nd aan ea dca STS eee hack

HARVARD, ‘UNIVE Rolt ¥.

LIBRARY

OF THE

MUSEUM OF COMPARATIVE ZOOLOGY.

gal
B
Koay» — Dotgber. Ib, /900

J,

QUARTERLY JOURNAL

MICROSCOPICAL SCLENCH.

E. RAY LANKESTER, M.A., LL.D., F.R.S.,

HONORARY FELLOW OF EXETER COLLEGE, OXFORD; CORRESPONDENT OF THE INSTITUTE OF FRANCE,
AND OF THE IMPERIAL ACADEMY OF SCIENCES OF ST. PETERSBURG, AND OF THE ACADEMY
OF SCIENCES OF PHILADELPHIA; FOREIGN MEMBER OF THE ROYAL BOHEMIAN
SOCIETY OF SCIENCES, AND OF THE ACADEMY OF THE LINCEI OF ROME;
ASSOCIATE OF THE ROYAL ACADEMY OF BELGIUM; HONORARY MEMBER
OF THE NEW YORK ACADEMY OF SCIENCES, AND OF THE
CAMBRIDGE PHILOSOPHICAL SOCIETY, AND OF THE ROYAL
PHYSICAL SOCIETY OF EDINBURGH ; HONORARY
MEMBER OF THE BIOLOGICAL SOCIETY
OF PARIS;

DIRECTOR OF THE NATURAL HISTORY DEPARTMENTS OF THE BRITISH MUSEUM; FULLERIAN PROFESSOR

OF PHYSIOLOGY IN THE ROYAL INSTITUTION OF GREAT BRITAIN.

WITH THE CO-OPERATION OF

ADAM SEDGWICK, M.A., F.RS.,

FELLOW AND TUTOR OF TRINITY COLLEGE, CAMBRIDGE 5

W. F. R. WELDON, M.A., F.R.S.,

LINACRE PROFESSOR OF COMPARATIVE ANATOMY AND FELLOW OF MERTON COLLEGE, OXFORD;
LATE FELLOW OF ST. JOHN’S COLLEGE, CAMBRIDGE 5

AND

SYDNEY J. HICKSON, M.A., F.R.S.,

BEYER PROFESSOR OF ZOOLOGY IN THE OWENS COLLEGE, MANCHESTER.

VOLUME 43.—New SErRIEs.

Gith Aithographic Plates and Engrabings on dlood

i

LONDON:
& A. CHURCHILL, 7, GREAT MARLBOROUGH STREET.
1900,

CONTENTS.

CONTENTS OF No. 169, N.S., FEBRUARY, 1900.

MEMOIRS: PAGE
Contributions to the Embryology of the Marsupialia. Parts II and
Il. By Jas. P. Hitt, B.Se.Edin., F.L.8., Demonstrator of
Biology in the University of Sydney, New South Wales. (With

Plates 1 and) : ‘ ‘ : : : : i

Studies in the Retina: Rods and Cones in the Frog and in some
other Amphibia. By H. M. Bernarp, M.A.Cantab. (from the
Biological Laboratories of the Royal College of Science). (With
Plate’) . f ; , : | 98

On the Sensory Pit of the Crotaline. By G. 8. West, B.A.,
A.R.C.S., Student. of St. John’s College, Cambridge. (With
Plate 4) . : : ; . 49

A Re-investigation of the Early Stages of the Development of the
Mouse. By J. W. Jenxryson, M.A. (With Plates‘ and6) . 61

The Structure of the Rostellum in Two New Species of Tapeworm,
from Apteryx. By W. Braxtanp Benuam, D.Sc., M.A., Pro-
fessor of Biology in the University of Otago, New Zealand.
(With Platey7 and 8). ; ; aye < eis

The Habits and Karly Development of Cerebratulus lacteus
(Verrill). A Contribution to Physiological Morphology. By
Cuas. B. Witson. (With Plates 9—11) 5 : » OF

CONTENTS OF No. 170, N.S., APRIL, 1900.
MEMOIRS:

On the Reaction of Daphnia magna (Straus) to certain Changes
in its Environment. By Ernest Warren, D.Sc., University
College, London , : 3 : : . 199

iv CONTENTS.

A Revision of the Genus Steganoporella. By Sipnny F,
Harmer, 8e.D., F.R.S., Fellow of King’s College, Cambridge ;
Superintendent a the University Museum of ma (With
Plates 12 and 13) :

On a New Histriobdellid. By Witttam A. Haswett, M.A,,
DSc; RSs Challis Professor of Bee University of
Sydney. (With Plates 14 and 15) : :

On Spongioporphyrin : the Pigment of Suberites Wilsoni. By
C. A. MacMunn, M.A., M.D. (With Plate 16)

Further Remarks on the Development of Amphioxus. By E. W.
MacBripg, M.A., D.Se.(Lond.), Professor of Zoology in McGill
University, Montreal. (With Plate’17)

Quelques Observations sur les Onychophores (Peripatus) de la
Collection du Musée Britannique. Par E. L. Bouvirr, Pro-
fesseur au Muséum d’Histoire Naturelle de Paris

On the Diplochorda. TIT. The Early Development and Anatomy
of Phoronis Buskii, Mcl. By Arrnur T. Mastermay,
M.A.(Cantab.), D.Se. Guond: and St. A.), Lecturer on Zoology i in
the New Medical School, Edinburgh. (With Plates” 18—21)

CONTENTS OF No. 171, N.S., JULY, 1900.

MEMOIRS:

The Anatomy and Classification of the Arenicolide, with some
Observations on their Post-larval Stages. By F. W. Gampte,
M.Sce., and J. H. Ashwortn, D.Sec., Demonstrators and Assistant
Lecturers in Zoology, Owens College, Manchester. (With Plates

~99—99) .

Diagrams illustrating the Life-History of the Parasites of Malaria.
By Ronautp Ross, D.P.H., M.R.C.S., Lecturer in Tropical
Medicine, University College, Liverpool, and R. Fretprne -Ouxp,
M.A., M.B., Acting Demonstrator, Liverpool School of Tropical
Medicine. (With Plates‘30 and 31)

Note on the Morphological Significance of the Various Phases of
Hemameebide. By HE. Ray LaAnKester

PAGE

225

299

337

351

367

419

571

581

CONTENTS.

CONTENTS OF No. 172, N.S., SEPTEMBER, 1900.

MEMOIRS:
Hippolyte varians: a Study in Colour-change. By F. W. GamBue,
D.Se., Owens College, Manchester, and F. W. Keene, M.A.,
Caius College, Cambridge ; late Assistant Lecturer in Botany,
Owens College, Manchester. (With Plates 32—36)

On the Nephridia of the Polycheta. Part III. The Phyllodocide,
Syllide, Amphinomide, etc., with Summary and Conclusions.
By Epwixn S Gooprica, M.A., Aldrichian Demonstrator of
Comparative Anatomy, Oxford. (With Plates'37—42)

Nouvelles Observations sur les Peripatus de la Collection du Musée
Britannique. Par E. L. Bouvrer, Professeur au Muséum
d’Histoire Naturelle de Paris

Tirne, INDEX, AND CONTENTS.

VoL. 43.—NEW SERIES. b

PAGE

699

749

‘7; , ae) eT ie

= ce “ahs 7 he a.
Uae ite Nea eee a 2 dy:
ae ae a 7 io 7
PVN ay + (a - Hae EF if 2yLe | ;
: wri St ; hy OF ty he ‘nn mei: ra
Hol en ee, Ge eh <e Porhiidaes, Pai
=. De a | y-1) eas's elt age Lan

wv

_

“a a aT ie ) ; ‘Ris limewne 4 eed -
a, ON fe onavang
\ r f DAO. P. Bte ae 0) @U eed
fh ur’ 1 fn 2 Ai seer’ ge Hal.
Pre ith. J Th , ( ' , . < sT iy =i ar
: : bast
wi 4

MAY 7 1900

New Series, No. 169 (Vol. 43, Part 1). Price 10s.

FEBRUARY, 1900.

| THE

QUARTERLY JOURNAL

OF

MICROSCOPICAL SCIENCE.

EDITED BY

HK. RAY LANKESTER, M.A., LL.D., F.R.S.,

HONORARY FELLOW OF EXETER COLLEGE, OXFORD; CORRESPONDENT OF THE INSTITUTE OF FRANCE,
AND OF THE IMPERIAL ACADEMY OF SCIENCES OF ST. PETERSBURG, AND OF THE ACADEMY
OF SCIENCES OF PHILADELPHIA} FOREIGN MEMBER OF THE KOYAL BOUEMIAN
SOCIETY OF SCIENCES, AND OF THE ACADEMY OF THE LINCEI OF ROME;
ASSOCIATE OF THE ROYAL ACADEMY OF BELGIUM; HONORARY MEMBER
OF THE NEW YORK ACADEMY OF SCIENCES, AND OF THE
CAMBRIDGE PHILOSOPHICAL SOCIETY, AND OF THE ROYAL
PHYSICAL SOCIETY OF EDINBURGH } HONORARY
MEMBER OF THE BIOLOGICAL SOCIETY
OF PARIS}

DIRECTOR OF THE NATURAL HISTORY DEPARTMENTS OF THE BRITISH MUSEUM; FULLERIAN PROFESSOR

OF PHYSIOLOGY IN THE ROYAL INSTITUTION OF GREAT BRITAIN.

WITH THE CO-OPERATION OF

ADAM SEDGWICK, M.A., F.RS.,

FELLOW AND TUTOR OF TRINITY COLLEGE, CAMBRIDGE 5

AND

W. F. R. WELDON, M.A., F.RS.,

LINACRE PROFESSOR Ol COMPARATIVE ANATOMY AND FELLOW OF MERTON COLLEGE, OXFORD;
LATE FELLOW OF ST. JOHN’S COLLEGE, CAMBRIDGE.

WITH LITHOGRAPHIC PLATES AND ENGRAVINGS ON WOOD.

LONDON:
J. & A. CHURCHILL, 7, GREAT MARLBOROUGH STREET.

1900.

Adtard and Son,] [Bartholomew Close.

oe

CONTENTS OF No. 169.—New Series.

MEMOIRS:

PAGE
Contributions to the Embryology of the Marsupialia. Parts II and

Ill. By Jas. P. Hitt, B.Se.Kdin., F.L.S., Demonstrator of Biology
in the University of ae New South Wales. (With Plates
l and 2) 5 : ; 5 ; ; , ; < iL

i}
Studies in the Retina: Rods and Cones in the Frog and in some other
Amphibia. By H. M. Bernarp, M.A.Cantab. (from the Biological
Laboratories of the Royal College of Science). (With Plate 8) a age

On the Sensory Pit of the Crotaline. By G. S. West, B.A.,
A.R.C.S., Student of St. Jolin’s College, Cambridge. (Witn
Plate 4) ‘ : : ; ; ; : ; - : . 49

A Re-investigation cf the Early Stages of the Development of the
Mouse. By J. W. Jenkinson, M.A. (With Plates 5 and 6) lO

The Structure of the Rostellum in two New Species of Tapeworm,
from Apteryx. By W. Buaxtanp Benuam, D.Sc., M.A., Professor
of Biology in the University of Otago, New Zealand. (With Plates
7 and 8) : : : : : : : : ; : tetra

The Habits and Karly Development of Cerebratulus lacteus
(Verrill). A Contribution to Physiological Morphology. By
Cuas. B. Witson. (With Plates9—11) . ; ; : : oe

may 7 1900

Contributions to the Embryology of the
Marsupialia.

By

Jas. P. Hill, B.Sc.(Edin.), F.L.S.,
Demonstrator of Biology in the University of Sydney, N.S.W.

With Plates 1 and 2.

II. On a Further Stage in the Placentation of Perameles.

In the present paper I deal with a stage in the placenta-
tion of Perameles somewhat later than my previous Stage D
(1). Beyond the demonstration of the persistence of the entire
yolk-sac wall, no strikingly new facts have been brought to
light in the investigation, but I have been enabled to essen-
tially confirm my previous account, and also to add some
fuller information on certain points of detail, especially as
regards the yolk-sac vessels. In addition, I give an account,
in the sequel, of the foetal membranes of a species of
Macropus, for comparison with those of Perameles, and I
also take this opportunity of offerig some further remarks
on the phenomena of parturition, and of correcting a mis-
interpretation contained in my previous account of that
process, since an extended investigation’ into the morpho-
logy of the female urogenital organs of Perameles, with
special reference to the phenomena of parturition, has con-

1 Communicated to the Linnean Society of New South Wales, March,

1899.
VoL. 43, PART 1.—NEW SERIES. A

2 JAS. P. AIL.

vinced me that “the common uterine canal” of my former
paper is in reality formed by the union posteriorly of two
median vaginal cul-de-sacs, which constitute a median
vaginal apparatus homologous to that existing in other
Marsupials. If for the above misleading expression the reader
will substitute common median vagina, the main facts in my
previous short account of the process of parturition remain
substantially correct.

It is with much satisfaction, in view of my interpretation
of the allantoic placenta of Perameles as a primitive feature
of its organisation, that I am thus enabled to bring its appa-
rently peculiar parturition phenomena into line with those
occurring in certain other Marsupials, which, like Perameles,
give birth to the young through a direct median passage.
Further, the investigation above referred to has led me to
the conclusion that the urogenital organs of Perameles are in
a condition which can only be described as _ persistently
embryonic, and which is without doubt much more primitive
than that existing in any other Marsupial hitherto described,
a conclusion which I believe serves materially to strengthen
the position I have taken up as regards the significance of
the occurrence of an allantoic placenta in the genus.

My work for the past year has been carried out with the
aid of a grant from the Royal Society, to whose Committee I
desire to express my grateful thanks.

Stace D.—P. OBESULA.

The female, a specimen of the short-nosed Bandicoot, P.
obesula, upon the examination of whose genital organs the
account of the present stage is based, came into my hands a
few hours after death. Post-mortem change, however, was
not at all apparent, and the genital organs were at once cut
out and preserved in picro-nitric acid.

Both uteri were much enlarged ; the right measured 22 mm.
in length by 11 mm. in breadth, the left 21 mm. by 15 mm.
Each contained a single embryo (PI. 1, fig. 3), measuring in

EMBRYOLOGY OF THE MARSUPIALIA. 3

greatest length 12°5 mm. and in head length 6:5 mm. Its
structural characteristics are given in the Appendix.

Both uteri were submitted to macroscopical examination,
while the right uterus and its embryo were alone examined
microscopically.

Forat Mempranes.—In fig. 1, Pl. 1, the embryo is
shown in situ in the right uterus, the ventral wall of which
has been removed. It was noticed at once that the yolk-sac
wall was not even slightly adherent to the surface of the
mucosa. Whether this non-adherence is due to post-mortem
change or to natural causes I am unable to decide. It is
quite possibly due to the latter, since the yolk-sac placenta is
now in a largely degenerated condition.

In the figure, the vasculur omphalopleure and the yolk-sac
splanchnopleure, which were cut through along their line of
attachment to the margin of the allantoic placental area, have
been reflected outwards. The embryo is seen lying on its
right side, with its head end next the anterior end of the
uterus, and its long axis in the antero-posterior axis of the
same. In the left uterus the head of the embryo lay next
the posterior end of the uterus, so that its position is an
inconstant one. The embryo is situated, of course, in the
extra embryonic splanchnoccele, which has been opened into
by the reflection of the yolk-sac splanchnopleure, and is
invested by the amnion. The latter is reflected from the
distal end of the thick stalk, which arises from the mid-region
of the ventral abdominal wall. This stalk—the umbilical
stalk (fig. 1, uw. s.)—is a tubular prolongation of the abdo-
minal wall, which encloses a portion of the ccelom, and the
upper ends of the allantoic and yolk-stalks (fig. 4, Pl. 1).
From the yolk-stalk the yolk-sac splanchnopleure is reflected
closely round the embryo. It becomes continuous with the
vascular omphalopleure, along the line of union of the latter
with the marginal zone of chorion which is present round the
allantoic placental area.

The allantoic stalk (fig. 1, all. s.), on leaving the umbilical
stalk, passes outwards and forwards, and then, curving

4, JAS. P. HILL.

mesially, forms a single loop upon itself, hence it passes over
the right side of the embryo to reach the centre of the allan-
toic placental area (fig. 1, pl. a.), a portion of which is visible
in the figure, just behind the back of the embryo. In fig. 2,
Pl. 1, the embryo has been removed to expose the placental
area. In both uteri the placental area is roughly oval in
shape, as in Stage D, and situated on the mesial side of the
uterus. It is bound by a continuous ridge-like thickening of
the mucosa, so that the area itself appears depressed below
the general level of the inner surface of the uterus. Through
the thin walls of the vesicular portion of the allantois the
irregularly ridged surface of the placental syncytium could
be made out. The inner surface of the mucosa of the rest of
the uterus also presents a ridged appearance.

The placental area of the right uterus measures approxi-
mately 8 mm. in length by 6 mm. in breadth; that of the left
uterus was somewhat larger, measuring 6°5 mm. by 9 mm.
The allantoic stalk has now a length of about 16 mm.,i. e. just
double the length of the stalk in the preceding Stage D, and
it is now also just about double as thick as in that stage.

As in previous stages, the outer or placental surface of the
vesicular part of the allantois is found not to occupy the
entire extent of the original chorionic area, but there is left
outside its margin, i.e. outside the margin of the placental
area, a narrow annular zone of persistent pure chorion, which
surrounds the placental area, and which is attached on the
one side around the margin of that area, and on the other
passes into the vascular omphalopleure, along the line of
junction of the latter with the yolk-sac splanchnopleure
(Pls 2g. -6icke)e

The placental area of the present stage as seen in surface
view is essentially similar to that of Stage D. The allantoic
stalk (Pl. 1, fig. 2, all. s.) is seen to join the inner surface of
the flattened vesicular portion of the allantois near its centre.
In the stalk run the two allantoic arteries and the single vein.
The latter is situated above the two arteries, and is hence not
visible in the figure. At the distal end of the stalk the

EMBRYOLOGY OF THE MARSUPIALIA. ol

vessels branch out over the inner (ccelomic) wall of the
vesicular part of theallantois. The two arteries—one running
forwards to supply the anterior portion of the placental area,
the other passing back to similarly supply its posterior
portion—eventually divide, each into two branches. These
pass outwards, dividing as they go, to the margin of the
allantoic vesicle, round which they and their branches pass
to reach its outer or placental surface, where they break up
into capillaries in the allanto-chorionic mesenchyme.

The allantoic vein is formed by the union of two main
factors (fig. 2, all. v.) which accompany the corresponding
arteries. The main arterial branches are each accompanied
by a corresponding venous trunk, but the smaller arterial
branches may or may not be so accompanied. The vitelline
artery (fig. 2, vit. a.), emerging from under the distal
margin of the umbilical stalk, passes in the yolk-sac
splanchnopleure, at first almost directly backwards, then
curves mesially and slightly forwards to reach the margin of
the chorionic zone, where it passes over into the vascular
omphalopleure. There it at once divides into its two
branches, which, diverging in opposite directions, form the
sinus terminalis (figs. 1 and 2, s. ¢.), the two branches being
united by a delicate anastomosis.

The vascular omphalopleure (figs. 1 and 2, vasc. omph.) is
readily distinguishable macroscopically from the bilaminar
omphalopleure (figs. 1 and 2, bil. omph.) lying outside the
sinus, by its more opaque appearance and yellowish colour.

Owing to the fact that the vitelline artery at once divides
on reaching the vascular omphalopleure, the vascular area
has at this point no existence, but as the two branches of the
artery pass out, they at the same time diverge away from the
margin of the placental area, and the vascular area thus
gradually increases in width until a maximum of 5 mm. is
reached about opposite the point of bifurcation of the
vitelline artery. The vascular area has a maximum diameter
of 12°55 mm. It will be shown later that the extent of the
vascular area of the Perameles embryo of this stage is

6 JAS. P. HILL.

considerably less than that of a Macropod embryo at a
somewhat earlier stage of development. What, however,
especially characterises the vascular area of this stage, as
well as that of my preceding Stage D, is its relatively
extremely poorly developed capillary system. Branches
are, indeed, given off from the sinus into the vascular area,
but these are small and by no means numerous, and ap-
parently undergo very little secondary branching.

I describe below the foetal membranes of an embryo of
Macropus parma, and from that account and the accom-
panying figure (Pl. 2, fig. 9) it will readily be seen that
the branches given off from the sinus terminalis into the
vascular area are not only numerous but richly branched ;
they form a highly developed capillary system, almost entirely
unrepresented in Perameles, in correspondence with the fact
that in Macropus the embryonal nutrition is carried on
solely by means of the yolk-sac vessels of the vascular area,
while in the Perameles embryo of this stage the allantoic
circulation is now playing the dominant part in the nutrition
of the embryo, only an insignificant proportion of the nourish-
ment necessary for the growth of the latter being conveyed
through the yolk-sac vessels. In my previous paper I put
forward the suggestion that probably the entire yolk-sac wall
disappeared before the end of intra-uterine life. The present
stage, however, shows that, at all events up to this period
of development, the entire yolk-sac wall remains intact,
although greatly reduced in functional importance, as shown
by the poor development of its vessels.

The yolk-sac splanchnopleure is supplied with blood by
numerous fine wavy vessels (fig.1, a. v.), which arise directly
from the vitelline artery—especially from its first part—as it
courses over that membrane. In fig. 2 one main branch is
seen passing from under the free margin of the umbilical
stalk. It divides up into numerous small wavy branches
which pass up parallel with the vitelline veins. Behind this
numerous branches arise separately from both sides of the
artery (fig. 2, vit.a.). In the terminal part of the course of

EMBRYOLOGY OF THE MARSUPIALIA. 7

the latter fewer and shorter branches are given off. The
blood from these fine vessels apparently passes over into the
vascular area at the line of junction of the splanchnopleure
with the vascular omphalopleure.

Semon (2) has also described the occurrence of similar fine
branches of the vitelline artery in the two forms examined
by him (44pyprymnus rufescens and Phascolarctus
cinereus), and such also occur in Macropus parma.

The blood from the vascular area is returned by two
vitelline veins (figs. 1 and 2, vit. v.), each of which is formed
by the union of two main factors, shortly after they enter
the yolk-sac splanchnopleure. As in Stage D, the two
vitelline veins run back in the splanchnopleure over the left
side of the head of the embryo (fig. 1), enclosing between
them a narrow triangular area altogether devoid of vessels.
The two veins gradually approximate as they pass back and
eventually run side by side. In this region the amnion is
found connected with the yolk splanchnopleure by a narrow
wedge-shaped band of mesoderm which separates the two
veins (Pl. 1, fig. 5, mes.). This narrow connection is all
that is now left of the much larger pro-amniotic remnant
seen in Stage D. Not only is the area now less in extent,
but the mesoderm has penetrated completely across it. The
ectoderm of the amnion over the remnant is thickened (fig.
5, ect.), the cells being club-shaped in form, with the nucleus
situated in the outer projecting part of the cell. The ento-
derm of the yolk-sac splanchnopleure over the remnant is
likewise thickened, but irregularly (fig. 5, ent.).

As the vitelline veins are traced back towards the umbilical
stalk they gradually become smaller, and at the same time
pass over from the yolk splanchnopleure towards the amnion,
in the now greatly thinned bridge of mesoderm of the pro-
amniotic remnant, which posteriorly becomes continuous with
the thin, attenuated yolk-stalk carrying the vitelline artery.
At the anterior margin of the umbilical stalk the two veins
unite into a single trunk. This runs up in a thin fold of
mesoderm continuous with that of the pro-amniotic remnant,

8 JAS. P. HILI.

and which connects the yolk-stalk with the inner surface of
the tubular umbilical stalk (fig. 4). In the upper part of the
umbilical stalk the vitelline vein becomes considerably
reduced in size, and is a much smaller vessel than the
allantoic vein. In this stage the vitelline vein is very re-
markably reduced as compared with the same vessel in
Stages Cand D. The vitelline artery in the upper part of
the umbilical stalk is also a quite insignificant trunk, about
half the size of one of the allantoic arteries, although its
diameter is considerably greater as it courses over the yolk-
sac splanchnopleure. These facts are sufficient to show that
at this stage the yolk-sac vessels play a quite insignificant
part in the nutrition of the embryo as compared with their
functional importance in Stages C and D.

The bilaminar omphalopleure calls for no special mention
here, beyond the remark that it composes the larger half of
the entire surface of the globular embryonic formation.

StructurRAL DErTaIts.

The following account of the structural features of the
uterus and foetal membranes is made very brief, in view of
the close agreement of this stage with my previous Stage D.
In writing up the present paper I have had, after an interval
of a year, to carefully re-examine many of my old prepara-
tions, and compare them with those of this stage, with the
result that I am able to substantially confirm my previous
account.

I. Urrrus.—The serosa, muscularis, and corium present
essentially the same appearances as in Stage D. The uterine
glands are considerably enlarged, and lined by a low cubical
epithelium ; and very numerous blood-vessels occur in the
much attenuated interglandular connective tissue.

(a) Allantoic Placental Syncytium.—This has the
same average thickness as in Stage D, viz.‘12 mm., and shows
no differences from that stage worthy of remark beyond the
fact that its capillary system is somewhat better developed,

EMBRYOLOGY OF THE MARSUPIALIA. 9

the capillaries being on the whole larger. As in that stage,
owing to the projection of the superficial capillaries, the
syncytial surface presents an. irregularly ridged appearance
(Bly 2s fe a7syn. cs):

(b) Synecytium beyond Allantoic Placental Area.—
The portion in contact with the vascular omphalopleure is
also of the same average thickness as in Stage D, viz. ‘09 mm.
In other respects also the same features are visible. The
superficial capillaries are fairly abundant, but on the whole
very much smaller than those of the placental area, and not
quite so well developed as in Stage D.

The syncytium in contact with the bilaminar omphalopleure
is a thinner and much less regular layer, and less vascular.

II. Feran Mempranes.—(a) Chorionic Ectoderm.—
Over the placental area usually single, much degenerated, and
deeply staining chorionic ectoderm cells are still to be found,
but are not numerous. Of the marginal zone of chorionic
ectoderm, seen persistent in Stage D, only traces now remain,
in the form of isolated and often much altered cells. Occa-
sionally such cells are found forming the transition to the
ectoderm of the zone of pure chorion (PI. 2, fig. 6, ch.) which
exists between the outer margin of the allantois and the
vascular omphalopleure (PI. 2, fig. 6, ch. ect.). The ectoderm
cells of this chorionic zone are usually enlarged close to the
margin of the placental area, but rapidly diminish in size as
they pass outwards.

(b) Allantois and Allantoic Placenta.—tThe allantoic
stalk is more or less rounded in section, and where it lies
enclosed by the umbilical stalk has a diameter of ‘5 mm.
The allantoic canal (fig. 4, all. cl.) is no longer perfectly con-
tinuous, and its entodermal lining is only recognisable in
places. Curiously enough, the allantoic vessels appear to be
smaller than in Stage D, but the difference in size is not so
disproportionate as in the case of the vitelline vessels in the
two stages. As regards the vesicular portion of the allantois
and the allantoic placenta, I have little of importance to add
to the description already given of the same parts in Stage

10 FASS Py WME

D. It may be mentioned that small numbers of maternal
leucocytes occur in the allantoic cavity.

A fairly typical section of the allantoic placental area is
shown in PI. 2, fig. 7, from which it will be seen that, except
perhaps for an increase in size of both foetal and maternal
capillaries, the description already given of the allantoic
placenta in Stage D holds good certainly up to this stage of
gestation, and without doubt also for the whole period of
intra-uterine life, a conclusion already arrived at from the
conditions presented by the post-partum uterus described in
my previous paper.

(c) Vascular Omphalopleure and Yolk-sac Placenta.
—The entodernial cells of the vascular omphalopleure, some of
which were found in Stage D to be undergoing enlargement,
are now found to have all increased in size, and to form a
uniformly much thicker layer than in that stage. ‘The cells
are mostly somewhat cubical in form, with rounded projecting
ends (PI. 2, fig. 8, ent.). Their protoplasm and nuclei stain
deeply. Over the sinus terminalis (fig. 8, s. ¢.) the entoderm
cells are also enlarged and, as in previous stages, club-shaped
in form, with the nucleus situated in the outer projecting
part of the cell.

It seems highly probable that this hypertrophy of the
entodermal cells of the vascular omphalopleure, commencing
as it does about the time the allantoic placenta begins its
functional activity, is to be associated with the functional
retrogression of the yolk-sac placenta, consequent upon the
establishment of the allantoic one. For, whether the ecto-
derm of the vascular omphalopleure be adherent to the
surface of the syncytium or not, the condition of the yolk-sac
vessels shows us that the yolk-sac placenta, if we can any
longer speak of such, is now functionally the mere shadow of
its former self. The ectoderm of the vascular omphalopleure,
though still a comparatively thin layer, is slightly thicker
than in preceding stages, the cell bodies being richer in
protoplasm (Pl. 2, fig. 8.).

(d) Bilaminar Omphalopleure.—The ectoderm of the

EMBRYOLOGY OF THE MARSUPIALIA. 11

bilaminar omphalopleure (Pl. 2, fig. 8, ect.) is just about
double as thick as that of Stage C. The cells are large and
somewhat irregular in shape, with projecting outer ends.
Their protoplasm is considerably vacuolated. In Didelphys,
according to Selenka (3, pp. 137 and 138), the ectodermal cells
of both the vascular and bilaminar omphalopleure undergo
enlargement during the last two days of intra-uterine life.
Selenka regards the enlargement of these cells as associated
with their functional activity in transmitting the secretion of
the uterine glands into the yolk-sac, but here again I am
inclined to look upon the hypertrophy as a sign of degenera-
tion.

The entoderm of the bilaminar omphalopleure is a very
much thinner layer than the ectoderm, and consists of flat-
tened attenuated cells (Pl. 2, fig. 8).

IIT. Genrrat Oraans.—As I have already given elsewhere !
an extended account of the structure of the urogenital organs
and of the main phenomena connected with the act of parturi-
tion, a brief résumé of some of the results of that portion of
my investigation will here suffice.

The female of the present stage proves to have been in
her first pregnancy, as shown by the condition of the genital
organs.

Each uterus passes back and opens into a short blindly
ending canal, the median vaginal cul-de-sac, which is
externally not marked off from the uterus, while internally
the os of the latter is exceedingly ill-defined, a condition
which led me in my previous paper to misinterpret the
vaginal cul-de-sacs as posterior prolongations of the uteri.
The two vaginal cul-de-sacs, separated by a common partition
wall, lie embedded in the connective tissue of the anterior end
of the urogenital strand between the lateral vaginal canals,
here bent slightly outwards. From the anterior ventral end
of each cul-de-sac, just below the opening of the uterus, there
passes forwards in the connective tissue underlying the
posterior portions of the uteri (uterine necks) the anterior

1“ Proc. Linn. Soc, N.S,W.,’ March, 1899,

12 JAS. P. HILL.

forwardly directed portion of the lateral vaginal canal, to
open into the base of the corresponding vaginal caecum.
The latter, functioning as a receptaculum seminis, is simply
an outgrowth of the lateral vaginal canal at the point at
which it bends round to pass posteriorly. Throughout their
entire extent the lateral vaginal canals are embedded in the
tissue of the urogenital strand, which represents nothing else
than the persistent genital cord of the pouch young.

Sections through the urogenital strand of this stage show
that the connective tissue separating the lateral vaginal
canals, in which in uni- or multi-parous females the pseudo-
vaginal passage is found to occur, is quite uniform in
character, and only differs from that of the virgin in being
very vascular.

In females, then, which have not given birth to young,
the two median vaginal cul-de-sacs do not open into each
other, and, as I pointed out before, no trace of a pseudo-
vaginal passage is present. But after parturition has once
been effected, the two median vagine are found to open into
each other posteriorly to form a short common median vagina,
and from this the pseudo-vaginal passage leads away. The
young in Perameles thus reach the exterior by way of a
median passage constituted in front by a short epithelially
lined tube a few millimetres in length—the common
median vagina—and behind bya relatively extremely long
cleft-like space, 3 to 4 cm. in length, entirely destitute of an
epithelial lining—the median pseudo-vaginal passage—
situated in the connective tissue between the lateral vaginal
canals.

In the paper above referred to the phenomena of parturi-
tion are described at length, and the conclusion is arrived at
“that Perameles, in respect to the phenomena connected
with that process, stands in no way alone amongst Marsupials
as an aberrant and specialised type, but, quite on the contrary,
exhibits more primitive features in the mode of birth of the
young than are shown by any other Marsupial hitherto
described as possessing a direct median passage.” In

EMBRYOLOGY OF THE MARSUPIALIA. 18

concluding the description of this stage I may remark that,
since the completion of my previous paper on the placenta-
tion of Perameles, I have discovered that the native cat,
Dasyurus viverrinas, is also provided with a placental
connection of a somewhat complex nature and probably of
. yolk-sac origin, but whether or not there is also present an
allantoic placental connection I am unable to state. My
series of stages is as yet very incomplete, and does not
permit me to enter into details, but it is certain that over
some portions of the inner surface of the uterus there is
present a syncytial layer formed by the fusion of the ectoderm
of the bilaminar omphalopleure with the uterine epithelium,
the nuclei of which form nests, vividly recalling the similar
nuclear nests of the syncytium of Perameles, and this conjoint
layer is vascularised by maternal capillaries. But whereas
in Perameles the syncytium clothing the inner surface of the
uterus is entirely of maternal origin, being derived from the
uterine epithelium, in Dasyurus it is partly of foetal origin
(foetal ectoderm) and partly of maternal origin (uterine
epithelium).

The foetal membranes are left behind in the uterus after
parturition, and, as in Perameles, the foetal and maternal
portions of the placenta are absorbed in situ through the
agency of maternal leucocytes. In other words, the placenta
of Dasyurus, hke that of Perameles, is contra-deciduate in
character. We have, then, in any discussion bearing on the
general question of the significance of the occurrence of an
allantoic placenta in Perameles, to face the fact that a placenta
of the contra-deciduate type has been found to exist in two
distinct genera of Polyprotodont Marsupials, and that the
uterine epithelium in both forms undergoes an essentially
similar transformation into a syncytium vascularised by
maternal capillaries.

14 JAS. P. HILL.

APPENDIX.

Organisation of Embryo, P. obesula.
(Plate 1, fig. 3.)

Measurements.—Greatest length, occiput to rounded
hinder end of body, 12°5 mm. Head length 6°5 mm.

Form of Body.—Head raised, but not so much as in
new-born, and forming an acute angle with the trunk. Pro-
minent snout. Slight neck protuberance. Lips fused late-
rally to form ‘“Saugmund,” the line of junction still
recognisable. Mouth lozenge-shaped. Tongue projects
prominently from mouth, and is grooved dorsally. Hyes
distinct, roughly oval in shape, and not covered by epi-
trichium. Eyelids not yet united. Position of lachrymal
duct recognisable. Position of external ear just recognis-
able, covered by epitrichium. In front of cloacal opening is
a small projecting ‘‘ genital Hocker.”

Limbs.—Much as in new-born, except that the claws are
less developed. Fore-limb flexed at elbow, and palmar sur-
face directed backwards. The first and fifth digits quite
small tubercles; second, third, and fourth provided with
short, blunt, recurved claws; the third digit the largest.
Hind limb paddle-like, with plantar surface directed me-
sially. Digits all indicated, but not free from each other ;
the fourth the largest.

Notochord and Vertebral Column.—Notochord intra-
vertebrally constricted. Marked cartilaginous centra with
transverse processes and neural arches, the latter not yet
united above the spinal cord.

Nervous System.—Marked fissura arcuata along mesial
hemisphere wall. Corpus striatum not yet prominent. Bud-
ding from hypophysis anteriorly, but not very marked.

Kye.—Outer wall of optic cup about half pigmented.
Ovalish lens cavity. Optic stalk solid in its middle portion.
Hyelids not yet united. Eye muscles developing.

EMBRYOLOGY OF THE MARSUPIALIA. 15

Ear.—Semicircular canals formed. Cochlea bent. Periotic
capsule partly pro-cartilage, partly cartilage. External audi-
tory meatus plugged by epidermal cells.

Nose.—Much as in new-born. Choane formed ; turbinal
projections arising, and Jacobson’s organ formed and its
cartilage present. Solid lachrymal ducts, which reach the
nasal epithelium.

Mouth.—Palate formed, and invests glottis posteriorly.
Club-like tooth germs, but no enamel organs. Tongue
grooved and with distinct taste-buds. Submaxillary salivary
glands open into mouth.

Alimentary Canal, etc.—Lateral thyroid Anlagen on
sides of trachea. Thymus Anlagen approximated in their
middle regions, but free posteriorly. Extensive pancreas,
its duct opening into bile-duct. Lungs with numerous simple
alveoli. Cartilaginous rings round trachea. Diaphragm
complete and muscle-fibres developing in it. Intestinal loop
no longer projects at navel.

Heart and Vessels.—Ventricular septum not yet com-
plete. Auricular septum complete and a foramen ovale
present. Sinus venosus still extensive. Truncus aorte
almost completely divided. Left ductus Botalli present.
Single dorsal aorta. Renal portal circulation in connection
with Wolffian bodies. Allantoic circulation greatly pre-
dominates over yolk-sac circulation.

Urogenital System.—Mesonephros of large size. Peri-
toneal funnels of Mullerian ducts present. Commencing
renal tubules. Ureters open into urogenital sinus mesially
to Wolffian ducts. Genital Leisten prominent. Sex?

Skin and Skeleton.—Thin nucleated epitrichial layer
on epidermis. Hair Anlagen well advanced on head. No ossi-
fication in cartilaginous skeleton. Pre-maxillary, maxillary,
and palatine ossifications. Rudimentary clavicle ossified.!

1 This is also present in the 8°75 mm. embryo.of Stage D.

16 JAS. P. HILL.

III. On the Fetal Membranes of Macropus parma.

Tue following account of the foetal membranes of this
small wallaby is based on the examination of a single em-
bryo from the left uterus, for which I am much indebted to
my friend Mr. J. J. Fletcher, M.A., B.Sc.

HISTORICAL.

In 1834, Owen (4) gave an account of the foetal membranes
of an embryo of M. major, 7 lines in greatest length; but
although no allantois was found in this embryo, he stated,
from the presence in young mammary foetuses of “the Kan-
garoo, Phalangista, and Petaurus,” of ‘‘the remains of
a urachus and umbilical vessels,” that ‘‘it would appear that
an allantois and umbilical vessels are developed at a later
period of gestation, but probably not to a greater extent
than to serve as a receptacle of urine” (4, p. 342). The
accuracy of this conclusion he definitely established in 1837,
through the examination of a uterine embryo of M. major,
10 lines in length. He says (5, p. 83), “ Below the neck of
this [vitelline] sac there is extended a second pyriform sac,
about one sixth the size of the vitelline sac, having numerous
ramifications of the umbilical vessels and constituting a
true allantois. This sac was suspended freely from the end
of the umbilical cord ; it had no connection at any part of
its circumference with the chorion, and consequently was
equally free from attachment to the parietes of the uterus in
which the foetus was developed.””!

Between 1837 and 1881 nothing of importance seems to
have been published on the embryogeny of Macropus. In
the latter year Chapman again described (7) the foetal mem-
branes of M. major, “ six eighths of an inch in length from
the mouth to the root of the tail.” His account essentially

1 Owen states that he was anticipated in the description of the allantois of
this embryo by Coste (6), with whom he had examined the foetal membranes.

EMBRYOLOGY OF THE MARSUPIALIA. 17

confirms Owen’s observations, and adds nothing of import-
ance thereto. In 1884, Caldwell (8), in a paper on the
arrangement of the foetal membranes in Marsupials, first
clearly pointed out that the embryo lay in the splanchnoceele,
surrounded by the invaginated upper portion of the yolk-
sac wall. He described the general arrangement of the
foetal membrane in Phascolarctus cinereus, and showed
that the allantois in this form fuses with the discoidal area of
true chorion. He also referred to the membranes of M.
rufficollis, but in such a way as to lead the reader to
suppose that in this form also the allantois fuses with the
chorion.

Semon (2), in 1894, described the foetal membranes of
Phascolarctus cinereus (confirming Caldwell’s discovery
of the fusion of the allantois with the chorion), as well as
Aipyprymnus rufescens. In this latter form he insisted
on the rudimentary character of the allantois and its non-
fusion with the chorion, and expressed the opinion that such
a condition would be found to hold good for the Macropodidee
in general. In 1895 I shortly stated (9) that such was
certainly the state for four species of the genus, viz. M.
parma, M. ruficollis, M. robustus, and M. major.

The present communication deals with M. parma alone.

External Characters of Embryo.

The embryo, at least so far as external characters go,
appears to be in a somewhat earlier stage of development
than the previously described embryo of P. obesula. Un-
fortunately it is not sufficiently well preserved for sectionis-
ing. It hasa greatest length of 10 mm., and a head length
of about 6 mm., and is characterised as follows :—Head bent
almost parallel with trunk. Prominent neck protuberance.
Lips not fused. Hye rounded. Lachrymal groove present.
Rounded external nares. Snout little prominent. Wide
external auditary meatus, with triangular ear-pinna. Fore-
limb not flexed, digits all present, and with claw Anlagen,

VOL, 43, PART 1.—NEW SERIES. B

18 JAS. SEL SBTEL.

palmar surface directed mesially. Hind limb’ paddle-like,
digits not indicated, plantar surface directed mesially.

Fotal Membranes.

The foetal membranes in M. parma have the same general
arrangement as in Aipyprymnus rufescens, as described
by Semon (2, p. 25), i.e. the embryo enclosed in its amnion
lies in the extra-embryonic splanchnoccele surrounded by the
upper part of the yolk-sac—the yolk-sac splanchnopleure—
which is invaginated into the cavity of the latter. The
splanchnoceele is closed externally by a discoidal area of
chorion, round the margin of which the yolk-sac splanchno-
pleure becomes continuous with the vascular omphalopleure.
The allantois is a comparatively small short-stalked vesicle,
which never reaches and fuses with the chorion, but lies per-
manently buried in the splanchnoceele.

The entire globular embryonic formation of this stage of
M. parma has a diameter of 15 mm.

In Plate 2, fig. 9, the cavity of the yolk-sac has been
opened by the removal of the greater part of the bilaminar
omphalopleure, exposing the embryo in its amnion, closely
surrounded by the invaginated yolk splanchnopleure (y. spl.),
together with the inner surface of the vascular area (vase.
omph.).

The discoidal area of chorion, concealed in the figure by
the embryo, is readily distinguishable externally from the
vascular omphalopleure by its more transparent and smoother
appearance. Compared with the extent of the chorionic area
in Perameles and in Phascolarctus, where, according to
Caldwell (8), the chorion has a diameter of 12 mm., the area
is here a small one, measuring in greatest diameter 4°5 mm.

The surface of the vascular area (vascular omphalopleure)
presents a roughened reticulate appearance in correspondence
with the ridged surface of the uterine mucosa. It is distin-
euished from the bilaminar omphalopleure by its denser and
darker appearance, The latter (Plate 2, fig. 9, bal. omph.)

EMBRYOLOGY OF THE MARSUPIALIA. 19

occupies rather less than half the surface of the entire
embryonic formation. Its surface is also irregularly ridged.

The vitelline artery, leaving the yolk-stalk on the left side
of the embryo, courses in the yolk splanchnopleure backwards
over its dorsal surface to reach the junction of the latter
membrane with the vascular omphalopleure (Plate 2, fig. 9,
vit. a.). Here it passes over into the latter, does not at once
divide as in Perameles, but runs on for a distance of about
4mm. before dividing into its two branches, which form the
sinus terminalis (s.¢.). The sinus is completed by a narrow
anastomosis, as in Perameles. It measures in diameter 14
mm. by 12mm. The vascular area has a greatest width of
8 mm. opposite the point of bifurcation of the vitelline artery,
and a least width of 4 mm. at that point. It is thus evident
from these measurements that in mere surface extent the
vascular area of this Macropod embryo very considerably
exceeds that of the Perameles embryo described in the pre-
ceding pages. And not only is the area greater in extent,
but its capillary system is also much more richly developed
than in that form, in correlation with its high functional
importance in the nutrition of the embryo. From the sinus
there pass off into the vascular area numerous branches,!
which divide up into much finer branches to form a rich
capillary system, from which the factors of the vitelline veins
take their origin. The numerous fine long wavy branches of
the vitelline artery which run in the yolk splanchnopleure
are especially well developed (Plate 2, fig. 9, a.v.). Above,
these branches come off directly from the vitelline artery,
while below they arise from an independent branch of
the artery which runs parallel with the same. The blood
circulating in these vessels must, as in Perameles, pass over
into the vascular area at the junction of the yolk splanchno-
pleure with the vascular omphalopleure. After the vitelline
artery has passed over into the vascular omphalopleure, it
still continues to give off small branches from both sides
almost up to its point of bifurcation.

1 In the figure these branches have been represented too short.

20 JAS. P: TWiLh

The vitelline veins (Plate 2, fig. 9, vit. v.) show the usual
relations, and include between them a very large area of
yolk-sac splanchnopleure altogether devoid of vessels. The
anterior vein is formed by the union in the yolk splanchno-
pleure of a larger anterior and a smaller posterior factor,
which pass over from the vascular area. There each is
formed by the union of lesser factors coming from the capil-
lary net of the same. Similarly, the posterior vein is formed
by the union of two factors, a smaller anterior and a much
larger posterior factor, returning the blood from the poste-
rior portion of the vascular area. The anterior vein passes
back in the splanchnopleure over the head of the embryo
behind the eye, while the posterior one passes in transversely
on a level with the snout. The two unite at the yolk-stalk
to form the single vitelline vein.

The allantois is a small, globular, thin-walled vesicle pro-
vided with a very short stalk, and measuring in diameter 5°5
mm. It is situated mainly on the embryo’s right side, lying
between the snout and the rounded hinder end of the body.
In the figure (Plate 2, fig. 9, all.) it is seen through the
yolk splanchnopleure, in contact with which it lies. Its
vessels are poorly developed. As Owen long ago pointed
out for M. major, and as Semon has recently described for
Epyprymuus, so here the allantois is a quite rudimentary
structure which lies remote from the chorionic area, and
never comes into contact, much less fusion, with the same.
Such a specialised condition of the allantois is probably
general for the entire family of the Macropodide. That it
also exists outside the limits of that family we know from
the observations of Osborn (10) and Selenka (8) on Didelphys,
and probably the condition is also general for the family
Phalangeride—it certainly holds for Petaurus sciurens
according to Semon, and from my own observations I can add
for Trichosurus vulpecula. But whether the condition
may turn out to be the general one for Marsupials or not, it
is admitted on all hands to be an essentially modified one,

University or Sypney, N.S.W.;

March 16th, 1899,

10.

EMBRYOLOGY OF THE MARSUPIALIA. 21

List OF PAPERS REFERRED TO.

. Hitt, J. P.—‘*The Placentation of Perameles,’’ ‘Quart. Journ. Mier.

Sci.,’ vol. xl, p. 385.

. Semon, R.—‘‘ Die Embryonalhiillen der Monotremen und Marsupialer,”

‘Zool. Forsch. in Australien u. dem Malayischen Archipel.,’ Bd. ii.

. SELENKA, E.—‘ Studien tiber Entwickelungsgeschichte der Thiere:’ IV

(1 and 2), Das Opossum (Didelphys virginiana), Wiesbaden,
1886.

. Owen, R.—‘‘On the Generation of Marsupiai Animals, ete.,” ‘ Phil.

Trans.,’ 1834.

. Owen, R.—“On the Existence of an Allantois in a Foetal Kangaroo,”

‘Proc. Zool. Soc.,’ pt. v, 1837, p. 82. Cf. also ‘Comp. Anat. of
Vertebr.,’ vol. ii, p. 569; and Todd’s ‘Cyclop. of Anat. and Phys.,’
vol. ili, p. 324, fig. 141.

. Costr, M.—“ Vésicule allantoide observée dans l’ceuf des Kangaroo,”

‘Compt. Rend. Acad. Sci.,’ Paris, tom. v, 1837.

. Cuapman, H. C.—‘‘ On a Foetal Kangaroo and its Membranes,” ‘ Proc.

Acad. Nat. Sci. Philadelphia,’ pt. iii, 1881, p. 468.

. CatpwetL, W. H.—‘On the Arrangement of the Embryonic Mem-

branes in Marsupial Animals,” ‘ Quart. Journ. Mier. Sci.,’ vol. xxiv,
1884.

. Hitt, J. P.—*< Preliminary Note on the Occurrence of a Placental Con-

nection int{Perameles obesula and on the Foetal Membranes of
Certain Macropods,” ‘Proc. Linn. Soc. N.S.W.,’ vol. x (2nd ser.),
pt. iv, 1895.

Ossorn, H. F.—‘‘ Observations upon the Foetal Membranes of the
Opossum and other Marsupials,” ‘Quart. Journ. Mier. Sci.,’ vol. xxiii,
1883. “The Foetal Membranes of the Marsupials: the Yolk-sac
Placenta in Didelphys,” ‘Journ. of Morph.,’ vol. i, 1888.

22 FAS. PL ATLL:

EXPLANATION OF PLATES 1 & 2,

Illustrating Mr. Jas. P. Hill’s paper, “ Contributions to the
Embryology of the Marsupialia” (II and III).

All sections drawn were outlined by means of Zeiss’s camera lucida.

List oF Common REFERENCE LETTERS.

Amn. Amnion. a. v. Branches of vitelline artery on yolk splanchnopleure.
all. a. Allantoic artery. a/. c. Allantoic cavity. dl. cap. Allantoic capil-
lary. all. cl. Allantoic canal. all. ent. Allantoic entoderm. all. mes. Al-
lanto-chorionic mesenchyme. ad. v. Allantoic vein. Jil. omph. Bilaminar
omphalopleure. ch. Chorion. ch. ect. Chorionic ectoderm. ca@. Colom.
ce. w. Coelomic wall of allantois. ect. Ectoderm. ext. Entoderm. ez. syn.
Syncytium beyond allantoic placental area. mes. Mesoderm of pro-amniotic
remnant. pl. a. Allantoic placental area. pl. sya. Syncytium of allantoic
placental area. Som. Somatic mesoderm of chorion. Sp. Space in syncytium
(lymph space ?). s. ¢. Sinus terminalis. syz. ¢. Capillary of syncytium.
wu. s. Umbilical stalk. aé. w. Uterine wall. vase. omph. Vascular omphalo-
pleure. vit. a. Vitelline artery. vit. v. Vitelline vein. y. spl. Yolk-sac
splanchnopleure.

Fie. 1.—Right uterus, P. obesula, with ventral half of its wall removed
and portions of the foetal membranes reflected, to expose the embryo. x
nearly 7.

Fic, 2.—The same, after removal of the embryo, to show the placental
area (gl.a.). “X 63-,

Fic. 3.—Embryo, P. obesula. x 65%.

Fig. 4.—Transverse section through the umbilical stalk. som. Somato-
pleure of body-wall. . x 90.

Fie. 5.—Transverse section through pro-amniotic remnant. x 90.

Fig. 6.—Section through margin of allantoic placental area. x 120.

Fic. 7.—Section through allantoic placental area, showing the relation of
the foetal and maternal capillaries. x 380.

Fig. 8.—Section through the sinus terminalis (s. ¢.), and the adjacent por-
tions of the vascular (vase. omph.) and bilaminar omphalopleure (4c. omph.).
x 150;

Fie. 9.—Uterine embryo of M. parma in its foetal membranes, seen after
removal of the greater portion of the bilaminar omphalopleure. x 73.

STUDIES IN THE RETINA. 23

Studies in the Retina: Rods and Cones in the
Frog and in some other Amphibia.

By

H. M. Bernard, M.A.Cantab.
(From the Biological Laboratories of the Royal College of Science.)

With Plate 3.

Part I.

A CLOSE comparative study of Vertebrate retinas, even
though comprehending less than twenty species, threatens to
be a very prolonged undertaking. It is therefore proposed
to publish an account of certain new anatomical facts which
can be dealt with separately. Such a publication is not
exposed to the same objections as can be legitimately made
against the ordinary “preliminary notice of results.” It
will not, of course, be possible to treat the new facts quite
without reference to the new points of view to which the
researches are tending. It may, indeed, be necessary at the
end to sketch some of these very briefly, trusting that no
long interval will elapse before the evidence on which they
are based can be published.

It is, first of all, a pleasant duty to preface this communi-
cation by acknowledging my debt to my friend Mr. Martin
Woodward, of this College. His great knowledge of zoology,
and especially of modern technical methods, has been
placed most unreservedly and generously at my disposal.
While the pursuance of the work and its responsibility are
mine, any permanent additions to knowledge which may
result from it must be largely credited to him, as the
technical work in connection with these researches has been

24 H. M. BERNARD.

done entirely at the Royal College of Science in the private
laboratory of Mr. Woodward, not only with his permission,
but not infrequently with his active co-operation. Professor
Howes has kindly allowed me to date the paper from the
College.

The cones in the eyes of frogs have hitherto been thought
to end in points not far below the level of the junction of
inner and outer limbs of the rods (see fig. 1, where a rod is
outlined for comparison). This, however, is not the case (see
P]. 3, fig. 2, a, b, d, f, g). The reason for this error, a
spite of all the splendid work which has been done on the
retina, is simple. As is well known, the rods and cones have
a strong tendency to divide at the junctions of inner and
outer limb (i. e. at the * in fig. 1) under the action of all
the ordinary reagents, hence it is hardly surprising that
the exquisitely delicate tips-of the cones fail to survive
their violence. If, however, the fixative used be a sudden
short application of intense heat—five to ten seconds’
immersion in boiling corrosive acetic, the animal having
been kept and killed in the dark—the retinal elements, cones
as well as rods, will, in successful preparations, be found to
remain unbroken from the membrana limitans externa to the
pigment layer.

Here it is necessary to state very distinctly that I am
referring only to the retinas of the frog and of some other
Amphibia. For while it is evident that the cones throughout
the Amphibia are analogous structures, certain differences,
e. g. in the positions of the nuclei, make it unsafe to assume,
without fuller investigation, that the elements called “cones”
are analogous in all Vertebrate eyes. We are dealing here,
therefore, only with the structures which are called “ cones”
in the eyes of the Amphibia, and make no allusion whatever
to the structures called “cones” in the human or other
Vertebrate eyes.

Very superficial examination of the retina of the frog,
even when fixed with any of the ordinary reagents, is suffi-
cient to show that, judging from the basal limbs alone, there

STUDIES IN THE RETINA. 25

are two different kinds of simple cones.!. These as usually
seen are shown in fig. 1. The one is short without a basal
vacuole, and the other about one third longer and with a basal
vacuole, which is always large, and may at times be enormously
distended. It is somewhat remarkable that I have not yet
seen any notice of these differences in previous works ; but the
literature on the subject is so vast that I make no pretence of
having waded through more than a very small portion of it.

The real significance of these differences is, however, better
seen when the distal portions, now described and figured for
the first time, are added to them.

The two types of cone thus revealed are shown in figs.
2 (cf. b, d, f, g, with h,7) and 3 (cf. a, b, c, with d, e, h, i),
and diagrammatised in fig. 4, cy (cf. with cs, cy). Their differ-
ences can best be seen if they are drawn upona scale. Careful
measurements show that each cone may be divided into nearly
equal sections—at least in their proximal halves—as indicated
on the scales in figs. 2 and4. In type cy, fig. 4, the first section
extends from the memb. limitans ext. to the spherical refrac-
tive globule which is characteristic of the cones of the frog.
The second section extends from this globule to a point
where the structure usually breaks in ordinary preparations.
There is generally here a minute vacuole or a sudden thinning
or change in the intensity of the staining. Beyond this it is
doubtful whether any divisions really exist; the fineness of
the thread, and its great delicacy and lability to be violently
affected by reagents, render it impossible to say for certain
whether the appearances can always be relied on. I have
certainly at times seen what appeared to me to be other
divisions (see figs. 2, fand g, and 3,a andc). At the very
tip of the cone there appears to be a terminal vesicle, to
which our attention will presently have to be directed.

In the cones of the second type (fig. 4, c; and ¢,) the first
section can be easily distinguished from the second. It

1 What are known as double cones will be mentioned later, and are not
referred to here.

26 H. M. BERNARD.

invariably has a large basal vacuole, and it is about the same
length as section | in type c,. The small refractive globule
we now find on the level of the second division of c,. The
third section is generally very distinct, being thick and often
deeply stained, but with very delicate walls, usually ill-defined,
doubtless owing to the action of the reagents. From this
point this second type of cone may again be divided into
cones Cc; and c,. In the former the delicate tip alone is
swollen into a vesicle; in the latter the whole of the remain-
ing length swells into a long, terminal, often shrivelled and
generally ruptured vesicle (figs. 2, 7, k, and 8, ¢, d, e, h, “).

Before discussing these varying forms it will be advisable
to examine more closely the measurements which lie at the
basis of the scale shown in the figure. Measurements of the
cone sections reveal a degree of regularity which requires
explanation. In speaking of the measurements of rods and
cones we must be careful to note that they can only be relative.
The rods are not stiff cuticular structures, but long, cylin-
drical sacs filled with certain substances, apparently of
varying consistency, which allow the rods to be squeezed up
or else pulled out or bent about at all angles.

The complete forms of the cones are best seen when the
rods are drawn out and separated by short intervals. The
latter are then about 50 win length, measured from the memb.
limitans ext.t. Of this length, the inner section or limb of the
normal rod measured on an average 10m (fig. 2, e and J),
with variations ranging between 8 and 12m. ‘This leaves
the outer limb of the rod about 40 in length.

We have, then, from the membrana limitans externa to the
pigment layer about 50 4, and across this the cones stretch.
I have shown in the diagram (fig. 4) the results of many
measurements. Passing over c, for the present, we find that
section 1 in c,, which is commonly called the inner limb of

1 This is also the length given by Hoffman (Bronn’s ‘Thierreich,’ vi, part
2, p. 283). I have found rods as much as 60 p» long in well-fixed frogs’
retinas. We shall see later on some reasons for believing that the size of the
rods varies up to some maximum with age.

STUDIES IN THE RETINA. 7

the cone, measures 10, and is, as is well known, of the same
length as the inner limb of the rod. The second section also
measures 10,, with slight variations it is true, yet with a
constancy sufficient to demand explanation. Section 3 at
times also appears to be well marked, but this may be purely
accidental. The same lengths are found for these three basal
sections in the cones ¢; and c,, there being no doubt in these
cases of the existence of section 3. On the other hand, sec-
tions 4 and 5are more than doubtful, and the last 20 u of the
tips of the cones runs without natural divisions to the pigment
in which the most distal portions are always embedded.

Returning now to the forms of these different types of
cone, it 1s obvious that, so far as the three inner sections are
concerned, the cone ©, is deducible from c, by the simple
addition of a section; for cone c; differs from c, in having
the thick basal section, with its large vacuole. Both form
and measurement thus seem to indicate that, so far as the
three basal sections are concerned, cone ¢, is but a further
development of cone ¢,,1. e. a new portion has grown out
beyond the memb. limitans ext., causing section 1 of cone ¢c, to
become section 2 of c;, and section 2 of c, to become section
3 of cs. This is, as we shall presently see, what has actually
taken place.

With regard to the more distal sections the changes are
more complicated. While it is very difficult to get absolute
demonstration of the terminal vesicle in C2, I am quite con-
vinced that such a vesicle exists, Fig. 2, a, shows such a
vesicle with its proximal half clear of pigment; but this
belongs to a cone which I take to be at a still earlier stage
than ©; while fig. 2, d, f, g, shows what appear to be terminal
vesicles covered over, almost in a basket-like fashion, with
pigment granules. The special sticking of these granules to
cones is always very marked, and will be noted again. Max
Schultze long ago called attention to the clinging of the pig-
ment granules to the ‘double cones’ in Fish. More easily
demonstrable, because longer, and therefore more likely to

1 © Archiv mikro. Anat.,’ iii, 1867,

28 H. M. BERNARD.

emerge from the pigment, are the longer terminal vesicles in
cone ¢y. Their walls are mostly torn and crumpled, but they
may nevertheless be at times found complete (figs. 2, 2, k,
and 3, b, e,h). The part most commonly seen is the promi-
nent end of the vesicle, where the stem of the cone suddenly
widens out (fig. 3,c, d). The former of these is on a cone of
type C,, which shows that variations occur in the order of
development.!

From these facts we gather that at the distal ends of the
cones there is a terminal vesicle, which increases in size up to
20 u in length.

While this transformation, which appears to take place at
the distal ends of the cones, differs widely from that seen in
the basal ends, yet it is so far in harmony with it that we have,
proximally, an extrusion of matter into the cone, and, distally,
an apparent accumulation.

The facts so far adduced indicate that the different types of
cones are due to the successive extrusions of matter through
the memb. limitans ext., while the existence of nodes or
sections approximately of the same length suggests some
periodicity in this process. It is true that this periodicity is
not easy to work out in detail; the difficulty lies in the much
greater quantity of material in the basal than in the distal
sections. We may, perhaps, assume that fig. 2, a, or 4, ¢,,
represents the initial extrusion beyond the memb. limitans
ext. of a vesicle containing fluid. This is squeezed up between
the rods, and runs as a thin thread, to swell out only in the
pigment layer. Into this, or added to this, new matter is forced
out by successive discharges, the nodes or breaking points
between the sections registering in the earlier, thinner stages
of the cone the successive discharges. The contents of the

1 Here it is worth noting that H. Miller (‘Z. w. Z.,’ viii, 1857, p. 48),
who had already seen some slight prolongation of the tips of the cones in the
frog, found in human “cones ” an empty prolongation reaching to the pigment
layer. The equality in length of rods and “cones” in the human retina has
recently been definitely affirmed by Borysiekiewitz (‘ Weitere Untersuchungen,
etc.,’ Wien, 1894).

STUDIES IN THE RETINA. 29

large basal section of c, may be the result of many discharges
which now, on account of the much greater thickness of the
whole structure, no longer cause the appearance of nodes.
Be this as it may, there can be little doubt but that the forms
of cone which we have drawn can safely be regarded as
different phases in the construction of the fully developed
cone C, out of matter extruded through the memb. limitans ext.

This important conclusion is quite in keeping with what
is known of the early development of the rods and cones.
They first appear as sac-like protrusions of the retina
which push back the pigment cells. These sacs are very
tightly packed, and may, I find, be more than one deep.
This latter fact points to the existence of successive extru-
sions. Beyond these simple thin-walled protrusions I am not
aware that the further stages in their development have been
accurately followed. The rods and cones are thought to be
merely specialised prolongations of the ‘visual cells,” the
rods being primary and with simple functions, the cones being
secondary specialisations for more important functions.’ The
new facts contained in this paper will not only fill up this gap
in our knowledge of the development of these the most im-
portant of the retinal elements, but in doing so reverse the
judgment as to their relative value, at least in the Amphibia.

For the moment, such simple sac-like protrusions of the
retina beyond the memb. limitans ext., as the admitted start-
ing-point in the formation of rods and cones, are all that we
require ; for we are justified in assuming that this process of
development is also likely to be that of any new rod or cone
elements which the retina will require in the course of its
growth. New elements, therefore, will be formed by the
thrusting down, between those already existing, of bag-like
protrusions whenever and wherever there is room for them.
The shape of the retina makes it clear that growth could not
take place only at the rim; it must be fairly evenly spread
over the whole extent of the cup, in order that that shape
may be preserved. Now it is obvious that if once a compact

1 Max Schultze, ‘ Archiv mikro. Anat.,’ ili, 1867, p. 238.

30 H. M. BERNARD.

layer of cylindrical bags was formed, new ones endeavouring
to force their way out between them would have to be wedge-
shaped or conical in order to succeed. This would especially
be the case with any sac-like body forcing its way out between
a compact mass of amphibian rods; its shape would necessarily
be conical, the basal portion, between the inner limbs of
the existing rods, which (inner limbs) are certainly softer
than the outer, could here be swollen or bag-like ; while
between the outer limbs of the rods, which there is every
reason to believe are, at least compared with the inner limbs,
turgid and firm, the new protrusion would have to be tapering
and thread-like, and only able to swell again as a vesicle
when it projected beyond the tips of the rods—that is, in the
pigment layer.

If this line of reasoning is correct, it leads us to conclude
that the cones, at least in the eyes of the Amphibia, are not
the important fixed morphological elements which all the
earlier investigators declared them to be, but merely stages in
the formation of new rods. Daring as the conclusion may at
first sight appear, there is nothing very improbable in it. If
new rods are required, as they must be as the retina grows,
they would certainly be formed as they are in the earlier
development of the eye, viz. as protrusions from the retina.
Such protrusions, foreed down between the existing rods,
would, as far as we can see, necessarily be conical. We
know of no other conical protrusions but those usually called
cones, and hitherto regarded as fixed elements with special
functions. Hence these cones must themselves be the stages
in the development of fresh rods which the argument requires.
Turning to our figures and diagrams, we find this line of rea-
soning fully confirmed, for qualitative and quantitative com-
parison of the different forms of the cones themselves shows
clearly enough that they are different stages in the protrusion
of matter beyond the limiting membrane. In this connection,
too, we can best call attention not only to the large vacuole
in the basal section of c,, a vacuole sometimes enormously
distended, but also to the small vacuoles (omitting the

STUDIES IN THE RETINA. 31

spherical refractive body) which are scattered along the thin
cone. In fig. 3, a,a very large one appears. These vacuoles
are all suggestive of fluid travelling outward along these
cones, and helping to swell the terminal vesicle, or, again,
they may be the remains of fluid left in the element after its
collapse under the action of the reagent, if such a collapse
takes place. (On this see below, p. 42, and fig. 12, a, the
second element on the left.)

On turning now to the rods, to ascertain whether they
afford any evidence of their early developmental stages
having been cones, our attention is at once fixed upon those
with very long inner limbs, which we will call, after their
discoverer, Schwalbe’s rods. On measuring these I found
that they were roughly divisible into two kinds, the one with
the inner limbs measuring about 30, and the outer limbs
20 4; the other with inner limbs measuring 20 p, and outer
limbs 30 ;! while, lastly, the inner limb of the normal rod
measures 10, and the outer limb 40 u. These are shown on
the scale, fig. 4, 7, 7, 73. It was obvious that there must be
some kind of connection between these different kinds of
rods and the developing cones, owing to this general agree-
ment in the measurements, but it was some time before I
could see any satisfactory explanation of the phenomenon.
On arranging the rods side by side with the cones, in the
way shown in the diagram (fig. 4), not only does the scale
formed by the sections of the latter serve also to measure the
different kinds of rods, but also throws light on the develop-
mental process. Three divisions of the cone measure the
longest inner limb, two divisions the next, while the inner
limbs of the cone c, and fully formed rod are already known
to agree in length. Turning to the outer limbs, we find the
shortest agrees in length with the long terminal vesicle dis-
covered at the tip of the most developed cone, viz. 20. The
next measures 30 , and that of the fully formed rod 40 p.
We may also note that the shortest outer limb is very fre-

1 Hoffman (I. c.) gives the measurements of the outer limbs as from
20 to 25 p, which agrees closely enough with my own.

ae H. M. BERNARD.

quently much thinner than that of the fully formed rod;
several measurements gave from 4 to 5 for the outer limbs
of Schwalbe’s rods, and 6 to 7 w for those of normal rods.
On the other hand, they may be found of the same thickness.
I note in some microphotographs which I have had made
of the rods and cones of the Frog, in one case a Schwalbe’s
rod is about two thirds as thick, while in another there occurs
one nearly if not quite as thick as the fully developed rods
near it.

We have, then, in the diagram a series of structures con-
nected together by a scale of measurements. What evidence
is there that this series is really developmental? We have
already found strong reasons for believing that the three-cone
stages are mere phases in the development of new rods; the
retina, therefore, should show us stages between the last cone
with its long terminal vesicle and the fully formed rod. The
only variations on the normal rod which we can find are
those with the long inner limbs (Schwalbe’s rods). There
can, I think, be no reasonable doubt that these are the inter-
mediate stages we require. The outer limb of the (pre-
sumably) youngest rod stage is of the same average length
as the terminal vesicle of the oldest cone stage, viz. 20 u, and
further, it has apparently but continued the line of develop-
ment by becoming filled up and distended. On examining
the change of shape which has taken place, the most striking
change between this rod (7,) and cone (c,) 1s that the matter
which was formerly in the basal sections of the cone has
moved outward to form a swelling in contact with, but in
some way separated from, the terminal vesicle or outer limb,
although it may be important to note that the separation
between inner and outer limb does not seem to be in this
stage nearly so sharp as it is in the later normal rod. The
next step (7) is a further filling up of the outer limb and its
extension through the length of 10; at the same time the
inner limb, as it were, is drawn back and shortened to 20 u.
The last step is the extension of the outer limb to its full
length, about 40 », and the corresponding shortening of the

STUDIES IN THR RETINA. 33

inner limb to its normal length of 10”. Here I should again
like to emphasise the fact that although I use these exact
figures, they are only approximate; lengths of outer limbs
between these occur, but the numbers given occur with
sufficient frequency to convince one that there is some under-
lying law which has to be discovered. After adopting and
abandoning several possible explanations, I am inclined to
regard this curious fitting of the successive stages in the
development of the rods into the scale made by sections of
the cones as due to the varying degrees of lateral pressure
exerted by these latter. This pressure will be greatest in
the zone of the innermost cone section and less in that of the
next, and soon. This explanation was suggested to me by
noting the similarity between the inner limbs of Schwalbe’s
rods and the conditions invariably presented by one of the
two cones in every pair of ‘double cones.” I give several
drawings (fig. 5, a—f) of these so-called double cones as seen
in the retina of the frog, about which so much has been
written. | Of these figures only a shows the full length of the
cones; the rest, being from sections prepared by other fix-
tures than heat, have lost their tips. I can myself find little
more in them than that two cones develop side by side, and
one of them is generally somewhat distorted by the pressure
of the other, the pressure being exerted in many cases by the
large basal vacuole. The peculiar appearance of the “ twin
cones” (at least in the frog) is thus of the nature of an acci-
dent, and a very simple accident. Whichever cone first
develops its basal vacuole squeezes all the material out of
the basal section of its companion into its distal end, as is
shown in the figures. If the inner limbs of the left-hand
cones in a and f, or of the right-hand cones of 6 and ¢, are
compared with the inner limbs of Schwalbe’s rods (fig. 2, ¢
and J), we see that pressure could easily account for the shape
of the latter.! It seems, then, that if the cone at stage c, in

1 These long-limbed cones which always form one of the ‘‘ double cones”
are the only elements I can find at all corresponding with the long-limbed

VoL. 43, PART 1.—NEW SERIES. c

34 H. M. BERNARD.

the diagram, fig. 4, became as it were passive, i.e. ceased to
distend its basal section by any further extrusion of matter,
the lateral pressure of the basal sections of younger and still
actively growing cones could hardly fail to force out distally
the material from the basal portions of its inner limb. We
thus have, on the one hand, zones of pressure due to the dif-
ferent thicknesses of the sections of the cones, while, on the
other, we have the outer limbs of the developing rods dis-
tending and lengthening in a direction opposite to that in
which the cones are forcing their way. It seems but natural
that the lengths of the growing outer limbs would be found
to have some correspondence with the different zones of
lateral pressure through which they have to force a passage.
It will be remembered that we have already assumed the
existence of this lateral pressure as necessary to account for
the shape of the cones themselves. The rods form a compact
layer into which fresh elements as conical wedges force their
way, their continued intrusion keeping the layer permanently
compact. In spite of the frequent spaces which appear in
microscopic sections between the rods, the evidence from
the best preserved material leaves little doubt but that, in
life, these retinal elements are packed together as tightly
as the intruding cones can wedge them. Many of the clear
spaces are due to rods falling out of the sections, others
perhaps to shrinkage, others again to the presence of large
vesicles filled with fluid, the walls of which are so delicate
as to be very seldom preserved (see below, p. 42, and fig. 16).
Our comparison of the rods and cones in the retina of the
adult frog has brought us to the conclusion that the latter, in
the frog’s eyes at least, are not elements with any special
sensory function, as was maintained by the earlier investi-
gators, but that they are simply stages in the development of
fresh rods; and that, in addition to their potential value as
future rods, they serve, even in their earliest stages, to keep
the layer of the rods compact.
cones shown in van Genderen Stort’s figure reproduced in ‘ Quain’s Anatomy,’
10th edit., iii, part ili, p. 48, 1894.

STUDIES IN THE RETINA. 35

We have so far confined our attention solely to the adult
frog, and the argument thus limited has been somewhat
complicated. This, however, is the order in which the
work was carried out and the results obtained. It may,
perhaps, be remembered that the relations of the rods and
cones was not the initial object of these researches, which
were undertaken to extend and elaborate the evidence I had
collected in confirmation of the theory of vision I published
in 1896.1 We shall now turn to other Amphibia, and espe-
cially to young forms in different stages of development,
where perhaps we ought to have begun, and show that they
fully confirm the conclusions above arrived at, and generally
in a much simpler and more decisive manner.

The Toad.—I have not found any traces of sections or
nodes in the tips of the conesin the toad. Their continuations
have more the appearance of shrunken sacs (fig. 6). The
refractive globule so characteristic of the cones in the frog is
absent here, but is perhaps compensated for by the immense
size of the “ellipsoid,” which in the fully developed rod may
attain a length of 10 w with a breadth of 6u. It is very con-
spicuous in cone ¢, (see fig. 7), but becomes somewhat in-
distinct in cones c, and c,. In cones at this stage it some-
times appears as if there were two, somewhat ill-defined.
These finer details, and indeed the ellipsoid itself, require
special investigation, and we shall return to them again in the
second part of this paper.

As in the case of the frog I suggest that cone c, (fig. 7)
passes into the rod 7, by the filling up of the terminal sac,
and the squeezing outwards of the ellipsoid and other matter
in the basal part of cone c,. Again, also, the aspect of the
double cones, fig. 6, d, h, shows that the action of pressure
might well account for the long thin inner limb of rod 1 ;
while, lastly, fig. 6, 7, shows how great the lateral pressure
within the proximal zone of the layer, brought about by the
intrusion of young cones, must be. Here we see the inner

1 Ann, and Mag. Nat. Hist.,’ 6, xvii, p. 162,

36 H. M. BERNARD.

limbs of the rods quite distorted by the intrusion of a cone,
the base of which is swollen into a large clear vesicle. Such
figures as these might be multiplied indefinitely, and in each
case with some slight but instructive variation in detail.

In the toad I have found outer limbs of rods, in stage r,,
not much more than 3 win thickness, and in striking contrast
to the thick outer limbs of the fully developed rod.

Urodeles.—The conical shape attributed to the rods
of the Triton by Max Schultze led him to believe that,
in the eyes of gilled forms, still more conical and probably
transition forms between rods and cones would be dis-
covered. In Triton he found the conditions such that if
the rods had been only a little thinner and the cones a
little thicker, the two would pass into one another.! He
would not at all accept Steinlin’s suggestion that, in general,
the two structures hardly admitted of sharp distinction.’
Admitting their common origin, transition forms were, he
thought, rare, and the rods were certainly the primary
simpler structures, out of which the cones were developed
later as more highly specialised organs.

My own observations have led me (perhaps erroneously) to
lay no great stress upon the slightly conical shape sometimes
noticed in the thick rods of Urodeles.? The undoubted tran-
sitional stages which can be found between the rods and
cones speak for themselves, whether this very slight form-
feature has any value or not. Numerous as they are, earlier
investigators were not prepared to see them, and missed
them accordingly. For example, diagram fig. 8 shows a series
of elements chosen from a few sections through the retina
of an adult axolotl. They might be multiplied manifold.
They have been arranged according to the lengths of the
different parts. At a glance they can be seen to form a
developmental series. We thus see that longitudinal measure-

1“ Archiv f. mikro. Anat.,’ Bd. iii, 1867, p. 238.

? Tbid., Bd. iv, 1868, pp. 10 and 22.

* In microscopic sections it may be due to the plane of the section not
passing strictly longitudinally through the thick rod,

STUDIES IN THE RETINA. 5)

ments of the parts of the elements give us an entirely differ-
ent kind of transition form from that which the earlier
workers looked for. But, as we shall see below, in young eyes
transition forms more like the kind expected do occur in
great numbers (fig. 12, c).

I have not succeeded in ascertaining whether or not the
tip of the cone shown in the earliest stage (fig. 8, a) is the
true tip. The aspect of b certainly suggests that the tips
break off, and when we find the cone not only in the Anura,
but also in the salamander (see below), running straight
down to the pigment layer, it is fairly certain that the same
is the case here. The cone “‘ grows” by the enormous deve-
lopment of the basal vacuole, which forces out the ellipsoid
(which was here densely stained) with the conical mass
distal to it; c shows a double cone; d, e, f show different
lengths of the vacuole and enlargements of the tip; from f
the outer limb of the rod grows and forces back the ellipsoid,
which changes its shape. Some of these developing outer
limbs (from g) seemed to be thrust much deeper than others
into the pigment cells, at times almost displacing the latter
—an appearance very suggestive of their active growth in
length.

The narrowing of the vacuole from ¢ to d, e, f is not in-
variable. It is probably purely accidental that those with
compressed vacuoles were most numerous in the sections. In
such a confused mass of elements forcing their way out, and
mutually squeezing one another, naturally many different forms
will be assumed by individuals. Further, these long narrow
vacuoles would be likely to be less injured in section-cutting
than those most swollen, and would occur more frequently in
the preparations. The inner limbs of rods g and h are also
probably chance forms.

It will now be understood from the series why I do not
think that there is much value in the conical shape of the
rod. In the swelling of the outer limbs seen in e and f, to
the size shown in J, it seems hardly likely that the conical
shape would be preserved, especially if the outer limbs of the

38 H. M. BERNARD.

cones originally ended in terminal vesicles, which, as above
stated, I feel sure must be the case.

If the tips of the cones run as they do in the Anura, from
the first as far as the pigment cells, we should have here
essentially the same condition as we have above described for
the toads. One striking difference, however, has to be noted.
The basal vacuole in the adult Anura never swells to the
enormous size seen in the axolotl. It is true it may be very
much larger than is shown in fig. 7 (see e.g. fig. 6, d), but
only in immature eyes (fig. 13) does it somewhat resemble
those in fig. 8, c, g.

Salamander.—As in the frog and the toad, the cones
here can be shown by heat fixation to reach to the pigment
layer (fig. 9, a—d). On reaching this layer, it is seen that
the pigment is raised as if round some terminal expan-
sion of the cone (see p. 27). Again, fig. 10 shows what I
take to be this expansion, although it may possibly be the
shaved-off tip of arod. If my interpretation in this case is
correct, it is interesting because the specimen was fixed in
Perrenyi’s fluid. And here I may add that though the com-
plete forms of the cones were first clearly seen in prepara-
tions fixed by heat—by which method they can always be
seen,—since knowing they are there I have recognised many
traces of them in sections prepared with other fixatives.

The figures show the only transitional series which I have
been able to find. I have not been quite so successful in
making satisfactory preparations of the retinas of either
salamanders or newts. This has been a disappointment which
I hope to overcome by renewed attempts. I may say, how-
ever, that what sections I have of adult salamanders, and of
Molge cristus and M. vulgaris, though not good enough
to show clearly and unmistakably the different stages side by
side, are yet quite sufficient to show that what one sees in the
eyes of the axolotl will, in all essentials, be found in these eyes
also. From the few figures given (b—d, fig. 9) it will be seen
that the basal vacuoles are much smaller than in the axolotl,
and more nearly the size seen in the cones of the Anura.

STUDIES IN THE RETINA. 39

Young Forms.—Of these I have examined different
stages in the development of frogs, toads, and salamanders.
All confirm very strongly the conclusions we have come to
above, that the cones in the Amphibia are merely stages in
the development of the rods.

In eyes under 0°5 mm. in diameter the conditions fre-
quently require special study, and will be briefly referred to
below. We will confine our attention for the present to
eyes over 1 mm. in diameter, in which the definitive conditions
are becoming apparent. In such eyes we are at once struck
by the immense numbers of cones in all stages of protrusion,
far more in comparison with the number of the rods than in
the adult eye, in which the proportions are reversed. Fig. 11
is that of a young salamander (1°6 mm. eye diameter). Fig.
12, A, B, c, are from a toad tadpole (1:12 mm. eye diameter).

Another phenomenon of these young eyes is the great
number of long, vacuolated inner limbs of the rods, the
outer limbs of which are short, and too often obscured by
pigment. This condition is not to be confused with that
which will presently be noted as being common to eyes under
0-5 mm. in diameter, which it may superficially resemble ;
for these long, apparently empty inner limbs are sometimes
so numerous that it is difficult, in sections, to make out the
connections at all. Fig. 13 shows the appearance referred to
in atoad tadpole (ca. 1°5 mm. eye diameter). Fig. 14 is from
a young salamander (1°6 mm. eye diameter). The elements
drawn are some way from the centre of the eye, where the
vacuoles were much longer and narrower, but hardly any
section cut them longitudinally, and the result was too con-
fused to draw. Reference to the diagram (fig. 8) will fully
account for these long inner limbs, which are not character-
istic of adult eyes, although existing in small numbers.
Those shown in the diagram (fig. 8), for instance, were found
in about three thin sections of the retina of an adult axolotl.
We see from this diagram that any large number of cones
must naturally mean a correspondingly large number of
immature rods, with long vacuolar inner limbs.

4,0 H. M. BERNARD.

A still more beautiful confirmation of our conclusions is
afforded by the fact that, in young eyes, the oldest and
thickest rods and those with longest outer limbs occur in
the centre of the retina, and as we work away towards the
periphery the rods get thinner and thinner, until it requires
close attention to decide whether the element is in the cone
or in the rod stage. It seems to me possible to speak of
such stages, the rod stage being when the outer limb has
begun to grow towards the retina. In fig. 12, a and B are
from the centre of the retina, ¢ nearer the periphery, but not
so far from the centre that the length of the elements has
perceptibly decreased. The rods in a and B were about
6 uw thick, in c the thickest was only 3 mw. Here the
earlier investigators could have found the transition stages
they were looking for in immense numbers had they looked
for them.

It seems to me, then, that we can clearly regard the longer
and thicker rods found in the centres of young retinas as
the ‘ oldest,’ for we know that all these elements are grow-
ing. The rod layer is almost crescentic in shape in very
young eyes, and at its thickest it is much thinner than in the
adult. In the advanced toad tadpole (with four legs, and
with the diameter of eye 1:12 mm., some of whose retinal
elements are shown in fig. 12) the thickness of the rod layer
in the centre of the retina was only 34—36 pu. In the
adult it is at least 50 u. Again, the thickest rod I could
find in this young eye was 6 yw, thinning away to 3 p, while
I have measured rods in adult toads as much as 9 mu thick.

I have noted also that rods may be thicker in the centre
of the eyes of adult frogs than towards the periphery.
Rods 8 » thick were common in the middle of a retina,
while 5—6 » was the usual thickness at the sides. If the
thickest were the oldest, this would be intelligible.

The transitional series between cones and rods based upon
the longitudinal measurements yielded by these young eyes
are very simple. As can be seen from fig. 15, which, as might
be gathered from the presence of the refractive globule,

STUDIES IN THE RETINA. 41

refers to a frog tadpole, they resemble in all essentials the
series seen in the adult axolotl. In c four cones are crowded
together, the cones here, again, being far more numerous
than the rods. In this eye I found absolute proof of the
truth of my main conclusion, that the cones turn into rods,
for the vestiges of the refractive oil globule characteristic of
the cones were to be occasionally seen in various stages of
evanescence in the ellipsoids of the rods (see fig. 15).

In now referring to the conditions seen in eyes under
5 mm., I should like to say that my examination of them has
not been as thorough as the difficulty of unravelling them
demands. The conditions vary ; in some eyes the definitive
elements have already begun to appear, in others one is
forced to the conclusion that the extrusions from the retina
are largely a confused mass of immense vacuoles, which
force back the pigmented layer. If any order exists among
these extruded sacs it is extremely difficult to unravel; the
nearest approaches to anything like normal rods or cones are
long, tapering structures which take deep stains, and as to
which I am still quite uncertain whether they are the tips of
fresh extrusions forcing their way between the existing sacs,
or merely streaks of staining matter on the walls of the same.
What is clear is that the rods and cones, such as they are
seen in the adult, or even in eyes over 1 mm. in diameter, may
not be visible; and yet there can be little doubt that out of
these large sacs the future retinal elements will be developed.
It is interesting further to note that the pigment granules
which climb up between these sacs do not seem to be able to
retreat back again to the pigment layer, as is the case in
eyes with definitive rods and cones if kept in the dark before
fixation. The clinging of pigment to the young cones, 1. e. to
the raw material of the rods, has been already noted (see p. 27).

From this stage, in which the retinal elements are largely
undifferentiated sacs, filled apparently simply with fluid, the
eye passes only gradually. The process has still to be worked
out in detail. We will here pass on to note that in much
older eyes, after normal rods and cones have appeared, we

42 H. M. BERNARD.

may find the latter frequently separated by what appear to be
long vacuoles, which cannot yet be called cones, but which I
take to be a lingering of the earlier undifferentiated condi-
tion. Fig. 16 (from an eye ‘75 mm. diameter) shows the
appearances ; the sacs can there be traced to definite nuclei
which occupy the position of the nuclei of very young cones
(see below on the positions of the nuclei). Such long open
sacs as these can only be regarded as the last remains of the
condition just described for still younger eyes. In fig. 12, a,
which is from an eye 1:12 mm. in diameter, a collapsed sac
can be seen, which shows that at any time in a rapidly grow-
ing eye the embryonic sac-like extension may reappear. As
soon as the rods and cones are multiplied sufficiently to form
a compact layer, each new vacuole forcing its way down can
presumably only appear in the form shown in fig. 4, ¢,, with
a slight proximal and a larger distal swelling, the intervening
portion being squeezed to a thread.

I had hoped to give, as a second part of this paper, an
account of what I have been able to unravel of the details of
this process of transformation from the early sac stage to the
definitive rod stage, and also of the minute structure of the
rods themselves; but other duties have intervened, and the
completion of the second part must be postponed for a few
months.

T will, however, here append one more argument in favour
of my conclusion that, in the Amphibia, cones are merely
stages in the formation of new rods. It is derived from a
comparison of the positions of the nuclei.

The nuclei of fully developed rods are invariably found in
various degrees of protrusion beyond the memb. limitans ext.
This protrusion is usually very pronounced in the Urodeles
and in the toads, but less so in the frog. In younger rods,
Schwalbe’s rods, the nuclei seldom if ever project beyond
this line, while the cone nuclei are still further away and
nearer to the outer reticular layer the younger they are.!

' This is not so rigidly the case in young eyes, in which the multiplication
of elements is very rapid.

STUDTES IN THE RETINA. 43

We thus have not only new elements (cones) forcing their
way down between the rods, but the cone nuclei forcing their
way to and through the memb. limitans ext., to become rod
nuclei. The question then arises, how is the supply kept up?
For in growing retinas it is obvious that a great multiplica-
tion of the wuclei of the outer nuclear layer must be provided
for. I have never seen any karyokinetic divisions in any
retina in parts where rods and cones have begun to form.
They can be seen all over the retina just within the memb.
limitans ext. in embryos before any sacs have been protruded ;
but after the centre of the eye has become functional, and
rods have appeared, the karyokinetic divisions are confined
to the rim of the retina where the embryonic simplicity
persists. ‘The immense number of fresh nuclei required by
the outer nuclear layer is not, therefore, supplied by the
division of those already present, most, if not all of which
would be actively functioning, and thus quite incapable of
mitotic division. The answer to the question of their origin
is, however, easily solved ; a survey of retinas of any extent
reveals a steady migration of nuclei outwards from layer to
layer, but especially from the middle nuclear to the outer
nuclear layers. As I propose to give the evidence for this
in extenso in a separate paper, I will confine myself here
to saying that the nuclei which have been already frequently
seen in the outer reticular layer (cf. fig. 5, e and f), and have
been invariably regarded as belonging to that layer, are, in
reality, nuclei travelling through it from the middle nuclear
layer outward. I have been entirely unable to confirm the
existence of Krause’s “membrana fenestrata,” nor the later
view of Schieferdecker! that this outer reticular layer is at
least primarily sustentacular, with a specialised nucleated
tissue. I have studied these nuclei with great care and for
many months, and while it is not always possible to say that
they are migrating, this is so frequently the case that I am
disposed to assume it to be so universally. The evidence for
this conclusion is so overwhelming that it has frequently
1 © Archiv f. mikro. Anat.,’ xxvill, 1886, p. 305.

44, H. M. BERNARD.

astonished me that it has not been noticed before. The only
observer who, so far as I can make out, has called attention
to the phenomenon is Borysiekiewitz (I. c.), who notes, evi-
dently with astonishment, two evidences of transmigration
(“‘ Ortswechsel”’) of nuclei which he has seen in the human
retina. He notes that nuclei may wander outward (1) from the
outer nuclear layer into the basal limbs of the cones, and (2)
from the middle nuclear layer into the outer nuclear layer
through the outer reticular layer. In this latter case it was
the characters of the migrated nuclei, exactly like those of
the layer they had left, and not at all like those into which
they had moved, which convinced him that migration must
have taken place. Leaving the subject for the present, it is
obvious that such migration of nuclei outwards from the
middle nuclear layer would account—(1) for the enormous
increase of nuclei needed for the formation of new rods in
the growing retina; (2) for the evident movement of cone
nuclei outwards to become rod nuclei.

All students of the retina will expect here some reference
to Landolt’s “ Kolben;” and rightly, for it must occur to
every one that we have here a possible explanation of these
structures. This, indeed, has, I believe, already been sug-
gested by Krause; but I have failed to find again the exact
passage in which he speaks of the “Kolben” as most pro-
bably supplementary elements. I have not, however, been
very fortunate in discovering these bodies, although not for
want of looking. ‘he structures which I have seen have not
resembled those figured either by Landolt! or by Dogiel.? I
therefore prefer to confine myself here to saying that the
structures I have seen, if they are what Landolt referred to,
fully bear out Krause’s suggestion—i. e. that the outermost
nuclei of the middle layer, even before they leave that layer
to join the definite rod and cone nuclear layer, send radially

1 Arch. mik. Anat.,’ vii, 1871, p. 81.

* Tbid., xxiv, 1885, p.451. See this paper for other interpretations of these
bodies. The author quotes Kuhnt as regarding them as transition forms
between rods and cones.

STUDIES IN THE RETINA. 45

outwards their sac-like processes, which are destined to
become new rods. These, therefore, would represent a still
earlier stage in the development of new rods even than that
shown in fig. 4, c,. They might almost be called intra-retinal
stages.

Returning now to the positions of the cone nuclei in the
Amphibia, if we compare them with those of the “cone”
nuclei in Mammalia, we see at once that the cones in the
Amphibia cannot, at least off-hand, be regarded as the mor-
phological equivalents of the cones in the mammals, or even
of the giant cones in the eyes of the cod. In both these the
cone nucleus has, if anything, a more advanced position near
(or even protruding through) the memb. limitans ext. than
the nuclei of the rods, which is the very reverse of what we
find in the Amphibia. Whether, again, the cones of the
human eye are the morphological equivalents of the giant
cones of the eyes of the cod is a further problem, which I
shall endeavour to decide in another paper. I shall not be
surprised if these, and, indeed, not a few other retinal
elements which have hitherto been regarded as special struc-
tures of definite morphological value, turn out to be passing
form-phases due to functional activities. Indeed, much of
the diversity which occurs in the records of past observations,
a diversity which is usually attributed by each observer to the
defective preservation of the material used by his less fortu-
nate or skilful colleagues, will prove ultimately to be due to
the fact that different physiological conditions are accompanied
by striking variations in the appearances of the tissues con-
cerned.

The one point which we have here endeavoured to establish
is that in the Amphibia the “cones,” which have always
been regarded as highly specialised structures with definite
sensory functions, superior even to those of the rods, are not
definitive structures at all, but simply developmental stages
in the production of new rods.

46 H. M. BERNARD.

EXPLANATION OF PLATE 3,

Illustrating Mr. H. M. Bernard’s “Studies in the Retina:
Rods and Cones in the Frog and in some other

Amphibia.”

Frog.—F ie. 1.—The cones of the frog as usually seen, with true tips
broken off. The asterisk marks the junctions of inner and outer limbs, where
the elements often further divide under the action of reagents.

Fic. 2.—Selection of elements from the retina of the adult frog which have
been measured, and arranged on a scale graduated in sections of 10 p.

Fic. 3.—Further selection from the same, the parts not measured.

Fic. 4.—A series of elements arranged according to the lengths of the parts,

‘showing how the cones may be developmental series in the formation of new
rods.

Fic. 5.—A selection of “ double cones ”’ froma the retina of the frog ; a alone
has the tips preserved (see text).

Toad.—Fic. 6.—A selection of elements from the retina of the adult toad.
The large size of the ellipsoid is shown; d is a double cone; 2% is also a
double cone without basal vacuole in the younger of the two, i.e. in the one
on the left.

Fic. 7.—Selection of same arranged on a scale corresponding with Fig. 4 of
the frog.

Axolot].—Fic. 8.—Series of elements from retina of adult axolotl, to
show how the cones pass into rods; ¢ shows a “ double cone.”

Salamander.—Fic. 9.—A few elements from the retina of the sala-
mander.

Fre. 10.—A cone between two rods of an adult salamander. The cone has
what appears to be a terminal vesicle (cf. Fig. 2, a, d,f, g, and Fig. 9, @ and 6).

Fie. 11.—A few elements from retina of young salamander (eye diameter
1:6 mm.), showing three cones at different stages of development, forcing
their way down between two rods. The rest of space was probably occupied
by one or more of the earlier sac-like elements. Cf. Fig. 16.

Toad, Young.—Fic. 12.—a and 8. Elements from near the centre of
the retina of a toad tadpole. c. Slightly nearer the periphery. 3. Shows the

STUDIES IN THE RETINA. 47

great preponderance of cones in young eyes. c. Shows that the transition
forms between rods and cones not based upon longitudinal measurements are
common in young eyes (see text).

Fic. 13.—From a young toad. Showing the long vacuolated inner limbs
and short outer limbs of the rods indicative of immaturity. See Fig. 8, g, A, 2.

Salamander, Young.—Fic. 14.—From a young salamander, near the
periphery, to show the vacuolated inner limbs and the transitional forms.

Frog Tadpoles.—Fice. 15.—A series of elements from a very young frog
tadpole. Here the fact that the remains of the refractive oil globule can be
frequently seen in the ellipsoids of the rods proves beyond question that the
cones turn into rods.

Fic. 16.—From retina of frog tadpole, showing two large sacs connected
with nuclei, and filling up the spaces between rods and cones (ef. the col-
lapsed sac in Fig. 12, a).

Page Be, ere tt ran ve pa

eee ss ee ee Mia? tox Roe

a AL ep, s b as ai Hee

} Dea aFial igs. Ga 97a Bow Se espe! tae
ange i opt “fe alias od ts the J et

os
.

’ of To neta’, 3, j ae A 7% a ay Ped ran ae A
‘ 7 ek paleo aes ie? mz} ‘ie glen lad |
a >EF ars. Sua
_ owe f a inl = a, The vee a5 an
t On ;
3 > ow oO ar . Nas CWE ats Bs 7 aK

‘ a ee > e L ra uae bey) Se rox ¥ VO see
aS | Ti ee yo:

|

Ae ceah il) ey etd si MATa Le he eee ‘anites =
a | - oad ieee ok

. a -
ef

:
r :
: \
=

“ft * _
.

P
3
:
y :
* a

. =, ‘

} a J

ON THE SENSORY PIT OF THE CROTALINA. 49

On the Sensory Pit of the Crotaline.
By

G. S. West, B.A., A.R.C.S.,
Hutchinson Student, St. John’s College, Cambridge; Professor of Natural
History at the Royal Agricultural College, Cirencester.

With Plate 4.

- Tue distinguishing character of the group of vipers known

as the Crotaline is the depression or “ pit” on each side of
the head between the eye and the nostril. Cope! defines
the group as vipers possessing “a deep fossa on each side
behind the nostrils, partly occupying the excavated superior
maxillary bone;”? and Boulenger? gives the following
characters for the crotaline as distinguished from other
viperine snakes :—‘‘ A deep pit on each side of the snout,
between the nostril and the eye; maxillary hollowed out
above.”

The earliest mention of this feature—which is mainly
responsible for the appearance of extreme ferocity which
these snakes present—was by Russell and Home,* who gave
a rough figure of the pit in the head of the “ fer-de-lance”
(Lachesis lanceolatus). Leydig‘ in 1868 was the first
to prove that this pre-orbital pit was a sense-organ. He some-

1 Cope, ‘ Proc. Acad. Philad.,’ 1859, p. 334.

2 Boulenger, ‘Catalogue of Snakes in Brit. Mus.,’ vol. iii, 1896, p. 464.

3 Russell and Home, “Obs. on the Orifices in certain Poisonous Snakes
between the Nostril and the Hye,” ‘Phil. Trans. Roy. Soc.,’ 1804.

4F, Leydig, “Ueber Organe eines sechsten Sinnes.” “Zugleich als
Beitrag zur Kenntniss des feineren Baues der Haut bei Amphibien und
Reptilien.” ‘ Novorum Actorum Academ. Cesaree Leop. Carol. Germ.,’ nat.
cur., T. xxxiv, 1868.

vou. 43, PART 1.—NEW SERIES. D

50 G. 8. WEST:

what roughly investigated its general structure in Crotalus
horridus, Lachesis (Trigonocephalus) puniceus, and
L. atrox, and described the nature of the nerve terminations
in the organ. It was pointed out in Bronn’s ‘ Klass. u.
Ordnung. Thier-Reichs,’ Rept. III, Schlangen, 1890, p. 1411,
that the skin of the pit is not itself fixed to the hollow of the
maxillary bone; and although this is the first mention of
what is, perhaps, one of the most important features in the
structure of the organ, it is a somewhat erroneous statement.
The membrane stretched across the hollow in the maxilla
is not the “skin of the pit,’ but a thin partition (which I
shall fully describe further on) dividing the pit into two
chambers.

The peculiar osteological characters of this region of the
skull are mentioned by Peters! and also described by Taylor.?

The present investigation, which can obviously be little
more than an account of the anatomy and histology of the
organ, was undertaken at the suggestion of Dr. Gadow, to
whom I offer my best thanks for sundry information and for
specimens of Lachesis lanceolatus, Moreau, and L.suma-
tranus, Boul., from the Museum of Comparative Anatomy
at Cambridge.

The greater part of my material was very kindly supplied
to me by Mr. G. A. Boulenger from the duplicate specimens
in the British Museum. I have to tender him my sincerest
thanks for specimens of Lachesis gramineus, Russell, L.
mutus, Seba, L. atrox, Boul., Crotalus triseriatus, Boul.
(young and adult), and C. terrificus, Seba; also for embryos
of Crotalus scutulatus, Boul., Ancistrodon Blomhoffii,
Boul., and Lachesis nummifer, Boul. In addition to these
I had in my possession adult specimens of Ancistrodon
Blomhoffii from Japan, and a species of Crotalus from
North America.

