these
Crustacea far from the Isopoda, and to bring them in closer approximation to the
Schizopoda, but this character is, perhaps, the only one pointing to a genetic connec-
tion between these two groups. In all other respects I find the difference so very
great as quite to forbid the adoption of the view of a direct descent of the one from the
other. In some characters the Cumacea would seem to occupy a still more primitive
position than even the Mysidz. Thus, in the development of the higher Crustacea we
find the Cumacean type, as it were, imitated by the early stage preceding the Mysis-stage,
and to which the name of Zoea has been applied, the tail being in this stage, as in the
Cumacea, very mobile and slender, and at first without any trace of ventral limbs, and the
natatory exopodites confined to the anterior limbs only. Moreover, the general form of
the body in the Cumacea, and especially that of the tail, strongly remind us of that
ancient group to which Mr. Packard has given the name of Phyllocarida, and of which the
recent genus Nebalia is regarded as a direct descendant. True, the limbs in the Cumacea
are very different from those in Nebalia, but it is by no means proved that the limbs in
all of the ancient Phyllocarida were of exactly the same structure as in the recent genus
Nebalia. It has been generally admitted that the phyllopodous form of the limbs is
the most primitive one in Crustacea, and that all other forms might be derived from
this type. But the legs in the oldest of all known Crustacea, the Trilobita, have
been stated by Mr. Walcott to exhibit a totally different form, and this fact does
not seem to corroborate the general validity of the above supposition. The structure of
the branchial apparatus in the Cumacea is very remarkable and quite unlike all that is
observed in other Crustacea. It is true that the part to which the gills are affixed
represents the epipodite of the maxillipeds, and that this part is also found in the
Myside, but here it always constitutes a simple membranous plate without any trace of
gills, and may be assumed only indirectly to subserve a respiratory function. As is well
known, we also find the same part peculiarly developed for respiratory purposes in the
cheliferous Isopoda, but even here without any trace of gills. The antenne in the
Cumacea are totally different in structure from those in the Mysidee or any other form of
the Podophthalmia, whereas they exhibit, especially as regards their peculiar modification
in the males, a certain similarity to those in Nebalia, as also to those in the
Amphipoda.

In conclusion, I am inclined to regard the Cumacea as representing the descendants
of a very ancient form, long ago extinct, which may have combined some characters
of both the Phyllocarida and Trilobita. Perhaps even some of the palseozoic forms
placed among the Phyllocarida may have formed a direct transition to the Cumacean
type.

REPORT ON THE CUMACEA. 5

DEFINITION OF THE FAMILIES.

All the known families, except one, the Pseudocumide, being represented in the
Challenger collection, I have found it advisable to give here short diagnoses of the
same, and to enumerate the several genera contained in each of them. It may be
remarked that these families do not seem to have strictly the same systematic value as
those of the Schizopoda characterised in my former Report. The latter should perhaps
more properly be regarded as groups of a higher rank, or as sections.

1. Cumip&.

Integuments generally strong, calcareous. Tail not sharply defined from the trunk ;
in female very slender, cylindrical ; in male much stronger, and with distinct epimeral
plates. Hye generally present. Antennulz very small, with one of the flagella
rudimentary. Antenne in male with posterior part of peduncle distinctly biarticulate,
flagellum filiform and composed of numerous short articulations. Mandibles well
developed, with the anterior branch produced and armed with a dense lateral series of
spines. Epipodite of maxillipeds very large, navicular; gill-lobules numerous, leaf-like,
arranged in a straight series ; terminal plate of exopodite scale-like and strongly indurated.
Second pair of gnathopoda rather large, with some of the joimts expanded and laminar.
The four posterior pairs of legs in both sexes simple, without any trace of exopodites.
Five pais of well-developed pleopoda present in male. Uropoda with both branches
biarticulate, or the inner uniarticulate. Telson quite wanting,

Genera.
1. Cuma, Milne-Edwards. 4, Iphinoé, Sp. Bate.
2. Cyclaspis, G. O. Sars. 5. Cumopsis, G. O. Sars.
3. Stephanomma, G. O. Sars.

2. VAUNTHOMPSONIID.

Integuments thin, squamous. General form of body, antennule and mandibles much
as in the Cumidz. Hye present or wanting. Antenne in male with flagellum composed
of very elongate and slender articulations. Epipodite of maxillipeds (in female) very
narrow, with only few and digitiform gill-lobules arranged in a semicircle; terminal
plate of exopodite membranous. Second pair of gnathopoda with the joints scarcely
expanded. The three anterior pairs of legs in female, and all but the last in male

6 THE VOYAGE OF H.M.S. CHALLENGER.

provided with well-developed natatory exopodites. Five pairs of pleopoda present
in male, as in the Cumide. Uropoda with both branches biarticulate. Telson
wanting.

Genera.

1 Vaunthompsonia, Sp. Bate. | 2. Leptocuma, G. O. Sars,

3. LAMPROPIDA.

Integuments thin, squamous. Form of body generally very slender; tail in both
sexes cylindrical, without any epimeral plates. Eye present or wanting. Antennule
with both flagella well developed and nearly equal. Antenne in male with flagellum
composed of numerous short articulations. Mandibles well developed. Epipodite of
maxillipeds comparatively short, with but few, digitiform gill-lobules ; terminal plate
of exopodite only slightly indurated. Second pair of gnathopoda rather slender, pedi-
form. The two anterior pairs or only the first pair of legs in female, and all but the last
in male, with well-developed natatory exopodites. Only three pairs of pleopoda present
in male, or all wanting as in female. Uropoda with the branches very slender, inner tri-
articulate, outer biarticulate. Telson distinctly defined, more or less laminar, with three
or more terminal spines.

Genera.
1. Lamprops, G. O. Sars. 4. Platyaspis, G. O. Sars.
2. Hemilamprops, G. O. Sars. 5. Chalarostylis, Norman.
3. Paralamprops, n. gen.

4, LEUCONID.

Integuments very thin and pellucid, smooth. Form of body generally slender, with
tail very elongate and mobile, not sharply defined from trunk. Eye always quite
wanting. Antennulee with one of the flagella small, uniarticulate. Antennze in male
with flagellum composed of numerous short articulations. Mandibles rather small, with
the body exserted into two angular processes ; anterior branch short, wanting the usual
series of lateral spines, molar tubercle very massive. Palp of first pair of maxilla with
a single terminal bristle. Epipodite of maxillipeds comparatively small, with but few
digitiform gill-lobules ; terminal plate of exopodite membranous, exserted into a narrow
flap. Second pair of gnathopoda rather short, with some of the bristles issuing from the
outer edge very strongly developed. The three anterior pairs of legs in female, and all
but the last in male, with well-developed natatory exopodites. Second pair of legs only

REPORT ON THE CUMACEA. ‘

sex-articulate. Only two pairs of pleopoda present in male. Uropoda with both
branches biarticulate and somewhat complanate, inner spinous, outer setose. Telson
wanting.

Genera.

1. Leucon, Kroyer. 3. Eudorellopsis, G. O. Sars.
2. Eudorella, Norman.

5. DIASTYLID2.

Integuments generally strongly indurated and often armed with spines. Anterior
division of body more or less dilated and sharply defined from tail, which is very slender
and mobile. Carapace large and vaulted, with a more or less conspicuous rostriform
projection in front. Eye present or wanting. Antennulze more or less dissimilar in the
two sexes, rather slender, with the flagella unequal, the smaller one (in female) tri-
articulate. Antenne in female forming a simple cylindrical stem divided into distinct
articulations, in male more or less elongated. Mandibles well developed, anterior branch
with a dense series of lateral spines. Epipodite of maxillipeds rather large, gill-lobules
arranged in a more or less distinctly spiral manner; terminal plate of exopodite
membranous, triangular. Second pair of gnathopoda with basal joint very large and
curved. The two anterior pairs of legs in female, and all but the last in male, with well-
developed natatory exopodites. Only two pairs of pleopoda present in male, the
posterior pair sometimes imperfectly developed. Uropoda very slender and elongate,
outer branch biarticulate, inner bi- or triarticulate and spinous at inner edge. Telson
distinctly defined, with the outer part generally narrowed and spinous at the edges, apex
with two spines only.

Genera

1. Diastylis, Say. | 2. Leptostylis, G. O. Sars.

6. PSEUDOCUMID.

Integuments generally thin and squamous. Tail more or less sharply defined from
the trunk. Eye present or wanting. Antennule small, with one of the flagella rudi-
mentary. Antenne in male with outer part of peduncle indistinctly biarticulate,
flagellum composed of rather elongate and slender articulations. Mandibles not very
strong, anterior branch with but few lateral spines. Epipodite of maxillipeds with only
slight traces of gill-lobules, terminal plate of exopodite scarcely indurated. The two

8 THE VOYAGE OF H.M.S. CHALLNGER.

anterior pairs of legs in female and all but the last in male with well-developed
natatory exopodites. Only a single pair of pleopoda present in male. Uropoda com-
paratively short, with the branches lanceolate, outer biarticulate, inner uniarticulate.
Telson distinctly defined, but extremely small, rounded at the tip and unarmed.

Genera.

1. Pseudocuma, G. O. Sars. | 2. Petalomera, G. O. Sars.

7. CUMELLIDZ.

Integuments more or less indurated. Tail very slender and rather sharply defined
from the trunk. Eye single or double, in male much larger than in female. Antennulee
quite similar in both sexes, flagella very unequal, the smaller one uni- or biarticulate.
Antenne in male with outer part of peduncle distinctly biarticulate, flagellum composed
of rather elongate and slender articulations. Mandibles with the anterior branch
slender and slightly dilated at the extremity, lateral spines few in number. Epipodite
of maxillipeds with the gill-lobules in female very slightly developed, terminal plate of
exopodite exserted into a narrow tubular flap. Second pair of gnathopoda with the
terminal part irregularly flexuous. The two anterior pairs of legs in female, and all but
the last in male, with well-developed natatory exopodites. The three posterior pairs of
legs extremely slender and terminating in a distinct claw. Pleopoda quite wanting
in both sexes. Uropoda with outer branch biarticulate, inner uniarticulate. Telson

wanting.
Genera.

1. Cumella, G. O. Sars. 3. Spencebatea, Norman.
2. Nannastacus, Sp. Bate.

8. CAMPYLASPIDA.

Integuments strongly indurated and calcareous. Carapace enormously developed
and highly vaulted in its hinder part. Tail comparatively short, with the segments
somewhat depressed. Eye generally present. Antennulz similar in both sexes, with one
of the flagella obsolete. Antenne in male with the flagellum filiform and composed of
elongate and slender articulations. Mandibles slender, with apex obliquely truncate and
dentate, molar process very narrow, styliform. First pair of maxilla unusually large,
with the masticatory lobes strongly spinous; second pair poorly developed, forming
simple, small, membranous plates. Maxilhpeds imperfectly developed, terminal part

REPORT ON THE CUMACEA, 9

obsolete; epipodite narrow, with digitiform gill-lobules arranged in a_ semicircle ;
terminal plate of exopodite membranous and exserted into a narrow flap. First pair of
gnathopoda rather strong, with penultimate joint greatly swollen. Second pair pediform,
only slightly differing from first pair of legs. The two anterior pairs of legs in female,
and all but the last in male, with well-developed natatory exopodites. Pleopoda quite
wanting in both sexes. Uropoda with the scape elongate, outer branch biarticulate, inner
uniarticulate. Telson wanting.

Genus.

Campylaspis, G. O. Sars. '

LIST OF THE SPECIES.

The following is a list of the species of Cumacea procured during the Challenger
Expedition :—

CuMID. DIASTYLID#.
1. Cyclaspis australis, n. sp. 9. Diastylis stygia, G. O. Sars.
2. ” pusilla, n. sp. 10, Pr horrida, n. sp.
3 » exsculpta, D. sp. ING 7 ertnaceus, N. Sp.
12. ° mystacina, N. sp.

VAUNTHOMPSONIID.

a=

Vaunthompsonia meridionalis, n. sp.
CUMELLID.
Lampropip#.

7; aie ‘4
5. Paralamprops serrato-costata, n. gen. et sp. 13. Nannastacus suhmit, n. sp.

LEUCONID”,
6. Leucon assimitis, n. sp. CaMPYLASPID,
7. 4, tenuirostris, n. sp. 14. Campylaspis pacifica, n. sp.
8. Hudorella abyssi, n. sp. 15. 7 nodulosa, n. sp.

(Z00L. CHALL. EXP.—PART Ly.—1886.) li 2

7 fn ; mM) tall is
ar | ; ih _ a

aint |

pits om = tis
: a

DESCRIPTION OF GENERA AND SPECIES.

Order CUMACEA.

Family L. Commz.

The most characteristic feature of this family is the total want, in both sexes, of
exopodites on the four posterior pairs of legs, a character not found in any other known
group of Cumacea. These legs also exhibit a very simple structure, and possess only a
scanty supply of bristles. On the other hand, the males are distinguished by the
presence of five pairs of well-developed pleopoda, and there is only one other family,
Vaunthompsoniide, which agrees with the Cumidz in this respect, whereas the males of
all other known Cumacea either have a less number of these limbs, or want pleopoda
altogether, as in the females. As a character peculiar to this family may also be
mentioned the highly indurated and strong integumenis, the full development of the
branchial apparatus, and the total want of a telson.

Of the five genera comprised within this family, only the genus Cyclaspis is repre-
sented in the Challenger collection.

Cyclaspis, G. O. Sars, 1864.
Cyclaspis, G. O. Sars, Om den aberrante Krebsdyrgruppe Cumacea og dens nordiske Arier, p. 81.

Generic Characters.—Carapace large and swollen, almost globular, with the dorsal
line strongly curved, and the pseudorostral projection very slight; a distinct notch on
each side anteriorly beneath the latter projection. Ocular lobe more or less produced,
and usually having at its end a distinct eye. Only four segments of the trunk exposed
behind the carapace, the anterior rather large, the three others suddenly much narrower,
and scarcely broader than the caudal segments. Tail very slender and elongate, last
segment obtusely produced at the tip. Antennule with one of the flagella very small,
knob-shaped, the other biarticulate, and bearing two long sensory appendages at the
extremity. Posterior lip with the lateral lobes armed at the tip with strong teeth.

12 THE VOYAGE OF H.M.S. CHALLENGER.

Second pair of gnathopoda strongly developed, the basal and meral joints expanded
exteriorly at the end into lamellar processes. First pair of legs with the basal joint
highly indurated and expanded in the middle, terminal part very slender. Second pair
unusually short, with the coxal joint broad and lamellar, terminal joint spinulose at the
edges. Uropoda comparatively short, with both branches lanceolate, outer biarticulate,
inner uniarticulate.

Remarks.—The present genus is nearly allied to Cuma, Milne Edwards, from which
genus it is chiefly distinguished by the great development and peculiar form of the
carapace, as also by a rather different structure of the uropoda. The genus was founded
upon a peculiar deep-sea form, Cyclaspis longicaudata, obtained by the author off the
Norwegian coast, and since also met with in the great depths of the Atlantic. In this
form the eye is totally wanting, but in all other respects it closely agrees with the species
here described. Another form, Cyclaspis cornigera, described by the author from the
Mediterranean, would seem to differ much more from the typical species, and may
perhaps be regarded as the type of a separate genus. No other species of the genus has
hitherto been known. In the Challenger collection no less than three different species
are represented, and will be described below. They may be easily distinguished by the
sculpture of the carapace, as follows :—

{ somewhat gibbous in the hinder part and provided on each side

with a slight transverse keel, and another obliquely longitudinal,
joining each other in about the middle part of the carapace, . Cyelaspis australis, n. sp.

Carapace quite glabrous and with the dorsal line evenly arcuate, . . Cyelaspis pusilla, n. sp.
very gibbous and highly sculptured by strong keels, both trans-

verse and longitudinal, limiting several deeply excavated areas
| oneach side, . c : : : : . Cyclaspis exsculpta, n. sp.

1. Cyclaspis australis, n. sp. (PI. I. figs. 1-20).

Specific Characters.—Carapace slightly compressed, keeled dorsally and somewhat
gibbous in the posterior part, with a slight curved prominence passing down the sides
and joining an obliquely longitudinal ridge above, which limits the gastric region.
Ocular lobe narrow and produced to the tip of the pseudorostral projection, its outer
part swollen and provided with well-marked lenses and pigment. Tail distinctly keeled
along the middle line, the three anterior segments, as also the two posterior segments of
the trunk with a subdorsal keel on each side of the middle one. First pair of legs
with terminal part shorter than basal, the three outer joints nearly equal in length;
second pair shorter than third, last joint armed with six spines. Inner branch of
uropoda about as long as scape, finely serrate along the inner edge, outer branch a little
longer. Length, 10 mm.

REPORT ON THE CUMACEA. 13

Remarks.—This species may easily be distinguished from the typical form, Cyclaspis
longicaudata, by the less tumid carapace and the sculpture of the same as well as that of
the tail. The ocular lobe has, moreover, at the end distinctly developed visual elements,
whereas in the typical species the eye is quite wanting, and the ocular lobe very short
and rounded. ‘The species is also very different from the Mediterranean form, Cyclaspis
cornigera.

Description.—I have been able to examine several specimens of this form, both
males and females, but none of them seem to be quite full-grown. The largest
specimen, represented on Pl. I. figs. 1, 2, is a young male. The length of this
specimen is 10 mm., whereas that of the largest female specimen (fig. 3) is only
8 mm.

The form of the body in both sexes (see Pl. I. figs. 1-3) is very slender, with the
anterior part, as in the typical form, suddenly and markedly dilated, almost club-shaped.

The carapace is large and deep, though somewhat more compressed than in the
typical species, its thickness being rather less than its height (compare figs. 1, 2). It is
somewhat gibbous in its posterior part, the strongest dorsal curvature lying rather behind
the middle, from which point the dorsal line declines almost in a straight line towards
the pseudorostral projection. The latter, to which generally the very improper term of
“rostrum” has been applied, is quite short and obtusely truncate at the tip, and, as
usual, is chiefly composed of the antero-lateral lobes of the carapace projecting in front of
the antennal segment. Immediately beneath this projection there occurs on each side a
distinct notch, limited by a short projecting angle, from which a short elevated ridge
runs backwards over the carapace. The inferior edges of the carapace are evenly curved
and join the posterior margin at an obtuse angle. On each side of the carapace, somewhat
posterior to the middle, a slight crescent-shaped prominence is seen running transversely
down the sides to the inferior edge. Above, this prominence joins an obliquely
longitudinal ridge, that begins at the most elevated part of the carapace, limiting
posteriorly the gastric region, and disappears at the sides of that area ; between this ridge
and the above-mentioned short lateral keel in one of the specimens (fig. 1), a somewhat
irregular forked prominence occurs, joing both in the anterior part of the carapace.
The gastric area (see fig. 2) exhibits, as usual, a somewhat bell-shaped form, and is limited
to each side by a distinctly marked fissure. From the extremity of this area the ocular
lobe is seen projecting. This lobe exhibits a rather peculiar appearance, being continued
along the whole upper side of the pseudorostral projection to its very tip; it is (fig. 4)
almost cylindrical and slightly swollen at the extremity, where an assemblage of
distinctly marked and regularly arranged lenses or cornea-facets occurs, as also interiorly
a dark pigment.

Only four segments of the trunk are found to be exposed behind the carapace. Of
these, the first is firmly connected with the carapace and almost of the same height as

14 THE VOYAGE OF H.M.S. CHALLENGER.

that part, whereas the three others become suddenly much lower and scarcely at all
broader than the caudal segments. These hinder segments of the trunk are moreover
very movably connected with each other, flexible membranous spaces being interposed
both above and below. Besides a median dorsal keel, also continued on the carapace,
these segments exhibit on each side of that keel another running along the dorsal surface
(see fig. 2). The epimera of the first segment are somewhat expanded and truncated at
the tip; those of the three posterior segments are narrowly rounded,

The tail, especially in female specimens (fig. 3), is extremely slender, even somewhat
longer than the anterior division of the body, and of a narrow cylindrical form. It has
a distinct median dorsal keel running along all the segments, and, besides, the two
anterior segments exhibit on each side of the median another subdorsal keel, as on the
posterior segments of the trunk. Laterally each of the five anterior caudal segments is
provided at the anterior margin with a small knob-like process that fits into a corre-
sponding notch in the posterior margin of the preceding segment when the tail is fully
extended. As to the relative size of the seements, they slightly increase in length
posteriorly to the penultimate, which is much longer than any of the others. The last
seement is somewhat shorter, and produced at the end as an obtusely rounded protuberance
(see fig. 20).

The integuments are highly indurated and calcareous, showing under the microscope
partly a granular, partly a squamous or densely reticulate structure.

The colour of the preserved specimens is light brown with darker shadings, especially
on the anterior part of the carapace.

The antennule (fig. 5, a') are attached close together beneath the pseudorostral pro-
jection, being partly concealed by that prominence, their outer part, however, projecting
freely from the anterior notches of the carapace. They consist each of a triarticulate
peduncle and two very short flagella. The first joint of the peduncle is rather large and
highly indurated ; it is turned obliquely outwards and has the outer edge finely ciliated,
the inner, close to the end, is provided with a few short bristles. The two-succeeding
joints of the peduncle are much smaller, and taken together scarcely as long as the basal.
The second joint has at the end on the inner side a bunch of three auditory sete, and
exteriorly a small simple bristle; the last joint is provided with a single auditory seta
(see fig. 6). Of the flagella, the one is quite rudimentary, only consisting of a small knob-
like joint bearing a very minute auditory seta and two simple bristles. The other flagellum
is about as long as the last joint of the peduncle and biarticulate, the terminal joint being
the smaller, and bearing at the tip two very long and regularly segmented sensory
appendages, besides two simple bristles, one of which is rather long. The latter flagellum
must undoubtedly be regarded as homologous with the outer flagellum in other Crustacea,
since it bears the sensory appendages, but the antennula is generally twisted in such a
manner that it in reality lies inside the other (see fig. 5).

REPORT ON THE CUMACEA. 15

The antenne (fig. 5, a”), originating immediately behind the antennule, are, as usual,
quite rudimentary in the female, only consisting of a broad lamellar basal part and a
very small conical terminal segment, the latter representing the rudiment of the flagellum.
The basal part is highly indurated, and bears on the inner (or upper) edge two very
strong and densely ciliated setae; the terminal segment, which is connected to the basal
at an obtuse angle, is tipped by a bunch of very minute auditory sete. In the young
male the antennze show an appearance quite similar to that described further on in the
male of Paralamprops serrato-costata, and lie folded beneath the lateral parts of the
carapace, so as not to be visible in the lateral aspect of the animal.

The anterior lip (fig. 5,1) forms a comparatively small rounded lobe, projecting
immediately behind the antennal segment. It is slightly emarginate at the free posterior
édge, and finely ciliated within the emargination.

The posterior lip (fig. 7), on the other hand, is rather large and quite membranous in
structure. It consists of two somewhat subtriangular lobes, connected at the base, and
terminating in a slightly inflexed angle armed with three strong compressed teeth. The
lobes are, moreover, densely ciliated along their inner edge, as also at the outer part of
the exterior margin.

The mandibles (fig. 8), as usual, do not exhibit the slightest trace of a palp, and are
wholly indurated and rather brittle, so that they easily break by slight pressure. Their
body is navicular in form and shows an elegantly reticulate structure ; its posterior
pointed extremity is articulated to the dorsal part of the carapace at the point where, on
each side, the fissure separating the gastric area from the lateral parts begins. From
the anterior part of the body two unequal branches originate, the one projecting forward
nearly in the axis of the body, the other inward at a right angle to the same. The
anterior branch is slightly compressed and has the tip incurved, with the cutting
edge somewhat different on the two mandibles. On the right mandible it is simple
and only divided into two small teeth, whereas on the left mandible it is double, forming
two acute projections, each indistinctly bidentate, and the posterior one movably con-
nected with the anterior. Behind the cutting edge there is a dense series of curved
spines, arranged in a comb-like manner and occupying almost the whole length of the
inner edge of this branch. The posterior branch, representing the so-called molar
tubercle, is shorter and more cylindrical in form, and terminates in a finely fluted
surface, more oblique on the right than on the left mandible.

The first pair of maxille (fig. 9) are composed of a thick muscular basal part, from
the end of which originate two slightly incurving masticatory lobes, and of a peculiar
recurved palp. The outer masticatory lobe is of rather firm consistency and a little
narrowed towards the tip, which is truncated and armed with strong spines forming a
double row, besides a few very small bristles. The inner lobe is much shorter and of a
more membranous nature ; its tip is narrowly rounded, and bears four curved spines, the

16 THE VOYAGE OF H.M.S. CHALLENGER.

posterior of which is the longest and finely ciliated. The palp, which is affixed to the
outer side of the basal part close to the base of the exterior masticatory lobe, is very
elongate and narrow, turned straight backward, and projecting within the branchial
cavity. It is uniarticulate and lnear in form, with a distinct muscular band running
throughout its axis; from its tip two peculiar compressed sete originate, the outer being
somewhat longer than the inner, and both having one of its edges sharpened and armed
with fine recurved hooks.

The second pair of maxille (fig. 10) are more membranous in structure and of a
rather different appearance. The basal part is composed of two segments, the first of
which is very short and filled by strong muscles. The second segment is almost
triangular, and exhibits on the inner side two very slight masticatory expansions, the
anterior one somewhat obliquely truncate and provided with short ciliated bristles, the
posterior having a regular series of slender sete arranged in a comb-like manner. From
the lower side of the basal part, close to its apex, a very short biarticulate palp originates,
directed anteriorly and movably articulated. The last joint of this palp is obliquely
truncate at the tip and armed with a dense row of slender curved spines, and the first
joint is on the inner side expanded to a lobe of quite a similar appearance. Moreover,
the outer edge of the basal part forms a very thin and pellucid expansion, which may be
regarded as homologous with an exognath; this expansion has the edges quite smooth,
without any trace of bristles.

The maxillipeds (fig. 12), which are closely applied against the other masticatory
parts, and themselves partly covered by the two pairs of gnathopoda, form each a rather
stout and somewhat compressed stem, contiguous with the one of the other side, and
having the outer part slightly incurved. The basal part is rather large, occupying half
the length of the stem, and consists of two segments, the first of which, however,
is very short and rather difficult to see. At the end this part projects inwards
as a rounded triangular masticatory lobe, armed at the tip with a few short and thick
spines densely ciliated in their outer part. Along the inner edge there also occurs a
series of five rather strong plumose sete, and another strongly ciliated seta is found at
the base of the masticatory lobe. The terminal part of the stem, or the palp,
is composed of but four distinctly defined joints, of which the two first are very broad
and lamellar, and connected by a very oblique articulation ; the outer of these latter
joints is armed along the inner edge with a series of small; curved, bidentate spines
(fig. 12, a), besides numerous fine bristles, and has at the end externally a strong
anteriorly curving seta. The two last joints become suddenly much smaller and more
or less incurved; the penultimate is provided at the end with three ciliated sete (two
on the inner and one on the outer side); the terminal joint is very small and tipped with
three or four short bristles.

At the base of these limbs the remarkable branchial apparatus is affixed (see fig. 11).

REPORT ON THE CUMACEA. 17

The greater part of this apparatus constitutes a very large membranous plate of a
somewhat navicular form, and curved so as to exhibit an outer convex and an inner
concave surface. It terminates in a recurved acuminate lappet, and is furnished along
the inner edge with a regular series of lamellar gill-lobules, increasing in size anteriorly,
the foremost of which is turned backward. The whole plate is moved in the living
animal by an assemblage of strong muscles partly passing from the base of the corre-
sponding maxilliped. Anteriorly another smaller plate is seen extending forwards
and forming an imperfect funnel; it tapers to a narrow band-like ligament, and
terminates in an indurated lamella armed with six curved sete, and encircled by a
very thin and pellucid border (fig. 13). This terminal lamella, which is distinctly
marked off from the plate by a transverse suture, is found projecting in front of the
pseudorostral prominence in close juxtaposition to the corresponding one of the other
side, and in living specimens both lamella are seen performing a peculiar snapping
movement, whereby the water is expelled at intervals from the branchial cavities, during
the rhythmical strokes of the true branchial plate. Although this anteriorly directed plate
would seem to be partly connected at its base with the principal plate, I am still disposed
to entertain the assumption I have set forth in another work,’ that the former is the
highly modified exopodite of the maxillipeds, whereas the latter represents the epipodite.

Of the limbs of the trunk the two anterior pairs are closely applied against the oral
parts, and do not seem to have any locomotory function, and they may, therefore, properly
be termed gnathopoda. These two pairs differ materially from each other both as regards
size and structure.

The first pair of gnathopoda (fig. 14) form simple stems, composed of the same
number of joints as the maxillipeds, but are rather more slender. The basal part is
longer than the terminal and somewhat laminar, with a slight longitudinal keel running
along the upper surface and terminating posteriorly in a dentiform projection of the outer
edge. This part, as in the maxillipeds, chiefly consists of a single joint (the basal), the
coxal joint being very small and imperfectly defined. It is furnished at the end with a
rather strong ciliated seta, and has, moreover, a few bristles at the outer part of both
edges, those of the exterior edge being larger and about eight in number. The first
joint of the terminal part is quite short and somewhat swollen, almost globular, with a
single bristle at the end on the outer side; the succeeding joint is a little longer, con-
stricted at the base, and furnished along the inner edge with several ciliated bristles, and
a single one at the end exteriorly. The two last joints are rather small, and beset with
bristles at the end. At the base of each of these gnathopoda there is aftixed, in the adult
female of all Cumacea, a lamella edged with very long sete projecting within the marsupial
pouch. This lamella was, however, only slightly developed in the specimens of the
present species, owing to their being not full-grown.

1 Beskrivelse af de paa Fregatten Josephine’s Expedition fundne Cumaceer.
(ZOOL, CHALL. EXP.—PART Lv.— 1886.) ii 3

18 THE VOYAGE OF H.M.S. CHALLENGER.

The second pair of gnathopoda (fig. 15) are much larger, and also of coarser structure.
They originate widely apart, at the outer posterior angles of the carapace, but are
suddenly bent inwards so as to meet along the greater part of their length, being more
or less closely applied against the ventral side of the body. The basal joint is very large,
more than twice as long as the remaining part, and strongly indurated, exhibiting, especi-
ally on the lower surface, a distinct nodulose sculpture ; it gradually expands towards the
distal extremity, and juts out exteriorly as a large laminar projection of a somewhat trian-
cular or broadly lanceolate form, fringed along the inner edge with a row of short ciliated
bristles. At the base this joint bears a well-developed natatory exopodite of about half
its length, and composed of a simple cylindrical stem and a five-jointed terminal part,
furnished with long natatory sete. The ischial joint, not defined in the former pair, is
distinctly developed, though rather short and simply cylindrical. The meral joint, on the
other hand, exhibits a rather peculiar form, being expanded exteriorly to a large securiform
projection, The carpal joint is subtriangular in shape, or produced interiorly to an
almost right angle bearing a few simple bristles. The propodal jomt 1s quite narrow and
articulated to the outer corner of the preceding joint. The terminal joint, finally, is still
more narrow, linear, and together with the propodal, admits of being impinged against
the interior projection of the carpal joint.

The first pair of legs (fig. 16) are constructed upon the very same type as the last
pair of gnathopoda, and in function would seem to be intermediate between gnathopoda
and true legs, their basal part being generally closely applied against the ventral side of
the body, whereas the terminal part is freely projecting and very mobile, so as partly at
least to act as true locomotory organs. They are much larger than any of the other limbs,
equalling in length, when fully extended, the carapace and the two first segments of the
trunk taken together. The coxal joint, which on the gnathopoda appears but very
slightly indicated, is on these limbs distinctly defined (see figs. 1, 3), but so firmly con-
nected with the surrounding parts as generally not to be obtained in connection with
the leg by dissection. The basal joint is very large and strongly indurated, bemg more-
over greatly expanded in the proximal part, and forming an obtuse angle at the middle
of the inner edge; whereas the distal part is narrowed, without forming any expansion
at the apex. The edges of this joint are quite devoid of bristles except at the apex,
where a strong ciliated seta occurs exteriorly, and a much smaller one interiorly. The
exopodite affixed to the base of this joint is somewhat larger than that of the last pair of
gnathopoda, and its basal part is a little dilated at the middle, and is also more strongly
indurated. The remainder or terminal part of the leg is very slender, somewhat shorter
than the basal, and generally exhibits a geniculate bend at the junction between the
carpal and propodal joints. The lengths of these two joints are nearly equal, whereas
the two preceding are considerably shorter and thicker. The terminal joint is a little
shorter and also narrower than the preceding joint, and provided at the tip with

REPORT ON THE CUMACHA. 19

several slender bristles ; similar bristles are also found along the inner edge of the pro-
podal joint.

The four remaining pairs of legs are all very small, and, in both sexes, quite simple,
without any trace of exopodites. They represent the true ambulatory legs, and for this
purpose are also turned more exteriorly.

The anterior of these pairs (fig. 17) are somewhat shorter than the succeeding pair,
but have the coxal joint very large (see figs. 1, 2), forming an almost semicircular plate
firmly connected with the corresponding segment. Of the other joints the basal is as
usual the largest. The carpal joint is obliquely truncate at the apex, or produced
on the outer side to a blunt process bearing two stiff bristles. The propodal joint is
extremely small, whereas the terminal is rather large, compressed, and armed at the tip
and along the outer edge with six short spines.

The three posterior pairs of legs (figs. 18, 19) are quite similar in structure, de-
creasing, however, somewhat in length, owing to the basal joint being shortened succes-
sively. The coxal joint in all of them is very small and scale-like; the four outer joints
successively decrease in size, and the terminal joint has the form of a simple biarticulate
spine. A few strong bristles originate from the tip of each joint.

The ventral limbs of the tail are, as usual, completely wanting in the female (fig. 3).
In the young male (fig. 1) there are five pairs of imperfectly developed pleopoda, con-
sisting of a stout basal segment and two short branches without distinctly developed setee.

The uropoda (see fig. 20) are about twice as long as the last caudal segment, with the
basal part or scape almost cylindrical or slightly dilated towards the apex. The terminal
branches are both lanceolate in form and at the apex drawn out to a sharp point. The
inner one is the shorter, about as long as the scape, and uniarticulate, with the inner
edge finely serrulate; the outer branch is distinctly biarticulate, with the first joint very
short, and the inner edge of the second joint setiferous.

Habitat.—Several specimens of this form were collected on April 1, 1874, off the
entrance to Port Philip, Australia, Station 161, from a depth of 38 fathoms; sandy
bottom.

2. Cyclaspis pusilla, n. sp. (Pl. I. figs. 21-238).

Specific Characters.—$. Carapace almost globular, quite smooth at the sides, dorsal
line evenly curved; pseudorostral projection very short and obtuse. Ocular lobe only
shghtly produced, its outer part swollen and provided with well-developed visual
elements. Tail slighty keeled dorsally, but elsewhere quite smooth. Limbs much as in
Cyclaspis australis. Colour whitish, anterior part of body mottled with brownish-pink.
Length of adult female only 34 mm.

Remarks.—This beautiful little form is readily distinguished from the preceding

20 THE VOYAGE OF H.M.S. CHALLENGER.

species, not to speak of its much smaller size, by the smooth and almost globular carapace,
the shorter pseudorostral projection, and the simple structure of the caudal segments.

Description.—I have only had a single specimen of this species for examination, a
full-grown female with greatly developed marsupial pouch. Its length does not exceed
33 mm., and it thus belongs to the smaller forms of this order. The form of the body
(see figs. 21, 22) is that characteristic of the genus, the anterior part being greatly dilated
and almost globular, whereas the posterior part is extremely slender.

The carapace is very large and quite smooth at the sides, about as thick as high, and
with the dorsal line evenly arched. The pseudorostral projection is short and obtuse, and
limited below at each side by a well-marked notch. The ocular lobe (fig. 23) is rather
shorter than in the preceding species, and is provided at the somewhat dilated extremity
with distinctly developed visual elements.

The four exposed segments of the trunk decrease rapidly in size, and the two posterior
do not exceed the caudal segments in height or thickness.

The tail is very slender, cylindrical, and somewhat longer than the anterior division
of the body. It haga slight keel running along the middle of the dorsal surface, and this
keel is also continued along the seements of the trunk and the carapace ; but for the rest
the seements are quite smooth and exhibit the usual relation in length.