1 W. Peters, ‘“ Ueber die craniologischen Verschiedenheiten der Grubenot-
tern (Trigonocephali),” ‘ Berliner Monatsb.,’ 1862, p. 670.

2 W.E. Taylor, “ Prelim. Notes on the Osteol. of the N- Amer. Crotalide,”
‘Amer. Naturalist,’ March, 1895, p. 282.

ON THE SENSORY PIT OF THE CROTALINA. ik

All the above were spirit specimens, and only a few were
in a sufficient state of preservation to admit of any detailed
histological investigation.

I. The Structure of the Organ in the Adult
Animal.

The precise position of the external opening of the
sensory pit is somewhat variable ; it is situated either in a
direct line between the eye and the nostril, or somewhat
below this line. In some species of Crotalus it is almost
immediately underneath the nostril, e.g. Crotalus terri-
ficus (cf. Pl. 4, fig. 4). Its form is generally oval or pear-
shaped, with the narrower end directed posteriorly. From
this posterior extremity a groove passes in a slightly upward
direction to the eye. This feature is more marked in some
species than in others, and among the snakes examined it
was most conspicuous in Lachesis mutus, L. atrox, L.
lanceolatus, and Crotalus terrificus. In the first-
mentioned animal the groove was partly protected by a
distinct flap of tissue, which on being lifted up exposed
more of the cavity of the pit (Pl. 4, fig. 2). In Lachesis
lanceolatus prolongations of the scales forming the an-
terior and inferior borders of the pit enter respectively into
the construction of the more external portions of the anterior
and inferior walls (Pl. 4, fig. 12).

The external orifice leads into a chamber, the inner wall of
which is very thin and membranous. This membranous wall
is a partition separating the outer chamber from a second
more deeply situated inner chamber.

The outer chamber (Pl. 4, fig. 14, 0.c.) is lined by a
smooth cuticle continuous with that of the rest of the head.
This cuticle is from 3°5 to 5 w in thickness, and in adult speci-
mens (after preservation) it easily comes away from the thin
wall of sensory tissue underlying it. At its junction with
the cuticle of the scales bordering the orifice there is a con-
voluted depression, lined with crenulated cuticle of the same

52 G.-S. WEST.

nature as that found between all the scales of the head (cf.
Pl. 4, fig. 14).

The inner chamber (Pl. 4, figs. 14 and 17, 7. c.) lies
deeper than the outer one, and is rather more posterior in
position, being situated immediately in front of the orbit,
and occupying a hemispherical hollow on the outer face of
the maxillary bone. Its posterior wall abuts against the
anterior wall of the orbit, and in the largest animals exa-
mined these walls were very thin and semi-transparent.
The outer wall of the inner chamber also forms the inner
wall of the outer chamber, and consists of a membranous
partition which I shall subsequently refer to as the “ pit-
membrane.” The cavity is not a completely closed one, but
communicates with the exterior by a minute pore at the
anterior angle of the orbit. As this pore lies under the
posterior margin of the lower antorbital scale it is not exter-
nally visible, but on reflecting the border of this scale it is
easily discernible (cf. Pl. 4, fig. 6, 0.7.), and readily admits of
the introduction of a bristle.

The inner chamber was mentioned by Russell and Home!
as an oval cavity between the pit and the eye. Its interior is
lined throughout by a continuous thin cuticle of not more
than 1 w in thickness. In some crotalines (e. g. Lachesis
eramineus) the cuticle is crenulated on both the internal
and external walls of the chamber, but in others (e. g.
Crotalus triseriatus, C. terrificus) only that of the
internal wall is crenulated, that of the external wall being
quite smooth.

This crenulated cuticle is of precisely the same nature as
that lining the depressions between the scales on the exterior
of the animal, and consists of an expanded sheet of knob-like
elevations, each of which is distinct from its neighbours.

1 Russell and Home, |.c.; they inferred from the situation of these oval
cavities that “they must be considered as reservoirs for a fluid which is
occasionally to be spread over the cornea; and they may be filled by the
falling of the dew, or the moisture shaken from the grass through which the
snake passes.”

ON THE SENSORY PI OF THE CROTALINA. 5Y3}

When seen in surface view (PI. 4, fig..11) these elevations
are rounded and of variable size, being from 9 to 14°5 w in
diameter. The characteristic embossed appearance is due to
the formation of the cuticle by a lining epithelium of hemi-
spherical cells, each of which has a height of about 7 to 9 p,
and a flat base resting upon more numerous, smaller, sub-
epithelioid cells. The nuclei of these cells are large oval
structures, containing a very distinct nucleolus. Immediately
underneath the cellular stratum, and forming a bed upon
which the latter rests, is a second layer consisting of dense
fibrous connective tissue containing blood-vessels, and be-
tween this layer and the hollow of the maxillary bone there
is a third stratum of delicate connective tissue, containing
numerous, relatively large, connective-tissue corpuscles. In
consequence of the delicate nature of this third stratum, the
lining epithelium of the chamber, together with the layer of
fibrous connective tissue upon which it rests, readily comes
away from the hollow of the maxillary bone, which in young
animals is a smooth hemispherical cavity, but in older
examples is generally irregularly pitted. A considerable
number of nerve-fibres are found in the connective tissue
underlying the cellular layer (cf. Pl. 4, fig. 10, c.t. f.), but I
have not succeeded in tracing their ultimate distribution to
the epithelial cells. The total thickness of tissue between
the inner cuticle of the chamber and the maxillary bone is
not more than about 50 pn.

The pit-membrane forms the inner wall of the outer
chamber and the outer wall of the inner chamber, and, as
both these chambers are lined by a thin cuticle, this mem-
branous partition consists of a thin sheet of tissue, bounded
by cuticle on both its external and internal faces. It is the
only truly sensory part of the organ, and is a semi-transparent
membrane of not more than 25 mw in thickness, somewhat
loosely stretched between the chambers, and forming a com-
plete wall of separation between them. As was mentioned by
Leydig,’ it exhibits a series of folds or ridges; these are only

1 Leydig, |. ¢.

54 G. S. WEST.

conspicuously evident in adult animals, and may vary in
number from about eight to twelve. They run in a somewhat
posterior direction from the periphery towards the centre,
each fold being a thickening of the membrane. Alongside
the folds, towards the edges of the membrane, are a few dark
brown, much-branched pigment-cells ; these are less numerous
in the adult than in the young animal, and are generally con-
spicuous only round the borders of the pit.

The nerve-trunks, which enter at the periphery, traverse
the above-mentioned folds, and by repeated divisions form
an immense number of fibres of extreme tenuity as they pass
towards the centre of the membrane; the ultimate divisions
of these minute fibres form a slight anastomosis before
terminating in the nerve endings.

The nerve terminations are cells of variable form,
many of them possessing a flat surface closely applied to the
cuticle of the outer face of the pit-membrane (cf. Pl. 4,
figs. 7—9). Under this cuticle more than one layer of nerve-
cells can be distinguished, and in most cases the cell walls
are very indistinct, although by careful teasing and staining
the form of the cells can be plainly observed. They are
somewhat triangular or even spindle-shaped in outline, one
pole being connected with a minute nerve-fibre, and in many
cases they exhibit a considerably branched appearance (PI. 4,
figs. 7 and 8). The nuclei are of a round or oval form, and
stand out prominently. The delicacy and indistinct nature
of the cell walls, which the most careful treatment scarcely
renders visible, caused Leydig! to describe and figure ag-
glomerations of nuclei round the small nerve branches. The
nerve terminations, although mostly confined to the outer
surface of the membrane, are also found in small numbers
near the edges of the inner surface.

The nerve supply for the entire sense-organ is-derived
from the V (trigeminus) nerve. The nerve bundles entering
the upper margins of the membrane are derived from the
ophthalmic branch, and those entering the lower margins are

1 Leydig, |. c., t. iv, f. 31,

ON THE SENSORY PIT OF THE GCROTALINA. 55

derived from several divisions of the maxillary branch
(cf. Pl. 4, figs. 13 and 14, Vio. and V.m.).

The pit-membrane is richly supplied with blood-vessels,
the main trunks of which enter at the periphery and run in
the folds alongside and internal to the nerve-trunks. From
these main vessels a capillary network extends through the
whole membrane, lying embedded in a sheet of fibrous con-
nective tissue internal to the nerve terminations. The blood
supply is derived from the ophthalmic artery.

In a section of the pit-membrane, such as that figured
(Pl. 4, fig. 15), the nerve terminations (v. ¢.) are seen imme-
diately beneath the outer cuticle (c.), then within these
the numerous nerve-fibres (n. f.), then a few blood-vessels
(b. v.) embedded in the fibrous connective tissue, and finally
the inner cuticle.

Most of the structure described was made out from serial
sections, cut through the anterior region of the head. In
the case of adult animals a mixture of equal parts of 1 per
cent. chromic acid and 1 per cent. hydrochloric acid was used
for decalcification; but in the case of the embryos the follow-
ing solution, recommended to me by Mr. J. Bles, was used
with success :—900 parts of 90 per cent. alcohol, 70 parts of
formalin, and 30 parts of acetic acid. For thorough decalci-
fication this mixture was required to be renewed every few
days for two or three weeks.

Sections were also cut of the entire soft tissues removed
from the pit, and treated by Weigert’s method for nerve
tissue. A figure is given of the edge of the pit treated in
this way (Pl. 4, fig. 17); in it only the larger nerve-fibres
can be distinctly seen.

II. The Structure of the Organ in the Embryo.

The outer and inner chambers of the pit arise by invagina-
tions of the epidermis. That which gives rise to the outer
chamber retains a widely open communication with the ex-
terior, but that which ultimately gives rise to the inner

56 G. S. WEST.

chamber only retains a communication with the exterior, in
the adult animal, by the small pore opening at the anterior
angle of the orbit. The second invagination, which gives
rise to the inner chamber, arises at the side of the first one,—
in fact, almost as a lateral dilatation of it.

The layers of tissue intervening between the inner chamber
and the maxillary bone are of greater thickness in the embryo
than in the adult, but there are only two of them. ‘The
lining cellular layer is very thin, but there is a considerable
development of the delicate layer of connective tissue imme-
diately outside the maxilla. This layer contains much
branched connective-tissue corpuscles, with large oval nuclei,
and close to the outer surface of the maxillary bone these
corpuscles are very numerous.

It is not until a late stage in development that the cham-
bers of the organ become lined by a distinct cuticle, and
the crenulated cuticle does not make its appearance until the
animal is still further advanced in growth.

The pit-membrane of the embryo is of much greater thick-
ness than that of the adult, and is not so transparent. Ina
well-grown embryo it is about 54 y in thickness, but this be-
comes reduced to less than half as the animal becomes adult.
It contains relatively fewer blood-vessels, and the reticula-
tion of capillaries, which forms such a conspicuous feature of
the structure in the adult, is by no means so marked. On
the outer side of the pit-membrane there are several layers
of flattened cells which rest upon a single layer of cubical
supporting cells, with large round nuclei. On the inner sur-
face of the membrane is a layer of somewhat short and very
broad cells with round nuclei similar to those of the outer
layer of supporting cells. Between these layers are large
numbers of non-medullated nerve-fibres and a few blood
capillaries. The nerve-fibres have prominent nuclei, and
mostly run close to the inner surface of the membrane.
They are continuous towards the outer surface of the mem-
brane with branched nerve-cells, the latter receiving pro-
longations direct from the innermost of the flattened cells on

ON THE SENSORY PIT OF THE CROTALINA. 57

the outer surface of the membrane. ‘These processes pass
between the cells of the supporting layer, and connect the
outer flattened nerve-cells with the inner branched nerye-
cells, the latter being in direct continuity with the nerve-

fibres (cf. Pl. 4, fig. 16).

III. Conclusion.

That this large and prominently situated sense-organ of
the pit viper must be of some considerable use to the animal
there can be no doubt, but no likely suggestion has been,
made concerning its probable function. - Russell and Home,!}
so long ago as 1804, expressed the idea that the apparatus
was a “ membrana nictitans,” but at that time the sensory
nature of the organ had not been discovered. Demoulins 2
(1854) writes, “organes particuliéres, dont Vusage ou la
fonction ne sont pas connus;” and Boulenger® (1890) states
that “the physiological significance of this pit is still
unknown.”

It is reasonable to suppose that an organ of this nature
must be concerned with some peculiarity in the mode of life
of the crotaline snakes, but no recorded observations offer
the slightest clue to the presence of anything aberrant in the
habits of these animals not exhibited by other vipers.

The thin wall separating the organ from the orbit and the
groove leading from the pit to the eye are somewhat remark-
able features, and may be of more significance than is at first
sight apparent. Again, the main partition stretched across
the hollow of the maxillary bone like the membrane of a
drum is an interesting feature, especially as it is the only
truly sensory part of the organ.

Another feature exclusively possessed by the Crotalinee
among venomous snakes is the sphincter near the termina-
tion of the poison duct, and, as the sense-organ is lodged

* Russell and Home, |. c. (1804).
2 Demoulins: cf. Bibron u. Demeril’s ‘ Erpetologie,’ 1854 (vide Leydig, l. c.).
3 Boulenger, ‘ Fauna of Brit. India; Rept. and Batrach.,’ 1890, p. 418.

58 G. S. WEST.

in the hollow of the maxillary bone, i.e. practically in the
base of the poison fang, and therefore in very close proximity
to the sphincter of the poison duct, can these features be in
any way associated ?

A careful study of the habits of these animals in their
native localities, especially with regard to any peculiarities
which they may exhibit in their mode of life, would no doubt
do much to elucidate the nature of the sense-organ; and it
seems probable that the exact function of this tegumental
sense-organ of the lateral line series, so characteristic
of a large group of viperine snakes, will not be thoroughly
understood until such an investigation has been made.

DESCRIPTION OF PLATE 4,

Illustrating Mr. G. 8. West’s paper “ On the Sensory Pit
of the Crotaline.”

Reference Letters.

b.v. Blood-vessels. c¢. Cuticle. c.¢./. Fibrous connective tissue (together
with a few fine nerve-fibres). gr. Groove passing from the pit to the eye.
h.gl. Harderian gland. ¢.c. Inner chamber of pit. ma. Maxillary bone.
n. Nostril. .f. Nerve-fibres. 2.¢. Nerve terminations. o0.c. Outer
chamber of pit. o.e¢. External opening of sensory pit. 0.7. Opening of
inner chamber to the exterior. p.d. Poison duct. yg. Pigment cells. p.m.
Pit-membrane. V.m. Maxillary branch of V nerve. V.o. Ophthalmic
branch of V nerve.

PLATE 4.

Fic. 1.—Lachesis mutus: head viewed from the left side, showing the
relative positions of the sensory pit and the nostril. Nat. size.

Fic. 2.—Lachesis mutus: anterior portion of left side of head. Nat.
size. The flap of tissue partly covering the external opening of the pit is
lifted up, showing the groove between the pit and the eye, and the external
opening of the inner chamber (0. 7.).

ON THE SENSORY PIT OF THE CROTALINA. 59

Fig. 3.—Lachesis mutus: enlarged surface view of the pit-membrane,
showing the characteristic folds.

Fic. 4.—Crotalus terrificus: head of adult from left side. Nat. size.

Fie. 5.—Crotalus scutulatus: head of embryo from left side. Nat.
size. (At this stage the scales are well marked.)

Fic. 6.—Lachesis Wagleri: anterior portion of head from left side.
x 2. The posterior edge of the lower antorbital scale is slightly reflected to
show the external opening of the inner chamber (0. 7.).

Fics. 7—9.—Crotalus triseriatus: nerve terminations from a teased-
up pit-membrane. xX 520.

Fic. 10.—Crotalus terrificus: portion of a section to show the tissues
between the inner chamber and the maxillary bone. x 520.

Fig. 11.—Lachesis gramineus: surface view of the crenulated cuticle
covering the inner wall of the inner chamber. x 500.

Fic. 12.—Lachesis lanceolatus: anterior portion of head from right
side. X 2.

Fic. 18.—Lachesis mutus: dissection of left side of head from above
to show the nerve supply of the sensory pit. Nat. size. The dotted line
indicates the depth of the pit.

Fic. 14.—Crotalus terrificus: vertical section through the entire
sensory pit of adult. x 18. Nerve-fibres from branches of the V nerve
are seen passing into the pit-membrane.

Fie. 15.—Crotalus terrificus: section of pit-membrane of adult animal.
x 520.

Fie. 16.—Crotalus scutulatus: section of pit-membrane of embryo.
x 520.

Fic. 17.—Crotalus triseriatus: section of lower portion of sensory
pit. > 75. The larger nerve-fibres are shown out black by Weigert’s
method.

ee a as VS
} ries Bak ie sia bapa sit
eet vee cathe Po ngepns. a; PEE AES SSR
Cae Pin. re Ae os
5 aes page aed hy mite is Tes - Hy
oe A eaipatiins Widagls od Pie aie J Sete
rant es) es MS Sa elit whe te
ayaa? 2 aes! pane eS reas Se geraed 28 witty te
OO DS > ea
idiecacr ij eae ay yebiota yr aay paeer hs tp? sdten ria
: (2E) Sel aioe sere eall ord nea ae
busty hokey at ap WAP OPO ad rai eey |

LAU a-ha a hae ener =
Ot 0 . Shtleatiy ae, ee

Fesxe ts cysts 3 sat Vol mates aie ;
dren SABI Powe: ae) agit wee HSE Wass

; : Te 2 .
ESSA GRY ( NOgHY sila seeay oo wi
eatctid Rs enc? wen! i rt
: 3 j Aas .
Oey aise- + re & - War POW cek ot +
Sree on 4% a
are veal as? fae) lati Ria satire to =
; j
WON AAS 1." ste TAT, PEE Ae Toad
Bisesiods we dete) Sacre ee ais
af
« 5
‘
‘
’, ;
di

EARLY STAGES OF DEVELOPMENT OF THE MOUSE. 61

A Reinvestigation of the Early Stages of the
Development of the PLGHEe:

By

J. W. Jenkinson, M.A.,

Assistant to the Linacre Professor of Comparative Anatomy in the University
of a

With Plates 5 and 6.

Axour a year and a half ago, while working in Professor
Weldon’s laboratory at University College, London, at cer-
tain points in the organogeny of the Mammalia, I cut a series
of sections of the pregnant uterus of a mouse, which proved
on examination to contain a much younger embryo than I had
anticipated ; and on searching through the literature of this
subject, I came across, in vol. xxxiii of this Journal, a paper
by Robinson (25) describing the development of the germinal
layers in the mouse and rat, and containing figures which, I
found, differed considerably from my own sections. I also
found that the observations of the author were not only in
startling disagreement with those of earlier investigators—
such as Selenka and Duval—on the same genus, but that they
were also totally at variance with what might have been
expected from the known embryogeny of other types. In
-addition, the writer of the paper seems to have been so cer-
tain of the accuracy of his own description that he ventured
to call in question the validity of the interpretations put by
others (van Beneden, Hubrecht, Selenka, Duval, etc.) on
their own work, and to substitute for them a generalisation
founded only on the single form which he had investigated,
but which he wished to apply to the whole of the Mammalia.
Still he was able, in a short paper—published subsequently (26)

62 J. W. JENKINSON.

—on Mustela ferox, to substantiate in some measure, as he
believed, his previous assertions. His work, however, was
received, if we may judge from an article of Born’s (8) and
from Duval’s (12) comments on “les précieuses observations
publiées récemment par Robinson sur la cavité de segmenta-
tion des Rongeurs,” with less criticism and suspicion than it
would seem to have deserved ; and I hope, therefore, that I
need not apologise for publishing the results of some investi-
gations which I have undertaken with the view of finally
deciding, if possible, whether Robinson’s account or that of
the earlier observers was correct. |

I have been fortunate enough to obtain between thirty and
forty embryos of the critical age (about the fifth day, when
the blastocyst is still free in the uterus). These were pre-
served in rather weak Flemming’s solution, which was injected
into the uterus, and the latter, with the contained embryos,
was cut into series and stained in various ways. In order to
ensure a most careful examination of the sections, I have
taken the precaution of making camera drawings of all of
them, and I append a list of those embryos of which I have
counted the nuclei, which will show, I think, that my series
is tolerably complete :

1.— 55 8.—126 15.—150 22.—195
2.— 95 9.—130 16.—151 23.—200
3.—100 10.—140 17.—161 24.—220
4.—105 11.—140 18.—170 25.—256
5.—105 12.—145 19.—170 26.—261
6.—106 13.—145 20.—170 27.—285
7.—125 14.—150 21.—185 28.—295

Table showing in order the number of nuclei in twenty-eight mouse
embryos. In the youngest of these the inner mass is quite undifferentiated,
and the blastocystic cavity is small. In the oldest the epiblastic mass is well
formed, and the hypoblast is partially extended round the inside of the much
enlarged blastocyst.

According to Robinson, the blastocyst of the mouse in its
earliest stage consists of a hollow oval vesicle, one end of
which—the “ floor”—is formed of a mass of cells two or
three deep, “‘ which is not separable into an inner mass of

EARLY STAGES OF DEVELOPMENT OF 'THE MOUSE, 63

hypoblast and an outer layer of epiblast” (25, p. 377),
while the other end, the “ roof,’’ and sides of the vesicle
are composed of a single layer of cells (see his figs. 38 and 4).
The “floor”? he terms hypoblast, the sides and “ roof” epi-
blast, the “cavity” segmentation cavity (Plate 5, fig. A). The
long axis of the blastocyst is parallel to that of the uterus
lumen, the “floor” is distal or anti-mesometric, and the
embryo isas yet free. The “ roof” and sides of the blastocyst
now increase very considerably in extent (see his fig. 5), and
in the next stage (his fig. 6) the embryo is found, still not fixed,
in a cylindrical anti-mesometric diverticulum of the uterus
lumen, which is lined not by the ordinary columnar cells, but
by a rather low cubical epithelium. The “ floor,” as before,
stains more faintly than the sides and “roof,” which latter
is (25, p. 879) “continuous with a mass of nucleated
protoplasm which occupies the interior of the vesicle,” and
which agrees in staining characters with the walls, though
its nuclei are small. ‘‘ In the interior of the inner mass is a
small cavity, from which a dark line extends to the surface of
the proximal pole of the ovum.” “It seems probable that
during the sixth day the thin roof of the blastodermic vesicle
is invaginated into the blastodermic cavity. . . . It does
not become divided into an outer layer and an inner mass, for
the inner mass is undoubtedly formed by invagination of
the thin roof of the vesicle’ (the spacing is mine) (fig. B).

The segmentation cavity thus becomes obliterated, and
a cavity is formed in the thickened floor by vacuolation, the
cavity of the yolk-sac (his fig. 7). By the development
of this a stage is reached in which the epiblastic knob (the
invaginated inner mass) is found resting on the concave
proximal end of an elongated yolk-sac, and covered by a cap
of trophoblast derived from the sides of the original segmenta-
tion cavity (his figs. 8 and 9) (Plate 5, fig.C). By the growth
of the trophoblast is formed the “Trager,” which subsequently
invaginates the epiblastic knob into the cavity of the yolk-sac
(his figs. 10, 11, and 12) (Plate 5, fig. D).

Such is Robinson’s description. In the last-mentioned

64, . J. W. JENKINSON.

respect it agrees with those of Selenka (27) and Duval (11),
but in his refusal to recognise a layer of trophoblast outside
the yolk-sac, as well as in his account of the mode of
development of the latter, and of the epiblastic knob, and of
their relations to one another, he differs widely from them.
I can only say that the study of my own preparations, quite
apart from more general considerations, has convinced me
that Selenka and Duval are right, though Duval’s figures
are somewhat diagrammatic, and that the interpretation
Robinson has put upon his sections is absolutely incorrect.
The formation of the primitive layers is not so different in
the mouse to what it is in other mammals, as Robinson’s
description would lead us to suppose. Ina young blastocyst,
such as he has figured, there are present (1) an outer layer,
one cell deep, of trophoblast, which is continuous over (2) an
inner mass which becomes differentiated into the embryonic
epiblast and the hypoblast, and which is quite distinct from
the overlying trophoblast, as my specimens invariably show
(see especially figs. 1, 2, 3, 4, and 5, the last of which is cut
transversely). Ata certain stage this proximal trophoblast
(the so-called Rauber’s cells of the rabbit) certainly becomes
very thin (figs. 6 and 7), but it never wholly disappears, and
soon thickens again (fig. 8) to form the “ Trager,” or, to use
a modern expression, trophoblastic syncytium, which is
destined to play an all-important part in the formation of the
placenta. Up to this point the development of the blasto-
cyst consists merely in the multiplication of the cells of all
layers, in the separation of the hypoblast, which commences
to grow round and across the inside of the trophoblast, from
the embryonic epiblast, which is now rounded off into a
definite spherical or ellipsoid mass, in the flattening of the
trophoblastic cells, and the considerable enlargement of the
blastocystic cavity. This agrees essentially with the account
of Selenka (27), Duval (11), and Cristiani (10), as may be seen
by a reference to their figures (Selenka, figs. 1, 2, 3, 6, 7, 9,
10; Duval, figs. 73—80, 83, 84; Cristiani, figs. 21, 24, 26, 28,

31), which call for little comment except that Duval does not

EARLY STAGES OF DEVELOPMEN'T OF THE MOUSE. 65

sufficiently emphasise the distinction between epiblast and
proximal trophoblast, a point to which he attaches consider-
able theoretical importance, and to which I shall have to
return later.

In attempting to account for Robinson’s error I am inclined
to believe that he had some difficulty in identifying the tro-
phoblast in a later stage (such as that which I have repre-
sented in fig. 8; compare Selenka, fig. 25,and Duval, fig. 90),
in which it is enormously extended and thinned out (Reichert’s
membrane) and not always easy to distinguish from the
submucosa of the uterus; and that his endeavour to give an
explanation of this has led him to a misinterpretation of the
earlier stages. In the first place he has assumed that the
unattached blastocyst, as it moves down the uterus to the
position it is permanently to occupy, does not rotate upon
itself in every possible direction (as it most certainly does),
and hence, with the help of a slight difference in staining, has
identified that end which he happened to find anti-mesometric
in a free blastocyst, and which is in reality the embryonic
knob, with the end which is distal, or anti-mesometric in a
fixed stage, that is to say the yolk-sac, and has therefore
labelled this end hypoblast (see his figs. 3, 4, 5; fig. A).

In the second place he has described an “ invagination ” of
the “roof” of the “ segmentation” cavity (his words in this
connection are somewhat inconsistent) from two sections only,
figured in his figs.6and 7. The first of these, I think, must
have passed through a fold in the trophoblast, such as are of
frequent occurrence in material fixed with picro-sulphuric
acid; this fold would be what he calls hypoblast; what he
has described as the epiblast I believe to be really so, or
rather the embryonic knob, but I feel sure that the line by
which he makes the central cavity of this epiblast communi-
cate with the exterior is an artifact. Fig. 7, I think, must be
tangential (it is the tenth of fourteen and cut obliquely !), the
appearance of the spaces (which he regards as separate,
though he advances no evidence in support of this, and as
segmentation and yolk-sac cavities respectively) being due to

VoL, 43, PART 1,—NEW SERIES, B

66 J. W. JENKINSON.

the irregularly folded surface of the trophoblast (I have
shown a section of a similarly distorted blastocyst in my
fig. 6).

And lastly, in figs. 8 and 9, he has made the distal and
lateral trophoblast continuous, not with the proximal tropho-
blast overlying the epiblastic knob (the distinction in staining
properties which he has introduced is, in my opinion, much
exaggerated, and in any case of insufficient value by itself),
while in figs. 10 to 12 he has ignored this layer altogether
(compare figs. C and D). With regard to Robinson’s
account of the isolated stage he had of the ferret, according
to which there is here also an epiblastic disc resting on the
surface of a hypoblastic vesicle, I think it must be regarded
as probable that he was not unbiassed by his previous inter-
pretation of the development of the mouse. But whether
this description is correct or not, I hardly think it justifiable
to base a speculative theory on an individual case, as Robinson
has done (and he is not the only one), more particularly in
mammalian embryology, a subject by no means easy to work
at in itself, and in which it is peculiarly difficult to bring the
phenomena into line with what is known of the development
of other Vertebrata. Before, then, I proceed to criticise the
theories of Robinson, Assheton, and Duval, I may perhaps be
allowed to briefly review the history of our knowledge of the
embryogeny of the Mammalia.

As is well known, the first accurate account of the de-
velopment of the mammalian ovum was given by van
Beneden, who published in 1875 a very careful description
of the segmentation and formation of the germinal layers in
the rabbit. According to him, one, the larger and clearer of
the first two blastomeres, divided more rapidly than the
other, and there resulted an embryo composed of an outer
layer of clearer cells derived from the former, surrounding,
except at one point, an inner mass of somewhat larger and
darker cells derived from the latter. The outer layer van
Beneden termed from its subsequent fate ectoderm, the inner
mass endoderm; he named the whole a metagastrula, and

EARLY STAGES OF DEVELOPMENT OF THE MOUSE. 67

the one point where the outer layer was incomplete a blasto-
pore. By the continued enlargement of the cavity which
appeared between the outer layer and inner mass the
blastodermic vesicle was formed, in which the inner mass of
rounded cells was attached at one point, the site of the
blastopore, to the inner surface of the hollow sphere of
flattened cells derived from the outer layer. The innermost
cells of the inner mass now began to spread out and grow
round the inner surface of this sphere, the remainder forming
a definite layer, the mesoderm, between the two primary
ones. The embryonic area was thus marked out, and it
became possible to definitely compare such a blastodermic
vesicle with the blastoderm of a chick, especially when it
was shown that the formation of the primitive streak,
amnion, and allantois was essentially the same in the two
cases. However, Rauber published almost at the same time
an account of his own independent researches, in which he
energetically maintained that what van Beneden had de-
scribed as mesoderm was in reality the embryonic ectoderm
(which was therefore derived from the inner mass), while
the flattened cells of the outer layer over these (since known
as Rauber’s cells) disappeared, the remainder of the outer
layer fusing with the edges of the disc of embryonic ectoderm.

These conclusions van Beneden refused to accept until
compelled to do so by Kolliker’s careful reinvestigation of
the subject published in 1882. Since then the researches of
Selenka on Mus, Arvicola, Cavia, and Pteropus, of Heape
and Lieberkiihn on Talpa, of Hubrecht on Erinaceus, Sorex,
Tupaia, and Tarsius, and of Assheton on Sus and Ovis, have
all tended to show, firstly, that in the typical mammalian
blastocyst the embryonic epiblast, and frequently the true
amnion, as well as the whole of the hypoblast, are derived
from the inner mass, while the outer layer, which we may
now, with Hubrecht, speak of as the trophoblast, gives rise
to the false amnion, and comes into close connection with the
uterus, playing a very important part in the formation of the
placenta; and secondly, that while the mode of formation of

68 J. W. JENKINSON.

_ the amnion is exceedingly variable, there is always a stage in
which the knob of embryonic epiblast is included in the
trophoblast or false amnion. In some cases (Hrinaceus,
Cavia, Pteropus) a cavity, the amniotic cavity, which never
communicates with the exterior forms inside this knob; in
others (Mus) the cavity is only temporarily in connection
with a cavity in the Trager, and in others again (Lepus,
Vespertilio, Sus, Ovis, Sorex, Talpa, Tupaia, Tarsius) the
epiblastic knob folds or flattens out, the overlying tropho-
blastic cells (Rauber’s cells) disappear (though this is denied
by Assheton for the rabbit, and Heape for the mole), and |
the amnion then forms in the characteristic Sauropsidan
manner.

Most writers have, therefore, agreed that van Beneden’s
theory of the metagastrula was premature, that the primitive
streak really represents the point where gastrulation takes
place, and that the so-called blastopore in those forms in
which it has been found (Lepus—though its existence here
is denied by Assheton—Talpa, Vespertilio, and Didelphys)
is a structure of unknown significance. At the same time it
must be admitted that Selenka’s account of the development
of the opossum is difficult, if not impossible, to reconcile
with what we know of other mammals. It may be that a re-
investigation of the early stages in the segmentation of the
Marsupial ovum will throw fresh light on this subject, or
possibly the development of this group of animals is quite
different to that of the remaining Placentalia.

More recently, however, Duval (12) has announced his
intention of resuscitating and defending the abandoned meta-
gastrula theory of van Beneden. His views are based on his
account of the development of Vespertilio murinus. There
is in this mammal, according to Duval, an epibolic gastrula,
of which the outer layer of clear cells is derived from two of
the blastomeres, the inner mass of dark cells from the re-
maining two in the four-celled stage, the earliest which
Duval was able to find. At the opposite pole of the ovum to
that at which the inner mass is attached (the point where van

EARLY STAGES OF DEVELOPMENT OF THE MOUSE. 69

Beneden, Heape, and Selenka found the “blastopore”’),
Duval also figures a gap in the outer layer to which he gives
this name. The inner mass is, according to him, endoderm
alone, and soon becomes everywhere reduced to a single
layer of more or less flattened cells spread over the inner
surtace of the ectoderm, while the epiblastic knob is produced
by an inward proliferation of certain cells of the outer layer
(see figs. H, F, G). This is also, it should be said, the
account given by Duval of the formation of the embryonic
epiblast in the mouse, rat, and guinea-pig. Now, as far as
the mouse is concerned, I have little hesitation in saying that
Duval’s interpretation is wrong. I have already said that
his figures are diagrammatic, and I think a comparison of
them with Selenka’s or mine will convince anyone that this
is so. In my series of embryos, which I think it will be
admitted is a tolerably complete one, I have the clearest evi-
dence that the inner mass, the cells of which are at first all
alike, becomes gradually differentiated into a compact epi-
blastic knob and hypoblastic cells, many of which are isolated
from one another as they creep round the inside of the
blastocyst. The trophoblast cells overlying the inner mass
are, almost from the first, as Selenka originally described
them, very much flattened, and could not well be supposed
to have given rise by proliferation to the rounded cells of the
embryonic epiblast ; and, besides, all the mitoses that I have
found in the trophoblast have the axes of their spindles tan-
gential. Finally, though I should be unwilling to lay any
great stress upon this, it seems to me a little remarkable that
the ratio of the number of cells in the inner mass to that of
those of the trophoblast is sensibly equal, in those stages in
which the epiblastic knob is already beginning to be differ-
entiated, to what it is in the earlier stages, in which no
difference is to be detected among the cells of the inner mass.
I think, therefore, we may take it that Duval’s account of
the mode of formation of the embryonic epiblast in the
mouse is not correct, and if so we may fairly regard with a
certain amount of suspicion his description of the same pro-

70 J. W. JENKINSON.

cess in the bat. Judging from what I know to be the effect
of picro-sulphuric acid upon delicate blastocysts, I should
think it quite possible that his “ blastopore” is an artifact.
But, apart from this, there is a very serious gap in his series
at what is, for his theory, the most critical point; for he has
no embryos whatever between the stage in which the inner
mass is still several cells deep, at the point of its original
attachment to the outer layer, which is everywhere composed
of a single layer of cells, and the stage in which, as he inter-
prets it, the inner mass has completely spread out as a single
layer, while the cells of the outer layer have at one point
proliferated to form the “ amniotic mass.” The cells of the
inner layer are at this point, as he admits, closely related to
those of the “amniotic mass” (he homologises this fusion
with the primitive streak), and taking into consideration
what we have seen of his description of a similar stage in
the mouse, together with the absence of the hypothetical
stage (fig. F), in which the cells of the outer layer and
those of the inner mass are alike disposed in a single layer,
it does not seem impossible that Duval’s interpretation may
here also be at fault. But, whether the bat differs from
most other mammals in this respect or not, it seems a little
hazardous to suppose that other authors have misinterpreted
the phenomena observed by them in such different mammals
as Talpa, Tupaia, Sorex, Lepus, Mus, Cavia, and—since
Duval wrote—Tarsius, Ovis, and Sus.

It is not necessary to criticise in detail Duval’s attempt to
interpolate a hypothetical ‘‘stade didermique primitif,” not
observed even by himself in Vespertilio, among the stages
figured by these writers, because any one who will take the
trouble to look at these figures and descriptions (Heape, 18,
14; Hubrecht, 15—19; Assheton, 2, 3; Selenka, 27—30)
will be able to convince himself that Duval’s interpretation
of their facts is exceedingly strained. Indeed, Assheton has
already expressed his opinion that such a stage could hardly
have been overlooked by the many investigators who have
worked on the rabbit ; and as far as Mus, Sorex, Tupaia, and

EARLY STAGES OF DEVELOPMENT OF THE MOUSE, (A!

Tarsius are concerned, all of which I have myself studied, I
believe Duval’s hypothesis to be quite untenable, particularly
in the last-mentioned case, in which the epiblastic knob is
differentiated long before the hypoblast grows out to form
the umbilical vesicle. Hrinaceus, it must be admitted, is an
exception, in so far as here the epiblastic knob does not begin
to form until some time after the hypoblast is completely
separated off; but we must at the same time remember that
the earliest stages in the development of this mammal are
quite unknown to us.

We may now turn to a consideration of the far-reaching
speculations of Robinson (25) and Assheton (2). Of these
Assheton’s is partly based on that of Robinson, while both
rest upon phenomena which their authors have, or supposed
themselves to have observed, in a single genus alone.

I have already endeavoured to show that Robinson’s
account of the early development of the mouse is devoid of
any serious basis in fact; and I need, therefore, now only
briefly discuss his extension of this erroneous description to
the rest of the Mammalia.

Starting from a comparison of the blastocystic cavity with
the segmentation cavity, and of the embryonic knob with the
yolk-cells of the lower Vertebrata (an homology which might
be criticised on more grounds than one), he finally arrives at
the conclusion that the epiblast forms a small knob on the
surface of a hypoblastic vesicle, round which it is unable to
grow as it does in the Sauropsida and in Hrinaceus; and
seizing on the statement of van Beneden and Julin (since,
however, contradicted by Duval), that in the bat the hypo-
blast does not completely grow round at the anti-embryonic
pole of the blastocyst, he puts forward the hypothesis that it
is in reality the edges of the epiblast which are here free,
while the hypoblast forms a completely closed vesicle round
which the epiblast grows, and not conversely (fig. H), and
this hypothesis he proposes to extend to the rabbit, mole,
and other mammals. This strained interpretation has been
already contested by Assheton, and a glance at his figures,

72 J. W. JENKINSON.

and at those of Heape, Hubrecht, Selenka, Duval, and others,
will show how impossible it is.

Now, although Assheton refused to accept these specula-
tions of Robinson, he fully acquiesced in the account given
by the latter of the development of the mouse; and having
found in the sheep (although not in the pig) what he believed
to be evidence for the hypoblastic nature of the trophoblast,
he has proceeded to apply this as a generalisation to every
other mammalian blastocyst. The only criticism of this is,
as before, to refer the reader to the original descriptions and
figures of the various authors, an inspection of which will
show whether the ingenious diagrams which Assheton has
published are defensible or not. It will be more profitable
to consider the basis in fact upon which he believed his
theory to rest, and the speculative arguments which he has
urged in its support.

Assheton found that in some, though not all of his speci-
mens of the segmented ovum of the sheep, certain of the
cells which were placed internally stained less deeply than
the others (fig. L). These less deeply stained cells he
thought he could trace to the epiblastic knob of the blasto-
cyst, the outer darker cells to the trophoblast ; and since he
found that some of the cells of the inner mass prior to the
appearance of the blastocystic cavity (fig. M), and the
hypoblast cells in a later stage (fig. N) agreed with the
trophoblast, and not with the epiblast in their staining
character, he came to the conclusion that the trophoblast
was hypoblastic in origin, and formulated the theory that
the blastocyst of the placental Mammalia represents a Sau-
ropsidan ovum which has lost its yolk, and into which the
embryonic epiblast has sunk.

Now I think it must be admitted that morphological con-
clusions drawn from a slight difference in staining reaction
are open to grave suspicion, especially when the difference
is not to be detected in all the preparations, and is absolutely
unsupported by any other evidence, such, for instance, as
the direction of the nuclear spindles, which in Assheton’s

EARLY STAGES OF DEVELOPMENT OF THE MOUSE. 73

fig. 9, for example, are just in the opposite direction to what
one would have expected on his theory ; when, moreover, an
allied animal, the pig, affords no confirmation of such a view,
and the evidence furnished by all other Mammalia is dis-
tinctly opposed to it ; and is it not a little unfortunate in this
connection that the same author’s figures of the rabbit (1)
should show a staining reaction which suggests the very
opposite interpretation to that which he has advoeated here
for the sheep (see his figs. 22, 24, 27). If this is so,
then the basis of fact upon which Assheton has relied
becomes very slender indeed. We will turn, therefore, to a
consideration of the general arguments advanced in favour
of the hypothesis; and we will admit for the moment that
the Mammalia are immediately descended from ancestors
with a megalecithal egg, from which the yolk has in all the
Placentalia practically disappeared. Assheton supposes (see
his diagrams A—D) simply that the epiblast, which in a
Sauropsidan grows over the surface of the yolk, has ceased
to do so in all mammals except Monotremata, and has instead
become included in it; and that the blastocystic cavity cor-
responds to the archenteron, which he (and also Robinson)
believes to arise in the Sauropsida as a split amongst hypo-
blast cells.

I am aware that the current view of the origin of the hypo-
blast, as set forth in the ordinary text-book of embryology,
is that it arises from those yolk-nuclei which are separated
from the blastoderm by the first tangential division. Now I
do not wish to express a positive opinion in this matter, be-
cause I have not yet had the opportunity of looking at pre-
parations of the blastoderm of the chick during the early
stages of segmentation ; but, judging from what I have seen
of some very excellent preparations of the early stages of
incubation, I should lke to suggest that the “ Dottersyn-
cytium,” as it seems undoubtedly to be in Teleostei, and
possibly in Elasmobranchii, and as Mehnert has stated it to
be in Emys (22), is also in the chick a structure entirely
sui generis, separated at an early stage from the primitive

74, J. W. JENKINSON.

blastoderm, but certainly not derived from the “ Neben-
spermakerne”’ of Riickert and Oppel. The function of this
structure is simply ‘‘ Dotter-resorption,” and its nuclei do not
form any part of any embryonic layer whatever, but swell,
divide directly, disorganise, and ultimately disappear; while
the hypoblast proper is derived later on from the blastoderm.
If this were so, then on the assumption that the mammalian
ovum was once megalecithal and similar to that of the Sau-
ropsida, the theoretical reasons which Assheton has urged
would lose greatly in force; for it would not in that case be
the trophoblast and hypoblast which were derived in the
segmented ovum from a cell or group of cells separate to
that which gave rise to the epiblast, but the epiblast and
hypoblast which arose in common from a group of cells,
namely from the inner mass, which was distinct from the
trophoblast.

At the same time it must be remembered that in the Am-
phibia yolk-cells and hypoblast are identical, and that in the
Gymnophiona we have what appears to be a condition inter-
mediate between the former and the Sauropsida ; though even
here, judging by Brauer’s figures (9), a good many yolk-
nuclei are left unaccounted for after a definite epithelium has
been formed to make the floor of the gut.

It might still be urged, of course, that the trophoblast was
the representative of the “ Dottersyncytium,” but this is not
the point in Assheton’s paper. Minot (28), indeed, has insti-
tuted a comparison between the Mammalian blastocyst and
the segmented ovum of Amphibia, in which he does homo-
logise the trophoblast of the former with the yolk-cells of the
latter, which he supposes to have grown over the epiblast as
Rauber’s ‘‘ Deckschicht” (see figs. I, K). He, however, does
not treat the hypothesis at great length, and dismisses rather
lightly the somewhat fatal objection that in the mammalian
blastocyst hypoblast cells are found at an early stage under-
neath the epiblastic mass.

But, setting aside these perplexing and somewhat unpro-
fitable speculations, there is a much more serious objection

BKARLY STAGES OF DEVELOPMENT OF THE MOUSE. 75

to Assheton’s theory; an objection which he himself has
seen. If the trophoblast is hypoblastic, then the false
amnion of the Mammalia cannot possibly be homologous
with that of the Sauropsida, and the character by which
these two groups have up till the present been distinguished
from the Anamnia has no morphological value whatever.
Assheton pleads that in the Sauropsida it is from the hypo-
blast that the embryo draws its first nourishment, and that
as the trophoblast performs a similar function in the Mam-
malia, it may therefore be regarded as hypoblastic; I can
only say that to do this seems to me to substitute analogy
for homology, in short to abandon the morphological stand-
point altogether; and as such the argument stands self-
condemned.

In conclusion, speaking for myself, I believe that all
attempts to institute homologies between the mammalian
blastocyst as such, and the segmented ova of other Verte-
brata, are foredoomed to failure, just because the conditions
under which the Mammalian ovum develops are so peculiar,
and because we have at present no clear idea of how this
ovum came to be derived from that of either an amphibian
or reptilian ancestor. The phenomena which we observe in
the early ontogeny of the Mammalia are, in my humble
opinion, absolutely sui generis; and I believe that the
only sure method of arriving at any homologies at all is to
take, not the ovum, but the embryo at a time when it
possesses an organ, such as an amnion, which can be de-
finitely compared with a similar organ in other groups, and
from this to argue backwards to an earlier stage.

Until lately two separate processes have been, so far as
concerns the Vertebrata, confused under the term “ gastrula-
tion.” The first is a movement of the vegetative cells to-
wards the animal pole, inside the cells of which they may,
and do in small-yolked, holoblastic eggs, become included ;
the second is a backward and lateral overgrowth and in-
growth of animal cells to form a notochordal and mesodermal
plate, and possibly the roof of the gut on the inside, and on

76 J. W. JENKINSON.

the outside the medullary plate, which thus lies on what was
originally the vegetative pole of the egg (a somewhat awk-
ward fact for such hypotheses as Minot’s). This second
process appears to be represented in the higher Vertebrata
by the primitive streak; the first (in the Sauropsida at
any rate) by the growth of the epiblast of the blastoderm.
These are facts which any one may observe for himself in
the frog, and which, taken in conjunction with Brauer’s
remarkable and brilliant work on Hypogeophis, do much to
remove Lwoff’s (21) original generalisation from the region
of pure hypothesis.

It would seem, therefore, that a knowledge of the axes of
the ovum during segmentation is necessary before it is
possible to speak of gastrulation at all; and it is just this
knowledge which, for Mammalia, we do not possess. More
than that, Assheton was unable to confirm in the rabbit van
Beneden’s statements as to the inclusion of cells derived from
one of the first two blastomeres in a layer derived from the
other, though Duval has, indeed, reasserted this for the bat.
I therefore think it preferable to avoid the term gastrulation
altogether, whether applied to the formation of the blasto-
cyst, or to the primitive streak; and not even to use the
alternative of hypergastrulation suggested by Selenka to get
over the original difficulty of the inclusion of epiblast as well
as hypoblast in the inner mass.

If it is necessary to employ any term at all to express the
processes which result in the formation of the blastocyst, I
should prefer to speak of a very early development of the
amnion (due to whatever causes) in placental mammals.

This is an actual ontogenetic fact in Hrinaceus, Pteropus,
and Cavia; and as it is a stage through which the embryos
of all Placentalia pass, I think it is justifiable to believe that
it is, for them, the more primitive one. But that this
points to the direct descent of the Mammalia from a vivi-
parous amphibian ancestor, and to the secondary oviparity,
and formation of the amnion by folds in the Sauropsida, as
Hubrecht has suggested, is a hypothesis on which I will not

EARLY STAGES OF DEVELOPMENT OF THE MOUSE. vit

venture at present to express a very definite opinion, except
that I am inclined to believe that a via media might be
found, which should avoid those grossly mechanical explana-
tions of the origin of the amnion and allantois, against which
this author has rightly protested, on the one hand, and on the
other the very serious difficulties in which the Monotremata
involve us when we attempt to derive the Mammalia directly
from an Amphibian ancestor with a small-yolked and holo-
blastic ovum.

Before I conclude I must express the great obligations I
am under to Professor Weldon, to whose kind encouragement
and sympathy I owe it that I have been able to undertake
this piece of work at all; to Professor Lankester, who allowed
me both time and space in his laboratory here last year; to
Mr. G. C. Bourne and Mr. (now Professor) H. A. Minchin
for many hints and suggestions; and last, but by no means
least, to Professor Hubrecht, with whom I spent five weeks
last Christmas, for his generosity in giving me free access to
his laboratory and his preparations, and for his courtesy in
placing so much of his own valuable time at my disposal.

Oxford, Jwy, 1899.

POSTSCRIPT.

Since the above was written van Beneden has published
in the ‘ Anatomischer Anzeiger’ of last September an account
of the development of the bat (Vespertilio murinus), which
to my mind completely disposes of Duval’s hypothesis of a
“stade didermique primitif,” and of the origin of the embry-
onic epiblast from the trophoblast.

Van Beneden’s description and figures show in the clearest
way that the epiblast in the bat, as in other forms, is a part
of the inner mass; and I need here do no more than give a
few quotations from his paper, including his remarks on the
“blastopore ” figured by Duval at the anti-embryonic pole
of the blastocyst (Duval, fig. 24). For the details the reader
must be referred to the paper itself,

78 J. W. JENKINSON.

“T/opinion de Duval, sur la fermeture tardive du blasto-
pore au pole anti-embryonnaire du blastocyste, repose sur
Vétude d’une vésicule blastodermique qui, 4 mon avis, avait
été accidentellement rompue ” (p. 313).

roe . Je crois pouvoir affirmer, en ce qui concerne le
Murin, que, chez ce Cheiroptére comme chez le Lapin, les
deux feuillets de l’embryon procédent l’un et l’autre, entiére-
ment et exclusivement de la masse cellulaire interne de l’couf
segmenté, que la couche enveloppante [the trophoblast of
Hubrecht] n’intervient en rien dans )’édification de l’embryon
proprement dite? (p..817);

.... dai trouvé la démonstration évidente du fait que
ce que Mathias Duval appelle lamas amniotique procéde con-
curremment avec la couche qu’il nomme endoderme de la
masse interne de l’ceuf segmenté” (p. 318).

December, 1899.

List oF PAPERS REFERRED TO IN THE TEXT.

1. Assueton, R.—“< A Reinvestigation into the Early Stages of the Deve-
lopment of the Rabbit,” ‘ Quart. Journ, Micr. Sci.,’ xxxvii, 1894.

2. AssHeton, R.—‘ The Segmentation of the Ovum of the Sheep, with
Observations on the Hypothesis of a Hypoblastic Origin of the Tropho-
blast,” ‘Quart. Journ. Micr. Sci.,’ xli, 1898.

3. Assurton, R.— The Development of the Pig during the first Ten Days,”
‘Quart. Journ. Mier. Sci.,’ xli, 1898.

4. van BenepEn, E.—‘‘ De la maturation d’ceuf, de la fécondation, et des
premiers phénoménes embryonnaires chez les Mammiféres, d’aprés les
observations faites chez le lapin,”’ ‘ Bulletin de l’Académie Royale des
Sciences de Belgique,’ 1875.

5. van BENEDEN, E.—“ Recherches sur |’Embryologie des Mammifeéres :
la formation des feuillets chez le lapin,” ‘ Arch. de Biol.,’ i, 1880.

6. van BeNEDEN, E., et Junin, C.—‘‘ Observations sur la Maturation, la
Fécondation, et la Segmentation de |’@uf chez les Cheiroptéres,”
‘ Arch. de Biol.,’ i, 1880.

7. vaN BENEDEN, E., et Jutin, C.—‘‘ Recherches sur la Formation des
Annexes foetales chez les Mammiféres,” ‘ Arch. de Biol.,’ v, 1884,

15.

16.

17.

18.

19.

20.

2i.

22.

23.
24.

25.

EARLY STAGES OF DEVELOPMENT OF THE MOUSE, 79

. Born.—“ Erste Entwickelung svorginge,” ‘Kregebnisse der Anatomie

und Entwickelungsgeschichte,’ 1892.

. Braver, A.— Beitrige zur Kenntniss der Entwickelungsgeschichte

und der Anatomie der Gymnophionen,” ‘ Zool. Jahrb.,’ x, 1897.

. Ortstrant.— L’Inversion des Feuillets blastodermiques chez le rat

albinos,” ‘Arch. de Phys. norm. et path.,’ 1892.

. Duvat, M.—‘ Le Placenta des Rongeurs,” ‘ Journ, de l’Anat. et de la

Phys.,’ 1889-92.

. Duvat, M.—* Etudes sur l’Embryologie des Cheiroptéres,” ‘Journ. de

Anat. et de la Phys.,’ 1895-6.

. Hears, W.—“ The Development of the Mole: the Ovarian Ovum, and

Segmentation of the Ovum,” ‘ Quart. Journ. Mier. Sci.,’ xxvi.

. Hearse, W.—“‘The Development of the Mole: the Formation of the

Germinal Layers, and Early Development of the Medullary Groove and
Notochord,”’ ‘ Quart. Journ. Mier. Sci.,’ xxiii.

Husrecut, A. A. W.—“ Studies in Mammalian Embryology. I. The
Placentation of Erinaceus europeus, with remarks on the Physio-
logy of the Placenta,” ‘ Quart. Journ. Mier. Sci.,’ xxx.

Husrecut, A. A. W.—* On the Didermic Blastocyst of the Mammalia,”
‘Report of Brit. Assoc.,’ 1894.

Husrecut, A. A. W.—“ Studies in Mammalian Embryology. II. Tie
Development of the Germinal Layers of Sorex vulgaris,” ‘Quart.
Journ. Mier. Sci.,’ xxxi.

Husrecut, A. A. W.—“ Die Phylogenese des Amnions und die Bedeutung
des Trophoblastes,” ‘ Verhandelingen der Koninklijke Akademie van
Wetenschappen te Amsterdam,’ 1895.

Husrecut, A. A. W.—‘‘ Die Keimblase von Tarsius,”’ ‘ Festschrift fiir
Carl Gegenbaur,’ 1896.

Koriiker, A.—“ Die Entwickelung der Keimblatter des Kaninchens,”
‘ Festschrift zur Feier der Universitat zur Wurzburg,’ 1882.

Lworr.— Die Bildung der primaren Keimblatter,” ‘ Bull. Soc. Imp.,
Moscow,’ viii, 1894.

Mennert, E.—‘Gastrulation und Keimblitterbildung der Emys,”
‘Morph. Arbeiten’ von Dr. Gustav Schwalbe, i, 3, 1891.

Minor, C. S.—‘ Human Embryology,’ New York, 1892.

RauBEeR.—‘ Die Entwickelung des Kaninchens,” ‘ Sitzungsb. der Natur-
forsch. Gesellsch. zu Leipzig,’ 1875.

Rosinson, A.—‘“‘ Observations upon the Development of the Segmenta-
tion Cavity, the Archenteron, the Germinal Layers, and the Amnion in
Mammals,” ‘ Quart. Journ. Mier. Sci.,’ xxxiii,

80 J. W. JENKINSON.

26. Rosinson, A.—‘ Observations upon the Development of the Common
Ferret, Mustela ferox,” ‘ Anat. Anz.,’ viii.

27. Sevenka, E.—‘ Keimblatter und Primitivorgane der Maus,’ Wiesbaden,
1883.

28. Sevenka, .—‘ Die Blatter umkehrung im Hi der Nagethiere,’ Wiesbaden,
1884.

29. SevenKa, E.—‘ Das Opossum,’ Wiesbaden, 1886-7.

30. Setenka, E.—‘ Studien tiber Entwickelungsgeschichte der Thiere,’
funftes Heft, zweite Halfte: ‘‘ Keimbildung des Kalong (Pteropus
edulis), Wiesbaden, 1892.

81. Vircuow, H.—‘ Dottersyncytium, Keimhautrand, und Beziehungen zur
Konkrescenzlehre,’ ‘ Ergebnisse der Anatomie und Entwickelungs-
geschichte,’ 1896.

DESCRIPTION OF PLATES 5 & 6,

Illustrating Mr. J. W. Jenkinson’s paper on “ A Re-investiga-
tion of the Harly Stages of the Development of the Mouse.”

PLATE 5.
(The dark is hypoblast, the light epiblast.)

Fics. A—D.—Diagrams to illustrate Robinson’s account of the develop-
ment of the mouse.

In A the blastula is shown, with a thin-walled epiblastic roof and a thick
hypoblastic floor. In B and C the roof has been invaginated to form the
epiblastic knob, covered by the trophoblast, and the cavity of the yolk-sac has
arisen by vacuolation of the floor. In D the trophoblastic Trager has
invaginated the epiblastic knob into the yolk-sac.

Fies, E—G.—Diagrams to illustrate Duval’s theory of the origin of the
epiblastic (amniotic) mass. F is the hypothetical ‘‘stade didermique pri-
mitif.” In G the amniotic mass is produced by the proliferation of the outer
layer.

Fic. H.—Diagram to illustrate Robinson’s theory of the partial over-
growth of the epiblastic trophoblast over a closed hypoblastic vesicle.

Figs. I, K.—Diagrams to illustrate Minot’s comparison of the mammalian
blastocyst, K, with the frog’s blastula, I. In K the hypoblast has decreased
in size through loss of yolk, and has grown over the epiblast as Rauber’s
layer.

Fics. L—O,—Diagrams to illustrate Assheton’s hypothesis of the hypo-

EARLY STAGES OF DEVELOPMENT OF THE MOUSE. 81

blastic nature of the trophoblast. In L the outer layer of cells are hypoblast,
the inner mass embryonic epiblast. In N the hypoblast of the inner mass is
seen to have a common origin with the outer layer, since in M the blasto-
cystic cavity appears inside the hypoblast. In O the hypoblast proper is
growing round inside the trophoblast.

PLATE 6.

Fie. 1.—A young blastocyst (95 cells) in which the cavity is small, and
the inner mass undifferentiated.

Fig. 2.—A slightly older blastocyst (140 cells). The inner mass is still
undifferentiated. Owing to the slight obliquity of the section the cavity does
not appear to be as large as it should.

Fic. 3.—A blastocyst of 170 nuclei, in which the inner mass is beginning
to differentiate into epiblast and hypoblast, and in which the trophoblastic
cells which overlie the inner mass are slightly flattened.

Fic. 4.—A blastocyst of only 105 cells, but in which the inner mass is
already differentiated.

Fie. 5.—Transverse section through the embryonic end of a blastocyst of
about the same age as Fig. 3. The trophoblast cells are quite distinct from
those of the inner mass.

Fie. 6.—A blastocyst of about 200 nuclei. The trophoblast is much
crumpled and folded, and is flattened over the inner mass. The latter is well
differentiated into a rounded epiblastic knob and scattered hypoblastic cells.

Fie. 7.—A much enlarged though still unfixed blastocyst with nearly 300
nuclei. Over the epiblastic mass the trophoblast is very much stretched,
and the hypoblastic cells are commencing to grow round the inside of the
blastocyst.

Fie. 8.—A very much older embryo which is firmly embedded in the
uterine crypt, of which the epithelium has disappeared. The trophoblast has
proliferated to form the “ Trager,” which has invaginated the epiblastic knob,
in which the amniotic cavity is apparent, into the yolk-sac.

Figs. 1—7 were drawn with Zeiss, obj. 2 mm., comp. oc. 4, xX 740;
Fig. 8 with Zeiss, obj. D, comp. oc. 4, x 350.

Am. Amniotic cavity. 2. Embryonic epiblast. 4. Hypoblast. JZ. Inner
mass. JZ. Trophoblast. Zr. Trager. Y. S. Yolk-sac.

voL. 43, part 1.—NEW SERIES. F

- PY
Z oa 7 , oan 7
cc 7
iT _ = =
4 . -
> ~
* —
ou.
: 7 - a
<<
Pa 4
F

1) a
*

TAPEWORM FROM APTERYX. 83

The Structure of the Rostellum in two New
Species of Tapeworm, from Apteryx.

By

W. Blaxland Benham, D.Sc., M.A.,
Professor of Biology in the University of Otago, New Zealand.

With Plates 7 and 8.

On the 11th November, 1898, I received from the Curator
of the Botanical Gardens the body of a young specimen of
Apteryx Bulleri, one of a lot recently purchased by the
Corporation of Dunedin, and placed in the public gardens of
the city.

The intestine of the bird was literally crammed with para-
sites, the duodenum contained a great quantity of very small
Cestodes, measuring a sixteenth to an eighth of an inch in
length. Further down were a number of larger Cestodes of
another species, and measuring three or four inches in length.

Still further down, and mixed with these, were a number
of large yellow Echinorhynchus, which occurred in still
larger quantities throughout the greater part of the intestine,
as far as the origin of the ceca. I counted more than
100 Echinorhynchus, and 150 of the larger Cestodes.

In the gizzard were a number of Nematodes, measuring
about half an inch in length, as well as a number of small
isolated proglottids of some tapeworm. ‘These appear to
belong to the small species occurring in the duodenum, where
also isolated proglottids occur, and their occurrence in the
gizzard must have been due to regurgitation.

84 W. BLAXLAND BENHAM.

I suggest the names Drepanidotwnia minuta and
D. apterygis for these two new Cestodes.

I. Drepanidotenia minuta, n. sp.

The smaller of the two Cestodes occurs in the duodenum ;
when killed it measures from an eighth to a sixteenth of an
inch in length, with a breadth of one twenty-fifth of an inch.
The scolex is followed by about ten or twelve apparent pro-
glottids, all of which are of the same breadth. The whole
strobila thus is nearly rectangular, with the exception of
the curved scolex. In horizontal section—section, that is,
in a plane parallel to the broad surface of the worm—it
shows a maximum of eighteen proglottids, of which the ante-
rior ones are very short, and do not show on the surface ;
these are preceded by an unsegmented area or neck, equal
in length to about the first half-dozen proglottids.

In compressed specimens, mounted entire, the delimita-
tion of the scolex is obscure (fig. 1), but in specimens floating
in spirit the anterior proglottids are frequently but not
invariably narrower than the hinder margin of the scolex
(fig. 2). This appears to be connected with the state of con-
traction of the parts concerned, for most specimens have
the shape shown in Plate 7, fig. 1. The proglottids do not
overlap one another to any noticeable degree.

Of the eighteen proglottids, the last alone contains ripe
eggs, with fully formed onchosphere in their envelopes. This
last proglottid readily falls off, so that in many instances no
complete eggs occur. In the four or five penultimate pro-
glottids the generative organs are more or less fully formed,
but the greater number show only traces of the gonads.

The isolated proglottids are usually U-shaped, and rather
larger than the terminal proglottid of the strobila (fig. 7) ;
but in other cases they agree in size. Frequently during the
process of mounting a strobila a proglottid would separate.
The peculiar form assumed by the isolated proglottid, brought
about by the unequal contraction of the muscles, seems to

TAPEWORM FROM APTERYX. 85

serve for the better dispersion of the ripe eggs contained
within. ‘The camera drawings (figs. 6 and 7) show the posi-
tion of these eggs in the terminal and in the isolated pro-
glottids. The spacious uterus occupies the anterior region
of the proglottid. After separation (or even before) the
circular muscles of the hinder margin contract more strongly
than elsewhere, so that this border is thrown into a curve ;
the anterior margin is thus spread out, and by contraction
of the longitudinal muscles the body-wall is drawn away
from the uterus, and during this process the thin walls of the
latter become ruptured, and thus the eggs are dispersed.
This seems to render improbable any prolonged independent
life of the proglottid (such as is recorded for those of Dav.
proglottina). The ripe eggs measure ‘03 mm. in diameter
over all, and possess two coats, an outer granular cellular
envelope, and an inner, firmer, thinner one, pressed against
which there appear to be flat nuclei (fig. 8).

The scolex, which is very much flattened from side to side,
is provided with the usual four suckers or acetabula hollowed
in the sides, and corresponding to the flat faces of the strobila
(fig. 4). Hach acetabulum presents the characters usual in
the family Teniade, but is rather oval than circular in
outline, and seems remarkable for the fact that its lower
posterior margin projects upwards and outwards as a kind of
flap, so that sometimes in mounted specimens, as well as in
unmounted ones, examined under spirit, the aperture appears
reduced, and may even be triangular in form (figs. 2 and 3).
From the various conditions here figured it seems certain
that this “flap” is moveable, the general effect being that
the aperture faces forwards instead of outwards.

The apex of the scolex is provided with an armed rostellum,
which bears a ring of eighteen or twenty small hooklets
arranged really in two circlets, but very close to one another,
so that the line of bases forms a zigzag (see figs. 5, 16, and
17), each of which is provided with a “handle” nearly as
long as the “blade,” while the “guard” is short but quite
distinct. The entire length of this hooklet is°04 mm. In

86 W. BLAXLAND BENHAM.

structure the rostellar apparatus agrees with that described
for T. undulata by Leuckart (see Bronn, p. 1827), but
differs in some details. It is described at the end of the
present paper.

As to the systematic position of this Cestode, I speak with
some diffidence, since I have no recent literature, beyond a
few manuscript notes on anatomical points, to aid me in the
determination. Bronn’s ‘Thierreich’ has not yet reached
the systematic account of the group. But the worm appears
to belong to Raillet’s genus Drepanidotenia—a charac-
teristic genus of avian parasites.

But the number of hooklets on the rostellum is greater
than in those species to which I can find reference ;* and,
moreover, they are in two closely placed circlets instead of
the “single circle” given as a character of the genus.
The hooks themselves are larger, and apparently the parts are
better marked than in other species.

It may be a representative of a distinct genus, but pro-
visionally I name the worm Drepanidotenia minuta, and
characterise it as follows :

A tetracotylean Cestode measuring about 1°5 mm., with
nearly parallel sides, consisting of a very few (about a dozen)
proglottids, of which the last alone contains ripe eggs. The
scolex is much flattened ; the suckers are provided with flaps
(or valves), so that the entrance appears reduced. The ros-
tellum is complex ; the hooks, in two closely set circlets, are
eighteen or twenty in number; each hook measures 0:04 mm.,
and has the usual parts well marked, the “handle” being
much longer than the “guard.” There is practically no
neck; the proglottids are short and wide; the genital pores
are alternate. The ripe eggs measure 0'03 mm. Hab., intes-
tine of Apteryx Bulleri.

Remarks.—The small size of the strobila and the fewness
of its proglottids render this worm rather remarkable, for it
is one of the smallest species of Cestodes. Amongst the
Tetracotylea (the family Tzeniade in the wide sense) there

1 Shipley, “On Drep. hemignathi,” ‘ Quart. Journ. Mier. Sci.,’ xl, p. 613.

TAPKWORM FROM APTERYX. 87

are 'T’. echinococcus, which reaches only a length of 5mm. ;
T. acanthorhyncha, Wedl, from Podiceps nigricollis,
and Davanica proglottina, Dav., from the fowl, which
does not exceed a millimetre in length: all these have but a
few proglottids. But from each the present species differs in
various ways. From D. proglottina, with which it has
some apparent affinity, it differs in that the suckers are not
provided with hooklets.

The peculiar flap to the sucker seems to be quite unique
amongst the family Tzeniade sensu lato; nevertheless it
faintly recalls the condition seen in the fish Cestodes, Pros-
thecocotyle Forsteri, Krefft, and Marsipocephalus
rectangulus, Wedl, both of which belong to the family
Tetrabothride (order Tetraphyllidea). From Bronn’s figures
it appears that in the former species there is a small muscular
wing arising from the outer margin of the sucker distally. It
is represented (Bronn, pl. xliv, fig. 2) as projecting into the
sucker. ‘lhe representation of the other species is not very
distinct (pl. xlv, fig. 15), but there appears to be a kind of
flap springing from the lower (distal) margin, as in the species
from Apteryx. As far as I can discover from all the general
literature, one of the characters of the Tzeniade sensu lato, is
that the hemispherical sucker has not projecting mobile mar-
gins. The two species herein described appear to contradict
this statement.

II. Drepanidotenia apterygis, n. sp.

The tapeworms from the intestine are altogether larger
than those in the duodenum, and are evidently a different
species.

They measure some 38 to 43 inches in length, and about
4 inch across the terminal proglottids ; the scolex, however,
is only about 4, inch across, so that the worm gradually
widens posteriorly (fig. 9). The strobila consists of some
300 proglottids, most of which (about 200) are of the same
short length, whilst beyond this point they become gradually

88 W. BLAXLAND BENHAM,

much longer. I killed the worms in various fluids ; those in
corrosive sublimate showed the last proglottids of about the
same length as breadth, whilst in glacial acetic acid they
shrank a great deal, and became shorter than broad. The
proglottids are a good deal imbricated, the hinder margin of
each covering nearly half the succeeding one (in the greater
part of the strobila) (fig. 13). The genital pores are alternate,
and the side that bears the pore is longer than the other, so
that each proglottid is somewhat wedge-shaped. (Here, too,
I note a difference in specimens killed differently. Those in
acetic acid show this character less than those in corrosive
sublimate.)

Here and there I noted half -proglottids intercalated
amongst the others. I believe this phenomenon has been
noted in the case of a species of Bothriocephalus from
Japan.

The eggs, which appear distributed over the entire ripe pro-
glottid, are provided with shells only in the last dozen
segments or so. Previous to that the blastomeres into which
the ovum has segmented are plainly visible, as they readily
take the stain; whereas, when once the shell is formed, the
stain does not penetrate (in entire worms).

The onchosphere (fig. 14) measures 0°03 mm. (this refers
to the diameter of the refringent shell only, and does not
include the granular envelope; the eggs, then, and the oncho-
sphere are larger than those of D. minuta), and their
hooklets 0:01 mm. in length.

The scolex is conical, with four large oval suckers, the
lower margins of which are often everted and prominent, and
appear, consequently, to be mobile. This lower lip does not,
however, rise upwards, as in the preceding Cestode, but the
cavity of the sucker is directed outwards.! The shape of the
suckers and general appearance of the scolex recall that of
certain Selachian Cestodes of the family Tetrabothridex ; but
the armed retractile rostellum, as well as other anatomical

1 T have a specimen of tapeworm with a similar scolex from a penguin, but
have not yet worked its character out. The shape is peculiar for a Tenia.

TAPEWORM FROM APTERYX. 89

characters, point to its affinities with the other avian Cestodes.
The rostellum, which, though constructed on the same plan,
is smaller than that of D. minuta (compare figs. 15 and 16,
which are magnified to the same extent), is armed with twelve
hooks, arranged in a single circle (fig. 10). Hach hook is
0:03 mm. long, and is thus smaller than in the preceding
worm. ‘The shape, too, is quite different, as the guard and
the handle are much smaller, the latter rather larger than
the former; it is, in fact, a typical Drepanidotzenian hook
Gigs tt).

The scolex is more nearly square in section than in D.
minuta; the suckers have the usual structure found in
Tenia (fig. 12).

This species is much more like a typical Drepanido-
tenia, except for the shape of the suckers (?), and agrees
with one species (not named by Shipley, but referred to) in
the alternate position of the genital pores.

It may be characterised thus:

Drepanidotenia apterygis, n. sp.

A Tetracotylean Cestode, measuring about 100 mm., with
some 300 proglottids, much broader at the free end than at
the scolex; the hindmost proglottids are as long as they are
broad. ‘The scolex, square in section, has oval suckers, with
posterior margin prominent; the rostellum is armed with
twelve hooklets in a single circle. Hach hooklet is 0:03 mm.
long ; the guard is about equal to the handle, but both are
short. The genital pores alternate; the eggs measure
0:03 mm. across the internal shell. Hab., intestine of
Apteryx Bulleri.

The Rostellum of Drepanidotenia.

The small size of D. minuta renders it a convenient
object for the study of the rostellar apparatus—its structure
and the mechanism of its movement—in specimens mounted
entire. From the following account it will be seen that it

90 W. BLAXLAND BENHAM.

agrees with the rostellum of certain other species of avian
Cestodes.

The rostellum in both the present species consists essen-
tially of two concentric muscular sacs, each filled with a fluid
(figs. 15, 16). The inner sac is the true rostellum ; the outer
sac is the “ receptaculum rostelli,” the wall of which is
reflected on to the rostellum over a certain area, so that the
latter may move in and out of the receptaculum.

The rostellum itself is more or less ovoid, but is divisible
into two unequal regions by a circular constriction or neck
near the distal end. The smaller of these regions is capable
of protrusion, and bears the crown of hooks; it may there-
fore be termed the “acanthophore” (figs. 16 et seq., b) ; the
proximal region is about twice the size of the acanthophore,
and owing to its function may be termed the reservoir (c).
The wall of this inner sac or rostellum consists of an outer
layer of longitudinal muscle, and below of circular muscle
(fig. 21, l.c.). The longitudinal muscles extend up to the
level of the insertion of the “ guard” of the hooklets; the
circular coat is distinguishable beyond this level, and ceases
at the distal limit of the “handles” of the hooklets (fig. 20).
This circular coat is much thicker at the neck than elsewhere,
and it is due to its presence here that the constriction is
so marked (figs. 16, 17).

The longitudinal coat is difficult to distinguish in flat
preparations of the entire object, but in transverse sections
is visible enough,

Just above the neck, but below the hooklets, is a series of
radial muscles, which in most preparations are seen to be in
two layers or strata, one above the other (figs. 16, 19, e).
These bundles of muscles arise from the wall of the sac, and
there are spots visible below the interspaces between the
hooks; consequently there are as many bundles of radial
muscles as there are hooklets (fig. 17, e). Possibly the
duplication of these muscles is in relation to the double
circlet of hooklets.

In the retracted condition of the rostellum these radial

TAPEWORM FROM APTERYX. 91

muscles have a horizontal direction, i.e. their axis is at right
angles to the long axis of the entire organ. But when the
rostellum is protruded they become vertically disposed
(figs. 18, 20).

For a long time I was unable to determine the mode of
insertion of these muscles, but in good longitudinal sections,
and even afterwards in old preparations, I was able to
recognise an extremely thin membrane (fig. 19, 7) that, in a
retracted state, is folded within the acanthophore.

In fact, the free distal extremity of the rostellum is in-
vaginated as a delicate membrane; and when the apparatus
is fully everted this membrane is forced outwards, and
assumes a convex form (fig. 20,7), taking with it, of course,
the insertions of the radial muscles.

It is very difficult to determine this invaginated membrane ;
for some time I believed that the terminal wall was double,
and that the membrane was capable of movement to and
fro, as implied by Studener (vide Bronn). I thought I could
detect the aperture of invagination at the apex, and then
again I could not make it out in the other case or in the
specimens mounted whole. But a comparison of a series of
camera outlines, representing every stage of protrusion, as
well as a renewed study of several states of protrusion,
showed that the circle of hooklets increased its diameter on
protrusion ; and I feel confident that the explanation of this
hes in the facts above recorded.

Neither this membrane nor the muscles are directly con-
nected with the hooklets.

The cavity of the rostellum, or, to be more particular, of
the reservoir, is occupied by a granular material, in which
numerous nuclei are recognisable, but without cell outlines
(figs. 16, 19, 20, ¢). In certain preparations a fibrillation of
this material is apparent; these fibrille, however, are not
muscular ; they react to stains quite differently, and do not
stain at all; I am inclined to think that they are due partly
to the arrangement of granules in rows, and possibly to some
coagulation effect. This granular material is very compress-

92 W. BLAXLAND BENHAM.

ible, and may be regarded as fluid ; for on the contraction
of the wall of the reservoir it is driven forwards so as to
distend the acanthophore, pushing forwards the radial muscle
and the membranous anterior wall of the acanthophore.

Turning now to the receptaculum rostelli, it has similarly a
wall of two layers of muscles, complete posteriorly, but
reflected distally (anteriorly), so as to be continuous with the
wall of the rostellum at the neck.

The contents of the receptacle in D. minuta is of two
kinds. In the distal region is a very faintly granular fluid
(not taking the stains) with scattered nuclei, without evident
arrangement or cell boundaries (fig. 19, p). But the bottom
of the receptaculum is occupied by a very deeply staining
granular mass, so deeply staining in boracic carmine as to
hide the nuclei which are scattered therein; but in hema-
toxylin the nuclei stain more deeply. This mass is contained
in four elongated sacs (figs. 16—22, s), the membranous walls
of which meet below the bottom of the rostellum, so as to
form an X-shaped septum in transverse section, and a longi-
tudinal one when seen in longitudinal section (as noted by
y. Linstow in 1890). These granule sacs fill the post-rostellar
region of the receptaculum, and push forwards about halfway
along the latter, where they end by obliquely tapering off, so
that the less granular material distally intervenes between
them and rostellum (figs. 1, 9). The receptaculum is moved
by extrinsic muscles, some of which pass upwards and out-
wards from the wall, near its anterior end, diverging in a
fan-like manner, to be inserted in the apex of the scolex
above the suckers (fig. 16, m’).

These muscles seem to be in four groups or bundles, two
on each side of the receptaculum, lying between it and the
chief nerves issuing from the brain. Other muscles pass
downwards and are lost behind the suckers (m). But it does
not seem that these extrinsic muscles play any great part in
the protrusion of the actual rostellam. In this process we
have to distinguish two independent movements; firstly, the
protrusion of the rostellum; and secondly, the distension or

TAPEWORM FROM APTERYX. 93

erection of the acanthophore (see the series of figures, 16
—18). The first movement is effected by the contraction
of the walls of the receptaculum rostelli. The fluid contents
are merely compressed, and force the rostellum forwards,
the acanthophore being thus protruded from the receptaculum
(fig. 17), and ultimately through the aperture at the true apex
of the scolex (fig. 18).

The distension of the acanthophore is effected by the con-
traction of the wall of the rostellar sac, the reservoir. This
drives the fluid contents (¢.) forwards, distending the acan-
thophore and pushing forwards the membrane, so that a
more or less spherical ball is formed, the wall of which is
tensely stretched (figs. 19, 20). The radial muscles now
come into action. Hitherto, as the various figures show,
they have been horizontal, but as the membrane to which
they are inserted is pushed outwards they take on the vertical
position, and are considerably stretched.

During this process of protrusion the points of the hooks
are kept pressed down against the side of the acanthophore,
but now by the contraction of the radial muscles it appears
that the terminal membrane, and therefore the “ guard,” is
pulled downwards, and consequently the point is caused to
diverge.

This type of rostelluam—with two concentric muscular sacs
—has been described by Leuckart, von Linstow, and others
for certain species, e.g. “Tenia” undulata, T. puncta,
T. serpentulus,—all avian Cestodes ; and it differs from
the apparatus in mammalian Cestodes, e. g. T’. crassicollis,
which is a solid mass of muscles, having various directions.
I believe, however, that I have been able to add some details
in regard to it and to clear up some points that were doubtful,

and I have thought it worth while to give the series of
figures representing accurately the relations of the various
parts during its movement, as I know of no such series having
been hitherto published.

Dunepin ; May 11 th, 1899.

94. W. BLAXLAND BENHAM.

DESCRIPTION OF PLATES 7 & 8,

Illustrating Mr. W. Blaxland Benham’s paper on “The
Structure of the Rostellum in two New Species of Tape-
worm, from Apteryx.”

Drepanidotenia minuta, n. sp.

Fic. 1.—The entire strobila, stained and mounted as a transparent object.
x 30. (Camera.)

Fic. 2.—The “scolex,” seen as an opaque object, in alcohol, uncompressed,
showing the flaps of the suckers more plainly than in the compressed
specimen.

Fic. 3.—Three different suckers, showing mobility of the flap or anterior
margin of the sucker; the muscle-fibres of the margin are seen to be continued
on to this apparent flap.

Fic. 4.—A transverse section through the scolex. x 46. (Camera.)
A. rostellum, 7. receptaculum rostelli.

Fic. 5.—One of the rostellar hooks; a. blade, d. handle, c. guard. x 625.
(Camera.)

Fic. 6.—Outline of the terminal proglottid of a strobila from a horizontal
(though somewhat oblique) section ; e. eggs, p. coiled penis, 0. genital pore.

Fie. 7.—Outline of isolated detached proglottid: the margins a. 8. corre-
spond with those in Fig. 8.

Fic. 8.—Onchosphere in its envelopes.

Drep. apterygis, n. sp.

Fic. 9.—The entire strobila, natural size.

Fic. 94.—Scolex; freehand.

Fie. 10.—Apex of scolex, with protruded rostellum.

Fie. 11.—A rostellar hooklet, a. blade, 6. handle, c. guard.

Fie. 12.—Transverse section of scolex. x 150. (Camera.) r. recepta-
culum rostelli, 2. aperture of excretory tubule.

Fie. 13.—A portion of the strobila, mounted, entire, transparent, somewhere
near the middle. x 78, (Camera.) It happens that, of the five proglottids
figured, four have the genital pore on the same side; in other regions the
alternation of the pores is more regular. o. genital pore, p. everted penis,

TAPEWORM FROM APERTYX. 95

z. longitudinal excretory canal. The imbrication of the proglottids is well
seen.

Fic. 14.—An onchosphere enclosed within its coats.

Fie. 15.—The apex of the scolex, showing the retracted rostellar apparatus;
in optical section, from a transparent specimen. Xx 375. (Camera.) a. the
apical pore, R. rostellum, 7. receptaculum rostelli, s. sucker. Compare the
size with that of the apparatus of D. minuta (fig. 10).

The Rostellum of Drepanidotenia minuta.

Fics. 16—18 are optical sections, from stained, transparent, entire stro-
bilas. All are drawn with the camera, under the same magnification.
x 375.

Fig. 16.—The rostellum entirely withdrawn into the receptaculum. a.
Apical pore in the scolex. 34. Acanthophore. e¢. Reservoir of rostel-
lum. d. The circular muscles of its wall (the longitudinal only
shown at the base). e¢. The radial muscles. m’,m''. The extrinsic
muscles that move the receptaculum. p. Finely granular contents of
the anterior region of the receptacle. 7. The muscular wall of the
receptacle. §. Outline of sucker. s. Coarsely granular contents of
the posterior region of the receptacle contained in membranous sacs.
w. The septum formed by apposition of these sacs.

Fig. 17.—The rostellum at the commencement of protrusion. The
acanthophore is moving upwards in the pre-rostellar canal. The
reservoir is greatly constricted by the circular muscles at the neck
and elsewhere; the radial muscles (¢.) are still horizontal. This pro-
trusion is effected by the contraction of the wall of the receptaculum ;
the “septum” (w.) between the membranous sacs is now longer, and
the sacs lie nearly entirely behind the rostellum. y. is a sphincter
muscle closing the lower aperture of the pre-rostellar canal. ‘The
radial muscles, as well as other details, show better in this preparation,
which was stained in alum-cochineal (Czokor). The radials are appa-
rently interrupted by vertical lines; as a fact, there are eighteen groups
of radial muscles.

Fig. 18.—-The rostellum is protruded, though not to its fullest extent.
The acanthophore not only projects through the aperture (a), but is
distended by the fluid contents of the reservoir, forced upwards by the
contraction of its wall. The longitudinal muscles are here shown.
The apex of the acanthophore is depressed (4’), and between the hooks
the “radial muscles” (e) are seen to be vertically disposed.

Fies. 19 and 20 are longitudinal sections x 450. Outlines and main
details with camera.

96 W. BLAXLAND BENHAM.

Fig. 19.—The rostellum in the same stage as in Fig. 18—at the com-
mencement of protrusion. The distal wall of the acanthophore is seen
to be invaginated as a thin membrane (j), to which the radial muscles
(e) are inserted. The longitudinal and circular muscles of the rostellar
wall are shown (JZ. C.), the latter extending up to the upper insertion
limit of the hooks. The granular contents (¢) are represented with
the greatest care. They show granulation and fibrillation and nuclei,
and are seen to be confined to the reservoir. The details of the recep-
taculum are also faithfully represented; the contents of the mem-
branous sacs (s) appear to coagulate or shrink, leaving a space, so that
the cells appear to form an epithelium.

Fig. 20.—The rostellum only is shown in a fully protruded condition.
The section is not quite median so far as the acanthophore is con-
cerned, hence the distance between the hooklets is not as great as
it would be if the hooklets were at the ends of a diameter. The
reservoir is strongly contracted, so that the contents (¢.) have been
entirely forced against the ‘radial muscle ” (e.), and thus distend the
acanthophore. The radial muscles are practically vertical (cf. Fig. 19),
and the invaginated membrane (j.) into which they are inserted is
pushed forwards so as to become convex. The contraction of these
muscles in this condition, when their area of insertion (j.) is rendered
tense, raises the points of the hooklets so as to effect attachment to
the wall of the gut.

Fie. 21.—Transverse section through the rostellar apparatus about the
middle of its length. 2. Rostellum. 7. Receptaculum rostelli. JZ. 2.
Longitudinal musculature. CC. c. Circular muscular of each. The rostellum
is seen to be filled with finely granular material, in which are nuclei. 2.
Nuclei. The coarsely granular contents of the receptaculum are contained
in four saes (s.), the walls of which meet to form four septa (w).

Fie. 22.—A transverse section of the receptaculum below the rostellum.
Letters as before.

HABITS, ETC., OF CEREBRATULUS LACTEUS. oF

The Habits and Early Development of Cere-
bratulus Lacteus (Verrill).

A Contribution to Physiological Morphology,

By
Chas. B. Wilson.

With Plates 9—11.

OUTLINE.
I. IntRoDUCTION . - ; : 5 Oe 5s
Il. Tor Apyitt Worm.
a. Determination of Species 2 : : . 102
B. Habitat and Habits:
(1) Geographical distribution . ‘ 5 . 103
(2) Burrows and burrowing . F : . 104
(3) Food . ‘ ; : . : LO
(4) Breathing . : ; : : ~ £09
(5) Locomotion . : : : : LO
(6) Dismemberment : : ; : ~ Ai
(7) Regeneration . , : : . 2 PS
IIT. Larvat DEVELOPMENT.
A. Sexual Organs:
(1) The ovaries :
(a) Germ tissue. : , : ower
(4) Odgenesis : : : : eles
(ec) Formation of oviduct . : - 125
(2) The testes:
(a) Sperm tissue . : ; : . 126
(4) Spermatogenesis ‘ : : « 126
(c) Formation of sperm-duct : : > 127
B. Egg-laying F : : ‘ . 12s
c. Fertilisation and Pomorie 2
(1) Fertilisation . : : 5 . 130
(2) Formation of polar pois é : ; elcal
(3) Activities of polar bodies :
(a) Description of activities ‘ ; . 138
(4) Connection with egg . . : » db
(c) Polarisation . : : : . 135

VoL. 43, PART 1.—NEW SERIES. G

98 CHAS. B. WILSON.

(d) Summary
(e) Conclusions
Dp. Segmentation:
(1) Mode of cleavage
(2) Behaviour of polar bodies
(3) Filose activities
(4) Contractile movements
(5) Separation of blastomeres
(6) Blastula
(7) Summary
(8) Conclusions
E. Gastrulation:
(1) Ciliation of the larva.
(2) Formation of gastrula
(3) The apical plate
(4) Change from radial to bilateral Sranetry
(5) Escape from egg-membrane
IV. Tue Prurpiom.
a. Habits:
(1) Locomotion ‘
(2) Use of apical flagella.
(3) Food . :
B. Morphology:
(1) External morphology .
(2) The primitive intestine
c. Mesoderm Formations:
(1) Origin of mesenchyme cells .
(2) Their contractility :
(3) Development of the larval muscles :
(a) Apical muscles
(4) Interparietal muscles .
(c) Gisophageal muscles
(d) Circumoral muscles
(e) Parietal muscles
(/) Lappet muscles
(4) Summary
(5) Conclusions
vp. Histology:
(1) The epidermis
(2) The apical plate
(3) The cilia rows
(4) The intestinal canal
(5) Summary

138
138

141
141
144
145
149
149
149
151

153
154
155
156
158

159
159
161

162
162

164
165

166
167
168
169
170
171
174
175

181
182
185
188
189

HABITS, ETC., OF CEREBRATULUS LACTEUS. 99

INTRODUCTORY.

Tue ontogeny of the Nemerteans, and more particularly
that of the Schizo-nemerteans, is of special interest on
account of the metamorphoses through which the young
embryos pass.

Ever since its discovery and naming by Miller in 1847
(38) the pilidium form of larva has attracted the attention of
leading scientists the world over. Asa result of their inves-
tigations we are to-day in possession of the leading facts
with reference to the histology of the pilidium and the meta-
morphoses from this free-swimming form into that of the
adult worm.

Much work has also been done upon the origin and matura-
tion of the sexual products in different species. But our
knowledge of fertilisation, segmentation, and the early
history of the pilidium has been derived almost wholly from
two papers by Metschnikoff, one in 1870 (385) and another in
1882 (36).

The former paper I have been unable to examine, but from
the excellent abstract given by Biirger (13) I judge that
Metschnikoff obtained the eggs already fertilised, and fol-
lowed their subsequent development as closely as possible.

At all events he confines his attention in both papers
almost exclusively to the later development of the larva, and
seems to have derived his facts from observation of histolo-
gical material, and not from a study of the living embryo.

1 Since the above was written it has been my pleasure to receive from the
author, Dr. W. R. Coe, of the Sheffield Biological Laboratory of Yale
University, a copy of his excellent paper upon “ The Maturation and Fertili-
sation of the Egg of Cerebratulus” (16). This is the first step toward
supplementing our knowledge of this long neglected group and is most
praiseworthy.

100 CHAS. B. WILSON.

In the present investigations for the first time, so far as
can be determined, the eggs of a Nemertean were fertilised
artificially.

The consequent abundance of embryos has rendered it
possible to follow in detail every step in their development,
and to use living material far more than has ever been done
heretofore.

In much of the recent embryological work there has been
a tendency to confine the attention almost exclusively to the
study of sections and prepared material. And embryos have
been reared for the sole purpose of furnishing such material.
But it is clearly evident that the true purpose of histology
is to supplement, and not to supplant, the study of the
living animal. For this reason the morphological drawings
in the present paper have been made, whenever it was
possible, from living specimens, with the aid of the camera
lucida.

Adults have also been captured and kept in aquaria where
their habits could be closely watched, and many interesting
facts have been thus discovered. Eggs have been laid and
fertilised by individuals thus kept in confinement, so that it
has been possible to verify all the details obtained from the
artificially fertilised eggs, and, in addition, to discover the
method of egg-laying and fertilisation.

The development and habits of the pilidium have been
carefully watched for four successive summers, and as a
result it is possible to present quite a full account of this
particular species. A second result has been the growing
conclusion that this species is particularly fitted for embryo-
logical work in our laboratories. Many different reasons
have led to this conclusion, among which may be mentioned:

1. The vitality of the adults, by reason of which uninjured
sexual products can be obtained from them even under very
adverse circumstances. When reduced to such a dire neces-
sity, a single piece of a disruptured worm, but a few inches
in length, can be used at the rate of half an inch a day for a
week or more, and it will yield all the while germinal pro-

HABITS, ETC., OF CEREBRATULUS LACTEUS. 101

ducts capable of producing normal embryos. A clean glass
vessel (4 to 6 gals.) with plenty of the sand or mud from
which the animals were taken, and a constant but slow
renewal of the water, has proved to be the best aquarium.
Only one pair of worms should be placed in a single vessel,
and the supply of plant life should be very meagre. Under
these conditions no difficulty has been experienced in keeping
the worms for six or eight weeks, and they have laid pro-
fusely (cf. Coe, 15).

2. The ease and uniformity with which the egg may be
fertilised artificially.

3. The persistence and remarkable activity of the
polar bodies. They remain in close connection with the egg
all through segmentation and gastrulation, the second body
being actually connected with the blastomeres by protoplas-
mic processes, while both display to a marked degree those
protoplasmic activities which have been designated as
* spinning.”

4, The transparency of the larva subsequent to gastru-
lation, which renders it very easy to follow its internal
development. It is so clear that very high powers may be
successfully used. An excellent opportunity is thus afforded
for the study of muscular development, owing to the peculiar
nature of the mesenchyme cells.

Every fact of importance has been included in the present
paper; when not verified by personal observation, due ac-
knowledgment has been made. The author desires to
express his indebtedness to Librarian Wm. I. Fletcher, of
Amherst College, for the free use of the science library of
that institution, without the help of which the present work
would have been impossible. It is likewise a pleasure to
acknowledge the inspiration and the many valuable sugges-
tions given by Dr. H. A. Andrews, of Johns Hopkins Uni-
versity, and by Mrs.G. F. Andrews. And to Dr. W. R. Coe,
of the Sheffield Biological Laboratory, acknowledgment is
due for the kindly loan of mounted material illustrative of
spermatogenesis, and for much friendly criticism.

LOZs * CHAS. B. WILSON.

Toe ApuLtt Worm.
Determination of Species.

The species under consideration is one of the largest of
the Nemerteans, and possesses all the characteristics of the
group. These consist negatively in the absence of all external
appendages and of a definite body-cavity, and the entire lack
of visible segmentation. Positively they include the posses-
sion of a smooth body, flattened dorso-ventrally, and of a
very long tubular proboscis, which can be protruded by
eversion from an aperture in the front of the head.

Much work has been done upon the classification of the
Nemerteans with no decisive results. Different species and
even genera frequently resemble one another so closely that
they cannot be distinguished after preservation. Hence we
can find in the attitude of different authors every variation
from one (46) 75 per cent. of whose enumerated species are
new creations, to another (27) who would include all the
Schizo-nemerteans under a single genus. And our present
species is classified by different authors under distinct names
and even under different genera. The name we have chosen
is the one selected by Verrill, but the same species was called
by Girard Meckelia fragilis, by Leidy Meckelia ingens,
though at first he designated it M. lactea. The name of
the group, Nemerteans, was first applied by Cuvier, and is
derived from Nemertes, one of the Mediterranean sea-nymphs,
daughters of Nereus and Doris.

The generic name, Cerebratulus, was first given by
Renier in 1804 to a single species, and continued until re-
cently to be simply a specific name. It is derived from
cerebrum, the brain, probably from a fancied resemblance
of the tissues (41).

The specific name, lacteus, was given by Leidy to cer-
tain small white specimens, which afterwards proved to be
the young of this species, and accordingly the name was

HABITS, ETC., OF CEREBRATULUS LACTEUS. 103

extended by Verrill, in 1892, to include the larger adults
which are often not at all “milky” (46).

Habitat and Habits.

This large Nemertean is quite common along the entire
Atlantic coast, from Florida to Massachusetts Bay, and is
found locally at Casco Bay on the coast of Maine. From
this latter locality were obtained all the specimens which
furnished data for the present paper. Verrill states (46)
that he found adults at Quohog Bay, one of the numerous
inlets of Casco Bay. These were associated with a number
of other southern forms, such as Venus mercenaria,
Crepidula convexa, Hupagurus longicarpus, Gam-
marus mucronatus, Nereis libata, Meckelia ingens,
Asterias arenicola, etc. These species properly belong
to the region south of Cape Cod, and it might be inferred
that Cerebratulus also was a southern species, and that it
could be found in northern waters only under specially
favourable conditions.

Such, however, is not the case; I obtained a number of
specimens from Quohog Bay, but found them more abundant
at Stover’s Point on the east side of Harpswell Neck. All
the specimens used were obtained here, but none of the
southern species named above were found anywhere in the
vicinity. Furthermore, the Point is only about a mile from the
end of the Neck, and it gets the full sweep of the tide from
the open ocean twice a day.

The largest colony of Nemerteans was on the outer or
exposed side of the Point, and was associated exclusively
with hardy northern species. The fishermen often find these
worms when digging for clams during the winter, and some
of the material used for the origin of the sexual products was
obtained from them at that season. When we reflect on the
severity of the winter upon the Maine coast, where the mud
is exposed between tides to an atmosphere that frequently

104 CHAS. B. WILSON.

registers many degrees below zero, we may conclude that
Cerebratulus has at least become well acclimated.

This species burrows in sand and mud between tides, and
in shallow water down to several fathoms in depth.

It occurs most plentifully at and just above low-water
mark, but may be found inder stones in sheltered positions
(Quohog Bay), nearly up to the high-water mark of medium
tides. It is gregarious in habits, and the finding of one is a
good indication that there are others in the immediate
vicinity. It also occurs in the same localities year after
year, but after prolonged search in any one place the number
of large specimens becomes very sensibly diminished. The
largest specimens are not solitary, as McIntosh declares to be
the case with the great Lineus marinus (84), but they are
so limited in numbers as to warrant the conclusion that here,
as in some of the higher forms of life, size is ‘inimical to
profusion.” One of its favourite haunts is along the edges of
an old mussel-bed amidst the broken shells and stones, into
which it is often almost impossible to drive a clam-hoe. But
it is also dug up with clams in clean white sand and mud, and
is known locally to the fishermen as a “ clam-worm.”

Scarcely a trace of the worms save the entrance to their
burrows can be seen except at high tide. This is their
period of activity, and they may then occasionally be ob-
served gliding amongst the sea-weed on a muddy or sandy
shore, or in the shade of the rocks in a large tide-pool. They
are essentially nocturnal, and come out of their burrows much
more frequently during the night tides than during those
which occur in the day time. The burrow itself is little more
than a hole or tubular opening through which the worm can
move freely in either direction. The walls of this tube are
coated thickly with the slimy mucus exuded from the worm’s
skin, which materially facilitates its progress.

The burrows are neither very long nor very deep, for even
the largest worms are found within a few (six or eight) inches
of the surface. There is no evidence to show that the same
burrow is inhabited for any length of time. On the contrary,

HABITS, ETC., OF CEREBRATULUS LACTEUS. 105

all observations indicate that the worm roams about con-
stantly in the mud after food, and that it is able to move
quite rapidly, even when forming a new burrow. ‘The enor-
mous amount of slime secreted by the worm’s ectoderm may
be inferred from the fact that it eevee the walls of its burrow
constantly coated.

This slime often oxidises the iron elements in the mud, with
the result that the latter is tinged a dull rusty red in the im-
mediate vicinity of the burrow.

Repeated attempts were made to ascertain just how the
burrowing was done, by digging out specimens and throwing
them on a fresh surface. It was noticed that the worm
thrust its pointed head a little way into the mud and then
seemed to brace itself for a further effort, the head at the
same time being withdrawn slightly. The significance of
this fact was in doubt for some time, but on placing a few
worms in a glass aquarium with five or six inches of mud at
the bottom, they immediately began to burrow near the glass.
It was then seen that the bracing action was due to the fact
that the worm was driving its proboscis into the mud ahead
of itself. The proboscis was protruded for six or eight inches,
and then enlarged slightly and crooked a little at the end.
Aided by the hold thus obtained the worm was able to thrust
its head rapidly into the mud, keeping it narrow and pointed
the while.

The extreme tip of the head was then contracted into a
broad rounded form, and the wave of contraction thus started
passed slowly backward along the anterior portion of the
body, thereby moving the latter forward about aninch. As
soon as this wave was fairly started in its backward motion
the head became pointed, the proboscis was thrust forward
again, and the whole process was repeated. The tip of the
head was then contracted, and a second wave was started
backward before the first had reached the centre of the body.
In this way one wave followed another so quickly that the
resultant motion was nearly a steady advance instead of being
jerky. This rapid burrowing by means of both proboscis and

106 CHAS. B. WILSON.

body contractions must be of great service to the worm in
escaping from its enemies and in obtaining its food. In
locomotion the proboscis seems to be of use chiefly as an
organ of feeling or touch, being thrust forward to determine
the direction in which the burrow is to be made. Whenever
it strikes an obstacle, such as a small stone, it feels around
it, sometimes on several sides, and selects apparently the
place that offers least resistance.

In doing this it often happens that the proboscis will be
thrust up into the water. It is then quickly withdrawn only
to be thrust up again, perhaps in a very few seconds.

The only idea of direction, therefore, seems to be to keep
beneath the surface of the mud. It is also evident that when
the proboscis is thrust forward forcibly into the mud or
sand, it makes an opening for the subsequent passage of the
head.

The worm may often be seen to withdraw its proboscis
and push its head along in the opening thus left. It is also
possible that the proboscis may have some tractile power in
helping to pull the body forward. That it is actually used
as an organ of prehension was witnessed several times.

The Nemerteans were fed with common clam-worms (Ne-
reis). When a Nereis in wriggling about came in contact
with a Nemertean, or crossed the mouth of a burrow when a
Nemertean was inside, the latter suddenly darted out its
proboscis and coiled it spirally around the Nereis. The spiral
coil covered an inch or more of the Nereis’s body, and the
proboscis was then slowly withdrawn, bringing the Nereis
up to the Nemertean’s mouth, where it was finally swallowed.
This corresponds exactly with the graphic description given
by Kingsley (cf. 34) of a specimen of the species Polia
mandilla (Amphiporus lactifloreus, McIntosh) in the
act of devouring a fish. McIntosh, however, questioned
Kingsley’s accuracy (84), because the latter says that the
proboscis assists in prehension, but Cerebratulus certainly
uses it sometimes for that purpose.

When withdrawn the proboscis is coiled up in that portion

HABITS, ETC., OF CEREBRATULUS LACTEUS. 107

of the sheath which lies above the cesophagus, as can be seen
in fig. 4.

Its large anterior end is continuous with the walls of the
sheath just in front of the ganglionic commissure, while its
small posterior end is fastened at a single point where the
cesophagus joins the intestine. As the proboscis itself is
several times the length between these two points of attach-
ment it is coiled very closely. Furthermore, being attached
at the posterior end, it follows that it must always be of
double thickness, with a blunt anterior end when everted.
This increases its strength for prehension and burrowing,
and does not seem to detract from its delicacy as an organ
of touch.

Food.—tThis species of Cerebratulus is almost wholly car-
nivorous, and feeds upon other worms which frequent the
mud between tides, showing a decided preference for Nereis.

Several times both Nereis and Nemerteans were placed
in the same dish when obtained; the former were found
to have been swallowed by the latter on reaching the labora-
tory half an hour later. The Nereis is always swallowed
tail first (fig. 1), which is exactly the opposite of the method
usually followed by carnivorous animals, but is occasionally
found in other carnivora, as when a snake swallows a frog
or toad (28).

In such cases the animal swallowed is usually defenceless,
while its captor is well armed, but in the present instance
these conditions are exactly reversed. And it is very hard
to understand how a Nemertean, which has neither teeth nor
jaws, nor indeed offensive weapons of any kind, can yet over-
come a well-armed Annelid nearly as large as itself. The
head of the Nereis, with its powerful jaws, is left entirely
free, but although I have seen the victim wriggle frantically
in its efforts to escape, until it finally disappeared down its
captor’s throat, it never made any attempt to bite. This is
the more remarkable in view of the well-known fact that when
two Nereis come together they almost invariably fall upon
each other tooth and claw, and often inflict very severe

108 CHAS. B. WILSON.

wounds with their powerful jaws. Dr. E. A. Andrews has
suggested to me that possibly the dense coating of slime
which is constantly exuded from the Nemertean’s ectoderm
may afford it protection. Ifa minute drop of this slime be
placed upon the tongue it will be found so intensely acrid
as to parch the whole mouth, and the taste remains for a long
time. This quality, then, might effectually prevent the
Nereis from inflicting any injury with its jaws. ‘These
Annelids do not often leave their burrows altogether, but
simply protrude the head and anterior portion of the body in
search of prey. ‘Taken in connection with the fact that the
Nemertean swallows them tail first, this suggests that they
are not ordinarily caught outside their burrows, but that the
Nemertean probes around beneath the surface until it strikes
the home of an Annelid, and then proceeds to swallow the
unfortunate occupant. In such a case the Annelid’s jaws
would be practically useless, for it could not turn about in its
burrow. The snout. of the Nemertean, in front of the
mouth, is usually turned backward during the process of
swallowing, the proboscis being wholly withdrawn.

The digestive fluid acts very quickly. Several attempts
were made to preserve a specimen with a Nereis nearly
swallowed and protruding an inch or two from its mouth.
But they failed at first because the Nereis was forcibly
ejected as soon as the Nemertean touched the preserving
fluid, no matter how far it had been swallowed. A subse-
quent attempt was crowned with success; a Nemertean with
an inch of Nereis nearly as large as itself protruding from
its mouth was plunged into boiling water for a moment
and then preserved in formalin. ‘This produced death so
instantaneously that there was no time for ejection, and
the perfectly preserved pair still remain to attest the fact
(fig. 1).

But although the first efforts were failures in one direction
they were a success in another. The swallowing of an
ordinary Nereis occupies about ten minutes, but in every
instance it was found more than half digested upon ejection,

HABITS, HTC., OF CEREBRATULUS LACTEUS. 109

The same thing happened when a dead squid was left in a
pail with some Nemerteans. One of them swallowed a long
arm of the squid, and when its further progress was stopped
at the base of the arm it drew its body down in wrinkles
until as much of the digestive tube as possible had come in
contact with the arm. It remained in this position for five
or six minutes and then withdrew, leaving the arm com-
pletely digested for more than half its length. Of course,
there is very little substance to the body of a Nereis, and it
can be assimilated without much change; but the arm of a
squid is more substantial, and must require considerable
digestion. It is evident that this takes place rapidly at the
very beginning of the alimentary canal. This fact suggests
one reason why the loss of the posterior portion of the body
does not seriously affect the animal.

Several of the fishermen have told me that specimens of
Cerebratulus are sometimes caught by them when fishing in
shallow water with a bait of Buccinum undatum or
Natica heros.

The same thing is noted by McIntosh (84) with reference
to the deep-sea form, Lineus marinus, which was caught
while fishing for cod. Like that species, Cerebratulus also
must have “an indiscriminate appetite,” feeding upon both
living and dead forms, and ejecting the bristles and other
indigestible material through the anus. Occasionally a
bristled or spiny victim proves too much for its captor, with
the result that the bristles or spines perforate the digestive
tract and the body-wall.

Dr. W. R. Coe tells me that he found a Cerebratulus in
this condition with a large Nereis half swallowed, the poste-
terior portion of the Nereis protruding through a large rent
in the ventral wall of the cesophagus. In confinement Cere-
bratulus eats readily almost any animal food, but prefers a
Nereis to anything else.

Breathing.—This species and probably most other Ne-
merteans breathe by means of the walls of the cesophagus.

With the incoming tide the Nemertean opens the anterior

110 CHAS. B. WILSON.

end of its burrow by turning it abruptly upward to the sur-
face, and then lies with its head in the lower part of this
vertical portion. The burrow around the head and in the
immediate vicinity is enlarged somewhat, so that the water
can circulate freely, and by alternately swallowing and eject-
ing mouthfuls of water the Nemertean generates a very per-
ceptible current.

The swallowing is long and slow, while the ejection is
short and abrupt, the two together occupying about ten
seconds. This is evidently the Nemertean’s mode of breath-
ing, and the purification of the blood must take place in the
walls of the cesophagus, as we should naturally infer from
the arrangement of the circulatory system. These facts, of
course, were chiefly gathered from specimens kept in an
aquarium where the supply of water was constant, but it was
curious to note that they alternated periods of rest with
periods of breathing exactly as if they had been subject to
the flow of the tide. And their periods of rest usually,
though not always, corresponded closely with those of the
ebb tide.

During the breathing the cephalic slits along the sides of
the head were occasionally, though not regularly, opened
and closed. At such times, of course, a current of water
would enter the side-organs, and it is possible that they
assist somewhat in the purification of the blood. But from
the regularity of movement in the cesophagus and the entire
lack of it in the cephalic slits, we must conclude that the
former constitutes the true respiration.

Locomotion.—The mode of locomotion by means of
which the Nemertean moves through its burrow has already
been described.

They also come out of their burrows at times and swim
about in the water. Verrill states (46) that “while swim-
ming the body is turned up edgewise and thrown into many
undulations, and the motion resembles that of an eel, but is
less rapid.” Coe adds (15) that “it is often met with at
night swimming near the surface of the water.” This is a

HABITS, ETC., OF CEREBRATULUS LACTEUS. 11]

well-known habit of all species, the lateral margins of whose
bodies are produced into a thin edge throughout the greater
part of their length. But although I have been out at night
repeatedly and towed over localities where the worms were
abundant, I have never been fortunate enough to catch one
swimming.

Frequently, however, some that were dug out of the sand
were thrown into the water and watched swimming about,
and others have often been seen swimming in the aquarium.
Under such circumstances the Nemertean does not turn up
edgewise, but undulates about in every possible position, the
body being now dorsal side up, now ventral, now with the
right side uppermost, now the left, the change from one
position to another being continuous though slow. It would
seem probable that they come out of their burrows and swim
about most frequently during the breeding season, although
eges are laid inside the burrows, as we shall see later.

In addition to swimming and crawling through their
burrows these Nemerteans are also capable of moving along
on the bottom over the mud or stones quite rapidly, and yet
as they have no sete like the earthworm, norany other means
to prevent slipping, and as the surface of their body is
slimy, there is always a considerable loss of motion. Ona
solid surface the mode of progression is by crawling in a
manner similar to that of a Gastropod, with the exception
that the waves of muscular contraction, passing backward
from the head, are much more apparent.

But this is true only of the adults; young individuals can
glide over the glass sides of an aquarium so smoothly that
their bodies show scarcely a wrinkle (cf. 34).

The Nemertean also leaves a track of mucus, like the Gas-
tropod. This mucus is exuded even when the animals are
lying coiled up at rest, and it is so abundant that a pail con-
taining several fresh vigorous worms is soon filled with a
perfect meshwork of mucus, from which the worms must be
pulled or cut out. And it acquires sufficient consistency to
offer considerable resistance. If it be removed it is quickly

112 CHAS. B. WILSON.

formed again, but several removals produce a marked dimi-
nution in the amount secreted. This abundance of mucus
gives some of the smaller forms the ability to crawl back
downward on the surface of the water, after the manner
of nudibranchs, the mucus forming a sort of float, and being
firm enough to give the animal a purchase for its muscles.
McIntosh states (34) that “if a Nemertean is raised from
the surface on which it crawls it always clings most perti-
naceously by the anterior end ; indeed it would appear that
the lips exercise a kind of sucker-like action, or at least that
the flattened under-surface of the snout does so.”

I have never been able to verify this observation on Cere-
bratulus, for I could not see that one portion clung to the
supporting surface any more than another. But the head
and anterior cesophagus are usually kept in contact with the
surface, while the other portions of the body are often
removed temporarily.

Dismemberment.—Almost every scientist who has dealt
with the Nemerteans has noted their disagreeable habit of
dismembering themselves when irritated. But even the
specialists have not gone beyond a mere statement of the
fact except in one or two instances, while the best and
most recent monograph on the Nemerteans, that published
by Birger as the 22nd volume of the ‘ Fauna and Flora
of the Gulf of Naples,’ does not even mention the habit
at all.

We are informed that we must secure our specimens very
quickly, and kill them in something that produces instan-
taneous death if we expect to obtain anything more than a
handful of fragments for our pains; but we are left to answer
for ourselves the many interesting questions that are sure to
arise. Do the Nemerteans ever fragment without irritation?
If so, under what conditions and what advantage is it to the
worm ?

After fission can both anterior and posterior fragments re-
generate, the one a new body and the other a new head ?

In answer to the first question, I had noticed for three

HABITS, ETC., OF CEREBRATULUS LACTHUS. 113

summers that it was very difficult to obtain perfect specimens
toward the close of the breeding season, though they were
fairly common at an earlier date. On the contrary, the
number of specimens possessing regenerating papille increased
as the season advanced. It was evident, therefore, that they
must dismember for some reason during the breeding season,
and it was suspected that the eggs might be discharged in
this way. During the past summer the matter was put to
test with the following results.

A perfect male and female Cerebratulus were secured
during the latter part of June, and placed in an aquarium
half filled with the same mud from which they were taken.
They burrowed into this mud at once, and remained there
under fairly normal conditions, and apparently perfectly
healthy, until the 1st of September, when they were both
preserved on leaving.

They were nearly sexually ripe when obtained, and after
being kept a fortnight the female laid three batches of
eggs at short intervals, each of which was fertilised by the
male.

Soon after the last lot was laid they both dismembered,
leaving but a comparatively short piece of the body attached
to the esophagus. This anterior portion at once began to
regenerate, and by the Ist of September, an interval of
three and a half weeks, it possessed a regenerating papilla
nearly 50 mm. long in the female, and about 40 mm. in the
male.

The posterior fragments lived for two weeks, and then
died with no signs of regeneration. I have kept headless
fragments alive, however, under much less favourable cir-
cumstances for nearly a month, and McIntosh in his mono-
graph (84) states that most of the pieces of a fragmented
Lineus were alive six months after dismemberment, and that
the sexual products were developed and discharged from
them in a perfectly normal manner.

But this happened to be a male, and he could obtain no
eggs upon which to test the fertilising power of the sperms.

VoL. 43, PART 1.—NEW SERIES. H

114 CHAS. B. WILSON.

In another species the posterior fragment began to develop
a new head, and he figures several stages in the process,
which occupied nearly three months but was not completed.

Barrois also has described the regeneration of headless

‘trunk-pieces in another species, and they have been known
to regenerate new heads in the common Lineus socialis.

Fission certainly produces very little apparent effect upon
vitality. I have repeatedly obtained headless fragments of
both sexes containing unripe sexual products and kept them
until they ripened, a period sometimes of two or three weeks,
and then fertilised the eggs from one fragment with the
sperm from another, and obtained perfectly healthy pilidiums
as a result.

Of course the posterior fragments can eat nothing, but the
anterior ones display as voracious an appetite as ever imme-
diately after fission, or even during the process. This is attested
by the preserved specimen whose photograph is shown in
fig. 1. The prolonged retention of sexual functions by head-
less fragments under adverse circumstances gives some idea
of the vitality possessed by these worms in their native
haunts, but repeated search has failed to find a single one in
which regeneration has even commenced.

These faets, taken in connection with those developed in
the aquarium, lead to two conclusions. First, that Cerebra-
tulus frequently dismembers at the close of the breeding
season ; and second, that while the anterior fragments regu-
larly regenerate, the posterior ones seldom if ever do so.

Professor Benham, of Oxford, has noted a similar case of
spontaneous dismemberment in the genus Carinella (10).

Here also there was a relation between fission and genital
maturity, but of a different nature from that in Cerebratulus.

He found that the genital elements in Carinella were pre-
sent only in the posterior regions of the body, and that this
portion was constricted and cut off as fast as the elements
ripened.

Fission in this genus, therefore, would be a method of
discharging the ripened sexual products.

HABITS, ETC., OF CEREBRATULUS LACTEUS. 115

In Cerebratulus, on the contrary, the genital elements are
distributed throughout the whole body, and if there be any
priority in ripening, it is in favour of the anterior and not
the posterior portion. Fission does not take place until after
the eggs and sperm have been discharged, and hence it
cannot be regarded as assisting that discharge in any way.

We are thus confronted again with the question, what
advantage can result to the worm in thus parting company
with a large portion of its body at this particular time ?

The body is composed essentially of two series of pouches,
arranged in alternating pairs on either side of the straight
intestine. Ordinarily the digestive pouches occupy the larger
part of the space, but as the breeding season approaches the
reproductive organs begin to enlarge, and by the time the
sexual products are ripe they occupy practically the whole of
the space, and the intestinal ceca are flattened between them
until their opposite sides meet. This is especially true in
the posterior portion of the body, which at this time becomes
little more than one large ovary or testis, divided into lobes
by the flattened czca. McIntosh (84) states that “the
glandular elements in the walls of the digestive tract undergo
a certain amount of atrophy during the period of reproduc-
tive perfection.” For a long time, therefore, these intestinal
pouches can function very little, if at all, and so they contri-
bute nothing to the nourishment of the body.

After the eggs and sperm have been discharged there is
evidently still less use for them until the next breeding
season, and regeneration proceeds so fast that before that
time a new body will have been formed. In fragmenting,
therefore, at the close of the breeding season, it would seem
that Cerebratulus is parting company with a portion of its
body which has for some time been devoted to a single pur-
pose, that of perfecting the sexual products, and of which,
now that this purpose has been accomplished, it has no im-
mediate need.

Fragmentation under irritation is evidently a defensive
action. As Hubrecht (27) well says, “an animal that at the

116 CHAS. B. WILSON.

approach of danger can separate in two or more parts, each
of them capable of regeneration and so of producing an
entire new animal, evades this danger very effectively by
doing so.”

But even if all the fragments are riot capable of regenera-
tion, the nemertean still has the chance that its enemy will
be satisfied with half a loaf, and that the posterior half.

The actual fission of the body-walls is brought about by
internal phenomena which will be discussed later (see p. 118).

The circular muscles at the.severed ends contract violently,
and draw the margins of the rupture together so tightly that
the end is completely closed. It is also rounded like the true
anal end of the body, and this resemblance is often increased
by aslight emargination at the centre, due to the excessive
contraction of the muscles, and by the formation of a regene-
rating papilla in this emargination (fig. 2).

Such a papilla is slender and almost pure white in colour.
At first it is difficult to distinguish it from the true anal
papilla with which the body normally terminates, but it may
be recognised by the fact that it always possesses a very
broad base which fades gradually into the body-wall, while
the anal papilla is narrow and ends abruptly at the emargi-
nation.

After closing the broken end the circular muscles go into
a kind of tetanus, and keep it closed until its edges are joined
permanently by the formation of new tissue.

No such formation of new tissue has been observed thus
far in the case of the posterior fragments, but their ends
remain closed, and this no doubt aids them in retaining their
vitality for so long atime. The regeneration papilla rapidly
increases in length and width, but always tapers much more
than the normal body and remains light-coloured. Speci-
mens have been obtained in which this papilla was four or
five inches in length.

Fission takes place through the intestinal ceca, since they
offer the point of least resistance, and it usually involves a
rupture of the adjacent sexual pouches.

HABITS, ETC., OF CEREBRATULUS LACTEUS. 117

The process is very rapid under irritation, and may be
completed within a few seconds after the application of the
irritant. It may also take place at two or three points at the
same time.

If the irritation be extreme the process may be carried so
far that the whole body is divided into very short fragments,
the majority of which contain but a single pair of ovaries or
testes. This is a frequent result when the worms die through
a stagnation of the water in which they are kept.

In such instances the fission goes forward slowly and may
occupy several hours, and the contents of the genital pouches
are commonly discharged, whatever their state of maturity.

Fresh water acts as a powerful irritant upon Cerebratulus,
and always induces dismemberment, but it does not kill very
quickly.

Fission and regeneration in Cerebratulus is not confined to
the body-walls; it often takes place in the proboscis.

Under the action of powerful irritants both the anterior
and posterior connections of the proboscis are severed at
once, so that the extruded organ is not turned inside out, but
remains in its ordinary condition, or it may be half everted
and then extruded bodily. In either case it often lives a long
time, many days or even weeks. If it be irritated, and some-
times voluntarily, it moves in such a lifelike manner, and
looks so much like a young worm, that it might easily be
mistaken for one. Indeed, a similarly extruded proboscis of
another species did mislead several excellent zoologists (6).

They described it as a young animal, and its possessor as
viviparous, and presented both as such to the British Museum,
where they now remain as striking examples of the-folly of
judging by external appearances. A proboscis thus extruded
is reproduced by the formation of a small conical papilla on
the surface of rupture just in front of the ganglionic commis-
sure. This papilla grows backward rapidly, and a new organ
is formed in a few weeks. A similar renewal takes place
when the proboscis is forcibly removed by cutting (cf. 33).

This species, therefore, in common with others, possesses

118 CHAS. B. WILSON.

the ability to restore lost parts so quickly, so easily, and with
so little apparent inconvenience during the process, that any-
thing short of being absolutely eaten whole could scarcely
prove fatal.

We are left with the two most interesting questions to
answer. First, how is fission actually accomplished? The
only description of the process that can be found is the one
given by Benham (10). From a study of sections in different
stages of fission he concludes that a double row of nuclei
appear in the connective tissue along the line of rupture, and
that the longitudinal muscle-fibrils are severed between these
rows of nuclei, either through the cell substance of the con-
nective tissue becoming actively contractile and nipping off
the fibrils, or in consequence of the fibrils being eaten through
by some solvent action.

Neither of these conclusions would explain fission in Cere-
bratulus, for the whole process, under irritation, occupies only
a fraction of a minute. Hence the connective tissue would
have no time to become contractile, but must exist in that
condition all the while, ready to act at an instant’s notice,
i.e. it must itself be muscle. On the other hand, any sol-
vent powerful enough to act in so limited a time would not
be likely to stop with the mere severing of the longitudinal
muscle; it would dissolve everything within reach, and prevent
any regeneration. How, then, is fission accomplished ?

The rupture takes place through one of the intestinal ceca,
where the body-walls can be most easily divided.

It may take place at any caecum, and sometimes under ex-
treme irritation the worm will divide itself into fragments so
small that they contain but a single pair of pouches.

If there were any special apparatus for producing fission it
ought to reveal itself opposite each of the ceca, at least in
specimens killed after irritation. But careful examination
fails to reveal anything of the sort.

What we do find is that Cerebratulus has a thick layer of
circular muscles, which are almost entirely lacking in Cari-
nella.

HABITS, ETC., OF CEREBRATULUS LACTEUS. 119

There are also well-developed dorso-ventral muscles in the
walls separating the intestinal ceca from the reproductive
pouches, and these muscles are enlarged into thick pillars at
the inner ends of the walls (fig. 60). Finally, an examination
of the regenerating longitudinal muscles shows that in early
stages of growth they consist of both longitudinal and trans-
verse fibres, about equally divided (fig. 60). Later the longi-
tudinal fibres become more numerous, but there are always
many transverse ones to be found among them.

We are left to conclude that in Cerebratulus dismember-
ment is at least greatly assisted, if it be not entirely produced,
by a sudden and excessive contraction of these transverse
muscles of the body. The dorso-ventral muscles being meta-
merically arranged, and the others being evenly distributed,
dismemberment would occur at a definite place in each seg-
ment.

The final question is one which demands the method of re-
generation; we shall note only the most important points.
Immediately after the rupture is completed the walls of the
body are drawn together, and held in that position by the
contracted circular muscles. This brings the severed edges
of the ectoderm into contact with each other, and they
quickly unite and heal the wound over with the exception of
the posterior end of the intestine, which is left open to func-
tion as an anus. The cells in this newly formed ectoderm,
and the mesoderm cells immediately beneath them, proliferate
rapidly and form a regenerating papilla which grows back-
ward, keeping the anus open at its extremity. This papilla
is much paler in colour than the rest of the body, and at first
consists of a thin ectoderm entirely filled except at the centre
with mesoderm cells. At the same time the entoderm lining
the intestine grows backward as a straight tube along the
centre of the papilla. The muscular system is, of course,
developed from the mesoderm, and two things are worthy of
note in its differentiation. The circular muscles appear first,
and are followed by the outer longitudinal layer. The latter
is developed very slowly, and for a long time consists of a

120 CHAS. B. WILSON.

meshwork of longitudinal and transverse fibres which cross
each other nearly at right angles. The longitudinal fibres
are then increased greatly in number and size, while the
transverse ones remain about the same.

But the chief interest centres about the nervous system.
There has been a great deal of controversy over the origin of
this system in Nemerteans. Salensky in 1884 declared, as
the result of his researches on Monopora vivipara, that |
the nervous system was derived from the epiblast (44).

Hubrecht, two years later, declared that in Lineus ob-
scurus no portion of the central nervous system takes its
origin in epiblast, but that it is all of mesoblastic origin, and
he undertakes to disprove Salensky’s statement in regard to
Monopora (26).

Finally, Barrois and other investigators derive certain
important portions of the nervous system from invaginations
of the cesophagus, i.e. from hypoblast (7). All these inves-
tigators were working with embryonic material, in which it is
usually very difficult to determine the exact relation of the
different parts. It is interesting to note in this dismembered
Nemertean the mode of regenerating the lateral nerve-cords,
since the process is attended by phenomena which leave no
possible doubt as to the origin of the new tissue.

At the same time that the muscle-fibres first appear we
find upon the ventral surface two invaginations in the epi-
blast (fig. 21), forming two parallel grooves running longi-
tudinally along either side of the central line and quite near
to it. :

The ectoderm external to these grooves contains gland
cells, that in the grooves themselves and in the® space
between them contains no gland cells, but seems to be made
up entirely of epiblast cells. A third groove then appears in
the centre of the space between the other two, dividing it
into two low ridges (fig. 23). Toward the inner surface of
each ridge the epiblast cells are gradually changed into
neuroblasts, and form one of the long nerve-cords. These
cells are not fully differentiated, but seem more like the so-

HABITS, ETC., OF CEREBRATULUS LACTEUS. 121

called Ersatz cells, destined to give rise to epithelium, but
still capable of being transformed into neuroblasts.

After being formed in this ventral position the nerve-cords
migrate upward along either side of the body to their final
normal situation, carrying with them a thick covering of the
neuroblast cells (fig. 22). As soon as the nerve-cords leave
the ridges, gland cells begin to appear in the epiblast cover-
ing the latter, and it becomes in all respects like that on the
outside of the grooves. The grooves then disappear, and
leave a smooth epithelial surface.

The new nerve, therefore, is in no respect an outgrowth
from the old one, but results from a new growth of cells
which are entirely independent of the old nervous system.

It hardly seems reasonable that this Nemertean in its
embryology should derive its nervous system from mesoblast
when in regenerating lost parts it shows such a distinctively
epiblastic origin.

LarvAaL DEVELOPMENT.
Sexual Organs.

The sexes are distinct as in most Nemerteans. There is no
perceptible difference in external form or size, but in the
breeding season there is a difference in colour, due to the
sexual products which show through the body-wall.

The male then appears cream-coloured, while the female is
greyish red, turning to a light chocolate-brown in many
cases.

This difference is clearly seen in the male and female
photographed in fig. 3, the latter being much the darker of
the two.

In regard to the original formation of the genital pouches,
nothing can be offered in the present paper, since the deve-
lopment is not followed that far. Hubrecht considers (26)
that they arise as invaginations of the ectoderm in Lineus,
but Birger’s comment seems far more probable.

122 CHAS. B. WILSON.

He says (13, p. 480), “I have not been able to decide upon
the origin of the sexual pouches in those forms in which they
are preformed (e. g. Drepanophorus, Cerebratulus), but I am
convinced that they are of mesodermal origin because they
arise as clefts in the parenchyme or the dorso-ventral muscle
layer, while there is no possible doubt that the sexual
pouches in those forms in which they are not preformed
(e. g. Carinella, Malacobdella), but are developed in conjunc-
tion with the sexual products, arise from the parenchyme,
and hence are a tissue derived from the mesoderm.”’

The development of these pouches in a regenerating papilla
bears suggestive testimony toward the same conclusion.

We have already stated that in regeneration a thin ecto-
derm grows backward from the surface of rupture to form
the exterior of the papilla. At the same time the entoderm
forms a straight tube through the centre, which is of the
same size as the central lumen of the intestine since the anus
remains at the extreme tip of the papilla, and which is at
first without any side pouches (en., fig. 60). The space
between ectoderm and entoderm is filled with mesoderm,
from which is developed the body musculature.

The circular muscles and the two longitudinal layers
appear first, but are quickly followed by the dorso-ventral
muscles. ‘

A row of the latter muscles, each consisting of several
fibres, appears on either side of the intestinal tube and close
to it, at about the position they are to occupy when regenera-
tion is completed. These form the thickened pillars at the
inner ends of the germinal pouches (fig. 60, dvm.). Two
lines of smaller vertical muscles extend from these pillars
outward to the body-wall, diverging slightly. They are
woven together by connective tissue so as to form walls
which eventually separate germinal pouches from intestinal
ceca. As the papilla increases in width the walls grow also,
each pillar with its diverging walls enclosing a germinal
pouch (0.).

As soon as the pillars and walls begin to form, the ento-

HABITS, ETC., OF CEREBRATULUS LACTEUS. 123

derm of the intestine grows out to the right and left between
the pillars and along the side of the muscle walls, thus form-
ing the intestinal ceca. A blood-vessel, connecting the
dorsal with the lateral vessels, is formed in the connective
tissue at the inner end of each cecum (bv.). The genital
pouches are thus bordered anteriorly and posteriorly by
bands of dorso-ventral muscles, above by the proboscis
sheath, and below by the lateral blood-vessel beneath the
intestine.

An epithelium now appears, made up of small irregular
nucleated cells which cover the pouch unevenly. It is
impossible for this epithelium to be formed by an outgrowth
from either the ectoderm or entoderm, since it nowhere
‘comes in contact with either of them. It is evidently
derived from the parenchymal tissue which binds together
the vertical muscles to form the wall of the ovary or testis.

In winter the pouches are much smaller than the ceca,
and are flattened between the latter until their sides meet.

Karly in spring the sexual products begin to develop,
appearing first at the outer end of the pouch nearest the
muscles of the body-walls. In the figure given (fig. 63) it
will be seen that the pouch extends, in the form of separate
longitudinal pockets, both forward and backward along the
ends of the adjacent ceca (cf. figs. 61 and 62).

Odgenesis.—The first appearance of egg development is
an increase in one of the nuclei of the epithelium lining these
pouches. This is carried so far that the nucleus with its
large nucleolus comes to occupy a large portion of the cell.

It is then gradually surrounded by a layer of fine-grained
protoplasm which protrudes into the lumen of the pouch
(ec.’, fig. 65).

Subsequent development consists in a continued growth of
both cell body and nucleus, the latter developing into the
large germinal vesicle and the former spreading somewhat
over the adjacent epithelium cells which have remained
apparently unchanged (ec.”). This gives the ovum a flask
shape, the neck of the flask being inserted between the epi-

124 CHAS. B. WILSON.

thelial cells into the underlying connective tissue. As the
ovum matures the neck of the flask is gradually pinched off
from its connection with the epithelium, and the egg is set
free in the central cavity (ec.””).

It is not, however, naked as at first, but is now invested
with a delicate follicle, and is soon surrounded by a thick
layer of gelatine, both of which are apparently formed from
adjacent epithelium cells. As fast as an ovum is pinched off
into the central cavity the epithelium partly closes behind it
and new ova are formed, this process continuing until the
whole pouch is filled.

Interspersed among the ova and scattered through the jelly
which fills the central cavity are small spherical highly pig-
mented bodies, granular in structure.

These are probably the same as those described by
Hubrecht (27) for Drepanophorus and Cerebratulus
marginatus, and like them they disappear gradually as the
ova ripen. Hence they must contribute to the development
of the egg, and undoubtedly furnish the yolk material.
There are also other cells, slightly smaller and lighter in
colour, but staining more deeply, which are scattered all
through the central cavity. From these comes the gelatine
which fills all the space not occupied by eggs (gc., fig. 65).

In a ripe ovary the eggs are crowded together so closely
that they become more or less angular in outline.

If a mass of these eggs be examined before they have
touched any water they present the appearance seen in
fig. 18. Hach egg is separated from its fellows by the thick
layer of transparent gelatine which surrounds it. This is
bordered in turn by a stiffened external surface, where it
comes in contact with the coats of adjacent eggs. This gives
the whole mass somewhat the appearance of honeycomb,
made up of angular gelatinous cells, with an egg in each cell
very near its centre.

The gelatinous envelopes cling to the eggs almost as firmly
as the similar jelly around amphibian eggs (Amblystoma,
etc.), and they evidently serve the same purpose.

HABITS, ETC., OF CEREBRATULUS LAOTEUS. 125

The ripe ovum is spherical, quite large (0°1 to 0°2 mm. in
diameter), and appears white to the naked eye, but by trans-
mitted light is seen to be dark brown and opaque, owing to
the large number of yolk granules which it contains. It
possesses a germinal vesicle fully one third its own diameter,
much lighter in colour, translucent, and slightly elliptical in
outline.

Inside the germinal vesicle is a large spherical nucleolus,
which is nearly always eccentrically placed at one end of the
vesicle, the end farthest from the original point of attach-
ment (ec.””, fig. 65).

As the eggs are developed the ovaries increase greatly in
size, until finally they occupy nearly all the space, and the
ceeca are flattened between them.

Formation of Oviduct.—The ovaries now push inward
nearly to the wall of the intestine, and outward, downward,
and upward to the body-wall. In both horizontal and verti-
cal sections they appear larger at either extremity than in
the middle.

When the eggs are nearly mature each sac pushes out into
the longitudinal muscle layer, presumably at the point where
it meets least resistance, i.e. on the dorsal surface about one
quarter of the diameter of the body from its lateral edge.

It then penetrates the muscles as a fine canal, the first
beginning of a genital duct, which as soon as the eggs or
sperm are fully ripe pushes through the skin to the exterior.
The epithelium lining this canal is made up of flattened cells,
which are elongated until they look almost like muscle-
fibres.

Just inside the mouth of the duct there is a cluster of
gland cells, which secrete a large amount of mucus.

As maturity advances the ducts grow shorter, in conse-
quence of the distension of the body and the resultant de-
crease in thickness of the body-walls. Hence when the
genital products are ripe they are easily discharged through
these ducts.

As soon as the egg enters the water it is seen to be sur-

126 CHAS. B. WILSON.

rounded by a zona pellucida, which swells up in fifteen or
twenty minutes to about twice the diameter of the egg itself
(fig. 20).

This zona pellucida is entirely distinct from the gelati-
nous envelope already mentioned, from which it is separated
by two concentric membranes, situated close to each other
and at quite a distance from the surface of the egg. The
membranes and the zona pellucida itself are perfectly colour-
less and transparent. Soon after the eggs are placed in
water for artificial fertilisation, or soon after they enter the
water when laid naturally, the outer gelatinous envelope
dissolves and disappears, leaving the egg surrounded only by
the zona pellucida and the membranes. If the eggs are
placed in water before they are fully ripe the outer envelope
does not disappear, but remains holding the eggs together in
bunches.

After the ovum is pinched off into the central cavity of the
ovary it retains its original flask shape for a long time, some-
times even after it is laid. Hence it occasionally happens
that after the outer gelatinous envelope has disappeared the
limiting membranes will be found to possess a teat-like pro-
tuberance on one side, which is manifestly the remains of the
original connecting stalk (fig. 20). And sometimes a cor-
responding remnant may be found upon the egg itself, the
neck of the old flask which has not been wholly withdrawn
into its body. These protuberances are of special signifi-
cance, because they enable us to orient the eggs perfectly,
and to determine that the polar bodies always come off at a
point diametrically opposite to them, and hence opposite to
-the original point of attachment. It should be added that
since the egg is always elongated into its flask shape at
approximately right angles to the surface of the epithelium,
it follows that the egg axis bears no definite relation to the
axis of the mother, but may stand at any angle with it.

Spermatogenesis.—The testes are formed and developed
in the same way as the ovaries. The origin of the spermatozoa
in Lineus has been admirably worked out by Lee (80). He

HABITS, ETC., OF CEREBRATULUS LACTEUS. 127

found that they were not developed in preformed sacs, but
that they themselves gave rise to the latter, or rather
furnished the occasion for their existence. <A few large cells
appeared in the body parenchyma, which were soon gathered
into bunches, around which was developed a thin membrane,
thus forming a testis. But in Cerebratulus the spermatozoa
as well as the eggs are developed from the epithelium lining
the genital sacs. The cells of this epithelium increase rapidly
by division, and the original nuclei become larger, as in the
development of the ova. Through the consequent crowding
of the cells some of them are pushed out into the central
cavity, where they become sperm mother-cells and form
spermatozoa by segmentation (fig. 66). The transition from
the sperm mother-cell, or spermatid, into the spermatozoon
is apparently not direct, there being intermediate stages
(fig. 68).

But the chromatic substance of the nucleus of the sper-
matid gradually separates itself as the head of the sperm,
while the body draws itself out into a long flagellum (cf.
figs. 67 and 68). The general type of development is thus
very similar to that given by Lee (loc. cit.), the essential
difference being that in Cerebratulus the testis is preformed
and the sperms are developed from its epithelium.

When fully ripe the sperms are very large (0:05 mm. long)
and of a peculiar shape (fig. 59; compare also fig. 42, in which
a sperm and the polar bodies are drawn to the same scale).

The head is long and sickle-shaped, tapering to a very
fine point at the anterior end, and usually somewhat curved
into a crescent. The middle piece is nearly spherical, and
caps the posterior end of the head like the top of a clothes-
pin.

The tail or flagellum is very long, many times the length
of the head and middle piece, and is undivided.

These sperms have a slow movement, but it is seemingly
very strong, for they experience no difficulty in getting
through the two egg membranes in order to reach the egg
itself.

128 CHAS. B. WILSON.

Egg-laying.

The breeding season extends over about two months or ten
weeks. Some of the females begin laying by the 10th of
June, while others delay till the 20th or 25thof August. In
general those which live in sheltered coves or bays lay earlier
than those found in exposed positions, while the nearer low
water mark the worm is found the later will its eggs be
deposited. By changing the locality, therefore, from which
the eggs are obtained, fertile ones can be secured throughout
the entire two months. Although Casco Bay is but little
north of Long Island Sound, the above dates are radically
different from those given by Coe (15), who states that in the
vicinity of New Haven the breeding season extends over the
month of April, and that by “the first of May nearly all the
genital products have been discharged.” This serves to
emphasise still farther the marked differences which have
been noted in the breeding seasons of other Invertebrates
from these two localities.

Birger (13) states that Nemertean eggs are usually joined
together in strings or balls, but that they are rarely laid
singly. Metschnikoff (85) gives Lineus lacteus as one of
these rare instances, but he tells us nothing whatever as to
the manner in which they are laid.

From the rapidity with which the outer gelatinous envelope
disappears when the eggs are placed in water for artificial
fertilisation, it would be naturally inferred that the eggs, if
not laid singly, at least separated very quickly, since this
envelope would be all that held them together. That this is
what actually occurs was proven by observation. The first
lot of eggs laid in the aquarium (cf. p. 118) were found
early in the morning already fertilised. A day or two
later the process was repeated while the aquarium was being
watched, also early in the morning. A stream of eggs was
noticed coming out of the opening of one burrow, while from
another burrow at the opposite side of the aquarium sperms
were issuing.

HABITS, ETC., OF CEREBRATULUS LACTEUS. 129

Fortunately the burrow occupied by the female was in
contact with the side of the aquarium, and the whole process
could be watched through the glass. It was seen that the
contents of a very limited number of genital pouches near
the anterior end of the body were being emptied. The eggs
were assisted in their passage through the oviduct by a con-
traction of the circular muscles of the body-walls over the
area occupied by the pouches. When first issuing from the
body the eggs were gathered in loose bunches, held together
by the gelatinous tissue already described. These bunches
were pushed along gradually by successive waves of muscular
contraction in much the same way that the ring of mucus
formed by the earthworm in egg-laying is worked off the
forward end of its body.

In this way the eggs came to lie at the bottom of the
vertical portion of the burrow around the head of the Nemer-
tean. Here the action of the water quickly dissolved the
gelatinous material that held them together, and left them
free. They were then caught in the current generated by
the Nemertean’s breathing, and carried upward out of the
mouth of the burrow and some distance away from it. Eggs
were laid in this manner several times, and upon them were
verified all the phenomena of maturation and segmentation
derived from artificially fertilised eggs. But in so restricted
a space there was always a tendency to over-fertilisation, and
many of the eggs were killed in this way. Whenever a con-
siderable number were laid at once they collected together at
the bottom of the aquarium, and were held together loosely
by adhesion of the zone pellucide, but a slight disturbance
in the water separated them and they floated away free.

Nothing could be seen of the burrow occupied by the male
except its opening, but as sperms were issuing from this in
the same way that eggs were from the other, and as a thick
mass of sperms was afterward found at the bottom of the
burrow in a position corresponding to that of the eggs, it would
seem safe to conclude that the sperms are discharged in the
same way as the eggs.

vou. 43, pant 1.—NEW SERIES, I

130 CHAS. B. WILSON.

Tt follows that the eggs must be fertilised outside the body
of the female, and that the sperms often have a considerable
distance to travel before reaching the eggs. This will account
in part for their very strong motion, and it also verifies the
statement made by Coe (15) that all the genital products are
not discharged at once, but only a limited portion of them.
From the fact that the several lots of eggs were laid so near
together, it seems probable that the period of egg-laying in
any one individual does not occupy more than a week or ten
days. When Nemerteans are kept in confinement without
any chance to burrow, they usually pull themselves in pieces
after a short time. If the sexual products are ripe when this
occurs they are always discharged, and perfectly healthy
fertilised eggs may often be obtained in this way.

Darwin, in his ‘ Descent of Man,’ says that these animals,
like many other Invertebrates, “apparently stand too low in
the scale for the individuals of either sex to exert any choice
in selecting a partner, or for the individuals of the same sex
to struggle in rivalry.” This is undoubtedly true, but we
must remember with McIntosh that this does not exclude
the possibility of a very delicate sexual instinct. The simple
fact that the sperms are discharged simultaneously with the
eggs, even though the burrows of the male and female may
be some distance apart, proves the existence of such an in-
stinct.

Fertilisation and Ripening.

There is nothing resembling copulation, eggs and sperm
being discharged from separate burrows. When ripe the
egos fertilise almost immediately, but with a little care the
entrance of the sperm into the egg may be seen, though its
subsequent action must remain invisible owing to the opacity
of the yolk granules. A great many sperms usually pene-
trate the limiting membranes, but only one of them enters
the egg, though instances of polyspermy are not unknown.
The sharp curved point of the sperm is placed against the
surface of the egg, and a gentle vibratory movement 1s pro-

HABITS, ETC., OF CEREBRATULUS LACTEUS. 131

duced by the lashing of the long tail. Although this appears
like a weak movement under the microscope, it must really
be very strong, for the head of the sperm is pushed in steadily
and quickly.

The curve in the head of the sperm renders any rotary
motion impossible. As soon as it has entered the egg the
latter becomes more opaque than before, and the large trans-
lucent germinal vesicle quickly breaks down and disappears.
This is followed in turn by the giving off of the polar bodies.

If the supply of sperm be sufficient, so many of them pene-
trate the membranes that the latter are broken down and
disappear entirely. Then the sperms, clinging to the egg
with their heads and lashing with their tails, give the egg a
rotary motion, exactly similar to that produced in later de-
velopment by the cilia. This may be kept up for an hour or
more.

Formation of Polar Bodies.—The first polar body
appears about an hour and a quarter after fertilisation, and
always at a point diametrically opposite the protuberance in
the limiting membrane, when such a protuberance is present.

As already noted, this is the remnant of the original stalk
whereby the ovum was joined to the wall of the ovary, and
hence those eggs which do not exhibit it must have been
separated so gradually and completely as to have left no
trace of their former connection. But it is reasonable to
infer that the polar bodies appear in them also opposite to
the point where such connection formerly existed. If this be
true, it follows that the connection of the ovum with the wall
of the ovary during development results in its permanent
polarisation, and the point at which the polar bodies are to
appear is predetermined.

There is no perceptible separation of formative and nutri-
tive material, but correlated phenomena indicate that the
point of attachment is the vegetative pole. The food supply
must come to the ovum through this attachment, and in early
development the germinal vesicle often lies eccentrically near
it (fig. 64). These facts, taken in connection with what has

132 OHAS. B. WILSON.

already been given in reference to the early development of
the ovum, furnish strong corroborative evidence to the truth
of the view formulated by Mark in 1881 (82) and by Watasé
ten years later (47). The ovum is at first isotropic, but after-
ward acquires polarity and other promorphological features
through its topographical relation to the remaining cells of
the maternal tissue. In this species the primary axis of the
ovum seems to be formed at right angles to the surface of
the epitheliam from which it originates (cf. 50).

The appearance of the first polar body is accompanied by
the usual flattening of the surface, and sometimes by a slight
pitting in of the ectosarc to meet it (fig. 23a). The latter
effect is often abnormally increased if the cover-glass is
allowed to press upon the egg. The gradual emergence and
rounding of the first polar body is shown in figs. 24—26.

A slight swelling first appears at the point of emergence,
and rises as a symmetrical hemisphere. ‘This increases in
size, and within a minute becomes a short cylinder, or a more
or less rounded conical protuberance (fig. 24).

Within half a minute more the base of the cylinder is con-
stricted, and the constriction increases until the polar body
has entirely separated from the egg (fig. 26). So far as
observed a connecting protoplasmic band is always present,
but it requires a good light and a high power to detect it.

The flattening of the pole draws the surface of the egg
away from the membranes, so that the polar body after its
extrusion is not very near them. It now becomes approxi-
mately spherical, the whole formation having occupied about
three minutes.

It lies in contact with the surface of the egg or near it for
ten or fifteen minutes, during which the egg resumes its
original shape, and then withdraws a little, but still retains
the connecting band of protoplasm. ‘This withdrawal is
simultaneous with the first appearance of visible spin-threads,
and marks the beginning of a long series of remarkable
activities which are of sufficient importance to demand a
separate description (see p. 138).

HABITS, ETC., OF CEREBRATULUS LAOTEUS. 133

About six or eight minutes later the first body returns to a
position near the egg, and there awaits the second body.

A swelling appears at the point where the connecting band
of protoplasm from the first body joins the egg (fig. 28).
This rapidly becomes nipple-shaped, lifting the first body
upon its slightly enlarged apex (fig. 29). There is the same
gradual constriction as before, and the whole formation
occupies about the same time, three minutes. There is also
a second flattening of the egg, sometimes a slight emargina-
tion, whereby the surface is withdrawn from the membranes,
so that the combined first and second bodies, even though
the latter is elongated, do not get any nearer to them. The
second body is smaller than the first, and does not become
spherical, but is elongated parallel to the surface of the egg
into a spindle or melon shape (fig. 38).

Sometimes the first body divides after separation, or, in-
stead of a single second body, two occasionally appear side
by side.

In both these abnormal cases one of the paired bodies
withdraws by itself, while the other two remain and continue
their filose activities.

Activities of the Polar Bodies.—During their for-
mation and almost to the blastula stage the polar bodies
afford a remarkable example of that form of protoplasmic
activity which was first described in echinoderm eggs by G.
F. Andrews, and designated “ filose activities or spinning ”
(4).

These activities have already been carefully described
in this Nemertean in an interesting paper by Dr. H. A.
Andrews (2), in which some doubt was expressed as to the
certainty that such activities were entirely normal. The
eggs used by Dr. Andrews were fertilised artificially, but
great care was used in observing them, and the results were
verified by comparison with other eggs which developed into
normal embryos. JI am glad to add in confirmation the
following description taken from eggs laid in an aquarium
under fairly normal conditions and fertilised naturally.

134 CHAS. B. WILSON.

The first polar body, immediately after separation, exhibits
amoeboid changes of outline, as can be seen by comparing
different figures. hese are most prominent during the first
four or five minutes. At the end of this time the body has
become spherical, and stands close to the surface of the egg,
with which it is connected by a narrow band of protoplasm
(fig. 26).

It now begins to exhibit spinning activities. Numerous
fine transparent threads of protoplasm radiate outward
from its surface, usually appearing first at one end (the
body is considered as lying with its side toward the egg),
but frequently elsewhere. The whole surface becomes
covered with such radiating threads, which vary considerably
in size and visible length. At the same time the body
moves away from the egg slowly, but whether as a result of
the spinning or the amceboid movement or both could not be
determined.

No further change occurs until the appearance of the
second polar body, except that sometimes the surface of the
egg in the vicinity of the first body rises up into one or more
small papille. These occur most frequently on eggs which
afterward become abnormal, and they disappear quickly.

As soon as the second body appears there is a distinct
change in the activities of the first body. The body itself is
slightly elongated parallel with the surface of the egg, and
becomes flattened on the inner side. The filose threads,
which have been hitherto distributed over its surface, now
aggregate toward one or both ends, and gather into long
filaments visible under a low power. They extend outward
and downward toward the surface of the egg (fig. 31), but
could not be traced to actual contact with the surface. But
this affords no proof that they do not reach it, for they are
extremely delicate and transparent, and they diminish in
size the farther they are followed, so that it becomes
difficult to see them.

Certain phenomena at just the place on the egg toward
which they point indicate that they really do reach the surface.

HABITS, E'TC., OF CEREBRATULUS LACTEUS. 135

Furthermore, as Dr. Andrews has noted (2), the appear-
ance of the first body during the extrusion of the second,
and its subsequent changes in shape, are just what they
would be if the first body were pushed upward by the
second and at the same time held down to the surface of the
egg by these filaments.

The band of protoplasm connecting the first body with the
egg remains after the second body is formed, and connects
the two bodies. The second body immediately begins to
elongate parallel with the surface of the egg, and assumes a
spindle or melon shape, which always characterises it. A
small papilla now appears on the egg at either side of the
second§body and some little distance from it (fig. 33). These
two papille are situated exactly where the long filaments
from the first body would strike the egg if they reached that
far, and it seems probable that the two are connected. The
papillz vary in size and number on different eggs, but they
are usually two.

They are arranged symmetrically, one upon each of what
will soon become the first two blastomeres (fig. 34). It is
also significant that the spindle of the egg nucleus after the
extrusion of the first polar body rotates through 90°, as in so
many other eggs, and becomes parallel with the surface, its
two ends being just beneath the points where the papille
afterward appear (fig. 56).

The summits of the papillae are covered with fine spin-
threads, radiating outward, while the surface of the egg
between them is flattened or even concave. They continue
for about five minutes and then disappear (fig. 36). In eggs
not quite ripe, or developed under abnormal conditions,
especially pressure, the papillae are increased in number,
size, and duration (fig. 37).

I have repeatedly seen unripe eggs, on reaching this
period in their development, put out ten or twelve large
pseudopodia-like processes in place of the two papillae, and
gradually go to pieces.

When the papilla disappear the egg returns to its

136 CHAS. B. WILSON.

original form, thereby carrying the polar bodies nearer the
membranes.

In one or two instances the recovery was carried so far
that the polar bodies were pushed out into the membranes
as in fig. 39.

This figure shows that there are two independent mem-
branes, for only the inner one is bulged outward to any
extent.

It also shows that the first polar body is surrounded by a
zone within which spinning activities are sufficiently strong
to prevent the membrane from entering. ‘The relative
distance of the two bodies from each other and from the egg
does not seem affected at all by this contact with the mem-
brane, so that the latter must be very delicate and yield
readily to slight pressure. The second body in pinching off
from the egg also leaves a narrow band of connecting proto-
plasm (fig. 35), which keeps both bodies in close relation
to the egg.

When separated it begins to show activities somewhat
different from those of the first body (fig. 36). While
forming, fine threads are seen radiating outward from
nearly all visible parts of its surface, but as soon as it
assumes its characteristic spindle shape the two poles at the
extremities of the spindle become the centres of filose
activity.

At first they send out slender threads in various directions,
but soon they begin to elongate as pseudopodia processes (fig.
35), carrying the centre of activity away from the body itself.
The ends of the processes enlarge, and may even form secon-
dary spindles, from which fine threads radiate in all direc-
tions (fig. 38). Short filaments still appear and disappear at
different points on the body itself, but they are very transi-
tory, and evidently of secondary importance.

In unripe eggs, and especially in those developed under
abnormal conditions, the spinning activities may be greatly
increased. These are the eggs usually covered with papille
in the vicinity of the polar bodies, and the abnormal spin-

HABITS, ETC., OF CEREBRATULUS LACTEUS. 137

threads run back and forth between bodies and papille,
lacing them together firmly (fig. 37). But even then the
threads are remarkably independent of one another, and in
no instance were two of them seen to fuse where they crossed,
though sometimes one would divide and attach itself by two
or more strands.

These abnormal activities also emphasise the fact that those
spin-threads which connect polar bodies and egg emanate
from the former. Of the spin-threads arising from the egg
the longer ones do not extend toward the polar bodies, while
the shorter ones, which do, evidently do not reach across.

The polar bodies take the initiative in spinning; and,
although the egg responds, it never reaches the same degree
of activity.

If a higher power is used the polar bodies are transparent
enough to disclose something of their internal structure.

The first body is pear-shaped, with a short process extend-
ing from the smaller end like a stem (fig. 41). Numerous
threads radiate in every direction from the enlarged tip of
this process, while a similar bunch of threads radiate immedi-
ately from the body at its opposite end, and a few weak
threads appear on the outer side. The interior is filled with
fine-grained protoplasm, with chromosomes at or near the
centre.

The normal number of these seems to be five, but they vary
considerably, now appearing as five distinct curved rods (fig.
41), and again fusing to one large mass, with or without
a smaller one beside it (fig. 40). The same chromosomes may
be seen in the second body, sometimes separate (fig. 44), at
others more or less fused (fig. 45). The fusion in both bodies
occurs at the time when they frequently divide, but the karyo-
kinesis does not show very plainly. During the emergence
of the second body the first one shows quite a marked polari-
sation (fig. 34), but the resultant figure is never as perfect a
spindle as in the second body, and the polarisation disappears
early in segmentation (fig. 44). The second body, on the
contrary, maintains its characteristic spindle shape through-

138 CHAS. B. WILSON.

out segmentation, its ends are enlarged more than those of
the first body, and they continue to be centres of filose activity
nearly to the blastula stage (cf. figs. 44, 45).

Summary.—l. The first polar body acquires its spinning
power soon after separation, manifests it chiefly in the form
of diffused spinning with little polarisation, and loses it early
in segmentation. The second body acquires this power
during separation or immediately afterwards, possesses a
marked polarisation, and retains its activity at least to the
blastula stage.

2. In both bodies the poles are at either extremity of an
axis parallel to the surface of the egg, and the spinning
activities are more or less centred there. In consequence
these two points assume a character notably similar to that of
the two centrospheres at either end of the nucleus during
segmentation.

3. Both bodies show in their interior chromosomes, whose
normal number seems to be five, but which vary greatly in
number as the result of partial fusion.

4. The surface of the egg in the vicinity of the polar
bodies also exhibits spinning activities during and subse-
quent to the formation of the bodies. This spinning is quite
diffuse, but just after the separation of the second body it
becomes concentrated at two papillae symmetrically arranged,
one on either side of the first axis of segmentation. The
long spin-threads from either end of the first body connect
with these papille. 'The internal phenomena of fertilisation
and segmentation are invisible through the yolk granules,
but may be seen in sections.

Conclusions.—l. The polar bodies and the egg
itself, in this species, are to a large extent physio-
logical as well as morphological equivalents.

Evidently the half of the original egg nucleus which
remains within the egg retains the same characteristics as
the halves which are successively extruded in the polar
bodies, or else the latter acquire distinct characteristics
during extrusion—an hypothesis which is hardly tenable.

HABITS, ETC., OF CEREBRATULUS LACTEUS. 139

Hence the polar bodies on the exterior, where they are
plainly visible, repeat for us the same activities, or very
similar ones, that occur invisibly within the egg. We find
both bodies elongated at right angles to the first plane of
cleavage, while their ends, enlarged over each blastomere,
become centres of spinning activity.

Externally the surface of each blastomere also manifests
spinning activity by rising into a papilla which becomes con-
nected with the enlarged end of the first body on its own
side.

These visible filose activities of the egg are much more
prominent while the egg nucleus remains near the superior
pole, and diminish sensibly as it descends to meet the sperm
nucleus.

Such a result would naturally follow the intervention of
inert yolk material between the active nucleus and the
surface of the egg. The increased activities of some eggs
immediately after the extrusion of the second polar body (2,
p. 232, and fig. 37), whereby the whole surface of the egg at
the superior pole is raised into ridges and papille covered
with filaments, admit of ready explanation if we assume that
in such eggs for some reason the nucleus does not descend at
once, but tarries awhile close to the surface.

Internally the female pronucleus, after the extrusion of the
first polar body, rotates through 90°, as already stated, so
that its ends are just beneath the points where the papillez
appear (fig. 56).

This has been noted in Cerebratulus marginatus also
(16, figs. 20 and 22), where the amphiaster is plainly parallel
to the elongated polar body. Furthermore there is good
evidence for believing that the female pronucleus again
rotates after the extrusion of the second body, and becomes
parallel with the latter (fig. 57). But with the amount of
material at my command for this particular phase of deve-
lopment I have been unable to decide beyond a doubt.
After the egg nucleus has united with the sperm nucleus the
resultant segmentation nucleus is also elongated at right

140 CHAS. B. WILSON.

angles to the first plane of cleavage, and forms an amphi-
aster. Its ends are not enlarged in each blastomere, but
there is instead a centrosome at either end, which becomes
the centre of activities very similar to those manifested by
the enlarged ends of the polar bodies (fig. 58).

Is it too much to conclude that this marked similarity
between external and internal phenomena cannot be the
result of chance, but that there must be a close relation
between the two? These considerations lead naturally to
our second and third conclusions.

2. In Cerebratulus we have an instance where
odgenesis approaches more closely to spermato-
genesis, and thereby shows more clearly the mor-
phological equivalence of the two.

Adopting the view first put forward by Mark in 1881 (82),
that the polar bodies are to be regarded as abortive eggs, we
find in Cerebratulus an instance where they are less abortive
than usual. In spermatogenesis the spermatocyte usually
divides into four sperms, each of which is in every way the
equal of all the others. But in the final division of the
odcyte the perfect egg ordinarily appropriates to itself all
the activities of the three rudimentary ones, as well as the
entire mass of the yolk. In Cerebratulus, however, it con-
tents itself with taking all the yolk, and leaves quite a share
of the activities for the polar bodies, especially the second
one.

38. The egg-cytoplasm, and probably the female
pronucleus also, exhibit a well-marked polarity at
right angles to the first plane of cleavage before
the two pronuclei have joined to form the segmen-
tation nucleus.

This can be easily seen by reference to figs. 34 and 56.
Even in those exceptional instances where the whole polar
surface is covered with ridges and papille the same trans-
verse polarisation is manifest in the increased size of certain

of the papille (fig. 37; cf. also 2, fig. 12).

HABITS, ETC., OF CEREBRATULUS LACTEUS. 141

Segmentation.

Segmentation is total and equal. The first furrow les
along an axis joining the polar bodies and the point of
original attachment. This fact furnishes further evidence
that the axis of segmentation was determined early in deve-
lopment. About an hour and a quarter after fertilisation
the egg begins to elongate at right angles to the axis just
mentioned, thereby drawing the polar bodies away from the
membranes. It continues to elongate until the long dia-
meter becomes one and a half times the shorter one.

If viewed at this period under a low power with strong
illumination, it can be seen that the nucleus has divided, and
the halves have migrated to either end of the ellipse.

A shallow groove appears beneath the polar bodies and
the egg elongates still more, the diameters bearing the rela-
tion to each other of five to eight. Two minutes later a
corresponding groove appears on the opposite side, and they
both deepen rapidly, the first more rapidly than the second.
There is also a continued elongation, the diameters standing
in the relation of five to nine. At the end of this period,
which has lasted ten minutes, we find the egg divided into
two almost perfectly spherical blastomeres, joined by a very
narrow isthmus, whose distance from the polar bodies is
twice that from the opposite pole (fig. 49).

Behaviour of the Polar Bodies.—Usually the flatten-
ing of the egg preliminary to segmentation moves the polar
bodies, but sometimes the connecting band of protoplasm
elongates and leaves them in their original position. When
the furrow appears they are always pulled down into it.
Under a low power it is seen that they follow the changes in
position which the surface undergoes as if they were attached
to it.

Under higher magnification one can detect that the bodies
themselves are somewhat changed in contour by the process
(fig. 42). Instead of its characteristic spindle shape, with
the long diameter parallel to the surface of the egg, the

142 CHAS. B. WILSON.

second body is pulled ont at right angles to that surface, until
sometimes the perpendicular axis becomes the longer one.
Evidently its attachment must be firm enough to bring about
such a change.

Its spinning activities are not disturbed in the least, and
the former poles remain the centres of such activities. This
often results in an irregular quadripolar appearance, the two
connecting bands of protoplasm arising from the vertical
poles, while from the horizontal ones radiate long filose spin-
threads.

We have said that the cleavage groove nearest the polar
bodies usually occupies two thirds or more of the entire
diameter of the egg. Hence, if the polar bodies remained
as near the bottom of the groove as they were when it started,
they would be drawn in at least to the centre of the egg.
But such is not the case. They do sometimes enter within
the general contour of the whole mass, but they usually
follow the groove only a little way, and remain partially or
wholly outside the general contour. As aresult, the band of
protoplasm connecting the second body with the egg appa-
rently changes its point of attachment to the latter. Instead
of remaining near the bottom of the groove, it removes to a
comparatively long distance from it on the side of one of
the blastomeres (fig. 46).

Is this change of position real or apparent? Is it the
body which has changed, or the bottom of the groove?

That portion of the egg where the connecting band origin-
ally appears is the centre of activity during the extrusion of
the bodies, and naturally remains connected with them during
their filose spinning. It then becomes the point at which the
protoplasmic activities resulting in the first cleavage are
manifested. Hence, if the point of attachment were to be
changed, it would seem natural that it should be toward some
other centre of activity. But no such centre can be found at
or near the surface of either blastomere, so that a priori we
should not expect any change. Again, the only way in
which such a connecting band could change its position would

HABITS, ETC., OF CEREBRATULUS LACTEUS. 148

be either by the withdrawal of the filose threads of which it
was composed and the protrusion of others from a new point,
or by a gradual slipping along the surface. The latter hypo-
thesis is untenable from the very nature of the spin-threads,
and the most persistent watching failed to reveal any tempo-
rary withdrawal of the connecting protoplasm. We are left,
therefore, to the conclusion that the change is only apparent,
and that the actual point of attachment remains the same.
This affords a means of identification whereby we can follow
one particular portion of the surface during segmentation. In
this way we find, first, that there is no investing membrane in
contact with the surface of the egg, but that the protoplasm
of the latter forms an ectosarc similar to that of the amceba.
This is lighter in colour and more transparent than the
remainder of the egg, partly because it contains no yolk
granules.

Again, we find that the change of position is due to the fact
that the point of attachment remains stationary, while the
groove advances; in other words, the old ectosarce travels
inward, during the formation of the groove, only the limited
distance necessary to accommodate the more rounded outline
of the blastomeres, and the ectosare which covers the bulk of
the groove is anew structure. This is easily formed, since it
consists essentially of egg protoplasm minus its yolk granules.

Anticipating a little, we find that after the two blastomeres
have come together again, and the furrow has been filled in
by appression, the point of attachment does not return to the
bottom of the furrow, but, approaching it closely, remains at
a distance which varies within narrow limits for different eggs
(fig. 50).

The two edges of the old ectosarc do not quite meet, but
a portion of the new ectosare remains exposed along either
side of the furrow. This portion increases with subsequent
segmentations until the point of attachment comes to lie
near the centre of the cell in the 128-cell stage (fig. 45).

This is the natural result, since the egg increases slightly
in size with each segmentation. The protruding surface of

144, CHAS. B. WILSON.

each blastomere retains a portion of the old ectosarce near its
centre, and this is surrounded by a border of newly formed
ectosarc, whose relative width increases as segmentation
advances.

Finally, the persistence of the point of attachment of the
second polar body greatly facilitates the orientation of the
ego. As soon as the first groove is formed the blastomeres
become almost perfectly spherical. Most eggs having total
cleavage show a rounding of the blastomeres, but in this
Nemertean they are almost separated, so that the egg assumes
a dumb-bell shape, with a short handle eccentrically placed.

As would be inferred, they are easily separated, with
results to be noticed later.

Certain interesting phenomena precede the coming together
and flattening of the blastomeres. In this egg, as in that of
Echinoderms (5), filose activities similar to those of the polar
bodies arise on the surface of the blastomere.

In fact, they are continuations of the same activity which
has just been spinning the connecting bands of protoplasm
and producing the first cleavage groove. Fastened at a
point near the opening of the groove are the polar bodies
(fig. 46).

Close watching in a good light now reveals spin-threads
forming between the blastomeres. A small papilla appears
nearly opposite the attachment of the polar bodies, and
gradually increases until it becomes half as large as one of
them.

At first filose threads radiate from this papilla in different
directions, but they gradually fuse into one thick thread,
extending obliquely across the groove to a point a little
below where the polar bodies are attached (fig. 47). Half a
minute later another spin-thread appeared below the first,
but no papilla could be seen at its origin, probably because
it was not in perspective. This thread divided when half-
way across, and the two ends were attached separately
(fig. 47).

At the same time spinning activities began on the opposite

HABITS, ETC., OF CEREBRATULUS LACTEUS. 145

side of the connecting isthmus. A large papilla was formed
on the same blastomere to which the polar bodies were
attached, and a moment later a similar one appeared on the
other blastomere (fig. 47). Short spin-threads radiated
from both papille; then the first papilla disappeared, but
the spin-threads remained and formed quite a stout thread
extending across the groove (fig. 48). In some eggs the
threads first formed remain until those upon the opposite
side of the isthmus have appeared. These eggs are of
special interest, because they show that the spin-threads
contain contractile protoplasm (fig. 51). The two blasto-
meres were drawn together on the side of the isthmus farthest
from the polar bodies, and held for an instant and then re-
leased. During this contraction the spin-threads shortened
and thickened visibly, showing that they were at least active
agents in the process. The papille also were pulled out
slightly in the direction of the spin-threads, as would be
expected of yielding protoplasmic material. After an in-
terval of five seconds the blastomeres were pulled together
again, this time on the side nearest the polar bodies. ‘These
movements on opposite sides of the isthmus alternated at
irregular intervals for two minutes, when the papille had
entirely disappeared, and the blastomeres had been drawn
together and flattened. These contractile movements were
noted independently, and commented upon by a friend who
was watching another lot of eggs, and were observed severai
times subsequently while studying other phenomena, so there
can be no doubt of their reality. It must be remembered in
judging these facts that the conditions are specially favour-
able in the present instance for the occurrence of just such
phenomena. Intercellular connections by means of spin-
threads have been clearly demonstrated in the eggs of many
Metazoa (cf. 3), and have even been retained in preserved
specimens.

We should expect to find them in Cerebratulus as a natural
sequence to the marked spinning activities of the polar bodies.
The perceptible motion of the blastomeres is rendered possible

VOL. 43, PART 1.—NEW SERIES. K

146 CHAS. B. WILSON.

by their almost complete separation ; the isthmus joining them
is very slender, and can be bent by a slight force.

We thus have in these eggs a combination of strong spin-
ning activities with just the physical conditions best adapted
for rendering them manifest. These activities are more
profuse at this early stage than in any later period of de-
velopment. Whether the blastomeres are sensibly reduced
by this spinning is difficult to determine, because they are
continually changing their shape at just the time when the
spinning is most profuse. In immature and abnormal eggs,
however, they often produce a perceptible diminution of the
blastomeres, and in such cases segmentation is usually un-
equal instead of equal, the third furrow producing four
micromeres and four macromeres. Subsequent division pro-
ceeds on the same plan, but the eggs are so weakened that
they seldom reach gastrulation. In this egg, as in the
Echinoderm, there is thus a marked difference between
normal and abnormal filose phenomena, as emphasised by
G. F. Andrews (5). Such abnormalities are of little use in
explaining normal cleavage, but may contain valuable sug-
gestions. Finally, we may note that these abnormal activities
are frequently carried so far that the egg spins out the entire
substance of the blastomeres, and goes to pieces during the
first segmentation.

This first cleavage, therefore, occupies about fifteen minutes,
and is followed by an interval of rest lasting ten or twelve
minutes.

This interval is occupied in the various phases of karyo-
kinesis; the nuclei of the two blastomeres divide, the halves
separate and take a position at either end of the vertical
diameter of each blastomere, where they can be seen under a
low power.

The second cleavage groove then appears at right angles
to the first, and divides the egg horizontally into four
blastomeres. ‘These are not spherical, although they appear
so when viewed from the side (fig. 52). If the egg be rolled
between cover-glass and slide, the blastomeres are seen to be

HABITS, ETO., OF CEREBRATULUS LACTEUS. 147

really egg-shaped or ellipsoidal masses lying side by side,
with the polar bodies still attached to the first cleavage
groove (fig. 53). When they flatten together an open space
is often left in the centre as in the Echinus egg (fig. 52).

If the surface of the blastomeres bordering this opening
be examined under a high power considerable filose activity
is revealed. One spin-thread starts from a papilla on the
side of a blastomere, and runs diagonally across to an ad-
jacent blastomere. Several other fine threads can be seen
radiating from the summit of the papilla, but they could not
be followed across (fig. 52). Another thread crosses from
one blastomere to the one opposite it, and makes a sharp
bend or elbow halfway across, very similar to the bends
figured for the star-fish blastula and the Hchinus four-cell
stage in the paper just referred to (5). The third thread
visible at this level proceeded out a little way from the re-
maining blastomere, and then turned abruptly and ran down
diagonally to an adjacent blastomere.

This central open space is subsequently obliterated by the
flattening of the blastomeres. ‘The polar bodies continue
their filose activity, remaining attached to one side of the
first furrow. In fig. 43 both bodies are seen to be bipolar,
but the two poles of the first body are unlike.

One consists of a large but short and blunt process from
whose tip and sides fine threads are given off, while the other
is made up of a simple bunch of radiating threads, each of
which starts from the body itself. Another blunt process
projects toward the second polar body, and forms part of the
connecting band between the two. Short fine threads also
radiate from this process.

The second segmentation occupies not more than eight or
ten minutes, and is followed by a rest of five minutes.

The third segmentation is vertical, and divides the egg into
eight equal blastomeres. Subsequent segmentations take
place more slowly than the first two, and the blastula stage is
reached in about fifteen hours. During the second and third
segmentations the egg elongates again, each time at right

148 CHAS. B. WILSON. ~

angles to the plane of cleavage, and since the first three
planes are in the three dimensions of space the successive
elongations restore the sphericity of the egg. -During the
flattening together at the close of the third segmentation
there is a twisting to one side, whereby the four upper
blastomeres come to lie over the grooves between the lower
four, i.e. the cleavage is spiral (fig. 54).

A change now takes place in the relative activity of the
polar bodies ; the first one has been more active hitherto, but
it now loses its marked polarity and begins to resume its ori-
ginal spherical form. One of its poles has already been re-
placed by a bunch of radiating filose threads, and the other
one now disappears gradually until the only remaining signs
of activity are occasional spinnings from various points on
the surface.

The second body, on the contrary, increases in activity ;
the processes at either end enlarge, and the filose spinning
increases proportionally. The band of protoplasm connecting
it with the egg changes continually in size and contour, and
occasionally a lump or swelling appears near the centre of
this band, looking like a third polar body. But it soon dis-
appears. The two figures given (44, 45) show the relative
activities in late stages of cleavage, and they also show that
the chromatic substance is affected by these activities.

In the first figure the chromatin appears in the form of
grains scattered through the body ; in the second figure it has
been gathered into a nuclear-like mass near the centre, whose
size and shape change under the influence of the spinning.

This change of the chromatic substance under the influence
of filose activity in the polar bodies corresponds well with the
changes in position, size, and shape of the chromosomes in
the nucleus during karyokinesis under the influence of the
spindle activities, and is another evidence of the close rela-
tion between the two. We have no means of knowing how
far they may agree in detail, but they are worthy of note as
showing that the filose activities have a tendency in the
same direction as those of the segmentation spindle.

HABITS, ETC., OF CEREBRATULUS LACTEUS. 149

A segmentation cavity appears very early, but not quite
in the eight-cell stage as described by Barrois for Lineus
Gesserensis (7).

As would be readily inferred, the first two blastomeres are
easily shaken apart when joined only by the narrow isthmus,
and the same is true of the four- and eight-cell stages.

The experiments of Morgan and others upon frogs’ eggs
at once suggested that blastomeres separated in this way
might develop into larve. Accordingly experiments were
made with the most satisfactory results. Even if the egg-
membranes were broken in the shaking and the blastomeres
set free, they segmented as though nothing had occurred,
and developed into larve similar in all respects to those
reared normally, except that they were only half as large, or
even smaller in the case of isolated blastomeres of the four-
and eight-cell stages.

Summary.—l. The axis of first segmentation is prede-
termined in the ovary at a very early stage of develop-
ment. It extends from the point where the egg-cell is
originally attached to the wall of the ovary, diametrically
across the egg to a point where the polar bodies subsequently
appear.

2. The ripe ovum is spherical. Segmentation is total and
equal; the first three cleavage planes occupy the three
dimensions of space, the second being horizontal. The
first segmentation occupies fifteen minutes, and is followed
by a period of rest lasting ten or twelve minutes. The second
occupies not more than ten minutes, followed by a rest of
five minutes.

Subsequent divisions proceed regularly but more slowly, and
the blastula stage is reached at the end of the fifteenth hour.

3. The polar bodies remain attached to each other and to
the egg through segmentation, and continue their filose
activities.

All evidence indicates that the point at which the second
body is attached to the egg remains constant. It appears at
the bottom of the first cleavage groove, then changes, as the

150 CHAS. B. WILSON.

groove deepens, to the side of that blastomere which first
passes into the four-cell stage. After the blastomeres have
been appressed it remains a short distance from the bottom
of the groove. This distance increases with subsequent
segmentations, until at the close of segmentation it appears
near the centre of the external surface of one of the cells. °
These changes of position without change of identity enable
us to determine—

a. That the egg possesses no surface membrane, but has an
ectosarce similar to that of the amceba.

b. That the original ectosare contributes but slightly to
the covering of the cleavage grooves, the larger portion of
that covering being a new structure.

c. That after appression a portion of this new ectosarc
remains exposed along the lines of cleavage, and increases in
relative width as segmentation progresses.

d. That gastrulation begins at the inferior pole, and the
axis of first cleavage becomes the future dorso-ventral axis
of the pilidium, and later of the adult (18).

4, The blastomeres show vigorous spinning activities during
early segmentation. While the polar bodies are coming off,
and immediately after the separation of the second one,
numerous spin-threads appear on the surface of the egg just
beneath the bodies. A papilla is formed on either side of
the first cleavage plane, and from its summit spin-threads
radiate outwards, some of them connecting with those from
the poles of the first polar body, and re-establishing vital
connection between the two. Both papille and spin-threads
disappear before segmentation begins.

5. Papillee are also formed on the sides of the cleavage
grooves, from which spin-threads extend to adjacent blasto-
meres and aid in appression. These are easily seen in the
first groove, less easily in the second, and can hardly be
distinguished in the eight-cell stage. These threads are con-
tractile, and during the first cleavage, when the blastomeres
are almost separated, their contraction produces a perceptible
movement,

HABITS, EVC., OF CEREBRATULUS LACTEUS. 151

6. The blastomeres may be entirely separated during early
segmentation, with the result that each one produces a per-
fect undersized pilidium.

Conclusions.—Recent investigations (3 and 5) have dis-
closed in living eggs of Echinoderms, Annelids, and Molluscs
activities similar to those just described, and filaments which
were probably of the same nature were found in preserved
egos of Amphioxus and the Amphibia. The first observer of
these activities (5) interpreted them as establishing the physio-
logical continuity of the blastomeres during cleavage, and all
subsequent investigations have only emphasised this inference.

Our first conclusion, therefore, reiterates the same truth :

1. The spin-threads connect the blastomeres and
prevent any physiological separation during seg-
mentation.

Few eggs undergo more complete separation of the blasto-
meres than those of Cerebratulus, but when most distinctly
separated they retain their physiological unity by means of
numerous cytoplasmic commissures. Evidently these spin-
threads are portions of the internal protoplasm which have
flowed out to the exterior, and are formed in the same way
as the filose pseudopodia of Radiolarians and the larger
pseudopodia of amcebee.

We should expect to find them, therefore, as suggested
(3), “high roads for the passage of living substance” be-
tween the blastomeres, and between them and the polar
bodies. And under specially favourable circumstances the
actual movement of granules along certain threads may be
seen. The current runs now outward and again inward, as
in a Radiolarian’s pseudopod.

Hence in those filaments which reach from one blastomere
to another, and remain for any length of time, there would
be a greater or less transference of living material. Seg-
mentation in such eggs cannot be regarded as a separation
of the egg substance into independent “cells,” but becomes
rather a differentiation of different portions of the same unit
mass for different purposes,

152 OHAS. B. WILSON.

2. If spin-threads are outflows of internal proto-
plasm, their activities must be similar to those in
the interior of the egg—a conclusion reached from other
material by G. F. Andrews (4).

One of the activities of the spin-threads is a streaming
movement of their more liquid contents. Unfortunately the
blastomeres are so opaque that we cannot see whether there
is a corresponding internal flowing of the protoplasm, but it
hardly seems possible that the former could exist without
the latter. Such streamings of the egg protoplasm have
been witnessed by Erlanger (21) in the living eggs of several
small Nematodes which are transparent enough to show it
distinctly.

In each end of these eggs alternately the protoplasm moved
from the poles to the equator, but as soon as the equatorial
groove appeared the streaming turned inward at the groove
and then backward toward the pole. After the first seg-
mentation similar streamings appeared in the blastomeres.
These movements were vigorous enough to distort the cleavage.
spindle, and Erlanger concluded that the whole of the egg,
spindle and astral rays included, is always plastic and fluid,
though the rays are more viscid than the remainder. Blunt
pseudopodia were formed on these nematode eggs at various
points, especially near the edge of the cleavage groove, but
no spin-threads were noticed.

The observation of such phenomena in transparent eggs
furnishes a strong presumption in favour of their occurrence
in opaque eggs, particularly in connection with such vigorous
external movements.

3. The spin-threads and other cytoplasmic con-
nections assist materially in appression, and proba-
bly in other movements of the blastomeres.

The spin-threads possess a contractility of sufficient
strength to move the blastomeres, and there can be no doubt
that they assist in drawing them together after segmentation.

They produce visible motion after the first cleavage, but
not in any succeeding stage, because the physical conditions

HABITS, ETC., OF CEREBRATULUS LAOTEUS. 153

are not the same. But it is not unreasonable to suppose
that the filaments formed in such stages really do assist in
appression, even if we cannot see any motion. A similar
function has been pointed out for the connecting filaments
formed in Hchinoderm eggs (5). It seems probable also that
something of this sort produces the spiral movement during
the third segmentation. We must admit that some portion
of the internal protoplasm possesses contractility, or we are
again driven to the improbability that the protoplasm which
streams outward to form the spin-threads is radically different
from that which remains inside the egg, and that the change
takes place at the ectosarc. We thus see that all the facts
and inferences to be derived from the visible filose activities
give support on the one hand to the hypothesis of fibrillar
contractility (van Beneden, 9), and on the other to the ex-
planation by means of streaming or osmotic movements of
the fluid portions of the protoplasm (Biitschli, 12). Neither
of these views can well be excluded in face of the testimony
here presented.

It seems equally impossible to escape the conclusion that
both are correct, so far as the existence of the forces which
they advocate is concerned. May it not be that we are to
look for a full explanation not to either one of them alone,
nor to any other single hypothesis already advanced, but
rather to a compromise, including at least several of the
principal ones ?

G-ASTRULATION.

Ciliation of the Larva.—As soon as the blastula stage
is reached cilia appear upon the external surface of the cells,
and the embryo begins to rotate slowly about a vertical axis.

The displays of filose spinning already given by the polar
bodies and the blastomeres incline me to the view recently
expressed (4) that cilia owe their origin to similar activities.

During segmentation both polar bodies and blastomeres
were sending out spin-threads, which often traversed spaces

154 CHAS. B. WILSON.

of considerable width. What more natural than that this
same activity should manifest itself at the close of segmen-
tation in spinning out these cilia? Evidently they cannot be
extrinsic in their origin, but must be intrinsic. Various names
have been applied to them, but I would suggest that the
term filature expresses better the actual facts in the case—
i. €. a spinning out into threads of filose processes.

These cilia vary greatly in length, the majority of them
being far longer than those ordinarily given in published
drawings (see 4, p. 72). Furthermore they do not end
abruptly at a definite distance from the cell surface, but
terminate in fine processes similar to the terminations of the
spin-threads from the polar bodies. I have ventured to
represent these cilia in one drawing as they really appear
(fig. 8), and I believe that such figures reveal their true
nature.

Such a relation between spin-threads and cilia may be
taken in evidence to explain the origin of motion in the
latter.

The band of strong cilia around the edge of the oral sur-
face are probably the ones first developed. At the close of
segmentation there is a well-defined differentiation of cells
into ectoderm and entoderm. The former are considerably
the smaller, and are more or less cubical in shape, while the
latter are elongated into well-defined cylinders (fig. 69).

During the blastula stage the egg maintains a position in
which the entoderm cells occupy the inferior pole, while the
ectoderm cells occupy the superior hemisphere and the upper
part of the inferior one. The lower surface becomes some-
what flattened previous to gastrulation, and it is in the ecto-
derm cells bordering this flattened area that cilia are first
seen (fig. 5).

The difficulty lies in proving that these cells maintain their
original position through gastrulation.

Formation of the Gastrula.—Toward the close of the
twentieth hour the large entoderm cells at the inferior pole
turn inward and upward, The flattened area around this

HABITS, ETC., OF CEREBRATULUS LACTEUS. 155

invagination becomes the oral surface, while that which is
for the present the superior portion of the embryo is the
aboral surface. ‘These correspond to the terms “ sub-
umbrella” and “ umbrella,” as used by Salensky (45). The
opening in the centre of the oral surface—the blastopore—is
the only opening into the invaginated entoderm. It is per-
manent, and functions as both mouth and anus during the
life of the larva, and is probably transformed into the mouth
of the adult as in other species, a new anus being formed.
The entire inner surface of the entoderm is covered with cilia
as soon as they appear on the ectoderm. The cilia around the
edge of the oral surface are much larger and longer than
elsewhere on the pilidium, and form what is known as the
pre-oral ring, which corresponds with those on trochophore
and turbellarian larve.

At this period the larva consists of a single outer layer of
cubical ectoderm and an inner layer of invaginated columnar
entoderm, also single. The space between these—the body-
cavity—is filled with a colourless, transparent, gelatinous
liquid.

Invagination is thus embolic, and the first stage in the
formation of the pilidium is accomplished.

The Apical Plate.—As soon as invagination becomes
distinct the embryo falls over on its side. At the same time
a slight depression appears near the centre of the aboral sur-
face (fig. 8), which is saucer-shaped at first, but becomes
markedly cup-shaped in later development. It never lies
exactly at the centre, but always a little anterior to it on the
median line.

For this reason it marks the first appearance of bilateral
symmetry in the embryo, which has hitherto preserved a dis-
tinctly radial form (cf. Korscheldt and Heider).

In the centre of the depression there is developed what at
first sight appears to be, and what was long mistaken for, a
single very strong flagellum. It is really a bunch or tuft of
flagella, twenty to thirty in number, which are nearly always
held firmly together. The depression, the apical plate, is

156 CHAS. B. WILSON.

made up of ectoderm cells much smaller than the average, and
elongated at right angles to the surface. In its formation the
cubical epithelium becomes columnar and invaginates into
the body-cavity as a thimble-shaped papilla. As invagina-
tion proceeds the columnar cells become wedge-shaped, with
their bases toward the body-cavity, and, withdrawing a little,
leave a depression at the centre of the papilla, which furnishes
the requisite support for the flagella. The latter arise singly
from the inner ends of the wedge-shaped cells, and are
wholly unlike the rowing flagella possessed by so many larve,
never being used for locomotion. They are rather enlarged
cilia, soft and very flexible, and they originate, so far as can
be determined, like the cilia, by a spinning out of the proto-
plasm from within the ectoderm cells. Consequently they
are sensitive, and serve as tactile organs of considerable
delicacy and power.

The Change from Radial to Bilateral Symmetry.
—It has just been stated that the apical plate is eccentric in
position. .

This first appearance of bilateral symmetry is quickly
emphasised by an elongation of the embryo parallel with the
eccentricity, and the long diameter thus determined becomes
the longitudinal axis of both larva and adult. In later
development the entodermal invagination is elongated along
this same axis, but in one direction only, i. e. away from the
apical plate.

This completes the differentiation, and we are able to dis-
tinguish anterior and posterior, dorsal and ventral, right and
left, and the second stage in the formation of a pilidium is
complete.

Such a transition from radial to bilateral symmetry is of
interest in its bearing on phylogeny. Embryologists gener-
ally agree that several of the largest groups of Metazoa show
enough resemblance in their larva] development to warrant
the conclusion that they are all descended from a common
ancestral form. These groups include Annelids, Molluscs,
Rotifers, Gephyreans, Nemerteans, and possibly others,

HABITS, BETC., OF CEREBRATULUS LAOCTEUS. 157

There have been several attempts to arrive at an idea of
their ancestral form, but the way is beset by so many difficul-
ties that the attempts agree in few particulars. These few,
however, are significant, for it is conceded that the archetype
must have been very simple, that it possessed radial symmetry,
and probably approached closely to a uniformly ciliated gas-
trula, with a rounded aboral surface and a flattened oral
surface, in the centre of which was situated the mouth.
Around the edge of the oral surface was a ciliated ring, pos-
sibly innervated.

Even in these meagre details we recognise almost an exact
description of our Cerebratulus larva, which is, like that of
many Nemerteans, developing through a pilidium.

The only noteworthy difference is the presence in the
pilidium of the apical plate with its bunch of flagella, which
forms a well-developed sense-organ. But in several impor-
tant respects the pilidium larva is less highly developed
than any of the others mentioned. This is especially seen in
the form of the alimentary canal, in the absence of an anus,
and in the lack of any true nervous system. In these par-
ticulars it approaches the ancestral type more closely than
any existing larva, and in consequence the manner in which
it changes:from radial to bilateral symmetry becomes of
interest.

The flattening of the inferior pole and the establishment
of the gastrula invagination leads to the fixing of a
structural axis passing vertically through the mouth, with
the whole body arranged radially around it. But the next
step is not an elongation of the aboral surface and the for-
mation of an anus there, as assumed for the ancestral
metamorphosis.

It is rather an unequal elongation of the oral surface,
whereby the portion in front of the mouth forms the pre-oral
lobe, while that behind the mouth develops into the trunk
and forms an anus.

Thus the aboral surface retains its relative position
and becomes the dorsal surface of the Nemertean.

158 CHAS. B. WILSON.

The Escape from the Egg Membranes.—Cilia have
now developed over the entire external surface of the larva,
and as soon as it falls upon its side the rotary motion which
they produce presses the aboral surface against the membranes.

This elongates the latter into an ellipsoidal form, and bends
the tuft of flagella at a sharp angle near their base.

By continued rotation this sharp angle is driven against
the membranes forcibly enough to bend them outward in a
shallow dent (fig. 6). This keeps the sharp angle in position,
and it soon bores its way through the membranes (fig. 7).

The bunch of flagella is then straightened out, tearing the
edges of the rent still more, and some of the liquid which
filled the membranes escapes. This causes them to collapse,
and they fall against the rotating embryo, whose strong
motion quickly tears them in pieces, leaving the larva free.

This is the second and probably the most critical period in
the life of the embryo. Of those reared from artificially
fertilised eggs fully one third fail to escape from the mem-
branes, and normal embryos fare no better, since 35 per
cent. of those under observation perished inside the mem-
branes. When we reflect on the apparent ease with which
the sperms penetrated these same membranes we are
impressed with the delicacy of the apical flagella. Hatschek
has noted in the Annelid HEupomatus cruciatus that the
cilia pierce the membrane when they first appear, and it
would seem as if the latter was not as tough as in Cerebra-
tulus (Korscheldt and Heider, p. 173).

We find examples of both dextral and sinistral rotation,
with a large majority in favour of the former.

The rapidity of rotation and the time at which the larva
escapes also vary greatly. If unable to escape at the proper
time the continued rotation reacts upon the larva and
tears asunder the cells of which it is composed.

In consequence a ragged bunch of cells may often be seen
rotating in the midst of a loose mass of individual cells
which have been separated from it, the whole enclosed in the
original membranes. Or sometimes the membranes give

HABITS, ETC., OF CEREBRATULUS LACTEUS. 159

way at the last moment, and the bunch of cells is set free
rotating slowly.

Tue PILIpium.
Habits.

Locomotion.—The larva always moves with the aboral
surface ahead, as seen in fig. 8. Locomotion is accomplished
wholly by the cilia, particularly the band of large cilia
around the edge of the oral surface. Their combined action
results in a uniform and quite rapid forward motion, and
there is also a continuance of the old rotary motion, though
the axis of rotation is now horizontal instead of vertical.

The life of the larva seems to depend on its constant
motion, and if one is stopped for any length of time it goes
to pieces, the cells being torn asunder by a vigorous contrac-
tion of the body muscles. This renders any extended
examination of living specimens very difficult. Nevertheless
it was determined to examine these larve alive for the reason
that they become beautifully transparent immediately after
gastrulation, so that internal development can be followed in
detail.

After repeated trials it was found that the best method of
keeping the larvee quiet was to place them in a drop of salt
water under a supported cover-glass, and then paralyse them
with cocaine, or better with chloral hydrate. If just the right
amount (which must be very small) be used the larva will
remain stationary for a long time, with the cilia moving
slowly and without any contraction of the muscles. In this
condition camera lucida drawings are easily made, and the
morphology which follows has been obtained entirely
in this way from a study of living larve.

Use of Apical Flagella.—In swimming the long
flagella are stretched far out ahead, and move round slowly
in front of the advancing embryo. So completely are these
flagella controlled by the apical muscle that they are capable

160 CHAS. B. WILSON.

of movements in every possible direction and of great
delicacy.

The larva is often seen advancing toward some object, or
toward the outer surface of the drop of water in which it is
swimming, and when still distant from it half its own
diameter it turns suddenly, sometimes even completely
around, and escapes coming in contact with it. Hither,
therefore, the flagella are sensitive enough to recognise an
object when still some distance from it, or they are prolonged
beyond their visible tips, the prolongations being invisible
under the power used.

In view of what we have already seen we must conclude
that the latter is far the more probable.

The flagella also serve as a steering apparatus, like the
tuft of cilia at the apical pole of many Actinian larve, and
the apical plate in its earlier origin is sometimes traced back
to such a rudder-like tuft of cilia (cf. Korscheldt and
Heider).

Here in the pilidium we find both apical plate and apical
tuft, the latter retaining its original function of steering.

Farther than this the flagella take no part in locomotor
movement, but are pre-eminently tactile, and constitute
practically the only sense-organ possessed by the larva.

Their importance is shown by the comparatively complex
structure of the apical plate from which they arise, and by
the attachment to it of the largest and best developed
muscle in the whole pilidium. And yet they are exclusively
a larval organ, and take no part in the formation of the adult
worm, being thrown off with the epithelial covering.

Sometimes there are two apical tufts instead of one as in
the figure here given. In such a case the plate is broadened
and thickened, but there is only a single apical muscle,
developed in the usual way.

Pilidiums are sensitive to light, always congregating on
the side of the aquarium nearest the source of light, but they
show no response to ordinary sounds.

Food.—The pilidium swims at the surface of the water

HABITS, ETC., OF CEREBRATULUS LACTEUS. 161

until its transformation into the adult form. During this
time its food supply is varied. It consists chiefly of very
small particles of the refuse material always found in sea
water; in no instance were living organisms found in the
digestive organs. The cilia on the inner surface of the ento-
derm keep up a constant current inward through the single
opening at the centre of the oral surface, and another inter-
mittent current outward. The former runs along the anterior
side of the invagination and carries with it the food particles.

In the stomach the current becomes more or less rotary,
carrying the food round rapidly until all that is digestible
has been absorbed. The refuse material is caught from time
to time in the intermittent current and carried outward along
the posterior side of the invagination, and discharged by the
same opening at which it entered. This single opening, the
blastopore, thus functions as both mouth and anus. Often
the refuse is thrown to quite a distance by a vigorous flap
of the lappets, the larva at the same time being driven
forward with a jerk. After the primitive intestine becomes
differentiated into stomach and cesophagus the opening
between the two is strongly constricted by a sphincter muscle,
which operates exactly like the pyloric sphincter in our own
bodies.

Morphology of the Pilidium.—As the larva elongates
in passing from radial to bilateral symmetry two enlarge-
ments appear, one on either side of the blastopore, growing
downward from the border of the oral surface. These form
ear-like lappets, diverging slightly from each other, and the
larva has now assumed the helmet form of a typical pilidium.
This species is slightly elongated antero-posteriorly, and the
lappets are quite thick (figs. 9, 10).

The whole pilidium is built up of the three primitive
tissues nearly unmodified. The ectoderm forms the skin, the
entoderm the intestine walls, while the mesoderm fills the
space between. The gradual development and transforma-
tion of these three tissues takes place very slowly, and affords
a good opportunity for studying the tissues themselves and

voL. 43, PART 1.—NEW SERIES. i

162 CHAS. B. WILSON.

their derivatives. The entire surface of the pilidium is
covered with cilia, those along the edge of the helmet being
thicker and stouter than elsewhere, since the pre-oral ring of
the gastrula is continued around the edge of the lappets.
By a contraction of the muscles with which the lappets are
soon supplied a peculiar flapping movement is produced, very
similar to that of a pecten’s shell when swimming, and this
seems to be of assistance in locomotion. The lappets are
also quite sensitive, though they are always carried behind
the larva when swimming, and hence cannot be of as much
service as the flagella.

The larva has now become perfectly transparent, so that
the details of internal development can be easily watched.

The Primitive Intestine.—At first no differentiation is
possible in the invagination which forms the primitive
intestine. It is composed throughout of a single layer of
cells which are longer and narrower than those of the
ectoderm, and which bear cilia upon their internal faces.
These cilia are very delicate, and are manifestly the result of
filose action. As soon as the embryo elongates, however,
the invagination bends over toward one end, the future
posterior end of the embryo (fig. 10). This flexed end
approaches close to the wall of the pilidium, enlarges, and
assumes a spherical shape.

A slight constriction appears at the point of flexure, and
we can now distinguish an cesophageal portion which
extends from the mouth to the point of constriction, and a
stomach portion, the enlarged inner end. Histological
examination reveals a clear distinction in structure also
between the two (cf. p. 188).

As the stomach enlarges the aboral surface posterior to
the lappets becomes larger than the corresponding anterior
portion.

Consequently it rounds over somewhat where it joins the
oral surface, and the latter sinks in as a shallow saucer-
shaped depression, approaching closely to the wall of the
stomach. But the two never meet as in the trochophore larva,

HABITS, ETC., OF CEREBRATULUS LACTEUS. 163

At first the cesophagus is cylindrical and of the same dia-
meter throughout, but later it is enlarged laterally and con-
stricted around the mouth as well as at its junction with the
stomach. This dilation produces a lateral elongation of the
mouth opening, which becomes more and more elliptical.

Both cesophagus and stomach walls are covered with
muscle-cells. In the former muscles are formed, which, by
inflation and constriction, assist in taking in and ejecting the
food, and probably also in breathing. For in view of the
fact that the adult breathes through these same cesophagus
walls, and that a strong current of water is kept flowing
over them by the action of their cilia, it seems rational that
oxygenation should take place here in the larva. On the
stomach the muscles do not seem strong enough to render
much assistance in churning the food, but at the constrictions
they develop into strong sphincter muscles. The one around
the mouth in other species becomes the lp muscle of the
adult worm.

The simplicity of this primitive intestine is the more re-
markable when we reflect that it is the only portion of the
pilidium which is preserved in the adult Nemertean.

Mesoderm Formations.—These include mesenchyme
cells and the whole musculature of the larva. In no other
larva with which I am acquainted can the development of
the muscular system be followed so easily and in such detail.

This is due to a combination of peculiarly favourable cir-
cumstances. First the pilidium walls are as clear as glass,
enabling the single mesenchyme cells to be seen through
them from the very beginning. ‘Then the mesenchyme cells
themselves are large, and as soon as they become polar can
be readily distinguished from all others. Finally the develop-
ment into muscle is so gradual, and the ultimate tissue is so
simple, that a single cell may be followed for some time after
it has united with others, and has begun to function as
muscle.

Consequently the development of the muscle system of the
pilidium larva is one which discloses something of the real

164 CHAS. B. WILSON.

nature of muscle tissue as to its origin and functions. And
yet, so far as known, the present is the first attempt to work
out this development in any pilidium. Even Biirger (13), in
his excellent monograph, can only say, “ The mesoderm gives
rise to the gelatine, the star-shaped cells lying in it, and the
muscle fibrille. The latter have doubtless developed out of
the star-shaped cells.”

Origin of the Mesenchyme Cells.—Metschnikoff has
shown in the genus Lineus (35) that the mesenchyme origi-
nates from large entoderm cells around the border of the inva-
gination, and the same is true in Cerebratulus. When
gastrulation first begins, scattered mesenchyme cells separate
from the entoderm in the angle between the invagination
and the oral surface, and sometimes along the convex in-
vagination itself (fig. 72).

Unlike Lineus, there are here two kinds of these cells,
readily distinguished by their size (fig. 73).

The larger ones are given off first, and for a little while are
the only ones to be seen; then both kinds come off together
indiscriminately. Wewill call them macromesencytes and
micromesencytes respectively.

At first the macromesencytes are rounded in form, and
float about freely. At this time they are difficult to discern
against the background of ectoderm, but they soon become
branched, and are then easily distinguished from all other
tissue.

The branches hinder their freedom of motion enough to
show that the liquid in which they float is gelatinous rather
than watery, and they gradually become fixed in position and
function as muscles. While free they exhibit amceboid
movements, similar to those of blood leucocytes; then the
cell puts out slender, blunt pseudopodia, which change their
position, size, and shape, like those of an amceba. But they
quickly become fixed in position, and are then spun out much
farther, with tips so attenuate that it is impossible to tell
where they really do end.

They continue to increase in length until they finally touch

HABITS, BTO., OF CEREBRATULUS LAOTEUS. 165

the body-wall, or that of the intestine, to which they fasten
themselves. They then function as muscle by contracting
and pulling together the parts to which they are attached.

While they remain free no trace of striation can be seen
in the cells, but we have to remember that we are looking at
them through the pilidium wall, which, however clear it may
be, is not perfectly diaphanous. Hence there might exist a
‘fine striation without our being able to detect it. But as
soon as the cells become fixed in position granules appear
in the cell cytoplasm, and the thread-like branches: become
distinctly fibrillar in structure. No amitotic division stages
were found, as noted by Montgomery in the free mesenchyme
cells of the adult worm (87). Occasionally the branches of
two cells anastomose before becoming attached, and may be
seen to contract, at first irregularly, but later rhythmically,
hike similar cells in opisthobranch Gastropods (cf. 49). After
the cell becomes fastened to the pilidium walls these rhythmic
pulsations cease, and the cells become regular muscles, con-
tracting only when stimulated. ‘The muscles developed from
these macromesencytes are considered under the following
heads:

1. Retractor Muscle of the Apical Plate.—This is
usually the first muscle formed. Soon after the intestine has
turned down posteriorly mesenchyme cells are seen along the
apex of the bend beneath the apical plate (figs. 8,9). One
or more of them become stationary at about the position of
the future muscle.

It then sends out spin-threads which reach, and fasten
themselves to, the apical plate, the wall of the intestine, and
sometimes the aboral wall of the pilidium. Other cells in
floating about come in contact with these fixed ones, and are
arrested. They in turn send out processes to the apical
plate, the intestine, or the wall of the pilidium, according
to their position. Other processes are then sent out which
anastomose with those already formed, making a coarse net-
work (fig. 11).