The colour of the animal is whitish, with small patches of brownish-pink, especially
along the sides of the anterior part of the body.

As to the limbs, they on the whole seem to agree fairly well with those of the
preceding species. The three anterior pairs of legs were, however, partly broken in the
specimen examined, and it may be that the terminal part of the first and second pairs
might have exhibited some minor differences, as to the relative length of the several
joints.

The marsupial pouch is greatly developed and projecting below, giving the anterior
part of the body an almost completely globular form.

Habitat.—I found the above-described specimen among some dredged sand kindly
sent to me by Mr. John Murray. The sand was procured with the dredge on September
8, 1874, at Flinders Passage (between Australia and New Guinea), from a depth of
7 fathoms.

3. Cyclaspis exsculpta, n. sp. (Pl. I. figs. 24-26).

Specific Characters.—§. Carapace very gibbous and strongly sculptured by elevated
crests limiting irregular depressed areas; two of the crests exceedingly strong, crossing
the dorsal surface of the carapace transversely, and uniting on each side near the infero-
posterior angle, being moreover connected above on each side by a thin longitudinal ridge,
whereby a large depressed area of irregularly oval shape is formed on each side of the

REPORT ON THE CUMACEA. il

carapace. Pseudorostral projection somewhat produced, obtuse at the tip, and limited
below on each side by a distinct angular notch. Ocular lobe extending along the dorsal
side of the pseudorostral projection to its tip, only slightly dilated at the apex and pro-
vided with but few corneal facets. Seoments of trunk angular, with three longitudinal
dorsal crests. Integuments highly indurated. Colour uniformly whitish. Length about
5 mm.

Remarks.—The present species is at once distinguished by the remarkable sculpture
of the carapace and the very strongly indurated integuments. Although the sole specimen
is incomplete, it may without any doubt be referred to the genus Cyclaspis.

Description.—The specimen examined wants the whole posterior part of the body, as
also the terminal part of the first pair of legs. The preserved anterior division of the
body has a length of 2 mm., and the whole body may thus have been about 43 or 5 mm.
long.

The carapace (see figs. 24, 25) is highly remarkable for its strongly marked sculpture.
It is rather gibbous in its hinder part and exhibits two very strong transverse crests
running across the dorsal surface and continued down the sides towards the infero-
posterior corner, where they unite almost at a right angle (see fig. 24). Of these crests
the anterior is placed immediately behind the frontal lobe and is uninterrupted in the
middle, whereas the posterior is divided in the middle line by a distinct notch at about
the posterior third of the length of the carapace (see fig. 25), Both crests are connected by
a median longitudinal keel and two lateral ridges, whereby the middle part of the carapace
is divided into four depressed areas, two dorsal and two lateral, the latter rather large and
of an irregularly oval or rounded triangular form. From the anterior crest, moreover, two
slight ridges run forward on each side, the one towards the base of the pseudorostral
projection, the other disappearing at some distance from the antero-lateral angle of the
carapace. Behind the posterior crest, finally, there occur on the dorsal surface three longi-
tudinal keels, each terminating in a somewhat rounded laminar projection at the posterior
edge. The pseudorostral projection is rather produced, obtusely triangular in form, and
limited below on each side by a distinet angular notch. The ocular lobe (fig. 26) is very
narrow and continued along the dorsal side of the pseudorostral projection to its very
apex ; it is but slightly dilated at the tip and exhibits a few rather small corneal facets ;
of pigment, on the other hand, no trace could be detected in the specimen examined.

The four exposed segments of the trunk are at a much lower level than the carapace
and exhibit a somewhat angular form, the dorsal surface being scalloped out on each side
of the middle line, or provided with three longitudinal crests. As usual, the three
posterior segments are rather smaller than the anterior and connected by very movable
articulations.

All the integuments are very strong and highly indurated, exhibiting under the
microscope a closely granulated structure.

22 THE VOYAGE OF H.M.S. CHALLENGER.

The colour of the animal is uniformly whitish, without any distinct pigmentary
deposits.

The limbs do not seem to differ materially in their structure from those of the two
preceding species. The terminal part of the first pair of legs was, however, wanting in
the specimen examined.

Habitat.—The above-described specimen I found among the same sample of dredged
material from which the preceding species was derived. The locality is stated as
follows :—September 8, 1874, at Flinders Passage, 7 fathoms.

Family Il, VauntHompsonrp &.

This family is rather closely related to the Cumide, from which, however, it differs
materially by the three anterior pairs of legs in the female, and all but the last pair in
the male, being provided with well-developed natatory exopodites. From the Lampro-
pide, with which family it agrees somewhat in the general appearance and the thin
integuments, it is distinguished by the want of a distinctly defined telson, and by the
male having five pairs of strongly developed pleopoda as in the Cumide. The family
comprises at present two distinct genera, viz., Vaunthompsonia, Spence Bate, and Lepto-
cuma, G. O. Sars. Besides, the form described by the author at an earlier date under
the name of Leucon anomalus, from the West Indies, would seem more properly to belong
to this family than to the Leuconide, representing in all probability another distinct
genus. Of these genera only the first is represented in the Challenger collection.

Genus Vaunthompsonia, Spence Bate, 1858.
Vaunthompsonia, Spence Bate, Nat. Hist. Review, vol. v. p. 203.

Generic Characters.—Form of body not very slender, scarcely compressed; anterior
and posterior divisions not sharply defined from each other. Integuments thin,
squamous. Carapace only slightly arcuate above; pseudorostral projection very short ;
antero-lateral angles more or less produced. Eye distinctly developed. Five segments
of the trunk exposed behind the carapace. Last caudal segment produced at the end,
but without any distinct telson. Antennule small, similar in both sexes, one of the
flagella very minute, uniarticulate. Antenne in female biarticulate, with two strong
ciliated setee, in male shorter than the body. First pair of legs rather elongate and
slender; second pair spinous, with the ischial joint not defined; penultimate pair in
female without any rudiment of exopodite. Pleopoda of male very large, with inner
plate uniarticulate, outer biarticulate. Uropoda strongly spinous, scape rather short,
both branches biarticulate.

REPORT ON THE CUMACEA. 23.

Remarks.—This genus is chiefly distinguished from Leptocuma by the body being
less elongate and not compressed, by the presence of a well-developed eye, by the second
pair of legs having the ischial joint obsolete, and finally by the penultimate pair of legs
in the female wanting the rudimentary exopodite present in the former genus. Of the
genus only a single species, Vawnthompsonia cristata, Spence Bate, was hitherto known.
The following new species from the Challenger Expedition is now added.

4. Vaunthompsonia meridionalis, n. sp. (Pl. IL. figs. 1-5).

Specific Characters.— ¢ . Carapace shorter than the free segments of the trunk taken
together, with two short serrate crests on the posterior part of the dorsal surface, anterior
part unarmed. Pseudorostral projection broadly truncate at the tip, anterior edges
finely serrate and having three stronger serratures at the lower corner ; subrostral notches
distinct. Antero-lateral angles of carapace sharply produced, inferior edges strongly
serrate in the anterior part. Ocular lobe rather large, almost reaching to the tip of the
pseudorostral projection, with two small denticles in its anterior part. First pair of legs
shorter than in the typical species, with the three outer joints subequal. Posterior pro-
jection of last caudal segment triangular, with five slender spines on each side. Uropoda
shorter than the two last caudal segments taken together, scape comparatively stout, inner
branch not longer than outer, with last joint small, scarcely half as long as first, both
strongly spinous on inner edge. Length, 10 mm.

Remarks.—This new species may easily be distinguished from the typical form,
Vaunthompsonia cristata, Spence Bate, by the carapace having only two short diverging
crests on its posterior part, whereas the anterior part is quite smooth; by the broadly
truncate pseudorostral projection and the distinctly marked notch beneath the same ; also
by the much shorter legs of the first pair, and finally by a rather different form of the
uropoda.

Description.—The sole specimen before us is a young female, with the marsupial
pouch not yet developed. It measures in length about 10 mm.

The general form of the body (see Pl. IL. figs. 1, 2) is nearly as in the typical species,
though somewhat less compressed. The anterior division tapers gradually backwards,
without being sharply defined from the posterior.

The carapace is comparatively rather small, not attaining the length of the free
segments of the trunk taken together. The dorsal surface is but very little vaulted,
and exhibits posteriorly two short curved serrate crests diverging anteriorly, but for the
rest 1s quite smooth, without any trace of the strongly serrate longitudinal crest observed
in the typical species. The pseudorostral projection (see fig. 4) is very short, and broadly
truncate at the apex, with the anterior edges finely serrate, and having moreover three
much stronger denticles inferiorly. The notch limiting this projection inferiorly on each

24 THE VOYAGE OF H.M.S. CHALLENGER.

side is very distinct and rather deep, and the antero-lateral corners of the carapace are
produced to a sharp point. The inferior edges of the carapace are evenly curved, and in
the greater part of their length strongly serrate. The ocular lobe (see figs. 3, 4) is rather
large and oval in form, almost reaching to the tip of the pseudorostral projection. It is
armed on the anterior part with two small anteriorly directed denticles, and seems to
exhibit pretty well developed visual elements.

The exposed part of the trunk is composed of five well-defined segments, the anterior
of which is the shortest, the second the largest. On all the segments the lateral parts
form broad laminar epimera, slightly projecting at the sides (see fig. 2).

The tail is only very slightly longer than the anterior division of the body, and of
the usual slender cylindrical form. Of its segments the penultimate is by far the longest.
The last segment (sce fig. 5) is rather short, and has the posterior edge produced in the
middle to a short triangular plate arching over the anal orifice, but not defined from the
segment by any suture. On each side of this plate is found a row of five slender
spines increasing in length posteriorly.

All the integuments are rather thin, only very slightly indurated, and exhibiting
under the microscope a squamous structure. The colour of the specimen preserved in
spirit is whitish, with a few stellate pigmentary patches, especially distinct on the
carapace.

The antennulz (fig. 4, a') are of moderate size, and have one of the flagella very short ,
and uniarticulate, the other triarticulate, and bearing at the tip two ribbon-like sensory
appendages.

The antenne (fig. 4, a’) are very small and biarticulate, their outer part projecting
from the bottom of the anterior notch of the carapace.

The terminal plate of the exopodite of the maxillipeds projecting in front of the
carapace (see figs. 3, 4, z) is very thin and quite membranous, being drawn out to a
narrow, somewhat tubular lappet.

The first pair of legs (see fig. 1) are rather slender, though not nearly so elongate
as in the typical species; they only slightly exceed in length the carapace, and have the
three last joints nearly uniform in size.

The remaining pairs of legs do not seem to differ materially in structure from those
of Vaunthompsonia cristata, and as in that form only the two last pairs are simple,
whereas the two preceding pairs are provided with well-developed natatory exopodites
of similar structure to those on the first pair. The second pair are only slightly shorter
than the first, and composed of but six joints, the ischial jot not being distinctly
defined.

The uropoda (see fig. 5) do not attain the length of the two posterior caudal segments
taken together, and exhibit a comparatively coarser structure than in the typical species.
The scape is rather thick, and armed along the inner edge with about ten strong spines.

REPORT ON THE CUMACEA. 25

The branches are about equal in length and somewhat longer than the scape, whereas
in the typical species the inner one is by far the longer, and the outer scarcely as long
as the trunk. The inner branch is composed of two distinctly defined joints, the first of
which is much the larger and somewhat expanded at the base, sublaminar, and armed
along the inner edge with a dense series of spines, some of which are more elongate than
the rest. The outer joint of this branch does not attain even half the length of the
preceding joint, and is also much narrower. It is armed with about eight spines, three
of which originate from the apex, the rest from the inner edge; the apical spines being
by far the strongest. The outer branch is also biarticulate, but the first joint is here
very short, whereas the terminal joint is rather elongate, and furnished along the imner
edge with a row of strong ciliated setae; from the apex four somewhat more elongate
setze originate, and to the outer edge about six slender spines are affixed, one of which
occurs at some distance from the rest, close to the apex.

Habitat.—l found the above described specimen in examining a sample of dredged
mud preserved in strong spirit, and kindly sent to me by Mr. John Murray. The mud
was procured on January 29, 1874, off Cumberland Bay, Kerguelen Islands, from a
depth of 127 fathoms, Station 149H.

Family III. Lampropip.

I have seen fit to establish this family for the reception of three northern genera,
Lamprops, Hemilamprops, and Platyaspis, which present several peculiar characteristics
not found in other Cumacea, and now [am able to add another generic type from the
Challenger Expedition, undoubtedly belonging to the same family. The genus Chalaro-
stylis, established by Norman for a Cumacean from the “ Porcupine” expedition, must
also, I think, be referred to this family, which thus at present comprises no less than
five different generic types.

The most characteristic features distinguishing this family from the two preceding
are:—the fuller development of the antennulz, both flagella of which are distinctly
articulated and nearly equal in size; the less rudimentary structure of the antenne in
the female; the comparatively great length of the second pair of legs; the presence in
the male of but three pairs of pleopoda (in one of the genera, Lamprops, the pleopoda
are even quite wanting); the distinctly developed telson; and finally, the slender form of
the uropoda, the inner branch of which is triarticulate. All the known forms belonging to
this family, except the one described below, would seem to be restricted to the northern
ocean.

(ZOOL, CHALL. EXP.—PART LY.—1887.) li 4

26 THE VOYAGE OF H.M.S. CHALLENGER.

Genus Paralamprops, n. gen.

Generic Characters.—Anterior division of body well defined from posterior. Cara-
pace large and sculptured with denticulated crests, dorsal surface vaulted, sides somewhat
expanded; pseudorostral projection very slight, subrostral notches obsolete. Ocular lobe
very small, eye wanting. Exposed part of trunk composed of five well-defined segments
with laterally projecting epimera. Tail very slender. Antennulz unusually large, with
both flagella elongate and multiarticulate. Antenne in female five-articulate, with two
strong ciliated setae on the middle joint. First pair of maxillee without any trace of palp.
Second pair of gnathopoda very slender, basal joint not expanded at the end. The two
anterior pairs of lees in female with well-developed natatory exopodites, third and fourth
pairs with a small biarticulate appendage at the base. Three pairs of pleopoda present
in male. Telson narrow, with the edges spinulose. Uropoda slender, inner branch
longer than outer.

Remarks.—This new genus is chiefly distinguished by the large vaulted carapace,
sculptured with serrate crests, the total want of the eye, the strong development of the
antennulee, and the absence of the usual palp on the first pair of maxille, in which
latter respect it differs from all hitherto known Cumacea. In the other anatomical
details, it would seem to agree most closely with the genus Hemilamprops, though in
some particulars also exhibiting a certain aflinity to the genus Platyaspis. Only a single
species of this genus is represented in the collection.

5. Paralamprops serrato-costata, n. sp. (Pl. IL figs. 6-13; Pl. IIL).

Specific Characters.—Form of body very slender. Carapace much larger than
exposed part of trunk, sculptured by seven longitudinal serrate keels, one median
running along the anterior half, two subdorsal on each side, occupying the posterior,
somewhat gibbous part of the dorsal surface, and two lateral encircling the carapace at
the sides and meeting in front. Pseudorostral projection short and somewhat upturned.
The three anterior exposed segments of the trunk somewhat gibbous in the dorsal part
and armed with small denticles, epimera produced anteriorly as an acute angle. Tail
extremely slender and much longer than anterior division of body. Antennulz with
the peduncle densely setose; flagella almost as long as peduncle, inner triarticulate,
outer six-articulate. Penultimate joint of antennz in female with outer edge denticu-
late. First pair of legs about as long as anterior division of body, the three outer joints
very slender, penultimate the longest; second pair nearly as long as first, antepenulti-
mate joint strongly spinose at inner edge. Telson shorter than scape of uropoda, slightly
dilated at base, outer part sublinear, with about nine pairs of lateral denticles, the last
one much larger than the rest, apex with three strong spines of equal size. Uropoda

REPORT ON THE CUMACEA. 27

very elongate, scape narrow and densely spinulose at inner edge, inner branch about as
long as scape, first joint almost twice the length of the two others taken together, all
three joints densely spinulose at inner edge; outer branch with first jomt very small,
second elongate and slender, slightly tapering, with short bristles on both edges. Length
of female, 12 mm.

Remarks.—The present species being the only one as yet known, it is rather difficult
to point out the characters which should be regarded as strictly specific. Meanwhile, I
have thought it right to enumerate some structural details, which, from analogy with
related genera, may be assigned the value of specific characters.

Description.—Of this form I have been able to examine numerous specimens, both
males and females. None of them, however, seem to have attained to sexual maturity,
as there are neither ovigerous specimens, nor males with fully-developed antennze and
pleopoda. The length of the largest female specimen is about 12 mm., that of the males
somewhat less.

The form of the body (see Pl. II. figs. 6-8) is extremely slender and elongate, with
the anterior division well defined from the posterior, and of a somewhat ovoid form.

The carapace is of very considerable ‘size, much larger than the exposed part of the
trunk. It is somewhat expanded laterally and distinctly sculptured by longitudinal
serrate keels, of which the following may be distinguished :—one median, running along
the anterior part of the dorsal surface and terminating at the end of the frontal lobe ;
two subdorsal keels on each side of the strongly arched branchial regions, the inner one
the shorter and curved, occupying the most prominent part of that region and confined
to the posterior half of the carapace, the outer keel reaching anteriorly to the base of the
frontal lobe ; finally, on each side a lateral keel horizontally encircling the carapace and
continued anteriorly along the edges of the pseudorostral projection to its very apex.
There is also a more or less distinct but very small and interrupted keel, also serrate, on
the posterior part of the carapace between the lateral and outer subdorsal keels.
Beneath the lateral keel, on the ventrally inflected parts of the carapace, a shght longi-
tudinal keel may moreover be noticed (see Pl. HI. fig. 1), but this keel, unlike the
others, is quite smooth. The pseudorostral projection is very short and somewhat
upturned; it is not limited beneath by any distinct notches, and there are no
projecting angles marking off the inferior from the anterior edges of the carapace. As
seen from above (PI. IL. fig. 6) the carapace appears rather broad, on account of the
expanded sides, its breadth being considerably greater than its height; anteriorly it is
evenly rounded, without any distinctly marked projection in the middle. The ocular
lobe (see Pl. IIT. fig. 2) is very small, and of a short conical form, without any trace of
pigment or visual elements; it does not extend, as in the above described species of the
genera Cyclaspis and Vaunthompsonia, along the dorsal side of the pseudorostral
projection, the lateral lobes of which meet in front of it.

28 THE VOYAGE OF H.M.S. CHALLENGER.

The exposed part of the trunk is composed of five well-defined segments, the three
anterior of which are somewhat gibbous dorsally and provided above with a short
transverse row of small denticles. The epimera of all the segments are distinctly
marked and laterally extended ; those of the three anterior segments produced anteriorly
as an acute angle. Of the segments, the second is the largest, the last being very small,
scarcely broader than the caudal segments.

The tail is extremely slender and elongate, almost twice as long as the anterior
division of the body. Its segments are cylindrical, with the posterior margin slightly
emarginated above and below. They taper somewhat posteriorly and increase successively
in length to the penultimate, which is very elongate. The last segment is much shorter
than the others, somewhat depressed and expanded at the end.

The integuments are not very strong, though somewhat more indurated than in the
other forms belonging to this family, and they exhibit a shght squamous structure.

The colour—to judge from a fresh specimen mounted in Canada balsam—is uniformly
yellowish, without any pigmentary spots or ramifications.

The antennule (PI. II. fig. 9) are remarkable for their unusual size, being almost as
long as the carapace, and also for the great development of the flagella. The peduncle
is rather elongate, and as usual, composed of three distinctly defined joints. The basal
joint is about as long as the two others taken together, slightly curved, and provided at
the end with several strong, partly ciliated bristles, and a few small denticles. The two
succeeding joints are scarcely narrower than the basal and densely setose, especially
towards the inner edge; some of the sete are ciliated, some simple and very slender.
The second joint, like the basal, is finely denticulate at the end, and somewhat larger
than the third. Of the flagella, the outer one is almost as long as the peduncle, and
composed of no less than six distinctly defined joints—a quite unusual number—each
provided at the end with slender simple bristles. Of the joints, the first and penultimate
are the longest, whereas the last joint is very small and might be easily overlooked.
Besides the bristles, this flagellum bears at the tip two ribbon-like, densely articulated,
sensory appendages, one of which originates from the end of the penultimate joint, the
other from the last jot. The inner flagellum, which in the Cumacea generally presents
a more or less rudimentary state, is rather fully developed, only slightly shorter than the
outer, and composed of three slender joints of about equal size, and beset with bristles.
In the young male the antennulz (sce Pl. III. fig. 14) do not differ materially from those in
the female, except by the peduncle being slightly thickened, and by the first joint of the
outer flagellum being somewhat expanded at the base; in all probability in the adult male
this joint bears a bunch of sensory appendages, as in the males of several other Cumacea.

The antennze in the female (PI. II. fig. 10; Pl. II. fig. 1, a”) are less rudimentary
than in most other Cumacea, forming a slender stem composed of five distinctly defined
joints. Of these the four first represent the peduncle, and the last the flagellum.

REPORT ON THE CUMACEA. 29

The peduncle is geniculate in the middle, the two outer joints almost forming a right
angle with the two inner ones. The third joimt is the smallest and provided with two
strong hairy sete and a little dentiform projection. The fourth joint is linear and armed
along the outer edge with a row of five small denticles. The flagellum forms a very
slender and narrow joint, about half as long as the peduncle, and provided at the tip
with four delicate auditory bristles. In the young male the antennz (see PI. IIT. fig. 14)
exhibit the usual appearance, being strongly geniculate at the base and reflexed beneath
the carapace. The proximal part of the peduncle is provided with four strong ciliated
setee curving anteriorly; the distal part of the peduncle is smooth and composed of two
well-defined segments, the outer one the larger. The flagellum has the appearance of a
densely annulated vermiform appendage, slightly flexuous, and as yet quite smooth,
terminating in an obtuse point.

The anterior lip (Pl. I. fig. 11) forms a semi-oval fleshy prominence, slightly emarginate
at the tip, with the free edge densely ciliated.

The posterior lip (fig. 12) is quite membranous, its lateral lobes rounded, triangular,
and terminating in a somewhat incurved, densely ciliated corner. The inner edges of
the lobes are also ciliated throughout their whole length.

The mandibles (fig. 13) are well developed and similar in structure to those in the
genus Cyclaspis, as described above, though somewhat stouter and with the body com-
paratively shorter.

The first pair of maxillee (PI. LIT. fig. 3) are markedly distinguished by the total
want of the usual reflexed palp, of which not even the slightest trace could be found by
the most careful dissection of several specimens, both males and females. No other form
of Cumacea hitherto known wants this part. In other respects, however, these maxillee
do not exhibit any marked peculiarity in their structure.

The second pair of maxillee (fig. 4) present quite the usual appearance.

The maxillipeds (fig. 1, mp; figs. 5, 6) are rather short and stout. The basal joint,
as usual, juts out at the end on the inner side as a linguiform masticatory lobe, having
along the inner edge a row of ciliated bristles, and at the tip several short dentiform
spines. The meral and carpal joints are broad and laminar, the former provided at the
outer edge with a strong ciliated seta, the latter with two somewhat smaller ones; the
inner edge of this joint is also provided with a row of curved spinules, which are
denticulated at one of their borders in a comb-like manner (fig. 5, @), as also with
numerous simple bristles. The propodal joint becomes suddenly much narrower and
strongly incurved, bearing at the end internally two ciliated sete, and externally a bunch
of somewhat more slender bristles. The terminal joint is very small and linear, with
three small spines at the tip.

The structure of the branchial apparatus in this form (see fig. 6) would seem to
corroborate the supposition set forth by the author at an earlier date, but not adopted by

30 THE VOYAGE OF H.M.S. CHALLENGER.

Dr. Boas, viz., that both the exopodite and endopodite take part in the formation of this
peculiar apparatus. For in this species it is clearly composed of two different parts,
well defined from each other, the posterior part apparently representing the epipodite,
the anterior the exopodite. The epipodite forms an irregular, oblong, membranous plate,
broadest anteriorly, where it exhibits a freely projecting acute corner, and gradually
tapering posteriorly, its extremity forming a lanceolate flap curving anteriorly in the
form of a hook. To the inner face of this plate are affixed six digitiform gill-lobules
pointing forwards, five of which form a row along a narrow inflexed lamella proceeding
from the inner edge, whereas the sixth occurs at about the middle line of the plate. The
anterior division of the branchial apparatus, which in my opinion represents the highly
modified exopodite, forms an anteriorly directed narrow plate, suddenly constricted in
front of the middle to a narrow semicylindrical neck, and terminating in a triangular
expanded part, which is found protruding from beneath the pseudorostral projection.
The whole of this division only serves as an efferent duct for the water introduced into
the branchial cavity, and in the living animal probably does not partake in the
rhythmical movements of the epipodal division.

The first pair of gnathopoda (fig. 1, gn’; fig. 7) are rather slender and have the ischial
joint distinctly defined, though very small. At the end of the large and somewhat
curved basal joint there occur at both edges several strong plumose setee. The carpal
joint is densely setose on the inner edge and considerably larger than the propodal joint,
which is slightly dilated at the end, where it is densely beset with bristles. The terminal
joint is narrow, conical, and provided with a strong apical spine. At the base of these
gnathopoda in the female the usual setose lamella was distinctly developed, though the
sete were still very short and rudimentary.

The second pair of gnathopoda (fig. 1, gn”; fig. 7 bis) ave, as usual, provided with
well-developed natatory exopodites, the terminal part of which is composed of eight
setiferous articulations. In other respects the endopodite or stem has much the same
appearance as that of the first pair of gnathopoda, though somewhat more elongate and
with the basal joint slightly tapering towards the end, and bearing along the inner edge a
dense series of strong plumose sete.

The first pair of legs (fig. 8) are rather slender, and, when fully extended, about as
long as the whole anterior division of the body. The basal joint, occupying somewhat
more than one-third of the length of the leg, is strongly curved and setose along the
whole of the inner edge and the distal half of the outer. The three succeeding joints
exhibit a similar relation in length to each other as in the gnathopoda, though somewhat
more slender, and only sparingly beset with bristles. The two next joints, on the other
hand, are much more elongate, and form with each other and with the preceding joint
distinct geniculate bends. The penultimate or propodal joint is considerably longer than
the terminal, which is very narrow and linear; both joints are furnished, especially on

REPORT ON THE CUMACEA. 31

the inner edge, with scattered, slender sete, three of which arise from the tip of the
terminal joint. The exopodite is of the same structure as that of the second pair of
enathopoda, except that the terminal part has one joimt more ; the basal part is provided
with six slender, ciliated bristles along the outer edge.

The second pair of legs (fig. 9) are not very much shorter than the first, and are like-
wise very slender and composed of the same number of joints. The basal joint is almost
straight and not so densely beset with bristles as that of the first pair. The carpal joint
is rather elongate, linear, and armed along the inner edge with a dense row of short
spines. The propodal joint, on the other hand, is very small, and constricted at the base,
whereas the terminal joint is elongate, linear, and provided with scattered spine-like
bristles ; these two joints, taken together, about equal in length the carpal joint. These
legs are in both sexes provided with well-developed natatory exopodites of the same
structure as those on the first pair.

The three posterior pairs of legs (figs. 10, 11) successively decrease in length, and
have the basal joint very slender, and longer than all the others combined. In the female
all these legs at first sight appear simple, without any exopodites, but on closer examination
a very small and narrow appendage is found affixed to the basal joint of the two anterior
pairs (see fig. 10), as in the genera Lamprops and Hemilamprops. This appendage
(fig. 10, a), which undoubtedly represents a rudimentary exopodite, is composed of two
distinctly defined joints of nearly equal length, the last of. which is provided with four
simple bristles. In the male the two anterior pairs of these legs (fig. 15) have fully-
developed natatory exopodites of the same structure as those of the preceding pairs, and
the basal joint exhibits a shght dilatation at the base to receive the muscles moving
the exopodite.

The last pair of legs (fig. 11) are in both sexes simple and much smaller than the
preceding pairs, both the basal and meral joints being considerably shorter.

In most of the female specimens the incubatory lamellae forming the marsupial pouch
are in the course of development at the bases of the second pair of gnathopoda and the
three anterior pairs of legs, though they are still rather small, so as not to meet in the
middle line (see fig. 1).

Only three pairs of pleopoda are present in the male, as in the genera Henulamprops
and Platyaspis, and they belong to the three anterior caudal segments (see Pl. IT. fig. 8).
They were not fully developed in the specimens examined (PI. LII. fig. 16), though
exhibiting all their parts distinctly defined. The basal part or scape is narrow,
quadrangular, and still without any trace of bristles or spines. The terminal plates
(fig. 17) are very short, and each of them is provided at the tip with four short and thick
bristles. The outer plate is distinctly biarticulate, whereas the inner is uniarticulate ;
the latter is somewhat broader than the outer one, and its external edge juts out in the
middle as a narrow conical process bearing two auditory bristles.

iY)
bo

THE VOYAGE OF H.M.S. CHALLENGER.

The telson (see fig. 12), as in the other forms belonging to this family, is distinctly
developed, and defined from the last caudal segment by a well-marked transverse suture.
It is about twice as long as the last caudal segment and very narrow, almost linear, with
the base very slightly dilated to receive the terminal part of the intestine. Its distal
part is armed on each edge with a regular series of about ten denticles, the last of which
(see fig. 13) is much longer and stronger than the rest, and precisely of the same
appearance as the three apical spines, which are quite uniform in size.

The uropoda (see fig. 12) are extremely slender and more than half as long as the
tail. The scape is considerably longer than the telson, narrow and cylindrical, with the
inner edge in the greater part of its length armed with a dense row of somewhat unequal-
sized spines. Of the terminal branches the inner one is the longer, nearly equalling
in length the scape, and composed of three distinctly defined joints, which are spinulose
at their inner edges. The first joint of this branch is by far the largest, being almost
twice as long as the two others taken together ; of the latter, the terminal is the smaller
one. The outer branch about equals in length the two first joints of the inner taken
together, and is only biarticulate, the first joint being very short, and the last slender,
and gradually tapering towards the tip, with a series of very delicate bristles on both
edges, those of the inner edge being more elongate. From the tip of this branch, more-
over, a somewhat stronger seta arises.

Habitat.—Numerous specimens of this form were collected on January 29, 1874, off
Cumberland Bay, Kerguelen Islands, from a depth of 127 fathoms (Station 149H). A
sample of sifted mud from the same locality, kindly sent me by Mr. John Murray, also
contained, besides numerous small Amphipoda and Isopoda, several specimens of this
Cumacean, which thus seems to have occurred in great profusion at this place.

Family [V. Levconip™.

This family exhibits some very marked anatomical characters, distinguishing it from all
other known Cumacea. Thus the mandibles are quite peculiar in structure, and the other
masticatory parts also present certain well-marked differences from the usual structure.
Of the legs, the three anterior pairs in the female are provided with fully-developed
natatory exopodites, as in the Vaunthompsoniide, but only two pairs of pleopoda are
present in the male. The tail in all the forms is very slender and highly movable, but
completely wants the telson, whereas the uropoda are powerfully developed. None of
the forms show any trace of an eye, and their habits would seem to be chiefly fossorial,
the second pair of legs having, in accordance therewith, an unusually strong develop-
ment.

REPORT ON THE CUMACEA. 30

The family at present comprises three genera, viz., Leucon, Kroyer, Hudorella,
Norman, and EHudorellopsis, G. O. Sars, the two first of which are represented in the
Challenger collection. These two genera are easily recognised by the structure of the
carapace, as follows :—

compressed, with a dorsal serrate crest; pseudorostral projection prominent,
antero-lateral corners of carapace more or less produced, . : : . Leucon, Kroyer.
Carapace
very short, truncated in front, dorsal surface smooth, pseudorostral projection
wanting, . : : 3 : 6 : : : 7 : . udorella, Norman.

Genus 1. Leucon, Kroyer, 1846.
Leucon, Kroyer, Nat. Hist. Tidsskr., Bd. ii. Heft. ii p. 208.

Generic Characters.—Body very slender. Carapace compressed, with a dorsal serrate
crest (sometimes obsolete in male); pseudorostral projection prominent; antero-lateral
angles of carapace more or less produced. Antennulz of usual structure, not geniculate,
inner flagellum mostly rudimentary; antennee in female triarticulate, in male attaining the
@, clothed with ciliated
bristles ; terminal jot compressed and armed at the tip with curved spines; second
pair rather powerful, ischial joint obsolete, terminal more or less compressed and armed
with stiff radiating spines. Last caudal segment slightly produced at the end. Uropoda
rather powerful, scape cylindrical, both branches biarticulate, inner spinose, outer
setose.

Remarks.

length of the body. First pair of legs elongate, gradually taperin

This genus is chiefly distinguished by the form of the carapace, which
exhibits a well-marked dorsal crest, more or less strongly denticulate, and a distinctly
prominent, often very elongate, pseudorostral projection. In anatomical details it
exhibits great affinity to the genus Hudorella, except that the antennule are less
powerful in structure, and not, as in that genus, geniculate. The genus at present
comprises, besides the two new forms described below, nine species, seven of which are
from the Northern Ocean, one from the Mediterranean, and one from the Atlantic. The
two species procured during the Challenger Expedition are easily distinguished by the
following characters :—

triangular, comparatively short, scarcely longer than frontal lobe.
Dorsal crest of carapace densely serrate. Inner branch of

uropoda shorter than outer, . - : F : } . Leucon assimilis, n. sp.
Pseudorostral poe ’ ’ P.

rojection . : :
prey conical, very slender and elongate, slightly ascending. Dorsal

crest of carapace with scattered denticles. Inner branch of
uropoda longer than outer, . : ; : . : . Leucon tenuirostris,n. sp.

(ZOOL, CHALL. EXP.—PART Ly.—1887.) Tii 5

34 THE VOYAGE OF H.M.S. CHALLENGER.

6. Leucon assimilis, n. sp. (Pl. IV.).

Specifie Characters.—Form of body moderately slender. Carapace with the antero-
lateral corners triangularly produced, dorsal crest densely serrate, three of the denticles
placed near the posterior margin at some distance from the others; pscudorostral
projection triangular, scarcely occupying one-fourth of the length of the carapace.
Inner flagellum of antennule very small and knob-like. First pair of legs slender, with
penultimate and antepenultimate joints subequal; second pair with terminal joint narrow
and linear. Uropoda with inner branch shorter than outer, last joint scarcely half as
long as first, both joints strongly spinulose on the inner edge. Length, 9 mm.

Remarks.—This form is very nearly allied to the northern species, Lewcon nasicus,
Kroyer, from which it may, however, be distinguished by the somewhat different form of
the pseudorostral projection, which is comparatively shorter and simply triangular, not
as in that form obliquely truncate at the tip.

Description.—The form of the body (PI. IV. figs. 1, 2), as in most of the species, is
rather slender, though somewhat less so than in Lewcon nasicus, and slightly compressed,
especially in the anterior part, with no sharply-marked definition between the anterior
and posterior divisions.

The carapace, occupying about half the length of the anterior division, is rather deep
and distinctly compressed, with a well-marked crest running along the dorsal side. This
erest is somewhat arcuate in the anterior part and densely denticulate, the denticles
having the form of regular serratures, from eighteen to twenty in number, the three
posterior of which are removed from the rest and placed at a short distance from the
posterior margin of the carapace. Between each pair of serratures a small hair is
affixed. The pseudorostral projection scarcely oceupies one-fourth of the length of
the carapace, and is triangularly pointed (see fig. 3), with the upper edge quite smooth
and horizontal, the lower edges finely denticulate in the outer part and provided with
slender bristles. The fissure limiting the frontal lobe is distinctly marked, and just
above it on each side there are three small denticles. The end of the frontal lobe does
not exhibit any distinct ocular prominence, and the eye is wholly wanting, as in the other
species of the genus. The antero-lateral corners of the carapace are distinctly projecting
and triangular in form; between them and the pseudorostral projection the edges of the
carapace are evenly incurved and finely denticulate. The inferior edges of the carapace
are strongly serrate in the anterior part, and posteriorly curve slightly upwards to the
rounded postero-lateral corners.