The strands of the network are then pulled around by the

166 CHAS. B. WILSON.

formation and attachment of new processes and the letting
go of old ones, until they are approximately parallel (fig. 14).
The strands then come together and fuse into larger ones,
while the cell bodies, which now contain little beside the
nuclei, travel slowly along the strands, and seem finally to he
on the under surface of the apical plate, or upon the wall of
the intestine.! :

The removal of the nuclei leaves the strands in the condi-
tion of clear muscle-fibres (fig. 15). Occasionally the body of
a cell is all used up in forming processes, and then the nucleus
may be flattened slightly and retain its place in the fibre.

The muscle is thus fastened first to the wall of the intes-
tine (fig. 15), and is so figured by Verrill (46, p. 417).

But it soon divides and passes down on either side of the
intestine, and fastens to the anterior border of the lappets,
separating into fine fibres at the point of junction (fig. 15).

In a good light the fibres.may be seen to be attached to
delicate papille, which are raised slightly from the inner
surface of the ectoderm cells. The muscle is now no longer
connected with the stomach, for a strong contraction draws
the apical plate down until it almost, if not quite, touches the
stomach wall. ‘This is the longest, the largest, and the
strongest muscle in the pilidium, as well as the first one to be
formed, and itis chiefly through its violent contractions that
the cells of the pilidium wall are pulled asunder under
irritation.

In such a case, after the muscle has shortened and thick-
ened all its structure will allow, a still further shortening
is produced by the assumption of a corkscrew shape,
exactly as in the contractile stem of Vorticella. This is
the only means by which the muscie can draw the apical
plate down far enough to touch the stomach wall.

2. Interparietal Muscles.—The first of these consists
of a single cell, which lodges usually just in front of the
apical plate (fig. 17). Long processes are developed at

1 Mrs. G. F. Andrews kindly gave me this final location of the nuclei, from
her own observations upon Cerebratulus.

HABITS, ETC., OF CEREBRATULUS LACTEUS. 167

either end of this cell, which extend across and fasten to
the pilidium wall.

At first the fibres are simple, and contraction results in
pulling the pilidium walls closer together; but in later
development they may be joined by other fibres, and the
motion then becomes compound, producing a general shrinking
of the body-walls.

There are also one or more cells which sometimes accom-
pany the large retractor muscle, but whose fibres only extend
from the apical plate to the wall of the intestine (fig. 15).

These are insignificant in size and strength, and probably
play an equally insignificant part in the motions of the larva.

Finally, there are muscles, consisting mostly of single cells,
which run from different points of the pilidium wall to that
of the intestine (figs. 13, 15). These seem to develop wherever
the cell is finally lodged, and their contraction produces move-
ment in both the walls to which they are attached.

Being formed from a single cell, the body of the cell
usually remains visible for some time, but later it may travel
along to one wall or the other, and leave a simple strand
stretched across the intervening space. Here, then, we
witness the transformation of a cell, at first independent of all
the rest of the larva save the liquid in which it floats, into a
muscle-fibre fixed at both ends, and capable of contracting
under stimulus.

3. Gisophageal Muscles.—There are two sets of these :

a. Gastro-csophageal, consisting of delicate fibres
running diagonally between the adjacent walls of cesophagus
and stomach.

Most of them consist of a single macromesencyte and its
branches; they do not anastomose, and are so far apart that
they cannot fuse (fig. 14). They are not formed until the
seventh or eighth day, and are used chiefly in the dilation
(antero-posterior) of the esophagus. They are weak, and
scarcely worth a separate classification.

b. Post-cesophageal, a thin muscular sheet, triangular
in shape, connecting the oral ectoderm with the posterior

168 CHAS, B. WILSON.

wall of the cesophagus along its mid-line. Sometimes the
sheet is divided, and attached along either side instead of in
the mid-line.

In fig. 14 several mesenchyme cells are seen just fastened
in place and putting out processes; in later development (fig.
15) the individual cells have coalesced into a broad triangular
sheet of muscle. One side is attached to the cesophagus from
the mouth nearly to the stomach; a second side is attached to
the ectoderm from the mouth back to the angle between the
lappet and the oral surface; while the third side, somewhat
concave, hangs free. The bodies and the nuclei of the indi-
vidual cells composing this muscle can be seen for a long
time as swellings irregularly distributed through the muscle
sheath.

The cesophagus is ordinarily dilated laterally, so that the
contraction of this muscle dilates it antero-posteriorly, and,
when followed by a contraction of the muscular walls of the
cesophagus itself, aids materially in generating the currents
of water which take in the food particles and eject the waste
matter.

The motion thus produced corresponds also to the breathing
movements in the adult worm, and it does not seem rash to
suppose that the larva also breathes in this way, and that the
muscle under discussion is one of the muscles of respiration.

4, Circumoral Muscle.—This consists of a_ strong
muscular ring which surrounds the mouth, and of muscle
bands which extend backward and forward from the ring to
the edge of the lappets (fig. 15). The elliptical mouth ex-
tends from the centre of one lappet to that of the other, and
across the space intervening between the lip and the anterior
and posterior angles of the lappets numerous muscle-fibres
are developed. At the side are usually found large cells,
which send out fibres reaching to the extreme anterior and
posterior walls of the pilidium, as well as shorter lateral ones.
These cells are well developed, and their contraction tends to
draw the borders of the oral surface in toward the centre.
The ring around the mouth is developed into a well-defined

HABITS, ETC., OF CEREBRATULUS LACTEUS. 169

sphincter, whose contraction can almost close the mouth
opening. These ring and band muscles form an excellent
support for the attachment of the other muscles, notably
those of the lappets and apical plate, and for the support of
the primitive intestine. In fact, they serve as a sort of
centre for the whole body musculature; and this seems an
important use under normal conditions. They also restore
the cesophagus to its normal shape after dilation, and, next to
the apical muscle, are the most strongly constricted under
irritation. They have the advantage of being situated close
to the source of supply of mesenchyme cells, and in other
species they are retained during metamorphosis, and develop
into the strong lip muscles of the adult Nemertean.

The second kind of mesenchyme given off by the entoderm
consists of much smaller cells than the first. Very soon
after the appearance of the large cells these smaller ones
may be seen coming off in the same locality. The difference
in size is shown in fig. 9, and is not diminished by subsequent
growth. These micromesencytes do not float about like
their larger predecessors, but remain close to the body-wall
(fig. 14).

They do move about, however, in a curious way.!

After being warped about in different directions they each
settle down at some particular spot, and become permanently
attached, to form the fifth group of muscles. Conn, in his
study of Thalassema (17), found two kinds of mesenchyme
cells, one of which became distinct muscles, while the other
consisted of branching cells of the same origin, but more like
“connective tissue corpuscles scattered at random in the
body-cavity, but quite close to the body-wall. In the older
larvee they are more abundant, and unite to form quite a
continuous layer.” Their similarity in origin, form, and
position to the micromesencytes of Cerebratulus, and the
fact that they are ultimately joined in a continuous layer,
suggest that they may have a similar function.

'In a verbal communication Mrs. G. F. Andrews states that she has seen
these cells warping themselves about by means of protoplasmic processes.

170 GHAS. B. WILSON.

5. Parietal Muscles.—These consist of single micro-
mesencytes scattered over the entire inner surface of both
ectoderm and entoderm (fig. 16). Their fibres anastomose
freely with one another and with the interparietal muscle-
fibres, and form an irregular network, which is attached
closely to the inner surface of the pilidium walls. Their con-
traction may assist the motion produced by other muscles, or
may produce a local shrinkage something after the manner
of the so-called “ goose-flesh”’ on our own skin under the
influence of cold.

Certain of the cells on the walls of the cesophagus are
arranged with more or less regularity transversely, and form
constrictor muscles. It is possible that some of the macro-
mesencytes assist in the formation of these constrictors, since
some of them are attached in the right position and after-
ward disappear, but the matter could not be definitely deter- .
mined.

These muscles are usually incorporated in the tissue of
the intestine wall during subsequent development, and
together with many of the macromesencytes which have
remained isolated are transferred to the adult Nemertean
during metamorphosis, as has been shown in other species
by Biitschli (11). All the remainder of this quite intricate
musculature disappears.

The parietal network forms a layer separating the ecto-
derm from the central gelatine, and assists the other muscles in
pulling asunder the cells of the pilidium walls under irritation.

We thus see in the musculature of the larva which is
temporary, and the bulk of which disappears during meta-
morphosis, a curious foreshadowing of the function of dis-
memberment which is so prominent in the adult.

6. Lappet Muscles.—These muscles necessarily await
the development of the lappets, and are thus the latest to
appear, coming about the eighth day. The cells from which
they originate are almost of the same size, and become
stationary close to the cilia ring, forming a row just inside
the cilia cells (fig. 81).

HABITS, ETC., OF CEREBRATULUS LAOTEUS. 171

Each cell then sends out a process which develops into a
muscle-fibre. There are two sets of these lappet muscles.

a. Radial Muscles of the Lappets.—These consist of
fine fibres extending radially from the edge of the lappets to
the circumoral ring (fig. 15). They are all.of the same size,
and are arranged at approximately equal distances from one
another, each micromesencyte forming but a single fibre.

They anastomose little, if at all, but each fibre at the edge
of the lappets divides into from two to five fibrils.

Hach fibril is attached to a fine mammillary process on the
inner surface of a cilia cell, which looks like a miniature of
one of the papillary muscles of the chorde tendinez of the
human heart. These muscles correspond to the “large
muscles of the lappets” noted by Salensky in Lineus (45),
but differ from them in that they do not radiate from a
single point.

There is a small group (fig. 15) radiating from the same
point as in Salensky’s figure, but it does not constitute an
important part of the muscle. The actual process of attach-
ment by which one of the muscle fibres is fastened to the
pilidium wall is difficult to watch, but it is easy to determine
in these lappet cells that the muscle fibrils are connected
with the cytoplasmic reticulum. When one of the threads
sent out by a mesenchyme cell comes in contact with an ecto-
derm cell it first flattens out a little on the surface of that
cell.

The substance of the thread, which is actively moving
protoplasm, then fuses with the ectosare of the cell, and
through it becomes attached to the reticulum in the interior.
That it is certainly thus attached is seen upon the disruption
of the pilidium under irritation, when muscle fibrils may
sometimes be found with a single ectoderm cell still attached
to either end.

These of course were interparietal muscles. If now the
cells be held in position by pressure of the cover-glass the
muscle-fibre will go on contracting for some time.

By increasing the power used until the reticulum of the

172 CHAS. B. WILSON.

cell becomes visible, it can be seen that the threads of this
reticulum are apparently continuous with the fibrils, and
that every contraction of the latter pulls the reticulum
adjacent to the point of attachment out of place. As soon
as the contraction ceases the reticulum returns to its former
shape. The ground substance of the cytoplasm is appa-
rently affected only as it is compelled to accommodate itself
to the changes of shape in the reticulum. he cytoplasm of
the thread, therefore, at first fuses imperceptibly with that
of the cell to which it is being attached, but on becoming
fibrillated the fibrils attach themselves to the. more sub-
stantial reticulum.

These radiating fibres are very contractile, and may often
be seen to assume the same corkscrew shape as the apical
muscle when excessively contracted. They serve to produce
the opening and closing motion of the lappets already de-
scribed.

b. Locomotor Muscles of the Cilia Rows.—These
correspond closely to the circumoral muscles in origin and
mode of development. The cilia rows le at the junction of
the aboral and oral ectoderm where the mesenchyme cells
originate.

When the lappets first start some of these cells are taken
along with them in their downward growth, and retain their
original position just inside the cilia cells (fig. 11). From a
portion of these micromesencytes are developed the radial
muscles just described, but most of the fibres unite to form a
muscle strand running along inside the cilia cells. This
strand increases as the lappets enlarge, and unites at either
end with the circumoral muscle (fig. 77). Its fibres divide into
fibrils which terminate in the individual cells of the cilia rows.

The strand can be plainly seen in all longitudinal or dia-
gonal sections which cut through the edge of the lappets,
and it may be detected in specially perfect cross-sections,
where of course the fibres appear as dots. These are the
only muscles of the larva distinctively for locomotion (cf.

p. 159).

HABITS, ETC., OF CEREBRATULUS LAOTEUS. 178

But not all the mesenchyme is employed in the manu-
facture of muscle. Certain of the macromesencytes do not
develop processes or exhibit amceboid movements, but divide
and subdivide actively. As fast as they are used up in this
way others take their place, so that they may always be found
scattered about in the gelatine. In the living larva they
appear yellowish, and they always stain more deeply than
the muscle cells. Evidently they are the source of the gela-
tine itself, and probably correspond to the isolated cells which
Biitschli showed (11) were transferred to the adult Nemer-
tean. If their development could be followed in this species
it would doubtless be found that they share the same fate.

Summary.—l. The mesenchyme originates from large
entoderm cells situated at the junction of entoderm and
ectoderm.

2. Its cells are of two kinds, called macromesencytes and
micromesencytes respectively, the former being several times
larger than the latter. At first macromesencytes are given
off alone, then both kinds appear together. From micro-
mesencytes are developed the parietal and lappet muscles ;
from macromesencytes all the other muscles of the pilidium.

3. In this muscle development both kinds of cells may
either remain single, forming delicate fibres, or may anasto-
mose into a complex network, or several cells may fuse into a
larger strand.

4, At first the macromesencytes float about freely and
exhibit slight amoeboid changes of form. Then they put
out slender pseudopodia branches which arrest their motion.
These pseudopodia do not show any contractile movements,
but only a streaming motion of granules and cytoplasm.
They are lengthened until they come in contact with some-
thing to which they can be fastened.

5. As soon as they are fastened the structure changes from
that of normal cytoplasm into typical fibrillated muscle.
This is accompanied by a corresponding change in activity ;
the streaming ceases, and the fibrils become contractile and
function as muscles,

174 CHAS. B. WILSON.

6. Prior to fixation two macromesencytes sometimes anas-
tomose with the same change in structure and activity, but
they pulsate more or less rhythmically instead of contracting
in the ordinary manner. As soon as they fasten to the larval
walls, however, the pulsations cease, and their subsequent
contractions are like those of other muscles.

7. The cytoplasm of the macromesencytes is exhausted in
the formation of branches. The nucleus retains its original
position until the muscle-fibres are formed; it may then
become flattened and incorporated in situ in the muscle
tissue, but more frequently it migrates along the fibre to the
pilidium wall.

8. The micromesencytes do not float about, but remain
close to the pilidium walls, upon which they creep along to
their final position by means of “ protoplastic activities.”

9. The ends of the thread-like pseudopodia sent out by
both kinds of mesenchyme, on coming in contact with a cell
of the pilidium wall, at first fuse with its ectosarc, but after
they become fibrillated the fibrillee are attached to and are
apparently continuous with the cell reticulum.

10. The ectoderm and the entire musculature of the larva,
except the parietal muscles of the intestine and a few isolated
macromesencytes, disappear during metamorphosis.

11. When irritated the larval muscles contract violently
and pull in pieces the walls of the pilidium, thus showing
the same tendency toward dismemberment that is manifested
in the adult.

Conclusions.—The simple fact that circumstances com-
bine so favourably for a study of the musculature in the
pilidium would give it considerable interest. And when we
remember how closely it approaches in primitive simplicity
to the archetype of several of the largest groups of Inverte-
brates, it becomes doubly interesting, and we are enabled to
draw several suggestive conclusions.

1. The muscles of the pilidium are metamor-
phosed pseudopodia.

The pseudopodia of the mesenchyme cells are the exact

HABITS, ETO., OF CEREBRATULUS LACTEUS. 175

counterpart of the spin-threads sent out from the polar
bodies and from the blastomeres during segmentation. Some
at least of those spin-threads were contractile, while these
mesenchyme spin-threads actually develop into typical
muscles. The same thread which at first exhibits a visible
streaming of its cytoplasm afterwards becomes contractile
and shortens just as visibly.

2. The transition from pseudopodium to muscle-
fibre consists essentially in a striation or fibrilla-
tion of a portion of the cytoplasm, and the
gradual assimilation of the non-fibrillated re-
mainder.

Such a striation of cytoplasm is nothing new. It has been
observed by Flemming and many others in the living cells
of cartilage, epithelium, connective-tissue and other animal
cells, in which the fibrille form a sort of loose network. It
has been seen by G. F. Andrews in living cells of many
Protozoa and Metazoa (4, 5), where it was plainly correlated
with contractile activities. In preserved material striation
is Shown in the pancreas cells of Necturus (51) and in the
beautiful preparations of ciliated cells from Anodonta and
Cyclas (20).

But the very best examples are those given by Heidenhain
(24) of the radiating system of fibres in the leucocytes or
wandering cells of the salamander, and by Zimmermann (52)
of similar radiating systems in the pigment cells from the
epidermis of fishes. Here the cytoplasm not only becomes
fibrillar, but both authors believe it to represent the con-
tractile elements by means of which the cells change their
form and creep about (51).

In all these cases the cytoplasm becomes fibrillar inside
the cell, but that ought not to exclude the possibility of its
repeating this tendency outside the cell in the pseudopodia.

Conn states (17) that in the mesoderm formations of
Thalassema the cells which are budded off from the entoderm
near the blastopore do not become true wandering cells, but
are immediately transformed into muscles. Each muscle is

176 CHAS. B. WILSON.

unicellular, consisting of a cell body with a distinct nucleus,
and with muscle-fibres extending from it in two directions.
Here, then, the branches become fibrous as well as the body
of the cell.

When the streaming movement necessary to the sending
out of spin-threads is stopped by contact with something, the
threads at once become striated. At first the striz are
hardly visible and some distance apart, but they rapidly
increase in size and distinctness until finally they occupy
nearly all the muscle strand. It seems probable that this
increase in fibrillation consists largely of an assimilation of
the non-fibrillated portion. During this transformation the
whole cell body is often conveyed out into the incipient
muscle strand, where it is converted into muscle fibrille.

3. Fibrillation appears to start in a rearrange-
ment of the cytoplasmic reticulum, whereby its
threads, instead of forming an irregular network,
become parallel.

We can see how a streaming of the cytoplasm along the
spin-thread pseudopodium would help such an arrangement,
for the fibrillee are longitudinal. Several other facts support
such an origin of muscle fibrillation. The familiar radiating
fibrillee in the asters of dividing cells, when followed out-
ward, can be traced into the cytoplasmic reticulum, and
they are so continuous with its threads that it is impossible
to tell where the fibril ends and the reticulum begins, or vice
versa.

Again, the muscle fibrille under favourable conditions can
be followed into the cell to which they are attached, and
terminate there in the cytoplasmic network, with which they
are so completely fused, that once more it is impossible to
tell where one ends and the other begins. Furthermore,
in a study of columnar epithelium it may often be noticed
that the cytoplasm in the outer zone of the cell has been
arranged in more or less parallel fibrille along the long
diameter of the cell. No reticulum is visible in this part of
the cell except that formed by the fibrille. In figures of

HABITS, ETC., OF CEREBRATULUS LACTEUS. 177

ciliated epithelium given by Englemann (20) the fibrille are
almost perfectly parallel, and not only correspond exactly in
number with the cilia, but are just opposite to them. We
can hardly escape the conclusion that the external cilia are
prolongations of the internal fibrille. If so, then the
difference between cilium and muscle-fibre is that the former
consists of a single fibrilla, while the latter is made up of
several bound together.

Finally the fibrille, when they first appear, are not upon
the surface of either cell or spin-thread, but are distributed
throughout their substance. Hence they cannot be regarded
in any sense as “surface secretions,” but are more inti-
mately associated with the cytoplasmic structure. If not
formed by a rearrangement of the reticular network, they at
least bear the same relation to the remainder of the cytoplasm
that such threads would.

4. The first contractions of the changing pseu-
dopodia represent the combined action of all
cytoplasmic energy, pulling in a single definite
direction instead of in different directions.

Originally the cytoplasm possesses perfect internal mobility,
and its first movements are amceboid in character. Then
follow spinnings, or the putting out and withdrawal of pseu-
dopodia in different directions. Some of these become per-
manent, and the whole contractile energy of the cell is then
concentrated upon them. As the cytoplasm is pushed out
farther and farther it becomes more and more limited in
the direction of its movement. And when the pseudopodia
are once fastened and fibrillation has begun it can move only
in one direction, along’ the axis of the pseudopodia.

The energy which is at first expended in different direc-
tions, some of them antagonistic to others, becomes concen-
trated along the axis of the pseudopodium. Hence the »
resultant cytoplasmic contractions gain as much in strength
and rapidity as they lose in mobility, and become capable of
producing what we call a muscular contraction. The initial
contractions are noticeably weak, and the intervals between

voL. 43, part 1.—NEW SERIES. M

178 CHAS. B. WILSON.

them are longer than in later development, but they do not
stop here.

5. The muscle-fibres thus formed increase both
in size and contractile power through exercise.

When first formed the fibres are simply fibrillated pseudo-
podia of single mesenchyme cells, hence all their substance
must come from this one cell. And yet there is a perceptible
increase in the size of the fibres, even after the entire body
of the cell has gone out into them. This increase is most
rapid and hence most apparent in those muscles which are
most often contracted, e. g. the apical and circumoral
muscles.

The increase in strength is admirably shown in the lappet
muscles, each of whose single fibres scarcely shortens at all
in its initial contractions. But after several days’ develop-
ment it can contract so vigorously as not merely to shorten,
but also to assume the characteristic corkscrew shape.

6. Fibrillation and the consequent change from
potential to kinetic contractility occurs only after
the pseudopodium has attached itself to something
outside the cell.

We found the same thing true of the spin-threads sent out
by the polar bodies and the segmenting blastomeres.

The simplest explanation of this fact is that the constant
movement of the cytoplasm in pushing out the spin-thread
prevents contraction, but as soon as spin-thread or pseudo-
podium becomes attached the flow ceases, fibrillee appear, and
contraction ensues.

It is worthy of note that the nature of the contractions
depends somewhat on the kind of attachment. When
attached to a cell of the pilidium wall the contractions in .
the resultant muscle-fibre are like those of ordinary muscle.
When threads from two cells anastomose without becoming
attached to anything else, they contract in rhythmic pulsa-
tions like cardiac muscle.

This rhythm is shown even better in the muscles formed
from mesenchyme cells in the veliger larve of certain nudi-

HABITS, ETC., OF CEREBRALTULUS LACTEUS. 179

branch molluscs, and has been described elsewhere (49).
Finally, in those cells where the cytoplasm becomes fibrillar
without forming any connection at all outside the cell, as
in ciliated epithelium, the contractions are in the form of
rhythmic vibrations.

Sometimes it happens that the pseudopodia from two cells
which have anastomosed, and have been contracting in
rhythmic pulsations, become attached later to the pilidium
wall. In such a case the nature of the contractions also
changes, and they cease to be rhythmic, and become in all
respects like ordinary muscle.

Histology.

Methods.—A pilidium larva is nearly as hostile to preser-
vation as the medusa to which it is often compared. After
a trial of many different preservatives the best was found to
be platinum chloride, used either alone or in equal parts
with acetic acid. Corrosive acetic can also be recommended,
but is exceptionally difficult to wash out of the tissues.

For staining, Delafield’s hematoxylin, followed by eosin or
Orange G, gives good differentiation.

Blastula.—A segmentation cavity appears very early, and
increases until the blastula consists of but a single layer of
cells surrounding this cavity. These cells are elongated at
right angles to the surface of the blastula, and vary greatly
in size and shape, so that they project unequally into the
central cavity, making the inner surface very rough.

The cells at the inferior pole are longer and narrower than
the superior ones, so that there is thus early a differentiation
into ectoderm and entoderm. The nuclei are spherical,
comparatively large and uniformly granular; they are nearly
always excentric in position, being much nearer the external
end of the cell. The cytoplasm contains so much yolk
material as to be opaque at first, but clears rapidly and
becomes transparent enough to show the central cavity
before gastrulation (fig. 55).

180 CHAS. B. WILSON.

This cavity contains one or more loose cells which have
been given off from the entoderm cells where they join the
ectoderm. The loose cells are mesenchyme, and so far as
observed none of them originate from the ectoderm.

Gastrula.—As soon as the cells begin to multiply for
invagination and the formation of the intestine they become
equal in size, and their inner ends are evened. The mesen-
chyme still continues to come off from the entoderm, and the
latter is now clearly differentiated from the ectoderm (fig. 69).

The ectoderm consists of a single layer of epithelium.
On the aboral surface it is a pavement epithelium made up
of cubical cells, which are small at the superior pole, grow
larger toward the equator, and then grow smaller near the
border of the oral surface. By a comparison of different
stages we find that the cells around the apical plate are the
first to become transparent (fig. 70). Large clear spaces
like vacuoles appear in these cells; but they are not empty
spaces, for they react to stains in the same way as the
gelatine which fills the body-cavity. These spaces gradually
extend down toward the oral surface, until by the time the
lappets are formed they can be found in every cell of the
aboral ectoderm (fig. 73). In individual cells they are at first
spherical, but quickly elongate parallel with the ectoderm
surface. Then together with the cells they increase in area
at the expense of their thickness, leaving the nuclei em-
bedded in cytoplasm on the inner border of the cells.

The oral ectoderm is much thicker, and composed of
cylindrical cells in which no clear spaces can be seen. These
cells have larger nuclei than those in the aboral ectoderm,
and are more active. From them are developed the lappets,
the cilia row which surrounds the edge of both oral surface
and lappets, and the invaginations which form the amnion
and the ectoderm of the adult Nemertean (18).

The entoderm is much thicker than the ectoderm, but
consists of a single layer of cells, cylindrical in form and
similar to those of the oral ectoderm. They are more
irregular in shape and overlap somewhat, so that they give

HABITS, HT'C., OF CEREBRATULUS LACTEUS. 18]

in some sections the appearance of a double layer. ‘They
retain their large blastula nuclei, and are quite active; they
also remain opaque, with the exception of those on the
anterior wall of the cesophagus, which are cleared in a
different manner.

Tae PILipium.

The aboral ectoderm, which was a pavement epithelium
in the gastrula, has now become typically squamous, the
cells being strongly flattened. As the cells increase in
superficial area they lose the rounded form of the gastrula
and become more and more angular, until they finally assume
an irregular four- to six-sided form. The number of the cells
remains practically constant, except at the border of the oral
surface.

These facts, compared with the increase of clear areas in
the gastrula, show that the pilidium grows largely, if not
wholly, by a flattening of the aboral cells. The aboral “ um-
brella,” as it is called, is simply a protective covering for
the young embryo, to be thrown away at the time of meta-
morphosis. Hence its cells, when once formed, remain until
final dissolution, simply flattening more and more to give the
necessary increase in size. Sometimes the flattening is carried
so far in the old pilidium that the body of the cell becomes
thinner than the nucleus, and the latter bulges out into the
body-cavity. Meanwhile the clear spaces have increased until
they occupy nearly all the cell, leaving but little cytoplasm
around the nucleus (fig. 72). The thinning and clearing of the
ectoderm, combined with the ‘‘ glass-clear ” gelatine between
ectoderm and entoderm, gives the pilidium great trans-
parency. But we should not expect the individual cells to
be held together very firmly, since they are in contact only
along their thin edges, and hence they pull asunder easily
under irritation.

But the oral ectoderm takes an active part in the develop-
ment of the future Nemertean, and it is the only ectoderm
except the apical plate that shows karyokinetic figures,

182 CHAS. B. WILSON.

Its cells are smaller, but the nuclei are about the same
size, and not being flattened the cells are held together
more securely.

Both oral and aboral ectoderm are thickly covered with
fine cilia, which are longer and stouter at the apical plate
and the cilia row.

The apical plate is an invaginated thickening of the
ectoderm. Metschnikoff regarded it “als eine Art indif-
ferentes Gehirn,” and the fibres going from it as a nerve
commissure (36).

Biitschli later maintained that the fibres must be regarded
as muscle, and that it was doubtful whether this plate really
was the central organ of the nervous system (11).

Salensky considered Metschnikoff’s assumption probable
from a morphological standpoint, since the apical plate can
be regarded as the homologue of that formed in the trocho-
phore larva. But he added that it was unlike this in its
simpler form, and it takes no part in the formation of the brain,
and hence must be regarded as a rudimentary plate (45). He
then gives the first, and, as far as known, the last account of the
histological structure of the plate, closing with these words :
“The question as to the nature of the bundle (of fibres con-
nected with the plate) must be settled by a study of the
development history of the plate and the fibres.” We have
just given the development history of the fibres, and have
found that they are undoubtedly muscle. The plate originates
in two or more cells found near the apical pole in a median
section of a blastula. These cells stain more deeply than the
others, and occasionally show karyokinetic figures (fig. 69) ;
otherwise they are like the remaining ectoderm cells. But
they divide and subdivide actively at right angles to the
surface of the blastula and form a group of cells, one layer
thick, a little anterior to the pole on the median line.

The cells are cylindrical in form, and of the same diameter
throughout. Their nuclei are small at first, but become
relatively large as the cells diminish, and are always situated
close to the inner end of the cell. Their cytoplasm is more

HABITS, ETC., OF CEREBRATULUS LACTEUS. 183

compact, and hence not quite as transparent as the rest of
the ectoderm. These plate cells divide slowly but steadily,
while the surrounding ectoderm cells do not divide at all;
hence they are pressed inward as an invagination into the
body-cavity. Neither this invagination nor that of the intes-
tine is quite symmetrical, the former being inclined toward
the anterior end of the pilidium, and the latter toward the
posterior end. As they invaginate the plate cells become
smaller and more conical or wedge-shaped, the bases pointing
inward toward the body-cavity (fig. 70). These changes pro-
ceed slowly, so that for two or three days the plate projects
but slightly into the central cavity as a rounded swelling
(fig. 71). But it grows more and more convex, until it ac-
quires a thimble or nipple shape by the sixth day.

In preserved specimens the apical muscle is usually con-
tracted, and the thimble is pulled out into a cone, and by
comparing longitudinal with transverse sections it can be seen
that the cone is nearly symmetrical in outline (cf. figs. 72
and 73).

A median section shows that the plate is composed of small,
crowded conical cells, whose bases show through the ecto-
derm as distinct circles (fig. 74). The cells are shorter around
the margin and longer toward the centre, each containing a
large spindle-shaped nucleus and sometimes a highly refrac-
tive nucleolus.

Both cells and nuclei stain more deeply than the adjacent
ectoderm, showing a corresponding difference in their ac-
tivity.

The outer ends of the nuclei are usually pointed, and some-
times prolonged into a short, slender, thread-like process
(fig. 76); but the inner ends are not so prolonged as Salensky
has figured for Lineus (45), they are well rounded and plump.

A muscle fibril connects with the inner end of each of the
cells near the centre of the plate, but not with those toward
the margin. These fibrils can be seen to enter the plate
through the structureless membrane which covers the whole
plate, and are lost sight of in the substance of the cytoplasm.,

184 CHAS. B. WILSON.

If Salensky’s figure be compared with this one of Cere-
bratulus (fig. 76) it will be noticed that in his figure (45,
fig. 8) the plate is pulled in so far that fully one half the
depression is formed of aboral ectoderm. Whether this is a
normal condition in Lineus I am unable to say, but I have
found a similar condition in Cerebratulus only when the
apical muscle was strongly contracted. If this were true in
Lineus the separate fibrils of the apical muscle when con:
tracted would naturally pull out the inner ends of the cells
to which they were attached, and may have produced the
apparent prolongation.

The long stout cilia arise in bunches of four to six, from
near the centre of the outer ends of the cells (fig. 76). Near
the border of the plate they are finer and shorter than at
the centre.

In life they are gathered into a compact bundle, looking
like a single large flagellum, but in preserved specimens
they are always separated and usually broken (cf. figs. 10
and 74),

Both surfaces of the plate are covered by a fine structure-
less membrane, through which cilia and muscle fibrils pass.

There are usually in the angle between the plate and the
ectoderm mesenchyme cells whose function is unknown.
They are yellowish or sometimes dark brown in colour in the
living larva, and no processes can be detected coming from
them. It is possible that they may be of the same nature
as the so-called “ eye-spots ” of annelid larvee, but this could
not be determined.

The plate, therefore, is developed from ectoderm cells,
which are smaller in size, less transparent, bear longer and
more sensitive cilia, and whose nuclei are relatively larger,
but which are otherwise undifferentiated from the remaining
ectoderm.

None of these things necessarily indicate the formation of
anything like nervous tissue; and, in view of the fact that
the fibres connected with the plate are undoubtedly non-
nervous in origin, structure, and function, we must conclude

HABITS, ETC., OF CEREBRATULUS LACTEUS. 185

that in Cerebratulus there is no nervous tissue in or
connected with the apical plate. This plate differs
from its morphological homologue in annelid larvee in being
made of a single layer of undifferentiated ectoderm instead
of containing two layers more or less modified. In the tro-
chophore the plate contains nervous tissue, which afterwards
develops into the supra-cesophageal ganglion of the adult ;
in the Cerebratulus pilidium the plate is thrown away with
the rest of the aboral ectoderm during metamorphosis, and
we find no trace of any nerves at all.

The Cilia Rows.—These are rows of large cilia running
along the border of the oral surface and around the edge of
the lappets, and they are the chief organs of locomotion.

We can distinguish ectoderm wall cells, cilia cells, and a
well-developed locomotor muscle system (fig. 75).

The ectoderm cells are similar in structure to other ecto-
derm, but increase in thickness as they approach the cilia
cells, those on the aboral surface being thicker than the oral.

Hence the upper border overhangs the under one, and acts
as an organ of protection to the cilia, as noted by Salensky
(45).

The cilia cells are smaller than the wall cells, and are
arranged in three rows between the latter along the extreme
edge of the lappets. They are wedge-shaped or pyramidal,
with their apices turned inward. Their cytoplasm and nuclei
-are similar to those of the apical plate, and they are also
covered on the exterior with a_ structureless membrane,
through which the cilia pass. ‘he latter are distributed over
the entire surface of the three rows of cells, but show a ten-
dency to gather in bundles. On the inner surface of the cilia
cells, and between the wall cells, lie the locomotor muscles (fig.
77). These consist of a strong muscle band and of scattered
mesenchyme cells. The band is made up of stout parallel
fibres, which originate in the mesenchyme cells and termi-
nate in the cilia cells (fig. 79). It is continuous with the
circumoral muscle both anteriorly and posteriorly (fig. 77),
and stains deeply with hematoxylin. It thus corresponds

186 CHAS. B. WILSON.

exactly with the ring of muscle fibres and cells which lie at
the base of the ciliated band in the trochophore larve.

The cells are small, and look like micromesencytes, except
that they are mostly unipolar, the single pole giving off a long
fibrous process. The row of cells can be followed from the
lappets around the border of the body, but the muscle band
blends with the circumoral muscle, and loses its indi-
viduality.

This locomotor muscle lies in exactly the position assigned
by Salensky to the “ nerve-ring ;” fig. 79 is almost identical
with fig. 4 of his description. But we have called them
muscle for the following reasons. Salensky states that ‘the
nerve-ring passes along the cilia row, and thus becomes the
homologue of the nerve-ring in the annelid larve described
by Kleinenberg.” But he fails to note that Kleinenberg also
describes a ring of muscle cells at the base of the ciliated cells,
which is used by the larva in locomotion (29).

If either of these sets of locomotor apparatus are to be
developed in so primitive a larva as the pilidium at the ex-
pense of the other set, the presumption is strongly in favour
of the muscle. We would scarcely expect to find the nerve
well developed, as Salensky claims, and no trace whatever of
the muscle.

Again, borax carmine, orange G, and hematoxylin stain
these fibres exactly the same as the other pilidium muscles,
and no difference is perceptible in their structure or texture.

Another proof is that the cells whence the fibres originate
are exactly like those from which the radial fibres arise.

It has never been doubted that the latter are anything but
muscle cells ; they, too, are unipolar or multipolar, as Salensky
claims for the “ nerve-cells,’ and his argument from form
would apply equally well to both. Finally, this strand is
continuous with the circumoral muscle (fig. 77), and if one
is nerve, the other must be also; but if we concede that the
circumoral ring is muscle, then the strand must also be
muscle.

These facts, no one of which, perhaps, is sufficient alone,

HABITS, ETC., OF CEREBRATULUS LACTEUS. 187

when taken together furnish strong evidence that the fibres
are muscle. Whether the strand also contains nerve-fibres
must remain an open question; none can be seen, and
pilidiums kept for days in water impregnated with methylene
blue showed no trace of coloration.

Anteriorly the cilia rows, in passing from the lappets to the
oral surface, invaginate in a large loop (fig. 82), which pro-
jects into the central cavity in the same manner as the apical
plate.

The two loops are composed of the same sort of cells as
the rest of the cilia rows, and appear undifferentiated. They
appear about the sixth day, and increase in size up to the
eighth or ninth day, after which they remain unchanged
as long as I have succeeded in keeping any larvaee—about six
weeks.

I believe these to be the first pair of invaginations which
are to form the adult Nemertean, but, of course, have been
unable to prove the matter.

The Intestinal Canal.—In the mature pilidium this is
composed of two parts, each consisting of a single layer, and
well differentiated. At first the intestine is composed through-
out of large cylindrical cells, but as soon as the inner end
begins to turn down posteriorly the constituent cells begin
to differentiate. Those onthe anterior and lateral walls of the
cesophagus flatten ont, increase in superficial area, and become
transparent in a very similar manner tothe aboral ectoderm.

But the process is not carried so far, and the cells never
lose their vitality. The flattening is not uniform, so that the
cells grow thinner from the stomach toward the mouth, where
they pass insensibly into the oral ectoderm.

The posterior wall of the cesophagus is thicker, its cells are
smaller in area, more cylindrical in form, and do not become
as transparent. They are also depressed along the mid-line
into a shallow groove (fig. 82), which forms a channel for the
food particles.

The stomach wall is thicker than that of the cesophagus,
its component cells are larger and less transparent, and are

188 CHAS. B. WILSON.

of two kinds, distinguished by the intensity with which they
are stained.

Wall-cells.—These are more numerous, are prismatic in
shape, and contain smaller nuclei. They do not stain very
deeply, and are evidently the true entoderm.

Gland-cells.—Between the wall-cells are others scattered
over the stomach, but most numerous at its anterior end
(fig. 80). They are larger than the wall-cells, and are flask-
shaped, with the narrow neck of the flask pointing inward,
while the rounded body contains a large nucleus. They stain
very deeply, and are evidently gland-cells as first stated by
Metschnikoff (33) and later by Burger (18), and not nerve-
cells as claimed by Salensky (45).

The inner surface of both stomach and cesophagus is
covered thickly with fine cilia, which are slightly longer in
the stomach than in the cesophagus. At the base of the cilia
is another structureless membrane, covering the whole inte-
rior of the intestine.

At the junction of stomach and intestine is the large
sphincter muscle already described. It allows free passage
of food particles when relaxed, but closes the opening entirely
when contracted. Since the muscles are usually contracted
in preserved specimens, it often happens that sections are
obtained which appear similar to those given by Hubrecht
(25) ; but watching the living larva for a few moments is
sufficient to do away entirely with any idea that the stomach
ends blindly at both ends. At about the sixth day a swelling
is noted on the superior wall of the stomach posterior to the
pyloric valve. This develops into a shallow evagination
whose walls are made up of cells smaller and more crowded
than the adjacent stomach entoderm. But this evagination
was carried no further in the oldest pilidiums reared, and so
its ultimate purpose could not be determined.

Summary.—l. A segmentation. cavity appears very early,
and increases until the blastula consists of a single layer of
cells elongated at right angles to the surface and surrounding
this cavity.

HABITS, ETC., OF CKREBRATULUS LACTEUS. 189

2. The ectoderm is a one-layered pavement epithelium,
made up of cubical cells on the aboral surface and cylindrical
cells on the oral surface. The entoderm is also one-layered
and made up of cylindrical cells, but it is thicker and more
opaque than the ectoderm, and its cells overlap considerably.

3. The aboral ectoderm remains constant after being
formed, and the increase in size is accomplished by a strong
flattening without cell division. This, together with a
gradual clearing of the cell protoplasm, gives the pilidium
great transparency.

4, The apical plate is an invaginated thickening of the
ectoderm, made up of conical cells whose bases turn inward
toward the body-cavity. The nuclei are pointed and some-
times prolonged into thread-like processes on the outer ends,
but are rounded and plump on the inner ends. The com-
ponent fibrils of the apical muscle connect with the imner
ends of all cells near the centre of the plate.

5. The long stout cilia which form the apical tuft arise in
bunches of four to six from the centre of the inner ends of
the cells, and in life are gathered into a central bunch which
looks like a single large flagellum.

6. The cilia cells, whence arise the large cilia running
along the border of the oral surface and around the edge of
the lappets, are arranged in three rows. The cilia them-
selves are given off in bunches from the outer ends of the
cells.

7. Just inside the cilia cells is a strong band of locomotor
muscle-fibres and scattered mesenchyme cells. A careful
study of their origin and development, the development of
the plate itself, its histological structure and staining, all go
to prove that both fibres and cells are muscle, and that there
is nO nervous tissue in the plate or connected with it.

8. The anterior wall of the cesophagus becomes partially
flattened and cleared in the same manner as the aboral
ectoderm, but the posterior wall retains its original thick-
ness. It is grooved along the mid-line to form a channel for
the food.

190 CHAS. B. WILSON.

9. The stomach walls contain numerous gland-cells, which
are flask-shaped, with the neck of the flask pointing inward.
The inner surface of both stomach and intestine is covered
with cilia, and at their junction is a large sphincter muscle
which controls the passage of the food particles and waste
material.

ADDENDA.

Since the foregoing went to the printer I have received an
article entitled ‘‘ Development of the Pilidium of Certain
Nemerteans,” by W. R. Coe.

This excellent paper discusses briefly the segmentation,
gastrulation, and pilidium stages in Micrura ceca, Cere-
bratulus Leidyi, and C. marginatus.

Together with the present paper it was practically finished
before either author became aware that the other was work-
ing upon the subject. The close agreement in the results
obtained is all the more gratifying in view of their entire
independence.

I wish briefly to mention the following points :

1. In segmentation C. lacteus transposes the second and
third cleavage planes of the other three species, making the
second horizontal and the third vertical. Otherwise the four
agree in all essential features of segmentation and gastru-
lation.

2. While Coe has not given the development of the apical
plate and the muscular system in detail, it is evident from
his drawings that this development in both cases is almost
identical with that here given. The arrangement of the
parietal muscles, especially in Micrura ceca, is somewhat
different from that in C. lacteus, as might be expected.
But the mesenchyme cells from which they are formed are
evidently smaller than those which form the other muscles,
and correspond to the micromesencytes in C. lacteus.

3. The statements in reference to the presence of nervous
tissue are wisely cautious, but it is easy to see that Coe does

HABITS, ETC., OF CEREBRATULUS LACTEUS. 191

not put much faith in Salensky’s interpretation (45). He
distinctly states (p. 253) that the so-called “ nerve-cells ” in
the entoderm “are obviously nothing but gland-cells, which
are partially filled with a deeply staining secretion and have
no sensory function whatever.”

In all four of these species, without exception, the fibres
connecting the apical plate with the oral ectoderm are mus-
cular in origin. Also the elements which Salensky describes
as nerve-cells and nerve-fibres are found to stain easily with
common muscle stains, while they do not differentiate at all
with methylene blue or any other distinctive nerve stain.
This should make us somewhat cautious in accepting the
apical plate of the pilidium as an exact homologue of that in
the trochophore larva of Annelids.

BIBLIOGRAPHY.

An excellent bibliography will be found in Biirger’s
monograph (138), which contains a brief abstract of every
paper mentioned. Only those papers are mentioned here to
which actual reference is made in the text.

1. Acassiz, A.—‘* The Embryology of Autolytus cornutus,” ‘* Boston
Journ. Nat. Hist.,’ vol. vii, 1863.

2. AnDrEws, HE. A.—‘‘ Activities of the Polar Bodies of Cerebratulus,”’
‘Archiv f. Eutwick.,’ Bd. vi, Heft 2, 1898.

3. AnDREWwS, E. A.—‘“Filose Activities in Metazoan Eggs,” ‘Zool.
Bulletin,’ vol. ii, No. 1, 1898.

4. Anprews, G. F.—“The Living Substance as such, and as Organism,”
‘Journ. Morph.,’ vol. xii, 1897.

5. Anprews, G. F.—“ Some Spinning Activities of Protoplasm in Star-fish
and Echinus Eggs,” ibid.

6. Brattiz.— On the Reproduction of Nemertes Borlassii (Lineus
longissimus),” ‘ Proc. Zool. Soc.,’ London, Part xxvi, 1858.

7. Barros, Jutes.—‘ Mémoire sur l’embryologie des Némertes,” ‘ Ann.
Se. Nat.’ (6), tome 6, 1877.

192 CHAS. B. WILSON.

8.

9.

10.

11.

12.

13.

14.

15.

16.

LP

“18;

19.

20.

21.

22.

23.

24.

25.

26.

van Brenepen, M.—‘‘ Recherches sur Ja Faune littorale de Belgique,”
‘ Mém. d.1’Acad. des Se. Belg.,’ tome xxxii, 1861.

vaN BENEDEN, #.—“‘ Recherches sur la Maturation de ’(Cuf, la féconda-
tion et la division cellulaire,” ‘ Archiv de Biol., tome iv, 18838.

Brenuam, W. B.—“ Fission in Nemertines,’’ ‘Quart. Journ. Mier. Sci.,’
vol. xxxix, 1896.

Bitscuir, O.—‘ EKinige Bemerkungen zur Metamorphose des Pilidium,”
‘ Archiv fiir Naturgesch., 1873.

Bitscuut, O.—* Vorlaufige Mittheilungen iber Untersuchungen betref-
fend die ersten Entwickelungsvorgange im befruchteten Ei von Nema--
toden und Schnecken,” ‘ Zeit. f. wiss. Zool.,’ Bd. xxv, 1875.

Bircer, Orto.—‘ Die Nemertinen des Golfes von Neapel,” ‘ Fauna u.
Flora d. Golfes v. Neapel,’ 221e Monographie, 1895.

Buscu, W.—‘ Beobachtungen tiber Anatomie und Entwickelung einiger
wirbellosen Seethiere,’ 1851.

Coz, W. R.—‘‘ On the Anatomy of a Species of Nemertean (Cerebra-
tulus laeteus, Verrill), with remarks on certain other species,”
‘Trans. Conn. Acad.,’ vol. ix, 1895.

Coz, W. R.—* The Maturation and Fertilisation of the Egg of Cerebra-
tulus,’’ ‘ Zool. Jahrb.,* Bd. xii, 1899.

Conn, H. W.—‘ Life History of Thalassema,” ‘Stud. Biol. Lab. Johus
Hopkins Univ.,’ vol. ili, No. 7, 1886.

Desor, E.—“ Embryology of Nemertes,” ‘ Proc. Boston Nat. Hist. Soc.,’
vol. vi, 1848.

Dieck, G.—‘‘ Entwickelungsgeschichte des Nemertinen,” ‘ Jenaische
Zeitschrift,’ Bd. viii, 1874.

Enetemann, IT. W.—* Zur Anatomie und Physiologie der Flimmer-
zellen,”’ ‘ Archiv ges. Phys.,’ Bd. xxiii, 1880.

von Ertancer, R.— Entwickelungsgeschichte des Nematoden,” ‘ Biol.
Centralb.,’ Bd. xvii, Heft 4, 1898.

GEGENBAUR, C.—‘‘ Bemerkungen tiber Pilidium gyrans, etc.,” ‘ Zeit.
f. wiss. Zool.,’ Bd. v, 1854.

Gace, S. H.—‘ The Life History of the Toad,” ‘ Teacher’s Leaflet,’
No. 9, Coll. Agric., Cornell Univ., 1898.

Heipennain, M.—‘‘ Cytomechanische Studien,” ‘Archiv f. Entwick.,’
Bd. i, Heft 4, 1895.

Husrecnt, A. A. W.—“‘ Zur Embryologie der Nemertinen,” ‘ Zool.
Anz.,’ 1885.

Husrecut, A. A. W.—‘‘ Contributions to the Embryology of the
Nemerteans,” ‘ Quart. Journ. Mier. Sci.,’ vol. xxvi, 1886.

27

28

29

30.

31.

32.

33.

34,
35.

36.

37.

38.

39.

40

41,

42

43

44

45

46

HABITS, ETC., OF CEREBRATULUS LACTEUS. 193

. Husrecut, A. A. W,—“ Report on the Nemertines,” ‘ Reports of the

Challenger Expedition,’ 1887.

. Kroun, J.—‘‘ Ueber Pilidium und Actinotrocha,” ‘ Miiller’s Archiv,’
1858.

. Kurinenzere, N.—‘‘Sull’ origine del sistema nervosa central degli

Annelidi,’”’ ‘ Mem. Accad. Lincei Roma,’ tome x, 1881.

Lrg, A. B.—“ La Spermatogenése chez les Némertiens, & propos d’une
théorie' de Sabatier,’’ ‘ Recueil zu Suisse,’ tome iv, 1887.

LEvCKART UND PacEnsTECHER.—‘“‘ Untersuchungen iiber niedere See-
thiere,”’ ‘ Miller’s Archiv,’ 1858.

Mark, EH. L.—*‘ Maturation, Fecundation, and Segmentation of Limax
campestris,” ‘ Bull. Mus. Comp. Zool.,’ Harvard College, No. 6,
1881.

McInrosu, W. C.—“ Notes on the Development of Lost Parts in the
Nemerteans,” ‘Journ. Linn. Soe.,’ vol. x, 1870.

McIntosu, W. C.—‘ Marine British Annelids, Nemertea,’ 1873-4.

Merscunikorr, H.—‘ Studien tiber die Entwickelung der Echinodermen
und Nemertinen,’” ‘Mém. Acad. Imp. Pétersbourg,’ series vu, tome
xiv, No. 8, 1870.

Merscuntkorr, H.—‘ Vergleichend embryologische Studien,” ‘ Zeit. f.
wiss. Zool.,’ Bd. xxxvii, 1882.

Monteomery, T. H.—‘ On the Connective Tissues and Body-cavities of
the Nemerteans, with Notes on Classification,” Spengel’s ‘ Zool.
Jahrb.’ (Anat. Abth.), Bd. x, 1897.

Mier, Jon.—‘ Pilidium gyrans,” ‘ Archiv fiir Anat. und Phys.,’
1847.

Miter, Jon.—“ Ueber verschiedene Formen von Seethieren,” ‘ Miller’s
Archiv,’ 1854.

. Ranponeu, H.—‘‘ The Regeneration of the Tail in Lumbriculus,”

‘Zool. Anzeiger,’ Jahrg. xiv, 1891.
ReniEr, St. A.—‘ Prospetto della Classe dei Vermi,’ 1804.

. SaBatier, A.—“ La Spermatogenése chez les Némertiens,” ‘ Revue Se.

Nat. Montpellier’ (3), tome ii, 1883.

. Satensky, W.—‘‘ Zur Entwickelungsgeschichte der Borlasia vivi-

para,” ‘ Biol. Centralb.,’ Bd. 11, No. 24, 1883.

. Satensky, W.—‘“‘ Recherches sur le développement du Monopora
vivipara,” ‘Archiv. de Biol.,’ tome v, 1884.

. Satensky, W.—* Bau und Metamorphose des Pilidiums,” ‘ Zeit. f. wiss.
Zool.,’ Bd. xliii, 1886.

. Verritt, A. E.—‘‘ The Marine Nemerteans of New England,” ‘Trans.
Conn. Acad.,’ vol. viii, 1892.

VoL. 438, PART 1.—NEW SERIES. N

194 CHAS. B. WILSON.

47. Watask, S.—‘ Studies on Cephalopods: I. Cleavage of the Ovum,”’
‘Journ. Morph.,’ vol. iv, No. 3, 1891.

48. Wuitman, C. O.—* The Embryology of Clepsine,’’ ‘Quart. Journ.
Micr. Sci.,’ vol. xviii, 1878.

49. Wison, C. B.—“ Activities in Mesenchyme Cells of Certain Larve,’
‘Zool. Bull.,’ vol. ii, No. 1, 1898.

50. Witson, i. B.—‘ Observations on the Early Developmental Stages of
some Polychstous Annelids,” ‘ Stud. Biol. Lab. Johns Hopkins Univ.,’
vol. ii, 1882.

51. Wuson, E. B.—‘The Cell in Development and Inheritance,’ The
Macmillan Company, New York, 1896.

52. Zimmermann, K. W.—“ Studien tiber Pigmentzellen, etc.,” ‘ Archiv f.
micros. Anat.,’ Bd. xli, 1893.

>

EXPLANATION OF PLATES 9—11,

Illustrating Mr. Chas. B. Wilson’s paper on ‘The Habits
and Harly Development of Cerebratulus lacteus
(Verrill).”

Key to LEtrters.

am. Apical muscle. ai. Anterior invagiuation. 6v. Blood-vessel. c.
Intestinal ceca. cc. Cilia cells. em. Circular muscles. com. Circumoral
muscle. e¢. Connective tissue. dvm. Dorso-ventral muscles. ec. Ectoderm.
en. Entoderm. ge. Gelatine cell. gic. Gland-cell. gr. Groove for food. im.
Interparietal muscle. Jam. Lappet muscles. dm. Longitudinal muscles.
fom. Locomotor muscles. o. Ovary. @. Gsophagus. pm. Post-cesophageal
muscle. s. Stomach. sc. Sperm mother-cell. ¢. Testis. we. Wall-cell.
yc. Yolk-cell.

PLATE 9.

Fie. 1.—Cerebratulus swallowing a Nereis five minutes after dismembering
the posterior half of its body. Photograph from preserved specimen, one
eighth life size.

Fic. 2.—Cerebratulus with regenerating papilla. Photograph from life,
one eighth life size.

HABITS, ETC., OF ORREBRATULUS LACTEUS. 195

Fie. 3.—Male (left) and female (right) Cerebratulus, the latter showing
normal anal papilla. Photograph from life, one eighth life size.

Fig. 4.—Cerebratulus with proboscis sheath cut open to show how the
proboscis is coiled when withdrawn. Photograph from preserved specimen,
one eighth life size.

All the remaining figures, with the exception of Nos. 11, 53, 54, and
59, have been drawn with a camera lucida on a Leitz microscope. The
magnification is indicated by giving the Leitz numbers of the eye-piece
and objective used. ‘The figures have then been reduced one half in
making the plates.

Fie. 5.—Gastrula, showing shape and arrangement of ectodermal cells and
beginning of cilia rows. 3 and 7.

Figs. 6 and 7.—Successive stages in the process of escaping from the egg
membranes. 3 and 3.

Fic. 8.—Gastrula just escaped from the membranes, thirty-eight hours old.
Cilia and flagella drawn the exact length seen. 1 and 7.

Fic. 9.—Larva forty-eight hours old, first stage in formation of apical
muscle. 1 and 7; tube drawn 60 mm.

Fic. 10.—Same, fifty-four hours old, second stage; side view.

Fic. 11.—Same, ninety-six hours old, third stage. Zeiss camera lucida,
magnified 575 diams.

Fie. 12.—Same, 108 hours old, fourth stage; end view. 1 and 7; tube
drawn 60 mm.

Fic. 13.—Same, 120 hours old, fifth stage ; side view, showing spipal muscle
attached to dorsal wall of cesophagus.

Fig. 14.—Same, six days old, sixth stage, showing apical muscle divided
and extending down on eitlier side of the intestine to fasten to the oral surface
anterior to the mouth. This figure shows also interparietal, post-cesophageal,
and circumoral muscles.

Fie. 15.—Same, ten days old, seventh stage. Apical muscle fully de-
veloped ; post-cesophageal muscle forming a triangular sheet ; radiating lappet
muscles weil developed.

Fie. 16.—Same, twelve days old; surface view showing parietal muscles.

Fic. 17.—Transverse interparietal muscle attached to apical plate, from
larva six days old. 1 and 7.

Fie. 18.—Eggs taken from ripe ovary and examined before they have
touched any water. 3 and 3.

Fic. 19.—Same after immersion in salt water three minutes.

Fig. 20.—A ripe, freshly laid ovum, unfertilised, showing membranes and
attachment protuberance. 1 and 7.

196 CHAS. B. WILSON.

Fic. 21.—Transverse section of a regenerating papilla very near its
posterior end, showing ventral grooves and beginning of the lateral nerve-
cords. land 3.

Fie. 22.—Same farther forward, showing lateral nerve-cords migrating
toward their normal position.

Fre. 23.—Same still farther forward; nerve-cords nearly in their normal
position, and circular muscles weil developed.

PLATE 10.

Fic. 23a.—Fertilised egg, showing flattening of the superior pole previous
to the giving off of the polar bodies. 1 and 7.

Fies. 24—36.—Maturation of the egg and formation of the polar bodies,
with the beginning of filose activities. 1 and 7, tube drawn 60 mm. These
drawings are all from the same egg, and were taken at the following intervals :—
11.05 a.m., 11.065, 11.08, 11.21, 11.216, 11.22, 11.228, 11.235, 11.24,
11.27, 11.28, 11.335, and 11.40.

Fic. 37.—A second egg, showing abnormal activities during completion of
the polar bodies.. 1 and 7; tube drawn 60 mm.

Fig. 38.—A third egg with unequal papille and slightly abnormal activities.
Magnification the same.

Fig. 39.—Egg with polar bodies pressing against the inner membrane and
bulging it outward. 1 and 7; tube drawn 60 mm.

Fic. 40.—Polar bodies of egg shown in Figs. 24—386, taken at 11.36.
3 and 7; tube drawn 60 mm.

Fic. 41.—Same, first polar body at 11.17.

Fic. 42.—Polar bodies and sperm at beginning of first segmentation.
3 and 7.

Fic. 43.—Same at close of first segmentation.

Fie. 44.—Polar bodies during 64-cell stage. 3 and 7; tube drawn 60 mm.

Fig. 45.—Same in 128-cell stage.

Fies. 46—50.—First segmentation, showing filose activities of polar bodies
and blastomeres. All figures from the same egg at the following intervals :—
12.06 m., 12.065, 12.09, 12.11, 12.16. land 7; tube drawn 60 mm.

Fic. 51.—Egg in which blastomeres were almost entirely separated, and
in which they showed perceptible motion during flattening. Same magnifica-
tion.

Fic. 52.—Same egg as in Figs. 46—50, in the 4-cell stage (12.30). Central
opening crossed by spin-threads.

Fic. 538.—Four-cell stage, top view. Enlarged from a camera lucida sketch
of living egg.

HABITS, ETC., OF CEREBRATULUS LAOTEUS. 197

Fic. 54.—Eight-cell stage, showing dextral twisting of the upper cells.
Enlarged from camera lucida sketch of living egg.

Fic. 55.—Blastula with differentiated ectoderm and entoderm, and mesen-
chyme cell separating from the latter. 3 and 7, from a preserved and mounted
specimen.

Fie. 56.—Section showing nuclear spindle parallel with surface subsequent
to giving off of first polar body. 3 and 3.

Fic. 57.—Same with spindle diagonal after extrusion of second polar body.

Fic. 58.—Same with segmentation spindle for first segmentation.

Fic. 59.—Sperms, enlarged from camera lucida sketch, ef. Fig. 42.

PLATE 11.

Fie. 60.—Longitudinal horizontal section of a regenerating papilla, showing
formation of sexual pouches and intestinal ceca; anus terminal. 3 and Tolles
l-inch objective.

Fies. 61 and 62.—Longitudinal horizontal sections of male and female ;

immature genital pouches scattered through the connective tissue. Killed in
April. 1 and 8.

Fic. 63.—Transverse section of female killed in April, showing relation of
developing egg-pouches to inner longitudinal muscle layer. 3 and 3.

Fie. 64.—Portion of immature ovary from Fig. 62, enlarged to show
method of egg development. 1 and 7.

Fig. 65.—A single egg pouch of Fig. 62, enlarged to show egg cells, yolk
cells, and glycerine cells. The walls are formed from connective tissue.
1 and 7.

Fre. 66.—A single sperm pouch of Fig. 61, enlarged to show formation of
sperm mother-cells. The connective tissue here extends into the pouch, and
the sperm cells are supported upon it. 3 and 3; tube drawn 60 mm.

Fic. 67.—A small portion of Fig. 66, enlarged to show the way in which
the sperm cells are borne on the mesoderm strands. 3and 7; tube drawn
60 mm.

Fic. 68.—A single sperm pouch magnified still farther to show transfor-
mation from sperm mother-cells into sperms. 3 and one twelfth oil immer-
sion.

Fies. 69—73.—Vertical sections of a late blastula and four gastrulas in
different stages of development, showing the origin and development of the
apical plate, the formation of mesenchyme cells, and clearing of ectoderm. 1
and 7; tube drawn 60 mm.

VoL. 43, PAR! 1.—NEW SERIES. )

198 CHAS. B. WILSON.

Fic. 74.—Longitudinal vertical section of pilidium; apical plate fully
developed with apical muscle attached ; aboral ectoderm much flattened and
perfectly transparent ; oral ectoderm thicker, more opaque, and beginning to
invaginate anteriorly ; micromesencytes scattered over the inner surface of
both ectoderm and entoderm. 1 and 7.

Fic. 75.—Transverse section of lappet; three rows of cells bearing long
cilia ; locomotor muscles. 3 and one twelfth oil immersion.

Fic. 76.—Longitudinal section of apical plate, showing arrangement of
flagella in bunches and the connection of the muscle-fibres. 3 and one
twelfth oil immersion.

Fie. 77.—Longitudinal vertical section through the lappet, the esophagus
wall, and the stomach. The locomotor muscle band (/om.) is here seen to be
continuous with the circumoral muscle (com.). 3 and one twelfth oil
immersion.

Fic. 78.—Longitudinal vertical section of the lappet through the wall cells
of the cilia rows, with a portion of the locomotor muscle band and the mesen-
chyme cells forming the radial muscles of the lappets. 3 and one twelfth oil
immersion.

Fic. 79.—Longitudinal vertical section as in Fig.77, showing the locomotor
muscle band composed of cells and fibres. 3 and one twelfth oil immersion.

Fic. 80.— Longitudinal vertical section of stomach, showing ordinary ento-
derm and gland cells. 3 and one twelfth oil immersion.

Fic. 81.—Same as Fig. 77, but showing more plainly the row of mesen-
chyme cells which form the radial lappet muscles.

Fic. 82.—Longitudinal horizontal section just above the mouth, showing
the two anterior invaginations with mesoderm attached ; the walls of the ceso-
phagus with a central groove posteriorly for the food particies. 3 and 8;
tube drawn 60 mm.

With Ten Plates, Royal Ato, 5s.
CONTRIBUTIONS TO THE KNOWLEDGE OF RHABDOPLEURA
AND AMPHIOXUS.
By E. RAY LANKESTER, M.A., LL.D., F.R.S.
London: J. & A. CHURCHILL, 7, Great Marlborough Street.

Quarterly Journal of Microscopical

Science.

The SUBSCRIPTION is £2 for the Volume of Four Numbers;
for this sum (prepaid) the JouRNAL is sent Post Free to any part
of the world.

BACK NUMBERS of the Journat, which remain in print, are
now sold at an uniform price of 10/-.

The issue of SuppLement Numpers being found inconvenient,
and there being often in the Hditor’s hands an accumulation of
valuable material, it has been decided to publish this Journal at
such intervals as may seem desirable, rather than delay the appear-
ance of Memoirs for a regular quarterly publication.

The title remains unaltered, though more than Four Numbers
may be published in the course of a year.

Hach Number is sold at 10/-, and Four Numbers make up a
Volume.

London: J. & A. CHURCHILL, 7 Great Marlborough Street.

TO CORRESPONDENTS.

Authors of original papers published in the Quarterly Journal
of Microscopical Science receive twenty-five copies of their
communication gratis.

All expenses of publication and illustration are paid by the
publishers.

As a rule lithographic plates, and not woodcuts, are used in
illustration.

Drawings for woodcuts should nor be inserted in the MS.,
but sent in a separate envelope to the Hditor.

Contributors to this Journal requiring extra copies of their
communications at their own expense can have them by applying
to the Printers,

Messrs. ApLARD & Son, 224, Bartholomew Close, H.C., on
the following terms :

For every four pages or less—

25 copies 3 : : : 5/-
Uke . : . ; 6/-
100 7/-

a : ; : :
Plates, 2/- per 25 if uncoloured; if coloured, at the same rate for
every colour.

Prepayment by P.O. Order is requested.

ALL CoMMUNICATIONS FOR THE EDITORS TO BE ADDRESSED TO THE CARE
or Messrs. J. & A. Cuurcuity, 7, Great Mariporoucu Srreer,

Lonpon, W.

THE MARINE BIOLOGICAL ASSOCIATION

OF THE
UNITED KINGDOM.

Patron—H.R.H. the.PRINCE OF WALES, K.G., F.R:S.
President—Prof. E. RAY LANKESTER, LE. Ba ES:

30;

THE ASSOCIATION WAS FOUNDED “ TO ESTABLISH AND MAINTAIN LABORATORIES ON
THE COAST OF THE UNITED KINGDOM, WHERE ACCURATE RESEARCHES MAY BE CARRIED
ON, LEADING TO THE IMPROVEMENT OF ZOOLOGICAL AND BOTANICAL SCIENCE, AND TO
AN INCREASE OF OUR KNOWLEDGE AS REGARDS THE FOOD, LIFE CONDITIONS, AND HABITS
OF BRITISH FOOD-FISHES AND MOLLUSCS.”

The Laboratory at Plymouth

was opened in 1888. Since that time investigations, practical and scientific, have
been constantly pursued by naturalists appointed by the Association, as well as by
those from England and abroad who have carried on independent researches.

Naturalists desiring to work at the Laboratory

should communicate with the Director, who will supply all information as to
terms, &e.

Works published by the Association

include the following :—‘ A Treatise on the Common Sole,’ J. T. Cunningham, M.A,,
4to, 25/-. ‘The Natural History of the Marketable Marine Fishes of the British
Islands, J. IT. Cunningham, M.A., 7/6 net (published for the Association by
Messrs. Macmillan & Co.).

The Journal of the Marine Biological Association

is issued half-yearly, and is now in its fifth volume (price 3/6 each number).

In addition to these publications, the results of work done in the Laboratory
are recorded in the ‘Quarterly Journal of Microscopical Science,’ and in other
scientific journals, British and foreign.

Specimens of Marine Animals and Plants,

both living and preserved, according to the best methods, are supplied to the
principal British Laboratories and Museums. Detailed price lists will be forwarded
on application.

TERMS OF MEMBERSHIP.

AwnnuaL MEMBERS . : é . £1 1 Operannum.

Lire Members . 4 : : . 15 15 O Composition Fee.
FOUNDERS . : : , : posived 070 Jeph Oe 6) ee 5
Governors (Life Members of Council) 500 O O Pa 53

Members have the following rights and privileges:—They elect annually the
Officers and Council; they receive the Journal free by post; they are admitted to
view the Laboratory at any time, and may introduce friends with them; they have the
first claim to rent a table in the Laboratory for research, with use of tanks, boats, &e. ;
and have access to the Library at Plymouth. Special privileges ure granted to Governors,
Founders, and Life Members.

Persons desirous of becoming members, or of obtaining any information with
regard to the Association, should communicate with—

The DIRECTOR,
The Laboratory,
Plymouth.

JUN 4 1900
fs a.

|
_New Series, No. 170 (Vol. 43, Part 2). Price 10s.

APRIL, 1900.

THE

QUARTERLY JOURNAL

OF

MICROSCOPICAL SCIENCE.

EDITED BY

EH. RAY LANKESTER, M.A., LL.D., F.R:S.,

HONORARY FELLOW OF EXErER COLLEGE, OXFORD; CORRESPONDENT OF THE INSTITUTE OF FRANCE,
AND OF THE IMPERIAL ACADEMY OF SCIENCES OF ST. PETERSBURG, AND OF THE ACADEMY
OF SCIENCES OF PHILADELPHIA} FOREIGN MEMBER OF THE ROYAL BOHEMIAN
SOCIETY OF SCIENCES, AND OF TH® ACADEMY OF THE IINCEL OF ROME;
ASSOCIATE OF THE ROYAL ACADEMY OF BELGIUM; HONORARY MEMBER
OF THE NEW YORK ACADEMY OF SCIENCES, AND OF THE
CAMBRIDGE PHILOSOPHICAL SOCIETY, AND OF THE ROYAL
PHYSICAL SOCIETY OF EDINBURGH; HONORARY
MEMBER OF THE BIOLOGICAL SOCIETY
OF PARIS;

DIRECTOR OF THE NATURAL HISTORY DEPARTMENTS OF THE BRITISH MUSEUM, FULLERIAN PROFESSOR

OF PHYSIOLOGY IN THE ROYAL INSTITUTION OF GREAT BRITAIN.

WITH THE CO-OPERATION OF

| ADAM SEDGWICK, M.A., F.BS.,

FELLOW AND TUTOR OF TRINITY COLLEGE, CAMBRIDGE 5

| W. F. R. WELDON, M.A., F.R:S.,

LINACRE PROFESSOR OF COMPARATIVE ANATOMY AND FELLOW OF MERTON COLLEGE, OXFORD; i
LATE FELLOW OF ST. JOHN’S COLLEGE, CAMBRIDGE ;

AND |

SYDNEY J. HICKSON, M.A., F-R:S.,

BEYER PROFESSOR OF ZOOLOGY IN THE OWENS COLLEGE, MANCHESTER,

WITH LITHOGRAPHIC PLATES AND ENGRAVINGS ON WOOD.

ft
~ LONDON:
J. & A. CHURCHILL, 7, GREAT MARLBOROUGH STREET.

1900.

Adlard and Son,] [Bartholomew Close.

CONTENTS OF No. 170.—New Series.

MEMOIRS:

On the Reaction of Daphnia magna (Straus) to certain Changes in
its Environment. By Ernest Warxen, D.Sc., University College,
London

A Revision of the Genus Steganoporelia. By Stpnny F. Harmer,
Se.D., F.R.S., Fellow of King’s College, Cambridge; Superintendent
of the University Museum of Zoology. (With Plates 12 and 13) .

On a New Histriobdellid. By Witutam A. Hasweut, M.A., D.Sc.,
F.R.S., Challis Professor of Biology, ie of ae (With
Plates 14 and 15) 5 :

On Spongioporphyrin: the Pigment of Suberites Wilsoni. By
C. A. MacMunn, M.A., M.D. (With Piate 16)

Further Remarks on the Development of Amphioxus. By E. W.
MacBripz, M.A., D.Se.(Lond.), Professor of Zoology in MeGill
University, Montreal. (With Plate 17)

Quelques Observations sur les Onychophores (Peripatus) de la Collee-
tion du Musée Britannique. Par M. EB. L. Bouvier, Professeur au
Muséum d’histoire naturelle de Paris

On the Diplochorda. LI. The Karly Development and Anatomy of
Phoronis Buskii, Mcl. By Arruur T. MastErMaN, M.A.
(Cantab.), D.Sc.(Lond. and St. A.), Lecturer on Zoology in the
New Medical School, Edinburgh. (With Plates 18—21)

PAGE

199

225

299

337

351

367

375

JUN 4 1900

CHANGES IN ENVIRONMENT OF DAPHNIA MAGNA. 199

On the Reaction of Daphnia magna (Straus)
to certain Changes in its Environment.

By

Ernest Warren, D.S8c.,
University College, London.

For some years I have been engaged in breeding Daphnia
magna (Straus), for the purpose of obtaining data which
would be of value in testing the current theories of heredity.
The investigation has led me to a series of experiments on
the action of common salt, and on the effect of a confined
volume of water on this animal. Some of the results seem
to present certain features of considerable interest and of
wide biological significance ; they illustrate how closely the
organism is knit to its external conditions of life.

It will be best to give here a brief epitome of some of the
results.

In the first place it will be shown that the times of killing
with varying strength of solutions of sodium chloride are
between certain wide limits (‘9 per cent. to 6:0 per cent.),
well represented by a rectangular hyperbola. The modifica-
tion induced by varying temperature is then discussed.

The physiological condition of the animal at the time of
immersion into the salt solution is shown to have an enor-
mous effect on the resisting power. From the results ob-
tained an antagonism between excessive vegetation and
animal life was surmised. In a foot-note to the description
of the experiment it is suggested that the observed injurious
effect was due to the green light and the shading caused by

VOL. 43, PARTY 2.—NEW SERIES. P

200 ERNEST WARREN.

the plants. Since this was written some experiments have
been made which point to the conjecture being correct. At
the present time I am engaged with the subject, but the
following results seem to be appropriate here.

Newly hatched Daphnia were placed in five glass capsules,
each of which was put in a shallow box.

The first box was covered by a sheet of ground glass.!

Second box by a flat glass dish containing a solution of
fuchsin in spirit. (Spectroscopically a pure red.)

Third box by a sheet of Chance’s pot-green glass (trans-
mitting a trace of blue green).

Fourth box by (1) a sheet of cobalt-blue glass, on the
top of which was placed (2) a flat glass dish containing a
diluted solution of ammoniated copper sulphate (perhaps
transmitting a trace of red).

Fifth box was made light-tight.

Two broods of Daphnia were taken, and an individual from
each brood was placed into each glass capsule. Thus there
were two individuals derived from two broods in each cap-
sule.

A second series of chambers was prepared, and three in-
dividuals from three broods were placed in each pot. The
animals were constantly supplied with fresh water and mud.
After a certain period the animals were measured by an ocular
micrometer; the dimension taken was the total length of the
body excluding the spine (see fig. 3, A, B).

The results of the experiment are given in the following
table:

1 With two pieces of ground glass the intensity of the white light is very
much reduced. The effect on the Daphnia, however, was practically the
same, hence the results observed are not simply due to the varying intensity,
but to the wave-length of the light.

CHANGES IN ENVIRONMENT OF DAPHNIA MAGNA. AON

Ist Series, 12°—19° C. 2nd Series, 19° C.

| Web. 25th, 2 |

Source of |. : :
| individuals of March 25th, 3 indi-

Qnd series.

ight. 5 Y ill, : ;
Sen /Same size (just) Mean ae viduals of same size | Mean
hatched). Mea- size. Spite (just hatched). Mea- | size.
sured on pring.) Sured on April 10th. <j
| March 25th. 2
| Ground }mm., mm, mm. mm. mm. mim. mim.

glass {3°04 2°77 | 2-90 10 | 2°56 2-78 1 died | 2°67| 10 | 2°79 | 5
Red |327 38:17) 3:22) 24 | 290 2:53 2-70 |2:71| 16 | 297 | 8
Green | 2°53 2. 2°55 | o | 2°38 2°66 2:08 | 233 2 | 2-44 ‘O4

2 2:35 222 Oe idiedp2;30) eee) eeioon |i eOnl|

_ 5
Blue | 2:33 2:3 |
In the | | |
dark | 2°56 2°63 | 2°59 0 .| 212 219 1 died | 2°16 O). || PBI |)

On April 17th the individuals of second series under the
ground glass had attained a size of 2°94 mm. and 3°14 mm.
and had produced forty-seven offspring. ‘Those under green
hight were 2°65, 2°11, 2.43 mm., and there were five young.
Under blue light 2°48, 2°43 mm., and six young. In the dark
2°36, 2°45 mm., and there were two young.

The individuals which had been living in green and blue
light and in the dark succumbed much quicker to °5 per cent.
NaCl than those which had been living in red light or under
ground glass. I hope, however, to deal with the subject at
greater length on a future occasion.

Daphnia have a very low power of becoming acclimatised
to salt.

Daphnia living in a small confined volume of water are
shown to gradually lose their spines (see fig. 3). The experi-
ments described prove that if an aniinal be allowed to grow
up in 40 ¢.c. of freshly drawn water, its spine would on the
average be shorter by several hundredths of its body length
than if it had lived in an unlimited bulk.

The sudden transference from water containing more
mineral constituents to water containing less, and vice
versa, is apparently not without effect.

Living in a small confined volume of water is shown to
have a great influence on the rate of growth and reproduc-

202 ERNEST WARREN.

tion ; also it would seem as if the water becomes so changed
in character as to be specifically injurious to Daphnia.

YZ J, Tur Reaction or DAPHNIA MAGNA TO DIFFERENT
SrRENGTHS OF SOLUTIONS OF Sopium CHLORIDE.

Py

The Daphnia experimented with were taken from a large
tank (3 x 44 x 14 ft.), facing a south-east window at University
College, London. The tank contained a luxuriant growth of
Vallisneria, and a constant slow current of water was main-
tained. Some two years previously the tank had been
stocked from various sources. During the winter the water
was kept at a temperature of about 17° C. by a small gas-
ring fitted below the tank.

It was found that a Daphnia placed into a solution contain-
ing above 1 percent. NaCl soon becomes uneasy and agitated,
and that after a certain time it may turn several somer-
saults in the water (sudden exposure to a strong light some-
times causes the same phenomenon), and then it sinks to the
bottom of the vessel. After this the animal may make
several feeble attempts at swimming, but it is soon exhausted.
The heart continues to beat, and the antenne and lmbs to
move for a considerable time, and in the weaker solutions
(0°7 per cent., 0°9 per cent., 1:0 per cent.) this may go on for
hours. If after the last trace of movement has ceased the
Daphnia be placed in fresh water the animal may recover,
and after about ten minutes feeble movements of the heart
and limbs may be observed. The Daphnia may recover com-
pletely and breed, or it may swim about for a few hours and
then die. ‘The condition when movement has ceased may be
termed salt-rigor.

1. The Rate of Killing asa Function of the Strength
of the Solution, the Temperature remaining Con-
stant.

The first point to investigate was the time at which salt
rigor occurred, using different strengths of solutions but a

CHANGES IN ENVIRONMENT OF DAPHNIA MAGNA. 208

constant temperature. A solution containing a definite per-
centage of salt was taken and five Daphnia were simultane-
ously placed in it, and the time elapsing before the last
flickering movements of the limbs stopped was noted. Some
of the animals were found to succumb much quicker than
others. This experiment was performed five times with the
same strength of solution. Thus the longest period recorded
out of the five trials was the time in which all the animals out
of the twenty-five had either died or passed into the condi-
tion of salt-rigor. The twenty-five Daphnia were treated in
detachments in this way, because it was found impossible to
examine with sufficient exactness and speed more than five
individuals.
The results are summed up in the following table:

Taste I.—Daphnia magna from the tank at Univer-
sity College, London, October, 1897. Tempera-
ture during experiments = 21° C.

| / : : The time for
/Percentage | Every number expresses the time (mostly in minutes) |‘ killing ” 100
| of NaCl. taken to ‘* kill” a batch of 5 Daphnia. % of the 25
individuals.
5 2 days, 30 hrs., 15 days ! @
| “ff, Zi hrs lt ehrst.) 16 hrs: LOvhrs:, 14) has: 1260
“) 192, 158, 220, 291, 218 291
1:0 129, 128, 71, 102, 129 129
1-2 61, 58, 59, 75, 63 75
14 44, 38, 41, 43, 40 44,
16 28, 32, 25, 31, 33 33
18 27, 21, 25, 30, 24 30
2°0 20, 22, 22, 21, 20 22
2°6 14, 14, 15, 14, 13 15
30 WP, WO), 10, 5 ill 12
4-0 8583, fy Sa 8
6:0 6, 5, 5°5, 4°5, 6 6
10-0 4, 4, 3°5, 4, 4 4,
20:0 4, 3°5, 3, 4, 3 4

1 In this batch it took fifteen days to kill one of the Daphnia, and it seems
to me doubtful how far the salt was the cause of its death,

Palsy ScuGmeromncc. wcecn slice Oc. Ole Si 2) ‘Ol <i "te eh. ck HM OF 6 8 4 9D Y b £ ct T 0
SIDYINIJUId OF 8S 9S US CS OS 8b 9b bh CY Ob BE FF bE CE OF 82 H@ bt C2 OF SI GI bi 24 OF

seen Oantanw eee lig |

Ok)

+09

06
Z
=

= ————1— 02/
<
=

= OS!
M
&
eB

= aE | Orsell

‘SUL[[D] JO VUIT] perAdssqo vy} JUVSadda.a SopaIo OJ,
Ue-(8-HK vpoqiodAy iwpNSuvjood Vy} St sammd oy], Olz
‘T OINGL]

OvZ

OLE
=
S

N ar

———— S@eznerITy

CHANGES IN ENVIRONMENT OF DAPHNIA MAGNA. 205

This curve is represented in the accompanying diagram
(Fig. 1). Between the limits of 0°9 per cent. and 6:0 per
cent. solutions the curve is well represented by a rectangular
hyperbola, and we have the relation T(a—8) = constant,
where I’ = the time of killing, and w = the strength of salt
solution between the limits of the 9th and 60th units.

The relation may be shown in a tabular form thus:

Tasie IT.

| |
Solution of | iT ee | Product T («—8) 276-7
NaCl. i should be constant 7—8
| Re Ne ts =
Percentage.
‘ | PAE 1 291 277
1:0 129 2 238 138
1G 75) 4. 200 69
Lea] 4A, 6 264 46
16 33 8 264 | 35
1:8 30 10 300 | 28
Za0) 22 12 264 | 23
26 iby | 18 270 | 15
30 12 22 264: 13
AO ie tS 2 256 9
6:0 | 6 | 52 312 5
| |

Mean of the products T (@ — 8) = 276°6.

Thus in no case do the products T(#—8) diverge very
widely from the mean 277. ‘lo show how rigorous is this
test it may be remarked that one minute error in the
observation, say at 3 per cent. solution, would make a
difference of 22 in the product.

According to these experiments solutions below ‘9 per cent.
and above 6:0 per cent. appear to introduce different sets of
causes from those between these limits.

Perhaps there is something more than mere analogy with
Boyle’s Law, which states that, with certain restrictions
and between certain limits, PV is constant for any gas where
P = pressure and V = volume, the temperature being fixed.
Volume may be compared with the amount of salt in the
solution above a certain ‘zero’ percentage (‘8 per cent.),

206 ERNEST WARREN,

and pressure with the rate at which the solution acts on
Daphnia, i.e. the rate at which the molecules of salt strike
the animal.

2. The Rate of Killing as a Function of Tempera-
ture, the Strength of the Salt Solution being
kept Constant.

Some observations were made on the effect of temperature
on the rate of killing. 1°6 per cent. and 2 per cent. solutions

were employed. ‘he results are given in the following
table :

Papi wk
16 % NaCl. 2°/, NaCl.
Timein minutes to | Time of Time in minutesto | Time of
Temperature. * kill’ sets of | killing | Temperature. | “kill” sets of killing
| | 5 individuals. | 100 %. 5 individuals, | 100 %.
2° C. = = 22 85, 63 85
3° C. 79, 105, 99,95 | 105 | 83°C. =: is
7 C. 75, 65 eye leer = =
14° C. 48, 45 | 48 Wa | Sul, 29), Bill al
PALL WS Be Fay, Bil, BE} |) Se Pale (i, |] VXO, Be Dee Ol 22
aCe 22, 23 23 Use (OF 19, 18 19
AES (OL 16Ey 5 1 06 29:52. | 16, 13 16
SC, UGS MAAS Iss a) 16 38) (Ch _— —
OL | — —_ BH? (CE Ue MO, inl, ie) )) ala

It is obvious from the accompanying diagram (Fig. 2)
that the observations may fairly be represented by the inter-
polated curves. The points found on the curves’are some-
what too few, but, as we shall see later on, the blanks could
not now be filled up; for unless the fresh Daphnia employed
were exactly in the same physiological condition as those
used for the rest of the curve they would not be comparable.
Since the points that were found are sufficient to show the
general effect of temperature it was not thought to be neces-
sary to do the experiments afresh.

The point at which heat-rigor occurred was 38:25° C.
[= 101° F.]. This was determined by slowly (i.e. taking

207

NT OF DAPHNIA MAGNA.

.
4

CHANGES IN ENVIRONMKI

qpeifyue] gag Ov 06 86 LE 96 SE He Eo 2b Ib Ob G2 98 lz G2 Sit b2 2% ie 02 6 8 LI 9 SI H EI 2 EL ALE OSLER ID AG ARS HO)

ere =Sle— i ee ere Cee a et eae

4

-<-- -+—
~<..
-<--.

“552. |
nose ee 25>
AS Se TES et
“oy. "5}.
- ~ Waa
co Kah 10S
SANs OQ Sa
<*, oe S
a te
—h, ONS
aes as
‘=. Len 1
x S)
eee %
i) ee ‘
‘ ‘
o*, »)
aN x.
‘
‘uoneodia3zur ies ‘
Aq UMBIP 391 SOAIND ay) : SUITTIY Jo aul %
P2eATISQgoO VY} JUVSaIdaI SapP1TD DY, ~ s

axccite ie

S27 MALI

208 ERNEST WARREN.

about ten minutes) heating the water in which the Daphnia
were placed.

The ends of the temperature curves in the neighbourhood
of 33° C. and 35° C. give no indication of being influenced
in any way by the approaching point of heat-rigor. Clearly
the curves would end practically abruptly against the verti-
cal through this point. The temperature at which heat-
rigor occurs introduces a new order of things, which is
probably distinct from the influence of temperature in
accelerating the time of salt-rigor.

8. The Effect of the Physiological Condition of
the Animal on the Rate of Killing.

Tt was noticed by repeated trials that out of a number of
Daphnia taken from the tank and placed into 2 per cent.
NaCl some 75 per cent. died in 4 days. The individuals
which survived were removed and placed separately in tum-
blers of fresh water, and broods were obtained. When the
offspring had grown up they were put into *2 per cent. NaCl,
and if was found that all the individuals survived 4 days’
immersion. These individuals had been bred in a fairly
constant temperature of 20° C. The question now to answer
was, whether this strong resisting power was inherited from
the parents, or whether it was due to the change in the
conditions of life. That is the change from living in the large
tank to living in clean tumblers, and so under different con-
ditions with regard to food, light, temperature, etc. The
following observations show that the latter alternative is quite
sufficient to account for the result.

The tank in which the Daphnia were living had become
choked with the luxuriant growth of Vallisneria, and it was
noticed that the Daphnia were dwindling in numbers. On
the morning of November 23rd most of the Vallisneria was
removed. Ina few daysthe Daphnia were visibly increasing
in numbers, and in about three weeks there was quite a swarm.
Some of these Daphnia were now put into ‘2 per cent. NaCl

CHANGES IN ENVIRONMENT OF DAPHNIA MAGNA. 209

and none died, while 75 per cent. of the Daphnia taken out
of the tank a few days previously died in four days.

Previous to the removal of the plants all the Daphnia
(except in one case where an individual survived and bred)
immersed into ‘5 per cent. NaCl] died in thirty-six to forty
hours; but two days after the removal most of them lived
for ninety-six hours, while some survived and produced
young. During the following three weeks sets of ten indi-
viduals were repeatedly put into ‘5 per cent. NaCl, and the
time when 100 per cent. had succumbed was noted. The
results are given in the accompanying table.

Taste LV.

Daphnia living in a tempera- Put into a temperature of
ture of 17° C. 20°C.
Date at which 10 Daphnia from Time in hours when 100 per
the tank were put into “5 cent. of the Daphnia had
per cent. succumbed.
Nov. 19th $06 ae 36
>» and ste See 40
sy SSN oie he oe)
oo) 2th Bod Sa 96
Dec. 6th ss as 72
ay ohge re pad 40
Bye ksh nae 366 40
yan if ie 40
», Leth ee aie 22
», 14th on a 22

Removal of Vallisneria 11 o’clock a.m., November 23rd.

The vigorous condition of the Daphnia on November 25th,
29th, and December 6th was followed by a rapid decadence
in the power of resisting the action of the salt. These large
and remarkable fluctuations in the resisting power seem to
point to the following conclusions. The removal of the
excessive vegetation was highiy favourable! to the Daphnia;
reproductive activity came into full swing, and the general

1 The exact cause I am endeavouring to ascertain at the present time. I

am inclined to think that the shading effect and the green light are both pre-
judicial to the growth and reproductive power of Daphiia,

210 ERNEST WARREN.

health of the animals reached a maximum. The resisting
power to the salt at this period was very great. Gradually
as the tank became crowded, the poisoning effect (further
evidence of this will be adduced later) of the close proximity
of large numbers of animals of the same kind came into
force. The Daphnia became sickly, and the resisting power
to the salt sank very low. This view is supported by the
further behaviour of the animals in the tank; the crowd
of Daphnia died off, and after about a month only a com-
parative few remained.

4, Experiments on the acclimatisation of Daphnia
magna to sodium chloride.

a. History of the Y Family.

October 19th.—F ive individuals from the tank were placed
into *2 per cent.

27th.—There was one survivor (= Y), and this had pro-
duced a brood (= Ya). Y and Y a were now placed into
‘5 per cent. solution.

November 3rd.—Ova appeared in the brood pouch of Y,
and they became red by the action of the salt. This proves
that the salt has a distinct chemical action, and that the
phenomena observed are not to be referred to merely the
density of the medium.

15th.—Y, Y a, Y a, were put into °55 per cent. solution.

18th.—Y dead.

24th.—All the animals dead.

B. History of the X Family.

October 19th.—Five Daphnia from the tank were placed
into ‘5 per cent. solution.

21st.—All five animals were dead, but a newly born indi-
vidual was alive and well. This was placed into a fresh
tumbler of *5 per cent., and labelled X.

November lst.—X produced a brood Xa; two individuals
of this brood were placed into fresh water to act as a control,

CHANGES IN ENVIRONMENT OF DAPHNIA MAGNA. 211

The X family was living in 200 c.c. of solution, and 1 c.c. of
1 per cent. solution was now added on alternate mornings.

Ath.—Kges in brood pouch of X reddish.

8th.—X and X a were put into °525 per cent. solution.

1lth.--The eggs in brood pouch of X had become of the
ordinary dark colour.

15th.—X, X a, X a, were put into °55 per cent. solution,
and no addition of salt was now made.

18th.—X apparently well; the broods X a and X a, were
very slow in growing; the largest were not more than half
the size of the two control individuals which had been placed
into fresh water on November Ist. One of these two control
animals had produced two young on November 16th.

23rd.—All dead; the controls were perfectly healthy.
Thus in both the X and Y families it was not found possible
to acclimatise the animals to a solution above ‘55 per cent.
NaCl. The gradual increase in salinity from ‘5 per cent. to
‘do per cent. during a fortnight proved to be too rapid to
affect a thorough acclimatisation to °55 per cent. It is very
doubtful whether acclimatisation per se could be carried
much beyond this.

5. Does acclimatisation to a certain strength of
solution increase the resisting power to a solution
containing a higher percentage of salt?

Suppose an animal has been acclimatised to a certain solu-
tion of salt, say a per cent., and is then plunged into an #
per cent. solution, where # is greater than a, the question
arises whether the w per cent. solution would act on the
acclimatised animal like an w«—a per cent. solution on an
ordinary Daphnia from the tank.

Thirty Daphnia! were taken from the tank and gradually
acclimatised (taking seventeen days in the process) to *25 per
cent. solution. None of the Daphnia died in the process.

1'This was at the period when ‘2 per cent. solution killed 75 per cent. of
the animals in four days.

pA ys ERNEST WARREN.

Thirty other Daphnia from the tank were made to live
under exactly similar conditions as the animals being accli-
matised, except that no salt was added to the water. These
individuals were for the purpose of acting as a control.

(1) Ten apparently healthy acclimatised Daphnia and ten
control animals were plunged into separate tumblers of 1 per
cent. solution. The acclimatised individuals “died” in eighty-
eight minutes, and the ten control Daphnia in ninety-eight
minutes. Nowif the 1 per cent. solution had acted on the
acclimatised animals like (1—°*25) per cent. = °75 per cent.
solution on ordinary Daphnia, they ought to have lived for |
hours, but we see that they resisted the salt less well than
the Daphnia which had been living in fresh water.

(2) Ten acclimatised and ten control Daphnia were plunged
into 1:2 per cent.; the former succumbed in thirty-five
minutes, and the latter in fifty-eight minutes. Thus, a
result similar to that of the first experiment was obtained.

It should be added that the Daphnia acclimatised to *25 per
cent. solution were perfectly healthy in appearance, and in
fact more so than the control individuals living in fresh water,
for some of the latter had died, and for some unknown reason
they did not seem in a very healthy condition.

Il. THe Reaction or DAPHNIA MAGNA TO A CONFINED VOLUME
or WATER.

The second series of experiments deals with the effect of a
small body of water on a certain dimension, and on the
power of growth and reproduction ; incidentally some remarks
will be made on the effect of a sudden transfer from one kind
of water to another.

1. The influence of a confined volume of water
on the length of the spine.

The “spine”? is formed by the posterior prolongation of
the carapace. Fig. 3 a represents an ordinary Daphnia
with a moderately long spine.

Professor Weldon pointed out to me that in all compara-

CHANGES IN ENVIRONMENT OF DAPHNIA MAGNA. 213

tively small volumes of water with no circulation, the spine
appeared to gradually diminish in length. Continued obser-
vation then proved that at the end of six months or so a

A. A Daphnia with a fairly long spine.
B. An individual in which the spine is absent.

colony of Daphnia in a large bell glass would possess exceed-
ingly small or no spines.

Some experiments were now undertaken to determine
the rate at which the spine diminishes, and the volume of
water which produces this reaction. Daphnia were placed in
a known volume of water, and the length of the spine in
successive generations was measured.

214 ERNEST WARREN.

Measurements.—(1) The length of the spine was
measured along a line which passed from its apex to a point
on the ventral surface of its base (B c). Since Daphnia con-
tinue to grow throughout life, it was necessary to express
the length of the spine in terms of some other dimension. For
this purpose the total length of the body was chosen.

(2) The body-length was measured along a line which
passed through the above point on the ventral surface of the
base of the spine, and cut the convex surface of the head
opposite the middle of the compound eye (a B). The measure-
ments were made under the microscope by means of Zeiss’s
screw micrometer.

Twelve adult Daphnia were taken without selection from
the tank.

Four of these (‘‘ A”’) were placed separately in four glass
tumblers containing 200 c.c. of water (that of the New River
Company) and alittle lump of Conferva. At the bottom of the
tumblers there was a layer of mud taken from the Victoria
regia tank at Regent’s Park. This mud contained many
Alge, &c., and constituted an adequate food-supply for the
Daphnia. The tumblers were covered with pieces of glass.

Four others (‘‘a”) were placed in tumblers which were in
every way similar to those of “Series A” except that the
coverings of glass were not used, and rain water collected in
the country was added from time to time to supply the loss
due to evaporation.

The remaining four Daphnia (“ b ”’) were placed in tumblers
containing similar mud, but the water was changed at least
six times a week.

A brood was obtained from each parthenogenetic female.
The mother was then measured, and the offspring were
allowed to grow up. When adult and about to produce
broods, all the children were measured except one. ‘The one
which was left was any individual of the brood, for no selec-
tion was made. After this animal had produced a brood it
was measured, and the offspring were left in the tumbler.

The results of the measurements on the spine are given in

CHANGES IN ENVIRONMENT OF DAPHNIA MAGNA. 215

the following table, and they are diagrammatically repre-
sented in the accompanying figure (Fig. 4).

Fig. 4.

TABLE V.
= S
= i=)
=x —)
ao ee
= x
a o =
2 = E\.8
Generation. te = |= 5
We ese cAI) eats
| o etl) Str
> — al
s a0 sS
S = j~)
mM | @ 1m
| =

| Malli-
metres. | Ratios.

The 4 “A” parents . .| 3°235 | 241
The children of the above 2°621 | 171
parents (20)
The4 “a” parents . . 2°998) 276 ©
The children (14). . .| 2°785 | 249) N
The grandchildren (18) . 2°616 | 185 f ¢
| =
The 4 “5” parents . . 3°119 | 194 4
The children (15) . . .| 3°086 | 179) &
The grandchildren (15) . 3°225 | 204 -
The great-grandchildren 2°997 205) &
(23) | | =

CHILDREN.

GRANDCHILDREN.

Apparently in these figures there are some signs of the
inheritance of the length of the spine, but it is much obscured
by the overwhelming influence of the condition of the water

voL. 43, PART 2.—NEW SERIES. Q

216 ERNEST WARREN.

in which the animals were living. The slope of the line
aaa’ (Fig. 4) is not very different from that of aa’; and
since the series “a” and “a” were living under fairly
similar conditions, this fact would seem to point to the cha-
racter being inherited. ‘he line b b’b” b’” shows a slight
downward tendency in the first generation, but in the second
and third generations there is a small rise above the parental
mean, which happened to be somewhat low. The mean spinal
length in the three generations was 196 thousandths, and
the parental mean was 194 thousandths; thus in the water
that was continually being changed the spine showed no
tendency to diminish.

The relative length of the spine sinks as the animal grows ;
and since under favourable conditions Daphnia continue to
grow as long as they live, the mean never becomes quite
steady. Consequently the means given in Table V would
only be absolutely comparable if all the animals had been
measured at one particular size. However, between the
limits of size employed the change in the mean would be
small, and if a correction could have been applied, it would
only have made the effects of the condition of the water still
more apparent.

In the “a” series, where no fresh water was added,
twenty individuals grew to an average size of 2°62] mm. in
800 c.c. of water; this gave an average bulk of 40 c.c. of
water for each animal. The average diminution of spine was

241—171
SaOn0IS a 70 thousandths of body-length.

Under the somewhat different conditions in the ‘ a”’ series,
where rain water was added, twenty-seven individuals grew
up to a size of 2°704 mm. in an average bulk of 30 c.c. of
276 — 218

water, and the average lessening of the spine was 7000

= 58 thousandths.

Thus quite roughly it may be said that if a newly hatched
Daphnia be allowed to grow up to “adult” life in 40 c.c. of
freshly drawn water, its spine would on the average be

CHANGES 1N ENVIRONMENT OF DAPHNIA MAGNA. 217

shorter by several hundredths of its body-length than if it
had lived in an unlimited bulk.

2. The influence of a confined volume of water
on the rate of growth and reproduction.

(a) The History of the “A,” “a;7? and “b” Families:
The differences in the conditions of life in the three series
of tumblers used in the previous experiment produced a con-
siderable effect on the rate of reproduction; asmall supply
of water decreased in a marked manner the number of
generations and the number of offspring in a brood. The
following table gives the mean dates at which broods were
produced, and the total number of offspring in each series.

TaBLeE VI.
Series ‘‘ A’ | Series “‘a” Series “6”
(no fresh water added). (a little rain water added). (water constantly changed).

The four mothers put in
tumblers and produced |
broods of the— |
1st generation, Ist generation, Ist generation,

July 28rd (20!) |,-,.... July 23rd (14) July 28rd (15) The
2nd generation, eV 2nd generation, oe 2nd generation, TN
Aug. 7th (17). Aug. 8th (18). Aug.7th(25-10)
3rd generation, 3rd generation, 3rd generation,

Aug. 30th (12) 23days Aug. 29th (15) 21days Aug. 25th (23) 18days

| 4th generation,

vy er ‘ude ’ Senn) Sept. Sthi(22) ) WaAdays
Sth generation,

These individuals of the 3rd generation grew ex- | Sep.23rd(25-14) 15days
ceedingly slowly. About twelve young were pro- 6th generation,

duced towards the end of September and then Oct.9th(24-12) 16days
breeding stopped, and all the individuals were dead | 7th generation,

by the beginning of December. | Nov. 4th (16). 26days

Although the water was
| continually changed two
of the families died out,

Fresh Daphnia from the tank were put into these | and the others were in a
tumblers on December 10th. They very soon be- ‘sickly condition on Dee.
came unhealthy in appearance, and some died in | 15th,
abont a fortnight. Very few young were produced,

and all the animals were dead early in January. Fresh Daphnia taken
from the tank and put into

the same tumblers, with
the same mud, lived and
produced broods in a per-
fectly normal manner.