Behind the carapace five distinctly defined segments belonging to the trunk are
exposed, all of them having broad laminar epimera slightly projecting laterally. Of these
segments the first is very narrow, the others about equal in length, but successively
diminishing in height, so that the last segment is not higher than the caudal segments,

REPORT ON THE CUMACEA. 35

to which it, moreover, seems to bear a closer relation in so far that it is much more
movably articulated to the penultimate segment of the trunk than to the first caudal
segment.

The tail is rather slender and somewhat longer than the anterior division of the body.
Its segments are regularly cylindrical, with the posterior edge somewhat more emarginated
ventrally than dorsally, and forming on each side an obtuse angle. Of the segments
the penultimate as usual is the longest. The last segment is rather small and forms
posteriorly a rounded prominence arching over the anal orifice.

The integuments are thin and pellucid, without any distinct sculpturing.

The colour—to judge from a specimen mounted in Canada balsam—is uniformly light
yellowish, without any pigmentary deposits.

The antennul (see fig. 1) are seen projecting in front from the sinus between the
pseudorostral projection and the antero-lateral corners of the carapace. They are of
moderate size (see fig. 4) and have the joints of the peduncle successively diminishing a
little both in length and thickness. At the end of each joint there are several slender
setee, which on the middle joint form a complete whorl around its end. Of the flagella
(see fig. 5), the inner one is very small and knob-like, bearing, besides three simple un-
equal sete, a single very delicate auditory bristle (fig. 6) with only two diverging cilia
at the tip; a similar bristle is also found affixed to the end of the peduncle internally
(see fig. 5). The outer flagellum scarcely exceeds in length the last joint of the peduncle,
and is, as usual, composed of three joints, the first being twice as long as the other two
taken together. The last joint is very small and bears, besides a few simple bristles,
two ribbon-like and closely annulated sensory appendages.

The antenne of the young male dissected (see fig. 4) are still imperfectly developed,
scarcely reaching the length of the anterior division of the body, but yet exhibiting a
distinct definition of the peduncle from the flagellum. The peduncle is geniculate at the
base, with the proximal part irregularly constricted and bearing three anteriorly curving
ciliated bristles, and the distal part cylindrical and exhibiting an imperfect articulation
anterior to the middle, but still without any trace of bristles. The terminal part of the
antenna forms a densely annulated sheath, gradually tapering to the tip, and within this
sheath the developing filiform flagellum may be traced.

The anterior lip (fig. 7) has the form of a small rounded prominence, the posterior part
of which is somewhat dilated and slightly emarginated at the free edge, which is finely
ciliated.

The posterior lip (fig. 9) is very delicate and difficult to separate from the adjoining
parts, but seems to exhibit the usual structure. The lateral lobes are very thin and
membranous, with the inner corner somewhat projecting and incurved, but without any
teeth, whereas a delicate ciliation is found along the inner and part of the outer edges of
the lobes.

36 THE VOYAGE OF H.M.S. CHALLENGER.

The mandibles (fig. 8) are comparatively small, and exhibit a structure rather differing
from that in the above described Cumacea. Thus the body of the mandibles is not, as in
these forms, navicular, but almost triangular, with two projecting angles, the outer pointed,
the inner obtusely rounded. By the outer angle the mandible is fixed to the inside of
the carapace at the point where the fissure limiting the frontal lobe terminates; to the
inner the strong rotatory muscles are affixed, whose points of insertion are visible as a
number of lucid spots in the middle part of the carapace, symmetrically arranged on each
side of the middle line (see fig. 2). The anterior branch of the mandibles is comparatively
short and strongly incurved, with the cutting edge divided into two comparatively simple,
dentiform projections ; instead of the regular comb-like series of curved spines occurring
in most other Cumacea behind the cutting edge, only two simple bristles are found on
each mandible affixed close together. The posterior branch is very thick and massive,
with a large fluted molar surface.

The first pair of maxills (fig. 10) exhibit the usual structure, with this exception,
however, that the posteriorly bent palp has but a single terminal seta.

The second pair of maxille (fig. 11) are comparatively small and want the dense
series of delicate bristles affixed to the inner edge of the basal part in other Cumacea,
instead of which there are only found three hook-lke spines.

The maxillipeds (fig. 12) are likewise rather feeble in structure, the basal part beg
comparatively short and forming a more or less pronounced angle with the terminal part.
The masticatory lobe arising from the basal part is almost quadrangular, and bears at the
base a very strong anteriorly curved seta. Of the joints belonging to the terminal part,
the antepenultimate is, as usual, the largest, and exhibits along the inner edge a series
of short curved spines, provided at one of their edges with a few slender denticles
(fiz. 14). Moreover, this joint has on the lower side numerous fine hair-like bristles,
partly arranged in fascicles, and at the outer corner a very long anteriorly curving seta,
densely ciliate at the outer part. Two similar, but somewhat shorter, sete are also
found originating from the succeeding joint. The last joint (see fig. 13) is very small,
sublinear, and provided at the tip with three bristles, one of which is quite short but
furnished with a few very long cilia on both edges.

The branchial apparatus (see fig. 15) affixed to the base of these limbs, is less fully
developed than in most other Cumacea. The epipodite-plate is rather narrow and has
only five small digitiform gill-lobules, the largest of which is affixed at some distance
from the inner edge and points posteriorly. The anteriorly directed narrow division of
the apparatus, representing the modified exopodite, is considerably longer than the
epipodite-plate and terminates in a somewhat dilated lanceolate plate bordered by a very
thin and pellucid membrane. In conjunction with the corresponding plate this part
forms an elongated tube, which admits of being exserted from the tip of the pseudo-
rostral projection, and serves for the expulsion of the water introduced into the branchial

REPORT ON THE CUMACEA. 37

cavities. During the rhythmical movements of the epipodite-plates, this tube remains
immovably exserted, but is immediately withdrawn when the movements are
interrupted.

The first pair of gnathopoda (fig. 16) do not exhibit any peculiarity in their
structure.

The second pair of gnathopoda (fig. 17), on the other hand, exhibit a form rather
different from that im most other Cumacea. Thus, the basal part is rather broad and
only very shghtly longer than the terminal part. It has several ciliated bristles along
the immer edge, and from its external corner four very strong anteriorly curving sete
originate, the outer of which especially is of quite unusual size and densely ciliate.
The terminal part is provided with comparatively short bristles, with the exception of
its second joint, which has externally a strong anteriorly curving seta similar to those
arising from the outer corner of the basal part. The exopodite is rather powerful, with
the basal part compressed, oblong, and the terminal composed of five articulations.

The first pair of legs (fig. 18) are about equal in length to the carapace and the two
anterior exposed segments of the trunk taken together, and are rather slender, tapering
gradually from the base to the tip. The basal joint is, as usual, somewhat dilated in its
proximal part, where it contains the strong muscles moving the exopodite, and is
fringed along almost the whole inner edge, and the distal part of the outer, with
ciliated bristles; moreover, a row of short spines occurs along the distal part at some
distance from the outer edge. The terminal part of the leg is much longer than the
basal, and is furnished with scattered plumose sete, especially along the outer edge. Of
the joints the antepenultimate and penultimate are the longest and about equal in size.
The last joint is shghtly compressed but rather narrow, and armed at the tip with about
six strong, claw-like spines. The exopodite has much the same appearance as that of
the second pair of gnathopoda, except that its terminal part has one joint more.

The second pair of legs (fig. 19) are much shorter than the first, but rather stout,
with the basal and terminal parts about equal in length. The ischial joint seems to be
quite wanting. The meral joint is rather thick and armed at the end on the inner side
with a strong spine. The carpal joint is about twice as long, but much narrower, and
has a similar, though somewhat smaller spine at the end. The propodal joint is quite
short and unarmed, whereas the terminal is rather elongate, linear, and furnished with
numerous stiff spine-lke bristles, forming a spreading bunch at the end of the joint.
The exopodite does not differ from that of the first pair of legs.

The third pair of legs (fig. 20) in both sexes are furnished with well-developed
natatory exopodites. The basal part of the endopodite is more than twice as long as the
terminal, and, as in the two preceding pairs, rather dilated to receive the strong
muscles moving the exopodite ; along both edges there are a number of ciliated sete.
Of the joints composing the terminal part, the three first slightly increase in size, and

38 THE VOYAGE OF H.M.S. CHALLENGER.

from the third (the carpal) three strong sete originate, the distal part of which is
densely annulated and curved at the end in a hook-hke manner. The propodal joint is
much smaller and has a single seta of similar structure, and from the tip of the very
minute terminal joint a slender spine originates, besides two very small bristles.

The two posterior pairs of legs in the female are simple, whereas in the male the
penultimate pair (fig. 21) have well-developed natatory exopodites, as on the anterior
pairs.

The last pair of legs (fig. 22) are quite alike in both sexes and very small, with the
basal joint narrow, cylindrical, and about as long as the terminal part. :

Of pleopoda only two pairs are present in the male, affixed to the two anterior caudal
segments (see fig. 1). These limbs (fig. 23) are not fully developed in the specimens
examined, though having the basal part and the two branches distinctly defined from each
other. The latter (fig. 24) are very short, and each of them is provided at the tip with four
still unciliated setze; the outer branch is biarticulate, whereas the inner is uniarticulate,
and, as in the male of Paralamprops, juts out in the middle to an angular projection
bearing a single auditory bristle.

The uropoda (see fig. 25) are rather stout and about as long as the two posterior
caudal segments taken together. The scape is cylindrical and furnished with scattered
spiniform bristles, especially along the inner edge. Of the branches, the inner is the
shorter and about as long as the scape. It is composed of two well-defined joints, the
first of which is more than twice as long as the last, and armed along the inner edge with
about twelve spines, three of which are much longer than the others; the last joint is
rather narrow and has five equal-sized spines along the inner edge, and two somewhat
larger ones arising from the tip. The outer branch is also biarticulate, but the first joint
is here very short, whereas the last is elongate and furnished along the inner edge with
a row of about ten ciliated sete, besides a few scattered bristles along the outer edge and
on the upper side.

Habitat.—A few specimens of this form were taken January 29, 1874, off Cumberland
Bay, Kerguelen Islands, from a depth of 127 fathoms (Station 149H).

7. Leucon tenwirostris, n. sp. (Pl. V. figs. 1-4).

Specific Characters.—Form of body extremely slender. Carapace with the antero-
lateral corners only very slightly produced, almost rectangular; anterior edges above
the corners denticulate, with a small sinus in the middle; dorsal crest armed with only
seven denticles arranged along its anterior half; pseudorostral projection very elongate
and slender, almost as long as the carapace, slightly ascending and regularly tapering to
the end. Inner flagellum of the antennule about as long as the first joint of outer.
The two anterior pairs of legs nearly as in the preceding species; the three posterior

REPORT ON THE CUMACEA., 39

pairs successively decreasing in length and densely beset with ciliated bristles. Uropoda
with inner branch longer than outer, first joint scarcely twice as long as second, both
armed with scattered denticles at inner edge. Length, 10 mm.

Remarks.—The present species is nearly related to Lewcon longirostris, described by
the author from an imperfect specimen procured during the Swedish Expedition in the
frigate “Josephine.” It may, however, easily be distinguished by the rather different
form of the pseudorostral projection, the length of which in proportion to the carapace
is also much greater.

Description.—The sole specimen procured is a young female, in which the marsupial
pouch has not yet been developed. Its lengthis about 10 mm. The form of the body (see
Pl. V. figs. 1, 2) is extremely slender, more so than in any other of the known species.

The carapace (see fig. 3) is distinctly compressed and of the usual form, with the
dorsal crest well marked, but denticulate only in its anterior half, the denticles being
rather few in number (seven), and hence more widely separated from each other. The
pseudorostral projection is quite unusually elongate and slender, almost equalling the
carapace in length, and tapers gradually to the tip, which is narrowly truncate. It is
somewhat ascending and has the lateral edges provided with a few scattered bristles and
a single small denticle behind the middle. The antero-lateral corners of the carapace are
less produced than in the preceding species and almost rectangular. The anterior edges
joining the pseudorostral projection are strongly denticulate and have a distinct rounded
sinus below the middle, from the bottom of which the rudimentary antennze are seen to
project. The inferior edges of the carapace form a slight angle at the middle and are,
as usual, strongly denticulate in the anterior half.

The five exposed segments of the trunk taper successively posteriorly, and the last of
them does not exceed the caudal segments, either in height or in breadth.

The tail is considerably longer than the anterior division of the body and very
slender. Its segments increase successively in leneth to the penultimate, which is by far
the longest. The last segment (see fig. 4), on the other hand, is quite short and almost
pentagonal, with the end produced to an obtusely triangular projection arching over the
anal orifice.

The antennulz (see fig. 3) are comparatively rather large, though not nearly reaching
to the tip of the pseudorostral projection. They are more especially distinguished by the
unusual development of the inner flagellum, which in this case cannot properly be said
to be rudimentary, since it fully equals in length the first joint of the outer one; it is,
however, as usual, composed of only a single joint, which bears at the tip several stiff
bristles,

The two anterior pairs of legs (see fig. 1) do not seem to differ materially from those
of the preceding species. This is also the case with the succeeding legs, with this
difference, however, that they are much more richly supplied with cilated bristles.

40 THE VOYAGE OF H.M.S. CHALLENGER.

The uropoda (see fig. 4) are comparatively a little longer than in the preceding species
and have the scape cylindrical, with but four denticles along the inner edge. Of the
branches, in this species the inner one is the larger and about as long as the scape.
Its first joint is scarcely twice as long as the last, slightly tapering, and provided along
the inner edge with only five denticles. The last joint is linear and has three denticles
along the inner edge anda much stronger one at the tip, besides another very small apical
denticle and a simple slender bristle. The outer branch is considerably shorter than the
inner and has the last joint provided with a series of ciliated setee along the inner edge.

Habitat.—The above described specimen was taken from a very considerable depth
in the North Pacific, at Station 246, July 2, 1875; lat. 36° 10’ N., long. 178° E.; depth,
2050 fathoms; Globigerina ooze ; bottom temperature, 35°'1.

Genus 2. Hudorella, Norman, 1866.

Eudorella Norman, Rep. Brit. Assoc., 1866, p. 197, note.
Eudora, Sp. Bate, Ann. and Mag. Nat. Hist., ser. 2, vol. xvii. p. 457.

Generic Characters—Anterior division of body more or less dilated, almost clavate.
Carapace comparatively small, not crested dorsally, truncated in front, without any
pseudorostral projection, the lateral lobes ascending perpendicularly and meeting
immediately in front of the median lobe, leaving between their extremities an oval
orifice for the expulsion of the water. No eye. Five segments of the trunk exposed
behind the carapace, rapidly diminishing in height posteriorly. Tail very slender and
movable. Antennule rather large, geniculate, outer part being reflexed and doubled
upon the inner by an elbow-like flexure ; ner flagellum well developed, uniarticulate,
with three strong apical bristles. Antenne in female very small, uniarticulate. Oral
parts and legs nearly as in Leucon. Telson wanting. Uropoda with both branches
biarticulate.

Remarks.—As regards the structure of the several limbs, this genus exhibits great
affinity to the genus Lewcon, though it is easily distinguished by the very different form
of the carapace, which gives to the species of the present genus quite a peculiar appear
ance. The strong development and peculiar curvature of the antennule affords another
good generic mark. No less than seven different species of this genus have hitherto
been distinguished. Of these, three occur in the Northern Ocean, one in the Arctic Sea,
two off the eastern coast of North America and two in the Mediterranean, one of which
is also found in the Northern Ocean. Besides these, an eighth species, which is
described below, was procured during the Challenger Expedition.

REPORT ON THE CUMACEA. 41

8. Eudorella abyssi, n. sp. (Pl. V. figs. 5-12).

Specific Characters.—Body moderately slender and beset with short scattered hairs.
Carapace almost perpendicularly truncate in front, with the upper part rounded; anterior
edges below the middle with a distinct rounded sinus limited by two obtu se projections,
the upper with three, the lower with five teeth ; antero-lateral corners obtusely angled.
First pair of legs, when fully extended, about as long as anterior division of body,
rather stout, and provided along outer edge of terminal part with elongate ciliated sete;
last joint compressed and armed with numerous claw-like spines; second pair with
terminal joint sublinear and provided with stiff radiating spines. Uropoda about as
Jong as the two last caudal segments taken together, inner branch much the longer, with
a regular row of short spinules along the inner edge, last joint very small, armed at the
tip with a strong spine and a slender bristle. Length, 9 mm.

Remarks.—In its general appearance this species is rather similar to the northern
form KEudorella truncatula, but may readily be distinguished by the rounded form of
the sinus on the anterior edges of the carapace, and by the different number of teeth
occurring on the cbtuse projections, which limit that sinus.

Deseription.—The sole specimen procured is an adult female with greatly developed
marsupial pouch. Jts length is about 9 mm.

The form of the body (see Pl. V. figs. 5, 6) is moderately slender, with the anterior
division considerably dilated, and, as seen from the side, almost club-shaped.

The carapace is comparatively short, scarcely occupying half the length of the
anterior division, and, as seen from the side, nearly quadrangular, the front part being
almost perpendicularly truncated, without any trace of a rostrum-like projection. Not-
withstanding this, the lateral lobes, usually forming the pseudorostral projection, are
present, but instead of projecting in front of the median lobe as usual, they ascend
perpendicularly and terminate close to that lobe, leaving between their extremities an
oval orifice (see fig. 6), through which the water is expelled from the branchial cavities.
The dorsal line of the carapace is almost horizontal and without any trace of a keel. The
inferior edges are densely serrate in their anterior half, whereas the posterior part is
smooth and obliquely ascending. ‘The anterior edges (see fig. 7) are in the upper part
quite smooth, but below the middle there occur two dentate projections limiting a rather
deep and rounded sinus, from the bottom of which the antenne project. Of these pro-
jections the upper is armed with three, and the lower with five strong teeth. The
antero-lateral corners of the carapace are obtusely angled, and armed with an anteriorly-
directed tooth, forming a continuation of the series of teeth occurring along the inferior
edges.

Not the shghtest trace of an eye can be detected, nor is any distinct ocular lobe

present.
(ZooL, CHALL. EXP.—PaRT Ly,—1887.) » hié

42 THE VOYAGE OF H.M.S. CHALLENGER.

The five segments of the trunk exposed behind the carapace rapidly diminish in
height posteriorly, and have all rather broad laminar epimera, somewhat projecting
laterally (see fig. 6). The first segment is very narrow, almost band-like, and the last
does not exceed the succeeding caudal segment either in height or in breadth.

The tail is very slender, considerably longer than the anterior division of the body.
The form and relative length of the segments are very nearly as in Leucon. As in that
genus the last segment is rather short and obtusely produced posteriorly.

The integuments are rather thin and without any distinct sculpturing, but beset with
scattered short hairs, especially on the tail.

The antennulz (see fig. 5) exhibit the structure and peculiar flexure characteristic of
the genus. They are rather stout and affixed to a fleshy segment lying immediately in
front of the upper part of the carapace, from which segment they, as it were, hang
down, forming a sharp elbow-like bend at the middle. This bend occurs between the
two outer joints of the peduncle, in such a manner that the last joint together with the
flagella is doubled upon the proximal part of the antennula, pointing obliquely
upwards. Of the flagella the inner one is fully as long as the first joint of the outer, but
only composed of a single joint bearing three strong spine-like bristles at the tip. The
outer flagellum is triarticulate and provided with several strong ciliated bristles,
especially along the edges of the first joint ; at the tip this flagellum bears the usual two
ribbon-like sensory appendages, which, however, are rather short, scarcely exceeding the
simple apical bristles in length.

The first pair of legs (fig. 8) are rather strong, projecting considerably in front of
the carapace, and when fully extended about as long as the whole anterior division of
the body. The basal joint is slightly curved and furnished on both edges of the distal
part with several ciliated bristles. The terminal part of the leg is considerably longer
than the basal and exhibits the usual well marked geniculate bends; it is furnished along
the outer edge with scattered and rather long sete, which are finely ciliate. Of the
joints the penultimate is the longest, whereas the terminal joint is comparatively short
and much compressed, with numerous claw-like spines at the obliquely truncated apex.
The exopodite does not reach to the end of the basal joint and has the terminal part
divided into five setiferous articulations.

The second pair of legs (see fig. 5) are comparatively stronger than in Lewcon, but
as in that genus only sex-articulate, the ischial joint not being distinctly defined. The
terminal joint is almost linear and provided with a number of diverging spines, arranged
in a double row.

The third pair of legs (bid.) have the exopodite well developed and of the same
structure as in the two preceding pairs, whereas the two posterior pairs (figs. 10, 11) are
simple and rather small, especially the last pair.

The uropoda (see fig. 12) are rather strong, fully as long as the two last caudal

REPORT ON THE CUMACEA. 43

seoments taken together, with the scape cylindrical and armed with a row of about
twelve small spines along the inner edge. Both branches are biarticulate, as in the
genus Leucon, and on the whole agree fairly well in structure with those in that genus.
The inner branch is much the longer, slightly tapering towards the tip and armed with
a regular row of denticles along the inner edge. Its terminal joint is very short and
has at the tip a strong spine and an elongate seta, besides four small denticles along
the inner edge. The outer branch is scarcely longer than the first jomt of the imner,
and has the basal joint rather short and obliquely truncate at the end, whereas the
terminal joint is elongate and somewhat compressed, with a row of about ten strong
ciliated setze along the inner edge and at the tip.

Hahitat.—The above described specimen was taken with the trawl from a very
considerable depth in the North Atlantic, off the coast of the United States.

Station 45, May 3, 1873; lat. 38° 34’ N., long. 72° 10’ W.; depth, 1240 fathoms ;
bottom, blue mud; bottom temperature, 37°'2.

Family V. Diastyiipa%.

The Cumacea referred to this family are easily known by the tumid and ovate form
of the anterior division of the body, which is sharply marked off from the slender and
very mobile tail; also by the large, superiorly strongly arched carapace terminating in
front in a more or less prominent rostriform projection, and finally by the distinctly
defined, lageniform telson, and the great length of the scape of the uropoda. The
family at present comprises only two genera, viz., Diastylis, Say, and Leptostylis, G. O.
Sars. Of these only the first is represented in the Challenger collection.

Genus Diastylis, Say, 1817.

Diastylis, Say, Journ. Acad. Nat. Sci. Philadelphia, 1817.

Condylura, Latreille, Le Régne Animal, t. iv. p. 153, 1829 (not Llliger).
Alauna, Goodsir, Edin. New Phil. Journ., vol. xxxiv. p. 130, 1843.

Cuma, Kroyer, Nat. Hist. Tidsskr., Bd. iii. p. 530, 1841 (not Milne-Edwards).

Generic Characters.—Form and armature of body generally rather dissimilar in the
two sexes, adult male always much more slender than female. Carapace large and
tumid, mostly spinous, antero-lateral corners obsolete, pseudorostral projection triangu-
larly pointed. Eye present or wanting. Antennule slender, peduncle only slightly
thickened in male. Antenne in female four to five-articulate, in male very fully
developed, attaining the length of the body, distal part of peduncle composed of
a single large segment with numerous fascicles of small sensory appendages along the
outer edge, flagellum very slender, with elongate articulations. First pair of legs more

44 THE VOYAGE OF H.M.S. CHALLENGER.

or less elongate, with the three outer joints very slender; second pair considerably
shorter and rapidly tapering toward the apex; third and fourth pairs in female without
basal appendages. Pleopoda of male distinctly biramose, outer branch biarticulate,
inner uniarticulate. Third and fourth caudal segments in male with four strong ciliated
setee in place of pleopoda. Telson rather large, with the terminal part more or less
produced and in the male forming a distinct angle with the basal part. Uropoda slender,
with the scape elongate, branches comparatively short.

Remarks.—This genus is chiefly distinguished from the genus Leptostylis by the
antennulz being far less dissimilar in the two sexes, by the much fuller development of
the male antennze, and by the third and fourth pairs of legs in the female wanting
the basal appendage (rudimentary exopodite) present in the former genus; finally,
by the somewhat different form of the caudal appendages. The genus is very
abundantly represented, especially in the Northern Ocean, no less than twenty-seven
distinct species having been hitherto recorded. The Challenger collection contains four
species, one of which has been formerly described, whereas the three others are now
added, increasing the number of species to thirty-one. The four Challenger species may
be easily known by the armature of the carapace and the form of the telson, as

follows :—

f f { very minute. Telson with terminal part
much longer than basal, and densely
denticulate at the edges, . : . Diastylis stygia, G. O. Sars.

subequal,
spinous; rather strong. Telson with outer part
ine spines much shorter than basal, and without
: lateral denticles, ; : ‘ . Diastylis erinaceus, n. sp.

Carapace
I unequal; some much larger than the others. Telson

comparatively short, with terminal and basal part
| about equal in length, . : : 0 ; . Diastylis horrida, n. sp.

finely scabrous, with a serrate crest on each side running obliquely
backwards from tip of pseudorostral projection. Telson with
terminal part shorter than basal and armed with but one pair of

| lateral denticles, ; : : : : é : : . Dirastylis mystacina, n, sp.

9. Diastylis stygia, G. O. Sars (Pls. VI., VIL, VIII.).

Diastylis stygia, G. O. Sars, Om Cumaceer fra de store Dybder i Nordishavet, K. Svensk.
Vetensk. Akad. Handl., vol. xi. p. 6, pl. ii. figs. 4-7.

Specific Characters.—Carapace about twice as long as the exposed part of trunk,
moderately tumid and armed (in female) with numerous small subequal spinules, more
crowded in the anterior part ; pseudorostral projection conical, scarcely longer than frontal
lobe; inferior edges of carapace denticulate in the anterior part only. No eye. Anterior
margin of the three first exposed segments of trunk finely denticulate. Tail in both sexes

REPORT ON THE CUMACEA. 45

smooth, without denticles. First pair of legs scarcely longer than carapace, with the
three outer joints subequal ; second pair with antepenultimate joint longer than the two
outer taken together. Telson rather elongate, with terminal part much longer than basal,
and densely spinous at both edges; apical spines not larger than lateral. Uropoda with
scape very slender, branches subequal, about half as long as scape, inner distinctly
triarticulate. Length of female, 16 mm., of adult male, 21 mm.

Remarks.—The present species was briefly described by the author in the year 1873,
from a single young female specimen obtained during the Swedish Spitzbergen Expedition
in 1868, from the very considerable depth of 2600 fathoms. During the Challenger
Expedition several specimens, both females and adult males, were procured, and I thus
have had an opportunity of making a closer examination of this form, to show the very
striking differences between the two sexes, as regards both the general appearance and
several of the anatomical details.

Description of the Female.—The length of the adult specimens is about 16 mm., and
the present form thus belongs to the larger species of the order. The form of the body
(see Pl. VI. figs. 1, 2) is rather stout, with the anterior division considerably dilated,
nearly ovoid in form, and sharply marked off from the slender tail.

The carapace is very large and deep, about twice as long as the exposed part of the
trunk, and nearly as broad as high. The dorsal surface is strongly vaulted in its
posterior part, declining anteriorly to the base of the pseudorostral projection. The
latter is conical in form and of moderate length, about as long as the frontal lobe. The
inferior edges of the carapace are somewhat irregularly arched, without forming any
distinct antero-lateral corners ; they are finely serrate in the anterior part, and join the
posterior edge without being defined from it by any distinct angle. The surface of the
carapace appears everywhere evenly arched, without any folds or keels, but is beset with
numerous small equal-sized spinules, more densely crowded in the anterior part.

The exposed part of the trunk consists of five well-defined segments, rapidly decreasing
in height posteriorly. The first segment is very narrow, almost band-like, and the three
succeeding segments only slightly increase in length, all these segments being firmly
connected with each other. The last segment is very small and rather movably connected
with the preceding, a space covered by thin skin being interposed dorsally between the two
segments. On all the segments the lateral parts form small rounded epimeral plates,
slightly projecting laterally. Those of the last segment are somewhat produced
posteriorly, without, however, forming acuminate projections as in the adult male. The
first three segments have the anterior margin very finely denticulate, and this is also the
case with the last segment, which also bears two small dorsal denticles.

The tail is scarcely longer than the anterior division of the body, but very slender
and cylindrical, with the posterior margin of the segments strongly emarginate both
dorsally and ventrally, and forming on each side a slight projecting angle. The three

46 THE VOYAGE OF H.M.8. CHALLENGER.

anterior segments are nearly equal in size, whereas the two succeeding somewhat increase
in length. The last segment is a little shorter than the preceding, slightly expanded at
the end and somewhat depressed. All the segments are quite smooth, without any trace
of spines or denticles.

The integuments, as in the other species of the genus, are rather strong and
calcareous, exhibiting under the microscope a finely reticulate structure.

The colour of the body is uniformly whitish, without any pigmentary deposits.

No trace of a distinctly developed eye can be detected, though a small rounded ocular
lobe is present at the end of the median lobe (frontal lobe) (see fig. 2).

The antennule (fig. 5, a') are rather slender, projecting considerably beyond the tip
of the pseudorostral projection. ‘They are composed of a triarticulate peduncle, and two
well-defined flagella. The first joint of the peduncle is very large, considerably longer
than the other two taken together, and also much broader. It is somewhat flattened
and finely ciliate along the inner edge; its end is obliquely truncate, and bears at
the inner projecting corner a very strong and densely hairy seta pointing anteriorly,
and at the outer a much smaller unciliated bristle, somewhat curved outwards. Of the
two outer joints of the peduncle, the first is the shorter, and has at the end internally a
ciliated seta of moderate size. The flagella are very unequal in size, the inner one being
very small, scarcely half as long as the last jomt of the peduncle. Nevertheless, this
flagellum is found to be composed of three well-defined articulations, the middle one of
which is the longest ; at the tip of the last joint three unequal bristles are affixed. The
outer flagellum is about three times as long as the inner, and composed of four articulations,
the three first of which are nearly equal in size, whereas the last is very small, and might
easily be overlooked. Besides two or three simple bristles, this flagellum bears at the
tip two slender ribbon-like sensory appendages, each divided into a number of short
regular segments.

The antenne (fig. 5, a’) have the form of simple, slightly tapering stems, about half
as long as the antennular peduncle, and somewhat curved outwards and forwards. Each
stem is composed of four well-defined articulations, and bears five strong, anteriorly
curved, plumose sete, two of which arise from the first articulation; of these setz the
one affixed to the penultimate articulation is considerably shorter than the others.

The anterior lip (fig. 5, L) constitutes a rounded lobe projecting immediately behind
the antennal segment. The free edge of this lobe is slightly emarginate in the middle
and finely ciliated.

The posterior lip (fig. 7) is considerably larger, but quite membranous, and, as usual,
consists of two lateral lobes united at the base. The lobes are irregularly oval and
have the inner corner slightly incurved, but without any teeth, whereas a fine ciliation is
found along the whole inner edge and part of the outer.

The mandibles (fig. 6) are strongly developed and rather similar in structure to those

REPORT ON THE CUMACEA. 47

in the genera Cyclaspis and Paralamprops, as described above. The strong adductor
muscles filling the concavity of the body are connected by a broad chitinous tendon, to
which two other diverging muscles are affixed posteriorly. The rotatory muscles
constitute several strong bundles arising from the inside of the carapace dorsally, and
joining successively a very long and slender tendon, which is affixed to the inner edge of
the body immediately behind the molar process (cf: Pl. VIII. fig. 1).

The first pair of maxillze (fig. 8) exhibit the usual two masticatory lobes, springing
from a rather thick and muscular basal part. The reflexed palp is distinctly developed,
and about as Jong as the outer masticatory lobe. It bears at the tip two diverging sete
of somewhat unequal length.

The second pair of maxillee (fig. 9) agree on the whole rather well in structure with
those in the genera Cyclaspis and Paralamprops, as described above.

The maxillipeds (Pl. VII. fig. 2) have the basal part rather large, and provided with
a ridge running along the lower surface and strongly denticulate in its anterior part.
The masticatory lobe exhibits the usual structure and has a row of ciliated sete continued
along the inner edge of the basal part. Of the joints composing the terminal part, the
second (carpal) is, as usual, the largest and rather expanded ; it has at the outer corner a
very strong and elongate plumose seta pointing anteriorly, and along the inner edge a
row of short, slightly curved spines, which are densely ciliated in the middle (fig. 4),
besides numerous, partly plumose bristles. The penultimate joint is much smaller, and
provided at the end with two strong anteriorly curving sete. The terminal joint, finally
(fig. 3), is conical, with two unequal spines at the tip, and one or two simple hair-like
bristles.

The branchial apparatus affixed to these limbs (fig. 1) is very fully developed, and
the epipodite-plate, especially, is very large and of a distinctly navicular form. The gill-
lobules are digitiform, and arranged in a slightly spiral series along a thin flexuous
lamella issuing from the inner edge of the epipodite-plate, and partly doubled over it.
They rapidly increase in length from behind forwards, the posterior lobules being very
small and knob-like; from the bottom of the concave surface of the epipodite-plate,
moreover, a single somewhat larger gill-lobule, pointing anteriorly, arises. The
exopodite is scarcely half as long as the epipodite, and constitutes a narrow anteriorly
directed plate, broadest at the base and gradually tapering to a narrow, somewhat curved
neck, which again expands into a triangular lamella bordered by a thin narrow membrane,
The inner straight edge of this lamella lies in close contact with that of the lamella of
the other side, both together forming an imperfect tube, which can be exserted beyond
the tip of the pseudorostral projection (cf: Pl. VIII. fig. 1), and serves for the expulsion
of the water introduced into the branchial cavities.

The first pair of gnathopoda (fig. 5) are rather slender and exhibit at the base, affixed
to the short coxal joint, a quadrangular lamella, to the posterior edge of which a dense

48 THE VOYAGE OF H.M.S. CHALLENGER.

row of very slender unciliated sete: are affixed. These setee, only found in the adult
female, successively increase in length from within outwards, and, together with those
on the other side, form a broad fan projecting within the marsupial pouch. The basal
joint is much longer than the other joints taken together, and exhibits on the lower
side a denticulate ridge similar to that on the maxillipeds. At the end this joint bears
some strong ciliated setze, and along the outer edge a regular series of bristles. The
terminal part apparently consists of but four joints, the ischial joint not being distinctly
defined. Of these joints the antepenultimate (carpal) is by far the longest and bears
at the outer corner, like the preceding joint, a ciliated seta of moderate length, and
along the inner edge a dense row of smaller sete. The penultimate joint is also
densely beset with bristles along the inner edge, and has also an unusually strong and
elongated seta affixed to the outer edge close to its base. The terminal joint, finally, is
quite small, conical in form, and provided with an apical claw-like spine besides some
small bristles.

The second pair of gnathopoda (fig. 6) are much larger, and possess the full number
of joints. The basal joint is more than twice as long as the terminal part, and strongly
curved, Along the outer half of the inner edge there is a dense series of ciliated
bristles, and from the outer slightly projecting corner four very strong anteriorly
directed plumose set arise. On the lower side this joint has a few scattered
denticles, and at the inner corner a somewhat stronger dentiform spine. Of the
joints composing the terminal part, the penultimate (propodal) is the longest and
rather slender, whereas the terminal is quite short and armed at the tip with several
curved spines. The exopodite affixed to the basal joint of these limbs scarcely exceeds
half the length of this joint, and has the terminal part divided into six setiferous
articulations.

The first pair of legs (fig. 7) are, when fully extended, about as long as the carapace.
The basal joint is very large, slightly tapering towards the end, and strongly curved at
the middle, with a dense series of ciliated bristles along the outer part of both the outer
and inner edges. Moreover, this joint is armed with several strong denticles, somewhat
irregularly arranged on the lower side, some of them, however, forming a regular series
along an elevated ridge close to the outer edge. Of the joints composing the terminal
part, the two first are rather short, whereas the three outer are very slender and almost
equal in length, forming with each other strong geniculate bends. The exopodite is
somewhat larger than that of the last pair of gnathopoda, and, moreover, differs by the
basal part being denticulate and setiferous along the outer edge, and by the terminal
part having two additional joints.

The second pair of legs (fig. 8) do not nearly attain the length of the first pair, and
taper rapidly towards the end. The basal joint is scarcely more than half as long as
that of the preceding pair, and only slightly curved. It exhibits along the lower side

REPORT ON THE CUMACRHA. 49

an elevated ridge, which in the anterior part is armed with four strong denticles and
some ciliated bristles issuing between the denticles. Along the inner edge, moreover,
a series of rather strong, ciliated setze are present, increasing in length anteriorly. The
ischial joint is distinctly defined though very short, and armed on the inner edge with
a strong denticle. From the inner edge of the succeeding jomt two similar denticles
arise. The antepenultimate joint is very slender and elongate, considerably longer than
the two outer joints taken together, and only provided with a few simple bristles. The
terminal joint is a little longer than the penultimate and conical in form, with some
hair-like bristles, the one issuing from the tip being the longest. The exopodite is
exactly of the same structure as that of the first pair of legs.

The three posterior pairs of legs (figs. 9-11) are all simple, without any trace of
exopodites, and of essentially the same structure. Of the joints the basal is by far the
largest, in the two anterior pairs even longer than all the others taken together. The
ischial joint is very short, scarcely longer than broad, whereas the two succeeding joints
are more elongate and about equal in size. The two last joints are suddenly very much
smaller, and taken together scarcely as long as the preceding joint. These legs are
rather richly supplied with ciliated bristles, especially along the inner edge. But there
is a number of bristles issuing from the outer part of the legs, which differ essentially
from the rest in being considerably stronger, unciliated, and terminating in a finely
annulated, somewhat curved point. Five such peculiarly modified bristles are present
on each leg, four of which arise from the outer corner of the antepenultimate joint, and
the fifth from the penultimate one. At the tip of the terminal joint is affixed a claw-
like spine and a simple bristle. As to the relative size of these legs, the two anterior
pairs are nearly of the same length, whereas the last pair (fig. 11) are considerably
smaller, chiefly on account of the shortening of the basal joint.

The marsupial pouch, as in other Cumacea, is composed of four pairs of large plates
arising from the bases of the second pair of gnathopoda and the three anterior pairs of
lees. They were fully developed in only one of the specimens, which was somewhat
crushed, and therefore selected for dissection. The marsupial pouch in this specimen
contained a number of embryos, of which I have figured one in four different aspects
(figs. 14-17), to be described below.

The telson (see fig. 12) is distinctly defined and about twice as long as the last
caudal segment. It has a rather narrow, lageniform shape, the basal part, containing
the terminal portion of the intestine, being somewhat dilated and cylindrical, whereas
the outer part is very narrow, gradually tapering, and nearly twice as long as the basal
part. At the junction between the two, on the lower side, the anal orifice occurs. The
basal part is quite smooth, whereas the terminal is armed at the edges with about nine
pairs of denticles, somewhat irregularly arranged, and at the tip with two denticles of a
quite similar appearance.

(ZOOL, CHALL. EXP,—PaRT Lv.—1887.) Ti 7

50 THE VOYAGE OF H.M.S. CHALLENGER.

The uropoda (7bid.) are very slender, about equalling in length the three last caudal
segments taken together, and are articulated to the last caudal segment somewhat in
front of the telson. The scape is narrow, cylindrical, slightly dilated at the end, and
reaches to about the tip of the telson; it exhibits a regular row of about sixteen
spinules along the inner edge. The branches are subequal in length and scarcely more
than half as long as the scape. The inner branch is composed of three distinctly
defined joints, the first of which is a little longer than the other two taken together.
All the joints are spinous at the inner edge, the number of spines in the specimen
examined amounting to fifteen (eight on the first, four on the second, and three on the
last jot); to the tip of the branch, moreover, a somewhat longer spine and a
simple bristle are affixed. The outer branch is only biarticulate, with the first joint
quite short, the last very narrow and gradually tapering, with a few small hair-like
bristles along the outer edge, and a somewhat longer seta issuing from the tip.

Description of the Adult Male.
males do not differ materially in their general appearance from the females, the adult

Whilst the young or not yet sexually mature

males of this and most other species appear so very dissimilar to the females, as easily to
be mistaken for distinct species, a fact that has caused much trouble in the synonymy
several spurious specimens having been introduced on account of this peculiar dissimi-
larity between the sexes.!

The adult male of the present species attains a much larger size than the female,
measuring 21 mm. in length. The form of the body (see Pl. VI. figs. 3, 4) appears
much more slender, the anterior division being far less vaulted and more oblong in
shape, and the tail also considerably more elongate.

The carapace is about twice as long as deep, whereas its height does not nearly
equal its breadth; it is consequently much more depressed than in the female, and its
dorsal line appears also more evenly curved and less abruptly declining to the base of
the pseudorostral projection. The latter is somewhat shorter than in the female, and
exhibits above, at the base, a concave space, into the bottom of which the ocular lobe
is received. On each side the anterior edges of the carapace form a somewhat projecting,
broadly rounded lobe, arching over the base of the antenns. These lobes are serrate at
the edge, and, moreover, beset with numerous short plumose bristles (see fig. 4). The
inferior edges of the carapace exhibit in the middle a strong, almest angular curvature,
and join the posterior margin at an obtuse angle. When viewed from above (fig. 4)
the side-edges appear strongly arched, on account of the great development of the

! The following is a list of such spurious species :—

1. Cuma angulata, Kroyer=Adult male of Diastylis rathkii (Kroyer).

2. Cuma brevirostris, Kroyer = Adult male of Diastylis edwardsti (Kroyer).

3. Diastylis spinosa, Norman= Adult male of Diastylis echinata, Spence Bate.
4. Diastylis strigata, Norman=Adult male of Diastylis rugosa, G. O. Sars.

5. Diastylis calwert, Norman = Adult male of Diastylis biplicata, G. O. Sars.

REPORT ON THE CUMACEA. 51

branchial regions, and the posterior part of the carapace considerably narrower than in
the female. As to the armature of the carapace, it differs materially from that in the
female by the almost complete want of the spinules, of which only a slight trace can be
observed in the most anterior part. Moreover, on the sides of the carapace, below the
middle, a distinctly marked keel runs from the postero-lateral corners forwards,
limiting the greatly swollen branchial regions below. This keel, found in all adult
males of the present genus, is in some species strongly denticulate throughout, and thus
gives the carapace a still more anomalous appearance.

The exposed part of the trunk is considerably narrower than in the female, and less
vaulted, whereas the epimeral plates are more distinctly defined and setose at the edges;
those of the last segment especially exhibit a rather peculiar form, each being produced
posteriorly to an acute point, and bearing at the outer edge four very strong and
densely plumose setze.

Of the caudal segments, the two anterior are somewhat thicker than the others, and
have, moreover, a serrate crest running along the ventral surface, the crest being also
continued along the last segment of the trunk. These segments are otherwise quite
smooth, without any dorsal denticles,

The antennule (Pl. VIII. fig. 1, a’; fig. 2) are comparatively stouter than in the
female, with the outer part of the peduncle less slender, and provided at the base of the
outer flagellum with a dense fascicle of delicate sensory filaments. The flagella are
nearly equal in length, and each of them has one joint more than in the female, a short
articulation being marked off at their base.

The antenne (fig. 1, a”; fig. 3) are greatly developed, and fully as long as the whole
body. The peduncle is strongly geniculate, with the proximal part consisting of four
short and somewhat irregular joints, connected together by rather oblique articulations;
it bears at the base three strong ciliated bristles curving anteriorly, two of which issue
from the second joint, and the third from the first. The distal reflexed part of the
peduncle constitutes a single, very large and slightly compressed segment, gradually
tapering to the apex, and provided along the outer edge with numerous fascicles of short
sensory bristles. Within this segment several strong muscles are seen converging to
the tip; by the aid of these muscles the flagellum is moved. The latter is extremely
slender and composed of very elongate articulations, each provided at the outer edge
with numerous fascicles of small sensory bristles of the same kind as those on the distal
part of the peduncle (see fig. 4).

The oral parts do not seem to differ materially from those in the female.

The branchial apparatus, on the other hand, is much more fully developed
(see fig. 1); the great number and peculiar arrangement of the gill-lobules being
especially remarkable. The gill-lobules also differ considerably in form from
those in the female, being distinctly lamellar, instead of digitiform (fig. 7). ‘They are

52 THE VOYAGE OF H.M.S. CHALLENGER.

densely crowded together, and arranged most regularly side by side in a row, forming a
double spiral along the membranous lamella, doubled over the concavity of the epipodite-
plate, so as anteriorly almost completely to fill up the concavity. As in the female,
they increase in size from behind forwards, but much more gradually (see fig. 6).

Of the legs, all but the last pair are provided with strongly developed natatory exopo-
dites, the basal part of which (see figs. 8-11) is remarkably broad and lamellar. In regard
also to the structure of the endopodal part of the legs some differences from that in the
female may be found. Thus, in the two anterior pairs (figs. 8, 9) the basal jomt is compara-
tively larger and more dilated in the proximal part, to receive the strong muscles moving
the exopodite. In the second pair (fig. 9) this joint is twisted in a peculiar manner, the
ridge running along the lower side being more elevated and strongly flexuous. More-
over, the penultimate joint of this pair of legs is markedly distinguished by its inner
edge being strongly denticulate or exhibiting a serrate crest, a condition quite absent
in the female. In the third and fourth pairs of legs (figs. 10, 11) the basal joint
exhibits a form quite dissimilar to that in the female, not being simple and cylindrical,
but considerably dilated in the proximal part, and at the base of the exopodite provided
with a number of very strong hairy sete. The last pair of legs (fig. 12) nearly agree
in the form and relation of the joints with those in the female, but are distinguished
by two unusually strong and densely hairy sete, arising from the outer edge of the
basal joint.

There are two pairs of well-developed pleopoda affixed to the two anterior caudal
segments (see Pl. VI. fig. 3). They consist (Pl. VIL. figs. 13, 14) each of a narrow
basal part divided into two unequal segments, and of two very short branches provided
with long natatory sete. Of these branches (fig. 13, @) the outer one is distinctly
biarticulate, and bears at the tip four setee, whereas the inner is uniarticulate and
provided with six sete, two of which are affixed to the inner edge; moreover, this
branch exhibits at the outer edge, close to the apex, a small projection bearing two
minute auditory bristles. Both pairs of pleopoda are essentially of the same structure,
with this difference, however, that the basal part of the first pair (fig. 13) is more richly
supplied with bristles. At each side of the pleopoda there are on the two anterior
segments a number of strong ciliated setze (see figs. 13, 14), and on the ventral surface
of the two succeeding segments four strong sete: likewise occur (see Pl. VI. fig. 3), as it
were, in place of pleopoda.

The telson (see Pl. VIII. fig. 15) is considerably more elongate than in the female,
and, moreover, readily distinguished by the strong geniculate flexure occurring anterior
to the middle (see also Pl. VI. fig. 3), whereby the basal part appears sharply marked
off from the terminal part. The latter is armed on each side with about fifteen ciliated
denticles, whereas in the female, as above stated, the number of denticles is only nine
on each side.

REPORT ON THE CUMACEA. 53

The uropoda (see Pl. VII. fig. 15) are very slender and about as long as the five
posterior caudal segments taken together. The scape is remarkably elongate, and pro-
vided at the inner edge with a great number of ciliated deuticles, somewhat unequal in
size. The branches exhibit a structure similar to that in the female, but the number
of denticles occurring along the inner edge of the inner branch is far greater, bemg no
less than twenty-seven, besides the terminal spine.

Nervous System.—In dissecting two specimens of this species, a male and a female,
I succeeded in isolating the greater part of the ventral ganglionic cord, and have
figured the most anterior part of this cord of the female specimen (PI. VII. fig. 13), and
the succeeding part from the male specimen (PI. VIII. fig. 5). The central part of the
nervous system in all Cumacea consists, besides the supracesophageal ganglion or brain
(visible in Pl. VII. fig. 1), of sixteen ganglia, ten of which belong to the anterior
division, and the six others to the tail. Of the former the three anterior (Pl. VII.
fig. 13), innervating the oral parts, are closely crowded together and almost confluent,
whereas the remaining seven ganglia (see Pl. VIII. fig. 5), belonging to the trunk, are
widely separated and connected by rather long double commissures. The three
posterior of these ganglia are, however, somewhat closer together than the four pre-
ceding, and the last ganglion is also a little smaller. Between each pair of the com-
missures connecting the six anterior ganglia of the trunk there is also a narrow median
cord, which at first sight has the appearance of another central commissure con-
necting the ganglia. On closer examination, however, this part is found to consist of
a continuous vessel running along the dorsal surface of that part of the nervous cord,
to which it is partly connected, and apparently representing the ventral artery. The
caudal ganglia (ibid.) are far less developed and only slightly dilated, whereas the
commissures are very long and slender. All the ganglia consist of two well-marked
symmetrical halves and give origin on each side to two or three strong nerve-trunks,
which soon ramify and enter the corresponding limbs. Another rather large nerve-
trunk is seen to issue from the commissures themselves, and seems to innervate the
musculature of the corresponding segment. The mandibles together with their com-
plex muscles are innervated by two strong nerves issuing from the oral commissures at
their junction with the ventral cord (see Pl. VIL. fig. 13), each nerve dividing succes-
sively into a great number of diverging branches (partly visible in Pl. VII. fig. 1).

Development.—As above stated, the female specimen dissected had the marsupial
pouch filled with embryos. These were all in the same rather early stage of develop-
ment (Pl. VII. figs. 14-17), merely forming rounded saccular bodies, lined by a
thin pellucid cuticle (the egg-membrane). On a closer examination several of the
limbs were found in their first stage of development, as rounded buds along the
strongly curved ventral surface. On the opposite side a slight sinus occurs, indi-
cating the dorsal curvature characteristic of the Cumacean embryos (fig. 14). The

a4 THE VOYAGE OF H.M.S. CHALLENGER,

tail (T) is as yet only represented by a slight rounded prominence limiting the above
mentioned sinus posteriorly, and not yet exhibiting any trace of appendages. The
anterior extremity of the embryo is considerably broader and more evenly rounded
than the posterior, and exhibits most anteriorly two rounded areas (0), which, from analogy
with the embryos of the Podophthalmia, may be regarded as the ocular plates, as yet
wholly separated, but afterwards becoming confluent and at last quite obliterated. Behind
these plates the anterior lip (L) can be distinctly traced, and further back the bipartite
posterior lip or metastoma (/), On each side of the anterior lip two transverse
prominences occur, representing the antennule (a') and antenne (a), the first of
which are the larger, and on each side of the posterior lip the mandibles (M) may be
traced as two rounded knobs. Further back two pairs of prominences, somewhat
different both from the preceding and succeeding ones, are seen, the anterior (m1)
being unequally bipartite, the posterior (m7) slightly tripartite at the free edge. These
prominences represent the two pairs of maxilla. Then follows a regular double series
of posteriorly pointing prominences, all of a quite similar appearance and unequally
bilobed at the end. The number of these prominences is seven pairs,’ of which the
first (mp) represent the maxillipeds, the two succeeding the two pairs of gnathopoda
(gn', gn”), and the four posterior (p!—p*) the four anterior pairs of legs, the last pair
not being formed until very late, even a considerable time after the young have left
the marsupial pouch. The two rounded lobes which all of these pairs of limbs exhibit,
may undoubtedly be regarded as the first indication of the two principal parts, the
endopodite and exopodite, and it is rather striking that even the first pair of gnatho-
poda, which never exhibit any trace of exopodites in the adult animal, do not differ in
this respect from the following limbs, and that, moreover, in all the embryos the two
posterior pairs (third and fourth pairs of legs) have also a similar bilobed form, although
these hmbs in the female are quite simple. Immediately above the oral region on each
side a curved ridge or slight fold (C) may be traced, representing the first indication of
the carapace, and within the area limited below by this fold a rounded cellular body (X)
occurs, Which ultimately becomes the liver, or cxeca of the stomach.

As may be seen from the above description of the embryo, the development of the
Cumacea differs materially from that of the Mysidz and other Podopthalmia in two
g, while still enclosed within the

ter
egg-membrane, a well-marked dorsal curvature, and secondly, by the last pair of legs

very important points; firstly, by the embryo exhibitin

not being formed until a considerable time after the young have escaped from the
marsupial pouch. In both these respects the Cumacea agree, on the other hand, very
closely with the Isopoda.

Habitat.—Kight more or less perfect specimens of this species were taken by the
dredge in the North Atlantic, off Nova Scotia, from a very considerable depth.

1 Jn fig. 14, by a mistake, eight such pairs have been indicated instead of seven.

REPORT ON THE CUMACEA. 55

Station 47, May 7, 1873; lat. 41° 14’ N. long., 65° 45’ W.; depth, 1340 fathoms ;
bottom, blue mud.

The species has also been taken during the Norwegian North Atlantic Expedition
in different places in the cold area.

10. Diastylis horrida, n. sp. (Pl. IX. figs. 1-8)

Specific Characters.— 3. Carapace not twice as long as the exposed part of
trunk, slightly depressed ; surface somewhat irregularly grooved and armed all over
with numerous spines, some of which are much larger than the others; pseudorostral
projection acute, a little longer than frontal lobe; inferior edges of carapace denticulate
in their whole length. No distinct eye. Free segments of trunk with transverse rows
of small spines; epimera strongly denticulate at the edges. Tail more or less densely
spinulous. Antennule with basal jomt of peduncle armed at the tip with two strong
spines, the smooth seta affixed to its outer corner remarkably long. First pair of legs
exceeding in length the carapace, terminal joint very slender and much longer than the
preceding ; second pair with basal joint strongly spinous, antepenultimate joint equalling
in length the two last taken together ; remaining legs rather slender, with basal joint
more or less densely spinous. Telson of moderate length, terminal part scarcely longer
than basal and densely denticulate at the edges ; apical spines much larger than laterals.
Uropoda not very slender, branches unequal, inner shorter than outer, and composed of
but two joints. Length, 11 mm.

Remarks.—The present species is easily known by the body being armed all over with
unequal spines, more densely crowded together on the carapace; by the great length of
the terminal joint of the first pair of legs, and finally by the structure of the caudal
appendages. In general appearance it would seem to be most nearly related to the
northern form, Diastylis lucifera (Kroyer).

Description.—Most of the specimens of this form contained in the collection are
still immature, but there are one or two female specimens which seem to be nearly
full-grown, since the marsupial pouch has been formed. The larger of these specimens
measures about 11 mm. in length.

The form of the body (see Pl. IX. figs. 1, 2) is rather stout, nearly as in the
northern form, Diastylis lucifera, to which species it would seem to bear a rather close
affmity. The anterior division of the body is oblongo-ovate, and of about the same
length as the posterior, with the dorsal surface rather evenly vaulted.

The carapace is comparatively smaller than in the preceding species, not nearly
attaining twice the length of the exposed part of the trunk. It is somewhat depressed,
the height not nearly equalling the breadth, and, as seen from the side (fig. [1),

56 THE VOYAGE OF H.M.S. CHALLENGER.

of irregularly triangular form, with the dorsal line gradually declining anteriorly, and
the posterior edge somewhat elevated in the middle. The pseudorostral projection is
rather produced and sharply pointed, a little longer than the frontal lobe, and quite
horizontal. The inferior edges of the carapace are strongly arcuate in the middle, and
densely denticulate throughout ; posteriorly they join the posterior edge without forming
any angle, and anteriorly they ascend more perpendicularly to the base of the pseudo-
rostral projection. As seen from above (fig. 2) the posterior half of the carapace is of
about uniform breadth, whereas the anterior rapidly tapers to a conical point. The
surface of the carapace is somewhat irregularly grooved, a slight furrow running
obliquely along each side from the frontal lobe backwards. It is densely armed all over
with sharp anteriorly directed spines, some of which are much larger than the others,
and rather regularly arranged on each side of the middle line, especially on the dorsal
surface. In young specimens the difference in size between the spines is still more
pronounced than in the adult. The eye would seem to be imperfectly developed, as
neither pigment nor distinct refracting bodies could be detected within the rounded
ocular lobe.

The five exposed segments of the trunk are rather sharply defined and armed with
scattered spines, forming more or less distinct transverse rows; on each segment two of
the spines arranged in pairs dorsally are somewhat larger than the rest. The epimeral
plates on all the segments are strongly denticulate at the edges; those of the last
seement are obtusely rounded.

The tail exhibits the usual slender form and the peculiar nodose shape of the seg-
ments characteristic of the present genus, Like the rest of the body, it is more or less
densely spinous, especially on the dorsal surface, the number of spines varying in
different specimens.

The antennule (see fig. 3) are rather slender, with the two outer joints of the
peduncle unusually elongate, and, taken together, considerably longer than the basal
jomt. The latter is armed on the lower surface at the extremity with two strong
spines, and exhibits, moreover, as in the preceding species, two sete, the inner pointing
anteriorly, and densely hairy, the outer recurved and quite smooth, and longer than
usual, Of the two outer joints of the peduncle, the first is by far the longer. The
flagella are comparatively small, the outer scarcely attaining the length of the last joint
of the peduncle, and the inner very minute, being about one-third as long.

The antennz (cbid.) are also somewhat smaller than in the preceding species, each
forming a regularly tapering stem divided into four articulations, each with a single
ciliated seta at the end.

The first pair of legs (fig. 4) are comparatively slender, and when fully extended,
considerably exceeding the carapace in length. The small coxal joint is bordered with
a row of strong denticles, and the curved and elongate basal joint also exhibits a number

REPORT ON THE CUMACEA. 57

of small denticles arranged along its outer part in three rows. The whole inner edge
of this joint, as also the greater part of the outer, is moreover provided with numerous
slender ciliated sete. The terminal part of the leg is considerably longer than the
basal, and has the two first joints comparatively short, and the three outer joits very
slender. Of the latter the two first are about equal in length, whereas the last jomt
is considerably more elongate, and provided along the inner edge with numerous short
bristles, and at the tip with a number of curved claw-like spines. The exopodite
exhibits the usual structure and has the basal part armed on the outer edge with a
row of about eight spines, besides a few slender sete.

The second pair of legs (fig. 5) are scarcely more than half as long as the first, and
have the basal jomt rather large, and armed on the lower side with numerous spines,
five of which form a regular row along the outer edge. The ischial and meral joints
have each two strong spines at the end. The carpal joint exhibits the usual slender
form and is devoid of spines, whereas a row of simple bristles occur along its inner
edge. The terminal joint is conical, and considerably longer than the propodal joint;
both taken together are about as long as the carpal joint.

The three posterior pairs of legs (figs. 6, 7) are rather slender, and more or less
spinous in their proximal part. Of the joints composing the terminal part, the meral
and carpal are the longest and about equal in length.

The telson (see fig. 8) is not very elongate, scarcely more than twice as long as the
last caudal segment. The basal part is regularly cylindrical, and in some specimens
armed along the dorsal surface with a median row of spines. The terminal part does
not exceed the basal in length, and tapers gradually to the tip, which is armed with
two very elongate spines; the edges are also densely spinous, but the spines are much
smaller than those springing from the tip.

The uropoda (bid.) are about half as long as the tail, with the scape rather slender,
and armed along the inner edge with about ten small denticles. The branches are
comparatively short, and somewhat unequal in length, the inner being considerably
shorter than the outer, and consisting of but two joints of nearly equal length. Both
joints are spinulose along the inner edge, the number of spines in the specimen dissected
being seven, besides the strong spine issuing from the tip of the branch. The outer branch
is more slender than the inner, and exhibits at the tip three equal-sized spiniform sete,
besides a row of very small bristles along the outer edge.

Habitat.—Of the present form several specimens were collected on January 29,
1874, off Cumberland Bay, Kerguelen Islands, from a depth of 127 fathoms, Station
1298.

(zoOL. CHALL. EXP,—PART Ly.—1887.) Ti 8

58 THE VOYAGE OF H.M.S. CHALLENGER.

11. Diastylis erinaceus, n. sp. (Pl. EX. figs. 9-14).

Specific Characters.— §. Carapace very large and tumid, surface evenly vaulted,
and armed with numerous equal-sized spines; pseudorostral projection of moderate
length; inferior edges of carapace denticulate in the anterior part only. No distinct
eye. Exposed part of trunk smooth, not attaining half the length of the carapace.
Tail very slender, slightly spinulose, the three anterior segments each provided dorsally
with a pair of somewhat stronger spines and four ciliated sete. Antennule with the
basal joint armed with a longitudinal row of spies, outer edge minutely serrate; second
joint nearly as long as basal; third much smaller. Antenne somewhat irregularly
twisted, with six strong ciliated sete arising from the middle part, and two unciliated,
curved sete at the extremity. First pair of legs very elongate, with basal joint strongly
spinous, carpal and propodal joints exceedingly elongate and nearly’ subequal, terminal
joint much smaller. Second pair of legs with carpal jomt twice as long as the two last
joints taken together. Meral joint of the three posterior pairs of legs much longer than
carpal. ‘Telson rather elongate, basal part regularly cylindrical and much longer than
terminal; the latter gradually tapering, with two small apical denticles ; lateral edge
of telson unarmed. Uropoda comparatively small, with the scape shorter than telson.
Length, 13 mm.

Remarks.—The present species would seem to be very nearly allied to Diastylis
josephine, described by the author, from the Swedish Atlantic Expedition. It differs,
however, by the carapace being relatively more tumid, and by its spines being equal-sized,
whereas in Diastylis josephine some of the spines are much longer than the rest.
Moreover, the exposed part of the trunk is not spinous as is the case in that species, and
the telson, though exhibiting a very similar form, wants the numerous denticles found
along the edges of the basal part in Diastylis josephine.

Description.—Of this form I have only had an opportunity of examining a single
female specimen, and the broken anterior part of another. The length of the perfect
specimen is about 13 mm,

The form of the body (see Pl. IX. figs. 9, 10) is that characteristic of the genus,
the anterior division being considerably dilated and sharply marked off from the slender
tail.

The carapace is very large and tumid, considerably broader than high, and more
than twice as long as the exposed part of the trunk, with the dorsal surface considerably
arched and gradually declining both anteriorly and posteriorly. The pseudorostral
projection is of moderate length, horizontally projecting, with the upper surface
somewhat depressed at the base, and the tip sharply pointed. The inferior edges of
the carapace are strongly curved at the middle, and finely denticulate im their anterior
part. As seen from above (fig. 10), the greatest breadth of the carapace occurs anterior

REPORT ON THE CUMACEA. 59

to the middle, the posterior part bemg slightly narrowed. The surface of the carapace
is rather evenly vaulted, without any keels or folds, but armed all over with numerous
spines, pointing for the most part anteriorly. These spines are all of nearly equal size
and, as in the preceding species, also continued along the lateral parts of the pseudorostral
projection. The eye seems to be quite wanting, and the ocular lobe is rather small
and depressed.

The exposed part of the trunk is considerably narrower than the carapace, and
quite smooth ; the epimeral plates are evenly rounded and likewise unarmed.

The tail is very narrow, and armed with scattered spines both laterally and dorsally.
The first segment has a strongly serrate keel running along the ventral surface, and
moreover exhibits dorsally, as do also the two succeeding segments, two somewhat
stronger spines arranged in pairs, and four ciliated sete issuing from the posterior edge.

The antennul (fig. 11) are rather slender, with the basal joint of moderate length,
and armed with a longitudinal row of strong spines running along the lower side towards
the inner corner, to which a strong ciliated seta is affixed; the inner edge of this joint
is minutely denticulate in the anterior part, but wants the usual unciliated bristle at the
end. The second joint of the peduncle is very slender and almost as long as the basal,
whereas the third joint is much smaller. The flagella exhibit the usual structure.

The antenne (figs. 12, 13) present at first sight a structure rather different from
that in other species, the joints being twisted in a peculiar manner so as only with
ditticulty to be counted. Moreover, the structure and arrangement of the sete are rather
anomalous. Thus, the two outer sets have assumed the character of strongly chitinous
filaments curved in a peculiar manner, and quite devoid of cilia, whereas the six other
sete are densely ciliated and crowded together in the middle part of the antenna, all
but one apparently issuing from a single joint (the second).

The first pair of legs (see fig. 9) are of very considerable length, exceeding, when
fully extended, half the length of the body. The basal joint is strongly spinous and
densely supplied with ciliated sete. The carpal and propodal joints are exceedingly
slender and elongate, and about equal in size, whereas the terminal is much shorter.

The second pair of legs have the carpal joint very slender and nearly twice as long
as the two last joints taken together.

The two succeeding pairs of legs are rather powerfully developed, about equal in
length, and with the meral joint unusually large, and more than twice as long as the
carpal joint.

The last pair of legs are much smaller and of the usual structure.

The telson (fig. 14) is rather large, about as long as the two last caudal segments
taken together, and exhibits in the greater part of its length a regularly cylindrical
form, the posterior third part only projecting beyond the anal orifice, and constituting
the terminal division. The latter is somewhat flattened and regularly tapering towards

60 THE VOYAGE OF H.M.S8. CHALLENGER.

the apex, which is narrowly truncate and armed with two small denticles, Excepting
these apical denticles, the telson is quite unarmed, and only provided with a few very
minute hair-like bristles at the edges.

The uropoda were partly broken in the specimen examined. They seem to have
been comparatively small, the scape not nearly attaining the length of the telson.

Habitat.—The above described specimen, as also the broken example mentioned
above, was taken in the North Atlantic from a very considerable depth.

Station 79, July 11, 18738; lat. 36° 21’ N., long. 23° 31’ W.; depth, 2025 fathoms ;
bottom, Globigerina ooze ; bottom temperature, 35°°9.

12. Diastylis mystacina, n. sp. (Pl. X. figs. 1-3).

Specific Characters.— ?. Anterior division of body greatly swollen. Carapace
exceedingly large and deep, with the dorsal surface boldly vaulted in the middle ;
pseudorostral projection of moderate length, bordered on each side by an elevated and
strongly dentate crest, continued along the anterior part of the carapace as a slightly
flexuous serrate keel; inferior edges of carapace densely serrate in the anterior half;
surface finely scabrous from very small microscopic spikes. No distinct eye. Anterior
edge of the two first exposed segments of trunk minutely denticulate ; penultimate
seoment with two longitudinal serrate keels dorsally. Epimeral plates of the anterior
segments finely serrate at the edges. Last segment of trunk and the three anterior
caudal segments each with a pair of small dorsal denticles. First pair of legs of
moderate length, terminal joint nearly as long as the preceding. The three posterior
pairs of legs very slender, with meral and carpal jomts about equal in size. Telson with
terminal part as long as basal, slightly tapering and armed with but one pair of lateral
denticles. _ Uropoda comparatively small, inner branch shorter than outer, and composed
of two articulations only. Length, 10 mm.

Remarks.—This very distinct species seems to be most nearly related to Diastylis
insignis, described by the author from the Swedish Atlantic Expedition, though easily dis-
tinguished by the peculiar dentate crest on each side of the anterior part of the carapace, as
also by the want of the strong lateral projections occurring on the carapace of that species.

Description.—The sole specimen contained in the collection is an adult female with
fully developed marsupial pouch. It measures about 10 mm. in length.

The general form of the body (see Pl. X. figs. 1, 2) is rather similar to that of
Diastylis insignis, the anterior division being greatly swollen and very sharply marked
off from the slender tail.

The carapace is exceedingly large and deep, about twice as long as the exposed part
of the trunk, with the dorsal surface boldly arched in the middle, and declining rather
abruptly posteriorly, and more gradually anteriorly. The pseudorostral projection is of

REPORT ON THE CUMACEA. 61

moderate length and deeply excavated above, being bordered on each side by an elevated
crest, which is continued along the sides of the anterior part of the carapace. These
crests are somewhat flexuous and strongly dentate in their anterior part, some of the
denticles being considerably larger than the rest, and the two anterior occupying the tip
of the pseudorostral projection. The inferior edges of the carapace are strongly arcuate
in the middle, and finely serrate along their anterior half. As seen from above (fig. 2),
the carapace appears very tumid, the greatest breadth occurring a little posterior to
the middle, and distinctly exceeding the height. The surface is evenly vaulted, and
everywhere minutely scabrous from numerous very small microscopic spikes. The eye
seems to be quite wanting, though the rounded ocular lobe is distinctly seen at the end
of the bell-shaped frontal lobe (see fig. 2).

The exposed segments of the trunk are rather sharply marked off from each other,
their dorsal part being more or less elevated. The anterior edge of the two first
segments is very finely denticulate. The antepenultimate segment has a slight
transverse keel above, armed with a few small denticles, and on the dorsal surface of
the penultimate segment two short longitudinal serrate keels occur, The last segment
is very small and provided with a pair of dorsal denticles. The epimeral plates of the
four anterior segments are evenly rounded and finely denticulate; those of the last
seoment are obtusely produced posteriorly.

The tail is very slender, and about as long as the anterior division of the body. It
is quite smooth, with the exception of a pair of small dorsal denticles occurring on each
of the three anterior segments.

The first pair of legs (see fig. 1) are of moderate length, with the basal joint strongly
spinous, the three outer jomts rather slender and slightly decreasing in length.

The second pair of legs have also the basal joint densely armed with spines and
seem on the whole to agree in form with those of the preceding species.

The three posterior pairs of legs are very slender, with the meral and carpal joints
subequal.

The telson (see fig. 3) about equals in length the two last caudal segments taken
together. Its basal part is regularly cylindrical; the terminal part, projecting beyond
the anal orifice, is nearly of the same length, and gradually tapers to the apex, which
bears the two usual spines. Of lateral spines there are in the specimen examined only
a single pair at a short distance from the apex, besides a very minute denticle occurring
on the left side immediately in front of the lateral spine.

The uropoda (¢bid.) are not very large, scarcely exceeding the length of the three
posterior caudal segments taken together. The scape does not nearly attain the length
of the telson, and wants every trace of denticles on the inner edge. The branches are
rather unequal in size, the inner one being considerably shorter than the outer, and
about half as long as the scape. This branch is composed of but two joints of about

62 THE VOYAGE OF H.M.S. CHALLENGER.

equal length, the last conical in form and terminating in a strong spine; of lateral
denticles there are only three (one on the first and two on the last joint). The outer
branch exhibits the usual form, its terminal joint being rather slender and provided
with a few small hair-like bristles on both edges, and a somewhat stronger apical seta.

Habitat.—The above described specimen was taken together with the precedin
form at Station 79, July 11, 1873; lat. 36° 21’ N., long. 23° 31’ W.; depth, 202
fathoms ; bottom, Globigerina ooze ; bottom temperature, 35°79.

o
oO
o

Family VI. Cume.im2.

The Cumacea comprised within this family are generally very small, and at once
distinguished by the very slender form of the three posterior pairs of legs, which more-
over terminate in a strong curved claw. They also differ considerably from the
Cumacea belonging to the preceding families, by the male wanting every trace of
pleopoda, The family comprises two distinct genera, easily recognisable by the very
different structure of the visual organ, viz., Cumella, G. O. Sars, and Nannastacus,
Spence Bate. Moreover, I am inclined to regard the genus Spencebatea, established by
Norman, on a single male specimen procured by the “ Porcupine ” expedition, as belonging
to this family. Of these three genera only the genus Nannastacus is represented in
the Challenger collection,

Genus Nannastacus, Spence Bate, 1865.

Nannastacus, Spence Bate, Carcinological Gleanings, No. 1, Ann. and Mag. Nat. Hist., 1865.
Diops, Paulisona, Tzsljedovanija rakoobraznjikh krasnago morja, p. 128, 1875.

Generic Characters.
corners more or less produced. Eyes distinctly separated, with well-marked visual
elements. Antennulze with one of the flagella rudimentary. Antenne in female very
minute, uniarticulate, and provided with three strong hairy sete, in male shorter than
body. First pair of legs with terminal part slender and strongly geniculate; second
pair much shorter. The three posterior pairs of legs very slender and nearly equal in
length; terminal claw very strong. Uropoda with the branches very unequal, inner
much larger than outer, and composed of a single joint, strongly spinous at the inner

Carapace large, not cristated above, with the antero-lateral

edge.

Remarks.—This genus, established by Spence Bate for the reception of a peculiar
little Cumacean—described by the same author at an earlier date as Cuma unguieulata—
is chiefly distinguished by the eyes being widely separated, and never, as in the other
Cumacea, confluent. In other respects it comes very near to the genus Cumella.

REPORT ON THE CUMACEA. 63

Besides the typical species, Nannastacus unguiculatus, Spence Bate, another very
distinct species, Nannastacus longirostris, has been described by the author from the
Mediterranean, and a third species from the Challenger Expedition is now added.

13. Nannastacus suhmi, n. sp. (Pl. X. figs. 4-5).

Specific Characters.—Form of body rather stout, especially in female. Carapace
very large, more than twice as long as the exposed part of trunk; dorsal surface evenly
vaulted, without any spines or projections; posterior part somewhat gibbous; antero-
lateral corners greatly produced, but terminating in a blunt point; pseudorostral
projection in female tubular and obliquely ascending, in male very short and rounded.
Eyes with three well-defined corneal facets, much larger in male than in female. Legs
nearly as in Nannastacus unguiculatus. Uropoda with the scape very short, inner
branch elongate, outer exceedingly minute. Length scarcely exceeding 2 mm.