The te:nperature was kept at about 17° C.

1 These are the number of young produced by the four mothers,

218 ERNEST WARREN.

This table requires some comment.

The number of generations and the number of offspring in
the series in which the water was continually being changed
are seen to be far in excess of those in the other two series.
Thus the condition of the water arrived at by remaining in
the tumblers! was prejudicial to the growth and reproduction
of Daphnia.

The fifth generation of twenty-five young was produced by
the ‘b” series at about the same time as the fourth genera-
tion of 12 young by “A” and “a” series.

I am unable to account with certainty for the ultimate
weakening of the stock in the series, which had an ample
supply of fresh water. It is possible that the following
circumstance was the cause of it.

(8) The Effect of Sudden Transference from one
kind of Water into another.

On August 3rd all the Daphnia were carefully packed and
taken by train under personal supervision to Canterbury.
They were placed on a table by an east window facing a
garden. The water used for series “b” was the town water
supplied by the local waterworks.

On August 5th broods were produced amounting to twenty-
five young, of these ten became sickly and died when a few
days old; also the period (eighteen days) between the second
and third generations was somewhat in excess of the usual
fortnight. ‘lhe stock, however, completely recovered and
became perfectly healthy.

On bringing the animals back to London and replacing
them in New River water some fourteen of the young died,
and the stock became permanently weakened.

In October two of the families died out altogether, and the

1 Every week or ten days the water and mud were emptied out of the
tumblers, and the glass was thoroughly cleansed from the green incrustation of
alge, etc., which had collected on it. In the “A” and ‘‘a” series the same
water was then replaced.

CHANGES IN ENVIRONMENT OF DAPHNIA MAGNA. 219

remaining two were alive but apparently sickly at the middle
of December.

That this result was due to the unavoidable shaking in
railway travelling would seem to be unlikely. It is con-
ceivable that the sudden stimulus produced by transfer from
one water to another was prejudicial, and that the second
application of a like stimulus was still more damaging to the
race.

The following table shows that the two kinds of water
differ widely in the amount of their mineral constituents.

Canterbury Water.! New River Water.
Grains per gall. Grains per gall.

Carbonate of line. . . 1°39 Carbonate of lime . . 12°70
Sulphate of lime . . . 0°07 Sulphate of lime. . . 1°60
Nitrate of lime. . . . 2°04 Nitratevof lime. 2 . 1700
Macnesia.: . 9: . . . 0727 | Nitrate of magnesia. . 1:28
Aikaline chlorides. . . 3°41 | Chloride of sodium . . 2°02
Dede e sea cet in 5 OTAO Silene is 3 7s. 3. e026
Weiss ok 7-58 | Alumina, ete. . . . . ie

| Total. . 19°00

Thus in the New River water there is two and a half times
more mineral matter than in Canterbury water.

The kind of reaction which was observed is very similar to
that which M. W. M. Hafkine? found among two races of
Infusoria. A race living in a clear pond near Paris was
killed by an artificial infusion of hay and leaves in which
the same species of Infusoria was flourishing.

y. Reproductive Cycles.

Another possible explanation may be sought in the follow-

1 This analysis was kindly sent to me by Mr. 8. Harvey, the City
analyst.

* The analysis of the New River water is taken from Dr. J. A. Wanklyn’s
‘Water Analysis,’ 1896.

3 « Recherches sur |’Adaptation au Milieu chez Infusores et les Bacteries,”
par W. M. Hafkine, ‘ Anu. Inst. Past.,’ 1890.

220 ERNEST WARREN.

ing way. From much observation in breeding Daphnia it
seems probable that families have periods of reproductive
activity independent of physical conditions, such as tempera-
ture and the nature of the water, and perhaps in the “b”
families the generations on September 23rd marked the end
of a reproductive cycle. This supposition, however, would
not explain the sudden retardation in growth, and the death
of some of the individuals when Canterbury water was first
used.

It should be remembered that the mud and tumblers were
in a perfectly wholesome condition ; for after the death of
the families on putting in fresh Daphnia from the tank,
broods were produced in a normal manuer.

o. [The Poisonous Nature of the Water in which
Daphnia had been living for a Prolonged
Period.

The decadence of the “A” and “a” families was un-
doubtedly due to the condition of the water, for fresh
Daphnia became sickly in it, and produced but few young,
and they all died in about a month. That this result was
not due to the mere lack of oxygen is certain, for the con-
ferva and unicellular alge gave off large quantities of the
gas.

At the beginning of February the water was decanted
from the mud and conferva and filtered. It had a faint
brownish tinge. 200 c.c. of this water were evaporated over
sulphuric acid, and the residue was dissolved in about 5 c.c.
of water. On filtration a fairly clear amber-coloured fluid
was obtained. This was tested for proteids, but none were
found. The ammonium hydrate reaction for uric acid was
tried, but no indication of its presence could be observed.

Dr. Collie very kindly tested it, and he informed me that
he believed it contained a minute trace of an organic base,
but that the quantity present was so small that it was quite
impossible to ascertain its nature.

CHANGES IN ENVIRONMENT OF DAPHNIA MAGNA. PPA |

About a cubic centimetre of the concentrated solution was
injected hypodermically into a frog, but without any marked
effect.

The remainder of the water which had been filtered, and
had been kept for a month in a bottle plugged with cotton
wool, was put into two beakers, and Daphnia were placed in
them. The animals grew and reproduced in a normal way.
Thus the poisonous nature of the water had apparently
passed off.

All that can be said at present is that—

(1) Daphnia living in a small confined volume of water
with plenty of food and oxygen gradually become unhealthy,
‘their spines diminish in length, and reproduction ceases.
After a prolonged period they die.

(2) This water is injurious, though not as a rule fatal to
fresh Daphnia; the reproductive power, however, is very
quickly acted upon.

(8) Cyclops and Cypres were observed living in the water
apparently without hurt. This fact would almost seem to
indicate that the water becomes specifically injurious to
Daphnia.

(4) The injurious nature of the water seems to pass off
after a sufficiently long period.

In a considerable volume (1L0—40 htres) of water the
phenomena observed are slightly different. On stocking the
aquarium, say with a dozen Daphnia, after a month or six
weeks with favourable conditions of temperature and food
several hundred animals may be produced. ‘Then quite sud-
denly something appears to happen, and the greater number
die, young and old alike. A few, perhaps thirty, survive.
These will live for months without producing eggs. After a
very considerable time eggs are formed, and the Daphnia may
become fairly plentiful again, but this second swarm is never
so great as the first.

Considering the course of events in a small volume (200
c.c.) of water, we may perhaps interpret the above pheno-
mena in the following way.

Dae ERNEST WARREN.

Daphnia, like all living organisms, must continually be
throwing off into the water excretory matter, using this term
in its widest sense. ‘This matter, either in itself or through
its favouring the presence of certain bacteria, may feasibly
be supposed to be particularly injurious to Daphnia; for when
the Daphnia are fast disappearing, there may be a swarm of
Ostracods or Copepods. Thus the first swarm of Daphnia
may be supposed to render the water unfit for Daphnia life.
A few individuals, however, are strong enough to survive,
the rest die. Now, by some natural process, the water
gradually becomes purified (possibly by the action of plant
life), and at last the few Daphnia that are still alive are able
to reproduce.

Summary.

From the foregoing experiments certain conclusions of
some interest may be drawn. The curve of the time of
killing with salt is quite clearly not «a logarithmic curve, as
the usual method of stating Fechner’s supposed relation of
stimulus to effect might perhaps lead us to expect. Between
the limits of ‘8 per cent. and 6:0 per cent. solution, the rate
of killing appears to directly depend on the number of
inolecules (above the number contained in ‘8 per cent. solu-
tion) of salt which. beat on the Daphnia per unit of time.
With an increase of temperature the molecules are moving
with greater speed, and consequently strike the Daphnia
more frequently and with greater momentum, and the
chemical or physical reactions which take place are per-
formed with greater rapidity. Thus a Daphnia in 1°6 per
cent. at 3° C. dies in one hundred and five minutes, but at
29° C. in sixteen minutes.

The physiological condition of the animal at the time of
immersion into the salt solution has an enormous effect on
the resisting power. ‘Thus in the case of a number of
Daphnia plunged into ‘5 per cent. NaCl, whether they all die
in about twenty-two hours or live indefinitely depends on

CHANGES IN ENVIRONMENT OF DAPHNIA MAGNA. 223

their state of health at the time being. From this we may
infer that if a natural piece of fresh water containing Daphnia
were suddenly inundated with a certain quantity of salt
water, whether all the animals would be killed or not would
depend on the physiological condition of the animals at that
particular period. Supposing, for example, the water were
choked with excessive vegetation, then the population of
Daphnia would become extinct.

The physiological condition arrived at by acclimatising
Daphnia to *25 per cent. solution might certainly be expected
a priori to increase the resisting power to a stronger solu-
tion. In the experiments described this was found not to be
the case. Probably, although the acclimatised animals
appeared perfectly healthy, yet there was a certain weakness
in the constitution which caused them to succumb quicker
to the stronger solution than ordinary unacclimatised
Daphnia.

The effect of living in a confined volume of water on the
length of the spine is somewhat surprising, but I think the
evidence for it is quite overwhelming. The apparent direct
action of the environment on a character which has no
obvious connection with any change in the environment has
been observed by Darwin and others. Doubtless the length
of the spine is correlated with something which is acted upon
directly by the state of the water, and the difference observed
in the spinal length is merely the expression of this correla-
tion.

Living in a confined volume of water has a very marked
effect in decreasing the power of reproduction, both in the
number of generations and in the number of offspring in a
brood.

Sudden change from New River water to Canterbury
water, and vice versa, produced a pause in growth, and
some of the younger Daphnia died. Doubtless the mineral
character of a water is one of the numerous causes which
decide whether or not Daphnia are to be found living in any
particular pond or ditch.

224. ERNEST WARREN.

The supposed poisoning effect of Daphnia on Daphnia is
not new in principle, and it has considerable significance from
the point of view of epidemics, which so frequently arise
when from any cause one kind of animal becomes excessively
abundant.

In conclusion I wish to express my indebtedness to Pro-
fessor Weldon for his kind help and ready suggestiveness.

A REVISION OF THE GENUS STEGANOPORKELLA. 225

A Revision of the Genus Steganoporella.

By

v

Sidney F. Harmer, Sc.D., F.R.S.,
Fellow of King’s College, Cambridge; Superintendent of the University
Museum of Zoology.

With Plates 12 and 13.

Some months ago Professor A. C. Haddon presented to the
University Museum of Zoology at Cambridge a collection of
Polyzoa, obtained by him during his first expedition to
Torres Straits in 1888-9. The bulk of his collection
had previously been given to the British Museum, and had
formed the subject of a paper by Mr. R. Kirkpatrick ;! but
the material acquired by the Cambridge Museum, although
consisting mostly of small pieces, contained many species
which do not seem to have been represented in the other
part of the collection. Among these I observed three species
of Steganoporella, two of which appear to be undescribed.
One of these was of special interest from being well pre-
served in spirit, enabling observations to be made on its
structure. My results on this subject are not quite ready
for publication, and I shall at present merely indicate their
general nature.

In drawing up an account of the genus Steganoporella
I have made use of the following collections :—(1) the speci-
mens brought by Professor Haddon from Torres Straits ; (2)
other specimens in the Museum of Zoology at Cambridge,
mostly presented by Miss Jelly; (3) the collection of the

' «Sci. Proc. RK. Dublin Soc.’ (N. S.), vi, 1888-90, p. 608.

226 SIDNEY F. HARMER,

British Museum, for the opportunity of studying which my
best thanks are due to the Director, Professor EH. Ray
Lankester, and to Mr. Kirkpatrick, who has shown me not a
little kindness in giving me information; (4) one or two
specimens in the collection of the Manchester Museum; (5)
specimens sent to me from Jamaica by Mr. J. EH. Duerden,
and from Victoria by Professor W. Baldwin Spencer, to both
of whom I desire to express my indebtedness, as well as to
other friends who have unsuccessfully attempted to procure
specimens of Steganoporella.

Steganoporella is a genus of very striking appearance ;
and, as has happened in many other cases, its generic cha-
racters are so distinctive and conspicuous that the specific
characters have not hitherto received due attention. ‘Thus I
believe that the forms described by various writers as S.
magnilabris, Busk, belong to a number of different species,
and, in place of the two recent species given in Miss Jelly’s
catalogue,’ I am able to define no less than twelve species.

The only author who seems to have published the opinion
that most specimens of this genus are not necessarily to be
referred to S. magnilabris is Jullien,? who further alludes
to two undescribed species which he has dredged on the
coast of Liberia. It is probable that these are not included
in the material which has been at my disposal.

The Polyzoa belonging to this genus are characterised by
the large size of the zocecium and of the operculum. The
zocecium consists of a calcareous basal wall and four vertical
walls, which will be described as, respectively, proximal (=
aboral), distal, and lateral. The proximal and distal walls
are commonly somewhat oblique, their free edges being
situated more distally than their base-lines. The sixth or
‘‘upper”’ surface is covered, as in the Membraniporide, by a
chitinous membrane or ectocyst, the “epitheca” of most

1 «Syn. Cat. Recent Mar. Bryozoa,’ 1889. I give below my reasons for
referring Membranipora delicatissima, Busk, to Siphonoporella,
Hincks.

2 §Miss. Sci., Cap. Horn,’ vi, Zool., 1888, p. I. 79.

A REVISION OF THE GENUS STEGANOPORELLA. 227

authors, with which the base of the enormous operculum is
continuous. In zocecia from which the epitheca has been
removed, the four vertical walls end in a thin “ raised line,”
which outlines the entire zocecium, separating it from its
neighbours. Busk! regarded this as a “chitinous hollow
filament,” which he supposed to be a channel of communica-
tion between different parts of the zoarium. In incinerated
specimens the lateral walls of neighbouring zocecia may
appear separated from one another by a narrow slit in
place of the “raised line.” This is in fact the edge of a
chitinous layer separating contiguous zocecia, and prolonged
into the membranous epitheca. This agrees with the account
given by Nitsche? of the calcification of the zocecia of Mem -
branipora membranacea, in which the calcareous matter
is said to be formed in the middle of the chitinous ectocyst,
part of which is left on each side of it. In S. auriculata
the basal wall is covered externally by a chitinous ectocyst,
the limits of the zocecia being visible as a chitinous line, just
as on the upper surface.

The proximal part of the zocecium is covered by the
epitheca, which is tightly stretched across it; and there is
here no calcareous portion which projects above the level cf
the epitheca. The distal wall is usually raised above the
epitheca of the adjacent zocecia into a conspicuous calcareous
“oral arch,” the development of which differs in different
species.

The thin summit of the post-oral part of each lateral
wall will be described as the “edge.” Nearer the base the
proximal and lateral walls have a thickened granular or
tubercular calcareous portion, as in many species of Mem-
branipora. ‘This may be referred to asthe “shelf,” a name
which has already been used by Waters.’ It is constantly
present on the lateral walls, but may be evanescent on the

1 «Challenger Report,’ pt. xxx, 1884, p. 75.

2 « Zeitschr. wiss. Zool.,’ xxi, 1871, p. 455.

3 «Quart. Journ. Geol. Soc.,’ xliii, 1887, p. 51; Waters, however, used
the term only for what I describe below as the oral shelf.

228 SIDNEY F. HARMER.

proximal wall. It may also occur on the distal wall, giving
valuable specific characters, and when present here it is found
as a projection within the oral arch, and at a considerably
deeper level (fig. 13).

Immediately on the basal side of the shelf a porous “ cal-
careous lamina” takes its origin from the proximal and
lateral walls, forming a layer more or less parallel to the
epitheca. This is the “cryptocyst” of Jullien,! and the
space between it and the epitheca is the “ hypostegia” of the
same author. The Microporide, Steganoporellide, with the
Membraniporidz and certain other forms, are grouped to-
gether by Jullien as Diplodermata,? in allusion to the oceur-
rence of a cryptocyst distinct from the ectocyst. In most of
these forms the cryptocyst is not complete, but has a free
internal edge which limits an opening of varying size, the
** opesia.”

The cryptocyst of Steganoporella is always complete
proximally. As it passes distally, it sinks towards the basal
wall—in some species with a slight angular deviation from
the epitheca, in which case it joins the distal wall of the
zocecium (figs. 11 and 15) at a greater or smaller distance
from its base. In other species the ecryptocyst descends
steeply, often at right angles to its proximal portion, to join
the basal wall (fig. 10). The importance of the place of in-
sertion of the distal border of the cryptocyst as a specific
character has hitherto been completely overlooked. Since
the calcareous walls are more or less transparent, it follows
that in some species the basal wall seen from below shows
merely the origin of the four vertical walls, while in others
it shows in addition the insertion of the edge of the crypto-
cyst (fig. 27). This structure is developed as an outgrowth
from the proximal side of the zocecium, which in its young
state passes through a condition, with incomplete crypto-
cyst and large opesia, which is permanent in species of
Membranipora. ;

' «Bull. Soe. Zool. France,’ vi, 1881, p. 4 (sep.).
? See also Jullien, ‘Cap. Horn’ (t. cit.), p. I. 66.

A REVISION OF THE GENUS STEGANOPORELLA. 229

The cryptocyst extends through the body-cavity of the
zocecium, which thus occurs both above it and below it. Its
descending part is never developed so much as to form a
complete septum across the body-cavity, but it is always
perforated by a more or less circular hole (fig. 13). Through
this passes the tentacle-sheath of the polypide, which oc-
cupies the chamber on the basal side of the cryptocyst. The
tentacle-sheath does not completely fill the hole, so that
there is a free communication between the two parts of the
body-cavity.

The opening in the distal part of the cryptocyst is the
base-line of a calcareous “tube,” which projects into the
distal or subopercular chamber of the zocecium. That part
of the tube which is remote from the basal wall is always
well developed, and is usually clearly visible from above.
The structure which is thus seen as a projection from the
descending part of the cryptocyst is what I shall hereafter
term the “ median process,” whether it is merely the upper
wall of the tube (fig. 7) or is complicated by the outgrowth
of flanges, as in fig. 11, etc.

In species in which the cryptocyst descends vertically to
the basal wall, the opening of the tube is vertical, and cannot
be seen (fig. 2) unless the zocecium is looked into obliquely
from the distal end. In those in which the cryptocyst joins
the distal wall the opening is oblique, and can usually be
readily seen from above (fig. 13). The sides of the tube are
generally much less developed than its roof, and there may
be no tubular wall on the basal or distal side. In this part
the opening may be completely surrounded by the crypto-
cyst, of which it is a mere perforation, surrounded laterally
and above by upstanding walls (fig. 11, large zocecium). In
other cases (fig. 11, small zocecium) the cryptocyst is still
more incomplete, the sides of the tube usually diverging and
joining the basal or distal wall, according to the arrangement
of the cryptocyst. The position of the opening and the
extent of its tubular walls offer valuable specific characters.

The tube, which thus rises from the free surface of the

230 SIDNEY F. HARMER.

descending part of the cryptocyst, partially interrupts the
distal region of the body-cavity, so that a pair of spaces,
which will be referred to as the “ lateral recesses,” are found
one on either side of it. Jullien’ has quite correctly appre-
ciated the function of these cavities, which, as he points out,
contain muscles. I propose to give a more detailed account
of these muscles on a future occasion, and will for the
present merely state that they are of three kinds: (i)
divaricator muscles, which open the operculum ; (11) occlusor
muscles, for closing this structure; (i11) depressor muscles.
These last are inserted into a linear chitinous thickening
(fiz. 16, e. s.) of the epitheca on each side. These thicken-
ings will be termed the “epithecal sclerites.” Their form
differs in different species. Busk? described them as
‘‘furcate spicula,”’ although the furcate appearance was no
doubt produced by the insertion of the tendon of the de-
pressor muscle into the middle of the sclerite, which is often
angulated at this point, so that the vertical tendon seen in
perspective with the two halves of the sclerite may have the
appearance of a Y.

I think, with Jullien,® that there can be little doubt about
the function of the depressor muscles. They are to be
regarded as special modifications of the parietal muscles of
other Polyzoa, whose function is, by depressing the upper
ectocyst, to exert a pressure on the fluid of the body-cavity,
by which the polypide is extruded.t| The tendons, as shown
by Jullien, pass through the well-known lateral foramina of
such forms as Micropora and Thalamoporella; and
Jullien, in his memoir on the Polyzoa of Cape Horn, suggests
no less than thirteen generic types for recent and extinct
species characterised by differences in these foramina, which
he terms the “ opesiules.”” This application of Jullien’s prin-
ciple would result in assigning different specimens of S.

Gap. Horn, p..: 77.
2 «Challenger Rep.,’ pt. xxx, p. 75.

3 *Cap. Horn,’ pp. I. 80, 81.
‘ Cf. Nitsche, ‘ Zeitschr. f. wiss. Zool.,’ xxi, 1871, p. 426.

A REVISION OF THE GENUS STEGANOPORELLA. 231

magnilabris to different genera, but credit is due to this
author for having distinctly understood the purpose of the
opesiules. In Steganoporella distinct “ opesiules”? may
be formed by the concrescence of the median process with
the lateral walls of the zocecium. This is specially the
case in S. auriculata (fig. 8) and im 8. connexa
(fie36)

The tube is probably not to be regarded as a median struc-
ture, as may be concluded not only from the internal evidence
afforded by Steganoporella, but by a comparison with
some of its allies. In Siphonoporella nodosa, Hincks,'
of which I have been able to examine a specimen (labelled
“ Australia”’) belonging to the Manchester Museum, there is
a descending cryptocyst, which, as in some species of
Steganoporella, joins the basal wall and leaves a con-
siderable subopercular cavity into which a tube projects.
Although Hincks did not convince himself that this tube
opens into the proximal part of the body-cavity (and I have
myself not been able to demonstrate this in the dry spe-
cimen), there can be little doubt, on the analogy of other
forms, of the existence of the communication. ‘The tube
arises quite unilaterally from the descending cryptocyst, and
is pressed against one or other of the walls of the distal
cavity of the zocecium.

The Manchester collection contains a specimen labelled by
Miss Jelly as Steganoporella delicatissima, Busk.
Although the original figure of this species ? gives little idea
of its internal structure, Miss Jelly’s determination was
undoubtedly correct, and I am thus indebted to her for
having my attention called to a species which appears to
throw considerable light on the structure of Steganopo-
rella. Although Mr. Kirkpatrick has been unable to find
the actual type-specimen of M. delicatissima, he procured
for me a fragment of the type-specimen of the Alga
(Amansia pinnatifida) on which, as Busk points out,

1 ¢ Ann. Mag. Nat. Hist.’ (5), vi, 1880, p. 90, pl. xi, fig. 10.
2 «Quart. Journ. Mier. Sci.,’ N.S., i, 1861, pl. xxxiv, fig. 1.
VOL. 43, PART 2.—NEW SERIES. R

232 SIDNEY F. HARMER.

M. delicatissima constantly occurs; the fragment being,
moreover, from the locality (King George’s Sound, West
Australia) from which Busk records the Polyzoon. The Alga
is, curiously enough, covered by Membranipora bicolor,
Hincks,! which appears at first sight to correspond with
Busk’s description of M. delicatissima. I find the expla-
nation of this discrepancy in two specimens (co-types, from
King George’s Sound) of Amansia pinnatifida in the
University herbarium at Cambridge. One of these is
covered by M. bicolor, and the other by M. delicatis-
sima, both being strikingly alike when seen without magni-
fication.

M. delicatissima (figs. 42, 43) should clearly be placed
in the genus Siphonoporella. ‘The first impression pro-
duced by its appearance is that it is a spineless Membrani-
pora, with a large “aperture ” occupying nearly the whole
of the front surface, and filled by a transparent membranous
ectocyst, in which lies the small operculum. A small portion
of the front wall is calcareous, immediately on the proximal
side of the aperture. The calcareous cryptocyst descends
with a uniform slope from this region, and thus has no hori-
zoutal proximal portion asin Steganoporella. At about
the middle of the length of the zocecium the cryptocyst meets
the basal wall on one side, while from the other side a well-
developed tube projects into the subopercular portion of the
body-cavity. ‘This tube is so asymmetrical that the cavity of
the zocecium which is roofed by the cryptocyst is retort-
shaped, the junction of the tube with the cryptocyst being in
some cases a little complicated. ‘The proximal division of
body-cavity overlaps the base of the tube on one side, and in
some cases (as in figs. 42, 43) on the upper side as well.
The tube on the other side springs directly from the lateral
wall of the zocecium, and below from the basal wall along
the line z. The consequence of this arrangement is that the

1 «Ann. Mag. Nat. Hist.’ (5), vii, 1881, p. 148. The species is probably

nearly related to Siphonoporella, although perhaps not actually to be
referred to this genus.

A REVISION OF THE GENUS STEGANOPORELLA. 233

tube appears to be traversed by three more or less transverse
lines. The most superficial of these, when seen from above,
is the line x, which indicates the bending round of the cryp-
tocyst to join the actual base of the tube. This appears, at a
deeper level, as the line y, where the recurrent part of the
cryptocyst bends round to form the upper wall of the tube.
This fold is indicated in optical section to the left of the
figure. The third line, z, in the plane of the basal wall of
the zocecium, is the origin of the deeper or basal part of the
wall of the tube. These relations are further explained by
_ the diagrammatic fig. 43, representing an ideal longitudinal
vertical section of the entire zocecium.

The operculum of 8. delicatissima is very much smaller
than the comparatively gigantic opercula of Stegano-
porella. That of the zocecium shown in fig. 42 measures
only 90 w in diameter, while the smallest normal opercula of
any of the species of Steganoporella here considered
measure no less than 320 yu. There is at present no reason
for regarding the zoocia of Siphonoporella as dimorphic.
The opercula (in S. delicatissima) have a concentric
thickening bar, as in the “A opercula”’ of Steganoporella;
and the proximal ends of this bar project to a considerable
extent from the lower side in a direction at right angles to
the plane of the operculum.

The question arises whether Siphonoporella should
be regarded as distinct from Steganoporella. I think
the answer to this must be in the affirmative, while admitting
that the former shows many points of resemblance to certain
species of Steganoporella. Siphonoporella differs from
Steganoporella in the small size of its opercula (which in
S. delicatissima do not exceed 100 yw in diameter), in
the absence of any horizontal proximal part of the crypto-
cyst, and in the fact that the “area” bounded by the
“raised lines” and filled by the membranous epitheca is
usually not co-extensive with the frout wall of the zoccium,
The cryptocyst of 8. delicatissima is tubercular, but not
porous; the mouth of the tube may be surrounded above

934 SIDNEY F. HARMER.

by fine calcareous processes, giving it a fimbriated appear-
ance.

In Steganoporella evidence of asymmetry of the tube
is conspicuous in certain species, as in 8. lateralis (fig. 1),
where the condition hardly differs from that in Siphono-
porella, and in 8. magnilabris (fig. 10), where the
asymmetry, though less apparent at first sight, is equally
striking in reality.

In other species of this genus the tube tends to pase a
median structure ; and its appearance in most cases is much
modified by the outgrowth of lateral calcareous flanges from
its upper wall. These usually take the remarkable form seen
in figs. 3, 8, etc. In most species the roof of the tube can be
distinctly seen as a convex floor (fig. 10) to the cavity which
is formed by the development of these flanges. It is not
easy to suggest a satisfactory explanation of this structure.
The lateral flanges have the effect of more completely de-
limiting the lateral or muscular recesses. They also strengthen
the distal edge of the median process which corresponds
with the base-line of the operculum. I cannot find evidence
that the cavity of the median process contains any organ of
importance; and I think it not improbable that it prevents
the too forcible retraction of the epitheca by the contraction
of the depressor muscles. If the epitheca should be de-
pressed so far as to come into contact with the edges of the
cavity in question, the resistance of the fluid in the cavity
(which is quite closed basally) would probably act as a
cushion, which would be less likely to tear the epitheca than
would a sharp calcareous edge unaided by a fluid cushion.

The distal part of the cryptocyst has hitherto been spoken
of as if it descended equally both medianly and laterally.
Although this may be approximately true of some species,
as of S. Buskii (fig. 13), the arrangement is usually compli-
cated by the fact that the part which descends into the
cavity of the median process has a different slope from that
part which forms the floor of the lateral recesses.

One of the most striking features of the genus Stegano-

A REVISION OF THE GENUS STEGANOPORELLA. 20)

porella is the dimorphism of the zocecia, which usually,
though apparently not always, occurs. The dimorphism
is due not only to differences in the form and size of the
calcareous parts of the zocecia, but in an even more striking
way to differences in the opercula. These, in Stegano-
porella, are always strengthened by vertical bars of
chitinous substance, which stand out from their lower side
like the joists from the lower part of a floor. In the one
form of opercula (which, with their corresponding zocecia, I
shall designate as ‘‘a”’) the operculum is usually semicircular,
with the main strengthening girder or bar concentric with
its curved margin (fig. 19). These zocecia may be regarded
as the equivalents of the ordinary zocecia of the Cheilostomes.
In the “8” form the operculum is usually a good deal larger,
and has an entirely different form of strengthening bar,
which may be roughly A-shaped (fig. 41) or N-shaped (fig. 14).
The a and B forms of opercula appear to differ in their mus-
cular system, as I hope to show on a future occasion. A more
obvious distinction depends on the character of the chitin-
ous teeth borne by the opercula. While a opercula may be
quite toothless (fig. 19), or with two (fig. 15) or four (fig. 24)
strong teeth on the main thickening bar, or in one case (S.
magnilabris, figs. 45, 46) with numerous small submarginal
teeth, the B opercula are nearly always characterised by the
greater or smaller development of submarginal teeth (figs.
36, 38). In one case (8. alveolata, fig. 41) each of these
teeth fits when closed into a socket in the calcareous oral
shelf of the zocecium (fig. 12). I have found the opercula
eminently serviceable in the discrimination of the species.
The nature of the dimorphism of Steganoporella has
formed the subject of some discussion, though the sugges-
tions that have been made are mere guesses. Hincks and
Busk have regarded the epi-cryptocystal chamber as occial
in function, in the B form at least; although Jullien! has
rejoined that part of the cavity in question contains
muscles, and cannot be regarded as an internal ovicell. This
' Toe. cit. (1888).

236 SIDNEY F. HARMER.

criticism appears to me to lose sight of the fact that the
supposed ocecial cavity of Hincks and Busk was more than
the lateral recesses. I have no evidence which justifies me
in expressing a definite opinion on this subject, although I
have no reason to think that the dimorphism is connected
with sexual differences. The ratio between the a and B
forms is curiously different in different species. In the
majority of forms characterised by the possession of B opercula
with A-shaped thickening, the 8 form is found in large
numbers. In those with a f-shaped thickening, on the
contrary, this form of zocecium is always rare, and appears
to be disappearing altogether. This leads to the cases (S.
neozelanica, etc.) in which no B zocecia can be found at all.
In S. alveolata the reverse condition obtains, the a form
being very rare, almost the entire colony being composed of
B zocecia. This is the only species in which I have been able
to obtain spirit material in which the polypides are present ;
and it is obviously not well adapted for the examination of
the meaning of the dimorphism. I have at present been
unable to detect any trace of reproductive organs, but I am
able to state that polypides occur in the comparatively few
A zocecia, and I have not noticed any difference between
these and the polypides of the 8 form.

Steganoporella possesses no avicularia, although these
are present in its ally Thalamoporella. I am at present
inclined to regard the B form of zocecium as representing an
avicularium, and probably that form of avicularium, common
n the extinct allies of Steganoporella, which Jullien
1881) terms an “onychocellarium.” I am disposed to do
this largely in consequence of the similarity between its
muscles and those figured by Jullien (‘Cap. Horn,’ pl. xu,
fig. 3) in the avicularium of Beania magellanica. I am
aware of the fact that the occurrence of avicularia containing
polypides would be very unusual.

A tentative suggestion with regard to the function of avi-
cularia may be here made. Anyone who examines encrust-
ing and Escharan forms of Polyzoa must be struck by the

A REVISION OF THE GENUS STEGANOPORELLA. 237

idea that one of the principal dangers to which they are
subjected is the competition of other fixed organisms. An
excellent example of this is afforded by a specimen of the
encrusting form of 8. neozelanica, which I have found
growing over another Cheilostome with a very uneven surface
in such a way that the basal wall of the Steganoporella
had moulded itself over every irregularity of the form on
which it was growing, thereby completely closing every
zocecial orifice. Many Polyzoa are particularly subject to the
attacks of encrusting Polyzoa,—as, for instance, Lepralia
foliacea of our own coasts. In some cases these attacks
probably do little harm, because the basal parts of the colony
become covered by a calcareous thickening of its own which
occludes the zocecial orifices, and the zocecia with functional
polypides are those in the younger parts of the colony.

Although Steganoporella grows into large flat surfaces
which might form an excellent fixing-point for other Polyzoa ,
I have never seen any overgrowth of this genus by encrust-
ing Polyzoa in specimens which were in good condition, with
their full complement of opercula. I have, however, exa-
mined a colony of S. truncata which was largely covered
by Membranipora, Cellepora, and Smittia; and it was
obvious that some of these were growing on parts of the
Steganoporella which had lost their opercula. The others
were in parts in which the opercula were wanting here and
there, and it seems to me not unlikely that the zocecia had
really been dead, although they had not yet lost their
opercula. Another case of Cellepora growing on the Vin-
cularian form of §. neozelanica is capable of being ex-
plained in a similar way.

I venture to suggest that certain of the external features
of a Polyzoon colony may be correlated with the discourage-
ment of the fixation of the larve either of Polyzoa or of
other encrusting animals. Many of the irregularities of the
surface, such as the armature of oral or marginal spines, may
act in this way by making the surface irregular and unfit for
the attachment of larve; and in particular it seems to me

238 ; SIDNEY F. HARMER.

probable that avicularia and vibracula may contribute to-
wards the same result. In the case of Steganoporella,
the B opercula, with their formidable teeth, may protect the
colony by the destruction of the larvee of Polyzoa or other
animals which are fixed in their adult state. The a opercula
may also take their share in this work, and would be parti-
cularly effective when furnished with teeth. It may be noted
that the a opercula are provided with two or four powerful
teeth in several of the species in which the B opercula are
apparently vestigial or completely absent. The disap-
pearance of the B opercula may in fact have been facilitated
by the occurrence of teeth on the a opercula.

The fixation of a Polyzoon larva is a deliberate process,
and does not take place until the larva has wandered about
over the surface of fixation for some time, rotating by its
cilia as it does so. During this process it may easily be sup-
posed that it would sooner or later be brought within the
reach of an avicularium in genera so provided, or of a B
operculum in Steganoporella, one closure of which would
be sufficient to destroy any intruding larva. The relations
of the oral shelf of the 8 form are by no means adverse to
this idea, particularly in 8. alveolata, but the cavity above
the shelf, in that species at least, is not adapted for the per-
formance of an ocecial function.

The nature of the dimorphism of Steganoporella may
perhaps in the future form the subject of direct observation
in some locality where suitable species are abundant.

Descriptions of the Species.

The species of Steganoporella form an interesting study
in evolution. ‘The complicated arrangements connected with
the distal part of the cryptocyst can be traced from a simple
to a more differentiated condition, and the former can be
compared with the arrangements of other genera. Certain
forms show a considerable range of variation; but on the
whole the characters of each species are well marked, and do

A REVISION OF THE GENUS STEGANOPORELLA. 239

not appear to vary to any great extent even in specimens
from widely different localities. In characterising the species
I have found the following features of special service :

(1) The opercula (A and B forms).

(i) The arrangement of the descending or distal part of
the cryptocyst.

(ii) The form of the tube and of the median process.

I have not derived any special assistance from the rosette-
plates, a character which, in the hands of Mr. Waters in
particular, has given valuable aid in the discrimination of
species. ‘he rosette-plates of Steganoporella are large
and conspicuous. Their typical arrangement seems to be
identical with that described by Nitsche for Membrani-
pora membranacea.! ‘The zoccia are in longitudinal rows,
those of adjacent rows usually alternating, so as to give a
regular quincuncial disposition. Hach zocecium typically
communicates with its neighbours by two proximal, two
distal, and four lateral rosette-plates on each side. It has
typically six neighbours, and it is connected with each one
by two rosette-plates, although there are many deviations
from this rule. I am unable to point out any constant cha-
racters by which the rosette-plates of one species differ from
those of another species, while in one and the same colony
very different conditions may obtain in neighbouring zocecia.
As an instance of this I may mention the case of a fragment
of the encrusting form of 8S. neozelanica, in which the
proximal wall of four zocecia could be examined from the
inside. In one of these there were two large watch-glass
shaped *rosette-plates with their concavity opening into the
distal zocecium ; in a second there were two similar rosette-
plates with their convexity in the distal zocecium ; in a third
two flat rosette-plates were present ; and in the fourth none
could be discovered.

In 8. buskii, while four lateral rosette-plates may occur,
other zocecia may have only three, or even two. The proxi-

1 «Zeitsehr, f. wiss. Zool.,’ xxi, 187], p. 421 (fig. 1).
> Cf, Waters, ‘Challenger Reports,’ pt. Ixxix, 1888, p. 18,

240 SIDNEY F. HARMER.

mal or distal rosette-plates may be of the typical number
(two), situated on the basal side of the insertion of the cal-
careous lamina, or each of these may fragment into as many as
three pieces placed close together (fig. 33). In 8. truncata,
although the typical number of lateral rosette-plates may occur,
one zocecium was noticed to have three vertically arranged
rosette-plates instead of the usual horizontal series of four.

It is obvious from what has been said that the relation of
the distal rosette-plates to the line of insertion of the crypto-
cyst is not the same in all species. In those in which the
cryptocyst joins the distal wall at some distance from the
base the distal rosette-plates are typically found, one beneath
the floor of each lateral recess (fig. 33). In species in which
the cryptocyst joins the basal wall the rosette-plates of the
distal wall are of course entirely distal to its insertion. The
subopercular cavity is in fact part of the body-cavity, what-
ever the relation of the cryptocyst, and the distal rosette-
plates maintain their position irrespective of the behaviour of
the cryptocyst.

Methods employed.—For the examination of the muscular
system I have found it convenient to remove the basal wall
of the zocecia. This may easily be done by embedding a
piece of spirit material (not decalcified) in paraffin, and
cutting away the basal wall with a scalpel after the paraffin
has cooled. On dissolving out the paraffin the zocecia can be
stained and mounted in Canada balsam. The removal of the
basal wall greatly facilitates the examination of the internal
anatomy of the zocecia.

The preparation of the opercula has been made by the
following method, which has enabled me to obtain satisfac-
tory evidence of the structure of small unique specimens
without in any way destroying their value. The fragment
of the colony is boiled for two or three minutes in a 4 per
cent. solution of caustic potash (although a stronger solution
might be used with impunity). The opercula are then brushed
off, or if necessary, removed, with the epitheca, by the aid
of aneedle. The calcareous parts are washed and reserved

A REVISION OF THE GENUS STEGANOPORELLA. 241

for further examination, while the opercula are placed in a
test-tube with nitric acid (which should not exceed about 50
per cent.) and boiled for two or three minutes. I have found
this procedure specially necessary in the case of dry speci-
mens, in which the dried tissues in connection with the
orifice are by no means easy to remove from the lower side
of the opercula. Even after treatment with nitric acid it is
often necessary to brush or dissect away these remains, in
order to obtain clean preparations of the opercula, which are
mounted in Canada balsam after staining with picric acid.
If the material is not specially valuable the opercula may be
prepared by boiling the dry fragment of a colony in nitric
acid ; but the other method is preferable, in that it permits
the examination of the dry calcareous parts and of the
opercula of the same fragment. In dry mounts of specimens
from which the epitheca has not been removed some in-
formation with regard to the characters of the calcareous
parts may be obtained by wetting the epitheca, a procedure
which makes it for the time more transparent.

The examination of the calcareous parts could hardly have
been made except by employing some device for rotating the
fragment, so as to be able to see it from different points of
view. I have used for this purpose a small cylinder, as
described in my paper on Lichenopora,! to which the piece
of the colony could be temporarily fixed.

Steganoporella, Smitt (Steginoporella, Smitt, 1873).

Zoarium encrusting, Hemescharan or Escharan. Zocecia
typically dimorphic, completely covered in front by a mem-
branous epitheca, the oral region alone rising as a calcareous
arch above its level. Opercula of great size, rarely less than
320 in diameter, and often much larger, strengthened by a
girder (main sclerite) which projects from the lower surface,
and often by additional girders. Cryptocyst a more or less
horizontal, porous plate proximally, separated from the
epitheca by the depth of a tubercular calcareous shelf ;

1 «Quart. Journ. Mier. Sci.,’ xxxix, 1897, p. 74,

242 SIDNEY F. HARMER.

distally descending to join the basal or distal wall of the
zoceciun. The descending part of the cryptocyst is per-
forated by a passage or tube, through which the tentacle-
sheath passes to the orifice, the walls of this passage being
developed at least above. The parts of the cavity on either
side of the tube form more or less deep lateral recesses, which
contain the opercular muscles and those which depress the
epitheca. The tube is usually produced into distal and lateral
flanges which limit a hollow, the cavity of the median process,
which opens upwards into the space beneath the epitheca.
Avicularia of the ordinary type and external ovicells wanting.

In arranging the species of Steganoporella somewhat
different results would be arrived at according to whether
the characters of the opercula or of the cryptocyst and of
the tube are taken as the basis of the arrangement. The
possible affinities of the species may perhaps be indicated by
taking three main divisions, as follows :

(i) B opercula, if present, with a M-shaped thickening bar
or main sclerite;! a opercula undifferentiated or with two
teeth on the main sclerite.

(ii) B zocecia apparently wanting; a opercula with four
teeth on the main sclerite.

(iii) B opercula with a A-shaped main sclerite.

The cryptocyst usually joins the basal wall in sections (i)
and (11), while it joins the distal wall in most of the species
included in section (111).

(i) B Opercula, if present, with a M-shaped main
sclerite; A Opercula undifferentiated, or with
two teeth on the main sclerite.

1. Steganoporella lateralis, MacGill. Figs. 1,19, 20, 27.

S. lateralis, MacGill., Mon. Tertiary Polyzoa Victoria,
‘Trans. Roy. Soc. Victoria,’ iv, 1895, p. 53, pl. vi, fig. 18.

Cryptocyst joining the basal wall, angulated and thickened

1 The term “ sclerite ” may conveniently be used for any definite thicken-

A REVISION OF THE GENUS STEGANOPORELLA. 243

at the commencement of the descending portion. Tube well
developed, rising very asymmetrically from the descending
cryptocyst; its opening vertical, completed by the basal
wall, or if complete not far raised above the basal wall. The
formation of a median process distinct from the tube is
indicated only by a pair of unequally developed horns on the
upper wall of the tube. 8 opercula rare, with N-shaped main
sclerite, but without basal sclerite ; submarginal teeth long,
strong, and recurved, confined to the distal half of the
operculum. A opercula undifferentiated. Insertion of the
cryptocyst, as shown on the back of the zocecium, usually
produced proximally into a deep asymmetrical sinus
(fig. 27).

(a) Tahiti; Manchester Mus., Miss H. C. Jelly.!

(b) Tahiti; Hincks Coll., Brit. Mus., 99. 5.1, 261 [from
Miss Jelly’s collection].

(c) Torres Straits; Haddon Coll., Cambridge Mus., 24..2.98
[Muddy Creek, Victoria (Tertiary), MacGillivray].

The material on which the diagnosis is based consists of
three small encrusting specimens, two of which, from Miss
Jelly’s collection, were no doubt obtained at the same time.
The specimen from Torres Straits is without opercula.

Of all the species I have examined this one most nearly
resembles a Siphonoporella, and I have accordingly put it
at the head of my list. The tube (fig. 1) arises quite asym-
metrically from the cryptocyst, as pointed out by MacGil-
livray, sometimes from one side, sometimes from the other,
and its position in a series of zocecia does not obey any
obvious law. The change from a right-handed to a left-
handed zocecium takes place abruptly in the course of a
ing of the operculum or epitheca, following a practice usual in entomology.
The ‘‘ main sclerite” is the principal thickening bar of an operculum, which
bears the tubercle for the insertion of the occlusor tendon.

1 The localities given are those of the specimens which I have myself exa-
mined. The specimen first mentioned is the one which I regard as the type-
specimen in the case of the new species. In the remaining species ‘‘ B. M.”
= British Museum, “C. M.” = Cambridge Museum, tlie register dates being
given in both cases.

24.4, SIDNEY F. HARMER.

longitudinal row of zocecia. If the series bifurcates, the
two daughter-zocecia may have the same asymmetry as their
parent, or one of them may have the converse symmetry ; or
both may be converse. I suspect that the asymmetry 1s cor-
related with the position of the retracted polypide, and that
the tentacles lie in some zocecia on the right side, and in the
others on the left side. In the specimen figured the tube
springs from the (apparent) right side of the subopercular
cavity. The proximal wall of the right’ lateral recess is not
apparent in the figure, while that of the left recess is just
visible. Between this wall of the left lateral recess and the
tube the basal wall is exposed to view from above. On
turning the zocecium over this appears as a deep sinus (fig.
27) passing proximally and asymmetrically in correlation
with the asymmetry of the tube itself. A view from this
side at once shows that there is considerable variation in
these respects. ‘The condition shown in the upper zocecium
of fig. 27 corresponds with that of fig. 1; that shown in the
lower zocecium indicates that the cryptocyst does not any-
where touch the distal wall, while another condition is
found when the cryptocystal floor of the lateral recess
meets the distal wall (in any case very low down) on both
sides.

The upper border of the opening of the tube is produced
into two points, which are typically asymmetrical, that on
the side of the sinus being more developed than the other,
as indicated by fig. 1. The edge (see p. 227) of the zocecium
is hardly as high as the calcareous post-oral shelf, from
which it is separated by a distinct furrow. The shelf is
strongly tubercular, but is not so deep as in most species.
The horizontal part of the cryptocyst is accordingly com-
paratively little depressed below the level of the epitheca ;
it is well developed, thick, and tubercular, and has small
pores. A strong tubercular continuation of the shelf runs

1 It will be convenient to describe what is actually seen in the figures,

without alluding on each occasion to the fact that the figure has been re-
versed by the microscope,

A REVISION OF THE GENUS STEGANOPORELLA. 945

across the zocecium, along the line where the descent of the
cryptocyst commences. The descending portion joins the
horizontal portion at a distinct angle, and the tube springs
from it at a deeper level than the tubercular edge. As is
usual in species in which the cryptocyst descends verti-
cally, the basal wall is well exposed from above. ‘The oral
shelf is completely absent. The oral arch is well raised.
The epithecal sclerites are rather long, nearly straight
proximally, curving outwards distally towards the ends of
the main sclerite of the operculum, which they nearly reach.
The epitheca is delicate and transparent.

The characters of the B zocecia have not been observed ;
but two B opercula have been found with respectively ten
(fig. 20) and nine submarginal teeth, but otherwise closely
agreeing with one another. The tendons of the occlusor
muscles are shown in the sketch, that on the right side being
displaced from its natural position. They are inserted, as
in the case of the opercula of Steganoporella generally,
into a distinct tubercle (a), which is marked by a group of
fine dots which doubtless correspond with a fibrillar insertion
of the tendon into the operculum. The main sclerite (6 c)
of the operculum is M-shaped; and, as seen from the inner
or basal side, is an oblique girder springing from the oper-
culum along the line c, and with a free edge at b. This edge
rises further from the plane of the operculum on the proxi-
mal side of the occlusor tubercle, and projects as a pointed
lobe whose edges are formed by the parts d and e, between
which there is a deep concavity sinking down to the level
of the proximal end of the base-line (c) of the sclerite.
This upstanding lobe is supported by a buttress or sclerite
(f), which passes down to the plane of the operculum. The
line c, the buttress jf, and (in some cases) the submarginal
tooth-bearing sclerite, being the parts which are most in the
plane of the operculum, are conspicuous as dark lines on the
opercula in an ordinary dry preparation seen from above. In
the present species, which is characterised by the delicacy of
its opercula, the lines c and * can be seen in a dry prepara-

246 SIDNEY F. HARMER.

tion from above. The free edge d is in most species some-
what thickened, so that the first impression, in examining a
transparent preparation, is that the main sclerite bifureates
proximally into two limbs, one of which is really the base
line of the sclerite, the other its free edge. The intermediate
oblique portion of the sclerite may be so thin as to appear to
be a foramen; but in some cases at least I have satisfied
myself that the apparent foramen is merely a thin part of
the sclerite.

A feature of the B operculum of 8. lateralis, to which
attention must specially be directed, is the absence of a
basal sclerite, this being indeed the only species in which I
have found this condition to occur in the B opercula.

The general structure of the a opercula (fig. 19) is very
similar to that of the 8 form. The differences are—its
smaller size and greater relative breadth ; the absence of
teeth; and the somewhat more distal position of the occlusor
tubercle. As this type of operculum does not appear to differ
widely from those of other Cheilostomes, I describe it in the
present paper as “undifferentiated.”

The diameter of the B opercula is about 515 w, and that
of the a opercula about 415 p.

2. S. sulcata, n.sp. Figs. 2, 14—17, 28, 29.

Steganoporella magnilabris, Hincks, ‘ Ann. Nat. Hist.’
(5), xiii, 1884, p. 358; ‘Journ. Linn. Soc.,’ xxi, 1889,
p. 130.

Cryptocyst joining the basal wall, angulated and thickened
at the commencement of the descending portion. Tube
short, its opening vertical and completely separated from the
basal wall. Median process variable, usually broad and with
a shallow cavity, the deepest part of which is a median lon-
gitudinal groove (hence sulcata); or narrow and T-shaped.
B opercula rare, with N-shaped main sclerite; submarginal
teeth well developed, sometimes long and weak, confined to

A REVISION OF THE GENUS STEGANOPORELIA. 247

the distal half of the operculum, which has a distinct basal
sclerite. A opercula with two strong teeth on the distal
part of the main sclerite; the teeth sometimes vestigial.
Back of the zocecium showing the insertion of the cryptocyst,
distal to which the basal wall is commonly thin, so as to form
a rounded fenestra, through which the tube is visible.

(a) Isle des Neufs, Amirante Is., Indian Ocean, Voy.
“ Alert,” 15 fathoms (B. M., 82.10.18, 88).

(6) Darros I. (Amirante Is.), Voy. “ Alert,” 22 fathoms
(5. Ms, 82:10:18, 125).

(c) Galle Point, Ceylon, Dr. Ondaatje (B. M., 85.7.27, 1).

(d) Mergui, Burmah, Hincks Coll. (B. M., 99.5.1, 28).

(e) Mergui, Burmah, Dr. Anderson (B. M., 85.12.29, 10).

(f) [Possibly N. Australia.] ‘On Avicula margari-
tifera” (B.M.).

All the specimens are encrusting. The largest, from
Darros Island, encrusts the greater part of a cylindrical piece
of coral limestone, about 85 x 30 mm. ‘The existence of the
specimen (d) in the British Museum collection enables me to
state that ‘““S. magnilabris” recorded by Hincks from the
Mergui Archipelago belongs to this species.

S. sulcata appears to be closely allied to 8. lateralis,
from which, however, the characters of the tube are sufficient
to discriminate it. The opening of the tube is circular and
complete, and it is often well separated by a portion of the
descending cryptocyst from the basal wall, a large part of
which is visible from above. A median vertical calcareous
wall usually rises from the roof of the tube, and typically
diverges above into the two flanges which are seen to unite
in the median groove (fig. 2) which is one of the most strik-
ing features of the species. A transverse section through
the tube and its annexes could accordingly be represented
by a circle on which is standing a short-legged Y with very
divergent arms. On the analogy of 8S. alveolata (see p. 229)
it may be confidently stated that the tentacle-sheath passes
through the opening of the tube round the distal end of the
median process. The transverse distal border of the latter is

VoL, 45, PART 2.-NEW SERIES. s

248 SIDNEY F. HARMER.

accordingly connected with the opening of the tube by a pair
of nearly vertical flanges, which are situated in a transverse
plane ; thus forming a smooth surface over which the tentacle-
sheath can glide easily in its movements of eversion and
retraction. In the type-specimen (a) the distal margin of
the tube is produced into two strong horns, which curve
downwards towards the basal surface. It is probable that
these serve as the point of origin of muscles or ligaments
which regulate the movements of the tentacle-sheath.

In some cases (particularly in specimen d) the origin of the
tube from the cryptocyst is almost as asymmetrical as in
S. lateralis, though without the deep sinus of the latter.
This condition is not so easily observed in other cases.

In the specimens (f) and (d) there are some interesting
variations in the median process. In some zocecia this struc-
ture has thetypical form (as in fig. 2), being broad and markedly
sulcate. At the opposite extreme the process is T-shaped
(fig. 29) as seen from above, with nearly transverse distal
border, ending in a sharp point on each side, a linear lon-
gitudinal portion connecting the distal border with the
descending cryptocyst. Hven in extreme cases the linear
portion slightly widens proximally, and an indication of the
longitudinal groove can usually be made out here. All
stages exist between this condition and the typical suleate
form.

The edge in this species is but slightly raised. The post-
oral shelf is narrow, especially proximally, and is sharply
separated from the cryptocyst ; it 1s continuous with a thick-
ened tubercular portion which runs along the angulated part
of the cryptocyst. The transverse thickening is not quite
complete medianly in the single B zocecium (fig. 2) which has
been examined. ‘This differs from the a zocecia in the
greater size of the distal or subopercular cavity. The oral
shelf is quite absent. The condyles for the origin of the
hinge of the operculum are conspicuously long, and at right
angles to the lateral walls of the zocecium. The oral arch is

® moderately raised above the level of the epitheca, The

A REVISION OF THE GENUS STEGANOPORELLA,. 249

cryptocyst is not much depressed proximally, and is thick,
with rather large pores. Some asymmetry in the floors of
the two lateral recesses is not uncommonly noticed; and the
asymmetry, when present, is indicated on the basal wall.
This is usually very characteristic, and is distinguished by
the occurrence of a large distal region, limited proximally by
the insertion of the cryptocyst, and often covered by a wall
which is much thinner than the rest of the basal wall, so that
the tube is clearly visible through the fenestra thus formed.
In the single B zocecium examined the descending part of
the cryptocyst meets the basal wall and the two lateral walls
at a long distance from the distal wall. The epithecal
sclerites are rather long and conspicuous, and start from the
base of the operculum. ‘The epitheca is thin and _ trans-
parent.

The single B operculum examined of the type-specimen
(fig. 14) has eight well-developed teeth, most of which are
conspicuously long, and apparently weak and flexible. ‘They
are confined to the distal part of the submarginal sclerite,
which fades away proximally. ‘The main sclerite is N-shaped,
and the operculum has a distinct basal sclerite. The a oper-
cula (fig. 15) have two very conspicuous distal teeth on the
main sclerite. The sclerite f, which acts as a buttress to the
proximal projection of the main sclerite, appears in this
species at least to be a hollow prolongation of the main
sclerite which runs into the chitin of the outer surface of the
operculum.

The opercula of this species are as variable as the calcare-
ous parts: While those of the specimens (b) agree with the
type-specimen except in having somewhat shorter teeth in
the a form, those of specimens from other localities are
somewhat different. The B opercula are always rare, and I
have been able to examine only one of specimen (d) and one
of (f). In the former (fig. 16), from the Mergui Archipelago,
there are nine stiff erect teeth, the distal ones being long;
the edge of the main sclerite is at a considerable distance
from the border of the operculum, The teeth of a are

250 SIDNEY F. HARMER.

shorter than in the type, and barely project beyond a slight
web-like lamella which connects them along the distal part of
the main sclerite. In f, possibly from N. Australia, the B
operculum (fig. 17) is short and broad,’ its main sclerite
otherwise resembling that of the type, but it has only four
teeth, which are stout and erect. The teeth of a are vesti-
gial, and their web-like connection is just indicated.

A mounted fragment of specimen (b) shows a curious
abnormality. One of the zocecia is unusually large, and has
a twin operculum, formed of two halves, each of full size,
with its own convex border ; but the two are united laterally,
their main sclerites being here continuous as well as the rest
of the opercula. The zocecium has a partial calcareous
septum dividing the proximal part only of the cryptocyst
into two halves. This septum is in the line of union of the
two halves of the operculum, as is also the single median
process of the zocecium. The growing edge of the colony
had at this point met another lobe of the same colony. The
interference thus produced probably resulted in the imperfect
longitudinal division of this part of the growing edge. The
double zocecium is separated from the point of union of the
two lobes by two imperfect zocecia, without orifices or median
processes.

The diameter of the B opercula is about 460 ; that of the
A opercula averages about 470 au, the extreme measurements
taken being 350 mw (f) and 540 mw (b), both these extremes
departing considerably from the mean of their own specimen.

3. S. tubulosa, n. sp. Figs. 3, 22, 238.

S. magnilabris, Hincks,? ‘ Ann. Nat. Hist.’ (5), viii, 1881,
p. 7; and (5) ix, 1882, p. 123 (“ Bass’s Straits ”’).

Cryptocyst joining the basal wall, angulated and often
1 Considerable variations occur in other species in the relative breadth of
the opercula.

2 It may be presumed that Mr. Hincks’s remarks refer to the specimen
here described,

A REVISION OF THE GENUS STEGANOPORELLA. 251

much thickened at the commencement of its descending
portion, which is usually far from the condyles. ‘Tube origi-
nating far below the angle of the cryptocyst, conspicuously
long, with a complete wall well raised above the basal wall ;
its opening nearly vertical. Median process formed by
distal and lateral upgrowths from the roof of the tube, which
is largely exposed as the floor of the wide cavity of the
median process. B opercula rare, broad and short, with
strong M-shaped main sclerite, the insertion of the occlusor
muscle being unusually elongated. Submarginal teeth ves-
tigial. A opercula relatively small, weak, and undifferen-
tiated.

Curtis I., Bass Strait (Hincks Coll., B. M., 99.5.1, 29).

The specimen to which this description refers is a large
KEscharan or bilaminar plate, about 70 mm. long, probably
part of a larger colony. The surface is undulating, and
although no secondary plates are given off, one is apparently
developing as a ridge near the peripheral edge. Mr. Hincks
had merely labelled the specimen ‘‘ Curtis,” but this, as I am
informed by Mr. Kirkpatrick, is Curtis Island in Bass Strait.

The conspicuous features of this species are the extremely
long tube (fig. 3) and the great length of the post-opercular
(proximal) part of the zocecium, due in large measure to the
distance by which the condyles are separated from the base
of the median process. The Escharan habit should not be
left out of account. I am inclined to think that Smitt,
Hincks, and others have gone a little too far in denying the
value of the characters of the zoarium in distinguishing
species.

The edge is unusually high, and is the summit of a ridge,
triangular in transverse section, which is sharply separated
laterally from the post-oral shelf. This is well developed,
tubercular, and rounded, and is well separated from the
cryptocyst. The oral shelf is smooth and narrow ; the con-
dyles are small, the oral arch well raised. The cryptocyst 1s
thick and tubercular, with small pores. It is sharply angu-

2 SIDNEY F. HARMER.

lated where it begins to descend, and the angle is usually
greatly thickened by a tubercular transverse portion, which
may extend, in the middle, proximally so as to obliterate
some of the pores. ‘The parts of the cryptocyst which bound
the lateral recesses are vertical. The tube is complete all
round, its wall being unusually well developed on its deep or
basal side. The opening is well raised above the basal wall
of the zocecium. ‘he cavity of the median process is not
very deep, the convex roof of the tube forming its floor, and
being clearly exposed to view from above. The lateral and
distal boundaries of the cavity are well developed. A view
of the basal wall of the zocecia shows clearly the insertion
of the cryptocyst. The epithecal sclerites are short and deli-
cate, just overlapping the angulated edge of the cryptocyst,
but not nearly reaching the operculum. 8B zocecia have not
been observed.

The B opercula (fig. 28) are very rare, and only three (one
of them damaged) have been found. They are short and
broad, and they agree in possessing a very strong M-shaped
main sclerite, the insertion of the occlusor muscle being of
vreat size, and much elongated transversely. The proximal
projections of the main sclerite are much prolonged into
spout-like lobes, which are concave externally. The basal
sclerite is strong. This operculum is almost unique among
B opercula in having no submarginal ' teeth, these structures
being, however, represented by vestiges, which are merely
inconspicuous rounded lobules. The a opercula (fig. 22) are
small, and belong to the undifferentiated type ; the buttresses
of the proximal projections of the main sclerite are well
developed. The average diameter of B is 530 yw, that of the
specimen figured being 560». The average diameter of a is
420 u, the range being from 370 to 470 yp.

1'The teeth do not always appear submarginal in the sketches. The
boiling with strong nitric acid is probably responsible for the disappearance
of the very delicate margin which I find in the opercula of many species (as
in fig. 88) outside the tooth-bearing sclerite. I believe this delicate margin
to be a normal feature of the opercula.

A REVISION OF THE GENUS STEGANOPORELILA. 203

A. S. simplex, n. sp. Figs. 7, 21.

Zocecia of large size. Cryptocyst joining the distal wall
close to its origin from the basal wall; angulated andthickened
laterally at the commencement of its descending portion.
Roof of tube short, thick-walled, and tubercular ; the opening
vertical and separated from the distal wall. Median process
not distinct from the tube. B zocecia not found. A opercula
with two strong recurrent teeth on the main sclerite.

Darros Is. (Amirante ts.). (B. M., 82.10.18, 125.)

This species is founded on a single encrusting fragment
removed from a dry preparation which otherwise consisted
of S. sulcata. It differs from that species in its larger size,
in the fact that the ecryptocyst joins the distal wall,’ and in
the remarkably simple character of the tube and median pro-
cess, the latter being indeed hardly distinguishable from the
tube. The edge is but slightly raised. The post-oral shelf is
boldly tubercular, deep, and descending steeply to the erypto-
cyst, which is thus a good deal depressed; the shelf is less
developed proximally. ‘lhe oral shelf is present, but is narrow
and hardly tubercular. The condyles (for the hinge of the
operculum) are blunt and massive. The oral arch is strong
and moderately raised. The cryptocyst is thick, very tuber-
cular, and with small pores; its descent is oblique, though
with a steep slope. The tube is not much more than a mere
perforation in this oblique partition, its upper border being,
however, developed into a short but massive and tubercular
portion, which thus forms a spout-lke prolongation of the
perforation in the cryptocyst (fig. 7). The thickening of the
cryptocyst at the descent of the lateral recesses may slightly
extend on to the base and sides of this tube, thus giving rise
to a hardly appreciable concavity, which is all that can be
compared with the cavity of the median process. The epi-

1 A larger quantity of material might perhaps show that the union was
sometimes with the basal wall in the neighbourhood of the distal wall,

254, SIDNEY F. HARMER.

thecal sclerites are long and conspicuous, and start from the
operculum. The epitheca is thick. The A opercula (fig. 21),
though resembling those of 8S. sulcata in the existence of
two distal teeth, differ from them in that the teeth are more
recurved. The base line (c) of the main sclerite bends
inwardly, at its proximal end, much nearer the occlusor
tubercle than in S. sulcata. The operculum figured
measures no less than 610 » in diameter.

5. S. connexa,n.sp. Figs. 6, 18.

Zocecia of large size. Cryptocyst joining the distal wall
close to its origin from the basal wall, not angulated at the
commencement of its descending portion in young zocecia,
thickened and angulated in old zocecia. Roof of tube long,
greatly developed, the opening nearly vertical, invisible
from above, separated from the distal wall. Cavity of the
median process shallow, its walls being all strongly tuber-
cular. The distal border of the median process is thick, and
joins the condyles; the sides are greatly developed wings,
slightly convex above, and unite with the sides of the zocecium
in such a way as to leave two foramina or ‘ opesiules ”
on each side for the passage of tendons.) A zocecia not
found. Bs opercula broad and strong, with strong submar-
ginal teeth which begin not far from the base of the oper-
culum.

John Adams’ Bank, H.M.S. “ Herald,’ Busk Collection
(B. M., 99.7.1, 408).

There is some uncertainty with regard to the position of
“John Adams’ Bank,” a locality from which, as Mr. Kirk-
patrick informs me, a number of specimens in the Busk col-
lection were obtained. The slde with this label contained
not only a specimen of S. connexa (the only one I have
seen), but also one of S. magnilabris, Busk. The latter

1 These were actually made out, passing through the opesiules.

A REVISION OF THE GENUS STEGANOPORELLA. 255

species has a wide distribution, but the specimen in question
more closely corresponds with those from the West Indies
and Abrolhos I. (coast of Brazil) than with any others I have
seen. A slide in the Busk collection at the British Museum
(referred to on page 176 of the “Challenger Report,”
part xxx) is labelled “ John Adams’ Bank, North Atlantic,”
as I am informed by Mr. Kirkpatrick; while the Bank is
said to be in the South Atlantic on page 36 of Part III of
the British Museum Catalogue of Polyzoa. I am indebted
to Mr. Kirkpatrick, to Captain Tizard of the Hydrographic
Department at the Admiralty, and to Captain Froud of the
Shipmasters’ Society, for much trouble which they have
taken in trying to elucidate this point. Although there is
an Adams Rock at Pitcairn Island, I am satisfied, as the
result of a letter received from Captain Craig, of the U.S.
Hydrographic Office, that the Bank is identical with the
“Victoria Bank” (S. of Abrolhos I.) of our own Admiralty
charts. The discovery of this Bank by the U.S.S. “John
Adams” is announced in the ‘ Nautical Magazine,’ 1850,
p. 186, and Captain Craig informs me that the name ‘ John
Adams Bank” is still employed in a publication! of the
“ Service Hydrographique de la Marine” at Paris.

The species appears to be a well-marked one, the connection
of the lateral walls of the median process with the sides of the
zocecia (fig. 6), and the consequent formation of two distinct
“opesiules””? on each side, being particularly noteworthy.
The species has a robust appearance. The epitheca and the
opercula are thick and strong, and the calcareous parts are
no less strongly developed.

The edge is but slightly raised, and is separated by a slight
groove from the post-oral shelf. This is massive, deep, and
coarsely tubercular, being strongly developed even proximally,
where the shelf is narrow in several of the other species.
The oral shelf is narrow and smooth. The condyles are

' «Instructions Nautiques .. . Brésil,? by Mochez and Roquemaurel,
1890.

256 SIDNEY F. HARMER.

strong, and ankylose with the distal margin of the median
process, thereby forming an unusually massive support for
the base of the operculum. ‘he oral arch is well raised.
The cryptocyst is sharply separated from the post-oral shelf,
and is slightly tubercular. The pores are small, and do not
usually occur on the part of the cryptocyst which descends
into the median process, being here obliterated by a tuber-
cular calcareous thickening. ‘The tube is complete, though
the only part of its wall which is well developed is the upper
part. The lateral parts of the wall are very low, while
basally the tube is a mere perforation in the oblique crypto-
cyst. The epithecal sclerites are minute and widely separated
from the operculum. They are probably small, because the
epitheca generally is so thick that it is strong enough to
withstand the pull of the depressor muscles without differen-
tiating special sclerites. In the dry condition a somewhat
complicated appearance of sclerites seems to be present in
the epitheca. As these cannot be seen in Canada balsam
preparations, I have convinced myself that they are due to
the crumpling of the epitheca during drying.

I have found only one form of operculum (fig. 18); the
similarity of these to the B opercula of S. sulcata (and
particularly to that of specimen f) induces me to regard them
as belonging to the B type, in which case we have here the
unique peculiarity of a species in which the B opercula alone
are known. In the absence of any certain evidence as to the
meaning of the dimorphism of Steganoporella, it is not
impossible that some species consist of two kinds of colonies,
in one of which the a form of zocecium preponderates or is
alone present, and in the other the p form. If this were the
case it would not be inconceivable that S. connexa might
be the second form of 8. simplex or 8. auriculata, for
instance. The supposed species are not unlike in some
respects; but I do not think that they are really related in
this way.

The chitin of the opercula, and in particular that of the
sclerites, is thick and dark-coloured. ‘The occlusor tubercle

A REVISION OF THE GENUS STEGANOPORELLA. 257

is situated rather more distally than in most species. The
submarginal teeth are strong, and are borne on a distinct
sclerite, which commences near the base of the operculum.
Their number varies from about thirteen to about twenty,
the proximal ones being minute. Highteen may be regarded
as the average number. The operculum is always broader
than long, though the disproportion between the two measure-
ments is sometimes a good deal less than in fig. 18. The size
varies as much as the shape, but without altering the general
characters of the operculum. ‘The diameter varies from 450
to 700 pu, that of the specimen figured being 570 yu, which is
almost exactly the average of the specimens measured.

(i) B Opercula apparently wanting. a Opercula
with four teeth on the main sclerite, the
proximal pair being derived from the occlusor
tubercle. .

6. S. auriculata, n. sp. Figs. 8, 24.

Cryptocyst inserted near the junction of the distal and
basal walls, usually joining the distal wall, but sometimes
joining the basal wall; not angulated at the commencement
of its descending portion. Median process with enormous
auriculate lateral wings; uniting distally with the large con-
dyles, which project into the subopercular space as con-
spicuous points. A curved “opesiule,” for the passage of
tendons, is thus formed on each side. The opening of the
tube is nearly vertical, and is invisible from above. Cavity
of median process very broad above, diminishing almost to a
point below. 8B zocecia not found. a opercula with four
enormous teeth on the main sclerite ; a broad and excessively
strong transverse, sub-basal sclerite connecting the bases of
the two proximal teeth.

Madagascar : T’. W. Waters, Esq. (B. M., 84.11.18, 1).

The specimens of this species are—(a) an imperfect colony
on a red seaweed, Hemescharan in character, forming an ex-
panding flattened collar which encircles the narrow stem of

258 SIDNEY F, HARMER.

the seaweed, and measures about 20 mm. in length by about
6 mm.; the orifices are on the outer side of the collar; (5)
slides which have been prepared from this specimen.

This species cannot well be confused with any other ; the
great auriculate median process (fig. 8), uniting distally with
the condyles, the four strong opercular teeth (fig. 24), and in
particular the immense sub-basal sclerite, make this species
one of the most distinct which I have had the opportunity of
examining.

The edge is hardly raised. The post-oral shelf is deep,
massive, and tubercular, being well developed even proxi-
mally. The oral shelf is narrow and smooth. The condyles
are long, and meet the distal border of the median process,
projecting as well-defined points into the distal chamber of
the zocecium. ‘The oral arch is thick and not much raised.
The cryptocyst is sharply separated from the post-oral shelf,
and its horizontal portion is much depressed, tubercular, and
(when old) with small pores. It slopes very steeply but
without angulation into the cavity of the median process.
he tube is incomplete distally, its low lateral walls joining
the distal (or basal) wall, by which the tube is completed.
The cryptocystal boundary of the lateral recesses is nearly
vertical. The back is tubercular, and is too thick to be trans-
parent. It is covered by a thick epitheca, which is con-
tinuous with a chitinous layer that separates the vertical
calcareous walls of adjacent zocecia, and is itself continued
into the epitheca of the free surface. The uncalcified part
of the vertical wall being relatively thick, some of the zoccia
of an incinerated specimen appear completely separated from
one another laterally, each having its own wall. The epitheca
is thin and the epithecal sclerites are long, and start from
the operculum. B zocecia have not been observed. The a
opercula (fig. 24) are very strong, broader than long, with
four great teeth on the main sclerite and an enormous sub-
basal transverse sclerite between the two proximal teeth.
When seen from above, in a dry preparation, the opercula
show a specially dark line at g, and another, not quite so

A REVISION OF THE GENUS STEGANOPORELLA,. 259

dark, indicating the base of the tooth-bearing or main
sclerite. Both these dark lines are in the plane of the outer
surface of the operculum, and g is accordingly the origin of
the sub-basal sclerite (seen from the inside in fig. 24). The
real form of the sclerites can be well made out in these large
and thick opercula in dry specimens seen from the inner side.
The edge h of the sub-basal sclerite stands up above the
surface in this view, the sclerite sloping from its origin g
obliquely to its most prominent part h. This is continued
into the projecting proximal spout 7, in which each of the
halves of the main sclerite ends. The proximal tooth of
each side is connected by a buttress with the distal end of
the sub-basal sclerite. ‘The main sclerite is very convex on
the proximal side of the proximal tooth, sloping from here to
the base of the operculum, where the main sclerite runs into
the general level of the operculum. In optical sections of
Canada balsam preparations the proximal part of the main
sclerite appears as two parallel bars, the most prominent
part being thinner than its sides.

The edge h of the operculum rests on the distal border of
the calcareous median process, the projecting points of the
condyles fitting into the angles where / turns proximally.

The opercula do not vary much. Their average diameter
is about 550 w, the size of the specimen figured.

7. S. neozelanica, Busk.

Synonyms of Typical or Vincularian Form. Figs. 4, 25, 30.

Vincularia neozelanica, Busk, ‘Quart.Journ. Micr.
Sei.’ (N. S.), 1, 1861, p. 155, pl. xxxiv, figs. 5, 5a;
and ‘Chall. Rep.,’ pt. xxx, 1884, p. 76; Hutton,
‘Man. New Zealand Mollusca,’ 1880, p. 189.

Steganoporella neozelanica, Hincks, ‘ Ann. Nat.
Hist.’ (5), #571882. p. 119, and’ (6); xi, 1893, p.
175; Waters, ‘Quart. Journ. Geol. Soc.,’ xli,
1885, p. 292, and xliii, 1887, p. 50; ‘Chall. Rep.,’
pt. Ixxix, 1888, p. 14, pl. ii, fig. 32 (or ? var,

260 SIDNEY F. HARMER.

magnifica); Hutton, ‘Trans. Proc. N. Zealand
Inst:,7 xxi, 18905 p: 1104:

Synonyms of Hncrusting Form (var. magnifica, Busk,
MS.) (figs. 5, 26).

Membranipora magnilabris, Hutton, 1. cit., 1880,
pe t90:
Steganoporella neozelanica, Hincks, ‘ Ann. Nat.
Hist.’ (5), 1x, 1882, p. 119; -Waters, “Quart.
Journ. Geol. Soc., xlii, 1887, p. 50.
S. magnilabris, Busk, ‘Challenger Rep.,’ pt. xxx,
1884, p. 75 (Tongatabu); Hutton, ‘Trans. Proc.
N. Zealand Institute,’ xxii, 1890, p. 105.
Cryptocyst inserted into the basal wall, angulated and
slightly thickened at the commencement of its descending
portion. Median process with a spreading border, its cavity
very deep, vertical, narrow above, but expanding transversely
until it equals the diameter of the tube at its junction with
the latter. Opening of the tube vertical, usually surrounded
by the descending part of the cryptocyst, but sometimes
completed by the basal wall. 8B zocecia not found. a opercula
with four strong teeth on the main sclerite, and with a more
or less complicated system of additional sclerites.

Vincularian Form.

(a) New Zealand, Mr. Busk (C. M.).

(b) New Zealand (Wanganui, Napier), Miss EH. C.
Jelly (C. M., 24.5.95).

(c) New Zealand (Hawke’s Bay), Hincks Coll. (C. M.,
13.5.99).

Var. magnifica.

(a) New Zealand (Napier, Foveaux Straits, Stewart
Island), Miss H. C. Jelly (C. M., 24.5.95).

(b) Tongatabu, Sir E. Home, Busk Collection (B. M.,
99,7.1, 400, 401),

A REVISION OF THE GENUS STEGANOPORELLA. 261

I have found great difficulty in deciding whether the
encrusting species of Steganoporella which is common in
New Zealand deserves to be ranked as a species. For the
present I shall describe it as var. magnifica, a name which
I have found on two slides! from Tongatabu, in the Busk
collection at the British Museum.

In the diagnosis I have chosen those characters which
are common to the two forms. I now give a description of
the typical form, indicating later the special characteristics
of var. magnifica.

The Vincularian form grows from a mass of stout, chitin-
ous rootlets, which give off a number of cylindrical, unjointed
shoots, the largest of which, in the Cambridge collection, is
36 mm. long. The zoecia open all round these shoots. They
are arranged in the usual longitudinal rows characteristic of
Steganoporella, but their basal wall tends to be reduced
to a longitudinal line occupying the axis of the shoot. If
this result were actually arrived at the zocecia would be
three-sided prisms, all reaching the centre. ‘here is, how-
ever, a considerable amount of irregularity in this respect, the
arrangement being indicated by fig. 30, which represents
part of a transverse section of the cylindrical shoot.

The mode of growth of these groups of cylindrical stems,
united by a common mass of roots, does not seem to have
been described. Although I have not quite complete proof
as to the details, I have very little doubt as to what really
happens. The cylindrical stems are unbranched, except for
the fact that at their base, just where they join the mass of
rootlets, many of them give off a small offset. This offset
may reach a length of asmuch as about 5mm. At this stage
the connection of the offset with the parent stem is becoming
weak, no doubt by an absorption of some of the calcareous
matter. The offset is already directly connected with the tangle
of rootlets, and is ready to break off as an independent stem.

This offers an interesting parallel to the mode of jointing

1 A third slide, of uncertain locality, labelled by Mr. Busk as S, magni-
fica, belongs to S. magnilabris,

262 SIDNEY F. HARMER.

which has been described by Lomas! in Cellaria fistulosa.
The young branches in this species, as in Crisia and doubt-
less in other jointed Polyzoa, arise as outgrowths of the older
branches, formed of zocecia which are at first rigidly connected
with their parents. By the “ breaking” (no doubt accom-
panied by some absorption of the calcareous walls) of the
base of these zocecia a joint is formed, the broken ring dis-
playing chitinous tubes beneath, which connect the young
branch with the older one.

The rootlets of S. neozelanica are probably comparable
with the connecting tubes of other jointed Polyzoa, although
they are continuous with the external epitheca. Assuming
the correctness of Nitsche’s account already referred to,” the
connecting tubes of Cellaria may be regarded as formed
from the chitin which is left on the inner side of the calcareous
wall by the calcification of the middle lamella only of the
original chitinous ectocyst. S. neozelanica is thus to be
regarded as a jointed species; and if what has been said
above with regard to the arrangement of the zocecia is correct,
the group of tubes may be derived from an originally Escharan
(bilaminar) colony, with narrow branches given off in a pal-
mate manner, a longitudinal division of the colony taking
place with the formation of each fresh branch.

The edge of the zocecia is very slightly raised, and slopes
continuously into the post-oral shelf. This is finely tuber-
cular, and often slopes continuously into the cryptocyst. The
oral shelf is represented by a mere line. ‘The condyles are
small. The oral arch is thick, and practically not raised
above the level of the epitheca. The cryptocyst is thick and
tubercular, not much thickened at the commenceinent of its
descent, which is angulated and at right angles to the proximal
portion. ‘The cavity of the median process is very deep, its
upper opening usually in the form of a longitudinal shit, the
cavity widening regularly as it descends until it reaches the
same transverse diameter as the tube where it joins this

1 «Proc. Liverpool Biol. Soc.,’ iii, 1889, p. 219,
2 See p. 227.

A REVISION OF THE GENUS STEGANOPORELLA. 263

structure. The periphery of the median process is everted.
The cavity of the process, when seen from the distal side
(fig. 30), is thus like a flask with a narrow neck and a spread-
ing mouth. ‘he tube (¢.) is little more than a circular open-
ing in the vertical cryptocyst. The opening is large, and
commonly of the same width as the zocecium itself at this
level. While it is usually separated from the deepest point
of the zocecium by a part of the cryptocyst, its lateral
boundaries are formed by the lateral walls of the zocecium,
an arrangement peculiar to this form. In some cases the
tube may, however, occupy the entire deeper part of the
zocecium. Hach lateral wing of the median process commonly
comes into contact with a tooth given off from the lateral part
of the zocecium, thus limiting a complete “ opesiule” (fig. 4).
The lateral recesses (fig. 50, 7.7.) have an unusual form.
They are completely vertical, and, sharing in the great depth
of the median process, they take the form of cavities which
appear triangular when seen from the distal side, their apices
being directed towards the axis of the branch.

The epithecal sclerites (fig. 4, e.s.) are rather short, and
do not quite reach the base of the operculum. No B zocecia
have been found. ‘he a opercula (fig. 25) have four well-
developed teeth on the main sclerite, which is massive, its
proximal ends projecting considerably as rounded, sometimes
trifoliate lobes. ‘The area included within the semicircular
main sclerite is occupied by a complicated system of smaller
secondary sclerites. A varying number of longitudinal bars,
usually converging towards the middle line, and uniting with
one another in various ways, start from a basal sclerite, and
are united by a more or less transverse sclerite, which joins
the main sclerite at its two ends, and may give off distally
irregular longitudinal sclerites, some of which may join the
main sclerite. ‘his set of sclerites is highly variable. Hach
is a girder-like thickening, like the other sclerites of the
operculum.

The size of the opercula is very constant, averaging about
450. That of the specimen drawn is 500 nu,

VoL, 43, PART 2,—NEW SERIES, Ly

264 SIDNEY F. HARMER,

S. neozelanica, Busk, var. magutifica, Busk (MS.).
Figs. 5, 26.

The habit is encrusting, this variety covering large areas
and appearing to have a special fondness for oyster shells.
There are no rootlets. The basal wall is equal in size to the
upper wall, as in other encrusting species. The edge is more
distinct from the post-oral shelf, and the latter from the
cryptocyst, than in the Vincularian form. ‘The oral shelf, as
in the latter, is represented by a mere line. The condyles are
not well marked. The oral arch is thick and more raised than
in the Vincularian form. The cryptocyst is thick, proximally
horizontal and tubercular, not much depressed, and it is
slightly thickened at the angle formed by the commencement
of its descent, which is vertical, the insertion being into the
basal wall. The pores are rather small. The opening of the
cavity of the median process is rounded or subtriangular,
not slit-like as in the Vincularian form, with which, however,
this variety agrees in the deep flask-shaped cavity of the
median process. The expanded mouth of the median process
does not meet the side of the zocecium, which has no tooth in
this position. The lateral recesses are bounded proximally
by a vertical portion of the cryptocyst. The tube is little
more than a circular perforation in the cryptocyst, being well
separated both from the basal and the lateral walls, and so
differing from that of the Vincularian form. As the opening
of the tube does not nearly reach the lateral walls of the
zocecium, the proximal boundary of the lateral recess is not
cut off by the tube from the deeper part of the ecryptocyst.
The basal wall shows the insertion of the cryptocyst, which
marks off a distal chamber whose base is more or less semi-
circular or biconvex, the diameter of the semicircle (if of this
form) being constituted by the base of the distal wall of the
zocecium.

The epithecal sclerites are subparallel, nearly straight,
rather short, and do not reach the operculum.

‘he opercula (fig. 26) resemble those of the Vincularian

A REVISION OF THE GENUS STEGANOPORELLA, 260
form, having four well-developed teeth and a series of
secondary sclerites. ‘he young operculum shows the main
sclerite only. The smaller sclerites consist of a_ basal
sclerite, an irregularly arch-shaped sclerite which is roughly
concentric with the main sclerite, and additional sclerites
starting from these two. One of these may start from the
arch-shaped sclerite opposite each of the four teeth, and
unite with the main sclerite in such a way as to pass beneath
its projecting edge and to form a buttress-like support for
the tooth. Although the pattern of the opercula is very
variable even in the same colony, there is usually a recognis-
able difference between these opercula and those of the
Vincularian form, in which there is commonly a more or less
transverse secondary sclerite and a system of subparallel
longitudinal sclerites between this and the basal sclerite.
The proximal projections of the main sclerite of var.
magnifica are usually hook-shaped on their outer side, but
they commonly have a lobe on their inner side as well. The
most striking difference between this and the Vincularian
form is, however, the existence of numerous fine denticula-
tions on the outer side of the base of the main sclerite.
These appear to be constant in this variety, but I have seen
no trace of them in the typical 8S. neozelanica.

The size of the opercula is rather uniform. The average
diameter is about 550 pe.

I am very doubtful whether this form should be regarded
as a distinct species, in which case Busk’s MS. name
magnifica, affixed to the specimens fron Tongatabu, might
be regarded as the specific name. he difference in habit
between the Vincularian and the encrusting forms seems to
be constant. Some of the other differences, such as the
form of the basal wall, the boundaries of the tube, and the
shape of the lateral recesses, are directly connected with the
habit. Others, and in particular the denticulation of the
opercula, the pattern of the secondary sclerites, and the shape
of the median process, are not obviously connected with the
habit.

266 SIDNEY F. HARMER.

S. neozelanica has formed the subject of several de-
scriptions. Hincks (1882) regards the encrusting and Vin-
cularian forms as varieties of one species, and shows that the
Vincularian habit cannot be regarded as a generic character.
Waters (1885) states, if I understand him correctly, that in
S. magnilabris the bifurcation of a longitudinal row of
zocecia takes place on the distal side of a B zocecium: since
the Vincularian S. neozelanica grows in a form in which
there is no frequent multiplication of the rows, no B zocecia
are found. I do not think that this is an adequate explana-
tion of the absence of the B zocecia. It has been shown
above that they may be absent or excessively rare in en-
crusting species. It is, moreover, not the case that bifur-
cation of a row takes place only on the distal side of a B
zocecium ; and these are not necessarily larger than the a
zocecia which are their neighbours. Waters in this paper
calls attention to the four teeth and the secondary sclerites
of the operculum of S. neozelanica. In 1887 Waters
uses the term “shelf” in describing Steganoporella.
Although he refers merely to what I have called the “ oral
shelf,” I have found it convenient to extend the term to the
thickened borders of the lateral and proximal walls. The
diagrammatic longitudinal section given by Waters (1888) is
not quite satisfactory, inasmuch as the epitheca is omitted,
and the base of the operculum appears to be continuous with
the median process.

(111) B Opercula with a A-shaped main sclerite. Oral shelf
well-developed, in B zocecia at least.

This group consists of species in which, for the first time
(with the exception of S. connexa in the previous groups),
the B zocecia are ordinarily so common that no difficulty is
experienced in finding them in even small fragments. Their
A-shaped main sclerite gives them a character which is quite
distinct from that of the first group of species. The two
halves converge distally, and after a longer or shorter parallel
course diverge outwards in a curved line, to become continu-

A REVISION OF THE GENUS STEGANOPORELLA. 267

ous with the submarginal or tooth-bearing sclerite. In the
distal part of their course the space between the halves of
the main sclerite is floored by a transparent layer of chitin
which has a sharp arch-like edge proximally (figs. 36, 41).
This space contains living tissue, as is shown by its behaviour
to staining reagents. It appears as a loop-shaped area, often
dilated distally, between the two parallel halves of the distal
region of the main sclerite. Hach of these halves becomes
more and more prominent as it passes proximally, being pro-
duced on the proximal side of the occlusor tubercle into a
strong projection, which stands out to a considerable distance
beneath the upper surface of the operculum. ‘The space
between this projecting edge and the more externally placed
base-line of the sclerite (on the proximal side of the occlusor
tubercle) often appears as a fenestra (cf. fig. 36), but is
more probably due to the fact that a thin vertical lamella of
chitin connects a broad base with a broad edge. There is
always a strong basal sclerite (b) ; and an oblique sclerite (0)
runs from the proximal projection outwards as an additional
buttress to this part of the operculum.

The projecting ends are for the insertion of a strong
muscle, as I hope to show on a future occasion. ‘This type of
operculum differs widely from the B opercula of the first
group of species, and I can hardly doubt that it is of great
functional importance to the colony. The possession of this
highly characteristic operculum may be regarded as indicat-
ing the relationship of the species to other species similarly
provided. The submarginal teeth of these B opercula are
nearly always strong.

The median process of the B zocecia is usually obviously
narrower than that of the a zocecia. This is probably due to
the larger muscles of the B form, necessitating a wider
lateral recess, aud a consequent compression of the median
process.

Several very distinct types of a opercula occur in this
group of species. I begin with the species in which these
opercula are still of the “ undifferentiated” type.

268 SIDNEY F. HARMER.

8. &. haddon;'n. sp. “Wirs sli se, "a0.

S. magnilabris, MacGill., “Mon. Tert. Pol. Victoria,”
‘Trans. Roy. Soc. Vict.,’ iv, 1895, p. 53, pl. vi, figs. 14—16.

B zocecia about twice as large as the A zocecia. Crypto-
cyst descending gradually and slightly, without angulation,
joining the distal wall rather high up. Median process
wide,’ its distal border usually without poimted angles, its
cavity not very deep, the roof of the tube forming its distal
boundary rather than its floor. Opening of tube oblique,
clearly visible from above; that of 4 zocecia usually com-
pleted by the distal wall, that of B zocecia entirely sur-
rounded by the cryptocyst. 8B zocecia with an enormous oral
shelf ; their opercula usually longer than broad, the halves of
the main sclerite being close together and parallel for a con-
siderable distance distally, so that the sclerite is A-shaped
rather than A-shaped; submarginal teeth fine, recurved,
limited to the distal half of the operculum. a zocecia small ;
ral shelf evanescent or narrow; their opercula undiffer-
ntiated.

(a) Torres Straits, Haddon Coll. (C. M., 24.2.98).

(b) Port Darwin, N.W. Australia, H.M.S. “ Alert” (B. M.
82.2.23, 512).

(c) Australia, Dr. J. H. Gray (B. M.).

(d) Australia (B. M.).

(e) Australia (B. M., 62.6.5, 18).

jf) Australa, Busk Coll. (B. M., 62.6.5, 18) ; marked by
Mr. Busk “8S. magnilabris, var.”

[Various localities, Victoria (Tertiary), MacGillivray. |

MacGillivray, who describes this form as a Tertiary fossil,
appears to be the only author who has noticed it. He
describes the B zocecia as having a shelf, which is seen from
his fig. 14 a to be large, and to form a distinct ogee arch.
The a zocecia have no shelf, or in some specimens a narrow
shelf. One specimen had a conical process on the back of

1 Not so wide in B zoecia, see p. 267.

A REVISION OF THE GENUS STEGANOPORELLA. 269

the zocwcium (fig. 14 b), “ probably a modified radical tube.”
The opening of the tube is well visible from above, being
shown in both A and B zoccia. These characters clearly
point to the species being identical with 8S. haddoni. Mac-
Gillivray suggests that his fig. 15 may be 8. neozelanica.
The dimorphism of the zoccia, the large oral shelf of 8, and
the obliquity of the opening of the tube make that determi-
nation improbable.

I name this species in honour of my friend Dr. A. C.
Haddon, whose collection from ‘Torres Straits formed the
starting-point of the present paper.

This species is probably of Hemescharan habit ; the largest
piece (c) measuring 386 X 33 mm. There is very little varia-
tion in the specimens I have examined. The zocecia are
commonly arranged with great regularity, and in some speci-
mens considerable parts of the colony are found in which
the arrangement is—

A
5 eae a eae
A
A
ee eda 3 ed eee ce
A

In other cases the B zocecia may be less numerous, a
zocecium of this form being followed in the same line by
three, four, or even five A zocecia. The back is very charac-
teristic. It of course shows no trace of the insertion of the
cryptocyst. That of each zocecium is slightly convex, with

270 SIDNEY F. HARMER.

intervening slight depressions between the longitudinal rows.
‘The back bears a moderate number of short cylindroid
calcareous papille. ‘These are much more definite structures
than the irregular outgrowths found on the back of many
encrusting species which grow on irregular surfaces, Some
of them have a rounded termination, while others are trun-
cate; this truncation suggests that the papillae: may be con-
tinued into chitinous rootlets, and one or two of the (dry)
specimens appear to show remains of these rootlets, which
are, however, much more delicate than those of the typical
form of 8S. neozelanica.

The edge is thin and much raised, passing gradually into
the post-oral shelf, which is usually very narrow, especially
proximally, though of considerable depth, and commonly
slopes gradually into the cryptocyst. ‘The oral shelf is
narrow or vestigial in a zocecia, but of great horizontal
extent in the B forms, where it is finely tuberculated, flat or
concave above, its free edge somewhat upwardly directed at
two distal points which more or less distinctly give it the
form of a trifoliate or ogee arch. The space above the shelf
is, however, to a considerable extent due to the fact that this
part of the zocecium overlaps the next zocecium on its distal
side, the curved transverse line (fig. lla) being the upper
end of the wall of separation between the cavity of the B
zocecium and that of its next neighbour distally. The oral
arch is not much raised; it is rounded in A zocecia, quad-
rangular (with rounded distal corners) and parallel-sided in B.
The cryptocyst is thin, with large pores; it slopes gradually
and gently into the median process and the lateral recesses,
its slope often beginning from its proximal border, so that it
is hardly possible to speak of a horizontal portion as in most
of the species. From the cryptocyst which enters the median
process the upper wall of the tube usually rises without any
angulation. ‘lhe descending part of the cryptocyst is, owing
to its slight descent, much more easily seen than in any of
the preceding species, and it entirely hides the basal wall of
the zocecium, except by deep focussing through the opening

A REVISION OF THE GENUS STEGANOPORELLA. 271

of the tube. ‘lhe median process in 4 is broader than long ;
in B longer than broad. Its border is not much everted, nor
with pointed distal corners; and its cavity is shallow. The
tube in B zocecia is usually surrounded by the cryptocyst, its
low lateral walls sloping down distally, so that the distal
border of the tube has no raised wall. In a zoccia the tube
is incomplete distally, though its wall may be more developed
than in fig. 11. The lateral recesses commonly have a par-
tial roof, formed by a thin upstanding calcareous lamella
continuous with the lateral wing of the median process, from
which it passes proximally and then forwards on the outer
side of the lateral recess.

The epithecal sclerites are small and inconspicuous, sepa-
rated by a wide interval from the operculum. The B opercula
(fig. 38) are quite distinctive. They are of great size in pro-
portion to the a opercula ; they are more or less quadrangular,
with rounded distal corners, and are usually longer than
broad. ‘There are nineteen to twenty-four fine, long, sharp,
recurved teeth, borne on the distal half only of a thin sub-
marginal sclerite. The distal part of the A-shaped main
sclerite is formed of two long, prominent, parallel bars, the
loop between which is not much dilated distally. The chi-
tinous floor of this space ends at the proximal end of the
parallel portion, the space on the proximal side of its edge
between the diverging parts of the sclerite being triangular.
The occlusor tubercles are small. The proximal projections
are very prominent, and are somewhat everted with a con-
cavity on their inner sides. ‘The basal sclerite is strong, and
the oblique sclerite well marked.

The A opercula (fig. 39) are of the ‘undifferentiated ”
type, and closely resemble those of some of the preceding
species.

The diameter of the a opercula in the type specimen (a) is
about 490, and that of the B forms about 520. The a
opercula of specimen e average about 350 , and the B forms
about 450

972 SIDNEY F. HARMER.

9. 8S. buskii,n. sp. Figs. 13, 33—35.

Membranipora magnilabris (part), Busk, ‘ Brit. Mus.
Cat.,’ 11, 1854, p. 62.

B zocecia much less than twice as large as A zocecia.
Cryptocyst descending gradually and slightly, without angu-
lation, joining the distal wall at a high level. Median process
wide and short in A zocecia, much narrower in B, its distal
border usually produced into projecting points; its cavity
shallow, limited beneath by the descending cryptocyst, and
distally by the roof of the tube. Opening of tube nearly
horizontal, entirely visible from above, completed by the
distal wall in both a and s. Oral shelf not much more de-
veloped in B than in A. B opercula with A-shaped main
sclerite, with numerous small submarginal teeth, sometimes
vestigial, the series beginning near the proximal end of the
operculum. Parallel portions of the halves of the main
sclerite of moderate length, the arch formed by the proximal
parts wide and evenly rounded. a opercula undifferentiated.

(a) Port Elizabeth, Cape Colony, Miss EH. C. Jelly
(C. M., 24.5.95).

(b) Algoa Bay (three slides), Busk Coll. (B. M., 99.7.1,
404—406).

(c) Shahr, South Arabia (B. M., 94.6.18, 7a).

(d) Reef in Talisse Island, North Celebes, Professor
S. J. Hickson (C. M.).

(e) Thursday Island, Torres Straits, four fathoms,
H.M.S. “ Alert ” (B. M., 82.2.28, 512).

(f) Australia (B. M., 50.8.28, 9).

This species is named in honour of Mr. Busk, to whom the
first description of a species of Steganoporella is due.
The examination of the three slides (b) from Mr. Busk’s col-
lection in the possession of the British Museum shows that
the original description of 8. magnilabris (but not the
figure) was based on two distinct species.

A REVISION OF THE GENUS STEGANOPORELLA. 2793

The characters of this species are sufficiently well marked,
though it is distinguished by a considerable amount of varia-
bility. It is encrusting or Hscharan, possibly sometimes
Hemescharan. The slight descent of the cryptocyst is shared
only by 8. haddoni, and to a less extent by S. truncata.
The combination of a B operculum thickened in a A-like
manner with an “ undifferentiated” a operculum is only found
in 8. haddoni of the species at present known; and this
differs from 8. buskii in the great relative size of the B
zocecia, and their enormous oral shelf, besides many details
in the B opercula, and in particular the restriction of the
teeth to the distal half.

The edge is thin and rather distinctly separated from the
post-oral shelf, which is narrow, small proximally, and is
covered by sharp tuberculations which may give it a denti-
culate appearance. The oral shelf is not much more de-
veloped in 8 than in 4. The condyles are conspicuous in B,
smaller in a. The oral arch is well raised; a transversely
elongated fenestra (or semi-transparent part of the distal cal-
careous wall) within the oral arch in 4 and B is conspicuous
in some specimens (a), and indicates the extent to which the
zocecium overlaps the next in the series. The cryptocyst is
sharply separated from the post-oral shelf; it is thin, with
conspicuously large pores, and slopes gently, without any
angulation, into the cavity of the median process and the
floor of the lateral recesses. Some specimens show the
cryptocyst in a very simple condition. Its descent in (c) is
unusually slight, and there is nothing to distinguish the
commencement of the floor of the lateral recesses except the
cessation of the pores of the horizontal part. The median
process, although of the typical form, is small and has an un-
usually shallow cavity, whose floor is nearly in the same plane
as that of the lateral recesses. The margins of the median
process are not continued to form a proximal boundary to
the lateral recesses. The opening of the tube is entirely
visible from above; it is nearly circular, completed as usual
by the distal wall, its lateral walls being so low as to appear

274 SIDNEY F. HARMER.

like a narrow border on each side of the opening. The a
opercula of this specimen are perfectly typical, and two B
opercula found, so far as can be seen in the dry preparation,
are in no way remarkable. ‘lhe specimen has much less than
the normal proportion of B zocecia.