Remarks.—This form is very nearly related to the typical species, Nannastacus
unguiculatus, Spence Bate, but may readily be distinguished by the female wanting
every trace of the peculiar laminar spines adorning the carapace, as well as the epimeral
plates of the exposed segments of the trunk in that species. Moreover, the antero-
lateral corners are not sharply poimted but blunt at the tip, and these corners in the
male are comparatively more produced than in the male of Nannastacus unguiculatus.

Description—All the specimens of this form contained in the collection, having
been mounted together in Canada balsam on a glass-slide, a closer examination of
the anatomical details could of course not be instituted. Among the specimens
there is but a single female, the rest being males. The length of the body does not
exceed 2 mm.

The form of the body (see Pl. X. figs. 4, 5) is rather short and stout, though a little
more slender in the male (fig. 5) than in the female (fig. 4), with the anterior division
somewhat longer than the posterior and rather dilated, especially in the female.

The carapace is somewhat differently shaped in the two sexes. In the female
(fig. 4) it is very large and tumid, with the dorsal surface boldly arched and distinctly
gibbous in the posterior part. The pseudorostral projection is rather prominent,
forming a narrow tubular process, which ascends obliquely in front and is tipped with
small bristles. The antero-lateral corners of the carapace are greatly produced in the
form of conical processes, terminating in a blunt point. Between these processes and
the pseudorostral projection there is a broad shallow emargination, from the bottom of
which the antennulz are seen projecting. The inferior edges of the carapace form
together with the posterior an uninterrupted oblique curve, and are finely denticulate
in the anterior part. In the male (fig. 5) the carapace is comparatively much shallower,
with the dorsal line almost horizontal, and the pseudorostral projection far less

64 THE VOYAGE OF H.M.8S. CHALLENGER.

prominent and obtusely rounded. The antero-lateral corners are also less prominent,
though distinctly projecting, and the inferior edges are irregularly flexuous, and through-
out smooth. The surface of the carapace in both sexes is quite even, without any trace
of crests or spines, except a few small denticles on the posterior gibbous part, more
distinct in the female.

The eyes, as in the two other known species of the genus, are widely separated, and
located on each side of the frontal lobe at the base of the pseudorostral projection.
Each of them exhibits a distinct ocular pigment and three strongly projecting corneal
facets, much larger in the male than in the female.

The exposed part of the trunk is scarcely more than half as long as the carapace,
and composed of five well-defined segments, the first of which, however, is very narrow,
The epimeral plates are evenly rounded and quite smooth.

The tail is very slender in both sexes, with the penultimate segment the longest.
The last segment is produced in the middle posteriorly to an obtuse angle. In the
female a few very small denticles occur on the dorsal surface of each segment, whereas
in the male all the segments are quite smooth.

As to the colour of the specimens freshly mounted in Canada balsam, the female
specimen is rather pellucid, with only a few dark brown patches, one of which occurs on
each side of the carapace close to the inferior edge, another across the penultimate
caudal segment (see fig. 4). In the male the whole carapace, as also most of the body,
is of a much darker brownish hue. In both sexes a dark transverse band is observed
on the first pair of legs occupying the meral jomt, and also on the second pair of
enathopoda a similar band occurs.

The antennul are quite similar in the two sexes, and rather slender, with one of
the flagella very small and knob-shaped.

The antennz of the adult male (see fig. 5) are much shorter than the body, and
scarcely reach beyond the third caudal segment. The distal part of the peduncle is
distinctly biarticulate and densely beset along the lower edge with rather slender sensory
bristles. The flagellum is very narrow and composed of much elongated joints.

The first pair of legs are about as long as the carapace, with the carpal and pro-
podal joints rather slender and subequal, and the terminal considerably shorter.

The second pair of legs are much shorter than the first, with the terminal joint
linear and provided with a few stiff bristles on both edges and at the tip, the latter
being the longest.

The exopodites of these two pairs of legs, as also of the second pair of gnathopoda,
are remarkably small, especially in the female, with the basal part not at all dilated.

The three posterior pairs of legs are in the female simple, without any trace of
exopodites, and very slender, considerably longer than the second pair, and about equal
in length. They are almost quite naked, and have the carpal and propodal joints very

REPORT ON THE CUMACEA. 65

elongate. The terminal joint, together with its apical spine, forms a strong biarticulate
curved claw.

In the male the two anterior of these pairs of legs are provided with well-developed
natatory exopodites, as in the preceding legs, and hence the basal joint of these legs is
considerably dilated to receive the strong muscles moving the exopodite. The last
pair of legs, on the other hand, exhibit a slender form quite similar to that in the
female.

The pleopoda are quite wanting in both sexes.

The uropoda have the scape unusually short and the branches very unequal, the
outer one being exceedingly small, though consisting of two well-defined joints. The
inner branch, on the other hand, is rather elongate, especially in the male, uniarticulate,
and provided with several small denticles along the inner edge, and a slender spine at
the tip.

Habitat.—No less than eleven specimens of this little Cumacean were collected by
the late Dr. v. Willemoes Suhm, on October 27, 1874, off Samboangan, Philippine
Islands, and preserved by him in the above mentioned manner. All the specimens
were taken at the surface of the sea with the aid of the tow-net.

Family VII. Campy Laspip.

This family in many essential points differs considerably from the other families, both
as to the external appearance and the anatomical details. The enormous development
of the carapace affords a good external character. Of the anatomical details the very
peculiar structure of the oral parts may be noted, as also of the maxillipeds and the
first pair of gnathopoda. As to the legs, the first pair are not, as in other Cumacea,
distinguished by any considerable length, being on the whole, both im size and
structure, very similar to the second pair of gnathopoda. Also in the internal organisa-
tion there would seem to exist essential differences from other Cumacea. Thus, I
have found the liver to consist of only a single pair of very large ceca, instead of
_ three pairs, as in the genus Diastylis. The family comprises as yet but a single

genus, Viz.:—

Genus Campylaspis, G. O. Sars, 1864.
Campylaspis, G. O. Sars, Om den aberrante Krebsdyreruppe Cumacea og dens nordisk Arter, p. 75.

Generic Characters.—Carapace strongly vaulted above, with the anterior part
more or less depressed and produced ; pseudorostral projection very short, obliquely
truncate ; inferior edges of carapace unarmed. Ocular lobe more or less produced along

(ZOOL. CHALL. EXP.—PART Ly.—1887.) Thi 9

66 THE VOYAGE OF H.M.S. CHALLENGER.

the upper side of the pseudorostral projection ; visual elements imperfectly developed.
Exposed part of trunk very short, though composed of five well-defined segments.
Segments of tail keeled laterally. Antenne in male attaining the length of the body.
First pair of legs comparatively short, not projecting in front of carapace; second pair
rather stout, with terminal joint very elongate and linear; the three posterior pairs of
legs successively decreasing in length and only sparingly supplied with bristles. Inner
branch of uropoda considerably larger than outer, with inner edge spinous.

Remarks.—The species of the present genus are easily known by the exceedingly
large and vaulted carapace, which in most of the species exhibits a very marked sculpture,
partly in the form of keels and partly as variously shaped protuberances. As to the
limbs, the comparatively small size of the first pair of legs also furnishes a marked
and characteristic feature. No less than ten species belonging to this genus have been
described, seven of which occur off the Norwegian coast, two in the Mediterranean, and
one in the West Indian Archipelago. Two new species are now added from the
Challenger Expedition,

14. Campylaspis pacifica, n. sp. (Pl. X. fig. 6).

Specific Characters.— 9. Carapace enormously developed, occupying more than
half the length of the body, and being produced posteriorly so as to arch over the
exposed part of the trunk; dorsal surface boldly vaulted; anterior part only slightly
produced ; pseudorostral projection very short ; subrostral notch rather shallow. Sur-
face of carapace without any keels or protuberances, but slightly uneven dorsally.
Ocular lobe rather broad, containing a whitish eye-pigment. Penultimate caudal seg-
ment entire, not subdivided. Uropoda very elongate, attaining the length of the four
posterior caudal segments taken together, branches scarcely half as long as_ scape.
Length, about 3 mm.

Remarks.—The present species seems to be most nearly related to the Mediterranean
form, Campylaspis glabra, G. O. Sars, from which it however differs by the somewhat
more slender form of the body, by the carapace being slightly uneven dorsally, by the
shorter pseudorostral projection, and by the presence of a distinct, though rather shallow
subrostral notch.

Description.—I have only had an opportunity of examining a single female
specimen of this form. The specimen, which had been mounted in Canada balsam, is
fairly well preserved, and measures in length about 3 mm.

The form of the body (see Pl. X. fig. 6) is comparatively somewhat more slender
than in most of the other species, with the anterior division greatly dilated and some-
what longer than the posterior, if the uropoda are excepted.

The carapace is of quite a prodigious size, occupying more than half the length of

REPORT ON THE CUMACEA. 67

the body, and being produced posteriorly so as to arch over nearly the whole exposed
part of the trunk. The dorsal surface is boldly arched, with the strongest curvature
occurring in the posterior part, whence the dorsal line declines quite gradually anteriorly,
and more abruptly posteriorly. The pseudorostral projection is very short and obliquely
truncated, with the upper corner slightly projecting; beneath it, on each side, oceurs a
distinct though rather shallow sinus, limited below by an obtuse angle. The inferior
edges of the carapace are quite unarmed and rather curved in the middle, their posterior
part ascending obliquely and without any angle joining the posterior edge, which is
also oblique. The surface of the carapace wants any trace of keels or distinct pro-
tuberances, but appears somewhat uneven in the dorsal part; it exhibits under the
microscope a finely granular structure produced by numerous small depressed pits.
The ocular lobe is rather broad and contains within it an accumulation of whitish eye-
pigment, whereas distinctly developed refracting bodies seem to be quite wanting.

The exposed part of the trunk is very short, and is to a great extent hidden by
the posterior projecting part of the carapace. It seems to be composed, as in the other
species, of five segments, but only the three posterior segments appear quite distinct
in their whole circumference, The epimeral plates of all the segments are evenly
rounded and slightly projecting laterally.

The tail is rather slender, with the segments sharply marked off from each other
and provided with a slight lateral keel. They increase successively in length to the
penultimate, which is the longest. The last segment is considerably shorter, and pro-
duced at the end to an obtuse angle.

The colour of the freshly mounted specimen is a uniform brownish-red.

As to the limbs of the anterior division, a closer examination could not of course
be made in the sole specimen before us. They, however, seem to agree fairly well with
those in the succeeding species, as described below.

The uropoda are rather elongate, about equalling in length the four posterior caudal
segments taken together. The scape is very slender, more than twice as long as the
branches, and quite smooth. The inner branch is composed, as in the other species of
the genus, of a simple segment, armed on the inner edge with a few denticles, and at
the tip with a strong spine. The outer branch is distinctly biarticulate, but consider-
ably smaller than the inner, and provided at the tip with a slender seta.

Habitat.—The above described specimen was taken by the late Dr. v. Willemoes
Suhm, at the surface of the sea, on October 27, 1874, off Samboangan, Philippine
Islands, and was mounted together with the specimens of Nannastacus suhmii on the
same glass-slide,

68 THE VOYAGE OF H.M.S. CHALLENGER.

15. Campylaspis nodulosa, n. sp. (Pl. XL).

Specific Characters.— ?. Carapace scarcely attaining half the length of the body ;
posterior part not produced over the anterior segments of trunk; dorsal surface evenly
vaulted in the posterior part and obliquely declining anteriorly ; pseudorostral pro-
jection rather produced; subrostral notches distinctly defined. Surface of carapace
everywhere provided with rounded nodiform protuberances. Ocular lobe oval. Pen-
ultimate caudal segment subdivided by a transverse sulcus. First pair of maxillee
with the palp bisetose ; second pair with eight sete. Terminal joint of second pair
of legs scarcely longer than carpal joint. Uropoda comparatively short, about half as
long as the tail, scape rather strong, slightly serrate on both edges; inner branch only
slightly shorter than scape, serrate on inner edge, and armed with five spines, two
lateral and three apical; outer branch a little shorter than inner, with two unequal
setee at the tip. Length, nearly 5 mm.

Remarks.—Of the earlier known species the Norwegian form, Campylaspis
verrucosa, G, O, Sars, would seem to be the one most nearly related to the present
species, at least as regards the sculpture of the carapace. In other respects, however,
the two species are very easily distinguishable from each other.

Description.—I have had for examination four specimens of this form, all of exactly
the same size, and having the general appearance of females. But in all specimens the
last pair of legs are quite wanting, a fact that would seem to prove the specimens to be
still immature, although their size is not inferior to that of adult specimens of other
species, and considerably larger than that of the form described above, which un-
doubtedly is full-grown. In dissecting one of the specimens, I have found all the
remaining limbs well developed and of a structure very similar to that in adult
specimens of other species. The length of the specimens is nearly 5 mm.

The form of the body (see Pl. XI. figs. 1, 2) is that characteristic of the genus, the
anterior division being greatly dilated and somewhat longer than the posterior.

The integuments, as in other species, are very strongly indurated and exhibit on
the several limbs a more or less pronounced squamous structure.

The carapace is very large, though not nearly attaining the enormous development
of the preceding species. In a lateral view (fig. 1) it exhibits a somewhat irregular
oval form, with the dorsal line forming a bold curve rather abruptly declining anteriorly.
The pseudorostral projection is somewhat more produced than in the preceding species,
and the notch beneath it deeper and limited below by a distinctly projecting process.
The inferior edges of the carapace are evenly curved in their anterior part, whereas the
posterior part is slightly sinuous and obliquely ascending. The posterior edge is almost
perpendicularly truncate and joins the inferior without forming any distinct angle.

As seen from above (fig. 2) the carapace exhibits a rather regular oviform shape, the

REPORT ON THE CUMACEA. 69

greatest breadth, which about equals the height, occurring posterior to the middle.
The surface of the carapace is evenly vaulted, without any keels or excavations, but
exhibits a number of well-marked, rounded, nodiform protuberances, distributed rather
evenly, dorsally as well as laterally, the most anterior part alone being nearly smooth.
The ocular lobe is rather large and of oval form, but seems to want distinctly developed
visual elements.

The exposed part of the trunk is not, as in the preceding species, arched over by
the posterior part of the carapace, all the segments being distinctly visible in their
whole circumference. They are rather sharply defined, with the posterior edge much
elevated. The last segment does not differ either in size or in form from the anterior
caudal segments, and, like these, is without any trace of limbs.

The tail is somewhat shorter than the anterior division of the body, with the
seements marked off from each other by deep constrictions. They are slightly keeled
laterally, and the penultimate segment exhibits, moreover, posterior to the middle, a
transverse sulcus, so that it is, as it were, subdivided into two segments. The last
segment (see fig. 21) is, as usual, somewhat dilated posteriorly and of pentagonal form,
the posterior edge being produced in the middle as an obtuse angle.

The colour of the specimens, preserved in spirit, is whitish, with patches of brownish-
red, but may have been in the fresh specimens more uniformily reddish, as several
northern forms acquire a quite similar spotted appearance by the action of the spirit,
though originally more uniformly coloured.

The antennulz (fig. 3), which project anteriorly from the subrostral notches (see
fig. 1), are of moderate length, with the first joint of the peduncle strongly curved and
somewhat shorter than the two others taken together. Of the latter the first is con-
siderably larger than the second. The outer flagellum (see fig. 4) is well developed
and composed of three joints, the last of which, however, is exceedingly minute and
might be easily overlooked. It is provided at the tip with the two usual ribbon-like
sensory appendages, besides a slender seta; moreover, a small auditory bristle is found
affixed to the last jomt. The inner flagellum is exceedingly minute, but on closer
examination it is found to be composed of two well-defined joints, the last of which is
provided at the tip with two diverging auditory bristles.

The antenne (figs. 5, 6, a”) are quite rudimentary, constituting a simple, strongly
indurated, conical prominence, divided into two segments and without any trace of
bristles or spines.

The anterior lip (figs. 5, 6) is comparatively large and of a rather peculiar shape,
forming a broad quadrangular plate projecting anteriorly between the antennz as a
rounded nodulose protuberance, and having the posterior edge sharp and_ broadly
incised in the middle.

The posterior lip (fig. 7) is scarcely larger than the anterior, and of a very delicate

70 THE VOYAGE OF H.M.S8. CHALLENGER.

and fragile structure, so as only with great difficulty to be separated from the sur-
rounding parts. It consists as usual of two membranous lobes connected at the base,
each lobe exhibiting an irregular oval form, with the inner corner produced to a small
somewhat incurved poimt. The inner edge of the lobes and part of the outer are
finely ciliated.

The mandibles (figs. 8, 9) exhibit a structure essentially differing from that of all other
known genera of Cumacea. They are not very strong, with the body oblong and on the
inner side forming a rounded expansion, to which the chitinous tendon of the rotatory
muscles is affixed. The anterior branch (see fig. 10), forming the direct continuation
of the body, is slightly incurved and somewhat compressed, terminating in a strongly
dentate, oblique, cutting edge. On the mght mandible this edge is simple and armed
with six teeth, increasing in size internally; on the left mandible, on the other hand,
the edge appears double, a secondary bidentate plate occurring in juxtaposition to the
principal plate. At some distance posterior to the cutting edge there is a densely
crowded series of strong denticulate spines, six on the right and four on the left
mandible. The posterior branch or the molar process is very unlike that im other
Cumacea, constituting an exceedingly narrow and somewhat flexuous styliform projection,
terminating in a sharp point and bearing a few small denticles along the anterior edge.

The first pair of maxille (fig. 11) are unusually strong, with the basal parts very
massive and partly connected at the base. The outer masticatory lobe is rather broad
and strongly incurved, with the extremity abruptly truncated and armed with numerous
powerful spines, some of which are finely dentate on one of the edges. The posterior
masticatory lobe is considerably smaller and somewhat tapering, with the extremity
narrowly truncate and armed with five spmes, the three median rather strong and
densely ciliated. The palp, which as usual points straight backwards, is very slender
and elongate, and bears at the tip two unequal setze.

The second pair of maxilla (fig. 12), unlike those of the first pair, are poorly
developed, forming simple membranous plates, without any trace of the usual bifid
palp. The inner slightly produced part, representing the masticatory lobe, is provided
with eight bristles, the posterior of which is somewhat removed from the rest and
densely ciliated.

The maxillipeds (fig. 14) are likewise imperfectly developed, the terminal part
appearing at first sight to be represented by only a single oval and lamellar joint,
finely ciliated along the outer edge, and provided along the inner with a few small
bristles. On closer examination, however, a very small terminal joint is found aftixed
to the inner corner. This joint (fig. 14a) is conical in form and provided with only a
single small apical bristle. The basal part, which about equals in length the terminal,
exhibits at the end, on the inner side, an imperfectly developed, rounded, masticatory
lobe, with two ciliated sete at the end, and is, moreover, provided on the inner edge

REPORT ON THE CUMACEA. (il

with two small hooks, whereby the two maxillipeds become, as it were, clasped
together.

The branchial apparatus affixed to the base of these limbs (fig. 18) is, as usual,
composed of two well-defined principal parts, the one pointing posteriorly, the other
anteriorly, the first representing the epipodite, and the second the exopodite. The
epipodite constitutes a rather narrow plate, concave on the upper surface and with the
posterior part curved in a hook-hke manner. The inner edge of this plate is somewhat
expanded in the middle, and exhibits an almost semicircular soft rim, to which is
affixed a series of eight digitiform gill-lobules, decreasing in size posteriorly, the two
posterior being quite rudimentary. Moreover, a single rather large gill-lobule, pointing
posteriorly, arises anterior to the others from the bottom of the plate. The exopodite
is nearly as long as the epipodite, and forms a narrow band-like plate, somewhat
irregularly twisted and expanding at the end into a very delicate and _pellucid
membranous flap, which admits of being exserted from the pseudorostral projection,
forming together with the one of the other side an imperfect tube, through which the
water, introduced into the branchial cavities, is expelled at reeular intervals.

The first pair of gnathopoda (fig. 15) are rather stout, with the basal part
comparatively broad and muscular, and provided at the extremity on the inner side
with a very long and densely ciliated seta pointing straight forwards, and at the outer
corner with a much smaller simple bristle. The terminal part, which about equals in
length the basal, is apparently composed of only four joints, the ischial joint not being
distinctly defined. The first of these joints is provided at the end, on the inner side,
with a rather strong ciliated seta, and the second with two simple bristles at the inner edge.
The third joint is somewhat swollen and of oval form, slightly larger than the preceding,
and has at the end externally a slender seta, and internally two very small bristles.
The terminal joint, finally, is exceedingly minute, and armed at the tip with three
unequal spines, the middle one being considerably shorter than the other two.

The second pair of gnathopoda (fig. 16) are quite pediform, and nearly twice as
long as the first pair, The basal joint is rather large, slightly curved and somewhat
tapering, with the outer edge finely ciliated and the inner smooth. The end of this
joint is not expanded, and bears exteriorly a very strong and elongate ciliated seta, and
anteriorly another much smaller seta. The terminal part is about as long as the basal,
and composed of five well-defined joints, the first of which (the ischial), however, is
very short, and armed on the inner edge with two denticles. The second or meral joint,
on the other hand, is rather large and expanded, and very obliquely truncate at the end.
The outer corner of this joint is prolonged to a sharp dentiform projection, and bears,
moreover, a strong ciliated seta; the inner edge is serrate, and provided with two small
bristles. The succeeding joint is much smaller, and has the outer edge serrate, being,
moreover, provided at the outer corner with a ciliated seta, similar to those on the

72 THE VOYAGE OF H.M.S. CHALLENGER.

preceding joints, and at the inner edge with three smaller bristles. The penultimate
joint is oval in form and unarmed, with two bristles on the inner edge. The terminal
joint, finally, is rather small and narrow, with four curved, claw-like spines at the tip.
The exopodite is about as long as the basal joint, and has the proximal part simple
and cylindrical, the distal is of about the same length, and composed of but three
joints, the two last being exceedingly small ; each of the joints is provided with two
natatory sete, one of which, however, arising from the first jot, is very small.

The first pair of legs (fig. 17) are only very slightly larger than the second pair of
gnathopoda, and of a very similar structure, though comparatively a little more slender.
The basal joint is armed at the end externally with a small dentiform projection and a
ciliated seta, and internally with two rather strong denticles. Two similar denticles are
also found at the inner edge of the very small ischial jomt. The succeeding joints, on
the other hand, are quite unarmed, the two first bearing each at the outer edge a single
ciliated seta, the two last only simple bristles. They successively decrease in size, the
terminal joint being rather small and linear. The exopodite exhibits a structure similar
to that of the second pair of gnathopoda, with this exception, however, that its terminal
part has an additional joint.

The second pair of legs (fig. 18) are scarcely smaller than the first and comparatively
of stronger structure. The basal joint is somewhat dilated at the middle and
comparatively shorter than that of the first pair. It has at the end on the inner side
a small dentiform projection, and on both edges a simple bristle. The ischial joint is
exceedingly small and unarmed. The meral joint is obliquely truncate at the end, and
provided on the inner side with a bidentate angular projection. The carpal joint is a
little longer and armed at the end internally with two strong denticles. The propodal
joint is very small and unarmed, whereas the terminal joint is rather elongate,
sublinear, and provided with a number of stiff bristles, two of which issue from the
outer edge, and three from the tip. This joint, together with the preceding, is
eenerally directed outwardly, forming a geniculate bend with the carpal joint. The
exopodite is exactly of the same appearance as that of the first pair of legs.

The two succeeding pairs of legs (figs. 19, 20) are quite simple and rather slender,
with the terminal part more or less curved exteriorly. Of the joints the basal is, as
usual, the largest, though considerably shorter in the posterior pair (fig. 20) than in
the anterior (fig. 19). The two succeeding joints are rather short and nearly equal in
size, whereas the carpal joint is much more elongate. The two outer joints rapidly
decrease in size, and the last joint has the form of a small biarticulate claw. Each of
the two preceding joints bears a strong curved seta at the end exteriorly. Elsewhere
these legs are only very sparingly supplied with simple bristles.

The last pair of legs, as has been stated above, were quite wanting in all the
specimens.

REPORT ON THE CUMACEA. (9

The uropoda (see fig. 21) are comparatively much shorter than in the preceding
species, scarcely attaining half the length of the tail. The scape is slightly serrate on
both edges, and exhibits a very marked squamous sculpture, the squamule being rather
large and triangularly pointed. The branches exhibit the structure characteristic of the
genus. The inner branch is only slightly shorter than the scape, uniarticulate, with
the inner edge serrate, and moreover armed with two slender spines; from the tip of
this branch three unequal spines arise, the middle one being by far the strongest. The
outer branch is a little smaller than the inner, and composed of two well-defined joints,
the first of which is quite short, whereas the last is rather elongate and gradually tapers
to the apex, bearing a rather long terminal spine, and a much smaller one on the inner
edge close to the apex.

Habitat.—The specimens of this species were detected by the author in examining
a parcel of dredged mud preserved in strong spirits, and kindly sent by Mr. John
Murray. The mud was obtained on January 29, 1874, off Cumberland Bay, Kerguelen
Island, from a depth of 127 fathoms (Station 1294).

(ZOOL. CHALL. EXP, —PART Lv.—1887.) ii 10

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TABLE OF CONTENTS.

INTRODUCTION, . 7 a ‘ : : : :
PrincipaL Works ON CUMACEA, ye j ; ‘ :
Morrno.ocy oF THE CUMACEA, ‘ : - : ”
DEFINITION OF THE FAMILIES, . : : : ; 4
List OF THE SPECIES, . 5 . : 5 5
DeEscRIPTION OF GENERA AND SPECIES, . ; : ; :
CumIpDms, . G é : 5 : : 5
Cyclaspis, G. O. Sars, F ; : é :
australis, 1. sp., . : : c : c
pusilla, 0. sp., . : : d :
exsculpta, D. Sp., . : : 4 :
VAUNTHOMPSONIIDE, 0 : é : : :
Vaunthompsonia, Spence Bate, : : , :
meridionalis, n. sp., 6 : 7 : c
LaAMPROPIDE, ; ; : : : : :
Paralamprops, n. gen., : : : : ¢
serrato-costata, 0. Sp.,. c 0
Lruconipa, F : : : : : ¢
Leucon, Kroyer. o ¢
assimtlis, D, Sp., : : : 0 7
tenuirostris, 0. sp., < : . é :
Eudorella, Norman, . : é ; : 9
abyssi, N. Sp... - : 0 7 :
DIASTYLIDA, , 6 5 : ; 5 6
Diastylis, Say, ; : : : :
stygia, G. O. Sars, 4 : ; : :
horrida, 0. sp., . : é 9 2 :
erinaceus, D. 8p. a ; : a 5
mystacind, D. sp., 0 : : : :
CUMELLIDA, . ; : ‘ ‘ : : ;
Nannastacus, Spence Bate, . 0 ¢ : :
suhmii, n. sp... : é : 6 :
CAMPYLASPIDEZ, . ; : : ; j
Campylaspis, G. O. Sars, : : : : é
pacifica, 0. sp., . : : : ‘ :
nodulosa, D. sp., . : : : : ;

(ZOOL. CHALL, EXP,—PART LY.—1887.)

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INDEX OF SYSTEMATIC NAMES,

Synonyms and Species incidentally mentioned are in ¢talies.

PAGE Drastynis—continued. PAGE
ALAUNA, : : : : 43 spinosa, 50
CAMPYLASPIS, : : ; 5 Bh Oe strigata, 50
glabra, . : ‘ 4 : 66 stygia, 2, 44
nodulosa, . : : ; : 68 | Diasryiipa, 7, 43
pacifica, . : ‘ ‘ ; 66 | Drops, 62
VENTUCOSA, : : , ; 68 | EpRIOPHTHALMIA, 3
CAMPYLASPID&, : : : GOD | Lvpora, 5 40
CHALAROSTYLIS, 6, 25 | Euporrnya, 7, 33, 40
CONDYLURA, . 3 : ; é 43 | abyssi, 41
Cuma, : 5 : 5, 12, 43 truncatula, 41
angulata, . : : é : 50 | ELUDORELLOPSIS, 1, 33
brevirostris, 5 : j : 50 | HemrLAMPRoOPs, 6, 25, 26, 31
unguiculata, : ; : : 62 | LPpHINOe, : 5
CUMELLA, . 8, 62 | Isopopa, A 3, 4, 54
CUMELLIDE, . ‘ 3 F . 8,62 | Lampropipa, Gao
CuMIDa, : ; : : . 5,11 | Lamproes, 6, 25, 3
CumoPsis, : : LEPTOCUMA, 6, 22, 23
CycLAspPIs, 5, 11, 21, 27, 29, 47 | ZLzprosryzis, . : 7, 43, 44
australis, . . 12,19 | Lxucon, 7, 33, 40, 42, 43
cornigera, 5A hs} anomalus, 22
exsculpta, . 12, 20 assimilis, . 33, 34
longicaudata, lee ails) longtrostris, 39
pusilla, 5 U2e At) nasicus, . 34
DIASTYLis, j F ; 7, 43, 65 tenuirostris, 33, 38
biplicata, . : : : : 50 | Levuconipa, 6, 32
calweri, . F ; : : 50 | Macrura, 3
echinata, . , : ; F 50 | Matacosrraca, 3
edwardsit, ; : : : 50 | Mysipa, 3, 4, 54
erinaceus, . 4 ' 2 . 44,58 | Nannasracus, . 8, 62
horrida, . ° : 6 . 44, 55 longtrostris, 63
insignis, . ; : : : 60 suhmii, . - 63, 67
josephine, : : ; : 58 unguiculatus, 63
lucifera, . ; ; ‘ . 55 | NEpatia, : 4
mystacina, : : : . 44, 60 | PARALAMPROPS, 6, 26, 38, 47
rathkit, . : : 5 : 50 serrato-costata, . 15, 26
rugosa, . ; F , : 50 | PETALOMERA, 38

78 THE VOYAGE OF H.M.S. CHALLENGER.

PAGE PAGE
PHYLLOCARIDA, : ; : : 4 | SrepHanomma, : : : : 5
PLATYASPIS, . ; : . 6, 25, 26, 31 | Trimosira, 4
PoDOPHTHALMIA, : : ; 3, 4, 54 | VAUNTHOMPSONIA, : : ‘ 6, 22, 27
PSEUDOCUMA,. 8 cristata, | 20, 24
PsEuDOCUMID2, ; : : 7 meridionalis, 23
Scuizopopa, . 4 A . 3,4 | VAUNTHOMPSONIIDEZ, . ‘ : Dylle22
SPENCEBATEA, 8, 62

PLATE [.

(ZOOL. CHALL. EXP.— PaRT Lv.—1887.)—Ii.

PLATE IL.

PAGE
Figs. 1-20. Cyclaspis australis, n. sp., . ; 12
Fig. 1. Young male, seen from the left side ; magnified about fifteen diameters.
Fig. 2. Same, seen from above.
Fig. 3. Young female, seen from the right side.
Fig. 4. Ocular lobe, seen from above.
Fig. 5. Antennal segment, viewed from below, together with antennule (a'),
antenne (c*), and anterior lip (L).
Fic. 6. Outer part of an antennula; more highly magnified.
Fie. 7. Posterior lip.
Fig. 8. Mandibles, seen from the front.
Fig. 9. Maxilla of first pair.
Fig. 10. Maxilla of second pair.
Fig. 11. Left maxilliped, together with the corresponding part of the branchial
apparatus, seen from above.
Fig. 12. Left maxilliped, isolated, seen from below; more highly magnified.
Fig. 12a. One of the marginal spines from carpal joint of same maxilliped ; highly
magnified.
Fig. 13. Terminal lamella of the exopodite of same.
Fig. 14. Gnathopod of first pair.
Fie. 15. Gnathopod of second pair.
Fie. 16. Leg of first pair.
Fig. 17. Leg of second pair.
Fig. 18. Leg of third pair.
Fig. 19. Leg of fifth pair.
Fic. 20. Last caudal segment, together with the uropoda, from above.
Figs. 21-23. Cyclaspis pusilla, n. sp., . : : 19
Fig. 21. Adult female, seen from the right side; magnified about twenty-six
diameters.
Fig. 22. Same, seen from above.
Fie. 23. Ocular lobe, seen from above.
Figs. 24-26. Cyclaspis exsculpta, n. sp., 5 : 20
Fig. 24. Anterior division of a female specimen, seen from the left side ; magnified
about twenty-six diameters.
Fig. 25. Same part, viewed from above.

. 26.

Ocular lobe, viewed from above.

Cumacea,PL1

The Voyage of H.M.S"Challenger:

Lith.W. Schlachter, Stockholtr

G.0. Sars, del

Fis? 4-20, CYCGLASPIS AUSTRALIS, n.sp. Fig § 21-28, CYCLASPIS PUSILLA, n.sp.

Fig® 24-26 CYCLASPIS EXSCULPTA, n.sp.

PLATE II.

Fig. 1
Fig. 2
Fig. 3.
Fig. 4.
INNER ta
Fig. 6.
Fig. 7
Fig. 8
His 9
Fig. 10
Fig. 11
Fig. 12.
Fig. 13.

PLATE II.

PAGE
Figs. 1-5. Vaunthompsonia meridionalis, n. sp., : ; 23

. Young female, viewed from the right side; magnified about fourteen

diameters.
Same, seen from above.

Anterior part of carapace, seen from above ; more highly magnified.

Same part, viewed from the right side. a’, antennula; a

x, terminal membranous part of branchial apparatus.

, antenna ;

Last caudal segment, together with right uropod, seen from above.

Figs. 6-13. Paralamprops serrato-costata, n. gen. et sp., : 26

Female, viewed from above; magnified about twelve diameters.

. Same, seen from the left side.

. Young male, seen from the right side.

. Right antennula of female, viewed from below.
. Right antenna of female.

. Anterior lip.

Posterior lip.

Mandibles, together with their adductor muscles, seen from the front.

Cumacea,Pl Il

The Vovage of H.M.S'Challenger”

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Fi8$ 1-5, VAUNTHOMPSONIA MERIDIONALIS n sp. Fig® 6-13, PARALAMPROPS SERRATO-COSTATA, n.sp.

PLATE III.

(ZOOL. CHALL, EXP.—PART Ly,—1887.)—lTii.

PLATE III.

PAGE

Paralamprops serrato-costata, n. gen. et sp., . : 26
(Anatomy—continued.)

Anterior division of body of a female specimen, seen from below. The
two gnathopoda on the left side, as also all the legs, are omitted, in
order to show the incubatory lamellae. a’, antennule ; a’, antennee ;
mp, maxillipeds; gn’, right gnathopod of first pair; gn’, nght
enathopod of second pair.

Anterior part of carapace, seen from above, somewhat compressed, to
show the fissure separating the frontal lobe from the two lateral lobes
forming the so-called rostrum.

Maxilla of first pair.

Maxilla of second pair.

Left maxilliped, seen from below.

One of the spines from inner edge of carpal joint of same maxilliped ;
highly magnified.

Left maxilliped, together with the corresponding part of the branchial
apparatus, seen from above. ex, exopodite ; ep, epipodite.

Gnathopod of first pair, together with the basal lamella.

7 bis. Gnathopod of second pair.

Le
Le

Leg of third pair.

of first pair.

2 09

» of second pair.

g

10a. Rudimentary exopodite of same leg; highly magnified.

Fig. 1.
Fig. 2.
Fig. 3.
Fig. 4.
Fig. 5.
Fig. 5a.
Fig. 6.
res
Fig.

Hig. 7S:
Higts 9:
Fig. 10.
Fig.

Higa:
Bip. 2.
Fig. 13.
Fig. 14.
Fig. 15.
Fig. 16.
Bigs li.

Leg of fifth pair.

Extremity of tail, together with telson and uropoda, viewed from above.

Terminal part of telson; more highly magnified.

Antennal segment, together with left antennula and antenna of a young
male, seen from below. On the right side only the bases of each are
represented.

Leg of third pair of same specimen.

Anterior pair of pleopoda of same.

Outer part of a pleopod; more highly magnified.

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The Voy

Cumacea,Pl Il]

Lith W. Schlachter Stockholm

PARALAMPROPS SERRATO COSTATA, n.sp.

(Anatomy)

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PLATE IV,

PAGE
Leucon assimilis, n. sp., . ; : : 34

. Young male, viewed from the right side; magnified about eighteen
diameters.

. Same, seen from above.
. Anterior part of carapace, seen from the left side ; more highly magnified.

. Antennal segment, together with antennule and left antenna, seen from
below.

. Outer part of an antennula; more highly magnified.

. An‘auditory bristle from same antennula; very highly magnified.
. Anterior lip.

. Mandibles, seen from behind.

. Posterior lip.

. Maxilla of first pair.

. Maxilla of second pair.

. Right maxilliped, seen from above.

. Outer part of same; more highly magnified.

. Part of inner edge of carpal joint of same maxilliped, with five of the
marginal spines.

. Left maxilliped, together with the corresponding part of the branchial
apparatus, seen from above.

. Gnathopod of first pair.

. Gnathopod of second pair.

. Leg of first pair.

. Leg of second pair.

. Leg of third pair.

. Leg of fourth pair.

. Leg of fifth pair.

. A pleopod.

. Outer part of same; more highly magnified.

. Last caudal segment, together with the uropoda, seen from above.

ne)

eof HM SChallenger’

The Voyas

ith.W.Schlachter Stockholm

T
ail

G.0.Sars del.

LEUCON ASSIMILIS, n.sp. (young male).

PLATE Y.

(ZOOL. CHALL. EXP.—PART Lv.—1887.)—lii.

Fig. 1
Fig. 2
Fig. 3
Fig. 4
Fig. 5
Fig. 6
Fig. 7
Fig. 8
Fig. 9
Fig. 10
Fig. 11

PLATE V.

Figs. 1-4. Leucon tenuirostris, n. sp.,

. Young female, seen from the right side; magnified about eighteen

diameters.

. Same, seen from above.

3. Carapace, with antennula and antenna, seen from the left side ; more

highly magnified.

. Last caudal segment, together with left uropod, seen from above.

Figs. 5-12. Hudorella abyssi, n. sp.,

. Adult female, viewed from the left side; magnified about eighteen

diameters.

. Same, seen from above.
. Anterior part of carapace, seen from the left side ; more highly magnified.
. Leg of first pair.

. Outer part of a leg of second pair.

Leg of fourth pair.
Leg of fifth pair.

Last caudal segment, together with right uropod, from above.

PAGE

38

41

Cumacea,P1.V.

The Voyage of H.M.S’Challenger”

Kholm

C.

Lith.W. Schlachter Sto

G.0. Sars, del

ON TENUIROSTRIS nspFig®5-12, EUDORELLA ABYSSI, nsp.

1-4, LEUG

s

Fi

PLATE VI.

g. 6.

PLATE VI.
PAGE
Diastylis stygia, G, O. Sars, : : 44

. Female, seen from the right side; magnified about nine diameters.

. Same, seen from above.

Adult male, viewed from the left side ; magnified about nine diameters.

Same, seen from above.

. Antennal segment of a female specimen, together with antennule (a'),

antennze (a), and anterior lip (L), seen from below.

Mandibles, together with adductor and rotatory muscles, seen from pos-
terior side,

. Posterior lip.

Maxilla of first pair.

Maxilla of second pair.

VI.

aL

Cumacea,P

ge of H.M.S"Challenger.”

The Voya

IS

FAY

a
eee

ER ter reaper epee
POLIPL LE LPSE a

Lith.W. Schlachter Stockholm
DIASTYLIS STYGIA, G.O. Sars, 2.2 3.

G.0. Sars, del

PLATE VII.

(ZOOL. CHALL, EXP.—PART LV,—1887.)—lii.

PLATE VII.

PAGE

Diastylis stygia, G. O. Sars; female, . ; 44
(Anatomy—continued.)

Fig. 1. Right maxilliped, together with the corresponding part of the branchial
apparatus, seen from above.

Fig. 2. Left maxilliped, isolated, seen from below; more highly magnified.
Fig. 3. Terminal joint of same; strongly magnified.

Fig. 4. Part of inner edge of carpal jomt of same maxilliped, with four of the
marginal spines; highly magnified.

Fig. 5. Gnathopod of first pair, together with the fully developed basal lamella.
Fig. 6. Gnathopod of second pair.

Fig. 7. Leg of first pair.

Fig. 8. Leg of second pair.

Fig. 9. Leg of third pair, together with the corresponding incubatory lamella.

Fig. 10. Leg of fourth pair.
Fig. 11. Leg of fifth pair.
Fig. 12. Extremity of tail, together with telson and uropoda, seen from above.

Fig. 13. Anterior part of ventral nervous cord, comprising three partly confluent
ganglia, innervating the oral parts.

Figs. 14-17. Embryo, taken from the marsupial pouch of an adult female specimen,
and still included within the inner egg-membrane, represented in four
different aspects; from the right side (fig. 14), from the anterior
extremity (fig. 15), from above (fig. 16), and from below (fig. 17);
magnified about forty-three diameters. O, ocular plates; a’, anten-
nula; a’, antenna; L, anterior lip; /, posterior lip; M, mandible ; im’,
maxilla of first pair; m’, maxilla of second pair; mp, maxilliped ; gn’,
enathopod of first pair; gn’, gnathopod of second pair; p'—p'*, legs of
first to fourth pairs; T, tail; C, carapace; », liver; Z (fig. 14),
anterior lip.

The Voyage of HM S’Challenger” Cunncen piagm

G.0. Sars, del ; Lith W. Schlachter, Stockholm

DIASTYLIS STYGIA, G.0. Sars ?.
(Anatomy & Embryology)

PLATE VIL.

Rigs)
Fig. 2
Fig. 3
Fig. 4.
Fig. 5
Fig. 6
Fig. 7
Fig. 8
igs 9
Fig. 10
Fig. 11
Fig. 12
Fig. 13.
Fig

Fig. 14.
Fig. 15.

PLATE VIII.

PAGE

Diastylis stygia, G. O. Sars; adult male, : : 50

(Anatomy.)

. Anterior part of body, after the carapace has been removed, from above,

exhibiting the whole branchial apparatus im situ. fr, frontal part ;
O, ocular lobe; a, antennula; a’, antenna; ex, exopodite of maxilli-
ped; exp, terminal lamella of same; ep, epipodite of maxilliped ;
br, gill.

. Right antennula; more highly magnified.

. Right antenna, with proximal part of flagellum, seen from below.

Part of flagellum ; more highly magnified.

. Part of the ventral nervous cord, comprising the seven ganglia belonging

to the trunk and the three anterior caudal ganglia.

. Gill isolated, seen from inner side.

. Part of the gill, with three gill-lamelle ; more highly magnified.
. Leg of first pair.

. Leg of second pair.

. Leg of third pair.

. Leg of fourth pair.

. Leg of fifth pair.

Anterior pair of pleopoda.

. 18a. Outer part of a pleopod of first pair.

Pleopod of second pair.

Extremity of tail, together with telson and right uropod, from above.

Cumacea, PL.VIIL

The Voyage of HM S."Challenger”

ps a oe pn eNO

Kholm

Lith W Schlachter Stoc

G.0. Sars, del

DIASTYLIS STYGIA, 6.0. Sars, 4

(Anatomy)

PLATE IX,

(Z00L, CHALL. EXP.—PART LY.—1887.)—Tii.

Wyre I
Fig. 2.
Fig. 3
Fig. 4
ies 25)
Fig. 6.
Fig. 7
Fig. 8
Bicw 9
Fig. 10.
Fig. 11
Fig. 12
Fig. 13.

Fig.

14.

PLATE IX.

PAGE
Figs. 1-8. Diastylis horrida, n. sp., . : : 5D
. Adult female, viewed from the right side; magnified about twelve
diameters.
Same, seen from above.
, Antennal segment, together with antennule, antenn, and anterior lip,
seen from below.
. Leg of first pair.
. Leg of second pair.
Leg of third pair.
. Leg of fifth pair.
. Last caudal segment, together with telson and right uropod, seen from
above.
Figs. 9-14. Diastylis erinaceus, n. sp., . é . 58

. Female, seen from the left side; magnified about twelve diameters.

Same, seen from above.

. Antennal segment together with left antennula and basal joint of right ;

seen from below.

. Right antenna, seen from below.

Same, seen from above.

Telson, seen from below.

The Voyage of H.M.S’’Challenger'

Cumacea PLIX.

G.0. Sars, del.

Lith.W, Schlachter, Stockholm.

Fig® 1-8, DIASTYLIS HORRIDA, n.sp. Fi§® 9-14, DIASTYLIS ERINACEUS,n. sp.

ey 7 a 7 %
‘

~
i :
can
® ‘
” - :
2 es 5 ? 4 i
: = aa . - se se De ee \
a ‘ ~~
7 “4 arti. S55 ae Loy] a
Je ot pred he
S et: a Seto £
_ PLATE X.
SS bers PER) tar COP PPP uea seh ae, yh : :
a me
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fi ‘
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; 7
7 7
a
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'
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hf
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Fig.

PLATE X.

Figs. 1-8. Diastylis mystacina, n. sp., .

. Adult female, viewed from the left side ; magnified about fifteen diameters.
. Same, seen from above.

. Extremity of tail, together with telson and uropoda, seen from above.

Figs. 4-5. Nannastacus suhmi, nu. sp.,

. Adult female, viewed from the right side ; magnified about fifty diameters.

. Adult male, seen from the right side; equally enlarged.

Fig. 6. Campylaspis pacifica, n. sp.,

. Adult female, seen from the left side; magnified about forty-three diameters.

PAGE

60

63

66

The Voyage of H.M S’Challenger” Gulazeapix

G.0.Sars, del Lith W.Schlachier, Stockholm

Fig? 1-3, DIASTYLIS MYSTACI NA, nsp. FigS 4-5, NANNASTACUS SUHMIL n sp.
Fig.6, CAMPYLASPIS PACIFICA, n. sp

ra

a

7v

PLATE XL.

PLATE XI.

PAGE

Campylaspis nodulosa, n. sp.. : 68

I
22

go
a

. Young (immature) female, seen from the right side; magnified about

twenty-seven diameters.
Fig. 2. Same, seen from above.
Fig. 3. Left antennula.
4, Outer part of same; more highly magnified.
Fig. 5. Anterior lip, together with left antenna (a’), seen from below.
Fig. 6. Same parts, seen from left side.

. Left lateral lobe of posterior lip.

“NI

Fig. 8. Mandibles, seen from posterior side.

_
ee.

gg
©

. Left mandible, seen obliquely from outer side.

Fig. 10. Masticatory parts of mandibles, seen from posterior side; more highly
magnified.

Fig. 11. Maxillee of first pair, seen from above.
Fig. 12. Maxilla of second pair.

Fig. 13. Right maxilliped, together with the corresponding part of the branchial
apparatus, seen from above.

Fic. 14. Left maxilliped, isolated, seen from above ; more highly magnified.
Fig. 14. Terminal joint of same; very strongly magnified.

Fig. 15. Gnathopoda of first pair.

Fig. 16. Gnathopod of second pair.

17. Leg of first pair.

Fig. 18. Leg of second pair.

Fig. 19. Leg of third pair.

Fig. 20. Leg of fourth pair.

{=}

Fig. 21. The two last caudal segments, together with uropoda, seen from above.

The Voyage of H.M.S’Challenger” Cumacea Pl XL

G.0. Sars, del

Lith W. Schlachter, Stockholm

CAMPYLASPIS NODULOSA,n. sp.

THE

VOYAGE OF H.M.S. CHALLENGER.

LOOLOGY.

REPORT on the Puytiocarmwa collected by H.M.S. Challenger during the
Years 1873-76. By Professor G. O. Sars, of the University of Christiania.

INTRODUCTION.

Amone the numerous Crustacea brought home by the Challenger Expedition, there are
two forms belonging to the above named interesting group, both of which represent new
generic types. This addition is especially of high interest since only a single recent
genus of Phyllocarida was hitherto known, viz., the genus Nebalza, all the other forms
belonging to this group being Paleozoic fossils. Thus, a closer investigation of the two
new types added by the Challenger Expedition cannot fail to be of great importance in
advancing our knowledge of this very remarkable and anomalous group of Crustacea.
One of the forms has already been roughly described by the late Dr. v. Willemoes
Suhm under the name of Nebalia longipes, and in the last edition of Professor Claus’
Zoology this form has been quoted with a new generic name as Paranebalia longipes. I
fully agree with Professor Claus that this species ought to be regarded as the type of a
new genus, which, however, is rather nearly related to the earlier known genus Nebalia.
The other form contained in the Challenger collection seems to deviate much more from
the typical genus, and may perhaps throw some light on the structure of certain fossil
forms. But the very restricted material has unfortunately prevented me from instituting
a satisfactory anatomical investigation of this interesting form. Besides these forms,
according to a letter from the late Dr. v. Willemoes Suhm to Professor v. Siebold,' a

1 Zeitschr. f. wiss. Zool., Bd. xxiy.
(Z00L, CHALL, EXP,—PART Ly1.—1887.) Kkk 1

2 THE VOYAGE OF H.M.S. CHALLENGER.

species of Nebalia, closely related to Nebalia geoffroyi, was observed off the Kerguelen
Islands. The specimens were, however, not preserved, apparently owing to their being
regarded as identical with the above named common species.

Principat Works on RECENT PHYLLOCARIDA.

Leacu, Zoological Miscellany, vol. i, 1814.

Minne-Epwarps, H., Mémoire sur quelques Crustacés nouveaux.
1828.

Histoire Naturelle des Crustacés, t. iii., 1840.

Kroyer, H., Karcinologiske Bidrag. Naturhistorisk Tidsskrift, 2° Rekke, Bd. ii. pp. 436-446, 1847.

Barro, W., British Entomostraca, 1850.

Merscunikorr, E., Development of Nebalia (in Russian), 1868.

Craus, C., Ueber den Bau und die systematische Stellung von Nebalia. Zettschr. f. wiss. Zool., Bd. xxii. pp.
323-330, pl. xxv., 1872.

Suum, R. v. Wittemors, On some Atlantic Crustacea from the Challenger Expedition.
Lond., ser. 2, vol. i. pp. 23-58, pls, vii.—x., 1875.

Packarp, A. S., The Nebaliad Crustacea as Types of a New Order, Amer. Nat., Feb. 1879; also Ann. and
Mag. Nat. Hist., ser. 5, vol. ii. p. 459, 1879.

A Monograph of the Phyllopod Crustacea of North America. Ann. Rep. Geol. Geogr. Survey of the
Territories, vol. xii, pp. 295-514, 38 pls., 1883.

Boas, J. E. V., Studien tiber die Verwandschaftsbeziehtingen der Malacostraken. Morphol. Jahrb., Bd. viii,
pp. 519-525, 1883.

Ann. d. Sct. Nat., t. xiii. pp. 299, 300, pl. xv.,

Trans. Linn. Soc.

GENERAL REMARKS ON THE MORPHOLOGY OF THE
PHYLLOCARIDA.

The views of zoologists as to the systematic position of the genus Nebalia, the only
hitherto known recent form of this group, have been widely different. Leach, the founder
of the genus, placed it among the Macrura, and was followed in this view by several
other authors, as Lamarck, Bose, and Desmarest, whereas Milne-Edwards in his important
work on the Crustacea put the genus among the Phyllopoda, placing it together with
the genus Apus in his family Apuside. The great authority of the last named eminent
naturalist seemed to have finally settled the question about the systematic position of
Nebalia, it being by the general consent of carcinologists regarded as a true Phyllopod,
though it was afterwards found necessary to remove it from the genus Apus, and to
establish a distinct family, Nebaliadze, for its reception. More recently, however, the
phyllopodous nature of this form has been denied by several naturalists. Thus, Dr. E.
Metschnikoff, in studying the development of Nebalia, was led to the result, that this
form should more properly be referred to the Decapoda than to the Phyllopoda, and
accordingly named it a “ phyllopodiform Decapod.” A similar view seems also to have
been partly adopted by Professor Claus in transferring Nebalia from the Entomostraca
to the Malacostraca. Finally, the late Dr. v. Willemoes Suhm, in describing a new form
from the Challenger Expedition, places the family Nebaliidee among the Schizopoda.
Mr. Salter’ was the first to point out the apparent affinity of the recent genus Nebalia,
to certain Paleozoic fossils, and Claus also recognised the relationship of Nebalia to
these old forms of Crustacea. In 1879 Dr. A. Packard established a distinct order,
Phyllocarida, for the reception of Nebalia, together with the above mentioned fossil
forms, which formerly had generally been regarded as true Phyllopoda most nearly
related to the genus Apus; and in the following year Professor Claus in the third edition
of his Zoology likewise referred the genus Nebalia to a distinct order, Leptostraca,
removing it far from the Phyllopoda and placing it among the Malacostraca.

As to my own views, I fully agree with the above named authors, that the genus
Nebalia ought to be removed from the Phyllopoda, but I am not prepared to agree
with Professor Claus in transferring it to the Malacostraca, and still less can I entertain the .

1 On Peltocaris, a New Genus of Silurian Crustacea, Quart. Journ. Geol. Soc. Lond., vol. xix., 1863.

4 THE VOYAGE OF H.M.S. CHALLENGER.

view of the late Dr. v. Willemoes Suhm in placing it among the Schizopoda. In my
opinion the genus Nebalia ought to be retained within the order of the Branchiopoda,
though representing a distinct subdivision or suborder, for which the name Phyllocarida,
proposed by Dr. A. Packard, as the older one, must be preferred to that proposed by
Professor Claus. The order Branchiopoda will thus contain the following subdivisions :—
Phyllocarida, Phyllopoda, Cladocera, Branchiura, the type of the last division being the
genus Argulus, which in my opinion cannot properly be referred to the Copepoda, as
proposed by Claus, but, in accordance with the views set forth by Thorell and others,
may find its proper place among the Branchiopoda, though it deviates still more from
the type of the order, the Phyllopoda, than is the case with the genus Nebalia.

It seems to be a generally adopted assumption, that the genus Nebalia forms a
distinct transition between the Phyllopoda and the Podophthalmia, and that its affinity
to the latter is even closer than to the former. I have been led to a rather different
view as to the relationship of Nebalia, and I think we shall find, on closer examination,
whether we consider the external or internal organisation, that this presumed affinity to
the Podophthalmia is in reality only very slight, and that most of the characters adduced
to show the decapodous nature of Nebalia do not hold good, since they are found fully
as pronounced either in other Branchiopoda or in certain Crustacea not at all belonging
to the Podophthalmian group. Thus, the stalked mobile eyes are not only met with in
the Podophthalmia, but also, as is well known, in a section of true Phyllopoda, the
Branchipodide, and as to structure the eyes in Nebalia evidently agree much more with
those in the latter than in the former. The carapace in Nebalia, it is true, exhibits
some resemblance to that in certain Schizopoda, as Gnathophausia, in being not connected
with the trunk, but we must remember that this is also the case in the Phyllopoda,
both in Apus and in the bivalved forms, and that this character in the Branchiopoda is
universal, whereas in the Podophthalmia it is exceptional, only distinguishing a very
restricted number of forms. Besides, the carapace in Nebalia shows both in its structure
and especially in the presence of a distinct adductor muscle a much closer resemblance to
the bivalved shell in the Phyllopoda. The form of the exposed part of the body in
Nebalia is very unlike that met with in the Podophthalmia, whereas the resemblance in
this respect to certain Phyllopoda and still more to the Copepoda is unmistakable. The
internal organisation of Nebalia, though rather deviating from that in the Phyllopoda,
does not show any marked resemblance to that in the Podophthalmia, being much
more similar to that in the Amphipoda; neither in my opinion can the development be
adduced as evidence of the decapodous nature of Nebalia.

As to the several limbs, their structure is in fact highly remarkable, indicating a
peculiar mixture of characters found in very different groups of Crustacea, and on the
whole their presumed resemblance to those in the higher Crustacea may on closer exami-
nation turn out to be only very slight. Thus, the structure of the two pairs of antenne

i

REPORT ON THE PHYLLOCARIDA. 3)

and the oral parts certainly appears very different from that generally met with in the
other Branchiopoda, but I think it will be fully as difficult to point out any closer
resemblance in this respect to the Podophthalmia. The eight pairs of limbs succeeding
the oral parts, on the other hand, are evidently constructed on the very same type as
those in the Phyllopoda, agreeing, as they do, both as to structure and function with the
so called “ branchial feet” in these Crustacea. But in Nebalia these limbs are followed
by four pairs of very differently formed appendages, constituting exceedingly powerful
natatory organs, and as similar swimming legs, the pleopoda, are also found in the
Podophthalmia, this character has hkewise been adduced to show the decapodous nature
of Nebalia. It must, however, be remembered, that such organs are not restricted to the
Podophthalmia, but are also met with in several other Crustacea, as Amphipoda and
Copepoda, and both as regards structure and number, the swimming lees in Nebalia
apparently agree much more closely with those in the Copepoda than with those in any
other group. This resemblance becomes still more striking by the presence in Nebalia
of two additional pairs of rudimentary caudal limbs, evidently answering to the rudi-
mentary legs found behind the swimming legs in several Copepoda. On the whole the
general appearance of Nebalia bears a very striking resemblance to that in certain free
living Copepoda, especially of the Harpactoid section. This similarity I do not regard
as merely accidental, but as indicating a true consanguinity, and this has partly also been
allowed by Dr. Packard. In order to understand the morphology of the Phyllocarida, it
thus becomes necessary not only to pay attention to the higher Crustacea, but also to
the lower forms, especially the Copepoda, which seem to be the most primitive of the
recent Crustacea. ‘To express shortly my opinion about the relationship of the genus
Nebalia, I would call it, instead of a ‘‘ phyllopodiform Decapod” as it has been termed
by Metschnikoff, more properly a “copepodiform Branchiopod.” At the end of this
Report, when the Challenger forms have been described, I propose to enter more in detail
into the question of the homology of the recent Phyllocarida with other known Crustacea.

As to the supposed affinity of the genus Nebalia to the fossil Paleeozoic forms referred
to the order Phyllocarida, the general appearance of the carapace, and especially the
presence in some of them of a similar jointed rostral plate as in Nebalia, seems in fact to
point to some closer relationship, but as the limbs of these old Crustacea are still wholly
unknown, and moreover, as the tail in most of them exhibits a rather different aspect,
the degree of affinity must still be regarded as very doubtful. In any case these
Paleozoic forms cannot be placed within the same family as Nebalia, but ought to be
separated as a distinct subdivision, and some of the forms exhibit such an anomalous
aspect as hardly even to justify the view that they belong to the same order. On the
other hand, it is quite evident, that the two new generic types from the Challenger
collection, described below, are on the whole so closely related to Nebalia as to be
properly classed together with this genus in the same family.

6 THE VOYAGE OF H.M.S, CHALLENGER,

DEFINITION OF THE FAMILY.

NEBALID2.

Anterior part of body covered by a large compressed bivalvular carapace, connected
with the body only along the cephalic part, its valves admitting of being moved by a
distinct adductor muscle and extending down the sides so as to enclose between them
all the oral parts as also the greater part of the other limbs. A tongue-shaped rostral
plate present in front, movably articulated to the carapace. Trunk covered over by the
carapace and composed of eight subequal segments. Posterior part of body tapering
backwards and consisting of two more or less distinctly defined subdivisions, pleon and
tail, each composed of four segments. Eyes pedunculated and mobile, but without
facetted cornea. Both pairs of antennze strongly developed, subpediform, with the
peduncle geniculate; anterior pair, or antennule, with the peduncle four-jointed and
bearing a setose lamella at the end, besides the flagellum; posterior pair with a single
multiarticulate flagellum. Mandibles comparatively small, with the cutting part rudi-
mentary, the molar tubercle well developed, palp very large, triarticulate. First pair of
maxille with two incurved masticatory lobes and a very elongate and slender reflexed
palp; second pair lamellar, with distinctly defined palp and exognath. Eight pairs of
subequal phyllopodous legs present on the trunk posterior to the oral parts; endopodite
more or less produced, with the inner edge and apex densely setiferous, but without
projecting lateral lobes. Four pairs of powerfully developed biramose pleopoda on the
succeeding part of the body, followed by two pairs of rudimentary caudal limbs.
Penultimate segment without limbs. No telson. Caudal rami simple, forming two
diverging plates edged with spinules and sete. Ova deposited within the lower part of
the carapace, and supported between the branchial legs. Development direct, without
metamorphosis. Internal organisation on the whole rather similar to that in the
Amphipoda.

Remarks.—As the fossil forms referred to the Phyllocarida are still very imperfectly
known, none of the limbs having as yet been found preserved, it is rather difficult to
point out the characters which should be regarded as exclusively distinguishing the
recent family Nebaliide, There is however at least one character, well seen in the
fossil forms, which seems to distinguish them very sharply from the Nebaliidee, viz., the
presence of a strongly developed telson, no trace of which is found in any of the recent
forms.

As above stated the recent Phyllocarida were formerly only represented by a single
genus, Nebalia. The two new genera, added by the Challenger Expedition, chiefly

REPORT ON THE PHYLLOCARIDA. if

differ from each other, as also from the typical genus, by the different development of the
phyllopodous or branchial legs. While in the one form, Paranebalia, both the endopodal
and exopodal parts of these limbs are very elongate, so as somewhat to approach the
form of the legs met with in the Euphausiide, these parts are in the other form
Nebaliopsis, so very much reduced as to cause these limbs to appear as merely simple,
slightly lobular plates. We have thus, as regards these limbs in the recent Phyllocarida,
a series of modifications tending in the one case to render them apparently more adapted
for the prehension of food, in the other case to restrict their function to solely respiratory
purposes ; the genus Nebalia occupying in this respect an intermediate position.

According to this difference in the structure of the branchial legs, the three recent.
genera of Phyllocarida may be characterised as follows :—

{ scarcely projecting beyond the edges of the carapace, endo-
podite narrow, indistinctly jointed, exopodite forming a
| broad rounded plate, epipodite very large, expanded at
both extremities, : 5 - . . WNebalia, Leach.
well
Heraloyysts projecting far beyond the edges of the carapace, endopodite
very elongate and slender, almost pediform, exopodite
also rather produced and ending in a narrow point,
epipodite exceedingly small, nearly obsolete, ' . Paranebalia, Claus.

legs

imperfectly developed, lamelliform, endopodal and exopodal parts only
slightly indicated as small triangular lobes, epipodite well defined, . Nebaliopsis, n. gen.

f
|
Branchial |
|

MO dis
f

DESCRIPTION OF GENERA AND SPECIES.

Order BRANCHIOPODA.
Suborder PHYLLOCARIDA.

Family NEBALIID&.

Paranebalia, Claus, 1880.
Paranebalia, Claus, Grundziige der Zoologie, ed. 4, vol. i. p. 576.

Generic Characters.—General appearance much as in Nebalia. Carapace smooth,
oval, lateral parts or valves produced posteriorly to broadly rounded lobes separated
above by an angular incision. Rostral plate well developed. Trunk scarcely longer
than pleon. Tail rather sharply defined from pleon, with the first seement smaller than
the succeeding. Eyes well developed, with distinct visual elements. Antennule rather
stout, with last joint of peduncle produced anteriorly to a serrate lamella; flagellum
comparatively short, greatly dilated in male. Antenne slender, with last joint of
peduncle elongate and geniculate at the base, flagellum simple, cylindrical, of similar
structure in both sexes. First pair of maxillze with the outer masticatory lobe narrowly
produced and abruptly truncate at the end; second pair with palp and exognath well
defined but comparatively small. Branchial legs projecting far beyond the edges of the
carapace; endopodite very elongate and slender, almost pediform; exopodite also very
elongate and produced to a narrow point; epipodite exceedingly small, upper end
produced. Pleopoda much as in Nebalia. The two succeeding pairs of rudimentary
caudal limbs both inarticulate. Caudal rami much as in Nebalia.

Remarks.—This genus, founded by Professor Claus upon the description given by the
late Dr. v. Willemoes Suhm of his Nebalia longipes, is chiefly distinguished from Nebalia
by the structure of the branchial legs, as also by the male having only the antennular
flagellum peculiarly modified, whereas the antennz are quite alike in both sexes. More-
over the maxillze exhibit some structural differences apparently of generic value. In all
other respects it seems to agree very closely with the typical genus. Only one species
is as yet known.

(zooL, CHALL. EXP.—PART LvI,—1887.) Kkk 2

10 THE VOYAGE OF H.M.S. CHALLENGER.

1. Paranebalia longipes, Willemoes Suhm (Pls. I., II.).

Nebalia longipes, Willemoes Suhm, On some Atlantic Crustacea from the Challenger Expedition,
iii; Trans. Linn. Soe. Lond., ser. 2, vol. i. p. 26, pl. vi. 1879.
Paranebalia longipes, Claus, Grundziige der Zoologie, ed. 4, p. 576.

Specific Characters.—Carapace as seen laterally, oval in form, covering besides the
trunk also more or less completely the sides of the pleon; rostral plate oblong, narrowed
in front and terminating in a spiniform projection. Posterior abdominal division or
tail scarcely longer than pleon and suddenly much narrower, the two middle segments
denticulate at the posterior edge. Eyes slightly curved and tapering to the end, upper
side strongly denticulate. Antennule with the terminal expansion of the peduncle
broadly lanceolate and armed with about twelve serrations along the outer edge;
flagellum not attaining half the length of the peduncle, and composed of but five
articulations, the first by far the longest. Antennze with last jomt of peduncle longer
than the preceding and armed at the anterior edge with two recurved denticles, flagellum
shorter than peduncle and six-articulate. Epipodite of last pair of branchial legs
produced above to a slender flap. The three posterior pairs of pleopoda with the basal
part strongly serrate at outer edge. The two pairs of rudimentary caudal limbs nearly
equal in size. Caudal rami about as long as the three last caudal segments combined,
outer edge minutely spinulose, inner setose, apex blunt, tipped with a fascicle of exceed-
ingly long and slender seta. Length of adult female 6 mm.

Remarks.—In the above diagnosis I have given some characteristics, to which I am
inclined to believe should only be attributed the value of specific marks. As, however,
the above named species is the only representative of the genus as yet known, a strictly
specific diagnosis cannot of course be drawn up at present.

Description.—Among the material sent me for examination no male was found, all
the specimens being either immature or adult females, partly laden with eggs or embryos.
But the late Dr. v. Willemoes Suhm has shortly described and figured the adult male of
this form, which exhibits some very interesting features not found in the male of Nebalia.
Unfortunately the male specimens examined by that naturalist have been lost, and thus
my investigations have been solely restricted to the female sex. The length of the
adult female does not exceed 6 mm. and hence the present form is rather inferior in size
to the known species of Nebalia.

All the specimens having been preserved in strong spirit, the body has become
rather opaque and of a dark brownish colour, showing however in most of them, at the
anterior part dorsally, a peculiar marking in the form of two symmetrical, slightly
ramified patches of a whitish colour (see Pl. II. fig. 1). Whether this marking is due to
a merely external colouring or indicates some underlying internal tissue, I have not
been able to ascertain. By carefully preparing a specimen with absolute alcohol and

REPORT ON THE PHYLLOCARIDA. Nal

oil of cloves, and then mounting it in Canada balsam, I have succeeded in rendering the
whole body sufficiently pellucid to admit a closer examination of the several parts in
their natural connection with each other (see PL. I. fig. 1).

As to the external appearance (see Pl. I. fig. 1; Pl. IL fig. 1) the present form
exhibits on the whole a great resemblance to the common species of Nebalia, with this
exception, however, that the terminal part of the body, comprising the four last segments,
is comparatively more slender and also more distinctly marked off from the preceding
part than is the case in Nebalia. In describing the body I find it advisable to
distinguish four principal divisions, viz., the cephalic part, to which the carapace is
connected, the trunk, the pleon, and the urosome or tail, the two latter parts answering
to the so-called abdomen in the higher Crustacea, and to the abdomen and thorax in the
Copepoda. All these four divisions are pretty well defined in the present form, and are
of about equal length, but differ both in form and in the structure of their respective
limbs.

The cephalic part is somewhat flattened, and along its whole dorsal surface firmly
connected with the carapace. It bears the following appendages, enumerated from before
backwards :—The eyes, the antennule, the antennze, the anterior lip, the mandibles,
the posterior lip, the first pair of maxille, and the second pair of maxilla. Of these
appendages only the eyes, the antennule, and the antenne project to a certain extent
beyond the free edges of the carapace, all the other parts being wholly concealed within
its valves.

The trunk is almost cylindrical in form, and only slightly longer than broad. It is
composed of eight short segments, well defined in their whole circumference, and nearly
equal in size, each bearing a pair of branchial legs, the outer part of which projects
beyond the free edges of the carapace.

The pleon is at the base fully as broad as the trunk, but tapers gradually, so as
scarcely to be more than half as broad at the end. It is composed of four well-defined
segments, each bearing a pair of powerfully developed natatory appendages or pleopoda.
The last segment is provided with distinct, rounded, epimeral plates, partly covering the
base of the corresponding pair of pleopoda.

The urosome or tail is rather slender, and very movably connected with the pleon, so
as often to form an angular bend with it (see Pl. I. fig. 1). It is nearly cylindrical in
form, and composed of four segments, the first of which is the smallest, and, properly
speaking, corresponds to the last thoracic segment in the Copepoda. This and the suc-
ceeding segment bear each a pair of rudimentary caudal limbs, whereas the third seement
is without any trace of limbs. The last segment terminates in two slender, diverging
branches, evidently answering to the so-called ‘“furea” in the Copepoda, and to the
caudal lamellz in the Branchipodide. The two middle segments of this division are
denticulate at the posterior edge, and the last segment projects at the end, beneath the

12 THE VOYAGE OF H.M.S. CHALLENGER.

terminal branches, as two triangular, pointed processes, having between them the anal
orifice (see Pl. IT. fig. 10).

The carapace (see Pl. I. fig. 1; Pl. II. fig. 1) is rather large, covering the greater part
of the body, including the whole cephalic part, the trunk, and part of the pleon. It is
highly compressed, the free lateral parts extending in the form of two valves perpen-
dicularly along the sides, so as wholly to cover the oral parts, and to include between
them the basal parts of the two pairs of antennze, as also the greater part of the branchial
legs. Above, the two valves pass immediately into each other by an even curve, without
any intervening hinge. As seen laterally (PI. I. fig. 1), the carapace exhibits a somewhat
oval form, with the dorsal line slightly arched, the anterior edges strongly curved, and
joining the inferior without any intervening angle. Posteriorly, each valve forms an
obtusely rounded lobe, advancing to a more or less extent over the side of the pleon,
without however covering the dorsal surface of that division. These lobes are separated
above by a deep emargination, at the bottom of which a small and narrow incision is
seen (see Pl. I. fig. 1). Owing to this emargination, the posterior edges of the
carapace appear in a lateral aspect (PI. I. fig. 1) obliquely truncate, and joining the dorsal
line at an obtuse angle. The so-called rostrum (PI. I. fig. 1, R; fig. 2) forms an oblong
tongue-shaped plate, movably articulated to the carapace in front, above the insertion of
the eyes. It is slightly arcuate, with the upper side convex, the lower concave, and
terminates in a sharp spiniform projection issuing from a slight longitudinal eleva-
tion running along the concave side of the rostrum. As seen from above or below (fig. 2)
this plate appears broadest near the base and tapers slightly towards the end, whereas
in Nebalia it is more regularly oblong—oval in form. When lowered and applied against
the anterior part of the carapace, it almost reaches to the inferior edges, thus, as it were,
closing the anterior aperture of the carapace as an operculum. The carapace is connected
with the body dorsally along a rather restricted space, extending from the base of the
rostral plate to about the middle of its length. The limits of this space are faintly
traced both in the lateral and dorsal aspect of the animal (see Pl. I. fig. 1; Pl. IL fig. 1),
and according to its position, this space may properly represent the gastric region in the
higher Crustacea. Throughout this limited dorsal area the carapace forms the immediate
body-wall, whereas elsewhere it only loosely covers the body, which admits of being
moved to a certain extent within it. On each side of the anterior part of the carapace,
immediately beneath the above-named region, and at a short distance behind the man-
dibles, an assemblage of lucid spots, forming together a well-defined, rounded, oval area
(Pl. 1, fig. 1, Cm) may easily be distinguished. This area is produced by the insertion
of the strong adductor muscle, by the aid of which the valves of the carapace admit of
being approached to each other to a certain extent. Both in form and position this
muscle entirely agrees with the strong adductor muscle of the shell met with in the

bivalved Phyllopoda, thus giving the carapace an evident phyllopodous character. As

REPORT ON THE PHYLLOCARIDA. 13

to structure, the carapace is rather thin and pellucid and very flexible, not at all cal-
careous, and without any trace of external sculpturing. It is composed of two distinct
layers, an outer chitinous coat, and a soft membrane lining the inside of the carapace.
Between the two layers there is a system of hollow spaces anastomosing with each other,
and forming together a complicated network of canals, in which the blood circulates.