‘he South African specimens (a, b) show the simple cha-
racter of the cryptocyst in a somewhat less marked way.
The sides of the median process are usually continued
obliquely across the proximal border of the lateral recesses
as far as the sides of the zocecia, though fading away to a
mere line before they reach this part. The lateral recesses
are thus sharply outlined; their floor is at a hardly deeper
level than that of the cavity of the median process, and its
plane is somewhat different, since it slopes basalwards as it
passes from the tube to the side of the zocecium. Ina few
cases a distinct curved line, with its concavity towards the
median process, runs transversely across the cryptocyst from
one lateral recess to the other. The part of the cryptocyst on
the distal side of this line is thin-walled, transparent, and
usually without pores. I can offer no suggestion with regard
to this appearance, which may have bearings on the function
of the median process. The difference in the size of the
lateral recesses in A and B is striking, indicating a difference
in the development of their muscular system. The opening
of the tube is usually narrower distally ; its sides meet the
distal wall in a highly characteristic way; they are alike in
both a and B, and the first impression produced by examining
them without sufficient focussing is that of a line on each side
of the opening fixed to the distal wall by an expanded foot.
The lateral wall of the tube is, in fact, somewhat expanded
aud thickened where it joins the distal wall. The tentacle-
sheath, in its passage through the tube, must lie in contact
with the distal wall, instead of being separated from it, as in
some other species, by a part of the cryptocyst. The basal
wall of the zocecium is not visible from above, except by deep
focussing through the opening of the tube. The back shows
merely the origin of the four vertical walls. ‘The proximal

A REVISION OF THE GENUS STEGANOPORELLA. 275

or distal wall, on the contrary, shows two curved obliquely
horizontal lines (fig. 33) corresponding with the insertion of
the floors of the two lateral recesses.

The epithecal sclerites are short, nearly straight, distant
from one another, and not nearly reaching the operculum.

The 8 opercula (fig. 34) have about thirty submarginal
teeth. The series begins not far from the base of the oper-
culum, and the teeth are short and small, or even vestigial.
The submarginal sclerite is not sharply defined, and the
parallel part of the main sclerite projects but little above the
general level of the operculum. On the proximal region of
this part the halves of the main sclerite diverge so as to form
a bold arch, which is completed distally by the edge of the
chitinous portion which connects the two parallel parts of
the bar. The projecting proximal ends of the sclerite are
less everted than those of 8. haddoni. ‘The basal and
oblique sclerites are well developed. The a opercula (fig. 35)
are of the ‘‘ undifferentiated ” type.

This species is a somewhat variable one. The Port Eliza-
beth specimens (a) are bilaminar, while that from North
Celebes (d) is encrusting. The zocecia of the South African
forms (a, b) are larger than those from other localities, and
their opercula are more robust. There is considerable varia-
tion in the form of the opercula. The B form shown in fig. 54
may be regarded as a long one, as it is considerably longer
than broad ; others, even of the same colony, being relatively
much shorter and even a good deal broader than long, In
these cases the parallel portion of the main sclerite is shorter
than in fig. 34. The specimen (e) from Torres Straits has
conspicuously short and broad B opercula.

The diameter of the opercula (in pu) is as follows:

B. A.
Specimen a (Port Elizabeth) 500—590 . 420—560
- c (South Arabia). — . 3840—500

d (North Celebes) . 560 . 450—560
f (Australia) : 500 . 370—450

3)

)

276 SIDNEY F. HARMER.

10. S. truncata, n.sp. Figs. 9, 36, 37.

S. magnilabris, Busk, ‘Challenger Report,’ pt. xxx,
1884, p. 75 (Port Dalrymple) ; MacGillivray, in
McCoy’s ‘ Prodr. Zool. Vict.,’ vol. i, decade 6,
1881, p. 43, pl. Ix, fig. 1; and ‘Trans. Roy. Soc.
Victoria,’ xxii, 1887, p. 208.

B zocecia hardly larger than a zocecia. Cryptocyst descend-
ing rather steeply, without angulation, to join the distal wall
at or below half its height. Median process well developed,
usually with rounded distal angles, and with deep cavity into
which the cryptocyst descends steeply, the roof of the tube
being visible in its floor. Opening of tube oblique, entirely
visible from above, completed by the distal wall, or complete
and separated by a narrow portion of the cryptocyst from the
distal wali. Oral shelf well developed in both a and B, not
tubercular. Oral arch of B semicircular, of a truncate, and
usually slightly concave distally. B-opercula very strong,
with A-shaped main sclerite, and with about twenty sub-
marginal teeth, all except a few of the proximal ones being
stout, long, and nearly erect. A opercula transversely oblong,
with rounded corners; a strong tooth on the main sclerite
not far on the distal side of the occlusor tubercle, and a
strong basal sclerite.

(a) Victoria (Port Phillip, etc.), Miss E. C. Jelly (C. M.,
245.95).

(b) Victoria, Hincks Collection (C. M., 13.5.99).

(c) Victoria, Prof. W. Baldwin Spencer (C. M., 1899).

(d) Port Dalrymple, Tasmania, voyage “ Rattlesnake,”
Busk Collection (B. M., 51.9.29, 34).

The name which I suggest for this well-marked species is
in allusion to the truncate form of the A zocecia (fig. 9).
By this character (already noticed by MacGillivray), and the
shape of the opercula with their dark brown sclerites, the
species can be recognised at a glance. The two large teeth
of the a opercula distinguish it at once from any other species

A REVISION OF THE GENUS STEGANOPORELLA. 277

with A-shaped sclerite in the B opercula. The union of the
cryptocyst with the distal wall, and the deep cavity of the
median process, are also important characters.

MacGillivray states that this form is Escharan, Hemes-
charan, or encrusting. He records an Escharan colony which
measured no less than 13 X 9 x 6G inches. Of the material
at my disposal, c and d are mere fragments, a and b are both
bilaminar or Escharan, with anastomosing plates, and have
somewhat the habit of Lepraliafoliacea. At the lines of
union of the plates the two layers of zocecia diverge, so that
hollow cavities originate, lined by the basal walls of the
zocecia. Considerable unilaminar pieces may thus occur at
the nodal lines. The ratio of a to Bis about 4—5:1. No
constant difference in this ratio was noticed in ‘different
parts of the colony, or on its opposite faces.

The edge is thin, a good deal raised, and well separated
from the post-oral shelf. his is slightly tubercular, deep,
and massive, being well developed even proximally. The
oral shelf is about equally developed in a and zB. It has the
form of a perfectly smooth rounded fillet, a well-developed
concave space with smooth floor occurring between it and
the oral arch. ‘The condyles are strong, especially in Bs.
The oral arch is slightly raised; that of B semicircular, of
A with straight parallel sides and a truncate distal border,
which is usually slightly concave distally. Cryptocyst either
sloping gently into the post-oral shelf or sharply separated
from it; its horizontal portion is very small, thick, and with
small pores, whose outer opening may be obviously smaller
than the inner opening. It slopes steeply, but without any
angulation, into the cavity of the median process. The
cryptocyst is usually porous in this region, but an imperfo-
rate part, forming the proximal wall of the cavity, may be
separated from the horizontal part of the cryptocyst by a
curved line, as in 8. buskii. The median process has a deep
cavity, floored by the convex roof of the tube, which may
arise from the cryptocyst at an angle (as in fig. 9), or with
a continuous slope. The borders of the median process are

278 SIDNEY F. HARMER.

usually continued across the proximal edge of the deep lateral
recesses to join the sides of the zocecia, and the lateral re-
cesses may be margined in their proximal half by a thin
upstanding flange of calcareous matter. The lateral walls of
the tube are well developed. In both a and 8 the base of
the tube may, in some cases, be a hole in the descending
cryptocyst, a narrow portion of which intervenes between it
and the distal wall. The walls of the tube may not, how-
ever, grow from the entire margin of this hole, the tube
growing upwards in such a way that its lateral walls unite
with the distal wall of the zocecium, and being thus incom-
plete above. The appearance seen in the A zocecium of fig. 9
is thus produced. The basal wall of the zocecium is, of
course, invisible from above.

The epithecal sclerites are long and gently curved, reaching
the base of the operculum, usually more distant from one
another in a than in sp. The B opercula (fig. 36) are re-
markably strong, with coarse, sharply pointed, nearly erect
teeth, which are so strong that their bases can be clearly
seen from above through the dry operculum. The longest
teeth may reach 65 uw in length. The submarginal sclerite
is strong. The halves of the main sclerite are widely
separated distally, enclosing a space which is dilated dis-
tally, the edge of its chitinous floor forming a somewhat
pointed arch with the proximal part of the main sclerite.
The two bars composing this end proximally in a stout pro-
jection. The occlusor tubercle is very large and strong.
The basal (b) and oblique (0) sclerites are as usual well deve-
loped. The characteristic form of the A opercula (fig. 37)
has already been described ; their most striking characters
are their large size and the development of a strong tooth
just beyond the occlusor tubercle on each side of the main
sclerite, which is far removed from the periphery of the
operculum. The occurrence of a distinct and strong basal
sclerite is an unusual feature in a opercula. Should an
A zocecium give rise to two younger zocecia at its distal end,
its oral arch and its operculum are more or less semicircular.

A REVISION OF THE GENUS STEGANOPORELLA. 279

I have found very little variation in this species, my
specimens of which have, however, come from practically
one locality. ‘The characters of the opercula are remarkably
constant. It need hardly be pointed out that where a zocecium
is restricted in its growth by want of room its operculum
may be abnormally small. Leaving these cases out of account,
the diameter of 4 opercula varies between 490 and 640 n, with
an average of about 525 4; that of B opercula between 500
and 620 uw, with an average of about 550 un.

11. S. magnilabris, Busk. Figs. 10, 31, 44—46.

Membranipora grandis, Busk, ‘ Cat. Mar. Polyzoa
Brit. Mus.,’ i, 1852, p. vi (explanation of pl. Ixv),
pl. lxv, fig. 4.

Membranipora magnilabris, Busk, ibid., ii, 1854,
p- 62 (part), 118, ? Haswell, ‘Proc. Linn. Soc.
N.S. Wales,’ v, 1881, p. 38.

Steginoporella elegans, Smitt, ‘Svenska Ak.
Handl.,’ xi, No. 4, 1873, p. 15, pl. iv, figs. 96—101.

Steganoporella magnilabris, Hincks, ‘ Ann. Nat.
Hist.’ (5), ix, 1882, p. 1238 [Abrolhos I., Singa-
pore], ? pl. v, figs. 8, 8a; Busk, ‘ Challenger
Rep.,’ pt. xxx, 1884, pp. 75, 76 (woodcuts, fig. 4),
ple xxi, figs, 25,20: § Ortmann, “Arch, -£.
Naturg.,’ lvi, 1, 1890, p. 380, pl. ui, fig. 7.

B zocecia considerably larger than the a zocecia. Crypto-
cyst descending at right angles, without or with thickened
angulation, to join the basal wall. Median process usually
with high walls, and often with a somewhat thickened distal
edge supporting the basal sclerite of the operculum ; its
cavity moderately deep (exceptionally shallow or absent), its
floor wide, formed by the convex roof of the tube. Opening
of tube vertical, not or hardly visible from above, complete
basally, or completed by the basal wall of the zocecium, oral
shelf distinct in both a and 8, larger in B, where the cavity
between the shelf and the oral arch is specially large. B

VOL, 45, PART 2,—NEW SERIES, U

280 SIDNEY F. HARMER.

opercula usually elongated, with nearly parallel sides ; the main
sclerite A-shaped; submarginal teeth developed round the
entire free border of the operculum, the proximal ones small
or vestigial, the distal ones long and recurved. A opercula
with numerous submarginal teeth ; arch formed by the main
sclerite usually somewhat pointed.
(a) Abrolhos Islet, coast of Brazil, 20 fathoms, Voy.
“ Beagle,’ Darwin Coll. (B. M., 54.11.15, 222).
(Type-)
(b) Abrolhos Islet, Busk Coll. (B. M., 99.7.1, 403).
(c) Pedro Bank, 40—50 miles 8. of Jamaica, 10—12
fathoms (on coral), J. E. Duerden, Esq. (C. M.,
30.6.99).
(d) St. Vincent, W. I. (B. M., 40.10.28, 18).
(e) Off Honolulu, Challenger Coll., 20—40 fathoms
(B. M.).
(f) Port Molle, Queensland, 12—20 fathoms, H.M.S.
“ Alert” (B..M., 82.2.28, 443).
(g) Tizard Reef, China Sea, 27 fathoms (B. M., 89.8.21,
10).
(h) Singapore, Hincks Coll. (B. M., 99.5.1, 260).
(7) St. 208, Challenger Coll. (Philippine Is.), 17th Jan.,
1875, 18 fathoms (B. M.). j
(j) John Adams’ Bank,' H.M.S. “ Herald,’ Busk
Coll. (B. M., 99.7.1, 407).
(k) ? loc., “On Meandrina,” Busk Coll. (B. M.,
99.7.1, 402).
(1) ? loc., ‘‘Off Brain-stone,’ Hincks Coll. (B. M.,
99.5.1, 262).
[Florida, 15—37 fathoms, Smitt; Japan, slight
depths to 200 fathoms, very common, Ortmann. |
The figure illustrating the original description of this
species was published in the first part of the ‘ British Museum
Catalogue’ (1852), the name Membranipora grandis ap-
pearing in the explanation to the plates. The description
was published in the second part of the Catalogue (1854).
l See p. 254.

A REVISION OF THE GENUS STEGANOPORELLA. 281

As Busk had himself dropped the earlier specific name, and
as later writers have accepted that given in the diagnosis
(1854), I have preferred to retain the familiar name. The
locality “ Algoa Bay,” given by Busk, does not refer to this
species, but to what I have called 8. Buskii (see p. 272).
As the locality ‘‘Abrolhos Islet”’ stands first in the diagnosis,
and as, moreover, the figure refers to the species from that
locality (as may be concluded in particular from the form of
the a opercula and the presence in them of a basal sclerite),
it is clear that Busk’s name should be applied to the S.
American form. In the ‘Challenger Report’ Busk gives
unmistakable figures (p. 76) of the opercula (a and zB) of this
species, describing the two forms of zocecia; and calls atten-
tion to the epithecal sclerites (‘‘furcate spicula”’). The
statement that the epitheca is closely adherent proximally
to the calcareous lamina is not correct; and the generic
diagnosis must be amended by stating that the cryptocyst
may join the distal wall instead of the basal (‘‘ posterior ’’)
wall. It is at present premature to speak of the B zocecia as
the “fertile cells.’ Fig. 2a on pl. xxii of Busk’s Report
is somewhat misleading, inasmuch as the B opercula are
shaded in precisely the same way as the zocecia which have
lost their opercula.

Biflustra crassa, Haswell,! is given by some authors as
a synonym of 8. magnilabris. I do not think there is
sufficient evidence for regarding this species as a Stegano-
porella. Haswell gives Membranipora magnilabris
in his list of species; and although the zoarial character
doubtless guided him in assigning B. crassa to Biflustra,
I think it would be difficult for the same writer to refer two
forms of Steganoporella to different genera on account of
differences in their habit without at least calling attention to
the resemblance of their zocecia.

This widely distributed species occurs in various forms.
Most of those I have seen are encrusting, but (e) is Escharan,
as figured in the ‘ Challenger Report.’ Smitt states that

1 «Proce. Linn. Soc. N.S.W.,’ v, 1881, p. 38, pl. i, fig. 8.

282 SIDNEY F. HARMER,

the species occurs in encrusting, Hemescharan (of “ Sipho-
nella form”’’—not to be confused with Siphonoporella,
Hincks) and Escharan growth, at a depth of 15—37 fathoms
off Florida. If all the specimens which I have referred to
S. magnilabris are correctly placed there, the species must
be regarded as a somewhat variable one. It is the only form
with A-shaped main sclerite in the B opercula in which the
cryptocyst of both a and B zocecia joins the basal wall ata
considerable distance from the distal wall. The large ex-
posure of the basal wall and the invisibility of the opening
of the tube, when seen from above, are characteristic marks
of this species, which is, moreover, peculiar in the possession
of well-developed submarginal teeth in the a opercula.

The following description refers to the type-specimen (fig.
10) :—The edge is thin and sharply separated from the post-
oral shelf. This is but slightly developed, finely tubercular,
and may be vestigial proximally. The oral shelf is moderate in
B, narrower in A, where it is mostly smooth, and may be con-
spicuously denticulate near the base of the oral arch. The
condyles are much larger in B than in a. The oral arch is
much raised ; by the overlapping of the zocecia over their next
neighbours distally there is a large concave space in the
B zocecia, between the oral arch and shelf. The oral arch of
B is much larger than that of a, the shape corresponding
with that of the respective opercula. The cryptocyst is
sharply separated from the post-oral shelf (except, as in
most other species, at the distal corners of its horizontal
portion), descending steeply (without any angulation in the
type-specimen) into the cavity of the median process. This
is wider in a than in B; it is moderately deep, its wide,
rather long floor being constituted by the convex roof of the
tube, whose opening is vertical and invisible from above.
The lateral recesses are commonly very asymmetrical, only
one meeting the basal wall, the floor of the other passing
into the lateral wall of its side. On examining the back of
the specimen this arrangement gives rise to the appearance
of fig. 31. The thick curved line rising from the left lateral

A REVISION OF THE GENUS STEGANOPORELLA. 283

wall is the line of insertion of the cryptocyst, forming the proxi-
mal boundary of the corresponding lateral recess. The thin
line running transversely from this to the opposite lateral wall
may or may not be present. If it is absent, the tube is com-
pleted by the basal wall, and we have here a case precisely
like that of Siphonoporella delicatissima (see p. 282),
where the tube rises asymmetrically from one side of the
base of the zocecium. If the thin line is present the tube
has a completed wall, and is connected with the basal wall
by a thin transverse septum, which is part of the cryptocyst.
If the cryptocyst of both lateral recesses meets the basal
wall two thick curved lines appear.

The asymmetry of 8S. magnilabris, taken in conjunction
with what has been said under S. lateralis, seems to me
to have an important bearing in showing the derivation of
Steganoporella from an asymmetrical ancestor.

The lateral walls of the tube are well developed. The
lateral recesses are often partly roofed in by a thin flange of
calcareous matter more or less continuous with the sides of
the median process, but principally developed at the outer
side of the lateral recess.

The epithecal sclerites are short, not very conspicuous, and
they are widely separated from the operculum. 8B zocecia
occur in large numbers. In some parts each B is followed
in the longitudinal row by two a, and the second of these
by another 8B; in others, three or more A intervene between
each two B, and sometimes only one A.

The B opercula (fig. 44) vary a good deal in size and shape,
without, however, losing their distinctive characters, the most
important of which is the arrangement of the teeth. These
are developed along the whole length of the submarginal
sclerite ; the proximal ones are small, but the distal ones are
very long, strong and recurved. Minute teeth may excep-
tionally occur between the larger ones (as in the figured
specimen). The parallel part of the main sclerite is usually
moderately long, though not so long and narrow as in 8.
Haddoni. The B operculum is commonly elongated, with

284. SIDNEY F. HARMBER.

straight nearly parallel sides (fig. 44), or it may be short and
broad, intermediate conditions also occurring. The number
of teeth varies from twenty to twenty-four (not counting the
minute intermediate teeth), the proximal six or seven on each
side being very small.

The a opercula (fig. 45) are even more distinctive, being
characterised by the possession of 26—33 minute submarginal
teeth, which absolutely distinguish this species from all others
at present known. ‘The main sclerite has the form of a pointed
or Gothic arch, this feature being well shown in the figures
given by Busk (B. M. Cat.) and Smitt, and there is a distinct
basal sclerite, which is thinner medianly.

The following points may be noted about the specimens
from other localities.

One of the Jamaica specimens (c) agrees well with the
type, except that the cryptocyst is angular and thickened at
the beginning of its descent. Most of the B opercula are
long and parallel-sided. One abnormally small B has only
thirteen teeth. Another Jamaica specimen is remarkable for
the great size and strength of the opercula of both kinds (see
measurements below). The a opercula (fig. 46), which vary
a good deal in their relative length and in their outline, have
unusually large distal teeth, borne on a distinct submarginal
sclerite. The main sclerite is a good deal expanded at its
anterior end. If this process were to continue, the sclerite
might meet the submarginal sclerite and give rise to a form
of operculum essentially similar to 8B, although it will be
noticed that the proximal ends of the main sclerite are of the
A form. The B opercula of this colony are rare, and one or
two are of gigantic size, though not differing in any essential
detail from the type. ‘The flanges of the sides of the zocecia
which roof the lateral recesses give off a process distally
which meets the lateral border of the median process ; some-
times the opesiule thus cut off is subdivided by a second
similar process, thus approaching the condition found
in S. connexa, although differing from that species in
that the formation of the opesiules is not due to out-

A REVISION OF THE GENUS SIRGANOPORELLA. 285

growths from the median process. This has unusually
everted walls, its cavity may be otherwise normal, but in
several cases it is shallow or even evanescent. The (ueens-
land specimen (f) approaches the one last described in the
form of the main sclerite of the a opercula, which are
distinctly large, and in the large size of their teeth, which
number from 22 to 24, The B opercula are relatively short,
the parallel part of the main sclerite being little developed.
The number of teeth is only 18 to 20, the minute proximal
teeth being fewer than in the type. In some of the zocecia
the cavity of the median process is unusually shallow or even
evanescent, the convex (tuberculated) roof of the tube being
almost on a level with the proximal part of the cryptocyst ;
but it may resemble that of the type. The cavity may be
developed on only one side of the roof of the tube. The
cryptocyst may be somewhat thickened and tuberculated at
the commencement of its descent.

Specimen d (St. Vincent; without opercula) and k and 1
(doubtful locality) are not specially noteworthy ; & has no
opercula; 7 (John Adams’ Bank, cf. p. 254) is also a normal
S. magnilabris.

Specimen e (Honolulu) is of Escharan habit, with narrow
branches, as described in the Challenger Report. The zocecia
and opercula are distinctly small, p being variable in form ;
the teeth of A are very minute and even vestigial, and the
basal sclerite is hardly complete across the middle. The
calcareous parts are, in the older regions of the colony, more
massive than in the type, both oral and post-oral shelf being
more developed and more tubercular. The horizontal part
of the cryptocyst is smaller and thicker, and may be thickened
and tubercular where it joins the descending portion. The
asymmetry of the lateral recesses is well marked here, as in
other cases.

Specimen 2 (Philippine Islands), which is not alluded to inthe
‘Challenger Reports’ (xxx and Ixxix), is of Hscharan habit,
but is more foliaceous than the last specimen. The B opercula
are relatively short, though with distinct parallel portion of

286 SIDNEY F. HARMER.

the main sclerite; their teeth number 16 to 21, the proximal
ones being very minute. The a opercula (which, like the
others, are thin and delicate) have even more vestigial teeth ;
the more distal ones alone can be made out, and not more
than twenty can be counted. The opening of the tube is
unusually wide, its sides sloping very much outwards and
downwards, and then somewhat approaching one another, to
join the basal wall, which completes the tube. In a good
many of the zocecia one of the lateral walls of the cavity of
the median process is not developed. The cryptocyst may
be thickened at the commencement of its descent.

Specimen g (Tizard Reef) agrees well with many of the
other specimens. Its back is very nodular, probably from
having encrusted an irregular surface. The opercula are
normal, A having twenty-seven small teeth, and 8 twenty-four
teeth (one operculum of each kind mounted); 8 is short and
nearly semicircular.

Specimen h is the merest fragment, but the characters of
its (dry) opercula show it to belong to this species. It is of
importance as giving another locality for the species.

Measurements of Opercula (in pw) and Number of
their Teeth.

A B
SSS SSE SS
| |

BLPC, Locality. Diameter. Length. | Nove Diameter.| Length. | No 6k
"yetwal SN 8 es 4 Sy Ve ea eeiae pelea ie
a Abrolhos Is. j 450 430-480 26-38 | 480-580) 600-730 20-24
cl Jamaica , . 850-460 | 870-480 30-31 | 820-570 | 430-7202) 13-25
ce x . «480-650 | 480-640 30-82 | 890-960 | 970-1050 20-24.
e€ Honolulu. . 820-370 3830-420 29-33 370-400 | 450-5380 | 23-27
ip Queensland . 480-610 450-580 | 22-24) 560-610| 540-610 | 18-20

g |Tizard Reef .| 400 370 27 620 580 =| 24
~ | Philippine Is. . 400-450 330-880 18-20 450-580| 420-520 | 16-21
l ? 6 430 410 | 37 | 410-640} 500-580 | 20-27

1 The length is measured obliquely from the proximal end of one of the
halves of the main sclerite to the distal border (median) of the operculum.

2 Leaving one operculum out of account, the figures would be :—s,
diam. 430-570; length 590-720.

3 One or two smaller opercula (Bb) were u0l measured,

A REVISION OF THE GENUS STEGANOPORELLA. 287

12. S. alveolata, nu. sp. Figs. 12, 32, 40, 41.

A and B zocecia of about equal size, 4 extremely rare; both
forms shortly oblong with angles hardly rounded, the oral
arch hardly distinguishable. Cryptocyst descending steeply,
without angulation ; in B inserted at or near the junction of
the basal and distal walls, in a meeting the basal wall at a
great distance from the distal wall. Median process with
very deep cavity, the roof of the tube forming its floor ; with
rounded, often everted border in B, appearing transversely
oblong in a. Opening of tube oblique or nearly vertical,
visible or hardly visible from above, complete or incomplete
distally (or basally). Oral shelf forming a trifoliate arch in
B, with a series of marginal sockets or alveoli, each of which
receives a tooth of the closed operculum; in a forming a
rounded arch. 8 opercula with strong A-shaped main sclerite
and a series of extremely strong, curved submarginal teeth,
each of which fits into a distinct socket in the calcareous
part of the zocecium when closed. a opercula transversely
oblong, with basal sclerite and without teeth.

Channel between Mer and Dauer, Murray Islands, Torres
Straits, March 12th, 1889, Haddon Collection (C. M., 24.2.98).

This species was obtained, well preserved, in spirit, and
by its means I have been able to make out some of the details
of the structure of the genus; these I hope to publish sub-
sequently. The species is in some ways the most interesting
of all, the evolution of the B opercula reaching their highest
point. They are moved by enormous muscles, and the occur-
rence of sockets to receive the points of the teeth is a unique
feature in the genus. The excessive rarity of the a zoccia
is another remarkable feature ; in one mounting I counted
only 6 a to 198 8; in another case 3 4 to 86 B.

The description is based on a single piece, of Hemescharan
habit. The zocecia are in the usual longitudinal rows, and are
very regularly quincuncial. The edge is slightly raised and
thin ; and the oral archis hardly higher than the edge of the

288 SIDNEY F. HARMER.

proximal part of the zocecium. The arch is usually not rounded
asin the great majority of forms (a zocecia of S. truncata
excepted), but is typically transversely oblong, with angular
distal corners, giving this species an aspect entirely peculiar to
itself. A few B zocecia occur, however, with a nearly semi-
circular oral arch, even in zocecia which do not precede the
division of a longitudinal row. The post-oral shelf is tuber-
cular and very deep, descending steeply to the much depressed
horizontal cryptocyst, from which it is sharply separated ; it
is usually narrower proximally. The oral shelf of a forms a
semicircular arch, whose upper surface is smooth and regularly
concave, and there are, of course, no tooth alveoli. That of
B 1s trifoliate, its upper surface slightly concave medianly
and just distally to the condyles, but strongly convex above
in the latero-distal parts which render the arch trifoliate.
The shelf of Bis of an entirely different character from that
of other species. Whilst in these the shelf is usually concave
above, or in any case so arranged that there is a considerable
cavity between it and the closed operculum, the two convex
parts of the oral shelf of S. alveolata stand up above the level
of the oral arch, and the concave surfaces of the operculum be-
tween the distal end of the main sclerite and the submarginal
sclerite actually come into contact with and are supported by
these convexities when the operculum is closed. ‘The oral
arch is no thicker than the post-oral edge, and thus is entirely
different from the strong oral arch of other species. The
occurrence of the series of tooth-alveoli just within the very
thin oral arch is highly remarkable. A smaller oval shelf
can be made out in the figure at a deeper level than the main
shelf. This may be regarded as the basal edge of the thick
oral shelf. This edge does not project in A. The condyles
are strong. The cryptocyst is thick and tubercular, its hori-
zontal part small in B, very small in 4; the pores are of
medium size. ‘l'he descent into the median process is very
steep, but without angulation. The cavity of the process is
deep, short and broad in a, and with a rounded, everted
border in B. It may, however, be much compressed, and

A REVISION OF THE GENUS STEGANOPORELLA. 289

with less everted border than in the specimen figured. The
opening of the tube is usually just visible from above, although
it is nearly vertical. The basal wall of a is largely exposed
from above, since the cryptocyst is inserted at a great dis-
tance from its distal end. In B, although the lateral recesses
are very deep, their floor (formed by the cryptocyst) usually
slopes so as to meet the base of the distal wall, or the distal
end of the basal wall. Although the tube may be complete
distally, it is commonly incomplete. In A it appears to be
asymmetrical, one wall joining the lateral wall of the zocecium,
the other joining the basal wall (fig. 12). It is also often
asymmetrical in B (as in fig. 12), and this is correlated with
a curious difference in the lateral recesses. While the floor
of the left one (in the figure) joins the lateral and distal
walls only, that of the right one, while joining these two
walls, dips down medianly at its distal end to meet the basal
wall on the distal side of the tube. In other words, the
cavity of the right lateral recess (in this particular zocecium).
reaches the basal wall at a small region in or near the middle
line of the distal end of the zocecium; and this results in the
formation of a small circular or slit-like mark (fig. 32) on the
back of some of the zoccia. This is, of course, not present if
the cryptocyst joins the distal wall only. It may, however,
be regarded as a common character of this species. It may
be noted that the vertical walls of this species are very thick
and strong.

I have not found distinct epithecal sclerites. The B
opercula (fig. 41) have nearly always six to eight strong
curved distal teeth (counting the two corner ones, which are
often specially large); and there are usually two to four on
each side besides; this number is not often exceeded. In
one case minute interstitial teeth were observed, as in fig. 44
(S. magnilabris). The opercula have the usual delicate
border outside the strong submarginal sclerite; and it is
obvious that this flange is of importance in fitting closely
over the zocwcium, and being so thin as to leave no edge
which could be lifted up by any intruding animal. The

290 SIDNEY F. HARMER.

closure of this species must be remarkably effective. The
parallel part of the main sclerite is short, and the cavity
therein included is much dilated transversely at its distal
end. ‘The proximal ends of the main sclerite are very stout.
The a opercula (fig. 40) are large and transversely oblong.
There is a distinct basal sclerite and a fine submarginal
sclerite in addition to the main strengthening arch.

Key to tHE SPECIES OF STEGANOPORELLA.

(x opercula with four teeth on the

ne main sclerite . : : é 2
ek opercula with two teeth or none
on the main sclerite : 5 =

L

( A opercula with an enormous sub-

| basal sclerite . ; . 6. S.auriculata.
2<~ A opercula with small secondary

| sclerites within the main

le sclerite . ; ; : . 7. 8.neozelanica.

( B opercula with A-shaped main
sclerite . 4 3 : : 4

3< B opercula with fM-shaped main

sclerite ; these opercula usually

[ rare : : ‘ : F 8
(

A opercula with straight or slightly
concave distal border, more or
less distinctly transversely ob-
long, and with a basal sclerite.

4% B opercula with stout teeth . 5
A opercula with very convex distal
border. 8B opercula with minute
teeth or none in their proximal

L half, or with all the teeth small 6

A REVISION OF THER GENUS STEGANOPORELLA. 291

ia opercula with a pair of strong
teeth on the main sclerite, just
| distal to the occlusor tubercle.
B opercula convex distally, with
| a series of strong, slightly
curved, suberect teeth . SOS) tromeat a.
e | A opercula rare, without teeth. B
ae opercula transversely oblong,
| with six to eight strong curved
submarginal teeth distally, and
| two or three others on each
side; the teeth fittimg into
| sockets in the calcareous z0ce-
i cium ‘ : ; ; . 12. 8. alveolata.
f
|
:

A with submarginal teeth; those of
B much stronger distally than
proximally. : : 11. S.magnilabris.

-

| 4 toothless, ‘‘ undifferentiated” . /

( Submarginal teeth of B long, fine,
restricted to the distal half of
the operculum. B zocecia about

= | twice as large as A zocecia » 18.58: addon
(
s

Submarginal teeth of B small, the

series commencing in the prox-

| imal half. B zocecia not twice
L as large as A zocecia . »\ | SuiSy Baska.

( Cryptocyst inserted at or near the
| base of the distal wall ; zocecia
of large size . : : ‘ 9
i Cryptocyst inserted into the basal
wall at a distance from the
L distal wall : : : : 10

292 SIDNEY F. HARMER.

( Median process with greatly deve-
loped lateral wings, which
unite with the sides of the
zocecium . ; :

Median process simple, without

\ lateral wings . : : J A. Ss simplex

9

5. 8. connexa.

An asymmetrical tube, without late-

ral wings, springs from the

descending cryptocyst . . ib. lateralis:
edian process bounded by late-

ral wings is differentiated on

It the upper surface of the tube. iil

105 Am

( Median process with a longitudinal
groove . : : . . 2. 8. sulcata.
11< The roof of a well-developed tube
forms the convex floor of the
L median process ° : . 3. 8S. tubulosa,

The determination of the species will be facilitated by
noticing that in S. magnilabris, 8. neozelanica, 5.
tubulosa, S. sulcata, and 8S. lateralis the cryptocyst
joins the basal wall at a distance from the distal wall, leaving
a considerable amount of the basal wall exposed from above ;
that in S. Buskii, S. Haddoni, and 8S. truncata the
cryptocyst joins the distal wall, the opening of the tube being
clearly visible from above, but not the basal wall ; and that
in S. auriculata, S. connexa, S. simplex, and 8. al-
veolata the cryptocyst is inserted at or near the junction
of the basal and distal walls, the opening of the tube not
being visible from above except in some zocecia of 8. alveo-
lata, which is sufficiently distinguished in other ways by its
quadrilateral zocecia and by the alveoli which receive the
points of the teeth, in the B zocecia,

A REVISION OF THE GENUS STEGANOPORELLA. 298

Bathymetrical and Geographical Distribution,

There is very little to be said under the first of these head-
ings. Most of the records of the occurrence of Stegano-
porella refer to the locality only. S. magnilabris, of
which there are several records, has usually been found at
depths of 10—40 fathoms; but a Steganoporella which
is probably 8. magnilabris is recorded by Ortmann from
shallow water to 200 fathoms from Japan. All the other
localities from which specimens of the genus have been
obtained mention some land or submerged bank; and the
evidence is in favour of its being principally littoral or found
in shallow water.

With regard to geographical distribution, it may be con-
cluded that the genus is a southern one, which is common
between the equator and 50° S., and has extended in one or
two cases to the north side of the equator, reaching 35° N.
in Japan. The only species which are known to occur north
of the equator! are 8S. magnilabris (W. Indies, Sandwich
Islands, Eastern Archipelago, Japan) ; and 8S. Buskii and
S. sulcata, both of which occur in the Indian Ocean. Of
these, S. magnilabris occurs in all the great oceans ; being
found, in addition to the localities already indicated, off the
coast of Brazil and off Queensland; and being the only
species described from the Atlantic Ocean. Jullien has,
however, stated? that he obtained two new species off the
coast of Liberia; and it is not to be supposed that S. Buskii
does not extend along part of the western coast of Africa.
No species is at yet known from the southern part of South
America. The Indo-Pacific region is clearly the head-
quarters of the genus, Torres Straits, with four or five
species (S. lateralis, ?S. sulcata, 8. Buskii, S. Had-

1 Various northern species, recent and fossil, belonging to Thalamo-

porella, have been described under the name of Steganoporella,
2 ‘Miss. Sci. Cap. Horn,’ vi, 1888, p. I. 79,

294, SIDNEY F. HARMER,

doni, 8. alveolata) having a richer representation than.
any other locality. The characteristic species of the Indian
Ocean appear to be S. sulcata and 8. Buskii, while S.
auriculata occurs in Madagascar, and 8S. simplex in the
Amirante Islands. New Zealand has one species (8S. neoze-
lanica), which occurs in two well-marked varieties, one of
which is recorded from Tongatabu. Australia has a larger
number of species; in addition to those from Torres Straits,
S. truncata and 8S. tubulosa occur off its southern coast.

It may further be noticed that MacGillivray! describes
four Tertiary species of Steganoporella from Victoria. Of
these S. patula, Waters, does not seem to me to be a
Steganoporella, as is shown by the occurrence of avicu-
laria and external ovicells, and by the Thalamoporella-
like condition of the cryptocyst. S. depressa, MacGill.,
is not represented in the recent collections I have examined.
S. lateralis and 8. Haddoni (described by MacGillivray
as S. magnilabris) are recorded above from Torres Straits
and other localities.

Waters describes fossil Steganoporella from various
localities? in Australia and New Zealand, but I am not able
to refer them with certainty to any of the recent species.
Forms related to Steganoporella, although probably not
to be referred to that genus, are common in various deposits
in Europe, the Cretaceous deposits being very rich in these
forms, as Jullien (1881) has pointed out. It may probably
be concluded that the Steganoporellide (including Tha-
lamoporella and other similar genera) are a group of world-

1 <'Irans. Roy. Soc. Victoria,’ iv, 1895, pp. 58, 54. MacGillivray uses the
term “opesia”’ for the part of the zocecium distal to the commencement of
the descending portion of the cryptocyst—a use of the term which would be
difficult, to employ in describing a species (e.g. 8. Buskii) in which there
may be no marked line of demarcation. Jullien’s original definition as ap-
plied to Steganoporella shows that the term should be used for the opening
of the tube; in other words, to the opening limited by the free edge of the
cryptocyst.

2 ‘Quart. Journ. Geol. Soc.,’ xxxvili, 1882, pp. 265, 506; xxxix, 1883,
p. 436; xli, 1885, p. 292; xlili, 1887, p. 50,

A REVISION OF THE GENUS STEGANOPORELLA. 295

wide distribution, but that Steganoporella itself is pri-
marily a southern genus.

It is noteworthy that the species of Siphonoporella at
present known (see p. 231) are both Australian; while this
region has a good representation of the allied genera Tha-
lamoporella, Thairopora, and Diploporella. It is not
improbable that Australia may have been a centre from
which species of this group have spread. All the species of
my third group (with A-shaped main sclerite in the B oper-
cula) occur in Australia, although 8. magnilabris occurs all
round the world. Of the second group (with four teeth on
the main sclerite of the A opercula) 8. neozelanica occurs
in New Zealand and Tongatabu, and 8. auriculata in
Madagascar. Of the first group (with f-shaped main
sclerite in the B opercula), S. tubulosa, 8. lateralis, and
possibly 8. sulcata are Australian ; the first being restricted
to Australia (so far as is at present known), the second
occurring as a Tertiary fossil in Victoria, found recent in
Torres Straits and extending to Tahiti; and the third found
also in the Indian Ocean. ‘The other two species are known
from isolated localities,—S. simplex from the Amirante
Islands, in the Indian Ocean, and S. connexa from Brazil.

EXPLANATION OF PLATES 12 & 13,

Illustrating Mr. Sidney F. Harmer’s paper “A Revision of
the Genus Steganoporella.”

PLATE 12.

The figures on this plate were all drawn to the same scale (camera lucida,
Zeiss A obj.; afterwards x 3), and are x 40. (B. M.= British Museum ;
C. M. = Cambridge Museum.)

Fic. 1.—Steganoporella lateralis, MacGill (p. 242). Zocecium a.
Tahiti, Manchester Museum.

VOL. 43, PART 2.—NEW SERIES, x

296 SIDNEY F. HARMER.

Fic. 2.—S. suleata, n. sp. (p. 246). Zoccia a (left) and B (right).
One condyle is wanting in B. Amirante Islands, B. M., 82.10.18, 88.

Fic. 3.—S. tubulosa, n. sp. (p. 250). Zoccium a. Curtis Island,
Bass Strait, B. M., 99.5.1, 29.

Fie. 4.—S. neozelanica, Busk, typical or Vincularian form (p. 261).
Zoecia A. The lower zowcium shows the operculum in situ; e.s. epithecal
sclerite. Wanganui, New Zealand, C. M., 24.5.95.

Fie. 5.—S. neozelanica, Busk, var. magnifica, Busk (MS.) (p. 264).
Zocecium a. Stewart Island, C. M., 24.5.95.

Fie. 6.—S. connexa, n. sp. (p. 254). Zoccium B. John Adams’ Bank,
B. M., 99.7.1, 408.

Fig. 7.—S. simplex, n. sp. (p. 253). Darros Island, B. M., 82.10.18,
125.

Fic. 8.—S8. auriculata, n. sp. (p. 257). Madagascar, B. M., 84.11.18, 1.

Fic. 9.—S. truncata, n, sp. (p. 276). Zocecia a (left) and B (right).
Victoria, C. M., 24.5.95.

Fie. 10.—S. magnilabris, Busk (p. 279). Zocecia a (right) and B
(left). From the type-specimen. Abrolbos Island, B. M., 54.11.15, 222.

Fie. 11.—S. haddoni, n. sp. (p. 268). Zocecia a (left) and B (middle).
Torres Straits, C. M., 24.2.98.

Fic. 12.—S. alveolata, n. sp. (p. 287). Zovecia a (right) and B (left).
Torres Straits, C. M., 24.2.98.

Fic. 13.—S. buskii, n. sp. (p. 272). Zocecia a (lower) and 8B (upper).
Port Elizabeth, C. M., 24.5.95.

PLATE 13.

The figures on this plate, with the exception of the diagrammatic figs. 27—
33 and 43, were all drawn to the same scale (camera lucida, Zeiss c obj. ;
afterwards X 3), and are X 80. ‘The reference to a preceding figure
indicates that the operculum or other structure is from the same colony from
which the figure referred to was drawn. ‘The lettering is explained in the
text. :

Fie. 14.—S8. sulcata. Operculum B (Fig. 2).

Fig. 15.—S. sulcata. Operculum a (Fig. 2).

Fic. 16.—S. sulcata. Operculum B and epithecal sclerites (e.s.). Mergui
Archipelago, B. M., 99.5.1, 28.

Fic. 17.—S. suleata. Operculum 8B and epithecal sclerites. ‘On
Avicula margaritifera,” B. M.

Fic. 18.—S. connexa. B (Fig. 6). The occlusor tendon is seen on the
right side.

A REVISION OF THE GENUS STEGANOPORELLA. 297

Fic. 19.—S. lateralis. a (Vig. 1).

Fic. 20.—S. lateralis. B (Fig. 1). Both occlusor tendons are seen,
that on the right side being displaced.

Fic. 21.—S. simplex. a (Fig. 7),

Fig. 22.—S. tubulosa. a (Fig. 3).

Fic, 23.—S. tubulosa. B (Hig. 3).

Fie. 24.—S. auriculata. a (Vig. 8).

Fie. 25.—S. neozelanica, typical form. Napier, New Zealand, C. M.,
24.5.95.

Fic. 26.—S. neozelanica, var. magnifica. Foveaux Straits, C. M.,
24.5.95.

Fie. 27.—S. lateralis. Back of zoecia (Fig. 1).

Fic. 28.—S. sulecata. Back. Darros Island, B. M., 82.10.18, 125.

Fig. 29.—S. suleata. Variations of median process (Fig. 16).

Fic. 30.—S. neozelanica, typical form. Part of transverse section of the
colony seen from the distal side: 4., basal wall; /.7., vertical proximal wall
of one of the lateral recesses; m.p., distal wall of the flask-shaped cavity of

the median process; ¢., opening of the tube into the subopercular cavity of
the zoecium. New Zealand, C. M., 24.5.95.

Vig. 31.—S. magnilabris. Back (Fig. 10).

Fig. 82.—S. alveolata. Back (Fig. 12).

Fie. 33.—S. buskii. Proximal wall of a zocwcium, showing the insertion
of the cryptocyst, and the two fragmented rosette-plates (Fig. 13).

Fig. 34.—S. buskii. Operculum B (Fig, 13).

Fie. 35.—S. buskii. Operculum a (Lig. 18).

Fic. 36.—S. truncata. 3. Victoria, C. M., 13.5.99.

Fie. 37.—S. truncata. a (Fig. 36).

Fig. 38.—S. haddoni. B (Fig. 11).

Fie. 89.—S. haddoni. a (Fig. 11).

Fic. 40.—S. alveolata. a (Fig. 12). Both occlusor tendons are seen.

Fic. 41.—S. alveolata. B, seen obliquely (Fig. 12).

Fig. 42.—Siphonoporella delicatissima, Busk (p. 232). An entire
zoecium, some of the calcareous parts seen through the epitheca. King
George’s Sound, Western Australia, Manchester Museum.

Fic. 43.—S. delicatissima, Diagrammatic side view (Fig. 42),
Fic. 44.—Steganoporella magnilabris, 3B (Fig. 10),

Fig. 45.—S. magnilabris. a (Fig. 10).

Fic. 46.—S. magnilabris, a. Jamaica, C. M., 30.6.99,

ON A NEW HAISTRIOBDELLID. 299

On a New Histriobdellid.
By

William A. Haswell, M.A., D.Sc., F.R.S.,
Challis Professor of Biology, University of Sydney.

With Plates 14 and 15.

INTRODUCTION.

Dvurine a recent visit to Tasmania I found the minute
animals which form the subject of the present paper living
in abundance in the branchial chambers of the fresh-water
crayfish (Astacopsis tasmanicus) that occurs in streams
in the neighbourhood of Hobart. I am greatly indebted to
Mr. Alexander Morton, F.L.S., the Curator of the Tasmanian
Museum, for his kindness in facilitating my work in Hobart
by every means in his power, and also for afterwards pro-
curing and sending to me in Sydney specimens of Tasmanian
cray fishes.

Histriobdella homari,! the only known relative of the
new animal, is found living among the eggs of the European
lobster (Homarus vulgaris). The first recognisable
account of it was given by P. J. van Beneden (2) in 1858.
Our knowledge of this remarkable animal was greatly
extended in 1884 by Alexander Feettinger (6), who supple-

1 Feettinger’s alteration of both the generic and specific names does not
appear to be necessary, and van Beneden’s name must apparently be re-
stored. Histriobdella is certainly not a leech; but the name Histriodrilus
proposed by Feettinger does not indicate its true affinities with any greater

exactness. Moreover the termination ‘“-bdella” occurs in the accepted
names of several genera that do not belong to the Hirudinea,

300 WILLIAM A. HASWELL.

mented van Beneden’s description of most of the internal
organs, described the nervous system for the first time, and
pointed out the erroneous nature of van Beneden’s conclu-
sions as to the animal’s affinities.

Since the date of Foettinger’s paper Histriobdella has
never been re-investigated, and a good many points in its
structure still remain obscure.

The animal with which the present paper deals, though
without doubt nearly related to Histriobdella, differs from it
in a number of points of greater or less importance; and I
have signalised these differences by giving it a new generic
name—Stratiodrilus. The species I propose to name
S. tasmanicus.

External Features: Movements.

Like Histriobdella, Stratiodrilus is a very small animai, the
largest being only a little over a millimetre in length, and
about one sixth of a millimetre in greatest breadth. In general
shape (figs. 1 and 2) it approaches very near to Histriobdella.
In front is a well-marked head, separated by a constriction
from the body. ‘The head is dorso-ventrally compressed,
convex dorsally, nearly flat ventrally ; in outline as seen from
above it is approximately heart-shaped—the apex, which is
rounded off, directed forwards. ‘There is no distinction into
prostomium and peristomium, and the mouth is situated on
the ventral surface quite close to the anterior extremity.
The head bears seven appendages, arranged exactly in the
same way as the appendages of the head of Histriobdella,
but differing in shape. Five of these appendages are tactile,
and may be called tentacles. The other two aid in locomo-
tion, and may be termed the anterior limbs, Of the tentacles,
one (fig. 1, ¢') is median, and projects forwards from a point
immediately above and behind the middle of the anterior
margin of the head; it is about one sixth of the length of the
head, very slender, cylindrical, and unjointed. The most
anterior pair of tentacles (f*) are a little longer than the

ON A NEW HISTRIOBDELLID. 301

median, and each consists of two distinct segments, the basal
much shorter than the distal. They are attached a little
below and behind the antero-lateral border of the head at
some little distance from the middle line. he second pair
(¢5) are nearly twice as long as the first, attached on the
antero-lateral margin of the head a little behind the first
pair; each consists of two segments, of which the basal is
somewhat longer and thicker than the distal. All the
tentacles are tipped with very fine non-motile sensory cilia,
arranged in a circlet or spiral. ‘The remaining pair of ap-
pendages of the head, the anterior legs (/. a.), are of a very
different character. They are much thicker than the tentacles,
unjointed, and retractile, being capable of becoming com-
pletely withdrawn into the interior of the head by the action
of retractor muscles. They are situated on the ventral surface
of the head, considerably behind the posterior tentacles.
They are somewhat shorter than the latter, of subcylindrical
form, broadest at the base, ordinarily directed outwards,
forwards,and downwards. At the free end is a slight expan-
sion, apparently of the nature of a sucker. Close to the base
of each is a rounded mass of unicellular glands, about half a
dozen in number, the ducts of which traverse the appendage
to its extremity.

The body is regularly constricted at intervals, and may
best be described as imperfectly divided into six segments.
The nature of these can only be discussed after the internal
organs have been dealt with. All the constrictions are much
more strongly marked laterally than dorsally or ventrally.
They are clearly marked in the living specimens. The first
or neck segment is small, and is devoid of appendages. ‘lhe
second has on each side a mammiform elevation, on the
summit of which is inserted one of the cirri of the first pair
(c!). These are slender cylindrical appendages, similar in
character to the tentacles, and each consisting of two segments,
a thicker proximal and a thinner distal. Like the tentacles,
the cirri are tipped with fine non-motile sensory cilia.
Behind this are three rings, which are probably to be referred

302 WILLIAM A. HASWELL.

to the next or third segment, the main part of which bulges
out laterally like the second, and bears a similar pair of cirri
(c?). On this follows a small annulus, probably belonging to
the fourth segment. The main part of the latter is much
broader than the segments in front, bulging out prominently
at the sides. In the female this segment is devoid of ap-
pendages, but in the male it bears a pair of remarkable
organs, the claspers (cl.). These are situated laterally in a
position corresponding to that of the cirri on the other seg-
ments. They are not unlike the anterior legs in their general
shape, but are considerably larger. They are of cylindrical
shape, stouter at the base than towards the free end. ‘I'he
distal extremity is obscurely divided into two lobes, tipped
with a few non-motile cilia; close to this, situated laterally,
are two small rounded elevations. A large unicellular gland
(fig. 14, gl. cl.) lies in the basal part of the interior of the
clasper, its duct opening at the distal end.

The following segment, the fifth, is as wide as the third,
but somewhat shorter. It bears laterally a pair of cirri (c’),
similar to those on the more anterior segments. The part of
the body which lies behind this is sharply marked off from
the rest, as will subsequently be explained. It cannot be
looked upon as a single segment, and it will be preferable to
term it the posterior or caudal region. It nearly equals in
length the two preceding segments put together, but is much
narrower, being in fact the narrowest part of the body. It is
divided by shght constrictions into six fairly regular annuli,
which, however, may become obliterated when the body is
greatly extended. At its posterior end, rather towards the
dorsal side, is the anal aperture. At the sides of this lie the
large posterior legs (J. p.). These are non-retractile, and in a
state of rest usually extend first outwards and backwards,
and then, towards their extremities, bend forwards. They
are much larger than the anterior legs (as long as the entire
caudal region) ; subcylindrical, stout at the base, constricted
towards the free end, which is expanded into a flattened
adhesive disc, the edge of which is divided by notches into

ON A NEW HISTRIOBDELLID. 303

about ten minute lobes. A large mass of unicellular glands
(1. gid.) lies just within the base of each leg, and the numerous
ducts open on the terminal lobes. The expanded terminal
part (foot) of these appendages is strongly adhesive—not
owing to any sucker-like action, as there is no muscular
arrangement for bringing this about, but on account of the
sticky character of the secretion of the gland. On the
posterior border of each leg is a short cylindrical tentacle or
cirrus (c*), tipped with motionless cilia; and close to its base
lies a shorter process of similar character.

Stratiodrilus differs from Histriobdella homari, as
regards the external features, mainly in the presence of the
cirri, of which there is no rudiment in the latter form. The
anterior and posterior limbs and the claspers, though differing
in minor points, are very similar in essentials. Foettinger
has, however, failed to distinguish the adhesive glands of the
posterior legs, with their ducts, from the muscular fibres that
run close to them. He says, “ Nous avons ici, comme dans
les pattes antérieures, un amas de cellules musculaires
composées de deux parties, une centrale, cellulaire avec
noyau et une périphérique, sous forme de fibre. Tous les
fibres se dirigent vers extrémité élargie du membre, et se
terminent en divergeant & peu de distance de son bord
aminci.’! But the fibres referred to are the ducts of the
glands, and the secretion may frequently be seen oozing
through their fine terminal apertures. The greater develop-
ment of the cephalic tentacles in Stratiodrilus is a minor
point of difference.

P. J. van Beneden’s description of the extraordinary move-
ments of Histriobdella applies so well to the form at
present under consideration, that they may be quoted. “On
peut dire sans exagération que c’est un ver bipéde ou méme
quadrupéde, quand il se déplace sur une plaque de verre, ou
tout autre corps uni. Que I’on se figure un clown de cirque
le plus complétement disloqué possible, nous allions méme
dire entisrement désossé, faisant des tours de force et

lL. c., p. 459,

304 WILLIAM A. HASWELL.

@équilibre sur une montagne de boulets monstres qu’il
s’évertue 4 escalader, posant un pied (en forme de ventouse)
sur un boulet, ’autre pied sur un autre boulet, balancant le
corps ou le roidissant, se tordant sur lui-méme ou se cour-
bant comme une chenille arpenteuse, et on n’aura encore
quwune idée trés-imparfaite de toutes les attitudes qu’il prend
au bout de quelques secondes.”

For the “immense balls” (eggs of the lobster) in the above
description substitute “filaments of the branchiz,” and it
would apply equally well to Stratiodrilus, except that the
bending movements of the latter are not so free, being re-
stricted by a certain stiffness of the body, due apparently
to the firmer cuticle. When moving over the bottom of a
glass vessel the mode of locomotion is very grotesque. The
posterior legs are advanced alternately like the legs of a man
in walking, the anterior portion of the body, and particularly
the head, being strongly swayed from side to side. The
anterior legs are also used, though not invariably, and sup-
port the weight of the head and front part of the body. It
is from this entirely unique style of locomotion that I have
derived the name I have given to the genus.

By means of the viscid secretion of the glands of the
posterior legs the animal is able to adhere so firmly to the
smoothest surface that it is difficult to detach it.

On one occasion I found four specimens, out of a number
that had been placed in a glass dish, collected together, and
executing the most remarkable movements. They were in
ceaseless motion, creeping over and under one another,
touching one another all over with their tentacles, and occa-
sionally inflicting a bite sharp enough to cause the bitten
individual to start back with a sudden movement. This
went on for an hour or more without intermission.

Integument and Muscular System.

The integument consists, as in Histriobdella, of a cuticle
and an epidermis. The former, though not very thick eyen

ON A NEW HISTRIOBDELLID. 305

relatively, is remarkably firm, if one may judge from the
fact that the form of the body is not readily altered under
the action of various reagents. In Histriobdella this layer
is described by Foettinger as structureless ; in Stratiodrilus,
on the other hand, it is marked by two systems of fine lines
crossing one another nearly at right angles, as in the cuticle
of many Cheetopoda. The epidermis is a thin layer of proto-
plasm in which cell outlines are not recognisable, but in
which nuclei occur at wide and irregular intervals. No in-
tegumentary glands of any kind appear to occur with the
exception of those situated at the bases of the legs and of
the claspers, and a few small unicellular glands situated in
the neighbourhood of the genital opening in the male.

The integument of Histriobdella would appear from Feet-
tinger’s description and figures to differ from that of Stratio-
drilus not only in the structureless character of the cuticle,
but in its relative thinness, and in the relative thickness of
the epidermis.

The chief muscles of the body are the four longitudinal
muscles (figs. 1 and 9—13, m.d. and m.v.). These have the
form of thin flat bands, two dorsal and two ventral, extend-
ing from the neck constriction to the bases of the posterior
legs. There is no layer of circularly arranged fibres. The
fibres of these bands are flattened in a direction approxi-
mately at right angles to the surface of the body ; each fibre,
of which there are only about ten to twenty in each bundle,
appears to extend through the whole length of the body.

In front of the neck constriction, in the posterior part of
the head, the place of these longitudinal bundles is taken, to
some extent, by oblique and transverse fibres, by means of
which the movements of the head on the neck are effected,
by two pairs of retractor muscles of the jaws, and by the
retractors of the anterior legs. The transverse and oblique
fibres form an imperfect partition between the ccelom of the
head and that of the trunk.

In the third segment of the male are two pairs of retractor
muscles of the claspers (fig. 1, 7. el.) running obliquely out-

306 WILLIAM A. HASWELL.

wards from near the middle of the ventral body-wall ; the
fibres of the more posterior of these extend through the
appendage to its extremity. In the following segment are
two pairs of narrow bands of fibres which act as protractors
and retractors of the penis, running inwards from the lateral
body-wall, the latter in front of and the former behind the
third cirrus, and becoming inserted into the processes at the
base of the penis (figs. 1 and 14, pro. m., retr. m.). In the
same sex, in the interval between the second cirrus and the
clasper, a pair of bundles of fibres run nearly vertically
from the dorsal body-wall to the ventral, enclosing between
them a mesial space in which lie the alimentary canal on the
dorsal side and the nerve-cord on the ventral, with a portion
of the testis between. Further back again a similar pair of
dorso-ventral bands separate the alimentary canal, nerve-
cord, and penis, situated mesially, from the testes and
seminal vesicles at the sides. In the female a pair of bands
of the same character (fig. 11, m. ob.) occur in the region of
the anterior part of the ovary. In both sexes a strong band
of transverse fibres extends across between the fifth and the
following segments; it does not seem to form a complete
partition. Throughout the body slender oblique bundles
occur at fairly regular intervals, running from the cuticle
of the lateral surface to that of the ventral near the nerve-
cord.

The dorsal and ventral longitudinal bands both send con-
tributions of fibres to a pair of large flexor muscles (fig. 1, fl.)
which run through the posterior leg on its anterior side, and
eventually terminate in the minute lobes at its distal end.
From the ventral longitudinal band a bundle of fibres runs
backwards and outwards to become inserted into the cuticle
about the middle of the ventral surface of the leg. A few of
the fibres of the extensor muscle run nearly transversely in-
wards as a narrow band which unites with the corresponding
band of the opposite side. A narrow bundle runs obliquely
inwards and backwards from the angle between the leg and
the caudal region to the posterior median depression between

ON A NEW HISTRIOBDELLID. 307

the legs; and from the latter point a pair of small bundles
run forwards parallel with one another, one on each side of
the anus. A small muscle runs along the posterior border of
the leg, and another crosses its cavity nearly transversely
from the base of the cirrus to the anterior border.

Digestive System.

The mouth, a wide, somewhat quadrilateral aperture, is
situated, as already stated, close to the anterior extremity of
the head. From it a narrow cesophagus (figs. 6 to 8, «s.)
leads backwards and slightly upwards through the head to
open into the stomach. Below the cesophagus lie the jaws
(figs. 1, 4, 5, 7, 8), the anterior extremities of which when
they are retracted lie just within the mouth opening, while
the posterior ends are at the posterior limits of the head.

The chitinous pieces of the jaw apparatus (figs. 4 and 5)
are arranged in two sets, which, though linked together, are
capable of being moved independently to some extent. One
of these two sets—the upper jaws—consists of a median
piece which I will call the fulcrum, and two sets of lateral
pieces composing the rami. ‘The latter set—the lower
jaws—is paired throughout.

The fulcrum of the upper jaws (/.) is a slender, nearly
straight rod lying between and somewhat above (dorsal to) the
lower jaws. Articulating with its distal end is a small median
piece, and with this articulate the right and left rami.
The latter consist each of a number of freely articulated
basal pieces supporting four teeth. The teeth are provided
with hooked claw-like extremities, and their inner surfaces
are beset closely with extremely fine transverse ridges,
giving them on that aspect the appearance of minute curry-
combs. When at rest the fulcrum is drawn back, so that its
posterior end is nearly on a level with the posterior ends of
the two lower jaws. When it is in this position the rami
are folded up into a small compass with the teeth inwards,
between and dorsal to the anterior portions of the lower

308 WILLIAM A. HASWELL.

jaws. When this part of the apparatus is brought into use
the fulcrum is pushed forwards by the action of its protractor
muscles, and the two sets of rami, becoming thrust out
through the aperture of the mouth, become widely divari-
cated with the teeth at their outer ends. When the upper
jaw has been fully exserted in this way the right and left
rami are brought together sharply, the fulcrum being jerked
back slightly at the same time. This series of movements is
effected with great rapidity, so that it is extremely difficult
to follow and analyse them. The chief part of each of the
two lower jaws is a stout, slightly curved rod (j.”), thickest
behind and tapering slightly in front. These rods lie nearly
parallel with one another, but diverging slightly anteriorly.
The most anterior part of each (about one seventh of the
length of the whole) articulates with the rest by a transverse
joint. Behind this to about the middle of the posterior portion
of the rod runs a thin, internally projecting flange with a
smooth inner edge. Firmly fixed to the anterior portion of
each rod along its inner edge is a broad plate, the inner edge
of which is in contact with that of its fellow of the opposite
side. ‘lhe anterior edge of this plate is finely denticulated ;
its antero-lateral angle is produced into a pointed process
directed outwards and backwards.

Connecting together the rami of the upper jaw with the
lower jaws on each side is a sort of bridle (br.) composed of
two pieces, the posterior of which curves over the rod of the
lower jaw, and slides along it when the upper jaw is pro-
truded or retracted. he effect of this arrangement is to
restrict the forward movement of the upper jaw, the curved
piece being checked when it reaches the anterior broad plate
of the lower jaw above described, and further movement of
the upper Jaw forwards being thus prevented. At the same
time, as will be explained presently, it is through the inter-
mediation of the bridle that the biting movements are carried
on. Whether the lower jaws have any function beyond merely
supporting the upper jaw and controlling its movements is
not clear. I have not observed them performing any inde-

ON A NEW HISTRIOBDELLID. 309

pendent movements; but the strength of their muscles and
the toothed character of their anterior edges would seem to
indicate that they play something more than a merely passive
role.

In addition to the bundles of fibres which play the part of
protractors and retractors, the jaws have three other sets of
muscles concerned with their movements. One of these is a
pair of large bundles of non-striated fibres, each of which is
wrapped round the ventral side of the corresponding lower
jaw, the fibres running forwards parallel with the latter
throughout their length. These two muscles are in close
apposition with one another along the mid-ventral line,
separated, however, by a thin septum of nucleated material
continuous with the lining of the head ccelom, of which it
appears to be a thickening. They are continuous with the
retractor fibres behind. The ventral edge of each is in-
folded, and becomes continuous with the ventral edge of the
corresponding muscle of the second pair. The latter (figs.
4 and 7, str. m.) are a pair of bundles of transversely striated
muscular fibres, which are in immediate contact with the
lower jaws and enclosed ventrally by the muscles just men-
tioned ; behind they arise from the main shaft of the lower
jaw, towards its posterior end; in front they are inserted
into the chain of pieces which I have called the bridle. The
third set consists of a number of non-striated fibres which
run forwards parallel with and close to the slender central
shaft of the upper jaw (fig. 7, 7.1).

The precise mode of action of these various muscles is very
difficult to determine with certainty. But there cannot be
much doubt that the striated bundles bring about some
movement which has to be performed with special rapidity
and strength. From their connections, and what I have been
able to observe with regard to their mode of action, I am
led to conclude that, acting through the bridles on the lateral
parts of the upper jaw, their function is to bring about
the sharp movements by which these are brought to bear on
an external object in the act of biting.

310 WILLIAM A. HASWELL,

Foettinger’s figure of the jaws of Histriobdella homari
resembles in essentials that given by P. J. van Beneden, and
represents a structure widely different from that of the jaws
of Stratiodrilus, though probably reducible to the same
general type. Both figures are very general; but it would
appear that one of the most striking differences lies in the
shape of the lower jaws, which are comparatively wide, and
in the larger number of teeth in the upper jaw. The bridles
are figured by both authors, but their significance was appa-
rently not detected by either. Van Beneden’s description is
as follows :!

“Tl ya d’abord deux miachoires placées symétriquement et
qui se correspondent compléetement sous tous les rapports.
Elles ont une couleur bistre, s’allongent en arriére sous forme
de lames jusque prés de l’extréme limite de la région cépha-
lique, et laissent un certain espace entre elles. On pourrait
les comparer a des élytres trés-allongées de Coléoptére légére-
ment écartées l'une de lautre, surtout vers leur extrémité
postérieure. . . . Ces machoires sont également larges
sur toute leur longueur; leur extrémité libre en arriére est
tronquée obliquement.

“Hn avant, ces organes chitineux se touchent au point de
se confondre, en s’unissant a la troisisme piece dont nous
allons parler.

“Ces machoires, vers leur extrémité libre antérieure, qui
est logée au fond de l’entonnoir, devienne rugueuses a la sur-
face et se hérissent méme de courtes aspérités qui leur donnent
une apparence de brosses. Au lieu d’étre terminées en
pointe en avant comme on le voit communément pour ces
piéces de la bouche des parasites, ces organes sont tronqués
en travers.

«A la base de cette portion rugueuse, on appercoit encore
une éminence crochue, dont la pointe est dirigée en dehors et
en arriére, et qui semble empécher le retrait de ce singulier
appareil de succion, quand il a perforé les parois des ceufs
dont il suce la masse vitelline.

Mc. p. a4.

ON A NEW HISTRIOBDELLID. ott

“A ces pieces paires se joint une troisiéme piéce impaire
plus courte et beaucoup plus gréle que les précédentes, de la
méme couleur et de la méme consistance, et qui fait, par son
extrémité postérieure, l’effet d’un stylet, dont les autres
formeraient la gaine. Cette derniére, en effet, est étroite
dans toute sa longueur, et son extrémité postérieure est
entiérement libre.”

Feettinger does not add much to this. He merely states,
“Les machoires sont au nombre de trois, une médiane et
deux latérales; celles-ci, réunies en avant par une partie
impaire et situées du cété ventral, ont assez bien la forme
@élytres trés allongées de Coléoptére ainsi que le décrit P. J.
van Beneden. A cdté de leur terminaisons antérieures se
trouvent deux petites languettes chitineuses, et plus en avant
deux masses de méme nature, a surface hérissée de pointes,
articulées par leurs extrémités postérieures avec la partie
impaire, et pouvant se mouvoir latéralement de facon a rap-
procher ou a écarter leurs bords antérieures. La machoire
médiane, placée au dessus des deux autres leur est réunie en
avant. Je ne métendrai pas plus longuement sur l’aspect de
cet appareil, P. J. van Beneden en ayant donné une descrip-
tion complete.”’!

It will be observed that both van Beneden and Feettinger
agree in connecting the part bearing the teeth with the paired
lower jaws rather than with the median upper jaw.

From the mouth a narrow cesophagus runs backwards
through the head to open into the stomach. The latter is a
tolerably wide sac extending through the first, second, and
third segments. In the fifth segment there succeeds a very
narrow canal, much more contracted in the female than in
the male, leading to the intestine, a comparatively wide tube
running through the caudal region to the anal aperture.

The wall of the alimentary canal is composed throughout
of a single layer of cells, beset on their inner surfaces with
numerous long cilia. Here and there in the wall of the
stomach is to be distinguished a non-ciliated cell, which

IL. c., p. 462.
VOL. 43, PART 2.—NEW SERIES. Y

312 WILLIAM A. HASWELL.

becomes affected by staiming agents much more strongly
than the rest; these are probably of the nature of unicellular
digestive glands. External to this there is merely a thin
peritoneal layer without any muscular fibres.

The stomach and intestine invariably contain a quantity
of miscellaneous granular particles which are so finely com-
minuted as to afford no clue to their nature.

Body-cavity.

There is an extensive body-cavity sending a prolongation
into the head. In Haistriobdella, Foettinger describes this
cavity as lined by a ceelomic epithelium having the usual
relations of such a membrane, a splanchnic layer covering
the surface of the digestive canal, and a somatic layer lining
the inner surface of the body-wall. But such a description
does not give a correct idea of the ccelomic wall, at all
events in Stratiodrilus. Covering the stomach and intestine
throughout is the splanchnic layer of ccelomic epithelium, a
thin layer of flattened cells with small nuclei. But the soma-
topleure remains in a very primitive condition. Closely
applied to the inner surfaces of the dorsal and ventral longi-
tudinal bands of muscle is a single layer of cells, the proto-
plasm of which is seen in the best series of sections (fig. 3)
to be completely continuous with the muscle substance of the
fibres. These cells, which are obviously the cells by means
of which the muscular fibres have become formed, are also
the only representatives of the somatic layer of the meso-
derm. This condition of things corresponds exactly to what
has been described by Fraipont as occurring at a certain
stage in the development of Polygordius. In the latter
the somatic layer of the ccelomic epithelium subsequently
becomes formed by the division of this single layer into two;
in Stratiodrilus the embryonic condition remains permanent.

There are no mesenteries of any kind, the wall of the
stomach and intestine being simply fused on the dorsal side
with the ectoderm as described by Feettinger. In this

ON A NEW HISTRIOBDELLID. 313

position the ectoderm is thicker than in most other situa-
tions, and in transverse sections a pair of nuclei are most
regularly to be observed in this thickened area; the double
row of cells which those represent would thus seem to form
a cord having the function of supporting the digestive canal.
The special developments of the ccelomic epithelium in the
genital region will be described in the section on the repro-
ductive organs.

The ccelom of the head is almost completely cut off from
that of the trunk by the muscular fibres of the neck constric-
tion and the gland cells that lie in that region. But this
separation is not complete, as evidenced by the fact that in
several female specimens sperms were found to have pene-
trated into this region.

Nervous System.

The nervous system (figs. 1 and 2) consists, like that of
Histriobdella as described by Foettinger, of a brain, a pair of
cesophageal connectives, and a ventral nerve-cord with gan-
glia at intervals. The brain (figs. 1, 2, 6, 8), situated in
immediate relation to the integument of the dorsal surface of
the head, consists dorsally of a mass of nerve-cells (br. ¢.),
and ventrally of a mass of fibrillated material (br. f.). Of
the nerve-cells, special groups (tentacular ganglia) (fig. 6)
situated opposite the bases of the tentacles give off peri-
pherally nerve-fibres which run to the extremities of the
latter. The fibrous material is in the form of a curved
transverse band obscurely divided into two portions, anterior
and posterior. Running back from the main mass of the
brain at the sides of the cesophagus is a pair of processes
which are perhaps to be looked upon as representing the
visceral nervous system (“nerfs sympathiques”’? of FF cet-
tinger).

The ventral nerve-cord consists of a strand of finely fibril-
lated material and groups of small nerve-cells similar to
those of the brain. In transverse section the fibrillated cord

314 WILLIAM A. HASWELL.

has the shape in different regions sometimes of an entire
oval, or is bilobed, or more or less deeply cleft, or even com-
pletely divided. The ganglia consist of very slight enlarge-
ments of the fibrillated cord, covered on its ventral and
lateral aspects with the nerve-cells; where a nerve is given
off, the group of nerve-cells is produced for a short distance
around its base.

There are five ganglia, one for each segment, in the
internal region of the body. The first ganglion is short, but
(as regards its group of nerve-cells) expanded transversely.
The fibrillated cord is here deeply divided into right and left
portions, each continuous with the cesophageal connective of
its side. The second ganglion, which is very close to the
first, is of much larger size; it is situated opposite the cirri
of the first pair, and gives off a pair of nerves ending in a
pair of ganglia at the bases of the cirri. From the nerve-
cells of these lateral gangla nerve-fibres pass along the
axis of the cirri to the extremities, where they terminate in
connection with the sensory cilia. In transverse section the
second ganglion appears very distinctly double, especially in
its posterior portion; in the female it is completely divided
into two parts, separated by a definite gap. The connection
between the second and third ganglia is of considerable
length, and is very distinctly double. The third ganglion
gives off a pair of nerves to a second pair of lateral ganglia.
In the male the fibrous cord is not distinctly divided, but
further back it is divided into two completely separated
though closely apposed portions ; in the female it is deeply
divided throughout. The connection between this and the
fourth ganglion is not cleft, but only obscurely divided in the
male; in the female it is deeply cleft. The fourth ganglion
is situated opposite the claspers in the male, and in a corre-
sponding position in the female. It gives off a pair of
nerves which in the male supply the claspers, while in the
female thev end in a pair of small lateral ganglia. In the
anterior part of this ganglion the cord is not divided ; further
back it is bilobed; yet further back it is undivided and

ON A NEW HISTRIOBDELLID. 315

dorso-ventrally compressed. In the male the cord just
behind this ganglion and immediately in front of the penis
gives off a pair of strong branches, and then becomes greatly
reduced, passing towards the dorsal side as a double cord, to
run between the intestine and the penis, in which position it
enlarges into a small ganglion, the fifth, completely divided
into two lateral bodies ; this gives off a pair of nerves to the
ganglia at the bases of the third pair of cirri. In the
female the nerve-cord becomes extremely attenuated behind
the fourth ganglion (in the neighbourhood of the dilated
median part of the ovary), but retains its ventral position ;
the fifth ganglion is dorso-ventrally compressed in its anterior
portion, but loses this character further back where it gives
origin to a pair of nerves passing to the ganglia at the bases
of the cirri of the third pair.

In the caudal region the ventral chain may be described
either as represented by a single elongated ganglion imper-
fectly divided into five or six portions, or as consisting of five
or six imperfectly separated ganglia. Nerve-cells clothe the
nerve-cord ventrally and laterally through all this portion of
its extent, except that there are about five narrow intervals in
which they are almost absent, the breadth of the intervals
differing in different specimens according to the degree in
which the body is contracted. Throughout this posterior
region the cord is deeply cleft. From the posterior end of
the cord nerves pass to the posterior legs, and to a pair of
ganglia situated at the bases of the cirri which they bear.

The account of the nervous system of Histriobdella
homari given by Foettinger corresponds fairly closely with
what I have found in Stratiodrilus as described above, except
that in the former in the caudal region there are only three
ganglia, somewhat better defined than those in the corre-
sponding region of Stratiodrilus, and that the lateral ganglia
are absent, or at least have not been recognised. A more
important point of difference is that the nerve-cord of His-
triodrilus would appear to be in complete continuity with the
epidermal layer, while in Stratiodrilus it is much more dis-

316 WILLIAM A. HASWELL.

tinctly differentiated ; a comparison of my figures of trans-
verse sections with those of Fcettinger will show how marked
this difference is.

There are no organs of special sense, unless we reckon as
such the tentacles and cirri; there are no vestiges of eyes,
and the ciliated pits described by Foettinger as occurring in
Histriobdella are not present.

Excretory System.

The excretory organs (fig. 1) take the form of a series of
pairs of ciliated canals. These are for the most part very
thin-walled, so that they are only to be traced in the living
animal by the movement of the cilia, and are not to be
followed with any certainty in any of my series of sections,
except in one or two localities where their walls are thicker.
A good many details thus remain to be elucidated, but
the following general features have been satisfactorily made
out.

The arrangement of these canals differs considerably in the
two sexes. In both the system extends forwards into the
head, and backwards as far as the posterior end of the body.
Each nephridium of the most anterior pair divides in the
first segment into an external and an internal branch. The
former runs right forwards into the head. The latter crosses
obliquely over to the opposite side, and joins the external
branch of the opposite nephridium. Judging from the
direction of movement of the cilia, which is always from
behind forwards, the external apertures of this pair of
nephridia must be in the head. None of the other nephridia
are branched. In the female an apparently continuous line
of cilia is traceable backwards on each side from the head
canals to a point some little distance behind the second
cirrus, where a canal is clearly traceable, which, after bend-
ing round in a loop, opens on the exterior on the ventral
side. But as the direction of movement of the cilia is from
before backwards in the posterior part of this line, it would

ON A NEW HISTRIOBDELLID. 317 .

appear probable that there are two pairs of canals in this
anterior region in the female. In the male, on the other
hand, there is no such evidence of division, the pair of
nephridia which branch in the head being traceable back-
wards, without change in the direction of the cilia, nearly as
far as the bases of the second cirri, at which point they bend
inwards and terminate in the ccelom near the middle line.
In some specimens each tube seemed to end in a loop, in
others this was clearly not the case; a difference in the
degree of contraction may have been the cause of this dis-
crepancy. In all cases the posterior part of the canal, from
the point where it begins to bend inwards, has comparatively
thick granular walls. The extremity of each is not funnel-
like, but is enlarged into a rounded knob which has the
appearance of having a narrow cleft on it; but I am not
certain of the existence of a coelomic aperture. The two
knob-like ends he in a compartment of the ccelom, bounded
by the stomach above and the ventral nerve-cord below, and
at the sides by a pair of fibrous partitions passing vertically
from the stomach to the ventral wall of the body.

In the fourth segment the nephridia are probably repre-
sented in the female by the oviducts, in the male by the vasa
deferentia.

In both sexes a pair of nephridia, which begin in the fifth
segment (in a loop in the male), run backwards through the
caudal region at the sides of the intestine, and terminate
close to the anus. ‘I'he direction of movement of the cilia in
these is from behind forwards.

The arrangement of these canals, though to some extent
partaking in the metamerism of the body, is not strictly a
metameric one, there being apparently only three pairs in
the male and four in the female.

Ciliary flames have not been observed, and, I think I may
say positively, do not occur in any part.

To judge from Feettinger’s description and figures, there
is an important difference between Histriobdella and Stratio-
drilus as regards the excretory system. ‘Ces canaux ue se

318 WILLIAM A. HASWELL.

rencontrent pas dans toute l’étendue du corps de Histrio-
drilus. Je n’en ai pas vu la moindre trace dans la téte ;
aussi, sans en vouloir nier d’une facon absolue la présenee,
je suis porté a croire quwils n’y existent pas.”! ‘ Dans la

apa: Die PS Sp Rer : 2
partie tout a fait postérieure du corps je n’ai jamais pu dé-
couvrir d’organes excréteurs.”’”

Reproductive System.

The male reproductive organs (figs. 1 and 1416) consist,
in addition to the claspers, of two testes fused together in
part of their extent, two seminal vesicles (ves.), two lateral
vasa deferentia (v. def.), a median ejaculatory duct, a median
chitinous penis (p.), two sets of granule glands (gr. gid.), and
a pair of accessory glands (ac.). The claspers have been
already referred to. In the interior of the base of each is a
large unicellular gland (fig. 14, gl. cl.), the duct of which opens
at the extremity. The testes when fully developed fill the
greater part of the cavity of the third, fourth, and fifth seg-
ments. Anteriorly (in the third and partly in the fourth
seoment) the right and left testes are separated from one
another by a distinct space ; posteriorly they are completely
fused. They consist of oval masses of spermatidia and
sperm, the fully developed sperms being in later stages of
formation, most abundant towards the posterior end. A
thin envelope invests the whole.

The seminal vesicles (ves.) are a pair of oval sacs situated
laterally in the interior of the testes, just in front of the third
cirri. Hach has on its dorsal aspect a wide, nearly longi-
tudinal slit, the edges of which are beset with vibratile cilia.
In the interior, in mature specimens, is always a large mass
of sperms. On the ventral surface are usually to be observed
several curved ridges, which are found when carefully traced
to be continuous with the ducts about to be described as

1L. c., p. 469.
? Thid., p. 471,

ON A NEW HISTRIOBDELLID. 319

those of the granule glands. These ridges are formed by
accumulated masses of the secretion of these glands.

The glands which I have termed granule glands, on account
of their resemblance to the glands so named in the ‘Turbel-
laria and some Trematodes, are situated on each side imme-
diately behind the base of the clasper. In each of the two
groups there are about half a dozen of these glands, which
are pear-shaped and unicellular. The narrow end of each,
which is directed inwards, is prolonged into a delicate duct
which runs to the seminal vesicle, into which it opens on the
ventral side. The rod-shaped granules which the glands
secrete are thus mixed with the sperms in the cavity of the
seminal vesicles. Sometimes the ducts are found to be dis-
tended with accumulated masses of the secretion.

The vas deferens is a thin-walled, widish tube, which
runs inwards to a point in the middle line close to the base
of the penis, where it unites with its fellow to form the
median ejaculatory duct.

The penis (figs. 14—16) is a hollow chitinous spine, per-
forated throughout by the ejaculatory duct. At its base it
is produced into three processes, one median and two lateral,
for the insertion of the protractor and retractor muscles. It
is broadest at the base and tapers gradually distally, ending
ina sharp point. At the free end it is cut off obliquely like
the needle of a hypodermic syringe. Near the extremity it
bears two very minute spinules, one dorsal and one ventral.!
When at rest the penis lies enclosed in a folded integu-
mentary sheath, which projects more or less prominently on
the ventral surface, its pointed extremity directed backwards
and downwards, and just protruding through the median
ventral reproductive aperture. In a good many preserved
specimens it was found fully protruded when it extends
forwards and slightly downwards from the reproductive
aperture at the end of the everted sheath.

The glands which—their function being unknown—I have

1 The shape of the penis and its processes differs somewhat in different
specimens,

320 WILLIAM A. HASWELL.

termed accessory glands are small, sharply contoured, oval
bodies ‘(02 mm. in length, lying one (ac.) on either side of the
penis behind the vas deferens. The long axis is directed
forwards and inwards, and from the narrower inner end
there arises a thin-walled duct, which opens into the
sheath of the penis. In the interior of the gland is a well-
defined lumen; the wall is composed of a small number of
cells arranged in a single layer, each bulging somewhat in
the middle into the cavity.

Foettinger has failed to recognise the significance of vari-
ous parts of the male reproductive apparatus in Histriobdella,
owing mainly to his having followed P. J. van Beneden, and
taken the claspers for a pair of penes. He describes the
seminal vesicles, though without fully recognising their nature
or their relations and tracing their ducts (in which he observed
sperms) to their union to form a median duct. Of the median
structure on which this opens he says, “ Celle-ci est cylin-
drique et pourvue d’un canal assez étroit qui, d’apres ce que
jai vu sur le vivant, doit étre le tube impair; elle a une
structure peu déchiffrable ; on dirait avoir affaire 4 un pénis.”

The chitinous hollow spine of Stratiodrilus is not repre-
sented, but a number of very minute spinules, represented
in his woodcut on p. 488, though not referred to in the text,
have probably a similar function.

The granule glands are the cells which Fcettinger describes
and figures as ‘‘cellules pariétales.” With regard to these
he states,’ “ Au niveau de la partie antérieure de ces vesicules,
on voit les cellules pariétales qui avoisinent le tube digestif
et les muscles dorsaux faire fortement saillie dans le segment
et se recourber vers le bas en longeant les extrémités internes
de leur congénéres. Les parties recourbées sont tres étroites
et arrivent a la face dorsale des vésicules; ot elles se divisent
en deux feuillets nucléés formant une sorte de revétement
cellulaire’ From the figure (pl. 29, fig. 2) to which refer-
ence is made it is evident that what are here referred to as
the ‘parties recourbées” are the ducts of the granule

Pe Paton

ON A NEW HISTRIOBDELLID. 321

glands. The irregular masses which he figures as projecting
into the cavities of the vesicles, and which he describes as
“des corps allongés, plus ou moins cylindriques, droits ou
non, homogénes, trés réfringents sur le vivant et qui semblent
unis aux parois par une base assez larges,”! are probably
the masses of the accumulated secretion of these glands to
which reference is made above.

In the female the ovaries (figs. 11 and 12; ov., fig. 17)
occupy a corresponding position in the body to that occupied
by the testes in the male. Anteriorly they diverge; poste-
riorly they are coalescent. The formation of the ova begins
in the anterior portion of each ovary (fig. 11), and as we
pass backwards they advance in development. In nearly all
the specimens examined the whole of the posterior part of
the united ovaries is composed of a single immense ovum,
very much larger than any of the rest, and occupying nearly
the entire interior of the body in this situation, the alimen-
tary canal and also the nerve-cord being in this position
ereatly attenuated. The diameter of this relatively enormous
ovum is as much as ‘2 mm.; its nucleus about ‘02 mm. Its
cytoplasm is coarsely granular, in which it contrasts strongly
with that of the smaller ova. In a few cases, however, there
is a second ovum, somewhat approaching the largest in size,
and resembling it in the coarsely granular character of the
cytoplasm.

The entire ovary is invested in a layer of nucleated mate-
rial, which is probably to be regarded as specially developed
peritoneal epithelium. Probably it is from the cells of this
layer that new ova are formed. It forms a complete investment
for all the larger ova, and this investing follicle, which is of
considerable thickness in an ovum approaching maturity,
has doubtless the function of ministering to its nourishment.

A pair of specially modified nephridia appear to act as
oviducts (fig. 11, od.). These open on the exterior in a
lateral position behind the second pair of cirri, and opposite
the anterior paired portions of the ovary. Hach runs first

Pie: p.. 487.

3822 WILLIAM A. HASWELL.

forwards and inwards, and then bends round, following the
line of the anterior border of the ovary, and runs backwards
to open near its fellow of the opposite side into the anterior
part of the space (uterus) containing the large mature ovum.
It is a comparatively wide tube, ciliated internally, with
thick walls, having a granular appearance, due evidently to
the presence of numerous minute bright granules or vesicles.
In close relation to it is a glandular body (vit.), of varying
size, consisting of finely granular material, with a large nu-
cleus here and there, but without cell limits and without
lumen. When well developed this body fills up a good deal
of the space between the wall of the body, the alimentary
canal, and the lateral paired portion of the ovary. It appears
to terminate behind in close relation to the corresponding
oviduct. Iam in doubt whether these bodies are to be looked
upon as shell glands or as vitellaria. I think the latter view
is the more probable, and accordingly I have provisionally
given them that name. If they have this function the shell
must be secreted either by the cells of the follicle or by the
wall of the oviduct.

When a ripe ovum has become discharged its place is
taken by the next in size. This must receive accessions of
vitelline matter with great rapidity, as the median ovum in
mature animals is nearly always greatly larger than the next
in point of size. From their arrangement it is evident that
the ripe ova are derived from the right and left sides alter-
nately. The shrivelled follicle of the ovum which has been
last discharged is sometimes to be found pushed on one side
by the ovum which has succeeded.

Foettinger’s account! of the female reproductive organs in
Histriobdella differs from the above in several important
points. The structure of the ovaries is evidently similar in
all essential respects, except that in Histriobdella there is
not, as in Stratiodrilus, a single ovum greatly predomi-
nating in size over the rest—several ova of approximately
equal size occurring together; and that in the former the

Me. spsada.

ON A NEW HISTRIOBDELLID. 323

posterior portion of the organ extends nearly to the posterior
end of the body. The ducts would appear, however, to be
widely different. From each female aperture there runs a
very short canal opening into an ampulla, the cavity of which
is drawn out into digitations. This often contains a granular
material, which passes out and spreads over the surface for
some distance around the reproductive aperture. Usually one
only of the digitations communicates with another ventrally
placed vesicle of spherical form, containing bodies supposed
to be sperms. This vesicle communicates by a constricted
portion with a flattened canal, having cellular walls ciliated on
the dorsal side only ; this opens into the body-cavity.

Living sperms were found in abundance in the body-
cavities of several females. In one instance they had pene-
trated in large numbers into the head, the coelom of which
is not completely cut off from that of the trunk. In one
instance they were found in the tail region—the partition
between this and the segment in front apparently not being
sufficiently complete to prevent their passage.

In several specimens dense masses of sperms were found,
always in the neigbourhood of the ripe ovum. But it was
only in one specimen that I happened to meet with the
appearances represented in fig. 12, which appear to explain
the mode of impregnation. Here a darkish body (spr.),
having the size and shape of a cast of the internal cavity of the
penis, with short prolongations representing the three basal
processes, was found with its point directed inwards, close
to the single large ovum and close to the internal opening
of the oviduct. Close to it in front, in the next section, is a
mass of sperms which had begun to become scattered. Ob-
viously the foreign body is the case of a spermatophore,
thrown off from the inner lining of the penis. After having
been discharged—the penis having previously been thrust
through the body-wall—the spermatophore had become rup-
tured and its contents liberated. In the other specimens in
which sperms were found in masses, the case of the spermato-
phore had apparently become absorbed.

324 WILLIAM A. HASWELL.

This observation renders evident the purpose of the pair
of claspers with their adhesive glands and the peculiarly
shaped penis. In the act of copulation the male, holding the
female fast by means of the claspers, drives the sharp-pointed
penis through the body-wall in the neighbourhood of the
mature ovum, and discharges a spermatophore into the body-
cavity.

Fertilisation is thus internal, but the fertilised ovum would
appear to be deposited at once, as no segmenting ova were
ever found. The section represented in fig. 12 shows definite
processes given off by the ovum towards the mass of sperms ;
these may be of the nature of receptive prominences, or
perhaps are processes formed during maturation. The body
lettered pl. in fig. 12 is most probably a polar body.

As it passes out the oosperm becomes enclosed in a firm
shell, and is attached to the axis of a gill-plume or an epipo-
dite, usually near its base.

Only a few stages in the development of the embryo have
been examined ; a full account of this part of the subject I hope
to be able to communicate at some future time when sufficient
material is available. So far as they go, my results are in
full conformity with the hypothesis dealt with in the following
section, that the Histriobdellide are derived from the Roti-
fera. When it escapes from the egg, the young Histriodrilus
is fully formed in all respects, except as regards the repro-
ductive organs.

Affinities of the Histriobdellide.

P. J. van Beneden (1) in his earliest communication on the
subject referred Histriobdella with doubt to the Poly-
cheeta, as perhaps the larva of a Serpulid. In his later
paper (2) he assigned it to the Hirudinea.

Foettinger (6) enters into a full discussion of this question,
and comes to the conclusion that Histriobdella is nearly
related to Polygordius and Protodrilus, and ought to be
looked upon as a member of the class Archiannelida, and

ON A NEW HISTRIOBDELLID. 325

this view has been generally accepted by later writers,
though frequently with some reservation.

Harmer (12, p. 22) assents to Foettinger’s views as to
affinities, and adds, “In the number of segments, in the
segmentation of the ventral nervous system, and in the
arrangement of the muscular system Dinophilus more nearly
approaches Histriodrilus than any of the other Archianne-
lida.” Hatschek (15) suggests that Histriobdella may be a
degenerate Hunicid. Hisig (5) expresses the opinion that
in Histriobdella we have to do with a strongly modified and
degenerate animal, and not with an Archiannelid.

Though I have not been able to trace a closer affinity
between the Histriobdellide and any other group of the
Annulata, I have come to the conclusion that to class them
as nearly related to Protodrilus and Polygordius is
altogether unjustifiable. Of the common features which
Foettinger adduces as affording evidence in support of his
view, nearly all are general annulate characteristics. To the
alleged primitive condition of the nervous system no weight
can be attached, since, as I have shown above, this condition
scarcely obtains in Stratiodrilus; and since, as has been
pointed out by various observers, it is a condition which is
by no means confined to the Archiannelida, but which occurs
also in various Cheetopoda that do not, in other respects,
present any primitive features.1 To the purely negative
feature of the absence of sete, also, it is impossible to attri-
bute much importance.

In both the Polygordiide and Histriobdellidz the
body is segmented ; but the nature of the metamerism differs
greatly in the two cases. In the former group the segments
are numerous; they are not very sharply defined externally,
but internally their cavities are separated by transverse par-
titions or mesenteries. In the Histriobdellide the segments
are few in number: they are defined externally by constric-
tions, and, in the case of Stratiodrilus, by the occurrence of
the paired appendages ; but only one intersegmental partition,

1 See Mensch, 21.

326 WILLIAM A. HASWELL.

and that an imperfect one, is developed, namely, that at the
commencement of the tail region.

In both familes a head is present, and is clearly marked
off from the rest. Its composition, however, does not in any
way correspond in the two cases. In the Polygordiide it
consists, as in most Cheetopods, of a prostomium lodging the
brain, and of a peristomium, on the ventral surface of which
the mouth opens. In the Histriobdellide it is undivided,
and the mouth opens far forwards, near its anterior extre-
mity in front of the brain. ‘The presence on the head of the
remarkable retractile anterior limbs is highly characteristic
of the Histriobdellide, as is also the presence further back
of the retractile claspers in the male. The highly developed
posterior limbs with their glands are also special structures.

One of the most characteristic features of the structure of
the Histriobdellide is the presence of the elaborate jaw
apparatus, which is not represented in the Polygordiide,
though the muscular sac appended to the cesophagus in the
members of the latter family may correspond to the sac in
which the jaws are lodged in the Histriobdellide.

A. blood-vascular system is fairly well developed in the
Polygordiide, but is not present in the Histriobdellide.
The nervous system is much more highly developed in the
latter than in the former, and the ventral nerve-cord takes
the form of a chain of ganglia metamerically arranged,
whereas in the Polygordiide there is no trace of ganglia.

The reproductive organs of the Polygordiide are of a
generalised character, and are constructed on the same
general plan as those of the Polycheta. In the Histriobdel-
lidee they are highly specialised. On the whole it appears to
me that the relationship between the Histriobdellide and the
Polygordiide is extremely remote, and not such as to justify
their inclusion in the same class.

A comparison with Dinophilus reveals certain common
features not shared with the Polygordiide. In both Dino-
philus and the Histriobdellide the animal consists of a dis-
tinct head, and a trunk consisting of a small number of

ON A NEW HISTRIOBDELLID. 327

seoments. In Dinophilus there is sometimes (D. meta-
meroides) an undivided post-anal or tail region, beset with
small adhesive papille, with glands serving as organs of
attachment. In both groups the ventral nervous system
consists of metamerically arranged ganglia, though in
Dinophilus there are two separate chains connected by trans-
verse commissures (at least in Schimkewitsch’s species) into
a ladder-like structure (25). Dinophilus wants the tentacles
and cirri; possesses bands or a cavity of cilia, and a pair of
eyes. In some species the metameric condition of the
nephridial system is more pronounced than in the Histriob-
dellidae, in others less so ; there is an extension forwards into
the head. In Schimkewitsch’s species there are metameric-
ally arranged bundles of annular muscular fibres, and a pair
of ventral longitudinal muscles. In the alimentary canal
there is a close resemblance between the two groups, though
the horny jaws are absent in Dinophilus. Though Dino-
philus possesses a mesoderm, segmented in the larval condi-
tion, developed from primitive mesoderm cells, its general
body-cavity has no epithelial lining, and the equivalent of
the ccelom is reduced to the cavity of the reproductive
organs. In the reproductive organs there is a considerable
similarity between the two groups, especially in respect of
the male apparatus with its median penis and associated
hypodermic mode of impregnation, and the paired vesicule
seminales.

On the whole I consider that there is more reason for
including Dinophilus and the Histriobdellidz in one class
than for grouping either of them with the Polygordiide.

It is obviously of radical importance in connection with
this question to determine if those features of the Histriob-
dellidee which seem to be of a primitive nature can be
explained as a result of degeneration. If the Histriob-
dellide are degenerate they must be degenerate Cheetopods,
or, at all events, degenerate achetous Annelids. If we are
to take this view, we must at the same time acknowledge
that, side by side with the supposed degeneration, there must

VoL, 43, PART 2.—NEW SERIKS, Z

328 WILLIAM A. HASWELL.

have gone on a special development in certain directions ;
that, while the definite character of the segmentation became
lost, a special set of locomotor organs with an elaborate
musculature became evolved, the mouth became shifted for-
wards, and complex reproductive organs of a specialised type
were developed. This view appears to me to involve diffi-
culties so great that they render the degeneration theory
extremely improbable, and it seems more in accordance with
the facts of the case to conclude that the Histriobdellide are
really primitive Annulates, and that the rudiments of their
specialised features have been inherited from forms lower in
the scale.

A connection between Dinophilus and the Rotifera has
been insisted on by various writers, notably by Schimke-
witsch (25), who says, “ Ohne Zweifel sind auch einige Ziige
_ vorhanden die Dinophilus mit den Rotatorien verbinden : die
Furchung des Hies, die Anwesenheit des Schwanzanhanges,
der mit dem Fusse der Rotatorien iiberemstimmt, der ge-
schlechtliche Dimorphismus: man muss auch gestehen, dass im
Baue des Nervensystems und der Hautmusculatur der Rota-
torien die Tendenz zur Erwerbung der Metamerie bemerkt
werden Kann; bei Dinophilus aber erstreckt sich diese
Tendenz auch auf das Mesoderm und die Excretionsorgane.
Auch bei den Rotatorien erscheinen, wie bei Dinophilus die
Genitalhéhlen als einzige Homologa des Céloms. . .

“Ks giebt aber auch ausser der Metamerie des Meso-
derms einen fundamentalen Unterschied in der Entwicke-
lung; die Rotatorien besitzen nach den Beobachtungen
Zelinka’s gar Kein Mesoderm, wogegen bei Dinophilus die
mesoepitheliale Anlage vollkommen entwickelt ist... .

“Hs Konnen also die Dinophiliden entweder als oligo-
meren Archianneliden deren Célom sehr spit im Laufe der
Entwickelung erscheint und ginzlich auf die Bildung der
Genitalhéhlen mit ihren seitlichen Anhingen geht angesehen
werden, oder man Kann sie auch als Rotatorien auffassen,
die eine echte metamere mesoepitheliale Anlage, vielleicht
durch das Anwachsen der Genitalanlige, und die metamer
angeordneten Segmentalorgane bekommen haben ” (p. 74).

ON A NEW HISTRIOBDELLID. 329

It will be observed that in order to connect Dinophilus
genetically with the Rotifera we have not only to assume the
development of metamerism, but also the loss of the mastax
and the appearance of the external ciliation.

Let us now consider what assumptions must be made if we
are to regard the Histriobdellide as direct descendants of
the Rotifera. The evolution of an incomplete metamerism
must of course be assumed. But there are indications of
such a tendency not only externally, but in both the muscular
and nervous systems of the Rotifera.

In the general shape the Histriobdellide more nearly
resemble the Gastrotricha than the Rotifera proper—in
the narrow body, in the presence of a distinct head region
having the mouth at its anterior end, and in the foot being
represented by a pair of processes each with its pedal gland,
with the anus situated nearly between them on the dorsal
side. But in Paraseison (23) we have a true Rotifer in
which the trochal disc is not developed, and in which there
is a definitely separated head region, containing the brain
and the mastax, and having the mouth at its anterior end.

The tail region of the Histriobdellidz correspends to the
tail of the Rotifer; the posterior legs of the former to the
“toes” of the latter. The tail of the Rotifer is always
entirely post-anal; but, as shown by T’essin and by Zelinka
(27), its interior is filled at an early stage with endoderm
cells, from which circumstance the latter author comes to the
conclusion that the anus originally opened at the end of the
tail. In the Histriobdellide the terminal position of the
anus was retained.

The resemblance between the glands in the bases of the
posterior legs of the Histriobdellide and the foot glands of
the Rotifers will be obvious. In some cases the latter would
appear to consist of homogeneous masses of protoplasm, not
divided into cells, with scattered nuclei (Plate, 24) ; but in
others (Callidina), as in Stratiodrilus, each is a group of
distinct, apparently dust bearing, cells (Zelinka, 27).