The eyes (PL I. fig. 1, O; fig. 8) are movably articulated to a short segment, lying in
front of the antennal segment, and are partly covered by the rostral plate, projecting
obliquely at each side (see Pl. II. fig. 1). They are rather large, nearly as long as the
rostral plate, slightly curved, and somewhat tapering, and not as in Nebalia, expanded
at the end. The upper edge is slightly convex and densely denticulate, the denticles
increasing somewhat in size toward the tip of the eye; the lower edge is almost straight
and quite smooth. The eye-pigment is black, and does not completely fill up the outer
part of the eye, forming a narrow, oblong central mass, from which the small, rounded
crystalline cones project all around. There is no distinct facetted cornea similar to that
found in higher Crustacea.

The antennule (PI. I. figs. 1, a1; fig. 4) are rather powerful organs, almost pediform in
character, and more or less projecting in front of the carapace, immediately below the
eyes. They consist each of a strong, four-jointed peduncle, geniculate at the middle,
and two terminal appendages movably articulated to the same. The first joint of the
peduncle is rather firmly connected with the antennal segment and of a nearly quadrate
form, without any spines or bristles. The second joint is almost twice as long, and rather
movably articulated to the first, forming with it a more or less distinct elbow-shaped
flexure. It is shghtly dilated towards the end, which exhibits on the upper side an
obtuse projection, at the base of which several slender bristles are affixed ; from the lower
side, close to the end of the joint, moreover, four rather strong and recurved ciliated sete
arise. The third joint is somewhat shorter than the second, constricted at the base, and
likewise very movably articulated, so as generally to form with the preceding joint a
strong geniculate bend. At some distance from the extremity there is a slight promin-
ence, and between this prominence and the terminal edge a great number of slender,
diverging bristles occur. The fourth joint is much shorter, and has only a very restricted
mobility in relation to the preceding joint. It is produced along the anterior side to a
compressed lanceolate expansion (fig. 6) freely projecting from its end, and strongly
serrate along the outer edge. The serrations, from twelve to fourteen in number, are
pretty regular, and increase in size toward the tip of the expansion, each of them being
finely denticulate at the upper edge. At the base of this expansion a few slender bristles
are affixed to the inner surface of the joint. Of the two terminal appendages, the outer
one has the form of an oblong-oval lamella clothed along the anterior side and apex with
a great number of unequal-sized slender bristles, forming together a dense brush. The
inner appendage, representing the true flagellum, is more cylindrical in form, and also

14 THE VOYAGE OF H.M.S. CHALLENGER.

considerably more elongate, though scarcely exceeding half the length of the peduncle.
It shghtly tapers towards the end, and is composed of five articulations, the first of
which is nearly twice as long as the four others combined. All the articulations are
densely beset with bristles, especially along the anterior edge, where the bristles are
arranged in distinctly defined fascicles increasing in length toward the apex. On closer
examination, some of the setze are found to be densely ciliated along one of their edges,
and besides there is found in each fascicle an exceedingly delicate and pellucid ribbon-
shaped appendage (fig. 5), answering to the so-called olfactory cilia in other Crustacea.
According to the statements of the late Dr. v. Willemoes Suhm, the flagellum in the adult
male has a very different appearance from that in the female, being greatly expanded, and
without any distinct articulations. In the male of Nebalia, the flagellum is also some-
what different from that in the female, but the difference here consists chiefly in this part
being more elongate and having dense clusters of sensory bristles on the proximal joints.

The antenne (fig. 1, a’; fig. 7) are somewhat more elongate and slender than the
antennulze, and affixed in close approximation to the latter, so as partly to cover them at
the base. They are composed of an elongate, triarticulate peduncle, geniculate at the
middle, and a single multiarticulate flagellum. The first joint of the peduncle is short
and thick, somewhat similar to that of the antennulee and without spines or bristles.
The second joint is also quite smooth, but considerably more elongate, cylindrical in
shape, and, like the antennulze, forming a more or less distinct, elbow-shaped bend with
the basal joint. The last joint of the peduncle is still more elongate and close to its base
abruptly curved, so as to render the peduncle distinctly geniculate at the middle. The
anterior edge of this joint is somewhat irregularly flexuous, forming above, at the curvature
of the joint, a rounded, knee-shaped protuberance, beset with short bristles; two similar
but less prominent setose protuberances follow further below, and, besides, two somewhat
recurved dentiform projections are found at the same edge, the one nearly in the middle,
the other at the end. The outer part of the anterior edge is, moreover, beset with slender
ciliated setze, rapidly increasing in length towards the end, and continued transversely
on the inside of the joint, so as partly to project also on the posterior side; these sete
are very elongate, almost reaching to the end of the flagellum. The posterior edge of
the jomt has only a single seta at the middle, but this seta is very strong and more
densely ciliated than the others. The flagellum is considerably shorter than the peduncle,
cylindrical in form, and composed of six distinctly defined joints, the first of which is by
far the longest, and about equals the three succeeding in length. At the end of each of
the joints anteriorly, a dense fascicle of bristles occurs, and in addition the first joint has
three similar fascicles along its anterior edge. According to the statements of the late
Dr. v. Willemoes Suhm, the antenne in the adult male do not differ materially from
those in the female, whereas in the male of Nebalia the flagellum is extremely elongate,
slender and filiform.

REPORT ON THE PHYLLOCARIDA, 1155

The anterior lip (fig. 8) forms a rounded fleshy prominence issuing from the antennal
seoment and projecting backwards so as to cover the masticatory parts of the mandibles.
It is slightly emarginate at the free terminal edge and finely ciliated on each side of the
emargination. |

The posterior lip I have not succeeded in isolating from the surrounding parts. In
Nebalia it constitutes a rather small bifid lobe, limiting the oral orifice posteriorly.

The mandibles (fig. 1, W; fig. 9) have the body comparatively small and tapering
above to a narrow point reaching rather far up the sides of the body (see fig. 1). The
masticatory part is strongly incurved so as to form a right angle with the body. It has
the cutting edge quite rudimentary, only forming a small, undivided dentiform projection
(see fig. 10), whereas the molar tubercle is well developed, cylindrical in form, and
terminating in a large fluted molar surface. No difference whatever can be detected in
the armature of the two mandibles. The palp (fig. 11) is very fully developed, being
twice as long as the mandible (see fig. 9) and generally pointing obliquely anteriorly so
as to reach the inferior edge of the carapace (fig. 1, Mp). It is rather slender and
composed of three well-defined joints, the first comparatively short and unarmed, the
second very elongate and somewhat curved, bearing at the posterior edge four slender
bristles, and at the opposite side near the end another recurved seta. The last joint is
nearly as long as the preceding and strongly compressed, forming an oblong vertical
lamella, slightly dilated at the middle and provided along the outer part of the posterior
edge with a double series of densely ciliated bristles arranged in a comb-like manner and
increasing in length towards the tip. As to structure, the mandibles in the present form
agree fairly well with those in Nebalia, excepting that the cutting edge is still more
rudimentary, and that the last joint of the palp is somewhat differently formed.

The first pair of maxille (fig. 1, m'; fig. 12) exhibit two well-defined and rather
dissimilar masticatory lobes, and a slender recurved palp. The outer masticatory lobe is
rather narrow and strongly incurved, with the apex abruptly truncate and armed with a
double row of strong equal-sized spines, besides a few slender bristles, one of which,
affixed at a short distance from the apex anteriorly, is somewhat stronger than the others
and finely ciliated. The inner masticatory lobe is considerably shorter than the outer
and has the form of a rounded lamella, finely ciliated along the free edges and, besides,
provided with a row of about twelve strong ciliated setee, curved anteriorly and forming
together a broad fan. The palp, which is movably articulated to the end of the basal
part, at the base of the outer masticatory lobe, is very elongate and slender. It exhibits
at the base two imperfectly defined segments, forming together a more or less sharp bend
and followed by a very narrow setiform terminal part, projecting obliquely posteriorly
along the sides of the trunk (fig. 1, m’'). The latter part is provided along the lower
edge with about fifteen extremely slender unciliated bristles, the posterior of which are
rather regularly arranged, two issuing from the tip. In the structure of these maxille,

16 THE VOYAGE OF H.M.S. CHALLENGER.

which has been wrongly represented by the late Dr. v. Willemoes Suhm, the present
form exhibits some well marked differences from Nebalia. Thus, the outer masticatory
lobe in the latter genus is very dissimilar, being not nearly so much produced, and its
armature is also rather different ; moreover the inner lobe is somewhat smaller, whereas
the palp is comparatively more strongly developed.

The second pair of maxille (fig. 1, m; fig. 13) are composed of a somewhat lamellar
basal part, to the end of which two appendages are movably articulated, the inner one
representing the palp, the outer the exognath. The basal part is divided into two
segments, and juts out internally as three densely setose masticatory lobes, the posterior
of which is by far the largest. In front of these lobes there is a slight expansion, bearing
three slender ciliated setze, the outer of which is very elongate. The palp is shorter than
the basal part and rather narrow, biarticulate, with the first joint smooth, and the second
tipped with three slender ciliated setee. The exognath arising close outside the palp, has
the form of a narrow lamella, somewhat shorter than the palp, and provided along the
outer edge and apex with about nine finely ciliated sete. The maxillee above described
differ from those in Nebalia, chiefly by the far inferior development of both the palp and
exognath, which in the latter genus are considerably longer than the basal part, and
provided with a much greater number of bristles.

The branchial legs (Pl. I. fig. 1, brp; Pl. IL. figs. 2-4) in the present form are, as
above stated, modified in a peculiar manner, so as at first sight to appear very different
from those in Nebalia, this modification being apparently to make them more adapted for
direct prehension of the food, whereas their original function as respiratory organs seems
to be much less pronounced than in the typical genus. This is chiefly effected by the
excessive prolongation of the endopodite, accompanied also by a peculiar transformation
of the exopodite, and a considerable reduction of the epipodite. The branchial legs in the
present form thereby acquire an appearance strongly reminding us of the true legs in
some of the higher Crustacea, especially those of the Euphausiide. As is also the case in
Nebalia, these limbs are considerably more elongate in the adult females than in the young
animals and in the males, and are moreover distinguished by the great development of the
bristles affixed to them. In both sexes they project considerably beyond the free edge of
the carapace (see Pl. I. fig. 1, brp), whereas this is not the case in Nebalia. All the legs
present a rather uniform appearance, forming together a densely crowded double series
along the ventral side of the trunk, and being extended straight downwards, parallel to
each other, and with their outer projecting parts more or less distinctly curved. Their
movements in the living animal are undoubtedly performed in a simultaneous and
rhythmical manner as in Nebalia. As to structure (see Pl. II. figs. 2-4), the same
principal parts as in Nebalia are easily found, though rather modified in form. On the
main stem may be distinguished a somewhat expanded laminar basal part, and a slender
terminal part or endopodite, the latter being more or less curved and divided into a

REPORT ON THE PHYLLOCARIDA. alr

number of segments. These segments are, however, very imperfectly defined, and hence
can only be exactly counted with great difficulty, except on the posterior pairs (fig. 4), where
they appear more distinct, amounting to six in all. The inner edge of the stem does not
show any trace of lateral lobes or endites, but is bordered by a regular series of rather
elongate and slender ciliated sete. Besides, at a short distance from the edge along the
posterior surface, another similar series of slender setze occurs, and this series on the last pair
(fig. 4) successively passes over from the posterior surface to the outer edge, whereby the
terminal part of the endopodite becomes densely setiferous on both edges. Finally, a
third series of very minute hair-like bristles is found close inside the latter series along
the posterior surface of the legs. The setae of the basal part in all the legs are considerably
shorter than those affixed to the endopodite, though arranged in a similar manner. The
apical setee in most of the legs (figs. 2, 3) differ somewhat from the rest, at least in the
female, one of them being densely plumose, whereas the others are quite unciliated, very
slender and strongly curved at the tip. On the last pair (fig. 4), however, the apical setae
do not differ materially from the lateral, but on close examination a very small spine, some-
what reminding one of the terminal claw in higher Crustacea, is found at the tip between
the setae. The exopodite, issuing from the base of the endopodite on the outer side, exhibits
an appearance very different from that in Nebalia, having the form of a slender plate,
somewhat shorter than the endopodite, and produced at the end into a very narrow flap.
It is fringed along its whole outer edge with a single regular series of slender ciliated
bristles, one of which issues from the tip. In the middle pairs (fig. 3) the exopodite is
very elongate, and beyond the middle more or less distinctly geniculate, with an approach
to a division into two parts, a basal and a very narrow terminal part, thus acquiring
a certain resemblance to the natatory branch in higher Crustacea. In the posterior pairs
(fig. 4) the exopodite becomes considerably shortened, and of a more simple form. The
epipodite, which in Nebalia is exceedingly large and expanded both superiorly and inferiorly,
is in the present form reduced to a very small appendage affixed externally to the end of
the basal part. It has the form of a narrow recurved plate, very delicate in structure and
finely ciliated along the outer edge. In the anterior pair (fig. 2) this plate is slightly
bilobed, the inferior lobe being, however, very short and rounded; in the succeeding pairs
(fig. 3) it is more simple and oblong in form, and in the last pair (fig. 4) the plate is
considerably more produced above than in the other pairs, forming a narrow, slightly
flexuous flap, which projects upwards beyond the base of the leg (see Pl. I. fig. 1).

The four succeeding pairs of limbs (Pl. I. fig. 1, pl; Pl. IL. figs. 5-7), affixed to the
pleon, constitute very powerful natatory organs or pleopoda, which admit of being moved
with great force from before backwards, acting in much the same manner as the swimming
legs in the Copepoda. They consist each of a broad and somewhat flattened basal part,
to the end of which two diverging linear branches are affixed. The basal part is strongly
muscular, and composed of two unequal segments, the proximal quite short, the distal

(ZOOL, CHALL, EXP.—PART LYI.—1887.) Kkk 3

18 THE VOYAGE OF H.M.S. CHALLENGER.

oblongo-quadrangular in form, and in the three posterior pairs having the outer edge
regularly serrate. Of the branches the outer one is the shorter, and uniarticulate with the
outer edge, and the apex strongly spinose, the inner edge being bordered by a regular row
of ciliated setee, two or three of which issue from the apex inside the terminal spines.
The inner branch is somewhat more slender and distinctly biarticulate, the proximal joint
very short, the distal elongate and slightly tapering to the apex, which juts out as a
short dentiform projection and, inside the latter, bears a strong spine. Along both edges
of this joint a dense series of ciliated setze increasing successively in length toward the
tip is affixed, and from the inner side of the proximal joint a linguiform lateral lobe
(fig. 6) arises, armed at the tip with three strongly chitinised hooks (fig. 6b). This
lobe meets the one on the other side, and by the aid of the above-mentioned hooks both
pleopods become thus, as it were, clasped together, so as only to admit of a quite
simultaneous movement. In comparing the four pairs of pleopoda with each other, we
find some slight differences in their armature and in the relative length of the branches.
Thus, in the first pair (fig. 5) the outer edge of the basal part is quite smooth, without any
trace of the regular serrations occurring in the other three pairs. Moreover, the outer
branch in this pair is considerably shorter as compared with the inner, and the spines of the
outer edge are much more numerous and also arranged in a different manner, being only
in the distal part disposed in fascicles, whereas those of the proximal part form a dense
comb-like series. In all the other pairs (figs. 6, 7) the spines of the outer branch are
arranged in five distinct fascicles, two in each fascicle, besides a small seta, and to the
obliquely truncate apex three somewhat stronger spines increasing successively in size are
atlixed. The last pair of pleopoda (fig. 7) are somewhat smaller than the preceding
pairs, and have the inner branch only very slightly longer than the outer, and the spines
of the latter branch are also considerably smaller.

The two pairs of rudimentary caudal limbs (PI. I. fig. 1, cp", ep?; Pl. II. figs. 8, 9)
succeeding the true pleopoda are both of a very simple structure, forming narrow
uniarticulate plates, scarcely at all movable. They are setose at the inner edge and
armed at the obliquely truncate apex with three spines. Those of the first pair (fig. 8)
are somewhat larger and more densely beset with bristles than the posterior pair (fig. 9),
with the apical spines successively increasing in length, whereas on the latter pair the
middle spine is the longest.

The caudal rami (Pl. I. fig. 1, wr; Pl IL. fig. 10) have the form of two more or less
diverging narrow plates, movably articulated to the end of the last segment, and about
as long as the two posterior caudal segments taken together. They are minutely
spinous along the outer edge, and along the inner they are provided with a row of
short ciliated bristles, besides a series of minute spines. From the obliquely truncate
apex a dense fascicle of very long and slender sete arises, which, however, were mostly
broken in the specimens examined.

REPORT ON THE PHYLLOCARIDA. 19

The internal organs I have not succeeded in isolating by dissection, owing to the
small size of this form. In the previously mentioned specimen, rendered pellucid by
preparation in Canada balsam, and represented on PI. I. fig. 1, the intestine can, however,
be easily traced running through the axis of the body and terminating in a strongly
muscular rectum, which traverses the last caudal segment (see also Pl. IL fig. 10). At
the sides of the intestine the ovaries (PI. I. fig. 1, Ov) appear very distinctly, owing to
their being rather more opaque than the surrounding parts. They have the form of
two very elongate and narrow tubes running through the whole trunk and pleon, and,
moreover, projecting anteriorly to some extent within the cephalic part and posteriorly
almost reaching to the end of the second segment of the tail. They were each filled by
only a single series of ovarial ova, each with a very distinct germinal vesicle in the
centre.

The musculature of the body may also be rather distinctly traced in the specimen.
Thus, in the cephalic part several strong muscular bundles are seen passing from the
dorsal side to the several appendages belonging to that division, and in the succeeding
part of the body, besides the muscles moving the respective limbs, there is another
group of very powerful muscles running parallel to the axis, and by the aid of which the
body admits of being moved in relation to the cephalic part or to the carapace, as does
also the tail upon the pleon. Of these muscles the dorsal, or extensores, are the more
numerous, passing from the one segment to the other and apparently forming several
layers, whereas the ventral musculature is chiefly restricted to two strong muscles
running backwards beneath the intestine, and in the tail dividing into separate bundles
for each segment. The heart, distinctly visible in living animals from its rapid
pulsations, quite escapes attention in dead specimens owing to its very thin and pellucid
walls, and the nervous system, as also the ceca of the intestine are very difficult to see
even in fresh specimens. That all these parts on the whole may agree with those in
Nebalia, I cannot but believe, as these two genera are otherwise very nearly related.

Development.—As above stated, some of the specimens in the collection were
laden with eggs and embryos. On PI. IL figs. 11, 12, I have represented one of the
embryonic stages in a ventral and lateral aspect, having found it somewhat different from
the corresponding stage of Nebalia, as figured by Metschnikoff. The length of this
embryo is nearly 1 mm. As may be seen, it is still provided with the so-called larval
cuticle, forming a pellucid homogeneous sheath investing the greater part of the body,
and terminating in a slightly bilobed extremity. The anterior part of the body,
constituting the cephalic division, is very considerably dilated, almost globular, and to
a great extent filled up with the remainder of the yolk, whereas the succeeding part
gradually tapers posteriorly. The latter does not exhibit any trace of the strong dorsal
curvature found in the corresponding stage of Nebalia, according to the statement of
Metschnikoff, but is quite straight, or with the terminal part even slightly curved

20 THE VOYAGE OF H.M.S. CHALLENGER.

ventrally (fig. 12). Of the several divisions of the body which are distinguished in the
adult animal, the anterior or cephalic part is, as above stated, very massive and about as
long as the succeeding division or trunk, which exhibits, within the larval cuticle, all
its seoments well defined. The posterior part of the body, on the other hand, including
the pleon and the tail, is still rather imperfectly developed and scarcely longer than
the trunk. It consists of only five segments besides the caudal rami, and if the four
anterior of these segments be referred to the pleon, the tail will then only be represented
by a single segment. ‘The free edges of the developing carapace (fig. 12, C) can easily be
traced on each side as a curved line extending backwards from the base of the eyes and
meeting above at the most anterior part of the trunk. The carapace is thus in this
stage chiefly confined to the cephalic part, the greater portion of the trunk being exposed
behind it. The rostral plate (J?) is also readily detected as an obtuse protuberance
curving inferiorly in front and not yet marked off from the carapace. The several
appendages belonging to the cephalic division are all visible, though still rather
imperfectly developed. The eyes (QO) constitute two rather large recurved prominences,
which, however, as yet show no trace of either pigment or visual elements, and are also
quite smooth, not as in the adult animal denticulate. The antennule (q') and antenne
(a’) are of a very similar appearance, forming simple digitiform recurved processes
projecting freely from beneath the anterior part of the head, the former slightly diverging
the latter extending straight backwards along the ventral surface. Between the base of
the antennze a rounded prominence (Z), still invested by the larval cuticle, is seen,
representing the anterior lip. Somewhat posterior to this prominence, three pairs of
rather small and closely crowded processes occur, the two anterior pairs exhibiting a
slender terminal appendage, distinctly marked off from the proximal part, and somewhat
recurved, Of these processes the anterior pair (JZ) represent the mandibles, and their
terminal appendage the mandibular palp; the succeeding pair (m’) are the first pair of
maxille, and their terminal appendage, which is considerably narrower than that of the
preceding pair, is easily recognised as the slender recurved palp of these maxille; the
third pair (m’), finally, are as yet quite simple, conical in form and represent the second
pair of maxilla. On each of the eight segments of the trunk there are a pair of
bilobular appendages (brp) pointing posteriorly and each partly covering the one succeed-
ing it. These appendages represent the developing branchial legs and are all exactly alike
and slightly extended laterally. They are succeeded by three pairs of appendages (p/),
which are also distinctly bilobular at the tip, but much smaller and quite concealed by
the larval cuticle. These appendages are the three anterior pairs of pleopoda. No
trace can as yet be detected of either member of the fourth pair of pleopoda, or of the
two succeeding pairs of rudimentary caudal limbs. The caudal rami (uz) form simple
obtusely conical processes, lying within the symmetrically formed bilobular extremity of
the larval cuticle and being well defined from the last segment, but as yet without any

REPORT ON THE PHYLLOCARIDA. il

trace of spines or bristles. The young, when fully developed and ready to escape from
the incubatory cavity of the mother, have much the same appearance as the adult animal,
with this exception, however, that the last pair of pleopoda, as is also the case in the
young of Nebalia, are not yet developed, but only indicated as a slight projection of
the last segment of the pleon.

Habitat.—According to the statement of the late Dr. v. Willemoes Suhm, the present
interesting form was obtained during the stay of the Expedition at the Bermudas, by
Mr. John Murray, who took it in Harrington Sound, a bay which only communicates
with the sea through a narrow passage. Afterwards the late Dr. v. Willemoes Suhm
also collected the animal in the same bay, where it occurred not rarely under stones and
Corals. But among twenty females he only succeeded in finding two male specimens.

eee
Nebaliopsis, n. gen.

Generic Characters.
the dorsal line so as to cover over the whole trunk and the greater part of the pleon;

Carapace distinctly sculptured, very large and produced along

valves not expanded posteriorly nor separated above by any emargination. Rostral plate
very small, tongue-shaped. Trunk much larger than pleon and rather dilated. Tail very
small with the segments subequal. Eyes rudimentary, without pigment or visual
elements. Antennule not very strong, last joint of peduncle produced anteriorly to a
narrow projection, terminal lamella comparatively small, narrowed at the tip, with
scattered spines at the edge, flagellum well developed. Antenne with last joint of
peduncle divided into two segments, flagellum slender, multiarticulate. Mandibular palp
very strong, subpediform. Second pair of maxillee with palp and exognath imperfectly
developed and not defined from basal part. Branchial legs very small and simple in
structure, forming oblong lanceolate lamelle, setose on the imner edge and slightly
lobular at the outer, endopodal and exopodal parts only very faintly indicated, epipodite
distinctly defined, narrow, elliptical, upper extremity more produced than lower. Pleopoda
well developed, outer branch lamellar, expanded, inner lanceolate. The two succeeding
pairs of rudimentary caudal limbs subequal, uniarticulate. Caudal rami lamellar expanded,
outer edge spinous, inner setose.

Remarks.—The present new genus is chiefly distinguished by the peculiar form and
sculpture of the carapace, and by the structure of the branchial legs. In both these
respects, as also, it would seem, in the structure of the oral parts, it differs very consider-
ably from the two other known genera of recent Phyllocarida. The relative development
of the several divisions of the body is likewise rather different, especially when compared
with the typical genus Nebalia, the trunk occupying the far greater part of the body,
whereas the terminal part or tail—greatly developed in Nebalia—is very much reduced
in size. In the form of the carapace, the present genus shows a certain resemblance to

22 THE VOYAGE OF H.M.S. CHALLENGER.

the Devonian genus Dictyocaris, Salter, in which a distinct external sculpturing has also
been described ; but whether this resemblance is only accidental or points to some nearer
relationship between the two genera, it is impossible at present to say with any approach
to certainty.

2. Nebaliopsis typica, un. sp. (Pl. IIL).

Specific Characters.

dorsal keel running along the middle, its form, as seen laterally, oblongo-triangular, dorsal

Carapace thin and flexible, somewhat compressed, with a slight

line very faintly curved, anterior extremity narrowly rounded, posterior obtusely produced
above, inferior edges strongly curved in front of the middle. Rostral plate exceedingly
small, oval in form, with a slight carina running along the middle and terminating in a
blunt point. Surface of carapace sculptured by elevated narrow ridges anastomosing
with each other and forming together a somewhat irregular open network, less distinct
on the anterior part, where a somewhat flexuous transverse elevation passes down the
sides for a short distance from the anterior edge. Trunk very large, about as long as
pleon and tail combined. Tail scarcely longer than the three posterior segments of pleon
taken together, very narrow, with the posterior edge of the segments indistinctly denti-
culate, Eyes exceedingly small, cylindrical, smooth, apex rounded. Antennule with
the two first joints of peduncle rather strong and subequal in length, third much smaller,
Jamellar appendage about as long as first joint of flagellum. Antenne with the peduncle
scarcely longer than that of the antennulee, first jot the largest. Pleopoda with basal
part smooth, outer branch shorter than inner and having the outer edge strongly curved
and armed with a single row of small denticles. Caudal lamella about as long as tail,
expanded in the middle, extremity tapering and slightly incurved, outer edge apparently
armed with seven spines, increasing in size posteriorly, tip with two spines (or strong
sete). Length reaching about 40 mm.

Remarks.—The specific diagnosis given above is of course only provisional, the present
form being the only one of the genus as yet known. Most of the characters mentioned
above may, however, from analogy with other forms prove to be really specific in value.
It is apparently this form that was mentioned by the late Dr. vy. Willemoes Suhm in a
letter to Professor v. Siebold,’ as a gigantic Ostracode. This strange mistake may be
readily explained by the incompleteness of the first specimen obtained, of which only the
carapace and a small fragment of the body was brought up in the dredge.

Description.— Of this remarkable form there is in the collection an apparently young
specimen with most of the limbs preserved, and also the carapace of a much larger and
in all probability adult specimen, together with a fragment of the cephalic part. The
former specimen has a length of 22 mm. excluding the caudal rami, which are wanting

1 Zeitsclr. f. wiss, Zool., Bd, xxiv. p. xiii.

REPORT ON THE PHYLLOCARIDA. 23

in the specimen. Its carapace measures 16 mm. in length. The carapace of the other
specimen is fully 29 mm. long and 16 mm. high, and thus the total length of this
specimen may have been about 40 mm.—a very large size, indeed, as compared with
that of the other known recent Phyllocarida.

The form of the body (see Pl. III. figs. 1, 2) differs considerably from that in the
species of Nebalia and Paranebalia, not to speak of the peculiar shape of the carapace,
by the large size of the middle division, the trunk, whereas the posterior part of the body,
including the pleon and the tail, is comparatively far less developed and scarcely at all

longer than the trunk.

The carapace is exceedingly large and of a form distinctly deviating from that met
with in the other two genera. It is slightly compressed, though somewhat less so than
in Nebalia, and covers the greater part of the body, including the cephalic part, the trunk
and the greater portion of the pleon, without, however, being connate with the body except
along a very limited space in front. As seen from the side (figs. 1, 5) it exhibits an oblong
triangular form, with the dorsal line only very slightly arched, the anterior extremity
narrowly rounded, and the posterior extremity produced above to an obtuse angle. The
inferior edges exhibit somewhat in front of the middle a strong, almost angular curvature,
and behind this curvature they ascend obliquely, without forming any projecting lateral
lobe, but joining immediately the posterior edges by a very slight curve. The free edges
meet above at an obtuse angle, no intervening incision or emargination, similar to that
found in the other known forms, being present (see fig. 6). The rostral plate (see figs. 1, 5)
is exceedingly small, but distinctly defined from the carapace. As seen from above
(fig. 7) it exhibits a quite regular oval form, with a slight keel running along the middle
and terminating in front in a small angular projection. In both specimens it curves
straight downwards between the free anterior edges of the carapace, partly closing the
anterior opening of the shell as an operculum, but in the living animal it undoubtedly may
admit of being raised and lowered to a certain extent, as is the case with the other known
forms. As to structure, the carapace is very thin and flexible, almost membranaceous, and
semitransparent, but provided with a well-marked external sculpturing, especially very
distinct on the carapace of the larger specimen (figs. 5, 6). This sculpturing consists of
a system of narrow elevated ridges anastomosing with each other, and forming together a
somewhat irregular open network, limiting a great number of angular depressed areas of
different size and form. Towards the anterior part of the carapace this sculpturing
becomes gradually less distinct, and at last wholly disappears, whereas at a short distance
from the anterior edge a rather coarse transverse elevation passes down the sides, making
at its upper part a sharp curve backwards. In the middle of the dorsal surface (fig. 6)
a straight ridge or low keel runs along the carapace from its anterior extremity to the
posterior, dividing it into two symmetrical halves, and at the end of the anterior fourth
part of the length of the carapace a well-defined obliquely transverse line crosses the ridge

24 THE VOYAGE OF H.M.S CHALLENGER.

and marks off in front the very small space where the carapace forms the immediate
body-wall, at the same time dorsally defining the anterior division of the body,—the
cephalic part. Immediately below this area, on each side, the insertion of the adductor
muscle of the valves is distinctly seen as an assemblage of small lucid spots.

The division of the body behind the cephalic part is very large, occupying more than
the third part of the length of the body. It is at once seen to answer to the compara-
tively small part described above in Paranebalia as the trunk, and is, as in that genus,
composed of eight well-defined segments, slightly increasing in size posteriorly, and each
bearing a pair of branchial limbs. The ventral surface of this division bulges out
as it were in its posterior part, so as to project further down than the pleon, whereas the
contrary is the case in the two other known genera.

The pleon is considerably shorter than the trunk and rapidly tapers posteriorly. It
is composed of the normal number of segments, none of which, however, exhibits any
traces of distinct epimera.

The tail is very small and narrow, cylindrical in form, and about as long as the three
posterior segments of the pleon taken together. It is composed, as in the other genera,
of four segments about equal in size, the three anterior being slightly denticulate at the
posterior edge. The last segment is somewhat dilated at the end, and wants the dentiform
projections found in the preceding genus on each side of the anal orifice.

The eyes (figs. 8, 9,O) exhibit a quite rudimentary condition, wanting, as they do,
every trace of pigment and visual elements. They are very small, so as easily to escape
attention, and nearly cylindrical in form, or very slightly dilated towards the end, which
is obtusely rounded and quite smooth.

The antennule (fig. 8, a1) are constructed upon the very same type as in Nebalia
and Paranebalia, but appear comparatively shorter and stouter. The first joint of the
peduncle is rather massive, irregularly angulated, and, as in the latter genera, very firmly
connected with the head. The second joint is scarcely longer than the first, dilated in
the proximal part, and rapidly tapering to the end, forming with the succeeding joint a
strong geniculate bend. It bears on the inner side near the end a few recurved setee, but
is otherwise, like the first, quite smooth. The third joint is scarcely more than half as
large as the preceding, constricted at the base and somewhat dilated toward the end, with
the terminal edge forming on the outer side an obtuse angle. The fourth joint is still
smaller but rather broad, and juts out anteriorly as a slightly curved narrow process,
strongly compressed and very finely denticulate at the anterior edge. As in Nebalia
and Paranebalia a lamellar appendage is articulated outside at the base of this process.
This appendage is, however, rather small and of a somewhat fusiform shape, with a few
small spines along the anterior edge, two of which are affixed to an angular projection
about the middle. Of the numerous slender bristles which clothe the corresponding
lamella in the two other genera, there is no trace to be detected. The flagellum seems

REPORT ON THE PHYLLOCARIDA. 25

to have been rather elongate, in all probability much longer than the peduncle, but the
outer part is wanting in both specimens. The preserved proximal part is composed of
eight joints, the first of which, as usual, is by far the largest and about as long as the
lamellar appendage, whereas the succeeding joints are very short. The bristles, which
may have clothed these joints anteriorly, were broken off in the specimen examined.

The antenne (fig. 8, a) are somewhat more slender than the antennule, and
comparatively rather smaller than those in Nebalia and Paranebalia. The peduncle is
scarcely longer than that of the antennule and geniculate at the middle. Its first joint
is the largest, irregularly quadrangular in form, and exhibits on the outer side at the
base a rounded prominence, slightly overlapping the basal joint of the antennule. The
second joint is, like the first, quite smooth, and has the distal extremity obliquely truncate,
forming with the succeeding joint a sharp geniculate bend. The latter joint is considerably
more slender than the two preceding, and divided into two segments by a well-marked
transverse suture. It is provided along the anterior edge with a number of small slender
bristles, forming on the proximal segment a double row. The flagellum in both specimens
is imperfect, the outer part being broken off, but, to judge from the form of the proximal
part, it may have been rather elongate and slender.

The anterior lip (figs. 8, 9, L) projecting posteriorly between the bases of the antenne,
is rather large and almost pentagonal in form, the terminal edge being not, as in the
two other genera, emarginate, but on the contrary produced in the middle as an obtuse
angle, and without any visible ciliation.

The mandibles (fig. 8, MZ) are very small, more so even than in Nebalia and Para-
nebalia. The structure of their masticatory part could not be more closely examined, but
this part seems to be far less developed than in the genus Paranebalia. The palp (Mp),
on the other hand, is very large, almost pediform, and composed of three distinctly defined
joints forming angular bends with each other. The basal joint is rather massive, and forms
with the succeeding joint apparently a very movable articulation. Both these joints are
quite smooth and nearly uniform in size, whereas the terminal joint is considerably smaller
and of a narrow elliptical form ; it is moreover strongly compressed, and provided along
the posterior edge with a dense row of ciliated bristles, arranged in a comb-like manner.

Of the maxillee I have only been able to examine the second pair more closely, the
first pair being so much damaged in the specimen examined as not to admit of any
satisfactory description. The former pair (fig. 10) are very small and look rather
dissimilar to those in Nebalia and Paranebalia, whereas, on the other hand, they show
an unmistakable resemblance to the maxille in certain Copepoda. As in the latter
group the inner masticatory lobe is very strongly developed and does not extend in the
same plane as the others; it is, moreover, provided at the free edge with a dense row of
strong spine-like bristles, which are ciliated at one of their edges and recurved, so as to

form together a dense comb-like fan projecting towards the oral orifice. The three other
(ZOOL, CHALL, EXP,—PART LvI.—1887.) Kkk 4

bo

6 THE VOYAGE OF H.M.S. CHALLENGER.

masticatory lobes are much smaller, and very narrow, and arise from a common lamellar
expansion lying outside the principal lobe. They were devoid of any armature, but it
may be that a few bristles have been originally affixed to their obtusely rounded
extremities. Neither the palp nor the exognath are distinctly defined from the basal
part but appear only as simple expansions of it. The palp has the form of a rather large
oval projection extended in the axis of the maxilla, and provided with numerous slender
ciliated setae on both edges, those of the outer edge being the longest and arranged in
several rows. The apex is evenly rounded and unarmed, whereas a row of very small
spine-like bristles is found along the inner edge, inside the slender ciliated setae. The
exognath is exceedingly small, constituting only a very slight lamellar expansion of the
outer edge, and provided with four densely plumose and somewhat flexuous sete
increasing in size towards the base.

The branchial legs (fig. 3) are at first sight very unlike those in the two other known
genera, and comparatively far inferior in size, as also much more widely separate from
one another (see figs. 1, 2). They are very simple in structure, forming, as they do,
merely delicate membranous lamella of oblongo-lanceolate form and slightly lobular at
the outer edge. There is no marked limit between basal and terminal part, nor are the
endopodite and exopodite distinctly defined, the epipodite being the only part distinctly
marked off from the plate. The inner edge of the plate forms a very slight and even
curve, and is bordered by a single row of slender sete, continued also on the narrowly
rounded extremity. Beyond the middle there is outside a very slight lobiform expansion,
the distal end of which is somewhat produced and separated from the terminal part of
the plate by a narrow incision. This expansion, which is quite smooth, may, from its
position, answer to the exopodite, and the part of the leg projecting beyond the above
mentioned incision of course corresponds to the terminal part of the endopodite in the
other Nebaliide. The epipodite forms a narrow elliptical lamella affixed on the outer
side nearer to the base, and separated from the exopodite by another narrow incision.
It is connected to the leg by a narrow neck, and has the upper extremity considerably
more produced than the lower, the former even reaching somewhat beyond the base of
the leg. The substance of the branchial legs is very soft, almost parenchymatous, and
between the two investing cuticles there is accumulated a granular opaque mass disposed
in small patches, apparently coagulated blood. All parts of the leg, indeed, seem here
to be equally well adapted for respiratory purposes. Moreover, in the proximal part
several thin muscular bundles are seen, partly crossing each other and disappearing at
about the middle of the length of the leg.

The pleopoda (fig. 4) are rather powerful and, as in the other genera, composed of a
large lamellar basal part, to the end of which two unequal branches are affixed. The
basal part is oblongo-quadrangular in form and quite smooth, though projecting at the
end externally as an acute angle. Of the branches the outer one is uniarticulate and

REPORT ON THE PHYLLOCARIDA. 2.

distinguished by its lamellar structure and peculiar expanded form, the outer edge
bulging out as a strong curve, whereas the inner is quite straight. The latter bears a
row of short sete, whereas the outer edge is armed with numerous small denticles,
arranged pretty regularly in a single series. The inner branch is considerably longer
than the outer, but much narrower and lanceolate in form. It is composed of two
distinctly defined joints, as in the other genera, the first quite short and bearing inside
the usual linguiform lobe, the second evenly tapering
to the apex, and all around the edges fringed with
ciliated sete. The first pair of pleopoda only differ
from the other three by the outer branch being some-
what less expanded. The last pair, as in the other
genera, are somewhat shorter than the preceding pairs,

Bi ie oa

. ff WY J
but otherwise of the very same structure. A
oh
The two pairs of rudimentary caudal limbs suc- 4 {/
ceeding the pleopoda (see fig. 1) are very small, and < A
quite alike, forming simple narrow plates, setose at the ‘ 4

edges and pointing directly backwards.

The caudal rami were broken off in the specimen
examined, and are only conjecturally indicated in fig, 1
by dotted lines. When, however, recently preparing
the specimen for retransmission, I detected at the
bottom of the tube in which it was originally pre-
served, a part, which, in spite of its anomalous
appearance, I cannot but believe to be one of the
caudal rami, detached from the specimen. In the
accompanying cut I give a figure of this part, drawn
to the same scale as figs. 3 and 4 on Pl. HL, which
represent limbs from the same specimen. In its
general appearance it somewhat resembles the outer
branch of the pleopoda, but is very much larger,
measuring nearly 5 mm. in leneth and thus about
equalling that of the posterior division of the body, or tail. It has the form of a rather
broad lamella, somewhat expanded in the middle and drawn out to a slightly imcurved
extremity, which is narrowly truncate. The edge, which I regard as the outer, is
sharpened and evenly curved, with seven angular notches, to which as many spines may
have been affixed, one of which, the most proximal, still remains. The latter is very
small, but in all probability the others successively increased in size posteriorly. The
inner edge is evenly convex in its proximal part, but becomes slightly sinuous towards
the end. It is considerably thickened and exhibits two distinct lips, limiting a narrow

Fic. 1.—Caudal ramus of Nebialopsis typica.

28 THE VOYAGE OF H.M.8. CHALLENGER.

sulcus, to the bottom of which a series of slender ciliated setze seems to have been
affixed, the bases of most of them being still present. From the tip of the lamella a
fragment of what may have been either a strong spine or a very clongate seta projects,
and external to this another similar spine or seta may have been affixed. The whole
lamella exhibits a delicate parenchymatous structure similar to that of the branchial legs.

As the younger specimen is rather pellucid, some of the internal parts can also be
faintly made out through the integuments. Thus, in a lateral view (fig. 1), a dark string
is seen running from the cephalic part through the whole trunk and part of the pleon, at
some distance from the dorsal surface. On examining the animal from the dorsal side,
this string is found to be composed of two symmetrical narrow tubes filled with an
opaque granular mass, and having between them another tube somewhat wider and more
transparent. It therefore seems evident that the string referred to must represent the
intestine, together with two elongate caeca accompanying it in the greater part of its length.
But, besides, the anterior part of the body contains another internal organ of far greater
dimensions, constituting a large opaque mass slightly tapering posteriorly and extending
through the greater part of the trunk at a short distance from the ventral surface. The
significance of this body I am unable to state with certainty. It cannot represent the
generative organs, since it apparently forms an unpaired mass, and, moreover, its situa-
tion would seem to forbid such an assumption. I am more inclined to regard it either
as a kind of liver, or perhaps more properly an accumulation of fatty deposits, answering
to the adipose body which in Nebalia envelops the whole intestine together with its
ceca. The ventral ganglionic cord—only with great difficulty examined in the two other
genera—is here immediately visible when the animal is examined from the lower side
(fig. 2), lying, as it does, immediately inside the ventral cuticle and not being concealed by
the branchial legs. The ganglia of the trunk, placed in the two other genera so closely
together as almost to be coalescent, are in this animal wide apart and connected by very
long commissures, in close proximity to each other. The ganglia of the pleon, of which
at least the anterior is very distinctly seen, are considerably larger than those of the
trunk, and furnish several nerve-trunks to each side, from which numerous fine nerves
arise, partly innervating the musculature of the pleon and partly entering the pleopoda.

Habitat.—The first specimen obtained, which, as above stated, was only represented
by the carapace and a fragment of the front part of the body, was taken with the dredge
in the Southern Ocean between Prince Edward Island and the Crozets.

Station 146, December 29, 18783; lat. 46° 46’ S., long, 45° 31’ E; depth, 1375
fathoms ; bottom, Globigerina ooze ; bottom temperature, 35°°6.

The other more complete specimen came up in the trawl from a very considerable
depth in the South Pacific, about midway between New Zealand and Chili.

Station 289, October 23, 1875; lat. 39° 41’ 8, long. 131° 23’ W.; depth, 2550
fathoms ; bottom, red clay ; bottom temperature, 34°°3.

HOMOLOGY OF THE RECENT PHYLLOCARIDA.

In the following pages I propose to discuss more in detail the homologies of the
several parts in the Nebaliidee, as compared with those in other recent Crustacea. As
has been indicated at the beginning of this Report, my view as to the relationship of
the genus Nebalia to other known Crustacea somewhat differs from that set forth by
most other naturalists, and the examination of the two related new generic types pro-
cured by the Challenger Expedition, and described above, has confirmed me still more in
the opinion at first adopted from a thorough investigation of our common northern form,

Nebalia bipes, Fabricius.
It is certainly astonishing that the great resemblance of Nebalia to certain Copepoda,

Fic. 2.—Diosaccus tenuicornis (Claus), male.

has escaped the attention of most naturalists who have subjected this genus to a closer
examination, whereas the much more remote affinity to the Podophthalmia has always
been dwelt upon, and even Professor Claus, to whom we are, as is well known, indebted
for an admirable work on the free living Copepoda, does not seem to have been aware
of this unmistakable resemblance; I think it may be readily found by a closer com-
parison, that the affinity of Nebalia to the Copepoda is in fact much greater than to the
Podophthalmia, both as regards the external appearance and the structure of the several
appendages. In some other important points it exhibits, on the other hand, an evident
agreement with the Phyllopoda, and for that reason it ought to be, in my judgment,

30 THE VOYAGE OF H.M.S. CHALLENGER.

placed within the same order, the Branchiopoda, though representing the type of an
anomalous suborder, the Phyllocarida.

In order to facilitate a closer comparison of the Nebaliide with the Copepoda, I sub-
join a cut of a male specimen of one of our most common marine forms of the Harpactoid
group, viz., Diosaceus tenuicornis (Claus).

Homology of the Body-Divisions.—In examining the body of a Nebaliid, its general
resemblance to that of a Copepod, especially of the Harpactoid group, may at once be
recognised. But itis at the same time readily seen that there is in the Nebaliide a
distinct division of the body which is only faintly indicated in the Copepoda, viz., the
trunk, or, as it is generally termed, the thorax. What is described as thorax in the
Copepoda does not at all answer to the thorax in the higher Crustacea, but undoubtedly
is homologous with the anterior part of the ‘‘abdomen” in these Crustacea, or the divi-
sion in the Nebaliidee described above as the pleon, whereas the so-called abdomen in the
Copepoda evidently answers to only the posterior part of the abdomen in the higher
Crustacea or the division in the Nebaliide succeeding the pleon, and described above
as the tail. This is especially distinctly seen in the above described form, Paranebalia
longupes (Pl. I. fig. 1; Pl. II. fig. 1), where the latter division is very sharply marked off
from the pleon, both exhibiting a form very similar to that in the Copepoda, and, more-
over, quite agreeing in function, since the tail here evidently admits of being moved as a
whole upon the pleon, in the very same manner as in the Copepoda. A closer com-
parison between the Nebaliidze and Copepoda thus clearly shows that the terminology
generally adopted in describing the higher Crustacea has been wrongly applied as regards
the lower forms (Copepoda), since the divisions “ thorax” and “ abdomen” in the former
do not answer to the similarly named divisions in the latter. This misapprehension may
indeed have been the cause why the affinity of Nebalia to the Copepoda has not been re-
cognised. Thus, in order to explain the supposed abnormal number of segments in the
“abdomen” of Nebalia, Professor Claus has set forth an hypothesis, which seems to me
very unreasonable, viz., that the two last segments together with the caudal rami in
Nebalia answer to the telson in the Podophthalmia, which latter part, he suggests, has
been originally formed by several segments. The fact is, however, that the so-called
abdomen in Nebalia does not show any similarity at all to that division in the higher
Crustacea, whereas it is constructed upon the very same type as in the Copepoda, the
number of segments being in full accordance with that found in a great number of these
Crustacea, admitting the above given explanation of the homology of the body-divisions
in both. As to the limit between the two divisions in the Nebaliidze, described above as
pleon and tail, it should be remembered that the first segment of the latter division,
properly speaking, answers to the segment in the Copepoda generally described as the
last thoracic segment, but which in most of the forms evidently has a much closer relation
to the succeeding division, the tail, or, as it is wrongly termed, the abdomen.

REPORT ON THE PHYLLOCARIDA. al

fLomology of the Carapace.—As above mentioned, the carapace in Nebalia has been
adduced as a character showing the affinity of this genus to the Podophthalmia, and
especially the Schizopoda. On closer examination we shall, however, find that according
to this character it might with quite as good reason be classed among the Phylopoda ;
for both the finer structure of the carapace and the manner in which it is connected with
the body are rather more in accordance with the latter Crustacea than with the Podoph-
thalmia. Moreover, the presence of a well-developed adductor muscle, never found in
any Podophthalmia, gives the carapace in the Nebaliide a very marked phyllopodous
character. As to form and relation to the body, it exhibits, as it were, an intermediate
condition between the carapace in Apus and the bivalved shell in Limnadia. The jointed
rostral plate is a character neither found in the Podophthalmia nor in the Phyllopoda,
whereas a quite similar movable rostral projection is met with in some Copepoda of the
Harpactoid group, and in the latter forms, moreover, the lateral parts of the so-called
cephalic segment are found to extend more or less down the sides, so as to include between
them the bases of the antennze and most of the oral parts, thus assuming the character
of a bivalvular carapace, though being still connate with the body along the dorsal
surface. The greatly developed carapace, by which the Nebaliidee at first sight seem to
be so very sharply distinguished from the Copepoda, may thus be found to have in fact
its homologue also in the latter Crustacea.

Homology of the Eyes.—The eyes form another character wrongly adduced to show
the affinity of Nebalia to the Podophthalmia. In reality the eyes in the Nebaliide,
though properly termed stalked and mobile, differ essentially from those in the Podoph-
thalmia by their much simpler structure and by the want of a distinct facetted cornea.
On the other hand, they are found to agree, both as to form and structure, very closely
with the eyes in a well-known family of the Phyllopoda, the Branchipodide.

Homology of the Antennule.—These limbs certainly exhibit a structure very different
from that met with in other Branchiopoda, but they are also quite dissimilar to the
corresponding limbs in the Podophthalmia, differing essentially as well by the abnormal
number of joints in the peduncle, this being in all higher Crustacea invariably but three,
as also by the peculiar setose lamella appended to the end of the peduncle. To compare
this lamella, as proposed by some authors, to the so-called antennal scale belonging to
the succeeding pairs of limbs, the antennz, in Decapods and Schizopods, is, in my
opinion, quite unreasonable. Neither can it properly be regarded as homologous with the
inner flagellum in these Crustacea or to the accessory flagellum in the Amphipoda, since
it is affixed outside the true flagellum, which latter undoubtedly answers to the outer
flagellum in other Crustacea, bearing, as it does, the characteristic sensory appendages,
generally termed olfactory cilia. Thus the lamella under consideration cannot properly
be compared to anything met with in the higher Crustacea, but apparently represents a
characteristic feature peculiar to the Nebaliide. I think we may better understand the

32 THE VOYAGE OF H.M.S. CHALLENGER.

structure of the antennule in the latter forms by instituting a comparison with the cor-
responding limbs in the Copepoda. Thus, in the Harpactoidea we find that the anterior
pair of antennee, which undoubtedly answer to the antennule in the Nebaliidee, are
composed each of two rather distinctly defined divisions, a thicker proximal part and a
much narrower distal part, the former consisting pretty constantly of four articulations,
the last of which forms anteriorly a lateral expansion bearing a slender, ribbon-like
appendage, the latter composed of a varying number of articulations but always very
sharply marked off from the proximal part. There cannot in my judgment be any doubt
that the proximal part of the anterior antennze in these Copepoda answers to the anten-
nular peduncle in the Nebaliide, and the distal part to the flagellum. The lateral
expansion of the last joint of the proximal part in the former is also well seen in the
Nebaliide, and, moreover, in all probability the ribbon-like appendage affixed to that
expansion in the Harpactoidea is a homologue of the setose lamella in the Nebaliide.
Thus, all parts of the antennulee in the latter forms seem to be in fact represented in the
Copepod antennula, and the apparently abnormal number of joints in the peduncle as
compared with that in the higher Crustacea, will turn out to be quite normal in relation
to the Copepoda.

Homology of the Antenne.—In comparing the antennze in the Nebaliidee with those
in the higher Crustacea, we find at once their structure very different from that in any
known form of the Podophthalmia, whereas they at first sight somewhat resemble the
lower antennee in the Amphipoda. On closer examination, however, it is easily found
that they differ materially also from those in the last named group of Crustacea by the
peduncle being only triarticulate, whereas in all known Malacostraca the number of joints
is far greater, generally amounting to five in all. Moreover, the peculiar geniculate
bend at the middle of the peduncle is rather different from what is generally met with
in the Malacostraca. I think we may also in the case of these limbs more properly
derive their structure from that met with in the Copepoda, especially those of the
Harpactoid group. In these Copepoda the posterior antennze are, as is well known,
very small but composed of three distinctly defined segments, the last of which forms
with the preceding a strong geniculate bend, and it may readily be found, by comparison,
that these three segments together perfectly agree in form with the antennal peduncle
in the Nebaliide. At the tip of the last joint, moreover, in some forms a small
imperfectly defined terminal joint may be distinguished, representing a rudiment of the
flagellum. The accessory branch generally found affixed to the middle of the second
segment is sometimes quite obsolete, whereby the accordance becomes still more pro-
nounced. The peculiar modification of the flagellum in the male of Nebalia, somewhat
similar to what is met with in the Amphipoda and Cumacea, does not seem to have any
more general significance, since in the nearly related genus Paranebalia there is
no difference whatever to be found in the antenne of the male and female, whereas it

REPORT ON THE PHYLLOCARIDA. 33

is here only the antennule which are peculiarly modified, as is also the case in the
Copepoda.

Homology of the Oral Parts.—These appendages appear on the whole very dissimilar
to those in other Branchiopoda, and their structure has consequently been adduced to
show the closer affinity of Mebalia to the Podophthalmia. Especially is the great
development of the mandibular palp certainly a very characteristic feature, since such a
palp is never met with in any adult Branchiopod. In form this palp, however, exhibits,
as has also been pointed out by Professor Claus, a much closer resemblance to that in
the Amphipoda than to the palp in the Podophthalmia, and the structure of the
mandible itself is also rather different, showing, by the reduction of the cutting edge and
the great development of the molar surface, more similarity to that met with in the
greater part of the Branchiopoda. In the Copepoda the mandibles are, as is well known,
in most cases provided with a well-developed palp, but this palp is generally biramose
or bears a so-called branchial appendage, which however is often very reduced in size
and in some forms even quite obsolete, whereby the palp acquires a certain similarity to
the mandibular palp in the Nebaliidee. The very slight development of the posterior lip
or metastoma in the Nebaliidee is a character apparently more in accordance with the
Entomostraca than with the Malacostraca, in which latter this part is always well
developed and rather large. As to the structure of the maxille, both pairs seem to me
to be essentially different from those in the higher Crustacea, and especially is the
structure of the first pair quite peculiar and only admits of a very general comparison
with those in other Crustacea. In the structure of the second pair I find, however, a
well-marked resemblance to the maxille in a great number of Copepoda, and this
resemblance is especially very striking in the case of the genus Nebaliopsis, as stated
above. In the Copepoda, it is true, only a single pair of maxilla are present, but this
pair I think may more properly be regarded as homologous with the second pair in the
Nebaliide, the first pair not being developed in the former Crustacea. The number of
maxille in the Nebaliidee cannot be adduced as showing their affinity to the Macacostraca,
since we find at least in all Phyllopoda both pairs distinctly developed, though of a
rather simple structure.

Homology of the Branchial Legs —These limbs, in my opinion, undoubtedly stamp
the Nebaliide as true Branchiopoda, agreeing, as they do, both in structure and function
with the so-called branchial feet in other forms of this order. This has, however, been
partly combated by some naturalists, who regard them as more closely agreeing with
the thoracic legs in the Schizopoda; and, in fact, if we had confined our examination to
the structure of these limbs in the above described genus Paranebalia, such a view
might perhaps to a certain extent be advocated, as in this form they certainly exhibit an
appearance somewhat approaching that of the legs in the Euphausiidee. On the other
hand, I think, that no one will find any trace of similarity between the simple lamelli-

(ZOOL. CHALL, EXP.—PART LVI.—1887.) Kkk 5

34 THE VOYAGE OF H.M.S. CHALLENGER.

form branchial legs in Nebaliopsis and the thoracic legs of any Schizopod or other
Malacostracan. In both these genera, however, these limbs are constructed upon the
same general plan, the chief agreement being found in their adaptation for solely respir-
atory purposes, and in so far they very materially differ from the thoracic legs in the
Malacostraca. In Nebalia the branchial legs hold an intermediate position and
consequently exhibit the most typical structure, whereas in the two above named generic
types they represent, as it were, the extremes of a series of modifications, apparently
standing in some connection with the very different conditions of life in the two, the
one being a shallow-water form, the other a very marked deep-water form. That these
limbs in Nebalia are much more closely related in structure to the branchial legs in
other Branchiopoda, than to the thoracic legs in the Malacostraca, cannot in my opinion
be disputed. It is true that they somewhat differ from the branchial legs in the
Phyllopoda by the want of the so-called endites or lateral lobes of the endopodite. But
it must be remembered, that these endites are only peculiar to the Phyllopoda, whereas
in other undoubted Branchiopoda, as the Cladocera, they are more or less completely
obsolete. Nor can it properly be adduced in support of the assumption of the: nearer
relationship of Nebalia to the Schizopoda, that the “ thoracic” legs in the former exhibit
the same principal parts as in the latter, since these parts, viz., the endopodite, exopodite,
and epipodite, may easily be distinguished in Crustacea belonging to very different
groups, and in most other Branchiopoda are quite so well definable as in Nebalia. The
number of these limbs in all the known recent Phyllocarida is eight pairs, and if we
consider the anterior pair as homologous with the maxillipeds in the Malacostraca, the
number will certainly answer to that of the thoracic legs in these Crustacea, whereas
their number in other Branchicpoda is very variable and at least in the Phyllopoda is
much greater. But on closer examination we shall find that the anterior pair of branchial
legs in the Nebaliidee evidently belong to the trunk and not to the cephalic part, as do
the maxillipeds in all the known Malacostraca, and even in the Euphausiidee, where the
maxillipeds are constructed upon the very same type as the succeeding legs, the
development shows them clearly to belong to the head and not to the trunk.’ It thus
results that the maxillipeds are wanting in the Nebaliidee, and that the number of the
limbs belonging to the trunk is in reality greater than in the Malacostraca. In the
Copepoda these limbs are only represented by the so-called maxillipeds, which according
to the suggestion of Professor Claus may properly be regarded as the outer and inner
branches of a single pair of limbs.

Homology of the Pleopoda and Caudal Limbs :—The great agreement both in form
and composition between the two posterior divisions of the body in the Nebaliide and
the so-called “thorax” and “abdomen” in the Copepoda, has been stated above. This
agreement becomes still more evident by a comparison of the respective appendages.

1See my Report on the Challenger Schizopoda, Zool. Chall. Exp., pt. xxxvii.

REPORT ON THE PHYLLOCARIDA. 35

Thus, the pleopoda in the Nebaliidze undoubtedly agree very closely with the swimming
legs in the Copepoda both as to structure and number, whereas their affinity to the
pleopoda in the Malacostraca is much more remote. To compare them to the caudal
limbs or the so-called saltatory legs in the Amphipoda, as proposed by Professor Claus, is,
I think, objectionable, since the latter limbs belong to a different division of the body
and more properly answer to the rudimentary caudal limbs in Nebalia. As to the mode
in which the pleopoda are moved, we find also the greatest resemblance between Nebalia
and the Copepoda, especially those of the Harpactoid group, the movements being not at
all rhythmical nor performed in the same rapid and almost vibratile manner as in the
Amphipoda and most Podophthalmia (Euphausiidee). The two rudimentary caudal limbs
in the Nebaliidee likewise find their homologues in the Copepoda. The first of these pairs
are thus evidently homologous with the generally very small and imperfectly developed
so-called last thoracic legs in the latter Crustacea, and on closer examination we shall find
that also the second pair of these limbs are represented in the Copepoda, though in a
very rudimentary state. Thus, on the segment succeeding the so-called last thoracic
segment in the latter Crustacea, and generally described as the first abdominal segment,
there occur in most of the forms on each side, close to the genital orifice, a small tubercle
provided with a few spine-like bristles. This tubercle, more distinct in the males, is
undoubtedly the rudiment of a pair of limbs, evidently answering to the second pair of
rudimentary caudal limbs in the Nebaliidee. The succeeding segments in the Copepoda
as also in the Nebaliide are entirely devoid of any trace of limbs, and in most of the
Harpactoidea these segments exhibit a denticulate armature on the hinder edge quite
similar to that in the Nebaliide. Finally, the caudal rami appended to the last segment
in the Nebaliidz are undoubtedly homologous with the so-called “ furca”’ in the Copepoda,
as also with the caudal lamelle in the Branchipodide, being not true limbs but more
properly representing a bipartite terminal segment. These terminal appendages in the
Nebaliide are therefore not at all homologous with the so-called uropoda in the Mala-
costraca, the latter being true ventral limbs.

Homology of the Internal Organs.—The internal organisation of Nebalia, which I
have also thoroughly studied in the northern form Nebalia bipes, may on the whole be
said to be much more advanced than in any other of the known Entomostraca, but I do
not find in this respect any closer resemblance to that of the Podophthalmia, whereas it
exhibits some points of apparent affinity to that met with in the Amphipoda.

The nervous system seems in fact to differ essentially in structure from that generally
met with in the other Branchiopoda by the ganglionic cord being not double but forming
a single median series of ganglia, as in most Malacostraca. It must, however, be
remembered, that the peculiar double ladder-like ventral cord, though very characteristic
of the Branchiopoda, does not form a universal character of these Crustacea. Thus,
among the Cladocera we find the nervous system in Leptodora wholly dissimilar from

36 THE VOYAGE OF H.M.S. CHALLENGER.

that in the other forms, and also in the Branchiura the nervous cord is constructed upon
a quite different type.

The intestine in Nebalia is markedly distinguished by the presence of a chitinous
visceral skeleton never found in any Branchiopoda; but this skeleton does not show
any resemblance to that found in the Podophthalmia, whereas its similarity to that
found in the Amphipoda is unmistakable. With the latter Crustacea Nebalia also
apparently agrees in the two pairs of elongate ceeca arising from the gastric part and
accompanying the intestine in the greater part of its length, and more especially in the
presence of another pair of elongate ceecal appendages originating from the terminal part
of the intestine and running anteriorly along its dorsal side. On the other hand, the
occurence of two short curved czeca, projecting forwards within the head, is a character
pointing rather more to the Branchiopoda, in some of which, as in the genus Daphma,
we find two quite similar curved ceeca arising from the anterior part of the intestine.

As to the structure of the heart the genus Nebalia may equally well be compared
with the Branchiopoda as with other Crustacea, since the structure of this organ in. the
former is very variable, being in some forms quite short and sac-like with only a single
pair of lateral venous fissures, in other forms more or less elongate with a varying number
of such fissures. As in the Branchiopoda the vascular system is imperfectly developed,
though a pair of short arteries may be traced at each end of the heart.

The generative organs in both sexes, as in most of the Branchiopoda, are rather
similar and very little complicated in structure, forming merely a pair of simple
eylindrical tubes extending along the sides of the intestine, and opening by a short
excretory duct on the ventral surface of the last segment of the trunk. In the
Podophthalmia these organs are, as is well known, much more complicated, and,
moreover, always exhibit a very marked difference in their structure in the two
SEXES.

Development.—The development of Nebalia cannot in my judgment be adduced as
showing any close affinity between this form and the Decapoda, as suggested by
Metschnikoff ; and this has partly also been admitted by Professor Claus, in so far, at
least, that he has pointed out that the stage of the MNebalia-embryo, termed by
Metschnikoff the Zoea-stage, and on which this author chiefly bases his suggestion of
the decapodous nature of Nebalia, does not in reality correspond to that stage in the
Podophthalmia, but more properly to the earliest stage of the Cyclops-form in the
Copepoda. Neither can I find that the supposed agreement between the development
of Nebalia and that of Mysis points to any true consanguinity between these genera.
As is well known, we find a very similar direct development also in a great number of
other Crustacea not at all belonging to the Podophthalmia, as in the Cumacea and
Isopoda, and even in the Phyllopoda I have recently had an opportunity of stating an
instance of a quite direct development, without any metamorphosis, and agreeing, more-

REPORT ON THE PHYLLOCARIDA. 37

over, in all essential points rather well with that found in Nebalia The apparent
agreement with the Schizopoda in the mode in which the ova and embryos are borne in
Nebalia during their development, is considerably lessened by the circumstance that
there is in the latter form no trace of any true incubatory pouch, the ova being simply
received within the valves of the carapace and kept in place by the aid of the branchial
legs.

Concluding Remarks on the Phylogeny of the Nebaliide.—Owing to the suggestion
made by most naturalists, that Nebalia forms a direct transition between the Phyllopoda
and Podophthalmia, it has generally been supposed that the Nebaliidee have descended
from the Phyllopoda, and that, on the other hand, all the Podophthalmia should be
regarded as descendants from Nebalia-like ancestors. In his interesting treatise on the
phylogenetic relationship of the Malacostraca, Dr. Boas has sought to strengthen the
latter supposition by instituting a close comparison of the limbs in Nebalia with those
in the Malacostraca, and has thereby been led to the result, that the connecting link
between Nebalia and the great bulk of the Podophthalmia is represented by the
Euphausiidee, from which again all the other forms of that division are supposed to have
descended. It would seem that the chief reason that has led Dr. Boas to this view as
to the supposed close relationship between Nebalia and the Euphausiide, is the apparent
agreement in the number of segments composing the anterior division of the body
(cephalothorax), and the uniformity in structure of the eight pairs of limbs succeeding
the oral parts in both. For in all other points the difference is in reality so very great,
as in most cases only to admit of the statement of a very general homology, such as
could also be made by comparing almost any forms of Crustacea. It has been stated
above that the resemblance of the branchial legs to the legs in the Euphausiide is in the
genus Paranebalia considerably more pronounced than in Nebalia. But notwithstanding
this agreement, I still believe that there is no true relationship between the Nebaliide
and the Kuphausiide, and that the above mentioned apparent conformity in the con-
struction of some of the limbs in both is merely accidental, a view that seems also to be
confirmed by the fact that in an otherwise closely related genus, Nebaliopsis, these
limbs exhibit a form showing no similarity whatever to the corresponding limbs in the
Euphausiide. If any true consanguinity had existed between the Nebaliide and the
Euphausiide, the agreement between the two would certainly not be restricted to the
above named limbs, but might have been traced also in the rest of the organisation. But
this is by no means the case. On the contrary, it may easily be found on closer com-
parison, that the Huphausiidee in so far differ from the Nebaludee even considerably
more than is the case with a great number of other Malacostraca.

As to my own view on the probable phylogenetical relation of the Nebaliidee to other

1 On Cyclestheria hislopi (Baird), a New Generic Type of Bivalved Phyllopoda, Forhandl. Vidensk. Selsk. Christ.,
1887 (to be shortly published).

38 THE VOYAGE OF H.M.S8. CHALLENGER.

Crustacea, I am inclined to agree on the whole with the suggestion set forth by Dr. A.
Packard in his valuable treatise on the Phyllopod Crustacea of North America, believing
that the Nebaliidee may have descended from some Copepod-like ancestors, whereas they
do not show any relation whatever to the Podophthalmia, the latter having in all
probability developed independently by a separate line from some Nauplius- or Zoea-like
form. From the same stem that gave origin to the Nebaliide, I think that also the
other Branchiopoda may be derived, the latter having apparently become rather con-
siderably modified in various ways to adapt them to the somewhat exceptional conditions
under which they live, whereas the Nebaliidz have still preserved much of the external
appearance which may have distinguished the progenitors of the order, while their
internal organisation has become much more modified.

TABLE OF CONTENTS.

INTRODUCTION, .
PrincipaL WorkKS ON Recent Poytuocaripa, .
GrNERAL REMARKS ON THE MorrHoLocy oF THE PayLLocariDa,
DEFINITION OF THE Faminy NEBALIIDA,
DESCRIPTION OF GENERA AND SPECIES, .
NEBALIIDE, .
Paranebalia, Claus,
longipes (Willemoes Suhm),
Nebaliopsis, n. gen.,
typica, N. sp.,
Homooey oF THE RECENT PyLLocARIDA,
Homology of the Body-Divisions, .

x 5, Carapace,

” ”? Ey es,
Antennule,
yy » Antenne,
» », Oral Parts,
Branchial Legs, .
Pleopoda and Caudal Limbs,
Internal Organs,

Development,

Concluding Remarks on the Phylogeny of the Nebaliide, .

ae
=

PLATE J.

(ZOOL. CHALL. EXP,—PART Lv1.—1887.)—Kkk.

\

Fig.

Wig. 2.
Fig. 3.
Fie. 4.
Fie. 5.
Fig. 6.
Fig. 7.
Vig. 8.
Fig. 9.
Fig. 10.
Fig. 11.
Fig. 12.
Fig. 13

PEATE Ae

Paranebalia longipes (Willemoes Suhmn).

1. Adult female, seen from the left side; magnified about thirty-four diameters.

The specimen has been rendered pellucid by mounting in Canada balsam,
so as to exhibit 7 situ the several limbs covered by the carapace, as also
some of the internal organs. , rostral plate; O, eye; a’, antennula; a?,
antenna; JZ, mandible; Mp, mandibular palp; m’, maxilla of first pair ;
m, maxilla of second paw; brp, branchial legs; pl, pleopoda; ep’, ep”,
rudimentary caudal limbs of first and second pairs; wr, caudal rami; Cin,
adductor muscle of carapace ; Ov, ovary.

Rostral plate, seen from below ; magnified fifty diameters.

Left eye, lateral view.

Left antennula.

One of the olfactory filaments from the flagellum of same ; highly magnified.
Serrate projection of last segment of peduncle of same.

Left antenna.

Anterior lip, seen from below.

Mandibles, together with the palps and adductor muscle ; front view.
Masticatory part of a mandible; more highly magnified.

Mandibular palp, lateral view.

Maxilla of first pair.

. Maxilla of second pair.

The Voyage of H.M S’Challenger
rate Phyllocarida,Pl |

G.0. Sars,del. Lith.W. Schlachter, Stockhol:

PARANEBALIA LONGIPES, (Will. Suhm).

PLATE Il.

dD.

6.

PLATE IL.

Paranebalia longipes (Willemoes Suhm)—continued.
Adult female, viewed from above ; magnified about thirty-four diameters.
Branchial lee of first pair; magnified fifty diameters.
Branchial leg of fifth pair.
Branchial leg of last pair.
Pleopod of first pair.

Pleopod of second pair.

6a. Lateral lobe of inner branch of same ; more highly magnified.

6b. One of the chitinous hooks from the same lobe; magnified three hundred and

cof

10.

el:

12.

eighty diameters.
Pleopod of last pair.
First pair of rudimentary caudal limbs.
Rudimentary caudal limb of second pair.
Last caudal segment, together with right caudal ramus, seen from below.

Embryo taken from the incubatory cavity of an adult female specimen, seen
from below; magnified seventy-eight diameters. R, rostral plate; O, eyes;
a’, antennule ; a, antenne ; L, anterior lip; M, mandibles; m', maxillee
of first pair; m*, maxillee of second pair; brp, branchial legs ; pl, pleopoda;
ur, caudal rami.

Same embryo, viewed from the right side. C{ carapace ; remaining letters as
in fig. 11.

Phyllocarida P1.II.

The Voyage of H MS'Challenger’”

Lith W Schlachter, Stockholm.

G.0.Sars del.

PARANEBALIA LONGIPES, (Will. Suhm).

PLATE Il.

(ZOOL. CHALL, EXP.—PART LVI.—1887.)—Kkk.

oo

PLATE III.

Nebaliopsis typica, n. gen. et sp.
Young specimen, viewed from the left side; magnified about five diameters.
Same specimen, ventral aspect.

Right branchial leg of seventh pair from same specimen ; magnified twenty-four

chameters.
Pleopod of third pair from same specimen.

Carapace of another, apparently adult specimen, seen from the left side; very
slightly magnified.

Same carapace, viewed from above.
Rostral plate of same specimen, seen from above ; somewhat more magnitied.

Fragment of the cephalic part of same specimen together with its several
appendages, viewed from the left side ; magnified about five diameters.
O, eye; a’, antennula; a’, antenna; L, anterior lip; MM, mandible; Mp,

mandibular palp.

Same fragment, front view. The terminal part of the antennul as also the
antennee and mandibles are omitted. O, eyes; a’, bases of the antennule;
L, anterior lip.

Maxilla of second pair from same specimen; magnified fourteen diameters.

Phyllocarida, PL III.

f H.M.S'Challenser”

The Voyage o

fe

|
|
|

hter, Stockholm

lath W.Schlac

6.0. Sars, del

NEBALIOPSIS TYPICA,n. gen. & sp.

4
'