In Paraseison, as already noted, there is a head region

380 WILLIAM A. HASWELL.

closely comparable with that of the Histriobdellide. From
the mouth, situated anteriorly, a long narrow cesophagus
runs back; and contained in a diverticulum of this, given off
close to the mouth, is lodged the mastax.

The various tentacles or papillz tipped with sensory cilia
on the anterior region in the Rotifera are closely comparable
to the tentacles of the Histriobdellidee. Homologues of the
anterior or head legs of the Histriobdellide are not of
general occurrence in the Rotifera. But the groups of
unicellular glands forming a viscid secretion, the ducts of
which, in Paraseison, open at certain definite spots on the
surface of the head, appear to perform a similar function in
connection with locomotion to the glands of the anterior legs
in the Histriobdellide, and may be homologous to them.
And still closer come the pair of mobile retractile tentacles
of Floscularia Hoodii, which would appear to be provided
with glands at their bases... Homologues of the cirri of
Stratiodrilus are readily to be found in the processes or
papille tipped with sensory cilia on the body of various
Rotifera.

The nervous system of the Histriobdellide differs from
that of the Rotifera in the presence of the ventral chain of
ganglia, but the discovery by Zelinka (27) of a subcesopha-
geal ganglion in Callidina and Discopus serves to greatly
reduce this difference.

The nephridial system, like the nervous, differs from that
of the Rotifera in partaking (though in this case only toa
slight extent) in the metamerism of the body, and also in the
absence of ciliary flames.

The reproductive system is readily capable of being con-
strued as a direct development from that of the Rotifera.
One of the most striking points of resemblance is the median
penis with the associated mode of impregnation. ‘The rela-

1 T obtain my information on this point from Hudson and Gosse’s ‘ Roti-
fera,’ in which it is stated (p. 55), “ Mr. Hood tells me that both in young

and adult specimens he has seen brown granular matter discharged from their
free ends.”

ON A NEW HISTRIOBDELLID. 331

tions of a pair of nephridia in the genital segment to the
reproductive apparatus is a special development following
upon the establishment of metamerism, such as we could not
expect to see foreshadowed among the Rotifera. The secon-
dary male character of the presence of the claspers seems to
be paralleled in some species of As planchna, in which there
is present only in the males a pair of lateral processes which
seem to have glands at their bases.

If, as the evidence adduced above seems to indicate, the
Histriobdellidee are primitive Annulates which retain certain
Rotiferan features that have become lost or disguised among
higher forms, it becomes necessary to account for Dinophilus
in a similar manner, unless we are to suppose that the annu-
late features of the latter have had an independent origin.
Now Dinophilus, while in most respects distinctly less
advanced than the MHistriobdellide towards the normal
annulate type, has at the same time fewer Rotiferan features,
and is looked upon by most of the zoologists who have paid
special attention to it as directly related to the Turbellaria.
If, however, the evidence in favour of the derivation of the
Histriobdellide from primitive Rotifers is sufficiently strong,
we must look on Dinophilus as having diverged from the
direct line of descent between the two groups, and as having
lost some of the Rotiferan features that in the Histriobdel-
lidee have undergone a further evolution.

The phase of metamerism which the Histriobdellide
exhibit is of great interest. The metamerism of Stratio-
drilus and that of a Chetopod must be acknowledged to be
of the same nature, though the former is less complete in
certain respects. In an animal which, whatever may be the
nature of its food, is of extremely alert and active habits,
great degeneration does not seem to me probable; and yet,
unless we are to look upon the Histriobdellide as degenerate,
it is impossible to avoid the conclusion that in them we have
a metamerism tending in the direction of that of the Annu-
lata, but in an incipient condition. If this be granted, it
carries with it the conclusion that the metamerism of the

332 WILLIAM A. HASWELL.

Annulata did not result from the modification of a chain of
zooids developed by serial budding as supposed by Haeckel,
Hatschek, and others ; but by the dividing up of the body of
an elongate animal into a series of similar parts (Lang,
Meyer, Hisig). In whatever manner the mesoderm bands,
the mesoderm somites, and the resulting secondary meso-
dermal structures may have first originated, whether by
modification of reproductive cells as supposed by H. Meyer,
or by the proliferation of primitive mesodermal elements, it
appears probable that the various organs passed through a
condition of pseudo-metamerism, which became converted into
nascent true metamerism as the ciliary mode of locomotion
became completely given up, and a creeping mode fully
adopted.

LITERATURE.

1. Benepen, P. J. Van.—‘ Note sur une larve d’Annélids,” ete., ‘ Bull.
Acad. Roy. Belg.,’ t. xx.

2. Benepen, P. J. Van.—‘ Histoire naturelle d’un Animal nouveau de-
signé sous le nom d’Histriobdella,’ ‘Bull. Acad. Roy. Belg.’ (2),
tome v.

3. Detace, Yves, and Hérovarp, Epcarp.—‘ Traité de Zoologie Concrete,’
tome v, ‘‘ Les Vermidiens,” 1897.

4. liste, Huco.— Die Capitelliden,’ ‘Fauna u. Flora des Golfes v.
Neapel.’

5. E1ste, Huco.—* Die Entwickelungsgeschichte der Capitelliden,” ‘Mitth.
Z. Stat. Neapel,’ Bd. xiii, 1898.

6. Fa@rtincer, ALEXANDER.—“ Recherches sur l’organisation d@’ Histriob-
della homari, P. J. Van Beneden, rapportée aux Archiannélides,”
‘Arch. Biol.,’ tome v, 1884.

. Frarpont, Jutinn.— Recherches sur le systeme nerveux central et
périphérique des Archiannélides (Protodrilus et Polygordius), et du
Saccocirrus papillocercus,” ‘Arch. Biol.,’ t. v, 1884.

2 |

8. Frateont, JuLteEN.—‘‘ Le genre Polygordius,’ ‘Fauna .u. Flora des
Golfes v. Neapel,’ 1887.

22.

23.

24.

25.

26.

27.

. Lankester, E. Ray.—‘‘ Notes on Embryology and Classification,’

ON A NEW HISTRIOBDELLID. aoe

. Frarvont, Junren.—“ Le rein cephalique du Polygordius,” ‘ Arch.

Biologie,’ t. v, 1884.

. Grarr, Lupwie von.—‘ Monographie der Turbellarien. I. Rhabdoccelida.’
. Hatiez, Paut.—< Contributions & Vhistoire naturelle des Turbellaries.”’

. Harmer, 8. F.—“ Notes on the Anatomy of Dinophilus,” ‘Journ.

2

Marine Biol. Assoc.,’ new series, vol. i.

. HlarscHEeK, BerrHotp.—‘‘ Studien iiber Entwickelungsgeschichte der

Anneliden,” ‘ Arbeiten aus dem Zool. Institut der Universitat Wien,’
Bd. ili, 1878.

. HatscHek, Bertuotp.—‘ Protodrilus Leuckartii,” ‘ Arbeiten aus

dem Zool. Institut der Universitat Wien,’ Bd. iii, 1881.

. HatscHek, Bertuouty.—‘ Lehrbuch der Zoologie,’ Lieferung iii,

1888.

. Hupson, C. T., and Gossz, P. H.—‘The Rotifera or Wheel Ani-

malcules,’ London, 1886; Supplement, 1889.

. Korscurtt.—* Die Guttung Dinophilus,” ‘Zool. Jahrbiicher’ (Spengel),

Bd. 11, 1887.

. Lane, Arnotp.—“‘ Die Polycladen,” ‘Fauna u. Flora des Golfes von

Neapel,’ 1884.

. Lane, ArnoLtp.—“ Der Bau von Gunda segmentata,” ete., ‘ Mitth. Z.

Stat. Neapel,’ Bd. iii.

’

‘Quart. Journ. Mier. Sci.’ (2), vol. xvii.

. Menscu, P. Catvin.—“ The Relation of the Ventral Nerve-cord and

Hypodermis in Procerea,” ‘Zool. Anz.,’ Bd. xxii, 1899.

Meyer, E.—“ Die Abstammung der Anneliden: der Ursprung der
Metamerie und die Bedeutung des Mesoderms,” ‘ Biol. Centralbl.,’
Bd. x, 1891.

Puatre, L.—‘‘ Ueber einige ectoparasitische Rotatorien,” ‘ Mitth. Z.
Stat. Neapel,’ Bd. vii, 1886-7.

Puatse, L.—‘‘ Beitrage zur Naturgeschichte der Rotatorien,” ‘Jen.
Zeitschr.,’ Bd. xix, 1885.

ScHIMKEWITSCH, Wiapimir.—“ Zur Kenntniss des Baues und der Ent-
wickelung des Dinophilus vom Weissen Meere,’’ ‘ Zeitschr. wiss.
Zoologie,’ Bd. lix, 1895.

We pon, W. F. R.—‘On Dinophilus gigas,” ‘Quart. Journ. Mier.
Sci.,’ vol. xxvii, 1887.

Zuuinka, C.—“ Studien uber Raderthiere. ILI. Zur Hntwickelungs-

geschichte der Raderthiere nebst Bemerkungen iiber ihre Anatomie
und Biologie,” ‘ Zeitschr. wiss. Zoologie,’ Bd. liii, 1892.

334. WILLIAM A. HASWELL.

EXPLANATION OF PLATES 14 and 15,

Illustrating Prof. Wiliam A. Haswell’s paper “On a New
Histriobdellid.”

List of Reference Letters.

ac. Accessory glands of male reproductive apparatus. d7. Bridle pieces of
jaws. dr. c. Nerve-cells of brain. 47. f Fibrous matter of brain. ¢. Cirrus,
cel. Clasper. ex, Cisophageal connective. ca. Colom. ca. ep. Celomic
epithelium. Fulcrum of upper jaw. fed. Follicle of large ovum. gi. ed.
Gland of clasper. gz. cd. Ganglion of nerve-cord. gz. ¢. Tentacular
ganglion. gr. gid. Granule glands. in¢. Intestine. j.' Upper jaw. j.?
Lower jaw. /. a. Anterior legs. 7. al. Leg gland. /. p. Posterior leg.
m. Mouth. m. d. Dorsal longitudinal muscles. m. ob. Oblique muscles.
m.v. Ventral longitudinal muscles. zeph. Nephridium. z. 7. Lateral nerve.
od. Oviduct. @s. Gisophagus. ov. Ovary. p. Penis. p.y. Muscular fibres
supposed to act as protractors of jaws. pro. m. Protractor muscles of penis.
r. Ramus of upper jaw. 7. ec. Retractors of clasper. retv, m. Retractor
muscles of penis. 7. y. Retractor muscles of jaws. +. 2. a. Retractors of
anterior legs. s¢. Stomach. sé¢r. m. Striated muscle of jaws. 7.) Median
tentacle. ¢.? 7.3 Lateral tentacles. ¢e. Testis. v. def. Vas deferens. ves.
Vesicula seminalis. v¢. Vitellarium.

Fic. 1.—Entire male of Stratiodrilus tasmanicus. xX 200. The
outline drawn from a living specimen with the aid of camera lucida: nervous
system coloured blue, muscles red, nephridia (including vasa deferentia)
green. ‘I'o avoid too great complication the ganglion situated on the dorsal
side of the penis and the cesophageal connectives have been omitted.

Fic. 2.—Outline of female specimen with the nervous system (coloured
blue).

Fic. 3.—Transverse section of a portion of one of the longitudinal bands
of muscular fibres, the coelomic surface below. x 1500.

Fig. 4.—Jaws with the rami retracted, ventral view. x 800.

Fic. 5.—Jaws with the rami everted, ventral view.

Fic. 6.—Approximately transverse section of head in the brain region.

Fic. 7.—Transverse section of head behind the brain region in the region
of the anterior legs.

Fic. 8.—Longitudinal vertical section of head, approximately median.

Fic. 9.—Transverse section of the second segment, immediately behind
the first pair of cirri.

ON A NEW HISTRIOBDELLID. 335

Fic. 10.—Transverse section of female in the region of the second pair of
cirri.

Fic. 11.—Transverse section of the same series as that represented in Fig.
10, in the region of the anterior paired portions of the ovaries.

Fic. 12.—Section (somewhat oblique) of female specimen in the region of

the posterior unpaired part of the ovary, showing spermatophore; pr. processes
of ovum.

Fre. 13.—Transverse section of caudal region.

Fre. 14,—General view of the male reproductive organs.
Fie. 15.—Ventral view of penis.

Fic. 16.—Lateral view of penis, partly protruded.

Fie. 17.—Ovary. The follicle cells are not represented.

ey

es |

ON SPONGIOPORPHYRIN. 387

On Spongioporphyrin: the Pigment of
Suberites Wilsoni.

By

Cc. A. MacMunn, W.A., Vi.D.

With Plate 16.

I. Spongioporphyrin.

Preliminary.—In July of last year Professor Ray
Lankester sent me a specimen of the Australian sponge,
Suberites Wilsoni, which is coloured a fine purple, with
a request that I would report on its colouring matter. Pro-
fessor Lankester had already named this pigment Spongio-
porphyrin, a name which is most suitable, but which must
not lead to the supposition that the pigment is in any way
related to hematoporphyrin, as I shall show further on.

Accompanying this specimen were also specimens of ano-
ther sponge, viz. the Hexactinellid Polyopogon gigas,
and of a gorgonian coral, both being coloured purple. ‘These
were sent so that | might determine whether their pigments
were related to that of the Suberites.

Mr. Kirkpatrick, assistant in charge of the collection of
sponges at the British Museum, had made at Professor
Lankester’s request some observations on the pigments
both of Suberites and of Polyopogon, which are in-
cluded in this report by Professor Lankester’s wish.

338 CG. A. MACMUNN.

This pigment is characterised by possessing a very well-
marked banded absorption spectrum, and by certain other
characteristics which distinguish it from other pigments
which have been hitherto described.

An inspection of the accompanying plate shows the remark-
able spectra which the various solutions of Spongioporphyrin
present. Looking at sp. 5 or 6, one is reminded of oxy-
hemoglobin, of carminic acid, of turacin, and of antedonin,
etc.; but a closer inspection reveals differences between the
spectrum of Spongioporphyrin and that of any known animal
or vegetabie pigment, and, as will be seen further on, the
wave-length measurements of the absorptive bands of the
solutions of this pigment, and the chemical characters of
these solutions, show that it is a pigment not identical with
any hitherto described.

Acid Solutions of Spongioporphyrin.!—Professor
Lankester had suggested various solvents to Mr. Kirk-
patrick, and among others alcohol acidulated with nitric
acid, and the spectrum of this solution was mapped by the
latter observer correctly, and is shown in sp. 1.

This represents the spectrum of a suitable depth, or suit-
able concentration of solution. In a deeper layer, or in a
more concentrated solution, the absorptive bands coalesce,
and one can see a broad black band occupying the middle of
the spectrum, the red rays and some of the blue being trans-
mitted, while in a deeper layer still, or in a more concentrated
solution, only some of the red rays are transmitted.

All the acid solutions of Spongioporphyrin have a red-
purple colour, while the alkaline solutions have a bluer tinge.
This difference is especially well marked when the solutions
are filtered ; the filtering paper being coloured reddish purple
in the case of the acid solutions, and bluish purple in the case
of the alkaline solutions.

Taking the readings of a suitable depth of a rectified (90
per cent.) spirit solution acidified with a couple of drops of
nitric acid we get,—First band, from A 595 to A 5838, centre

1 Of course all these solutions were filtered.

ON SPONGIOPORPHYRIN. 339

589 ; second band, including shadings, X 577 to A 545, the
darker part extending from X 574 to A 552; the centre of
darkest part being about X 563.

Hydrochloric acid is quite as good a solvent for the pig-
ment as nitric acid, when added in very slight amount to
alcohol or even distilled water, and is really preferable for
many reasons; but alcohol acidulated with sulphuric acid is a
very poor solvent.

A solution of Spongioporphyrin in absolute alcohol acidu-
lated slightly with hydrochloric acid, gave the following
measurements for the absorption bands :—First, A 602 to
r 574, including shadings, dark from X 598 to X 580; second,
A 566 to A 556°5; third, A 548°5 to rA 535.

The bands in an aqueous solution acidulated with hydro-
chloric acid, of which the spectrum is shown in sp. 5 (only
for another depth of solution), read—First band, X 592 to
A 542, dark part A 586 to A 547, centre about A 566; second
band, A 533 to X 514, centre A 524.

The pigment is gradually deposited from an aqueous solu-
tion acidulated with hydrochloric acid, and can be quickly
precipitated out by adding caustic potash solution drop by
drop until the fluid is slightly alkaline. In this way I found
that I could isolate Spongioporphyrin, as will be referred to
below.

Mr. Kirkpatrick found, as I have done, that the pigment
is insoluble in benzol, ether, chloroform, and ammonia, but I
find that distilled water and glycerine take a little up as well
as water to which a little ammonia has been added.

Neutral Solutions of Spongioporphyrin. — The
spectrum of a neutral aqueous solution is shown in sp. 7,
and that of the solid pigment mounted in balsam in 8. That
the very small amount of acid or of alkali required to extract
the pigment must exert some slight influence on the pigment
is Shown by a comparison of the spectra of the alkaline and
acid solutions. Compare, for instance, sp. 5 and 6 with 3
and 4. Of course the alcohol acidulated extracts show a
different spectrum from that of the corresponding acidulated

340 C. A. MACMUNN.

aqueous extracts, as is usually the case,— due, no doubt, to
the different refractive index of the solvent.

An aqueous solution gave the following readings for the
absorption bands :—First, ’ 592 to » 547, dark from A 586
to A 552, centre A 571; second, A 588 to A 516, centre A 527.

If an excess of sulphuric acid, or of hydrochloric or
nitric acid, be added to such a solution, we finally, after
allowing the solution to stand some time, get the spectrum
shown in sp. 9. Certain intermediate changes of spectrum
take place which are not easy to map.

Glycerine, as already said, also extracts some of the pig-
ment from the sponge, forming a violet solution, and giving
two bands :—First, A 586 to » 550, dark from 2X 581°5 to
X 560; second, A 540 to A 518.

Alkaline Solutions of Spongioporphyrin.—Both
caustic potash and caustic soda, added in small quantity to
alcohol or to water, are capable of extracting considerable
quantities of pigment. Ammoniacal alcohol, on the con-
trary, extracts very little; in aqueous solution it extracts
more. But whereas we can precipitate Spongioporphyrin
out of an acid solution, such as that obtained with hydro-
chloric acid, by means of caustic potash, we cannot do so by
adding an acid to the alkaline solution, or at least only toa
limited extent.

If a great excess of caustic alkali be added to a solution
of Spongioporphyrin, obtained by extracting the sponge with
water or alcohol containing a little caustic alkali (and giving
sp. 3 and 4), no further change takes place.

Although the colour of such a solution seems red in deep
layers or in concentrated solutions, yet in thin layers or in
weak solutions it is more of a bluish colour than the acid
solutions, or to be more correct it has a violet colour.

If we take a solution got by digesting some sponge with
water to which a few drops of caustic soda have been added,
and examine a deep layer, we find the red rays between, say,
A 620 and A 700 are transmitted; in a less deep layer the
spectrum is blocked out from about A 615 to X 505, while in a

ON SPONGIOPORPHYRIN. 341

still thinner layer a band from about A 610 to A 515 appears,
and on diluting further or diminishing the layer we get sp.
3, and in a still thinner layer or more dilute solution sp. 4.
An aqueous and caustic potash solution, a few drops only of
the alkali having been used for the extraction, having a fine
deep thick purple colour, gave the following measurements
for the bands :—First including shadings from A 602 to A 552,
dark from A 595 to X 560, centre about A 577; second, Xr 545
to A 522, centre about A 534, A thin layer or a dilute solu-
tion has a beautiful lavender tint.

Although the spectrum obtained by adding an excess of
a mineral acid to a feebly acid solution finally shows the
spectrum of sp. 9, yet there is evidence of the presence of
some intermediate substance which may show five or six
bands. I have not yet investigated this substance or
substances. As stated above, an excess of caustic alkali does —
not seem to produce any change of spectrum. Nitric acid
added to a weak aqueous solution acidulated with hydro-
chloric acid produces the change just mentioned. Sulphuric
acid produces a similar effect.

Is this Pigment Respiratory ?—The addition of
ammonium sulphide to a neutral aqueous solution of
Spongioporphyrin lightens the colour of the solution and
diminishes the intensity of the bands, and on vigorously
shaking with air the bands did seem darker and the colour
deeper. The addition of formol produces no change. The
shght change produced by reducing agents does not enable
one to conclude whether the pigment is respiratory or not.

The Action of Strong Sulphuric Acid.—It was
necessary to find out if strong sulphuric acid produces any-
thing hke hematoporphyrin, when made to act on Spongio-
porphyrin, as it does in the case of turacin.! Accordingly
some pigment isolated as described below was treated with
pure sulphuric acid, and filtered through asbestos. The
filtrate, which was of a purple-red colour and showed a
spectrum closely resembling sp. 5, was poured into water,

1 ¢Philos, Trans.,’ vol, clxxxiii, p, 516.

342 C. A. MACMUNN.

and ammonia added to alkalinity; the precipitate which
formed was separated by filtration and a part digested in
alcohol and ammonia, but this merely showed the ordinary
alkaline spectrum as shown insp. 3. Another part was digested
in alcohol acidulated with sulphuric acid, but this only showed
a spectrum similar to sp. 1. Hence Spongioporphyrin is not
allied to haemoglobin or to hematin.

Isolation of Spongioporphyrin.—After trying various
methods of isolating the pigment, I have come to the con-
clusion that by far the easiest and best method is as follows :
—KExtraction of portion of sponge with distilled water, to
which a little hydrochloric acid has been added, filtering,
precipitating the filtrate with caustic potash to feeble alka-
linity, collecting the precipitate on a Schleicher and Schiill’s
toughened filter-paper, washing on the filter-paper with
abundance of distilled water, collecting precipitate, drying,
and washing with alcohol and ether. The amorphous pre-
cipitate can thus be obtained fairly pure, or it may be further
purified by re-solution and precipitation. So far I cannot
obtain it in crystals, and on incineration on platinum foil it
leaves a little greyish ash. I have not yet been able to get
enough pigment for a series of combustions, nor to determine
more closely its chemical characters, but I find that it is
soluble in distilled water acidulated with hydrochloric acid,
and insoluble in ether, chloroform, benzol, absolute alcohol,
liquorice, distilled water, aqueous solutions containing caustic
potash, and in alcohol containing caustic potash. Like the
pigment as it exists in the sponge, it is soluble slightly in
alcohol acidulated with hydrochloric acid. Solutions of the
isolated pigment give the same spectra as those obtained
from the coloured sponge itself.

II. The Pigment of Polyopogon gigas.

Whereas Spongioporphyrin is very stable, even when
treated with strong mineral acids, the colouring matter of

ON SPONGIOPORPHYRIN. 343

Polyopogon is extremely unstable. This was observed by
Mr. Kirkpatrick, who states in his notes: “ (a) HNO, bleaches
instantly ; (b) KHO turns colour from purple to brick-red ;
(c) KHO and NH, added to a bleached piece of sponge partly
restore colour; (d) the alkaline (KHO) brick-red colouring
matter is bleached by HNO,, and again restored by adding
more KHO; (e) colouring matter insoluble in benzol.”

In contrast to the pigment of Suberites, that of Polyo-
pogon disappears at once when portions of sponge are put
into water acidulated with hydrochloric acid. On putting
portions into water to which a little caustic potash had been
added, the colour changed to brick-red. ‘The sponge itself
has a kind of dull violet-brown colour quite different from that
of Suberites, and in the sponge itself and in its solutions I
could not see any absorption bands.

Both water and glycerine take up some pigment from
Polyopogon. The aqueous solution has a pale violet tint,
and shows no bands. Nor do any appear on treatment with
ammonium sulphide. The same remarks apply to the glyce-
rine extract.

Portions of sponge clarified by means of glycerine and
examined with an Abbé condenser and open diaphragm, and
microspectroscope, show no bands before or after adding
ammonium sulphide.

This pigment may be isolated by taking an acidulated
alcoholic solution, which has a faint yellowish tint, and
shows no bands, and adding a little caustic potash solution.
The almost colourless fluid gets reddish. The precipitate
may then be filtered off and further purified.

If a bit of sponge be taken which has lost its colour under
the influence of alcohol acidulated with hydrochloric acid,
and be washed free from acid and then be placed in water
containing a little caustic potash, the sponge becomes reddish
brown. If now the alkali be washed off, and a little water to
which hydrochloric acid has been added is poured on the bit
of sponge, the latter is again almost decolourised. It has
now, however, a faint greenish tinge. On again washing and

VOL, 43, PART 2.—NEW SERIES, ar

344 Cc. A. MACMUNN.

adding caustic potash solution the reddish-brown colour is
restored.

Weak spirit will not dissolve the pigment, as Moseley
found it did in the case of Polyopogon amadou.

Hence it is quite evident that the pigment is quite dif-
ferent from Spongioporphyrin.

III. The Pigment of a Gorgonian Coral, Pterogorgia pinnata.

Professor Lankester found the pigment of this species
“insoluble,” and truly it is so. I tried all kinds of solvents,
but without result. Alcohol, ether, chloroform, acidulated
water, aqueous alkaline solutions, etc., were all tried in vain.
In the case of the Aleyonarian Heliopora Moseley? found
he could get the pigment out by dissolving the corallum in
hydrochloric acid. I tried all kinds of acids, but with a
negative result. The pigment as it is present in the or-
ganism does not seem affected by acids or by alkalies. I
may mention that the spirit in which this specimen had been
preserved showed a faint chlorophyll spectrum.

From a specimen of the solid pigment mounted in balsam,
which Professor Lankester had prepared, I could see no
definable bands with the microspectroscope, so that one can
infer that this pigment is not related to Spongioporphyrin,
and it is not identical or apparently related to the pigment of
Polyopogon.

Remarks.—On looking up the literature of sponge pig-
ments I cannot find any mention of any pigment which
presents the characters of Spongioporphyrin.

Krakenburg® is the only observer who has made any
extended observations on the pigments of sponges. I
thought at first I was dealing with a “ floridine” when

1 «Quart. Journ. Mier. Sci.,’ vol. xvii, N.S., p. 1.

2 *Vergl. physiol. Vortrage, 1886, iii, and ‘ Vergl. physiol. Stud.,’ 1882,
pp. 22, ete.

3 For chlorophyll, ete., 'n sponges, see ‘Journ. Physiol.,’ vol. ix, No. 1.

ON SPONGIOPORPHYRIN. 3845

examining Spongioporphyrin, but I am now sure that such
is not the case.

On comparing Spongioporphyrin with polyperythrin,
which I have shown reasons for supposing to be hematopor-
phyrin,' with antedonin, which is shown in sp. 10, drawn
from a specimen given me by the late Professor Moseley,
and with, in fact, all the pigments which have been described
up to the present time, I am quite sure we have in Spongio-
porphyrin a pigment which is new to biology.

I hope soon to be able to say something more about the
chemical characters, as well as about the spectro- photometry
of this pigment. In being apparently so easily isolated and
purified, as compared with pigments which are mixed with
fat, or even of a fatty nature, it promises to give interesting
results when submitted to a thorough chemical examination.

EXPLANATION OF PLATE 16,

Illustrating Mr. C. A. MacMunn’s paper “ On Spongiopor-
phyrin: the Pigment of Suberites Wilsoni.”

(The scale attached is one of wave-lengths in 100,000th mm.)

Sp. 1.—Spectrum of a rectified spirit and nitric acid extract of Spongio-
porphyrin.

Sp. 2.—The same; shallower depth or weaker solution.

Se. 3.—An aqueous and caustic soda solution of Spongioporphyrin,

Sp. 4.—The same ; shallower depth or weaker solution.

Sp. 5.—Spongioporphyrin in water acidulated with hydrochloric acid.

Sp. 6.—The same ; shallower depth or weaker solution.

Sp. 7.—Neutral aqueous solution of Spongioporphyrin.

Sp. 8.—Spongioporphyrin in neutral state mounted in Canada balsam.

Sp. 9.—Action of excess of nitric acid on an aqueous solution of Spongio-
porphyrin,

Sp. 10.—Moseley’s antedonin, mounted in balsam. From a Specimen put
up by the late Professor Moseley when on the “ Challenger.”

346 GC. A. MAOMUNN.

POSTSCRIPT.

The Spectrophotometry of Spongioporphyrin.

In this Journal (vol. 40), in his paper “ On the Green Pig-
ment of the Intestinal Wall of Cheetopterus,’ Professor
Lankester has given curves showing the percentages of light
transmitted by solutions of cheetopterin and bonellin. These
curves were drawn by Professor Engelmann, being worked
out by means of his microspectrophotometer. At Professor
Lankester’s request I here give spectrophotometric curves for
feebly alkaline and fully acid spongioporphyrin. I may
briefly describe the instrument by means of which these
curves were obtained. It is constructed on the lines first
proposed by Vierordt,! but with improvements since made
by the brothers Kriiss? and others. It consists of a double
slit, the jaws of which open symmetrically to the optic axis ;
this was made by Mr. A. Hilger, and he has constructed the
screws so well that there is not the slightest ‘ lash,” or any
other defect. The eye-piece is provided with the usual
moveable shutters, and the instrument with a measuring
arrangement; by means of these a slice of the spectrum can
be isolated and measured in wave-lengths. The glass cells
glass body,’ and are 11 mm.
from front to back, the “ glass body” being 10 mm. in the
same direction; thus one can compare a depth of fluid of

are provided with Schulze’s “

1 mm. with one of 11 mm., which is the same as comparing
10 mm. with a depth of nothing. The graduated drumheads
attached to the screws, moving the jaws of the slit, allow

1 «Journ. Physiol.,’ vol. vii, No. 3; vol. viii, No. 6.

* Vierordt, ‘Die Anwendung des Spectralapparates zur Photometrie der
Absorptionsspectren,’ ete., 1873; and ‘ Die Quantitativ Spectralanalyse in
ihrer Anwendung,’ ete., 1876.

3 Kriiss, G. and H., ‘ Kolorimetrie und Quantitatiy Spektral Analyse,’
ete., 1891,

ON SPONGIOPORPHYRIN. 347

one to read off the percentages of unabsorbed light. These
are the percentages which are expressed by the ordinates
of the curves. The abscissz of the curves are wave-lengths
of light, in millionths of a millimetre (uy).

I may now give the data upon which these curves are con-
structed.

[The tables of measurements and the diagrams exhibiting
these results in the form of a curve are printed on the next
two pages (pp. 348, 349), so as to enable the reader to com-
pare them without difficulty. They should be compared with
the similar curves drawn by Professor Engelmann for
chetopterin and bonellin (this Journal, vol. 40). The size
and conditions adopted for the two diagrams of absorption
curves here figured would seem to be well adapted to serve
-asa standard scheme, and it would be desirable to have a
series prepared on this model, illustrating the absorption of
each of the more important substances which present irre-
gular curves of absorption, such as hemoglobin, chlorophyll,
potassium permanganate, nitrous oxide gas, etc.— H. R. L.]

348 C. A. MACMUNN,

ifs

- Feusty ALKALINE SPONGIOPORPHYRIN (a little KHO in
distilled water).

X = wave-lengths in pp (1 = 0:001 p).

A. A weak solution. | B. A stronger solution.
Percentage of unab- Percentage of unab-
a. sorbed light. a. sorbed light.
661 91°2 661 66:2 ?
598 17°4 598 65
578 8'8 578 30
563 12'8 563 5'8
553 22°0 593 8:0
544 20°6 544. 7-0 |
535 240 535 25
523 38'8 523 12:0
498 89°6 498 | 22°6
427 56°4 427 53
|

G.i.
B6s6 = C656 YEE) TTD F486 G430 H4#O0

ON SPONGIOPORPHYRIN. 349

LE.
Frrsty Acip SronciororrHyrin (a little HCl in distilled
water).
X = wave-lengths in pu (1 = 0°001 p).

B. A stronger solution, which had become

A. A weak solution. slightly altered by standing.
Percentage of unab- Percentage of unab-
x. sorbed light. r. sorbed light.

661 80°4 661 42°2
635 76°6 635 36°5 |
589 18°4 589 | 8:2 |
563 3°2 563 3°2
547 66 547 8:2
537 13:0 5387 12:0
520 12'8 520 148 |
498 41°2 498 ea
427 26'8 427 15°7

See Curve II (Fig. 2).
FiG.2.

2686 C656 D589 E526 E486 G430 H40

These numbers express the mean of five readings for each. I may mention
that I have repeated these measurements over and over again for solutions of
the same strength, and I find they agree to within 0°5 per cent. for the middle
of the spectrum, aud to below about 2 per cent. for the red end,

a cw 3S ae 7
ed simon «| HIN Sil 4) pan
a” ae HS 9° ieee” at aeR

= Iara pat UA ay a

1 ne eG ya - a ce

oo!
6» el bed! 7 he Vinge ee
ie ee yr oe 2 Hist : ols egies

oo ae
t
ch Se | tere 0 eee wt
Ast Say ;

REMARKS ON THE DEVELOPMENT OF AMPHIOXUS. 3051

Further Remarks on the Development of
Amphioxus.

By

E. W. MacBride, M.A., D.Sc.(Lond.),
Professor of Zoology in McGill University, Montreal.

With Plate 17.

In 1897 I published in this Journal (6) a paper entitled
“The Karly Development of Amphioxus.” In this work it was
shown—(l1) that the gut wall is all formed by the endoderm,
and that the blastopore is at first posterior and subsequently
displaced on to the dorsal surface; (2) that the mesoderm
originated from five distinct rudiments, viz. (a) an anterior
pouch of the gut, from which the head cavities are formed ;
(b) a pair of dorso-lateral pouches which give rise to the first
pair of myotomes, and to long ventral sac-like outgrowths of
the same which extend back into the atrial ridges; and (c) a
pair of dorso-lateral grooves in the gut wall extending back
to the blastopore, which gradually become separated off in
front, and at the same time divided up to form all the myo-
tomes which succeed the first.

It was further shown, in the paper referred to, that the tube
found in the larva on the left side above the mouth, and
called by Hatschek a nephridium, was the persistent con-
nection existing between the first myotome on the left side
and the gut, from which in the younger larva it had origi-
nated as an outgrowth. Lastly, I asserted that the lymph
canals found in the metapleural folds were the remains of the
ventral extension of the first myotomes.

sue E. W. MACBRIDE,

In the same number of this Journal in which my paper
appeared, Professor Lankester published a criticism (4) of
some points contained in it. He considered that in referring
to a paper by himself and Willey (8) I had given the impres-
sion that they had not deviated from Kowalevsky’s view on
the subject of the development of the atrial cavity ; and that
further, since in my own paper I used the term “atrial fold ”
to denote the wall of the atrial cavity, I had virtually adopted
Kowalevsky’s view on this subject, and overlooked the cor-
rection of this view by Dr. Willey himself, and that in so
doing I was “ perpetuating error.”

Such a strong statement from a zoologist occupying the
position of Professor Lankester could not be passed over in
silence. But various preoccupations, especially those con-
nected with the organisation of the Zoological Department in
McGill University, prevented my undertaking a renewed
examination of my preparations before now. This I have,
however, at last accomplished, and the results of this exami-
nation are given in the present paper. In general it may be
said that these results confirm Kowalevsky’s position as to
the mode of formation of the atrium, but in many details
they support the observations of Lankester and Willey.

Kowalevsky observed (2) in the older larvee of Amphioxus
that two ridges appeared on the ventral surface. Subse-
quently he found underneath the animal a median tube—the
rudiment of the atrial cavity. This tube was situated be-
tween the ridges observed in an earlier state, and these ridges
could still be observed projecting from its walls. These
freely projecting portions could be traced into still older
larvee, and were found to constitute the metapleural folds of
the adult. The canals contained in the folds were stated by
Kowalevsky to be extensions of the general cclom. The
interpretation placed by Kowalevsky on his observations was
that the ridges had met beneath the ventral surface of the
body, and so enclosed the atrial cavity.

Lankester and Willey (3) have made similar observations,
but have interpreted them rather differently. They say the

REMARKS ON THE DEVELOPMENT OF AMPHIOXOS. 353

atrial cavity becomes floored in by ingrowths which meet one
another, arising from the inner sides of the free ridges.
They were not able to trace the lymph canals into continuity
with the ccelom, but state that they appear to be formed by
the hollowing out of the originally solid ridges. The atrial
cavity is at first a narrow tube, which later expands so “as
nearly to surround the alimentary canal.”

When in my first paper I stated that Lankester and Willey
had confirmed most of Kowalevsky’s results, I believed then
and believe still that the difference between the flooring in
of the space existing between two ridges, and the growing
together of the same ridges so as to meet, were practically
only a difference in the form of expression. Kowalevsky
undoubtedly figured the atrial ridges too far from the mid-
ventral line, and does not seem to have observed the first
origin of the cavity, but only a later stage, and the account of
Lankester and Willey is a needed correction of his observa-
tions; but it seems to me rather unreasonable to require a
detailed reference to these minor differences in a paper
mainly devoted to the earlier development of Amphioxus ;
especially when in a later part of the same paper I further
described the views of Lankester and Willey as to the mode
of growth of the atrial cavity, and expressed doubts as to
their accuracy.

Both, however, in the résumé of their observations given
by Lankester and Willey, and in the criticism of my paper
by Professor Lankester, there is a view put forward of the
origin of the atrial cavity which seemed to me most improb-
able, and one main object of the present paper was to test its
accuracy by fresh observations.

In the paper by Lankester and Willey they sum up the
development of the atrium in these words : “ a narrow groove
which closes and sinks (as it were) into the body of the
Amphioxus ;” although they are careful to add that the
mode of formation suggested by Kowalevsky and that de-
scribed by them ‘ ultimately come to the same thing so far
as the obvious morphological relations are concerned.” In

354 E. W. MACBRIDE.

Professor Lankester’s later paper he asserts that he and
Willey showed that there were no atrial folds at all,
since the atrial cavity originated as an insinking formed
between two free edges which were only the metapleura.

A renewed and careful examination of my preparations
has led me to a different conception of the origin of the
atrial cavity. I hold that there are atrial ridges, and that
the first rudiments of these make their appearance long
before the stage in which they were observed by Lankester
and Willey.

In transverse sections of larve of the latest stage to which
they can be artificially reared—that is to say, of larve at the
period of the formation of the mouth—it can be observed that
the section of the body has a very different shape in the
pharyngeal from what it has in the posterior region of the
animal. In specimens preserved in osmic acid it can be seen
that in the pharyngeal region there are two latero-ventral
ridges, sometimes extraordinarily dilated. By carefully
following up the sections it can be seen that the cavities
contained in these ridges are extensions of the cavities of the
first myotome (somite) on each side (fig. 1). This pair of
myotomes was proved by me to have an independent origin
from the alimentary canal, and was compared to the collar
region of Balanoglossus, for which reason its cavity on each
side is termed the collar cavity in this paper. The dilation
of the collar cavities and the consequent extension of the
latero-ventral ridges vary a good deal, and seem to depend
on the amount of fluid contained in them. As we follow the
sections back the collar cavities become more and more
restricted to the latero-ventral angles of the animal, and
between them and the pharynx is interposed on each side the
splanchnoceele, that is the cclomic tube formed by the
coalescence of the ventral portions of the posterior myotomes
(figs. 2 and 3). Our knowledge of the formation of the
splanchnoccele is most unsatisfactory. Kowalevsky’s obser-
vations on this point do not rest on sections. In larve of
the age under discussion, in the anterior region the splanch-

REMARKS ON THE DEVELOPMENT OF AMPHIOXUS. 355

noceele often appears in sections as a solid wedge of cells;
whilst in the posterior region the splanchnoccele is not
completely formed; the ventral portions of the coelomic sacs
are, it is true, nearly shut off from the dorsal portions, but
the coalescence of the ventral divisions to form the splanch-
noceele is not complete. The youngest larve in my collection
caught by the tow-net are too advanced to throw further
light on the subject.

About five or six sections behind the only gill-slit formed
at this stage the collar cavities somewhat abruptly cease, and
the form of the section changes; the ventral ectoderm becomes,
so to speak, moulded on the gut (fig. 3) and the ventro-lateral
ridges disappear. The ventral part of the splanchnoccele can
just be made out as a cord of cells, intervening between gut
and ectoderm.

When later larve are examined, in which several gill-slits
have been formed (figs. 4 and 8), the collar cavities can again
be recognised. Owing to the extraordinary inequality of
growth of the two sides of the pharynx so characteristic of
these larvee, the first gill-slit, which was originally situated in
the mid-ventral line, becomes shifted up on the right side.
In this region the ventro-lateral ridges appear as before on
each side of the gill-slit; they have here, in accordance with
the changed position of the shit, become lateral. Further
back (fig. 8), however, the hinder gill-slits are still in the
middle line, and the ventro-lateral ridges containing the
collar cavities are distinctly seen on each side.

In still later larvee (fig. 5) the ventro-lateral ridges become
still more accentuated. On the right side it can be distinctly
seen that the portion of the collar cavity contained in the
ventro-lateral projection is cut off from the rest. This portion
we may designate as metapleural coelom. A similar cavity
exists on the left side, and has doubtless a similar origin, but
owing to the disturbance caused by the appearance of the
mouth this could not be demonstrated. The greater part of
the ridge which we may now designate as atrial ridge is,
however, caused by a peculiar thickening of the ectoderm

356 E. W. MACBRIDE.

(ect., fig. 5). This is caused, as is shown by fig. 6, by an
enlargement of some of the cells, whose protoplasm becomes
at the same time clear and glassy. These enlarged cells sink
inwards, and are covered by the adjoining unaltered ectoderm
cells. A first trace of this peculiar change can be noted even
in younger larve, such as that shown in fig. 4.

In a later stage (fig. 7) the atrial ridges have coalesced
to floor in the atrial cavity. The metapleural ccelom on each
side is represented by a solid mass of cells, and some of these
cells are already being drawn out transversely. This is an
indication of their approaching modification into the muscles
of the floor of the atrial cavity. A few fibres are already dis-
tinguishable by their refractive power (¢. musc.). In the right
atrial ridge a cavity is seen with indications of nuclei in its
walls. This space I at first supposed to be identical with the
metapleural ccelom of the earlier larva. Lankester and Willey
call it a lymph canal, and suppose it to be derived from the
hollowing out of the ectodermic thickening seen in an earlier
stage. This latter view I now believe to be correct. In the
series from which fig. 7 is taken, one can distinctly see the
metapleural ccelom in the extreme anterior portion of the
right atrial ridge. As one follows the series backwards, the
metapleural coelom changes into a solid plug of cells, and is
pushed to the one side by a mass of watery cells lying under
the external ectoderm, in which further back the cavity
appears. From this observation I have no doubt that
Lankester and Willey are right in assigning to the meta-
pleural canals a “ pseudoceelic ” origin.

The question now is whether the rudimentary atrial cavity
has been formed by an invagination of the ventral ectoderm,
or whether it has been walled in by the farther downgrowth
of the atrial ridges. If figs. 5 and 7 are carefully compared
with one another, it will be seen that the latter view is the
only tenable one. These figures represent sections taken
from corresponding parts of two larve, one with free ridges,
the other with a rudimentary atrial cavity. The lymph canal
in the older larva has been carried further downwards than

REMARKS ON THE DEVELOPMENT OF AMPHIOXUS., 3507

the corresponding ectodermic thickening in the younger
larva by the growth of its base. Had an upgrowth or
invagination taken place, it must have pushed back the
pharyngeal wall, an event which we can see from the figures
has not taken place. The same conclusion will be arrived at
by a comparison with one another of figs. 9 and 10, which
represent sections through the posterior pharyngeal region
of two larve, one with free ridges and one with a rudi-
mentary atrial cavity. One can see that we have to do with
a process of elongation of the walls of the cavity, for parts in
fig. 10, as compared with those in 9, are stretched out.

The further growth of the atrial cavity is described by
Lankester and Willey in terms with which I cannot agree.
They say that the atrium encroaches on the space hitherto
occupied by the ccelom, and finally nearly surrounds the
alimentary canal. I freely admit that this is a view which is
at first sight strongly suggested by an examination of sections
through the region intervening between the end of the
pharynx and the atriopore. It seems to me, however, that
an examination of the relations existing between the atrial
cavity and the gut in the pharyngeal region necessitates a
different view. he point of origin of the atrial wall
isinallstages of development situated at the edge
of the gill-slit. In the larva the gill-slit is a mere pore
situated near the ventral line, and the atrial wall appears to
arise in this stage near the ventral line also. As the animal
assumes the adult form the gill-slit elongates enormously in
a dorso-ventral direction, and the atrial cavity grows in strict
correspondence with this enlargement. The atrial cavity
certainly enlarges, but it does not ‘ displace the ccelom,” or
acquire new relations; its expansion is only a part of the
general expansion of all the ventral structures of the animal.
A comparison with one another of the pharynx of the larva
and adult as to histological structure confirms this view.
We find that the whole of the lateral walls of the pharynx of
the larva have the same structure as the hyperpharyngeal
eroove and adjacent epithelium of the pharynx of the adult,

358 E. W. MACBRIDE.

The rudimentary character of the ventral and lateral walls
of the pharynx of the larva accounts for the apparently
ventral origin of the atrial wall. This wall always arises at
the spot where the flattened epithelium passes into the high
ciliated branchial epithelium.

Since the view of Lankester and Willey has been shown to
be untenable as far as the pharyngeal region is concerned,
it is very unlikely that it is true for the posterior region of
the animal. If we examine a just metamorphosed individual
we find that near the atrial pore the atrial cavity is com-
pletely ventral to the intestine, whilst further forward the
cavity half surrounds it. If, however, we measure the dis-
tance from the mid-dorsal line of the gut to the dorsal
edge of atrial cavity in the two regions, we shall find it about
the same, so that the apparent upgrowth of the atrial cavity
is largely if not entirely accounted for by the increased size
and downward extension of the ventral part of the gut.!

Lankester and Willey state further that their account of
the growth of the atrial cavity ‘‘is readily harmonised with
the existence of the post-atrioporal extension of the atrium
which gradually tapers to a fine cecal canal.” I must say
that I hold on this subject an absolutely contrary view.

In an individual which had just completed the metamor-
phosis there is no trace of this post-atrioporal extension.
In the region of the atriopore we find in such a specimen
four ventral ridges. ‘The two outer are the metapleural ; the
two inner, on the contrary, are the separated walls of the
atrium, here hanging vertically down. In an individual, on
the other hand, in which the genital organs are commencing
to appear, the post-atrioporal connection can be traced back

1 Lankester and Willey give figures in the text of their paper illustrating
the manner in which, according to them, the upgrowth of the atrial cavity
divides the splanchnoceele into the inner or splanchnic and an outer or pleural
portion. I can find in my sections no traces whatever of this outer pleural
portion. Can Lankester and Willey refer to the genital sac? This has of
course been shown to be formed not from the splanchnoceele at all, but from
the myotome,

REMARKS ON THE DEVELOPMENT OF AMPHIOXUS. 309

for a few sections only. It is formed not as a groove at all,
but by the meeting together of the two free atrial walls,
which in younger individuals are well defined, and continued
for some distance backwards behind the atrium. Its mode
of formation is, therefore, strictly comparable to the account
given by me of the manner in which the main portion of the
atrium is formed.

To sum up—

(1) The atrial cavity in Amphioxus is walled in by a pair
of ridges which may be termed atrial ridges, which appear
at a very early period of development as comparatively low,
broad elevations, each of which contains a cavity, which is
an extension of that of the first myotome (collar cavity).

(2) The ectoderm on the external side of these ridges be-
comes thickened, the cells composing the thickening become
clear and glassy, and eventually are hollowed out to form a
“lymph canal.” My former statement as to the ccelomic
nature of this lymph canal is therefore incorrect. The
thickenings containing the lymph canals are called meta-
pleuree.

(3) The extensions of the collar cavities into the atrial
ridges become first separated off as the metapleural ccelom
on each side ; later this coelomic space becomes converted into
a solid mass of cells, from which arise muscular fibres in the
neighbourhood of the gill openings, and almost certainly later
the subatrial muscle. This separation and solidification of
the metapleural ccelom is coincident with an accentuation of
the atrial ridges.

(4) The atrial ridges unite beneath the ventral surface of
the body, and enclose the atrium.

(5) In the larva practically the whole sides and dorsal
portion of the pharynx represent merely the hyperpharyngeal
groove and the adjacent epithelium of the pharynx of the
adult, the whole of the branchial epithelium of the adult being
represented by a very narrow strip of the ventral wall of the
pharynx of the larva. The subsequent disproportionate
growth of this part of the pharynx of the larva and of the

VOL. 43, PART 2.—NEW SERIES. BB

360 E. W. MACBRIDE.

adjacent portion of the atrial cavity has given the impression
that the atrial cavity grew upwards and displaced other
structures, which is not the case.

(6) Whilst Kowalevsky’s main idea as to the manner in
which the atrium is formed is therefore correct, the descrip-
tions given by Lankester and Willey of the structures seen
by them are quite correct, but the consideration of additional
facts renders it impossible to accept their interpretation of
the processes of growth involved.

Before closing this account of the development of Amphi-
oxus I should like to refer to another criticism of my former
paper, and also to some papers on the same subject which
appeared subsequently to its publication. The criticism
referred to is that of Klaatsch (1). In discussing my paper
he remarks (1) that my figures do not awaken much confidence
in the state of preservation of the specimens; (2) that my
position as regards the formation of the mesoderm is governed
by a rash and exaggerated comparison with Balanoglossus.

In reference to Klaatsch’s first remark, I should like to say
that the figures do not satisfy me, and are very far from doing
justice to the preparations. I regret to say that my powers
of draughtsmanship are not first-class, and that the figures
were somewhat hurriedly executed owing to my having to
leave Cambridge for Montreal, and not being able on that
occasion to take my preparations with me. Nevertheless,
imperfect as they are, they give a far better idea of what is
actually seen in well-preserved preparations than the highly
schematic figures of many authors, who represent an epithe-
lium of clearly defined pillar-like cells with a nucleus showing
ineach. It is astonishing how often a first glance at a pre-
paration will give the impression of such a structure, when
more careful examination will only reveal a row of elongated
nuclei, with here and there a cell limit seen. In particular,
in Amphioxus the whole protoplasm both of ectoderm and
endoderm is so loaded with yolk that cell limits are excessively
difficult to make out once the blastula stage has been passed.
I was careful to base my work only on preparations which

REMARKS ON THE DEVELOPMENT OF AMPHIOXUS. 361

gave evidence of thorough preservation ; and in such of my
material as was not preserved in osmic acid the limits of the
various cavities could not be made out, since shrinkage of
ectoderm and mesoderm and the swelling of the gut cells had
obliterated them.

With regard to Klaatsch’s second remark, I can only
interpret it as an insinuation that I wilfully distorted facts
in order to make the development of Amphioxus harmonise
with that of Balanoglossus. Such an insinuation I most
emphatically repudiate. It is perfectly true that I have long
regarded the structure of Balanoglossus as likely to give the
best clue to Vertebrate ancestry, and that I was convinced
that a careful examination of the early development of
Amphioxus would reveal agreement in the essential plan of
development of the twotypes. But the mannerin which this
agreement manifested itself was a surprise to me.

I commenced by investigating Hatschek’s nephridium in
the older larva, and I was astounded to find that it was in
continuity both with the alimentary canal and the cavity of
the first myotome. I then, by examining successively younger
stages, traced this connection back to the embryo, and found
there the first myotome on either side was in communication
with the gut cavity when no other myotome opened into the
endoderm. ‘This was seen in all the embryos of this age
which I examined.

I then made the discovery that no other myotome, in the
strict sense of the word, is ever in open communication with
the gut, but that one always finds at the hinder end of the
animal on each side a dorso-lateral groove or evagination of
the gut wall, from which fresh myotomes (somites) were
successively cut off as the animal grew in length. I may
remark that this view of the origin of the bulk of the meso-
derm is not only in accordance with the results of the latest
work on the origin of the mesoderm in Vertebrata, but, as
Mr. Sedgwick was kind enough to inform me, it was in
accordance with the results of his own unpublished observa-
tions on Amphioxus, 3

362 E. W. MACBRIDE.

As far as regards the head cavities, I was able by sections
to confirm Hatschek’s account of the matter, with the trifling
addition that both head cavities originate from a common
evagination of the gut.

So that, whatever view one may hold of the relationship of
Amphioxus and Balanoglossus, the fact remains that in
Amphioxus the mesoderm originates from five rudiments—
(a) the anterior unpaired pouch of the gut; (b) two dorsal
pouches situated far forward, giving rise to the first pair of
myotomes ; and (c) two dorso-lateral evaginations of the gut
wall, which become divided into somites as the animal
increases in length.

Samassa’s paper (7) onthe development of Amphioxus was
published after mine, but the work was carried on simulta-
neously with mine, and in many points I regard his results
as a welcome confirmation of my own. Ib is curious that we
should have been both driven to use the celloidin-paraftin
method as the only possible way of dealing with such
delicate embryos. ‘The points of difference between us which
I may notice concern (1) the segmentation, (2) the gastrula-
tion, and (3) the formation of the mesoderm.

With regard to the first point, I asserted that at the close
of segmentation no difference is observable between the sizes
of the blastomeres at the two poles of the blastula. his con-
clusion was based on sections, but as orientation is impossible
with spherical objects, it is possible that my sections were
horizontal, and I have no doubt that Samassa’s views, based
on an examination of fresh material, are correct.

With regard to the gastrulation, Samassa’s figures are in
many ways similar to mine, but he regards the lip of the
blastopore at which there is a well-marked separation of the
endoderm and ectoderm as dorsal, whereas I regard it as
ventral.

Now the only method of determining which lip is dorsal
and which ventral is by getting hold of a specimen in which
the first trace of the dorsal flattening preparatory to the
formation of the medullary plate is visible. Such a specimen

REMARKS ON THE DEVELOPMENT OF AMPHIOXUS. 363

has been figured by me in fig. 9 of my paper, and it is clearly
seen that the “clear space” referred to by Samassa is in the
ventral lip. Since, further, I have figured a much more
complete set of intermediate stages of the gastrulation than
Samassa, I must hold to the opinion that in this point an
error has been made by that investigator.

As to the mesoderm, Samassa’s observations are obviously
incomplete, no mention is made of the head cavities, and the
whole subject seems to have interested him less than the
subjects of the segmentation and gastrulation. None of his
statements, however, are irreconcilable with my position.

Legros’ paper (5) is unfortunately only known to me
through the abstract of it given by Klaatsch in the ‘ Zoolo-
gisches Centralblatt,’ but the results therein communicated
have awakened the utmost astonishment in me, and prove con-
clusively not only that Legros has never seen the earlier stages
in the development of Amphioxus, but also that he has never
had properly preserved larve at all. I may pass over his
theoretical conclusions in silence, for any conclusions founded
on such erroneous observations are devoid of any value.

Legros states that the pre-oral pit of the larva is an ecto-
dermal ingrowth, and denies that the club-shaped gland has
an outer opening. It will be remembered that the accepted
view of the origin of the pre-oral pit referred it to the left
head cavity of the embryo. NowTI must reiterate this view
in the strongest possible terms. I have seen the pre-oral pit
in the larva about the time of the formation of the mouth as
a closed vesicle, not once or twice, but twenty to thirty times,
—as often, in fact, as I examined a larva of that age. I have
further traced it back until I found it arising as a thickening
of the left side of the head cavity. As to the club-shaped
gland I am entirely of Willey’s opinion that it is a gill-slit.
I have seen its origin again and again as a pouch of the
pharynx, and I have also found its external opening, but to
see this it is necessary to have larvee preserved in osmic acid.

I have only mentioned the club-shaped gland incidentally
in my former paper, for it never occurred to me that the

364. E. W. MACBRIDE.

results of Willey (8), obtained six years before by an exami-
nation of abundant living material, would be questioned on
the grounds of examination of imperfectly preserved and
scanty material: had such a contingency occurred to me I

could have given figures of every stage in the development
of the club-shaped gland.

MonrtTREAL;
December 38rd, 1899.

List oF WORKS REFERRED TO IN THIS PAPER.

1. Kusarscu, H.—Referat iiber “‘The Early Development of Amphioxus,”
‘Zoologisches Centralblatt,’ Jahrg. vi, No. 4/5, 1899.

2. Kowatevsxy, A.—‘‘ Weitere Studien tiber die Entwickelungsgeschichte
des Amphioxus lanceolatus,” ‘Arch. f. mikr. Anat.’ Bd. xiii,
1877.

8. LanxesterR, E., and Wittey, A.—‘‘The Development of the Atrial
Chamber of Amphioxus,” ‘ Quart. Journ. Micr. Sci.,’ vol. xxxi, 1890.

4, Lanxester, E.—‘‘ Note on the Development of the Atrial Chamber of
Amphioxus,” ibid., vol. xl, 1898.

5. Lecros.—‘ Développement de la cavité buccale de lAmphioxus
lanceolatus,” ete., quoted by Klaatsch in ‘ Zoologisches Central-
blatt,’ Jahrg. vi, No. 4/5, 1899.

6. MacBripz, E. W.—*'The Early Development of Amphioxus,” ‘ Quart.
Journ. Mier. Sci.,’ vol. x], 1898.

7, Samassa.—‘‘ Studien tiber den Hinfluss des Dotters auf die Gastrulation
und die Bildung der primaren Kleinblatter der Wirbelthiere N. Am-
phioxus,” ‘Arch. f. Entw. Mech.,’ Bd. vii, Heft 1, 1898.

8. Wittey, A.—‘ The Later Larval Development of Amphioxus,” ‘ Quart,
Journ. Mier. Sci.,’ vol. xxxii, 1891.

REMARKS ON THE DEVELOPMENT OF AMPHIOXUS. 365

EXPLANATION OF PLATE 17,

Illustrating Mr. E. W. MacBride’s paper entitled “ Further
Remarks on the Development of Amphioxus.”

List of Abbreviations employed.

ect. Ectodermal thickening of the atrial ridge. /oxg. musc. Longitudinal
muscles developed from the inner wall of the collar ccelom, and constituting
the first myotome. my. The myotomes derived from the ccelomic groove.
neh. The notochord. sp.c. The spinal cord. ¢. muse. The transverse
muscle-fibres in the floor of the atrial cavity.

The outlines of all the figures are drawn with a camera lucida, but in Figs.
5, 7, 9, aud 10 the details of the histology of the ectoderm and endoderm are
not given.

Fic. 1.—Transverse section through the anterior portion of a larva just
before the formation of the mouth, in order to show the continuity existing
between the first myotome and the collar celom. Magnified 1100 diameters.
(Zeiss, oc. 2; Leitz, immersion 1.

Fic. 2.—Transverse section through the hinder end of the pharyngea
region of another larva of the same age as that from which Fig. 1 is taken.
The splanchnoceele (represented on the right side by a wedge of cells) inter-
poses between the pharynx and the backward extension of the collar coclom.
Magnification as before.

Fic. 3.—Another section from the same series as that to which Fig. 2
belongs, taken a little further back. On the right side the collar ccelom has
disappeared, and the outline of the section has changed in consequence.

Fic. 4.—Transverse section of the pharyngeal region of an older larva, in
which several gill-slits have been formed. The atrial ridges are not as yet
recognisable. Magnification as before.

Fie. 5.—Transverse section of the pharyngeal region of a still older larva,
to show the first appearance of the atrial ridge. The metapleural ccelom has
become separated from the remainder of the collar celom. Magnification 350
diameters. (Zeiss, oc. 2, obj. D.)

Fic. 6.—A small portion of another section from the same series as that to
which Fig. 5 belongs; taken further forward. It illustrates the peculiar
thickening of ectoderm cells on the atrial ridge.

Fic. 7.—Transverse section of the pharyngeal region of a larva in which
the atrial ridges have just met, ‘so as to form a floor for the atrial cavity.
Magnification 350 diameters. The metapleural ccelom has become solid, and

366 E. W. MACBRIDE.

is giving rise to the subatrial muscle. The ectodermic thickening is hollowed
out to form a lymph-space.

Fig. 8.—Transverse section through the posterior part of the pharyngeal
region of the same larva as that from which Fig. 4 was taken. Magnification
1100 diameters.

Fic. 9.—Transverse section through the posterior pharyngeal region of a
larva, with numerous gill-slits, older than that figured in Fig. 5, but younger
than the larva represented in Fig. 7. The atrial ridges are well marked.
Magnification 350 diameters.

Fic. 10.—A section from the same series as that figured in Fig. 7, through
the posterior pharyngeal region of the larva. The atrial cavity is formed.
The metapleural ceelom has become solid, and in each atrial ridge there is a
lymph-space.

QUELQUES OBSERVATIONS SUR LES ONYCHOPHORES. 367

Quelques Observations sur les Onychophores
(Peripatus) de la Collection du Musée Britan-
nique.

Par

M. E. L. Bouvier,
Professeur au Muséum d’histoire naturelle de Paris.

M. te ProresseuR Ray LanKesteR ayant eu Vaimable obli-
geance de soumettre 4 mon examen les Onychophores du
Musée Britannique, je crois utile de résumer briévement les
principaux résultats auxquels m’a conduit l’étude de cette
riche collection.

A.—Relativement aux espéces américaines, qui appartien-
nent toutes au genre Peripatus, ces résultats sont les sui-
vants:

1. Le P. dominic Poll., le P. trinidadensis Sedg., et
le P. Imthurmi Scl., sont des espéces fort voisines, mais
certainement bien distinctes les unes des autres.

2. Le P. juliformis Guild. différe du P. Edwardsi
Blanch., avec lequel on l’a confondu, parses papilles principales
qui sont de deux sortes, par le nombre de ses pattes et, pro-
bablement aussi, par le nombre des papilles sexuelles du mile ;
cette espéce habite Vile de St. Vincent, mais elle est re-
présentée a la Jamaique par une variété intéressante et,
dautre part, se rapproche beaucoup du P. dominice.

3. Dans Vile de la Jamaique se trouve également une
espece des plus remarquables, le P. jamaicensis Gr. et Cook,
qui ressemble au P. torquatus par ses pattes fort nombreuses,
mais qui se distingue de tous les Peripatus américains par
Virrégularité de ses plis et par ’uniformité de ses papilles.

4, Les Péripates caraibes sont représentés dans la région de
Amazone par une espéce nouvelle de grande taille, le P.
brasiliensis, dont les plis fort réguliers sont dépourvus
des bifurcations segmentaires normales. -

368 M. E. L. BOUVIER.

d. Une autre espéce nouvelle, le P. Lankesteri, appar-
tient au groupe des Péripates andicoles; elle se rapproche de
beaucoup d’espéces non américaines par la présence d’une
papille sur la face dorsale du pied, mais elle offre en outre,
comme les autres espéces andicoles, deux papilles pédieuses
en avant et deux en arriere.

6. La Nereis viridis d’ Adams n’est rien autre chose que
le P. Brdlemanni Bouy.

7. Les embryons de presque toutes les espéces américaines
présentent des papilles principales de deux sortes, des
grandes et des petites, méme chez les formes ou les papilles
principales de l’adulte sont subégales. Ce caractére rend fort
difficile la détermination des jeunes; il semble prouver que
les espéces & papilles principales de deux sortes sont plus
primitives que les autres.

B.—Les espéces australiennes (genre Peripatoides) ne
m’ont par offert une moisson de renseignements aussi riche;
pourtant j’ai pu constater que les ¢ de P. Leuckarti Siang.,
var. orientalis Fl. présentent une papille sexuelle sur toutes
les pattes, depuis la seconde paire jusqu’a la quatorzieme
inclusivement.

C.—Les formesde |’ Afrique australe sont plus intéressantes.
Parmi leurs espéces les plus instructives il y a lieu de signaler
VOpisthopatus cinctipes Purcell, qui est représenté dans
la collection par un certain nombre de jolis exemplaires. Ces
derniers proviennent de Durban, c’est a dire, d’une localité
assez éloignée de Port Elizabeth, région ou furent captures les
types primitifs de l’espéce. II se distinguent de ces derniers
par leur grand orifice sexuel en croix, par les énormes vési-
cules coxales évaginables de leurs pattes (6 a 16 inclus.), par
leurs papilles plus réguliérement sériées et par leur jolie
teinte d’un gris noiratre granité. Ces exemplaires me parais-
sent appartenir a une variété nouvelle de lespéce (var. nata-
lensis) ; d’ailleurs ils ressemblent a |’espéce typique par leur
développement, car j’ai pu observer dans un méme individu,
a ’exemple de M. Purcell, des embryons a divers stades.

Une autre espéce non moins intéressante est le Peri-

QUELQUES OBSERVATIONS SUR LES ONYCHOPHORES. 369

patopsis Moseleyi W. M.; cet Onychophore, en effet,
ressemble aux espéces américaines par des variations considér-
ables dans le nombre de ses pattes ; il peut en compter de 22
a 25 paires et les derniéres, qui sont fort réduites, tantot sont
munies de eriffes, tantot en manquent completement. Malgré
ces variations, tous les spécimens que j’ai observés m’ont paru
fort semblables et je n’ai pu que les ranger dans la méme
espéce. J’ajouterai que M. Purcell semble incliner vers une
opinion analogue, depuis son dernier travail; ce savant m écrit,
en effet, qu’il s’efforce de recueillir des P. Moseleyi vivants
afin de savoir si leurs jeunes présentent des variations sem-
blables dans le nombre des pattes.

Le P. Moseleyi m’a paru se rapprocher étroitement du
P. Sedgwicki Purcell, espéce qui présente 20 paires de
pattes toutes munies de griffes. Pensant que l’étude des
embryons me permettrait peut-étre d’identifier les deux
espéces, j’ai ouvert une femelle pleine de P. Sedgwicki,
mais tous les jeunes qu’elle renfermait dans son utérus
avaient, comme elle, 20 paires de pattes. Cette observation
ne m’a donc par donné les résultats que j’espérais, mais elle
m’en a fourni d’autres, de non moindre importance. J’ai
pu constater, en effet, que les embryons de P. Sedgwicki
ressemblent a ceux des Opisthopatus en ce quwils ne sont
pas tous au méme stade de développement, que leurs pattes
postérieures sont plus développées relativement que celles de
Vadulte, enfin que les plus jeunes présentent sur la téte une
vésicule trophoblastique diversement développée. Par ce
caractére, le Peripatopsis Sedgwicki se rapproche du
Paraperipatus nove-britannie Willey, abstraction
faite des dimensions de le vésicule, qui est plus réduite, et
qui représente vraisemblablement, dans la premiécre de ces
espéces, un organe embryonnaire en voie de disparition. I]
y a lieu de penser qu’on observera des caracteres analogues
dans les embryons de P. Moseleyi.

D.—J’ai pu également examiner les types de Paraperi-
patus nove-britannie offerts par M. Willey au Musée
Britannique. Je n/’airien a ajouter aux savantes observations

370 M. E. L. BOUVIER.

de ce zoologiste, si ce n’est que les pattes de la derniére paire
sont réduites et qu’elles représentent, comme les pattes pos-
térieures des Peripatopsis, des appendices en voie de dis-
parition.

Conclusions.—I] me parait aujourd’hui probable que les
modifications les plus importantes de la morphologie des
Onychophores sontle résultat d’atrophies semblables, plusieurs

Schémas représentant la disparition progressive des pattes postérieures et les
modifications correspondantes de l’extremitié terminale du corps.
A. Peripatus. B. Peripatoides. C. Peripatopsis. D. Paraperipatus.

fois répétées, qui ont réduit et fixé le nombre des pattes. Dans
les Peripatus (toutes les formes américaines sauf une du
Chili; P. Tholloni Bouv., du Congo, et P. sumatranus
Horst, de Sumatra) le nombre des paires de pattes s’étend de
934,43, et varie dans une méme espéce, l’orifice sexuel se trouve
situé entre les pattes de l’avant-derniére paire, et celles de la
derniére sont toujours plus ou moins réduites, mais pourtant

QUELQUES OBSERVATIONS SUR LES ONYCHOPHORES. 371

armées de griffes. Chez les Peripatoides (espéces d’Aus-
tralie, de l'asmanie, de Nouvelle Zélande, et du Chili) et chez
les Opisthopatus (certaines espéces de |’Afrique australe),
les pattes de la derniére paire sont complétement atrophiées,
et Porifice sexuel reste entre les précédentes (qui sont main-
tenant les derniéres), la partie postérieure du corps se termi-
nant par un cone apode plus ou moins allongé. I] en est encore
de méme chez les Peripatopsis (autres espéces de l’Afrique
australe), mais les pattes postérieures y sont fort réduites, et
placées 4 la base d’un céne anal des plus petits. On observe
dailleurs, dans les espéces du genre, les divers stades de
Vatrophie des pattes postérieures: dans le P. Sedgwicki
Purcell, le P. leonina Purcell, le P. clavigera Purcell, et
le P. Balfouri Sedg., ces pattes sont encore assez fortes et
munies de griffes; elle sont de taille variable et le plus sou-
vent inermes dans le P. Moseleyi W. M., enfin elles se
réduisent 4 un court moignon et perdent toute trace d’arma-
ture terminale dans le P. capensis Gr. Dans le genre
Paraperipatus (Nouvelle-Bretagne), cette patte postérieure
disparait complétement, et lorifice sexuel se trouve en
arriére de celles qui les précédaient et qui sont ici, 4 présent,
les derniéres. D?ailleurs ces pattes disparaitront vraisem-
blablement a leur tour (car elles sont déj& notablement ré-
duites), le céne anal qui porte Vorifice sexuel s’atrophiera
peu a peu, et ainsi se produira une réduction progressive
dans le nombre des appendices. Ce nombre, qui s’éléve
43 paires dans les especes américaines, descend jusqu’a 16
chez certaines formes africaines, et finit méme par s’abaisser
& 14 ou 16 chez les espéces d’Australie et de Nouvelle-
Zélande ; en méme temps qu’il se réduit, ce nombre tend a
devenir de plus en plus fixe pour une méme espéce; il
acquiert méme une fixité absolue dans tous les Onychophores
ou il descend au-dessous de 20.

En se fondant sur ces caractéres et sur quelques autres de
diverses valeurs, on peut grouper et distinguer comme il suit
les cinq genres qui constituent la classe :

ove M. E. L. BOUVIER.

Orifice sexuel entre les pattes de l’avant-
derniére paire; pattes postérieures réduites,
mais normalement conformées. Un récep-
tacle séminal sur chaque branche de l’ovi-
ducte. Embryons a& divers stades de dé-
veloppement et munis d’une formation
placentaire a laquelle ils se rattachent par
un cordon. Plis de la peau généralement
réguliers. Couleur variant du _ brun

Peripatus,

(Guild.) Pocock.

L
{

jaunatre au noir. J

Orifice sexuel) Un réceptacle sé-}
entre les pattes de |
la derniére paire

| minal sur chaque

| branche del’ oviducte;
qui ne sont pas | le développement | Peripatoides,
réduites ; em- | s’effectue tout entier| Pocock.
bryons a divers | a Vintérieur de l’ceuf ;

|

stades de déve-; un cOne anal bien
loppement et dé-
pourvus de pla-
centa. Plis de la

x ° 4
peau tres irre-
guliers. Couleur
fondamentale al-

ee eee

développé.

Pas de réceptacle |
séminal (Purcell) ; le

développement se fait | Opisthopatme
1 us,

lant le plus sou- librement dans Vin- +
Purcell.
vent du vert au

noir, rarement | cOne anal rudimen- |
)

térieur de lutérus;

jaune ou brune. taire.

Orifice sexuel entre les pattes de la der-
niére paire, qui sont fort réduites et ees
inermes; cOne anal rudimentaire. Pas ire
réceptacles séminaux. Les embryons se
développent librement dans lutérus ee Peripatopsis,
ternel et y sont presque toujours au meme | Pocock.
stade; parfois, pourtant, ils sont a des
stades divers et munis d’une ei
Couleur allant le plus souvent du vert au |

noir, Plis de la peau trés irréguliers, J

QUELQUES OBSERVATIONS SUR LES ONYCHOPHORES. 378

Orifice sexuel en arriére des pattes de la}
derniére paire (qui sont réduites, mais nor-
males), sur un cone anal trés développé.
Un réceptacle séminal sur chaque branche
de Voviducte. Hmbryons a divers stades +
de développement et munis d’une grande |
vésicule. Plis dela peau assez irréguliers.
Couleur fondamentale allant du vert au
noir. 5)

Paraperipatus,
Willey.

Je terminerai en disant que par leur couleur et, jusqu’a
un certain point, par le nombre de leurs pattes, les Onycho-
phores découverts par M. Richard Evans, membre de la
Skeat Expedition, dans la presqu’ile malaise, semblent se
rapprocher surtout du genre Peripatus.

Paris;
Le ler Janvier 1900.

ON THE DIPLOCHORDA. B70)

On the Diplochorda.

III. The Early Development and Anatomy of Phoronis
Buskii, MclI.

By
Arthur TT. Masterman, W.A.(Cantab.), D.Sc.(Lond.
amd St. A.),

Lecturer on Zoology in the New Medical School, Edinburgh,
With Plates 18—21.

LITERATURE.

Dr. Dysrur (6) appears to have first published observations
upon the development of Phoronis (P. hippocrepia). The
anatomical part of his paper is principally concerned with
the alimentary and vascular systems, and parts of this will
be referred to later on.

He watched the whole process of oviposition, the passage
of the eggs through the nephridia (the ‘‘ hollow ridge ”’) and
their deposition in the inner space of the lophophore. To
the wall of this ridge they adhere by a glutinous exudation.
“They are voided alternately through each ridge (ne-
phridium) and form a compact white mass, separable only with
considerable difficulty on each side of the space in the con-
cavity of the lophophore, shadowed over by the interlacing
extremities of the inner tentacles.” He states, further, that
the larva “quits the parent nest when about forty-eight
hours old.” He figures three larvee at different stages, the
latest having one pair of tentacles. Both the figures and
description clearly show that he mistook the anal end for the

VOL, 43, PART 2,—-NEW SERIES. GE

376 ARTHUR T. MASTERMAN.

oral, and vice versa. ‘lhe eggs after deposition measured
zéy inch in diameter.

Kowalevski (9) in 1867 published the results of his labours
upon Phoronis at Naples. Some observations upon the
anatomy are followed by an account of the early develop-
ment. He states that fertilisation takes place in the ccelom.
Total cleavage leads to the formation of a hollow sphere,
which invaginates. ‘The mesoderm is formed by delamina-
tion from the ectoderm. The blastopore shifts from a ter-
minal to a ventral position. Further development results
in the formation of the hood over the mouth and the ten-
tacles at the posterior end. Between the latter the anus
breaks through. On becoming set free from the egg
membrane the larva is uniformly clothed with cilia. He
succeeded in definitely identifying the Phoronis larva as
being none other than Actinotrocha, Finally, he was led
to consider that Phoronis had no connection with the
Gephyrea or the Bryozoa. In fact, he doubted the cor-
rectness of placing it amongst the worms, himself inclining
rather towards the Mollusca as its true phylum.

Metschnikoff (13) in 1871 gave an account of early Ac-
tinotrocha larve and their structure in so far as could be
ascertained from external observation. He figures and
describes a free-swimming larva with one pair of tentacles,
and follows this up through stages with two and three pairs
of tentacles. His description of stages later than this do not
concern the present subject.

in 1882, however, in a paper (14) dealing generally with
oastrulation and the origin of the mesoderm in Metazoa,
he follows these processes in Phoronis from the blastula
onwards. He appears to have relied solely upon an exami-
nation of the entire embryos for his results. He shows large
mesenchyme Cells present in the blastoccele cavity before
gastrulation, and smaller ones scattered during this process
in the reduced cavity, more especially in the pre-oral lobe.
In this region they are figured as arranging themselves as a
layer lining the cavity. From these observations he is led

ON THE DIPLOCHORDA. onal

to conclude that the mesoderm of the adult arises from
mesenchyme cells. In this opinion he is supported by
Foettinger (7), who finds what he considers early mesen-
chyme cells (“le premier élément mésodermique”) in as
early a stage as that of eight blastomeres. He followed
the segmentation processes from the earliest condition to
gastrulation. Like Metschnikoff, he relied upon optical
sections of the entire embryos, and also subjected them to a
course of treatment with acetic acid.

In 1885 appeared a short paper on the early stages of
Phoronis by Caldwell (3). This observer was the first to
apply the method of sections to the elucidation of the subject
in hand. His paper is almost entirely concerned with the
origin of the mesoblast. Briefly, he dismisses Kowalevski’s
statements by supposing that he was deceived by the ecto-
derm cells being darker at the base, and those of Metschni-
koff and Foettinger by explaining their ‘ mesenchymatous”
cells as being “‘amceboid processes of the endoderm cells
growing into the segmentation cavity,’ or possibly other
non-nucleated bodies which are to be found in the blastoccele.
He concludes, “‘I have observed them frequently, but it is
certain that they have nothing to do with the true meso-
blast.”

His papers and figures have been introduced into numerous
text-books, and are well known, so that we need merely
repeat here his summary (p. 25).

1. The blastopore gives rise to both mouth and anus.

2. The mesoderm arises in an anterior pair of entoblastic
modified diverticula, and in a posterior pair of ectoblastic
diverticula connected by a few mesodermic cells derived from
the middle of a primitive streak.

3. The nephridial openings to the exterior are parts of the
blastopore.

In 1890 Roule (15) attacked the subject, and formed no
exception to the others in differing remarkably from his
predecessors. His material was derived from Phoronis
sabatieri.

378 ARTHUR 'T. MASTERMAN,

Roule’s paper is unaccompanied by any figures, and is of
the nature of arésumé. He has followed the segmentation
to the stage with thirty-two blastomeres, in which he states
there is no blastoccele. The spherical blastula spreads out
laterally to a discoidal shape, which then invaginates and
hence becomes globular. The blastopore is at one of the
poles of the gastrula, but becomes eccentric by differential
growth. He finds no mesoblast till the mouth and pre-oral
hood over it are established, thus differing from Metschni-
koff and Foettinger, and indeed from Kowalevski. From
this stage onwards he finds primary mesenchymatous cells in
the blastoccele. Later still, the “ mésendoblast” in the
neighbourhood of the anus proliferates to form the initial
“‘mésoblastiques.” The cells of these break up partly into
single cells, which join the mesenchyme already referred to,
and partly form two compact masses which Roule considers
to be the mesoblastic bands (homologous to those of the
trochophore). Roule does not state his methods of investiga-
tion, though it would be difficult to determine with any
certainty the points above described without serial sections
of the embryos.

Lastly, Schultze (16) has quite recently (1897) published a
short paper upon the development of the Phoronis found in
the Black Sea. He found that the blastula became bilateral.
As in the case of Roule and Metschnikoff, he describes the
mouth as formed from the blastopore, the anus being a new
formation. He, like Metschnikoff, finds single mesoderm
cells in the blastoccele of the blastula stage. They arise
from the endoderm, and later become pressed into the pre-
oral lobe and the anal region, eventually arranging them-
selves into somatic and splanchnic layers.

He illustrates this process by figures, but does not in any
way refer to his methods. He attempts to account for
Roule’s and Caldwell’s descriptions as being due to the per-
sonal element and the influence of Hertwig’s ccelom theory.
He also remarks that Caldwell evidently mistook the ventral
invagination which gives rise to the adult body for a pair

ON THE DIPLOCHORDA. 379

of posterior coelomic sacs. This cannot possibly have been
the case, for Caldwell’s embryos were cut in the tentacles of
the parent, and in all-the species of Phoronis whose de-
velopment has been known up till now the larve leave the
parent at the stage with only one pair of tentacles long
before the invagination commences. Apart from this, Cald-
well’s figures, drawn by camera from the sections, scarcely
allow of such an explanation.

Lastly, he refers to my comparison of Phoronis and
Balanoglossus, and objects to it on the score of the dif-
ferent fate of the blastopore in each case.

Reference to this will be made later.

Thus the ontogeny of Phoronis is almost unique in this
respect, that with regard to it there is universal disagree-
ment on such an important point as the development of the
mesoderm.

In a former paper I have investigated the structure of the
late Actinotrocha larva, but was debarred from following
the early stages because neither Phoronis nor the early
Actinotrocha occurs in St. Andrews Bay. The later
larvee appear to be brought by the tide currents from else-
where, probably from the Frith of Forth, in which Dr. Stret-
hill Wright first found the adult.

Although a renewed investigation of the early stages
might furnish fresh proof of the correctness of the view
which was suggested of the natural affinities of Phoronis,
and could hardly reveal anything prohibitive of it, more
especially as the origin of the mesoblast in Tornaria is still
considered as undecided (cf. Spengel and Morgan), it
seemed justifiable to publish at once the facts already found,
such as the five coelomic sacs, and draw the legitimate in-
ferences from them rather than keep back the whole work
for years. Such, however, does not appear to be the opinion
of some, to judge by recent criticism, so that I determined
to attempt an investigation of the early stages in Phoronis
Buskii, although the specimens kindly given me by Pro-
fessor McIntosh were preserved in about 1870, and even

380 ARTHUR T. MASTERMAN.

then more with regard to preservation of the adult than of
the embryo. This author has himself made a few observa-
tions upon the larve and their presence in the tentacles of
the parent (12).

Methods.

The animals themselves were well preserved, probably in
corrosive sublimate followed by spirit, but some little diffi-
culty was experienced in the case of the embryos, so that the
study of them has failed. to elicit all that might have been
expected, especially with regard to the origin of the meso-
derm.

The embryos were cut in series mostly with a thickness of
1:25 to 2 uw, and were then deeply stained with heemalum fol-
lowed by aqueous eosin. A very beautiful differential staining
resulted. Not only were the nuclei sharply defined, but the
stages in development were clearly indicated, all the earlier
stages staining with eosin, and the later stages, especially
after gastrulation, becoming clearer. At the same time the
hypoblast always took a darker eosin stain than the epiblast.
Such a method of staining very thin sections when applied
to suitably fixed embryos of Phoronis kowalevskii could
not fail to settle the vexed question of mesoderm formation
in this species, with regard to which every observer has up
till now disagreed with his predecessors.

Some of the sections were made with paraffin alone, and
others with the celloidin-paraffin method ; the latter were the
more satisfactory, mainly on account of the possibility of
more accurate orientation.

The Karly Development of Phoronis Buskii, Mel.

It appears as far as is known to be a general character of
the Phoronidea to retain the eggs in the lophophore until
the early stages are passed through. In the case of P.
Buskii the same arrangement holds as was noticed by Pro-

ON THE DIPLOCHORDA. 381
fessor McIntosh in his monograph upon the species. The
doubts which have been thrown upon the claims of this form
to specific distinction do not seem to be well founded, as it
has well-marked differences which cannot be explained as
variations. Apart from those which concern the compara-
tive length of the adults, the number of tentacles, and the
differences in pigmentation, it is noteworthy that the size of
the embryos in Phoronis australis is greater than that of
P. Buskii; so much is this the case that it is easy to dis-
tinguish the embryos of each species by their relative size in
a mixture of the two.

In P. Buskii the embryos are found in enormous numbers
in the outer coil of the lophophore. They are all enclosed in
a thin ege-membrane, which is intact in the latest stage found
in the tentacles. Rupture of the egg-membrane would
appear to be synchronous with escape of the larvee from the
lophophore of the parent.

Fig. 59 is a transverse section of the lophophore and sur-
rounding partsof Phoronis Buskii, seen from above. As
is well known, the lophophore is composed of a nearly com-
plete ring of tentacles surrounding the mouth. This ring, at
first nearly circular in those species in which the young
stages are known, is drawn out laterally into an ellipse, and
then the extension on each side is rolled up dorsally (to-
wards the anus) into a spiral.

The inner (oral) surface of all the tentacles presents a
ciliated epithelium of long cells, which probably cause cur-
rents of food and water to pass downwards towards the
mouth. The outer surface of the tentacles has a non-ciliated
epithelium of cubical cells, which are much flatter than the
cells of the inner surface. In Fig. 59 the distribution of the
two layers is shown as seen in a section about halfway up
the lophophore.

Thus the inner coil of the lophophore leads down to the
mouth, whilst the outer coil eventually opens out opposite its
fellow in the median line between mouth and anus. Through
the greater extent of the lophophore the apertures of the

382 ARTHUR T. MASTERMAN.

outer coils upwards are freely open, but in a section at the
very base of the lophophore they are seen to be partially
blocked by a pair of large organs, one on each side (see fig. 61).

These problematical organs have had various functions as-
signed to them. Caldwell (1) claimed for them a sensory
function as indicated by the name “ciliated pit,” and they
have been compared to certain sensory pits in some of the
Gephyrea. McIntosh (12) also observed them in the species
under consideration, and noted that they were simple and
rudimentary in the young individual. He also noted the
presence of mucus in the central cavity of the organs.

Benham (2), working upon Phoronis australis, was led
to doubt their sensory function, and considered them to be
glandular in nature. He remarked that a similar glandular
modification extends as a ridge throughout the lophophore,
lying along the face of the inner series of tentacles. I have
carefully examined these organs, and can confirm the obser-
vations of Benham upon their structure and extent. The
“ciliated pit” itself is really only the involuted terminal
portion of the ridge of ciliated glandular epithelium extend-
ing along the base of the outer coil. Benham has named
the whole organ, including the portion extending through-
out the length of the outer coil, the “lophophoral gland.”
My observations of its structure and relationships in P.
Buskii do not differ sufficiently from his to justify further
figures.

With regard to the functions of this lophophoral gland, I
believe there is sufficient evidence to assume that it secretes
mucus, which, driven up the coil by the cilia, forms an
adherent surface for the eggs and embryos to be carried in
the same direction. Thus these glands would come under
the category of subsidiary reproductive organs, or nida-
mental glands.

The proot for this assertion is partly direct and partly
indirect.

Upon dissecting the lophophore, the mucus lying in the
gland may often be removed as a long band with a great

ON THE DIPLOGHORDA. 383

number of embryos adhering to it. The embryos usually
present a more or less progressive series as regards develop-
ment (fig. 20). This band is also found in Phoronis aus-
tralis.

If we are justified in assuming that the cilia on the inner
surface of the tentacles cause a food- and water-current
downwards, the water must tend to filter between the tenta-
cles into the outer coils, and down them into the median
space, where the current would be reinforced by the water
directed by the epistome out of the imner coil through the
dorsal gap in the tentacles, which I called the branchial
fissure. This current of water would pour outwards between
the two spirals of the lophophore, and over the apertures of the
nephridia and the anus. I have not had any live specimens
of Phoronis, so cannot demonstrate with certainty that these
currents actually exist, but I fail to see any other way of
interpreting the structure of the lophophore. This current
would tend to bear away from the animal both the feces
from the anus and the excretory products from the nephridia,
but in the breeding season the sexual products would in like
manner be carried away from the parent. Whilst this may
or may not be a desirable consummation in the case of the
spermatozoa, further provision would be necessary to retain
the eggs in the lophophore (see figs. 61 and 62). If we
may assume that by a contraction of the base of the lopho-
phore the openings of the nephridia could be approximated
still more to the mouth of the lophophoral gland, the eggs
would come in contact with the mucus immediately upon
extrusion, and adhering thereto must be carried up the outer
coil in the teeth of the down-coming water-current, in which
there would doubtless be spermatozoa from another indi-
vidual, Sheltered in the tentacles of the parent, the egesare
in this situation not only in the best position for fertilisation,
but the continuous stream of water makes the lophophore,
like the branchiz of Lamellibranchs, an ideal ‘nursery ” for
the early stages (see fig. 61).

Again, the fact that the lophophoral glands develop very

384 ARTHUR T. MASTERMAN.

late in life indicates a probable connection with the sexual
function.

These remarks concerning fertilisation are contrary to
the statements of Kowalevski that it takes place inside the
body-cavity, but this does not appear to be the case in
P. Buskii or P. australis. Like Benham, I have failed to
find any mature spermatozoa in the coelom. In lke manner
the eggs are never segmented in the ccelom, whilst the un-
segmented eggs are found in great numbers in the tentacles.
In any case all are agreed that the nephridia act as genital
ducts.

Thus the structure, function, development, and relationship
to surrounding parts of the lophophoral gland indicate alike
that it acts as an accessory gland in connection with repro-
duction with a nidamental function.

Arrived at the apex of the lophophoral spiral the embryos
appear to become detached from the mucus, and are then
carried round the outer coil, probably by the water-current,
which passes not only downwards, but from the apex of the
spiral to the opening of the outer coil. Thus the forward
movement of the embryos to the centre of the coil is reversed,
and they travel round the spiral till they are discharged in
the water-current to the exterior between the two spirals of
the lophophore, dorsally to the lophophoral gland (see figs.
60, 61, and 62).

A suitable section will show the spiral with every stage
of development from the segmented blastula at the apex to
the advanced larvee with three pairs of tentacles in the outer
coil (cf. fig. 59).

We may regard the increase in number of tentacles and
their coiling as being adaptations connected with nutrition
and growth, and these features have been seized upon for
the protection and ‘‘ nursing ” of the young in an analogous
manner to similar phenomena in the Lamellibranchiata. At
the early phyletic stages of the group, when the lophophore
was a ring, it could have afforded little or no protection to the
young ; the lophophoral glands were probably absent, and the

ON THE DIPLOCHORDA. 385

eggs were discharged direct into the water. As the lophophore
commenced to coil the eggs were retained for a longer and
longer portion of the ontogeny in the shelter of the tentacles.
Phoronis australis and Phoronis Buskii form the head
of the series in this as in nearly all other features of anatomy
and physiology. Thus the eggs and young are found in the
tentacles, and as a rule still enveloped in the egg-membrane
till as late as the Actinotrocha stage with three pairs of
tentacles.

Segmentation.

The earliest unsegmented ova are found in the lophophore,
which fact militates against the view that fertilisation and
part of the segmentation is effected in the ccelom of the
parent, as was stated to be the case in the Phoronis
examined by Kowalevski (9). Cori (4) has been led to doubt
this observation, and I have certainly failed to find either in
P. Buskii or P. australis a single ovum undergoing seg-
mentation within the coelom. The ova are perfectly round,
and surrounded by a very delicate and pellucid membrane,
which usually has a small pedicle by which it was attached
to the mucus band (see fig. 20).

The first segmentation results in the formation of two equal
blastomeres, which appear to be almost symmetrical. The
second furrow is at right angles to the first, and results in four
quadrants which now differ shghtly at the two poles. Hach
tapers to one end, so that the whole egg appears to be slightly
pointed and broader at the base (figs. 2 and 3). This condi-
tion is foreshadowed in the two-cell stage, but becomes well
marked here. A view of the base (fig. 4) shows the arrange-
ment in which two opposite blastomeres form a cross-line.
All the eggs of this and the eight-cell stage which I have
seen show this arrangement, though, as in the case of the frog,
there are probably variations, and the point is one to which
little importance need be attached. At the apex the two
furrows form a regular cross. A transverse section of this

386 ARTHUR T. MASTERMAN.

stage shows (fig. 21) that there is a well-defined blastoccelic
cavity, slightly compressed from side to side. Roule (15)
states that the blastoccele does not develop till much later.

The third furrow is at right angles to the first two, and is
almost exactly equatorial, The fact that the first four
blastomeres taper results in the upper four being less in bulk
than the lower (fig. 5). The base and apex of this stage
appear similar to those of the four-celled. The further stages
in segmentation are difficult to trace in the specimens to hand.
The cells of the blastula stage are very nearly if not quite
equal in size. The cells of the lower hemisphere, however,
appear to retain a slightly greater size. Fig. 22 is a median
section through an early blastula, with five upper cells and
four lower cells in the median plane. The blastula is still
perfectly spherical, but in further segmentation both the
blastula and the blastoccele appear elongated in a median
section (fig. 23). In this figure the lower cells are distinctly
larger and rather longer than the upper ones. The elongated
appearance is not due to an elongation in one axis of the
blastula (the horizontal axis), but to a gradual flattening of
the whole blastula in the vertical plane, so that it becomes
disc-shaped (cf. fig. 11). Fig. 24 shows an even later stage
of the blastula, in which there isa great increase of cells, and
the lower cells have become slightly flattened on their outer
surface. This is the commencement of gastrulation. As
segmentation proceeds, the nuclei, which in the four-celled
stage lie at the centre of the cells, gradually move outwards
to the peripheral part, and in fig. 24 come to he almost under
the limiting cell wall.

Gastrulation and the Fate of the Blastopore.

The external appearance of the several stages here dealt
with is shown in figs. 6 to 15. The embryos not having
been observed alive, one can only follow the changes by the
examination of a selected series. The whole process of
gastrulation and closure of the blastopore appears to be

ON 'THE DIPLOCHORDA. 387

extremely rapid if one may judge by the small proportionate
number of embryos to be found at these stages, and the very
small extent of the coils which is occupied by embryos at this
stage. The spherical blastula appears to become more or less
hemispherical by a complete invagination of the lower and
rather larger cells, so that the gastrulation is typically embolic.
Fig. 11 shows the view from below of an embryo in which
the invagination is nearly completed ; fig. 6 is a lateral view
of the same embryo. The blastopore at this stage is large and
circular, with a diameter little less than that of the whole
blastula. In the next stage which I have found (fig. 7) the
embryo has commenced to elongate shghtly in an axis
perpendicular to the principal axis of the blastula, and corre-
sponding very nearly with the long axis of the late larva.
Hence in ventral view (fig. 12) the embryo appears to be oval
in outline, and the blastopore is correspondingly oval. At the
part which we may now distinguish as the posterior end, the
oval blastopore is seen to taper off into a groove which extends
as a furrow very nearly to the posterior border of the embryo.
These appearances certainly lead one to the inference that
the blastopore is closmg up by an approximation of its lips
in the posterior region.

A reference to the lateral view of the same embryo (fig. 7)
shows that the anterior part of the embryo, mainly in front
of the blastopore, is increasing in size rapidly, and is tending
to bend over ventrally.

At the next stage (fig. 18) this increase of the anterior
region has caused the outline of the embryo as seen from
below to apparently taper at the posterior end. The blasto-
pore has now further contracted in extent, and narrows off
posteriorly in connection with the median groove, which
has increased in length. In comparing this stage with the
last we note that the anterior lip of the blastopore appears to
be further back than in the latter, which is probably due to
the growth of the anterior region and to its further ventral
flexion (cf. fig. 8). On the other hand, the appearances here
still further confirm the result arrived at above, that the

388 ARTHUR T. MASTERMAN.

blastopore is undergoing a process of closure by an approxi-
mation of the lips in the median line. The closure proceeds
from behind forwards, and the line of closure is indicated by
the faint median groove.

At the next stage the growth, both laterally and ventrally,
of the anterior region has altered the outline of the embryo
(figs. 9 and 14). The blastopore has closed for the greater
part of its extent, and it is now rather broader from side to
side than before. The closure having almost ceased, the
blastopore, or rather its anterior end which is still open,
broadens out and soon after this becomes circular; it is defi-
nitely to be identified as the larval mouth, or more accu-
rately the opening into the “stomach.” The ventral groove
can now be barely distinguished except by careful arrange-
ment of the light, and after this stage is quite indistinguish-
able.

The ventral flexure of the anterior part of the embryo is
very marked (fig. 9), and in the next stage (figs. 10 and 15)
has proceeded so far that the mouth is completely covered over
by this part, now to be identified as the “hood” or pre-oral
lobe.

The period included between these two last stages appears
to be a fairly long one, during which some important internal
differentiations are in progress.

So far as external observation can show, we may notice
that the gastrulation is embolic, the blastopore closes from
behind forwards, its anterior part persisting as the “ mouth.”
We may here anticipate a consideration of the work of
other observers by saying that in no embryo have I been able
to find either in external view or in section any trace of the
“yosterior pit” of Caldwell (8) as a posterior persistent
portion of the blastopore.

Fig. 25 is a median vertical section through fig. 11. In
it the larger granular cells are seen to be invaginating.
Throughout the whole series of sections the histological
characters of the hypoblast are markedly different from those
of the epiblast. Apart from the differences of size and number,

ON THE DIPLOCHORDA. 389

the hypoblast cells contain far more yolk, which stains well
with eosin, the cell walls are much fainter, and are in some
cases indistinguishable (due to method of preservation),
whilst the nuclei are slightly larger and less regularly
arranged.

In fig. 25 the blastoccele cavity is still seen, and it is usually
quite destitute of any structural contents. Occasionally I
have noticed a few fine strands of cytoplasm crossing it, or
even gathered into small masses, but in no case have I seen a
nucleus, or any body which stained with the dark blue tint of
hemalum present in the blastoceele.

Fig. 26 shows a median sagittal section of a stage a very
httle later than fig. 12. Here the invagination is completed,
and the blastopore even in its length has considerably con-
tracted. The epiblast cells are slightly longer and more
abundant at the anterior end than elsewhere. The blasto-
coele cavity is still distinguishable and empty as before. Up
to this stage there is nothing which could be construed into
a trace of mesodermic elements in any part of the embryo.

Fig. 27 is a median sagittal section of the stage represented
by fig. 13 or slightly earlier. Here we may note that the
hypoblast is in close contact with the epiblast in every direc-
tion. Whether due in any degree to a post-mortem contrac-
tion or not, the blastoccele cavity has disappeared altogether.
The blastopore has further narrowed in extent, and the
epiblast at its lips has commenced to grow inwards, following
in the wake of the invaginated hypoblast.

Figs. 29 and 30 are median sagittal sections of figs. 14 and
15 respectively. In them the further formation of the
stomodeum is shown, fig. 30 indicating that the whole
‘qgsophagus” of the larva is formed in this way from
epiblast. The gradual ventral growth of the pre-oral hood
is also clearly shown. One feature to be noted is the entire
absence of any indication in section of the ventral groove.
In transverse sections it appears merely as a superficial
depression of the cells, and it would appear that concrescence
of the respective hypoblast and epiblast of the two lips

390 ARTHUR T. MASTERMAN.

takes place as rapidly as the formation of the groove itself,
so that there cannot (in this species) be found a part in
which these two layers are fused; at least, I have failed to
find a section exhibiting this condition. The ventral
groove would thus appear to be a structure merely indicating
the line of fusion of the blastoporic lips, and not correlated
with an internal line of junction between hypoblast and
epiblast. Fig. 27 shows that internal separation of the two
layers proceeds forwards with the fusion of the blastoporic
lips.

Formation of the Mesoblast.

A determination of the true formation of the mesoblast in
Phoronis was the primary object of this investigation.
Unfortunately, owing to the fact that the material was not
preserved with a view to embryological work, I am not in a
position to demonstrate every detail of the mesoblast forma-
tion in P. Buskii to the extent which I could wish, and I
was tempted to withhold these results till the opportunity of
working out another species with properly prepared material
presented itself ; but as the lesser details may as likely as not
differ in the two species, I propose to give a brief account of
the results to which I have been led by the examination of
sections of P. Busk1ii.

We have already seen that up to the stage depicted in
fig. 12 and in fig. 26 in section, there is no trace of mesoblast
in any part of the embryo.

In fig. 27 the archenteron is seen to be extending into the
anterior part of the embryo, which is at this stage rapidly
growing.

The hypoblast level with this forward extension of the
archenteron bounding it laterally and anteriorly is thinner
than the rest (fig. 27, p.c.), and in places has more nuclei.
Ata slightly later stage, in coronal section, this anterior part
of the archenteron is seen to have still thinner walls, and to
grow backwards as a pair of lateral horns. Its cavity is still

ON THE DIPLOCHORDA. 391

in continuity with the general cavity of the archenteron, but
is connected only by a narrow aperture (fig. 28). At a later
stage (fig. 31) complete separation is effected, and the pre-
oral lobe then contains a cavity separated from the archen-
teron, and lined by low flat cells which have been directly
derived from the hypoblast. The cavity forms the pre-oral
coelom lined by its mesoblast. In fig. 30 the same cavity
is shown with its walls growing back dorsally between
epiblast and hypoblast, and in figs. 35 and 36, trans-
verse sections of the same stage, it can also be recognised
as growing down laterally. The pre-oral body-cavity (or
protoccele) would thus appear to arise directly from the
archenteron, and its mesoblastic walls from the anterior
hypoblast.

At the stage seen in fig. 28 the cells of the hypoblast at
about the middle of the embryo are seen on either side to have
a group of massed nuclei (msc.), whilst here and there a cell-
wall can be seen separating them. In transverse section of
this region (fig. 35) it is seen that the masses are really
ventro-lateral in position, and that the inner surface of the
archenteric cavity is indented just opposite the massed nuclei.
These indentations or grooves correspond in position and
appearance with similar grooves described by Caldwell (8) in
Phoronis Kowalevskii. The cells of the hypoblast sur-
rounding them appear to be segmenting off their inner
ends, and cell divisions proceeding rapidly, a pair of ventro-
lateral masses of mesoblast result. The separation of these
two mesoblastic masses must be effected later than that of
the pre-oral ccelom, and they do not appear at first to con-
tain a cavity. Their future development will be followed ;
they give rise to the collar cavities or the cavities of the
lophophore. In the stage of fig. 28 there is an arrange-
ment of cells at the posterior end of the archenteron much
as seen in the figure (mtc.). After careful search | have not
been able to discover any more definite condition than this.
A little later on, in fig. 51, there can be recognised a pair of
posterior accumulations of nucleated cells, as depicted.

voL. 43, PART 2.—NEW SERIES, DD

392 ARTHUR T. MASTERMAN.

There can be no question that these cells are segmented off
from the hypoblast in this region, and in fact could even be
regarded as being still integral parts of the hypoblast. I
cannot say for certain whether these two masses of cells have
archenteric grooves opposite them or not. It is possible
that this may be the case, and even that they are formed by
two archenteric diverticula which have been disguised by
shrinkage and imperfect preservation. The development of
these posterior mesoblastic masses is later than that of the
collar, for in fig. 32, a section a little ventral to fig. 31, the
collar cavities have expanded to form a median ventral
cavity. The posterior masses still lle in a dorso-lateral
position above the gut, and very little further developed in
the latest stages; there can be little question that they give
rise to the ccelom of the trunk, as found in late Actino-
trocha.

Figs. 34—39 are a selected series of transverse sections
through the stage depicted in fig. 15. Figs. 34 and 35 show
the pre-oral cvelom (pe.) containing its cavity, and giving
off its two lateral horns, These horns proceed backwards
on either side of the mouth, and their terminal portions are
cut across in fig. 37 level with the mouth. Further back, in
fig. 38, the collar mesoblast has fused ventrally, and formed
a spacious collar cavity (mse.) extending up laterally towards
the dorsal surface.

In fig. 89 the posterior tip of the collar ccelom is cut ven-
trally, and the paired masses of trunk ccelom (mtc.) are seen
lying dorso-laterally to the gut. They contain no cavity,
and are small.

Later Development.

Returning to fig. 15, we find that further external differ-
entiation results in (fig. 16) the bifurcation of the posterior
end to form the rudiments of the two first tentacles and a
further growth of the pre-oral hood, Round the edge of this

ON THE DIPLOCHORDA. 393

hood a slight ridge may be traced, and on either side this
ridge passes downwards till it is lost on the surface of the
tentacles. It does not appear to be ciliated, though this may
be due to the inadequate preservation. Lastly, there appears
at the hind end posterior to the two tentacles a single
median protuberance. This is the anal papilla, and its pre-
sence gives the embryo the appearance of bearing at this
stage three tentacles.

Figs. 40 to 45 are selected from a series of transverse
sections through this stage. In fig. 40 may be seen the
large stomodzum which is forming the cesophagus, and is
spreading out laterally to form the atrial grooves. Sur-
rounding the cesophagus and part of the stomach is the
spacious pre-oral ccelom. The stomach still consists of long
granular cells with more or less irregular nuclei. In fig. 41
the atrial grooves are still wider, a mere tip of the pre-oral
ccelom is cut in the hood, and there is no mesoblast present
in the body.

Lower down, however (fig. 42), the two collar elements
(msc.) appear in a ventro-lateral position, and these may be
traced through figs. 43, 44, and 45 as gradually expanding out,
and containing a collar cavity within them. The epiblast in
figs. 44 and 45 can be seen to grow out into the two tentacular
rudiments with great numbers of elongated cells. In fig. 45
the collar mesoblast can be seen to grow out into these
rudiments.

In figs. 44 and 45 the trunk mesoblast (métc.) can be recog-
nised as lying dorsally to the stomach and more or less united
into one mass. The anus does not appear to open at this
stage, nor do any of the ccelomic cavities open to the exte-
rior.

Figs. 17, 18, and 19 illustrate the external appearance of
two later stages. In fig. 17 the first pair of tentacles has
increased in size, and the rudiments of the second have
grown out on either side posterior to the first.

The ridge round the hood can still be noticed, and it now
passes down to the second tentacle on each side, The anal

394. ARTHUR T. MASTERMAN.

papilla has increased in size. The ridge now passes to the
latest developed pair, and has a prominent bay at the spot at
each corner of the hood where the atrial grooves emerge.
The tentacles may be regarded as arising on this ridge one
by one. If the ridge prove in future investigations to be
ciliated, the early Actinotrocha at this stage would have a
single post-oral ciliated band comparable to that of Bipin-
naria, which in later life breaks up like that of this Echino-
derm into a pre oral and a post-oral band.

Under any circumstances the pre-oral band edging the
pre-oral hood, and the post-oral band following the course of
the tentacles, are connected at these early stages by a thick-
ened ridge which probably indicates a phyletic unity. The
common origin of these two bands from one “architroch ”
has been suggested by Lankester (9a).

In fig. 18 the tentacles spread out in such a way as to
hide the anal process altogether, but it may still be recog-
nised by reversing the larva.

Fig. 19 shows a front view of the same stage; the large
bell-shaped pre-oral lobe is conspicuous, and it extends out
laterally beyond the body. This is the latest stage found in
the tentacles of the parent, and it is probable that rupture of
the egg-membrane is effected after its attaimment, the larva
then leaving the lophophore of the parent.

The internal structure of the stage with two pairs of ten-
tacles is intermediate in character between that with one
pair which has been described, and that with three pairs
(figs. 18 and 19). The internal structure of this latter stage
is indicated by the sections shown in figs. 46, 47, 48, and 49,
and by the restoration in fig. 50.

There is little change in the epiblast, except that the central
nerve-ganglion (ng.) can be discerned in figs. 46 and 49 as
a thickening of the epiblastic cells over the esophagus. The
stomodzeum (cesophagus) is now very long and curved round
into the stomach, which is still simple, and does not appear
to have yet given rise to the pleurochords. The hind end of
the alimentary canal is constricted off to form the intestine

ON THE DIPLOCHORDA. 395

(fig. 47), and in most the anus opens to the exterior, though
the aperture is very minute. ‘The intestine seems to be
hypoblastic in origin.

In the mesoblast there are considerable changes. The
mesoblast cells have now formed the thin “ lining-mem-
brane” type of endothelium,—in fact, typical coelomic endo-
thelium, not to be distinguished from the ccelomic endothe-
lium of the free Actinotrocha with six pairs of tentacles.
The several portions of the coelom have come together and
formed typical mesenteries.

The pre-oral ccelom or protoccele does not otherwise differ
in extent from the stage with one pair of tentacles, except
that the two horns have reached back to meet the mesocceles
or collar cavities on either side of the cesophagus, which also
grow forward from their former position to effect the junc-
tion. At the point of junction are formed a right and left
mesentery (fig. 49), but in the middle line dorsally the pro-
toccele and mesoccele do not meet, but leave a hamoccele
space just under the nerve-ganglion (figs. 49 and 46, sns.).
This is the subneural sinus, differing only in size from that
of the later Actinotrocha. Other hemoccele spaces can be
observed, such as that below the cesophagus in fig. 49, but
the extent of these vascular spaces is difficult to trace, and
probably varies to a considerable extent. The mesocceles(msc.)
have extended dorso-laterally round the stomach, to meet
dorsally just on the fore-part of this organ (fig. 47), whilst
they expand widely in a lateral direction, and dorsally at
their posterior part, giving off branches to each tentacle on
either side. In fig. 48, a transverse section at the level of
the post-oral ring of tentacles, the two mesoceeles may be
seen pushing dorsally, their walls forming a pair of con-
spicuous mesenteries with the walls of the metacceles (mtc.).
On either side of the anus and slightly ventral to it the meso-
cceles open to the exterior by a small pore (fig. 47), which is
evidently the mesoccelic pore or collar pore. There can be
little doubt that this is later metamorphosed into the collar
nephridium of the later Actinotrocha, probably by the

396 ARTHUR T. MASTERMAN.

invagination of an epiblastic portion carrying the actual
mesoblastic pores into the interior of the mesoccele.

The metacceles appear to have fused, and to lie asa shallow
(from side to side) coelomic sac dorsal to the stomach and
intestine. ‘They are surrounded in front and on either side
by the mesocceles, and their walls form with them a con-
spicuous pair of dorso-lateral mesenteries (fig. 48), and a
median transverse mesentery (fig. 47).

Fig. 50 is a semi-diagrammatic representation of a half-
larva at this stage, cut in the median sagittal plane. It
serves especially to illustrate the position and inter-relation-
ships of the ccelomic cavities at this stage.

It is clear that very few changes are necessary in order to
change this larva into the free Actinotrocha with five pairs
of tentacles, the structure of which has been described in a
previous paper. In the epiblast the pre-oral sense-organ
and the subneural gland have yet to appear, and possibly a
proctodzum, whereas a pair of protoccelic pores do not seem
to have been yet formed. In the hypoblast the pleurochords
and the partial separation into pharynx and stomach are still
required. ‘The later growth is largely a protuberance of the
anal papilla and the surrounding parts, and with it an
increase in size and extent of the metacceles until they would
meet ventrally to form a ventral mesentery, whilst the peri-
anal band would form later.

Metschnikoff (18) found pelagic Actinotrocha larve
with no more than one pair of tentacles, and traced them up
to the later stages, so that the presence of a proctodeum and
the fuller development of the collar nephridia are among the
few points still requiring elucidation. Metschnikoff’s larve
belong to one of the smaller species at Naples, and it is
important to note that they leave the tentacles of the parent
at a much earlier stage than is the case in Phoronis
Buskii or P. australis.

ON THE DIPLOCHORDA. 397

Comparison with the Work of others.

In comparing these facts with the previous work of others,
one can divide them into two series. The first of these
consists of facts which have been observed by external exami-
nation and connected with the external differentiation of the
embryos, including the phenomena of segmentation, gastru-
lation, and the fate of the blastopore; the second are the
changes undergone by the tissues within the embryo,
especially connected with the phenomena of gastrulation and
the formation and subsequent fate of the mesoblast. With
regard to the first series all observers agree very closely.
Segmentation has in all cases been recognised as being nearly
equal, and gastrulation embolic. The blastopore appears to
survive (in part at least) as the mouth in all the species, but
all do not recognise the fusion of the blastoporic lips pos-
teriorly. Metschnikoff (14) followed and figured the fate of
the blastopore in detail, and he notes that it is at first round,
then becomes reduced in size, and then presents a pointed
oval outline. He also describes a median longitudinal furrow
running backwards from the reduced blastopore to the
posterior end of the embryo. Caldwell (3) followed with
another account, which describes a similar ventral furrow (his
so-called primitive streak), but in addition he finds a posterior
pit, which he regards as the posterior part of the blastopore.
Metschnikofi’s account would be quite as true for Phoronis
Buskii as for his own species. Schultze (16), working upon ~
a species in the Black Sea, finds no trace of this ventral
furrow.

The difference may all be probably accounted for as due
either to defective observation or to specific variability.

Coming to the second series of phenomena a very different
condition prevails. All previous observers with the excep-
tion of Caldwell appear to have relied upon the observations
of entire embryos in optical section, and this method, when
applied for the elucidation of important internal changes, can

398 ARTHUR T. MASTERMAN.

be regarded as neither reliable nor conclusive. Of these
Kowalevski (9) held that the mesoblast arose by delamination
from the hypoblast, and, so far as it goes, this agrees with the
present results.

Metschnikoff (14) described and figured mesenchyme cells
present in the blastoccele cavity at an early stage before
gastrulation, and Foettinger (7) went even further, and claimed
to recognise the mesoblast cells at an even earlier stage.
Caldwell (8), in applying the method of sections to the ques-
tion, failed to corroborate these observations, and attempted
to explain Metschnikoff’s figures on other grounds. He
failed to find any trace of mesoblast till well on in the process
of gastrulation. Roule (15), who followed him, also failed to
detect any mesenchyme cells until the pre-oral lobe and the
mouth were established. As stated above, there are no
figures, and Roule gives no account of his methods. Addi-
tional interest in the question has been roused by a recent
communication of Schultze (16), in which he reasserts the
origin of the mesoblast from mesenchyme cells. At the
present stage of the paper it will be sufficient to note that
he claims to find a mass of mesenchyme cells scattered
throughout the blastoccele cavity at a very early stage before
gastrulation. Again we are led to inquire, what were the
methods pursued? Schultze gives three woodcut figures
which may or may not have been drawn from sections, and
this is all.

Such being the case, special care was taken in this instance
to find out whether there are or are not mesenchyme cells
present in the early stage. The sections were stained very
deeply with eosin and hemalum, and the nuclei were depicted
with remarkable clearness. In the great number of embryos
I have examined I have failed to find a single nucleus in the
blastoccele cavity till after gastrulation. The most one ever
finds are a few cytoplasmic strands and fragments, which are
stained with eosin alone, and show no trace of nuclei. In all
the stages up to the spherical blastula all the nuclei which
are present are arranged symmetrically in the ectoderm cells

ON THE DIPLOCHORDA. 399

as in the figures. The blastula is simply a single-layered
sphere with each nucleus in its place, enclosing a spacious
blastoccele space. In this respect Phoronis Buskii ap-
pears to resemble the species examined by Caldwell (P.
Kowalevskii).!

The results of Kowalevski (9) and Roule (15) are in accord-
ance with what an exact observer would see of the develop-
ment of mesoblast in Phoronis Buskii by an examina-
tion of transparent embryos. Roule probably observed the
anterior mesoblast cells after their origin from hypoblast,
and the posterior masses (metacceles) which he called meso-
blastic bands.

In the case of Foettinger (7) his figures and remarks upon
them would lead us to suppose that the bodies he describes
are neither cells nor nuclei, and do not give rise to the meso-
blast; whilst the entire absence of mesenchyme at early stages
in sections as shown by Caldwell, and confirmed by myself
above, cast grave doubt upon the results of Metschnikoff and
Schultze. It seems more natural to make an appeal to the
evidence of sections in a case of this kind.

With regard, however, to the actual development of the
mesoblast from the hypoblast there are considerable discre-
pancies between Caldwell and myself. He describes and
figures a pair of “modified archenteric diverticula,” which
are evidently identical with the rudiments of the
collar celom as described above. From them he derived
the pre-oral ccelom. In this I am inclined to think he was
misled by the growth backwards of the two horns of the
pre-oral ccelom, which he figured in precisely the same posi-
tion as above in fig. 37. The lateral masses of mesoblast,
instead of growing forwards as he stated to form the pre-oral
coclom, grow backwards and ventralwards to give rise to the
collar or tentacular ccelom.

1 IT am indebted to Mr. A. E. Shipley, of Christ?s College, Cambridge, for
kindly sending me some original drawings of the earliest stages of P.
Kowalevskii, which appear to resemble closely the similar stages as given
in this paper.—A. T. M.

400 ARTHUR T. MASTERMAN.

The rest of the ccelom he derived mainly from a pair of
posterior pouches which arose in connection with the
“posterior pit”—a remnant of the posterior part of the
blastopore. Schultze emphatically denies the existence of
these posterior pouches, and in this, as far as P. Buskii
goes, I can corroborate him. Many weeks’ search amongst
hundreds of embryos whole and in section has failed to bring
to light a single structure bearing the slightest resemblance
to either the posterior pit or the posterior coelomic pouches.
Schultze (16) suggests that Caldwell was misled by the
ventral invagination which gives rise to the adult trunk, but
this cannot be the case, as this organ does not appear till
long after the larve have left the parent.

Caldwell (3) figures these appearances not only in P.
Kowalevskii but in P. australis as well, and although I
have failed to find them in the latter I merely state the fact,
and defer further consideration till I am able to examine the
other species with fresh material.

Comparison with Development of Balanoglossus.

In the first of this series of papers on the Diplochorda
the structure of the late stage of Actinotrocha was com-
pared in some detail with that of Balanoglossus. The
facts above recorded of the early development serve to
emphasise this comparison. There are at present known
at least two types of development in the Enteropneusta, the
direct development of Balanoglossus Kowalevskii (?)
known to us through the work of Bateson (la), and the so-
called indirect development with Tornaria larva. ‘The
early stages of this indirect development do not appear to
be known, though one would expect to find the development
of Phoronis with its free-swimming larva Actinotrocha
conform more closely to this type. However, taking Bate-
son’s type for comparison we find that the stages of seg-
mentation are identical. In both cases there is total seg-
mentation with very slightly pronounced inequality in the

ON THE DIPLOCHORDA. 401

blastomeres, or, in other words, subequal segmentation.
Gastrulation is in each case total, and Bateson’s fig. 5
would serve equally well for a stage of Phoronis. The
subsequent behaviour and fate of the blastopore is markedly
different. In Balanoglossus it closes up gradually and
completely, the hypoblast becoming completely separated
from the epiblast. Subsequently the anus opens at about
the same spot, as far as can be judged, as that at which the
blastopore closed, and the mouth appears ventrally as a new
structure. In the case of Tornaria the young stages do
not appear to have been followed prior to Goette’s larva. In
Phoronis it is certain that the mouth is a persistent an-
terior portion of the blastopore, and it is pretty clear that
the anus opens subsequently at the posterior closed portion
of the blastopore.

Schultze (16) emphasises the different fate of the blasto-
pore in criticising my comparison of Balanoglossus and
Phoronis. Those who accept the view that the blastopore
becomes phyletically both the mouth and anus of the
Colomata will not regard the fact that it persists in a
special ontogeny as mouth or anus, or both, or neither, as
having any bearing upon the question; but for those who
hold other views one may recall the behaviour of the blasto-
pore in other groups. In the Echinodermata the blasto-
pore usually becomes the anus, but does not survive as mouth
or anus in Antedon, nor in Asterina. Again, within the
group of Gastropod Mollusca the blastopore becomes the
mouth in Patella (Patten), Chiton (Kowalevski), and
Nassa (Bobretsky), whilst it survives as the anus in Palu-
dina (Lankester) and numerous others.

In the face of such examples as this we can hardly attach
phyletic relationship or otherwise to a comparison of the
behaviour of the blastopore. In Chiton the blastopore
would appear to migrate from a terminal position, where the
anus opens later, to the position where it survives as the
mouth. In this, as in Balanoglossus Kowalevskii, it is
possible to follow this migration owing to the fact that there

402 ARTHUR T. MASTERMAN.

is present in each case a ring of cilia. Such a migration
would be very hard to follow, except by direct observation
of a developing embryo, in such a type as Phoronis. The
larva of Balanoglossus Kowalevskii differs from Tor-
naria in developing the perianal band very early alone,
whereas the latter develops this band after the post-oral
band. In this respect Actinotrocha resembles the free-
swimming Tornaria, as the perianal band has not ap-
peared in P. Buskii even in the larva with three pairs of
tentacles.

I hope to show later elsewhere that in Tornaria and
other larve, such as those of Echinoderms, the ciliated bands
can be classified by their primary functions into trophic and
motor. Of these the post-oral band of the Hchinoderms,
Tornaria, and Actinotrocha is trophic, whereas the peri-
anal band of Tornaria, Actinotrocha, and the circular
bands of Auricularia and Antedon are motor. Thus in
Tornaria and Actinotrocha, with free larval life at a
very early stage, the trophic bands are essential, whilst the
perianal motor band is added in due course. In the de-
mersal type of Balanoglossus Kowalevskii the mouth
and anus are closed till late; no pelagic food is required, and
the post-oral band does not appear, whereas the perianal band
is developed early for the locomotion of the larva. The same
considerations apply to Antedon and pupal Auricularia.

After closure of the blastopore the next essential com-
parison is in the development of the mesoblast. In Pho-
ronis, as we have already seen, there has been a great
difference of opinion upon this point. The following facts
appear to be indicated.

1. The mesoblast arises from five separate parts of the
archenteric hypoblast, of which one is pre-oral and unpaired,
and the other four are paired and post-oral.

2. The pre-oral mesoblast is in the form of a portion of
the archenteron which is pinched off from it, the cavity
being part of the archenteric cavity shut off in course of
development.

ON THE DIPLOOHORDA. 403

3. The first pair of post-oral elements (collar-somites) are
formed of masses of cells segmented from the distal ends of
the hypoblast cells which lie opposite to slight depressions
in the archenteric walls. These cells at first have no cavity.

4, The second pair of post-oral elements (trunk-somites)
arise at the anal extremity in a similar way to the former, but
they may consist of invaginations of hypoblast in which there
are two walls in close contact. Under any circumstances
these mesoblastic elements come to lie between hypoblast and
epiblast as paired masses with no cavity.

As regards 1, there is an identity in type with Balano-
glossus.

2. The development of the pre-oral coelom in Tornaria
does not appear to have been followed except in the case of
Goette’s larva, in which it is indicated as in course of inva-
gination from the gut. Morgan (14a), however, has thrown
doubt upon this interpretation. In any case the pre-oral
ccelom arises much earlier in Tornaria than the rest of the
mesoblast, and this agrees exactly with Phoronis, as has
been shown above.

In the case of the demersal larva of Bateson (1a) the data
are definite, and the pre-oral ccelom appears to arise in a
manner precisely similar to that of Phoronis. In both
cases it commences to be separated from the archenteron at
the time when the proboscis on the one hand, and the pre-
oral hood on the other, are commencing to be differentiated
externally. In both cases this ccelomic pouch, after separa-
tion from the archenteron, grows backwards laterally and
dorsally, forming a pair of lateral horns. ‘The pouch of
mesoblast grows backwards, surrounding the gut except on
the ventral surface, but especially forming the hollow horns
lying in a horizontal position, one on each side of the gut”
(Bateson, loc. cit., p. 220).

The only difference appears to lie in the earlier separation
of the coelomic pouch from the archenteron in Phoronis,
and in this feature it resembles 'Tornaria.

3. The development of the collar-somites (mesocceles) in

404, ARTHUR T. MASTERMAN.

Tornaria has been carefully followed by Morgan (14a).
He finds that there is “a process of proliferation of the walls
of the stomach, so that the wall at this point, by division
of its cells, becomes two-layered.” ‘I'he mesoblastic mass,
thus derived, has at first no cavity. The whole process
is precisely similar to that of Phoronis, as described
above.

In the demersal larva Bateson states that the collar meso- |
blast arises by a modified form of archenteric diverticula.
“This pair of cavities is bounded on the inner sides by the
cells forming the wall of the gut, and the external boundary
is made up of a single layer of cells continuous dorsally
and ventrally with the hypoblast.” As a matter of fact,
Bateson’s reasons for regarding them as archenteric diver-
ticula appear to be two. Firstly, there is a connection of
their cavity with that of the archenteron which occurs in
” secondly, he notes that “the middle
mesoblastic tracts in Tornaria are said to be archenteric

“very few larve ;

diverticula.” Under any circumstances the inner walls
would appear to arise from the hypoblast in a similar
manner to the mesoccele in Tornaria, according to Morgan
(14a), and the mode of formation is really a type inter-
mediate between the formation of archenteric diverticula
and delamination. Bateson points out that these meso-
blastic pouches extend principally posterior to their point of
origin, which is also the case in Phoronis.

4, The third pair or trunk somites arise in Tornaria
(Morgan) as a pair of hypoblastic outgrowths, two-walled
from the first, but containing no cavity till after separation
from the hypoblast. In the demersal larva they arise as a
pair of archenteric diverticula. In Phoronis I am unable
to state with certainty that they arise either as hypoblastic
outgrowths actually involving the wall of the archenteron, or
whether they are formed by active division from the distal
ends of archenteric cells, but very probably by one of these
two methods. In this respect Phoronis resembles Tor-
naria rather than the demersal type. Bateson (1a) states

ON THE DIPLOCHORDA. 405

that the wall separating the trunk somites from the archen-
teron is last closed on the dorsal side, and in Phoronis the
trunk somites are dorso-lateral in origin, whilst his section
(fig. 33) shows the collar somites to be ventro-lateral, in this
respect also resembling the homologous structures in Pho-
ronis.

It will thus be seen that the formation and relationships of
the several parts of the mesoblast in Phoronis resemble even
in minute particulars that of Balanoglossus, the resem-
blance in mode of origin being rather closer to Tornaria
than to the demersal type, though in many respects the latter
differs more from Tornaria than from Phoronis.

My comparison of Actinotrocha with Balanoglossus
and Cephadiscus receives very little modification with
further work upon the subject. Professor L. Roule (15a)
has published one or more papers in which he states that he
is unable to find in the Actinotrocha of Phoronis
sabatieri certain structures which I have described in the
Actinotrocha at St. Andrews; perhaps further research
may clear up this difficulty. He corroborates the descrip-
tion given of the chordoid structures in Actinotrocha, but
is inclined to regard this larva as closely allied to the tro-
chophore of the Annelida. My views of the relationship
of the trochophore to Actinotrocha are sufficiently clearly
indicated in a recent paper (10a), but it may be noted here
that Roule makes no reference to the five coelomic cavities
which I have figured and described in Actinotrocha,
though the mesenteries separating them can be seen with a
hand lens in the living or mounted larva!! His paper has no
figures, and his methods are not described. Roule’s account
of the early development of the mesoblast in Phoronis so
differs from mine and from that of others that it is not sur-
prising that there should be a like discrepancy in description
of the later stages.

1 As already noted (‘ Quart. Journ. Micr. Sci.,? August, 1897), they were

correctly figured by R. Wagener as early as 1847, but were supposed by him
to be nerves,—A. I’. M.

406 ARTHUR T. MASTERMAN.

Structure of Lophophore and Coloration.

The anatomy of Phoronis Buskii and that of Pho-
ronis australis, a closely allied species, have been
described by more than one worker, and it is here proposed
merely to add a few fresh observations to the facts already
known.

Coloration.

Preservation in alcohol does not appear to affect to any
extent the black pigment of Phoronis australis. The
arrangement of this is somewhat peculiar. The lophophore
or crown of tentacles is banded. Figs. 51 and 52 are dorsal
views of the entire animal (natural size). The tentacles
appear to be black throughout the greater part of their
length, except for a light unpigmented area extending hori-
zontally across each coil at about three fifths of the distance
towards the base. Another narrower band is found at the
base of the lophophore, under which les the nerve-cord.
Fig. 54 is a ventral view of another specimen, in which the
white band on the tentacles is seen to extend down to the
base of the lophophore, thus meeting the lower band.

There is, however, considerable variation in the colora-
tion, though these three illustrate the general rule. Fig. 54
shows an abnormal specimen, in which the whole lophophore
is inky black, with no bands.

The trunk is pigmented for a very variable extent of its
length, as is seen by figs. 51—54, in which a dotted line
indicates the transition from the pigmented to the unpig-
mented areas. It is possible that the unpigmented portion
is that part which during life was embedded in the skeletal
tube of Cerianthus, which also appears to be dark in
colour. All the pigment is deposited as minute black
granules in the cells of the ectoderm, but whilst the pigment
in the trunk is uniformly distributed in the cells, that in
the lophophore is confined to the ectoderm of the cubical
type, which is found only on one side of the tentacles,

ON THE DIPLOCHORDA. 407

Ectoderm.

The ectoderm covering the trunk is corrugated (fig. 55)
into circular ridges, which have been supposed to be due to
contraction caused by spirit. An inspection of the figure
would lead one to doubt this, as the reduplications appear to
he very regular, and the thin cuticle runs from tip to tip of the
corrugations instead of following the course of the corruga-
tions. The cells are elongated and have elongated nuclei.
On the left hand the presence of black pigment spots is
indicated. At the base of the ectoderm cells is seen the fine
plexus of nerve-fibres which is very characteristic of Pho-
ronis as of Balanoglossus. Below this again is the
chondroid tissue.

At the junction of collar and trunk the nerve-plexus be-
comes hypertrophied into a massive post-oral ring of nerve-
cells and nerve-fibres (fig. 56). The inner ends of the
ectoderm cells can be traced in some cases into nerve-cells,
and in others into nerve-fibres. The nerve-cells rather tend
to accumulate close under the chonaroid tissue, but every
transition stage can be selected from the densely crowded
long ectoderm cells to the nerve-cell removed from the
surface. Fig. 57 shows some of the transition stages ; they
indicate how intimately the nervous system still is bound up
with the ectoderm in this group.

The ectoderm of the collar or lophophore is of two types,
which I have elsewhere described as branchial and atrial
epithelium respectively.

From other work upon the alimentary processes of Hchino-
derm and other larve I have been led to more generalised
names for these types of ectodermal epithelium. A great
number of facts seem to point to the supposition that the
method of food ingestion, by the activity of ciliated areas
causing currents of water, which in their turn carry micro-
scopic food particles, is the primitive method for the early
Metazoa from the gastrula stage onwards. This method of
food ingestion may be termed cilio-trophic, and is found

VoL. 43, PART 2.—NEW SERIES. KE

408 ARTHUR T. MASTERMAN.

very generally in the lower types of Metazoa, especially
sedentary types in which the cilia, no longer motor, are
entirely trophic in function. The first important differen-
tiation in cilio-trophic alimentation is the separation and
retention of food particles and the removal of the water-
current. The active areas which are trophic have a charac-
teristic form of epithelium which may be termed tropho-
phoral, and the areas along which the return water-current
is removed have another type of epithelium which may be
termed hydrophoral. Trophophoral epithelium is made up
of densely crowded elongated cells, covered with active cilia,
and very commonly having glandular cells added to them.
Hydrophoral epithelium has flat or cubical cells, usually non-
ciliated or with few cilia, and often pigmented or even
actively excretory.

For the separation of the food particles from the water-
current at least two important general methods are resorted
to. The first is the principle of filtration, in which water is
allowed to pass through certain apertures and food retained,
or vice versa; and the second is by an entanglement of
the food particles in mucus strands which allow the water-
currents to pass in other directions, whilst they themselves
are conveyed into the alimentary canal.

The first system is probably the most primitive, and in
almost every case the second is superadded to it. I have
attempted elsewhere (10b) to show that a great number of
the characteristic organs of the Chordata, including noto-
chord, hypochorda, pharyngeal clefts, thyroid gland, and
hypophysis, may be traced to an origin which they subserved
in either one or other of these methods of food ingestion,
and the matter will be further dealt with later.

In Phoronis both methods are exemplified very perfectly.
In the case of water-filtration it is evident that the greater
the surface of contact which is effected between the tropho-
phoral areas and the hydrophoral areas, the greater will be
the efficiency of the filtration attained. The simplest rela-
tionships obtain in the larve of Echinoderms in which the

ON THE DIPLOCHORDA. 4.09

whole body-surface is divided into trophophoral and hydro-
phoral areas, and the pinne or “arms” and processes may
be all, as I hope to show later, accounted for as contributing
to the efficiency of filtration. In Actinotrocha the line of
contact between the two areas is at first multiplied by a
simple row of tentacles, throughout the length of which the
line of contact passes (cf. figs. 59—62).

After fixation the young Phoronis is provided in like
manner with a simple row of tentacles round the oral aper-
ture, and the subsequent history of the Phoronidea may be
traced as a successful attempt to increase the efficiency of
filtration by a gradual multiplication of the number of ten-
tacles.

The known species may be placed in order from Cori’s (4)
table :

Greatest length Number of ‘Thickness of
in mm. tentacles. tentacles in mm.

Pe eracilis’*. : 10 joe 40 ite 05
P.hippocrepia . 15 tae 60 i —
P. cespitosa : 35 Ab: 70 ve 057
P. psammophila . 50 os 90 ca ‘06
PS Buski : - 52 a. 300 asi —
Po australis . e150 =. ~o00 es. —

From this it will be seen that the increase in size corre-
sponds very closely with the number of the tentacles and
their thickness. Probably the comparative length of the
tentacles follows the same rule. As the tentacles seem
to serve the ingestion of food, the increase of ciliated sur-
face on the one hand, by increase in number, length, and
thickness of the tentacles, and the increase in bulk of the
body, on the other hand, are probably directly connected
with each other.

The tentacles in transverse section show that their inner
or oral surface is covered with trophophoral epithelium and
their outer surface with hydrophoral, and bear a remarkable
structural resemblance to the ctenidia of Lamellibran-

410 ARTHUR T. MASTERMAN.

chiata, the tentacles of numerous sedentary Annelida and
Brachiopoda, Cephalodiscus, and even the branchial
filaments of Tunicata and Amphioxus. These resem-
blances depend upon a similar method of food ingestion, the
cilio-trophic, in each of the groups, and it seems fairly clear
that in each case the branchial function has been only secon-
darily added. In Phoronis not only does this filtration
method hold, but the trophophoral epithelium has glandular
cells distributed in it. As the result of the activity of these
cells fine strands of mucus pass down the oral side of the
tentacles and serve to entangle minute algoid bodies. In
fig, 8 these strands with their contents may be seen passing
along the oral side of the epistome into the cesophagus.

Lastly, the epistome itself is so arranged in relation to the
rest of the lophophore that it acts as an organ to remove the
water from the oral aperture.

Figs. 60, 61, and 62 are intended to illustrate this point.
‘he coils of each half of the lophophore are arranged spirally,
and the tentacles are widely separated from each other for
about their distal two thirds and united together laterally
for the proximal one third. A transverse section of the
lophophore may illustrate the arrangement at different
heights.

Thus in fig. 59 the outermost half-coil shows the tentacles
cut in transverse section, each having the trophophoral
epithelium on its oral surface and filtration spaces between
contiguous tentacles. For the rest of the course of the coil
the deeper parts are cut in which the tentacles are fused to-
gether laterally, so that the tentacular filtration method no
longer acts at this depth. But not very far up, at the
beginning of the second coil in the figure, the epistome may
be seen in transverse section projecting across the floor
of the oral aperture for a little over a coil in length.
After this the section is too deep to cut the epistome
completely with its ectodermal epithelium, but its ccelomic
cavity can be seen in transverse section up to the very tip
of the spiral. Benham (1) criticises Allman’s description

ON ''HE DIPLOCHORDA. 411

of the epistome, and remarks that Allman’s figure “ conveys
quite a wrong idea of the organ.” The same remark
would be equally applicable to his own. He described
the epistome as extending “right across the oral side of
the animal from right to left,” and figures it in the same
way (fig. 7). As a matter of fact it is continued as a con-
spicuous ridge on either side to the very tip of the spiral,
continuous throughout the three coils of the lophophore. If
the tentacles be regarded as forming the incomplete lateral
walls of a spirally coiled chamber, then the epistome forms
the floor of this chamber except for a fissure between it and
the outer row of tentacles through which the mucus strands
pass down into the cesophagus (fig. 58). This floor descending
from the apex to the base of the spiral must necessarily serve
to prevent access of the greater portion of the water-current
into the cesophagus, and to cause it to flow out in the median
line through the gap in the inner row of tentacles where it
would join the current along the hydrophoral area of the
outer surface of the tentacles.

The figures 60, 61, and 62 should make this clear. In fig.
60 the lophophore is viewed from above, and the epistome
(shaded) is seen projecting over the mouth. The currents
are shown by the arrows descending the coils and passing’
through the tentacular gap to escape over the anal area.

Fig. 61 is a section through fig. 60 at a, showing the course
of the water first separated by the intertentacular filtration,
and further down the course of the water impinging upon the
upper surface of the epistome. In fig. 62, a section through
B, this water is seen to pass out through the tentacular gap,
whilst the mucus strands continue their course down the
cesophagus. The epithelium of the trophophoral area is
indicated by thick lines, that of the hydrophoral by thin.

Conclusion.

My labours upon the Diplochorda (Phoronis and
Cephalodiscus) have now extended over some time. We
may here refer to some of the results.

412 ARTHUR T. MASTERMAN.

The first of these is that Actinotrocha has a pair of
organs which have at least as great a claim to be regarded
as rudimentary chordoid organs allied to the notochord of
the Vertebrates as have the so-called notochord of Balano-
glossus and Cephalodiscus. Roule (15a) has confirmed
the chordoid structure of them, although he differs in other
points.

In 1897 (10) it was pointed out that the chordoid structure
of the gut in Actinotrocha was not confined to the two
diverticula, but was also found in the mid-ventral portion of
the stomach just opposite the sac-like invagination which
later gives rise to the trunk of the adult.!. This alone showed
the need for caution in drawing too close homologies, and
although the hypothesis was made that the two pleurochords
represented the paired rudiments of the single notochord of
the Vertebrates, it was with some reservation.

A study of Balanoglossus itself shows that the chordoid
metamorphosis of the gut epithelium is very wideiy present
in the various parts of the alimentary canal, especially in the
pharynx, in parts of which it extends completely round the
whole pharyngeal wall. This is so easily demonstrated (it is
referred to by Spengel) that it is surprising, firstly, that
the fact is universally ignored in text-books ; and secondly,
that in the face of it the small pre-oral diverticulum alone
should have been selected for comparison with the notochord
of the Vertebrata (cf. Bateson). Considering that the
organ lies pre-orally, its great claim for notochordal recog-
nition must rest in the fact that its cells are metamorphosed
into vacuolated tissue similar to that of the vertebrate
notochord, and the value of this comparison is considerably
lessened when it is considered that the dorsal part of the gut
in the collar region, and even beyond it, is chordoid, and is
in a position relative to the nervous system more closely
resembling that of the vertebrate notochord. The structure

1 This appears to be in the same position as the so-called “ pygochord ’’ of
Willey, occurring in certain species of Enteropneusta—A. T. M., March,
1900.

ON THE DIPLOCHORDA. 413

of Actinotrocha and Bala oglossus points out clearly
that chordoid modification may occur in any part of the
hypoblastic organs. On the other hand, in Cephalo-
discus, and, as I hope to show elsewhere, in ‘ornaria, the
chordoid metamorphosis is restricted to a pair of lateral
grooves along the pharynx, so that we are justified in sup-
posing that this represents the earliest condition of the
Archichorda, and that the Diplochordate condition has
become disguised in adult Balanoglossus by a further
spreading of the chordoid metamorphosis. Hence in
Balanoglossus there does not appear to be any one
organ which can be compared directly to the noto-
chord of the Euchorda.

The phyletic history of an organ appears to consist of the
following steps :

1. The function and structure are co-extensive with the
organism itself, or very early limited to either the endoderm,
ectoderm, or mesoderm.

2. The function becomes concentrated in a certain part
of the primary layer, and the part itself then becomes differ-
entiated structurally from the rest of the layer.

3. The function is so fully defined as apart from that of
the primary layer as a whole, that the organ also becomes
organically separated from the parent layer. In a natural
group it is to be expected that the lower members will
exhibit stages 1 and 2 of organs which are in stage 3 in the
higher.

It has been suggested to divide the Chordata into two
main groups, Archichorda and Euchorda, the former com-
prising Balanoglossus, Cephalodiscus, Phoronis, and
possibly the Echinodermata ; whereas in the latter there are
included the Urochorda, Cephalochorda, and Vertebrata.

The Archichorda are regarded as being the lower
members of the group, and we may inquire, How do they
stand the test of the organismal relationships above referred
to?

In the case of the nervous system, stages 1 and 2 are

4.14 ARTHUR T. MASTERMAN.

prevalent in all the Archichorda, a diffuse nervous plexus
(stage 1) and sundry definite nerve tracts being character-
istic of the group; whilst in the Euchorda the central and
peripheral nervous systems are alike organically separated
from the parent ectoderm.

Applying the same test to the notochord, we find that in
the Archichorda a large and more or less indefinite part of
the endoderm is metamorphosed into chordoid tissue in
accordance with the needs of each particular type. (A cross-
section of the pharynx of Balanoglossus shows this
clearly.) At the same time there are indications of stage 2.
The chordoid tissue becomes definitely located at certain
parts, and these become more or less distinct structurally as
organs (pleurochords) still in organic continuity with the rest
of the endoderm.

In the Euchorda the notochord has completely separated
from the endoderm in the adult.

This method of looking at the matter will show clearly
the relationship of the chordoid organs of the Archichorda
to those of the Kuchorda. It may be possible with further
research to indicate an actual organ among the former which
may be regarded as the direct homologue of the notochord,
but it will probably be in some larval form with an unpaired
dorsal rudiment, not in adult Archichorda.

The same relationships might be pointed out in the meso-
dermic organs. The mesoderm in the Archichorda merely
shows archimeric segmentation, and does not show a com-
plete separation into various organs. In the Huchorda the
mesoderm is not only metamerically segmented, but early
divided up into separate organs, such as nephrotome, myo-
tome, sclerotome, etc.

Lastly, in the case of pharyngeal clefts, I have attempted
to indicate elsewhere (10b) that the origin of these organs
must be sought for in the grooves at the corner of the
mouth which, very early even in the history of the Archi-
chorda, become segmented backwards from the mouth. In
this way I would regard the pharyngeal clefts as originating

ON THE DIPLOCHORDA. 415

primarily from the mouth, the inverse to Dohrn’s hypothesis,
which regards the Vertebrate mouth as a pair of fused
pharyngeal clefts, a view which does not appear to take suffi-
cient account of physiological differentiation.

In part 1 (10) it was shown that Actinotrocha has five
coelomic cavities, with many of the relationships of the five
cavities in Balanoglossus; and they were compared not
only with these, but with the five cavities which appear to be
an integral part of the constitution of a great number of the
lower Coelomata. In this last part of the work the origin of
these cavities is shown to be similar to that of the same
organs in Balanoglossus.

Roule (15a) in a recent paper disagrees with my conclu-
sion on the relationship of Phoronis to the Hemichorda
(so called), and attempts to regard Actinotrocha as a
trochophore. The body-cavity of a trochophore is a
hemocecele, whereas the hemoccele is restricted in Actino-
trocha to small spaces between the ccelomic sacs. Until
Roule is in a position to demonstrate the absence of these
five coelomic sacs one need hardly attach much importance
to his comparisons of Actinotrocha with a trochophore
nor to his refusal to accept my enlignment of the former
with the Enteropneusta.

St. ANDREWs ; March, 1899.

VOL. 430, PART 2.—NEW SERIES. BR

416 ARTHUR TT. MASTERMAN.

REFERENCES.

1. Bennam, W. B.— Quart. Journ. Mier. Sci.,’ July, 1889.

la. Bateson, W.—‘ Quart. Journ. Micr. Sci.,’ vol. xxiv, 1884.

. CatpwELL, W. H.—‘ Proc. Royal Soc.,’ London, xxxiv, 1882-3.
. CALDWELL, W. H.—‘ Quart. Journ. Mier. Sci.,’ vol. xxv, 1885.
. Cort, 1.—“ Inaugural Dissertation,” Prague, 1889.

. Cort, C. J.—‘ Zeitschrift wiss. Zool.,’ Bd. li, 1891.

. Dystrr, F. D.— Trans. Linn. Soc.,’ London, vol. xxii.

. FarringerR, A.—‘ Arch. de Biol.,’ tom. iii, 1882.

. Kowa.evski, A.—‘ Mém. Acad. Impér.,’ St. Petersburg, t. x.
Kowateysk1, A.—‘“‘ Inaug. Dissertation,” St. Petersburg, 1867.
. LanxesTer, EK. R.—‘ Polyzoa,” ‘ Encyclopedia Brit.,’ 1885.
10. Mastermay, A. T.—‘ Quart. Journ. Micr. Sci.,’ vol. xl, 1897.
10a. MastEerMAY, A. 'I.—‘ Proc. Royal Soc.,’ Edinb., June, 1898.
10b. Masterman, A. T.—‘ Report Brit. Assoc.,’ 1898.

11. McIntosu, W. C.—“ Challenger Reports,” vol. Ixxv, 1888.

12. McIntosu, W. C.—‘“‘ Challenger Reports,” vol. xxviii, 1888.
13. Merscunikorr, .—‘ Zeitsch. f. wiss. Zool.,’ Bd. xxi, 1871.

14. Metscunikorr, E.—‘ Zeitsch. f. wiss. Zool.,’ Bd. xxxvii, 1882.
14a. Morean, T. H.—‘ Journ. of Morph.,’ v, 1891.

15. Routz, L.—‘ Comptes Rendus Ac. Sci.,’ Paris, tom. ex, 1890.
15a. Rouse, L.—‘ Comptes Rendus Ac. Sci.,’ Paris, Oct., 1898.
16. Scnutrzz, E.—‘ Imp. Soc. Nat.,’ St. Petersburg, vol. xxviii, pt. 1.

CHONAAT A W LY

xe)
©

ON THE DIPLOCHORDA. 417

EXPLANATION OF PLATES 18—21,

Illustrating Mr. Arthur T. Masterman’s paper “ On the
Diplochorda.”

ABBREVIATIONS.

arch, Archenteron. 4p. Blastopore. dc. Blastoceele. ené. Enteron. m.
Mouth. mse. Mesoceele (collar cavity). mite. Metaccele (trunk cavity). xg.
Nerve ganglion. p. Pre-oral hood. pe. Protoceele. szs. Subneural sinus.
st. Stomodeum. 7, @, /3. Pairs of tentacles.

PLATE 18.

Fic. 1.—Embryo in egg-membrane.

Fie. 2.—Kmbryo with two blastomeres ; side view.
lic. 38.—Embryo with four blastomeres; side view.
Fie. 4.—Embryo with four blastomeres; ventral view.
Fig. 5.—Embryo with eight blastomeres ; side view.
Fics. 6—10.—Lateral views of series of larve.

Fies. 11—15.— Ventral views of series of larve.
Fics. 16—18.—Lateral views of late larve.

Fie. 19.—Ventral view of Fig. 18.

Fie. 20.—Mucus band with embryos.

PLATE 19.
Fic. 21.—Transverse section of Fig. 3.
Fies. 22—24.—Longitudinal sections of embryo later than Fig. 5.
Fie. 25.—Longitudinal sagittal section of Fig. 11.
Fic. 26.—Longitudinal sagittal section of Fig. 12.
Fig. 27.—Longitudinal sagittal section of Fig. 18.
Fie. 28.—Longitudinal coronal section of Fig. 18.
Fic. 29.—Longitudinal sagittal section of Fig. 9.
Fic. 30.—Longitudinal sagittal section of Fig. 10.
Fies. 31, 32.—Lougitudinal coronal sections of Fig. 10.
Fie. 33.—Transverse section of Fig. 10.
Fies. 34—39.—Series of transverse sections of Fig. 16 (early).
Fies. 40—44.—Transverse sections through late stage of Fig. 16.

PLATE 20.
Fie. 45.—Transverse section through larva of Fig. 16.
Fies, 46, 47. Longitudinal sagittal sections through Fig. 18.
Fries. 48, 49.—Transverse sections through Fig. 18.
Fig. 50.—Semi-diagrammatic half-larva at stage of Fig. 18.

418 ARTHUR T. MASTERMAN.

Fies. 51—54.— Lateral views of Phoronis australis, natural size.

Fig. 55.—Longitudinal section through body-wall of trunk region ot
Phoronis Buskii.

Fic. 56.—Transverse section through nerve-ring of P. Buskii.

Fie. 57.—Isolated elements from Fig. 58.

Fie. 58.—Longitudinal section through epistome of P. Buskii.

Fic. 59.—Transverse section of lophophore of P. Buskii.

PLATE 21.

Fic. 60.—Diagram of transverse section through lophophore of P.
buskil, showing currents.

Fic. 61.—Longitudinal sagittal section through lophophore of P. buskii,
showing currents. The section is supposed to pass through A. in fig. 60,
but the coil of end coil in fig. 60 should be twisted a little more, so as to be
cut once more by the line. (Cf. fig. 59.)

Fie. 62.—Median sagittal section through lophophore of P. Buskii,
showing currents. The section is supposed to pass through B. in fig. 60.

i

With Ten Plates, Royal 4to, 5s.
CONTRIBUTIONS TO THE KNOWLEDGE OF RHABDOPLEURA
AND AMPHIOXUS.
By KE. RAY LANKESTER, M.A., LL.D., F.R.S.
London: J. & A. CHURCHILL, 7, Great pe peeuelk Street,

Quarterly Journal of Microscopical

Science.

The SUBSCRIPTION is £2 for the Volume of Four Numbers ;
for this sum (prepaid) the JourNAL is sent Post Free to any part
of the world.

BACK NUMBERS of the Journat, which remain in print, are
now sold at an uniform price of 10/-.

The issue of Supptument Numpers being found inconvenient,
and there being often in the Hditor’s hands an accumulation of
valuable material, it has been decided to publish this Journal at
such intervals as may seem desirable, rather than delay the appear-
ance of Memoirs for a regular quarterly publication.

The title remains unaltered, though more than Four Numbers
may be published in the course of a year.

Hach Number is sold at 10/-, and Four Numbers make up a
Volume.

London : Je & A. CHURCHILL, os Great Sree oes Street.

TO. CORRESPONDENTS.

Authors of original papers published in the Quarterly Journal
of Microscopical Science receive twenty-five copies of their
communication gratis.

All expenses of publication and illustration are paid by the
publishers.

As a rule lithographic plates, and not woodcuts, are used in
illustration.

Drawings for woodcuts should nor be inserted in the MS.,
but sent in a separate envelope to the Editor.

Contributors to this Journal requiring evtra copies of their
communications at their own expense can have them by applying
to the Printers,

Messrs. ApLarD & Son, 224, Bartholomew Close, E.C., on
the following terms :

For every four pages or less —

25 copies : Zé 3 : 5/-
1 O eat : : ; 6/-
100 iif

Plates, 2/- per 25 if uncoloured ; if colour ed, at the same rate for
every colour.
Prepayment by P.O. Order is requested.
ALL CoMMUNICATIONS FOR THE EDITORS TO BE ADDRESSED TO THE CARE
oF Mussrs. J. & A. Cuurcuint, 7, Great MariporoucnH Srreer,
Lonpon, W.

THE MARINE BIOLOGICAL ASSOCIATION

OF THE

UNITED KINGDOM.
=O
Patron—H.R.H. the PRINCE OF WALES, K.G., F.R.S.
President—Prof. E. RAY LANKESTER, LL.D., F.R.S.

Ht O75

THE ASSOCIATION WAS FOUNDED “‘ TO ESTABLISH AND MAINTAIN LABORATORIES ON
THE COAST OF THE UNITED KINGDOM, WHERE ACCURATE RESEARCHES MAY BE CARRIED —
ON, LEADING TO THE IMPROVEMENT OF ZOOLOGICAL AND BOTANICAL SCIENCE, AND TO
AN INCREASE OF OUR KNOWLEDGE AS REGARDS THE FOOD, LIFE CONDITIONS, AND HABITS
OF BRITISH FOOD-FISHES AND MOLLUSCS.”

The Laboratory at Plymouth

was opened in 1888. Since that time investigations, practical and scientific, have
been constantly pursued by naturalists appointed by the Association, as well as by
those from England and abroad who have carried on independent researches.

Naturalists desiring to work at the Laboratory

should communicate with the Director, who will supply all information as to
terms, &c.

Works published by the Association

include the following :—‘ A Treatise on the Common Sole,’ J.T. Cunningham, M.A.,
4to, 25/-. ‘The Natural History of the Marketable Marine Fishes of the British
Islands, J. T. Cunningham, M.A., 7/6 net (published for the Association by
Messrs. Macmillan & Co.).

The Journal of the Marine Biological Association

is issued half-yearly, and is now in its fifth volume (price 3/6 each number).

In addition to these publications, the results of work done in the Laboratory
are recorded in the ‘ Quarterly Journal of Microscopical Science,’ and in other
scientific journals, British and foreign.

Specimens of Marine Animals and Plants,

both living and preserved, according to the best methods, are supplied to the
principal British Laboratories and Museums. Detailed price lists will be forwarded
on application.

TERMS OF MEMBERSHIP.

|
ANNUAL MEMBERS . E : . £1 1 Oper annum. |
|

LIFE MEMBERS . : ; : . 15 15 O Composition Fee.
FOUNDERS . . : ; : lOO. FORO os os
Governors (Life Members of Council) 500 O O > =

Members have the following rights and privileges:—They elect annually the
Officers and Council; they receive the Journal free by post; they are admitted to
view the Laboratory at any time, and may introduce friends with them; they have the
first claim to rent a table in the Laboratory for research, with use of tanks, boats, &c.;
and have access to the Library at Plymouth. Special privileges ure granted to Governors,
Founders, and Life Members.

Persons desirous of becoming members, or of obtaining any information with
regard to the Association, should communicate with—

The DIRECTOR,
The Laboratory,
Plymouth.

a ee a

}
|
|
|

New Series, No. 171 (Vol. 43, Part 8). Price 10s. |

15a) JULY, 1900.
THE

QUARTERLY JOURNAL

OF

MICROSCOPICAL SCIENCE.

EDITED BY

BE. RAY LANKESTER, M.A., LL.D., F.B.S.,

HONORARY FELLOW OF EXETER COLLEGE, OXFORD; CORRESPONDENT OF THE INSTITUTE OF FRANCE,
AND OF THE IMPERIAL ACADEMY OF SCIENCES OF ST. PETERSBURG, AND OF THE ACADEMY
OF SCIENCES OF PHILADELPHIA}; FOREIGN MEMBER OF THE ROYAL BOHEMIAN
SOCIRTY OF SCIENCES, AND OF THE ACADEMY OF THE LINCEI OF ROME;
ASSOCIATE OF THE ROYAL ACADEMY OF BELGIUM, HONORARY MEMBER
OF THE NEW YORK ACADEMY OF SCIENCES, AND OF THR
CAMBRIDGE PHILOSOPHICAL SOCIETY, AND OF THE ROYAL
PHYSICAL SOCIETY OF EDINBURGH ; HONORARY
MEMBER OF THE BIOLOGICAL SOCIETY
OF PARIS;

DIRECTOR OF THE NATURAL HISTORY DEPARTMENTS OF THE BRITISH MUSEUM; FULLERIAN PROFESSOR

OF PHYSIOLOGY IN THE ROYAL INSTITUTION OF GREAT BRITAIN.

WITH THE CO-OPERATION OF

ADAM SEDGWICK, M.A., F.RS.,

FELLOW AND TUTOR OF TRINITY COLLEGE, CAMBRIDGE 5
1
We PR WELDON, M.A.” FARS.
y) I d
LINACRE PROFESSOR OF COMPARATIVE ANATOMY AND FELLOW OF MEKTON COLLEGE, OXFORD,
LATE FELLOW OF ST. JOHN’S COLLEGH, CAMBRIDGE j
AND

SYDNEY J. HICKSON, M.A., F.R.S.,

BEYER PROFESSOR OF ZOOLOGY IN THE OWENS COLLEGE, MANCHESTER.

WITH LITHOGRAPHIC PLATES AND ENGRAVINGS ON WOOD.

TLONDON:
J. & A. CHURCHILL, 7, GREAT MARLBOROUGH STREET.
1900.

\

ERIE RET eT LT I OM Ee ei a I ee ee ea

Adlard and Son,]

[Bartholomew Close.

CONTENTS OF No. 171.—New Series.

MEMOIRS:

The Anatomy and Ciassification of the Arenicolide, with some Obser-
vations on their Post-larval Stages. By F. W. Gamsiz, M.Sc.,
and J. H. Asawortu, D.Sc., Demonstrators and Assistant Lecturers
in Zoology, Owens College, Manchester. (With Plates 22—29)

Diagrams illustrating the Life-History of the Parasites of Malaria.
By Ronaup Ross, D.P.H., M.R.C.S., Lecturer in Tropical
Medicine, University College, Liverpool, and R. Frerpinc-Ov1p,
M.A., M.B., Acting Demonstrator, Liverpool School of Tropical
Medicine. (With Plates 30 and 31) : 2 ;

Note on the Morphological Significance of the Various Phases of
Hemameebide. By HE. Ray LankestEr

PAGE

419

571

581

SEP i 1900

ANATOMY AND CLASSIFICATION OF THE ARENICOLIDA. 419

The Anatomy and Classification of the Areni-
colide, with some Observations on their Post-

larval Stages.
By

FEF. W. Gamble, M.Sc.,
and
J. H. Ashworth, D.Sc.,

Demonstrators and Assistant Lecturers in Zoology,

Owens College, Manchester.
With Plates 22—99.

CoNnTENTS.

1. Introduetion
. Distribution and Habits
3. Hxternal Characters
I. Segmentation
Il. Prostomium :
III. Eyes and Nuchal Organ
IV. Peristomium
V. Gills
4. Sete
5. Hpidermis
6. Musculature 3 :
7. Generai Anatomy of Internal Organs
8. Alimentary Canal :
9. Vascular System: Heart-body
10. Ceelom
1]. Nervous System
I. Brain ;
Il. @sophageal Connectives
ILI. Ventral Nerve-cord :
IV. Giant-cells and Giant-fibres
A. Giant-fibres
B. Giant-cells ; :
c. The Nature of Giant-cells and Giant-fibres

[a 2)

p The Occurrence of Giant-cells in Arenicola.

you, 43, PART 3.—NEW SERIES,

GG

PAGE
420
4.24
43.4
435
4.36
438
439
441
4.44
452
453
454:
456
458
467
468
469
478
480
483
483
485
491

498

420 F. W. GAMBLE AND J. H. ASHWORTH,

PAGE
12. Sense-organs: Otocysts . : : : : . 500
13. Nephridia . ‘ : : : : 3 . 508
14. Reproductive Organs : : : : : . 521
15. Specific Characters and Classification of the Arenicolide . - 528
16. Affinities of the Arenicolide , 2 : : . 543
17. Summary of Results ; : ; : : . 547
18. Literature . : : 5 : ‘ ; . 554

1. Introduction.

ArnouaH the literature which treats of the anatomy of
Arenicolais a large and growing one, there are several struc-
tures, such as the nervous system, the nephridia, the “ hearts ”
and “ heart-body,” which have received little or no attention
from anatomists such as de Quatrefages, Grube, Claparéde,
Pruvot, Racovitza, who have contributed largely to a know-
ledge of the comparative morphology of Polychetes. Hmbry-
ologists have neglected the Arenicolidee even more. Wilson’s
early paper (1882)! still remains the only account of the
development of an Arenicola (A. cristata) from the egg
up to the early post-larval stage, and naturally enough only
deals with the external features. In 1893 the post-larval
stage of the common lugworm was identified by Dr. Benham,
and though his decision was soon afterwards questioned by
Mesnil (1897), Benham’s statements have since received full
confirmation. It is not our purpose to give in this place a
full résumé of past or recent work on the Arenicolide, but
merely to point out that both in morphology and embryology
there are lacunz where our present knowledge is scanty or
entirely lacking. ‘This statement applies, moreover, to the
groups with which it has been suggested, though on some-
what slender grounds, that the Arenicolide are allied, namely,
the Maldanidz on the one hand and the Scalibregmidez on
the other. For all we know to the contrary, these families
may represent three more or less parallel but independent
modifications. Their relationship can only be adequately

1 The dates in brackets form references to the literature quoted at the end
of this paper.

ANATOMY AND CLASSIFICATION OF THE ARENICOLIDA. 421

discussed when the modifications of structure and develop-
ment of each family are known as a whole. With reference
to the Scalibregmide, for example, many of the structural
features are only known through the work of Rathke (1845)
or of Danielssen (1859). Even more recent writers, such as
Wirén (1887), have been content, when dealing with the
vascular system or the subdivision of the body-cavity, to
record the results of the examination of one or two genera
without even determining the limits of specific differences,
which at any rate in the Arenicolide extend from obvious
external marks to the mode of origin of the gonads, or the
grade of development of certain ganglion-cells in the nerve-
cord.

But there is yet another class of evidence quite as impor-
tant for phylogenetic deduction as the modifications of organs
or the changes in larval and post-larval history. We refer
to the power of response to stimulation, or, in other words, the
physiology of the group. It is generally assumed that the
members of the sub-order of Polychaeta to which Benham
has given the term Phanerocephala Scoleciformia,! like
those of some other sub-orders, have acquired their distinc-
tive grade of organisation, in part at least, in adaptation to
their burrowing or sedentary mode of life. For example, the
reduction of the brain, the small size of the prostomium, the
absence of an armed pharynx, the modifications of the sete,
are explained by reference to the loss of free life, lack of active
competition, and to the necessity of acquiring a structure
conforming to a less complex mode of life than is enjoyed by
the Nereidiformia. A test which is quite applicable to both
groups, since they are in a large sense living under similar
conditions, would be the sense of response to variations of
light-intensity at different phases of growth, and to other
well-known forms of stimulation. At present we have abso-
lutely no data. The noteworthy presence in the Capitellida
of one form, Dasybranchus, which possesses a brain more

1 Including Opheliide, Maldanide, Arenicolide, Scalibregmide, Chlore-
mide, and Sternaspide,

499, F. W. GAMBLE AND J. H. ASHWORTH.

highly organised than that of any other Polychete at present
known, is sufficient to indicate that among other groups there
may be members which possess a highly sensitive organisa-
tion where we at present only suspect a slight power of
physiological response. The search for this important class
of evidence is at present a much more promising field than
the trodden paths of anatomy and embryology, though it is
clear that all these have to advance together in any attempt
to solve a phylogenetic problem.

In this paper, however, we confine ourselves to the anatomy
and the post-larval developmental features of the family.
The work has been largely carried out in Manchester, but has
necessarily involved visits to the coast. We have examined
the Lancashire coast, the neighbourhood of Port Hrin, Isle of
Man, Plymouth Sound, and St. Andrews Bay. To Professor
Agassiz we are specially indebted for the loan of specimens
of Arenicola from the Harvard Museum. We also wish to
express our thanks to M. Felix Mesnil for specimens of A.
Grubii and of Branchiomaldane from St. Martin, and to
Mr. J. E. Duerden, Curator of the Institute of Jamaica, for
obtaining, after much trouble, a specimen of A. cristata
from the shore at Bluefields. The Naples station has sent us
specimens of this species, which is rare, or at any rate diffi-
cult to obtain in the Mediterranean, and also material repre-
senting A. Claparedii and A. Grubii. For the post-larval
stages we are indebted to Mr. R. L. Ascroft and to Dr.
Benham, who gave us a specimen sent to him from Ply-
mouth. To Professor Hickson we owe several valuable sug
gestions, and many of the facilities which have helped us in
the course of the work.

The material upon which this paper is based has been col-
lected from many sources during the last three years.

(1) Arenicola marina, Linn.—In addition to specimens
from various parts of the British and Irish coasts, and from
Jersey, we have received two specimens from the Harvard
Museum, collected at Grand Manan, and also coloured draw-
ing by Professor Agassiz of an undoubted example of this

ANATOMY AND CLASSIFICATION OF THE ARENICOLIDA. 423

species taken at Nahant. Although labelled Arenicola
natalis, Gir., and A. arenata, these American specimens all
belong tothe common Huropean form.

Our attempts to obtain living specimens of larval or post-
larval examples of the lugworm have so far been unsuccess-
ful, but Professor Benham has presented us with a post-larval
stage, 45 mm. long, captured at Plymouth, and Mr. R. L.
Ascroft has given us two specimens taken in the tow-net at
high water near Lytham, on the Lancashire coast.

(2) Arenicola cristata, Stimps (A. antillensis, Liit-
ken.)—Three specimens from Naples ; a large specimen from
the Harvard Museum, but with no indication of its place of
capture ; a smaller one from the same museum, collected at
Captiva Key, Florida; and another, 47°5 mm. long, from
Bluefields, Jamaica,

(3) Arenicola Claparedii, Levinsen.—A_ considerable
number of specimens, full-grown and immature, from Naples ;
and four specimens of what we consider to be this species
from the Harvard Museum, collected by Professor A. Agassiz
at Crescent City, California.

(4) Arenicola Grubii, Claparede.—We have collected
this form in abundance at Plymouth, and at Port Erin and
Port St. Mary in the Isle of Man. Mr. Hornell has supplied
us with specimens from Jersey, M. Mesnil has kindly sent a
few from St. Martin, and we haye also received specimens
from Naples. A specimen was taken by one of us at Port
Appin, near Oban, in Loch Linnhe, and others at Valencia
in the south-west of Ireland.

(5) Arenicola ecaudata, Johnston.—Many adults from
Port St. Mary, Plymouth, Valencia, and Jersey; a few and three
post-larval stages from Port Erin (August, 1896). Dr. 8. F.
Harmer submitted a few specimens collected in the north of
Ireland. They differed slightly from more southern specimens,
but agreed closely with Rathke’s description of his A. Boeckii,
which, however, does not rank as a distinct species.

A424 F. W. GAMBLE AND J. H. ASHWORTH.

2. Distribution and Habits.

DISTRIBUTION.

The genus Arenicola may be divided into two sections ;
one (including A. Grubiiand A. ecaudata) in which the
sills and parapodia are continued tothe end of the body, and
a second (including the remainder of the genus) in which
these structures are confined to the middle region. Of the
members of the first section, A. Grubii is the more southern
form, occurring in the Irish Sea, North Atlantic, the Channel,
Mediterranean, and Black Sea; while A. ecaudata ranges
from Norway on both the east and west coasts of Great
Britain and Ireland to the Channel. Neither of these species
has been hitherto recorded from the American continent.

The sectionof the genus including A. marina, A. cristata,
and A. Claparedii occurs on both sides of the Atlantic. It
was pointed out in our paper (1898) on A. marina, that lat.
40° N. approximately marks the southern limit of this species,
since it is not found either in the Mediterranean or south of
New Jersey. In these more southerly latitudes its place is
taken by A. cristata, which, however, appears to be rare at
Naples, while it is abundant at Charleston Harbour, Virginia
(Stimpson, 1856), and at Anglesea, ten miles north-east of
Cape May (Ives, 1890). It has also been found at Jamaica
(Liitken, Duerden), Florida, and is reported from Vancouver
and Alaska on the Pacific coast. Arenicola Claparedii
isa common Mediterranean form, and four specimens which
exhibit the distinguishing features of this species have been
sent to us from California.

In his catalogue of non-parasitical worms in the British
Museum, Johnston (1865) records three species of Areni-
cola—(l)the common species, A. piscatorum (A. marina),
(2) A. branchialis, (3) A. ecaudata,'—but only the first
and third of these are recognised generally as British.

1 Johnston first recorded and described this species in 1835 (‘ Loudon’s

Magazine’), but gave a new diagnosis and figure in this British Museum
Catalogue,

ANATOMY AND CLASSIFICATION OF THE ARENICOLIDA. 425

In a paper on “ The Habits and Structure of Arenicola
marina” (1898) we have shown that there are on the Lanca-
shire coast two varieties of A. marina, differing in hahits,
structure, and times of maturity. The typical specimens of A.
marina inhabit the littoral zone, living in U-shaped burrows.
They average about eight inches in length, and their gills,
which are only well developed in old deeply pigmented
Specimens, are composed of 9—11 stems, each provided with
3—5 pairs of short lateral branches. These forms breed in
the summer, at any rate on the Lancashire coast.

The second variety of A. marina is found in the upper
part of the Laminarian zone. It breeds in the spring, from
the beginning of March onwards. The gills of this form are
highly pinnate structures, consisting of about twelve stems,
united by a connecting membrane at their bases, and bearing
ten or more branches on each side of the axis (cf. figs. 2 and
38, Pl. 3, Gamble and Ashworth, 1898). This type of gill
has hitherto been known only in A. cristata. The discovery
of two races or varieties of A. marina distinguished by the
form of their gills necessitates a revision of the diagnostic
characters of this species, which have hitherto been based
chiefly on the shape of the gills and on the sete. We were
unable to find the Laminarian variety during a visit in
September, 1897, to St. Andrews, where the coast has been
carefully searched for years by Professor McIntosh and his
pupils without meeting this form. It has, however, been
found in Jersey, and has been figured, probably from the
coast of Normandy, by Milne Edwards in the coloured plates
of Cuvier’s ‘Régne Animal’ (édition de Disciples, pl. viii,
fig. 1). From the records of A. marina made by Scandi-
navian and other naturalists who have examined specimens
from the Northern seas, it would appear that the littoral type
is the only one with which they were acquainted.

The species Arenicola branchialis was established by
Audouin and Milne Edwards (1834, vol. ii, p. 287, and pl.
viii, fig. 18). Itis distinguished, according to these authors, by
having the first fifteen segments setigerous only, by having

4.26 F. W. GAMBLE AND J. H. ASHWORTH.

16 —28 pairs of branchial tufts, and by the posterior portion
of the body being abranchiate and apodous. We have been
at some pains to obtain the types or specimens of this species.
Unfortunately the types are lost from the museums both of
London and Paris. We have not been able to find among the
large number of specimens we have obtained, any which,
while agreeing in other respects, exhibit a tail of the length
figured by Milne Edwards. It is possible that the species
A. branchialis is founded upon a specimen of either A.
ecaudata (which it resembles in the position of the first
pair of gills) or A. Grubii, in which the last few pairs of
gills have not been formed. We have several times found
specimens of A. Grubii without gills, and parapodia on the
last two somites, and indeed specimens of this kind belong-
ing to the species A. Grubii have been sent to us from
Paris labelled A. branchialis. It seems to us that as the
descriptions and figures of this species are insufficient to
enable it to be identified, and as the type specimens have been
lost, for all practical purposes it must be ignored.

While working at Port Erin, Isle of Man, during Easter,
1897, we collected near Port St. Mary specimens of
Arenicola—with gills extending to the end of the body—
which would be called A. ecaudata by most naturalists.
On examination we found that these specimens could be
separated into two sections; the members of one were
characterised by the first gill being attached to the twelfth
chetigerous segment, while those of the other section had the
first gills on the sixteenth segment (Pl. 22, figs. 3, 4). More-
over a careful scrutiny of the nephridiopores showed that
the first section had only five pairs of nephridia, but the
second had no less than thirteen pairs. On comparing these
specimens with A. Grubii from Naples, we saw at once that
those specimens which had five pairs of nephridiopores and
gills commencing on the twelfth chetigerous segment belong
to this species, which had not hitherto been recorded from
Britain ; while the specimens with thirteen pairs of nephridio-
pores correspond exactly with Johnston’s description and

ANATOMY AND CLASSIFICATION OF THE ARENICOLIDA. 427

figure of A. ecaudata. Dissection, moreover, revealed further
differences between the two species, which are especially
obvious in the reproductive organs (see figs. 44 and 45). It
is somewhat remarkable that the result of a dissection of A.
ecaudata has never been published,! since even a rough
dissection of a single specimen, especially in the spring of
the year, would have revealed so many points by which this
species might be at once distinguished from any other species
of Arenicola. The uncertainty which hangs over the
distinctiveness of this species, even at the present time, is
shown by the endeavours of some recent authors to use A.
Grubii, hitherto known from the Mediterranean only, as a
synonym for A. ecaudata. One of the objects of this paper
is to point out the distinguishing characters of the species, so
as to enable more accurate records of these forms to be made
than has been the case hitherto.

The species, A. Claparedii, was founded by Levinsen
(1883, pp. 136—138), who pointed out some of the differences
between this Mediterranean form and the northern specimens
of A.marina. Specimensof Arenicola from Naples which
possess thirteen pairs of gills are often labelled A. marina,
which, however, does not occur in the Mediterranean. It is
replaced by A. Claparedii, which differs from A. marina in
the form of its gills, in having only five pairs of nephridia, and
in other ways.

Stimpson (1856, p. 114) founded the species A. cristata
(A. antillensis, Litken) upon specimens obtained in
Charleston Harbour. ‘This species differs from others in the
richly pinnate character and smaller number of the gills, and
in usually possessing certain papillary processes on the tail
(Pl. 22, fig. 1, and Pl. 24, figs. 30—33).

All specimens of Arenicola which have hitherto been
completely investigated and described, fall within the five
species mentioned above, viz. A. marina, A. cristata, A.
Claparedii, A. Grubii, and A. ecaudata.

1 Since this was written we have received a paper from M. Fauvel (1899)
in which this has been done.

428 F. W. GAMBLE AND J. H. ASHWORTH.

A. marina (= A. piscatorum, Lamarck) includes A.
tinctoria, Leach, and A. carbonaria, Leach,! which dif-
fered somewhat in colour from more typical specimens.
A. natalis, Girard (1856, p. 88), is nothing more than an
ordinary A. marina, in which Girard has mistaken the
ventral for the dorsal surface. The smooth dorsal line which
he describes as one of the peculiar characters of this worm
is the line found on practically all specimens of Arenicola
indicating the position of the ventral nerve-cord, its anterior
division into two being the usual division into the two
metastomial tracts or grooves which mark the position and
course of the cesophageal connectives. A. natalis has
thirteen pairs of gills, and six pairs of parapodia in front of
the first gill, thus exactly agreeing in these respects with A.
marina. It was found on Chelsea Beach (Mass., U.S.A.),
1.e. well to the northward of lat. 40° N., which, as we have
shown, marks the southern limit of A. marina.

As stated below, Clymenides sulfureus, Mesnil (1897),
is now proved to be the post-larval stage of A. marina.

A. cristata (= A. antillensis, Liitken, 1884) probably
also includes A. glacialis, Murdoch,? from Alaska. The
description of this latter species is very brief and insuffi-
cient, the only characters of real importance mentioned being
the presence of eleven branchiferous segments, preceded by
six abranchiate segments, thus exactly agreeing with A.
cristata.

Czerniavsky* describes three new species of Arenicola
from the neighbourhood of Sevastopol (Black Sea), viz. A.
cyanea, A. dioscurica, and A. Bobretzkii; but these are
undoubtedly specimens of A. Grubii, differing from each
other only in colour, age, and size. All of them have eleven
anterior abranchiate segments, as in A. Grubii, and at

1 *Hneyclopedia Britannica,’ Supplement, vol. i, p. 452.

2 «Proceedings United States National Museum,’ Washington, vol. vii,
1884, p. 522.

* «Bulletin de la Société Imperiale des Naturalistes de Moscou,’ vol. lvi,
1881, pp. 358—356.

“ANATOMY AND CLASSIFICATION OF THE ARENICOLIDA, 429

most only one posterior abranchiate segment, which, as men-
tioned above (p. 426), is frequently found in specimens of
A. Grubii. The only differences between these forms are
connected with the colour and number of gills.

The colour of A. Grubii varies within wide limits, for in
one gathering at Port St. Mary we have taken specimens of
this species varying in colour from dark green through dark
red to reddish yellow. The number of gills described as
occurring in A. cyanea, A. dioscurica, and A. Bobretz-
kii is respectively thirteen, fifteen, and twenty pairs. This
difference is probably explained by the different ages of the
specimens chosen as typical of the species.

A. Boeckii, Rathke, as described by him (1843, p. 181,
and pl. vil, figs. 19—22), is an indubitable but probably
young A. ecaudata, as it has the first gill on the sixteenth
chetigerous segment, and has forty pairs of gills. Speci-
mens agreeing with Rathke’s description have been sub-
mitted to us, and after acareful examination of their external
characters, and of some points in their internal anatomy, we
consider them to be young forms of A. ecaudata (see p. 423).
Clymenides ecaudatus, Mesnil (1897), is the post-larval
form of A. ecaudata.

A. pusilla, de Quatrefages,! of which only a single in-
complete specimen is known, from Coquimbo: A. assimilis,
Khlers,? from the Straits of Magellan: and A. Loreni,
Kinberg,® from the Cape: are so shortly and insufficiently
described, that for all practical purposes they must be
ignored.

Hapsirts.

(1) Arenicola Grubii and A. ecaudata.

On the coast of the Isle of Man, at Port Hrin and Port
St. Mary, and at Plymouth, A. Grubii and A. ecaudata

1 «Hist. des Annelés,’ tome 2, part i, p. 266, 1865, Paris.

2 ¢‘Magalhaen. Sammel Reise-Polycheten,’ Hamburg, p. 108, 1897.

3 «Kong. Svenska Fregatt. Hugenies Resa,’ 1857, and ‘ Annulata nova
Recensuit,” ‘Oefv. k. Vet. Akad. Forhandl.,’ 1865, p. 355,

430 F. W. GAMBLE AND J. H. ASHWORTH.

live together near the bases of rocks in a deposit composed
of sand and small stones. Like A. marina, they are charac-
teristically littoral animals, occurring in and above the upper
portion of the Laminarian zone. At Port St. Mary they are
best obtained by overturning large boulders lying on the
gravel-like beach, and digging in the place so exposed with
the hands until the worm is seen gliding, almost like an
earthworm, intoits burrow. The excavation is then enlarged
all around this point, as the worms seem to occur in batches in
certain places, each of which, being probably very suitable to
their wants, has attracted several specimens. The débris of
decomposing rock appears to have a great attraction for these
species, and in a suitable locality such as Port St. Mary
they may be collected in considerable quantities. At this
place four workers obtained seventy-six specimens of A.
Grubii and thirty-six of A. ecaudata in the course of
rather over an hour’s work, while at Port Hrin only about
half a dozen specimens of A. Grubii were obtained in
the same time. ‘These species do not construct a regular
burrow like that of A. marina. They are often found in
oblique and curved holes in the gravel, a few inches below
the surface, but there is not a definite opening leading to the
exterior. ‘hey take into their alimentary canal the sand
and gravelly material in which they live, and their castings,
being composed of larger particles, are less firm than those
of A. marina; and the components fall apart from each
other, mingle at once with the gravel among which the worms
live, and are not piled up on the surface as in the case of the
common lugworm. In specimens of A. ecaudata obtained
from Valencia (co. Kerry) there was little sand, but the
alimentary canal was distended with pieces of Fucus. At
Naples A. Grubii lives chiefly in sand mixed with putres-
cent matter, and breeds through the spring (Lo Bianco,
1899). On the British coasts both this species and A.
ecaudata breed in the spring.

Most specimens of A. ecaudata are yellowish red or
dark red in colour, but some are dark green. A. Grubii is

ANATOMY AND CLASSIFICATION OF THE ARENICOLIDA. 431

generally dark green in colour, but may be dark red or
occasionally yellowish red in colour.

As we said above (p. 429), Arenicola Boeckii appears
to be merely a variety of A. ecaudata, and we are confirmed
in this opinion by the examination of a few specimens col-
lected by Mr. H. Hanna, of St. John’s College, Cambridge,
and sent to us for identification by Dr. Harmer. The note
appended to them (written by Mr. Hanna) supplies some details
of their capture. “The specimens came from Murlough
Bay, near Fair Head, co. Antrim. Four were found living
in deep circular pits, 24 feet deep and about 1 foot broad,
in a raised bank of soft green sandstone near high water.
The bank of rock was washed over by waves at high tide.
The worms were of a bright scarlet colour, and lived in soft
greyish mud inside their membranous tubes, which slipped
off very readily.” The form and position of the nephridia
show that these specimens belong to Arenicola ecaudata,
but as they differ in appearance from specimens of the usual
pigmented type in their transparent body-wall, and agree in
this respect and in size with Rathke’s A. Boeckii, we con-
sider them to form a variety of the species A. ecaudata,
for which Rathke’s name may be retained.

Concerning the methods of oviposition and the habits of
the larva we have been unable to obtain any information,
but we have obtained three very young specimens of A.
ecaudata.

On August 18th, 1896, while at Port Erin one of us col-
lected at a very low tide a large number of the “ roots” of
Laminaria from the ruined breakwater, in the hope that
in their interstices some rare worms might be lodging. On
washing and examining the roots carefully one by one, many
worms were obtained, among which were three young speci-
mens of A. ecaudata. ‘These are 7:2 mm., 8 mm., and
9-4 mm. long respectively. They are probably only a few
months old, and had but recently settled down to their
littoral habitat. They possess thirteen pairs of nephridia,
but no gills have yet been formed (PI. 24, figs. 35, 36).

432 F. W. GAMBLE AND J. H. ASHWORTH.

Fauvel (1899) has shown that the early post-larva of A.
ecaudata before the assumption of gills lives not in sand,
but in the interstices of algze. It is enclosed in a gelatinous
tube, through which the internal organs of the transparent
body can be readily perceived. Only later on when the gills
are well developed does the animal adopt the arenicolous
mode of life.

Lo Bianco (1893, p. 10) states that Neapolitan specimens
of A. Grubii attain a length of 150mm. The largest British
specimens of this species and of A. ecaudata attain a length
of 225 mm.

The skin of A. Grubii and A. ecaudata is remarkable
for the large amount and tenacity of the mucus which exudes
from it. This is generally yellowish green in colour, and
readily stains the hands.

The peristaltic action of the body-wall, the waves passing
from behind forwards, was observed even more clearly than
in A. marina, but the gills of these two species do not possess
the same amount of contractility as those of A. marina.

(2) Arenicola Claparedii.

This species is found at Naples living in sand mixed (Lo
Bianco, 1893, p. 9; 1899, p. 484) with putrefying matter, and
breeds from November to May. The body is often trans-
parent, the tail chrome-yellow. In other specimens the colour
is reddish with green reflections. The examples from Crescent
City, California, were of a dark green, almost black colour.
Specimens of A. Claparedii average about 70—80 mm. in
length, but according to Lo Bianco (1899) they may attain a
length of 150 mm.

(3) Arenicola cristata.

This species is rare at Naples, and occurs chiefly among
(Lo Bianco, 1899, p. 484) decaying matter in the Porto mer-
cantile, breeding from June to August. It was found by
Stimpson (1856) at the entrance to Charleston Harbour living

ANATOMY AND CLASSIFICATION OF THE ARENICOLIDA, 433

in the lower portion of the littoral zone. The general colour
is dark velvety bottle-green, with slight yellowish and bluish
iridescence. The branchiz and proboscis are reddish, the
notopodial setze golden yellow. The specimen from Captiva
Key is flesh-coloured, and the one from Jamaica is black up
to the seventh segment, semi-transparent and almost colour-
less behind.

The large American specimen of A. cristata is 360 mm.
long (Pl. 24, fig. 80), and specimens 400 mm. long have been
taken at Naples (Lo Bianco, 1899, p. 484).

According to Liitken (1864) this species (to which he gave
the name A.antillensis) is common on the shores of the
West Indies, but although Mr. J. HK. Duerden, Curator of the
institute of Jamaica, has searched the coast for some time he
has only been able to meet with one specimen, so that this
species is not common on the Jamaican shores.

Of the habits of A. cristata Stimpson (1856) says, “ It
occurred in the third and fourth sub-regions of the littoral
zone, living in holes in the hard sand excavated to two feet.
The holes were exactly adapted to the thickness of the
animal, and were not furnished with a lining of any kind.
They extend obliquely downwards, at first perpendicularly,
then curving horizontally. The lower extremity is about
one foot below the surface. Hach worm was found head
downwards in its burrow. During the latter part of March
we frequently observed in and about the holes of this animal
ereat quantities of a soft transparent jelly filled with minute
brownish specks, which proved to be the eggs.” Of these
ego-masses Professor EH. B. Wilson (1883) gives an interest-
ing account. “The eggs are embedded in huge gelatinous
masses, which assume various forms as they are swayed to
and fro by the tide. A common form is irregularly cylin-
drical, three or four feet long and as many inches wide.
Sometimes they are rounded and shapeless, lying flat on the
sand ; in other cases they are as long as six feet and more,
and from one to three inches in diameter. The eggs are
small, ‘13 mm, in diameter, nearly spherical or slightly ovoid,

A434 F. W. GAMBLE AND J. H. ASHWORTH.

very opaque, and are enclosed in a thick chorion, which seen
by oblique light appears to be perforated by minute radiat-
ing pores. The yolk is a hight cinnamon colour. Segmenta-
tion is almost equal, and the embryo gradually elongates, and
when eighteen to twenty-four hours old acquires a belt of
cilia in front of which two eye-spots appear, and a broad
band of cilia also appears on the ventral surface. The first
pair of setee appears on the third day, and the mouth is by
that time distinct. The larve hatch on the third day, and
swim freely for a day or two. The notopodial: sete are first
formed, appearing from above downwards; the neuropodial
setee appear at the end of the third or beginning of the
fourth day. The larve then secrete a gelatinous tube, sink

to the bottom of the vessel, and creep about there. There
- they lived for more than three weeks, and by the end of that
time possessed eleven to twelve setigerous segments.”

The post-larve of A. marina taken at Plymouth by
Garstang, and described by Benham (‘ Journ. Marine Biol.
Assoc.,’ vol. i1, No. 1, 1898, p. 48), also inhabited gelatinous
tubes which they had secreted, and which closely invested
their bodies. This covering, however, did not prevent them
swimming actively in an eel-lke manner, generally near
the surface of the water (Garstang).

Small specimens of A. marina when taken from the
sand are beautifully transparent for some time, but when
placed in sea water the skin gradually becomes translucent
and finally opaque. littoral forms are generally reddish or
yellowish red in colour, while those from the Laminarian zone
are much darker in colour, sometimes indeed almost black.
On the Lancashire coast Laminarian specimens attain a
length of 400 mm.

8. External Characters.

Although the chief external features of the Arenicolide
have been carefully studied by a number of zoologists, yet
there is still some doubt as to the meaning of certain of

ANATOMY AND CLASSIFICATION OF THE ARENICOLIDA. 435

the more obscure points, such as the prostomium, the mor-
phological value of the buccal segment, the nature of the
gills, the presence of cirri, the presence or absence of scat-
tered sense-cells in the skin of the body.

I. Segmentation. — The strictly morphological com-
ponents of the entire worm are the prostomium, the pygidium,
and the long intermediate region composed of segments, the
parapodia of which mark out certain regions. Thus there
is always a chetigerous but abranchiate region up to the
seventh segment;! then in the “marina” section of the
genus there are from eleven to thirteen segments, bearing
plumose, highly vascular gills attached to the dorsal element
(notopodium) of the parapodia. Gills and parapodia then
cease, and behind this point there is merely a caudal region,
varying in length, and, with the exception of some varieties
of A. cristata, unprovided with any parapodial outgrowths,
though still preserving traces of its segmentation. In these
specimens of A. cristata there is a double paired row (one
pair more dorsal and one more ventral) of hollow processes
placed at segmental intervals along the sides of the tail (PI.
22, fig. 1, and Pl. 24, figs. 30—32). We discuss this matter
more fully later on (p. 442). In the “ecaudata” section
the gills and sete are continued to the hinder end of the body.

The presence of branched, strongly developed gills, and
their arrangement on at any rate all the middle segments,
together with their absence from the first seven, is. a cha-
racter which distinguishes the genus Arenicola. Almost
equally diagnostic and constant is the secondary annula-
tion of the skin, so that the space between two chetigerous
annuli is subdivided by three grooves into four rings. ‘The
second of these grooves posterior to each of the chetigerous
annuli is the intersegmental groove, and at this level the
septa, if present, are inserted. The segments of the caudal

1 The first bundle of sete is placed in the adult worm in the middle of the
first cheetigerous segment, and this segment is referred to in the text as the
first segment. Consideration shows, however, that it is probably really the
third segment (see p. 441).

VOL, 43, PART 3.—NEW SERIES. HH

436 F. W. GAMBLE AND J. H. ASHWORTH.

region in the “marina” section of the genus cannot, however,
be determined by this criterion, since the chetigerous annuli
are missing.

The division of the body of Capitellids into thorax and
abdomen by the use of regional characters afforded by the
sete alone, finds but a feeble analogy in Arenicola. The
anterior segments bear as a rule both the capillary sete de-
fining the “ thorax,”’ and the crotchets which are confined to
the “abdomen” of at least some genera of Capitellide. In
Arenicola cristata alone is there an approach to the
Capitellid arrangement. For in the first two and in some cases
three segments the crotchets are absent or invisible in a
surface view. ‘The regional external characters are afforded
by the gills, which, as we have already mentioned, are pecu-
har to the genus and the family.

Il. Prostomium.—Though necessarily fused at its pos-
terior margin with the peristomium, the prostomium is distinct,
and at least in A. Claparedii fairly well developed (Pl. 27,
figs. 59, 60). It is often stated or implied that this fusion
is more extensive, and entails the more or less complete
suppression of the prostomium, in Arenicola. Such, however,
is not the case; and even in the “ecaudata” section, where
it attains its least development, this structure has fully pre-
served its individuality (Pl. 22, fig. 5). The misleading state-
ments to the contrary are probably due to the retraction of
this structure within the nuchal groove, which results from
most of the ordinary killing methods. A powerful retraction
of the buccal muscles in the living animal also tends to hide
the prostomium.

As is the case with so many other structural features, the
prostomium exhibits two types characteristic respectively of
the “marina” and the “‘ecaudata” sections of the genus.
In the former it is a hollow, lobate, highly vascular and thin-
walled structure; in the latter it forms a smooth, conical,
Opaque prominence. ‘The forms which it assumes are more
readily understood from Pl. 22, figs. 2, 5, and Pl. 27, figs. 59
—61, than from lengthy descriptions.

ANATOMY AND CLASSIFICATION OF THE ARENICOLID®. 437

The shape of the prostomium of A. marina was described
and figured in our previous paper, and we have only to add
that A. cristata has an organ of almost exactly similar
shape. In specimens from Jamaica, Naples, and the Pacific
coast of America it is uniformly of a trilobate shape, and
measures about 1 mm. in length by slightly more in breadth.
It is hollow, and contains an extension of the ccelom accom-
panied by vessels. As in the lugworm, the brain is in close
association with the skin, and fills up the greater part of the
cavity of the prostomium.

In A. Claparedii, different specimens of approximately
the same and of different lengths exhibit a considerable
variation in the shape of the prostomium (Pl. 27, figs. 59—
61). Its comparatively large size drew Levinsen’s atten-
tion to it, and he demonstrated for the first time the presence
of the prostomium as a distinct structure in the Areni-
colide. Some of the Californian specimens show a marked
similarity in prostomial form to the typical adult Mediter-
ranean ones, while others differ slightly in this respect, but
their differences are paralleled by the variation in the shape
of this organ in the young Neapolitan specimens as com-
pared with adults. Unfortunately we have never seen A.
Claparedii alive, and we are unable to state how far these
differences may be accounted for by irregular contraction
of the prostomial lobes, and how far they may represent
natural variations in the form of the organ itself. The
form of the organ is essentially similar to that of A.
marina, but the median area is often conspicuously raised,
while the lateral projections are bent downwards and out-
wards, so as almost to suggest in some specimens that they
represent traces of tentacles. Though hollow, the anterior
lobes of the brain extend into them, so it is not probable
that they are of tentacular nature. A comparable pro-
stomium occurs in Scalibregma, in which the anterior
prostomial margin is produced outwards like the cross of
a T (see Rathke, 1843, pl. viii).

In the “ecaudata” section the conical, non-lobate pro-

438 F. W. GAMBLE AND J. H. ASHWORTH.

stomium is similar in the two species (Pl. 22, fig.5). In front
it is continuous with the papillose margin, forming an upper
lip which overhangs the mouth.

Ill. Eyes and Nuchal Organ.—There are two struc-
tures developed from the prostomium, the eyes (Pl. 24, fig.
34) and the ciliated grooves or nuchal organ, which may be
considered under the head of external organs, though the
former and the greater part of the latter are hidden when an
adult specimen is viewed from without. The structure of
the eyes is more fully considered in the section on the sense-
organs (p. 506, and Pl. 27, fig. 55). It will be sufficient to
state here that they are comparable with the earliest stage
of the development of eyes in Nereis as regards structure,
but that they are sunk even in early post-larval stages of A.
marina into the ganglionic layer of the brain. In this
position they persist apparently throughout life in all species
of the genus.

The nuchal organ or ciliated groove is a V-shaped ciliated
but deep and narrow groove, formed by an invagination of
the epidermis of the sides and hinder end of the prostomium,
as is well seenin the figure of A. Claparedii on PI. 27, figs.
56 and 57, from a specimen 26 mm. long. The arms of the
groove diverge, and run somewhat outwards and downwards
as far as the anterior cerebral lobes, while their hinder ends
are connected by a curved portion lying at a higher level.
Since, however, the groove is sunk deeply into the body its
appearance in horizontal section is that of a pair of tubes
commencing anteriorly in the angle made by the projection
of the lateral prostomial lobe, and then running inwards and
backwards, so that only the dorsal sections show the union
of the two grooves near the hinder edge of the prostomium,
although of course they are in connection with the exterior
along their whole length.

In A. cristata the nuchal organ is essentially similar to
that of A. marina described in our previous paper, and it
is only necessary to emphasise the single character of the
organ ; for although it is innervated from a pair of posterior

ANATOMY AND CLASSIFICATION OF THE ARENICOLIDA., 439

cerebral lobes there is no reason for regarding it as a double
structure, at least in full-grown Arenicola, though it may
arise from a paired origin, and is undoubtedly equivalent to
the pair of ciliated eversible organs in Capitellids and
Opheliacea, and to the two longitudinal grooves on the
prostomium of Maldanide. In a very young specimen of
Arenicola marina in our possession (a post-larva 4°5 mm.
long) the nuchal organ is already present, and consists of
a median transversely placed depression ‘04 mm. from side
to side and ‘012 mm. deep.

The groove is similar in both A. Grubii and A. ecaudata,
while its course differs from that hitherto described (PI. 22,
fig. 5). The arms of the groove commence ventro-laterally,
and run upwards and backwards, but before meeting on the
dorsal surface of the prostomium they bend sharply back-
wards and then unite in a short transverse line. In A.
ecaudata the thickened lips are nearly black in colour and
fairly wide apart, and thus contrast with the pink tint of the
bottom of the groove. In A. Grubii the lips are more
closely apposed.

In this section of the genus the nuchal organ is further
distinguished by its innervation. In place of the cerebral
lobes of A. marina there are several posterior outgrowths of
the commissure-like brain, which have rather the appearance
of nerves than of lobes. In some specimens, however, a
median process of the brain extends backwards so as to
underlie the dorsal part of the nuchal groove. The organ is
already present in post-larval specimens of A. ecaudata
7:2 mm. and 9'4mm. long.

IV. Peristomium.—The peristomium is fused with an
annulated achztous region, which lies in front of the first
parapodium. ‘The composition of this region is difficult to
determine, but it can be shown to result from the fusion of
the peristomium and the first chetigerous segment, the seta
of which is vestigial and disappears early. The grounds for
this conclusion rest upon (1) the external delimitation of
the peristomium from the first segment in the post-larva of

44.0 F. W. GAMBLE AND J. H. ASHWORTH.

both A. marina and A. ecaudata (PI. 24, figs. 34, 35) ; (2)
the constant position of the otocyst; (3) the vestigial seta ;
(4) the nerves given off by the connectives ; and (5) the
presence of a segmental “ giant-cell” in the cord just behind
the point of union of the commissures (see Pl. 29, fig. 79).

The debatable region in question extends from the hinder
border of the prostomium (as indicated by the nuchal groove)
to the annulus immediately in front of the first (adult) para-
podium. Laterally it is often marked by two sloping grooves,
the “ metagstomial grooves” of Ehlers (1892), which indicate
the course of nerve connectives uniting the brain with the
ventral cord. It is crossed by a number of circular grooves,
which vary in number in different species. The skin of the
annulus between any two grooves is marked out into raised
areas like a mosaic.

The position of the otocyst is indicated by an aperture
(A. marina) or by a slight depression (A. Grubii and A.
ecaudata), a little dorsal to the point of intersection of the
second of these grooves (counting from the prostomium)
with the metastomial groove. The otocyst is supplied by a
large nerve from the commissure, and a special development
of ganglionic cells occurs at the pomt of origin of the
otocyst nerve, extending slightly beyond and below this
point. The region between the prostomium and the second
groove is thus composed of two annuli bounding the mouth,
and containing the otocyst, otocyst nerve, and ganglion. This
region constitutes the peristomium. On this view the sugges-
tion made by Ehlers that the otocyst represents a pair of
modified peristomial cirri is extremely probable, but as the
early development of these organs has not been studied in
Arenicola, Aricia, Wartelia, or any other genus, the
suggestion can hardly be regarded as proven.

The presence of a vestigial seta in post-larvee of A.
marina (Benham), A. ecaudata (Mesnil), which disappears
later, indicates the presence of a segment between the
peristomium and the first adult chatigerous segment. We
have not been able to confirm the occurrence of this seta

ANATOMY AND CLASSIFICATION OF THE ARENICOLIDA. 441

with any certainty, but we are able to produce additional
evidence in favour of this view. In A. marina and A.
Grubii there are certain “ giant-cells ” which occur usually
in couples near the hinder limit of each segment (see Pl. 29).
In A. ecaudata and A. cristata we have also found them
in the anterior segments, and always in the same relative
position. Now at the meeting-point of the connectives there
is a single giant-cell in the first three of the species named.
This giant-cell lies in the region which bears the vestigial
seta, and it may be taken as confirming the view first sug-
gested by Benham (1893) that this is the second segment,
the first parapodium being attached to the third.

The limits of the second segment then include a number
of annuli up to the dorsal insertion of the first septum, exactly
one annulus in front of the first parapodium of the adult.
Accordingly the first chetigerous segment of the full-grown
Arenicola is really the third, and is preceded by a segment
bearing a giant-cell and vestigial seta, and this again by the
peristomium.

The conical notopodium and vertical rows of neuropodial
crotchets le about, or slightly behind, the middle of each of
the succeeding segments. In all the species the surface of
the body is areolated ; the areolez are composed of glandular
pigmented cells, the interstices being made up of finer non
glandular elements.

V. The Gills.—These structures, so characteristic of the
genus, are hollow branched outgrowths of the body-wall, and
contain an extension of the ccelom by which the afferent and
efferent blood-capillaries are brought into close contact with
the thin and delicate epidermis. ‘The gills are attached to the
inner side of the notopodium, and their branches radiate from
this point like the parts of a fan. In the “ marina” section
the type of gill is in every species the same, though, as we
showed in our previous paper, there are two distinct varieties
of gill (the dendritic and the larger feathery or pinnate) in
A. marina. In this type the branches are only connected
together at their bases by a kind of webbing, they are not

442 F. W. GAMBLE AND J. H. ASHWORTH.

fused basally. In A. ecaudata and A. Grubii (as Horst
[1889] first pointed out for the latter) the branches all spring
from a common stem. The mode of division of the branches
into leaflets is also somewhat different in the two cases. In
A. marina, A. cristata, and A. Claparedii the division is
nearly pinnate, though the leaflets are not strictly opposite,
but more nearly alternate. In A. ecaudata and A. Grubiu
the branches bifurcate, and then the posterior of the two so
formed dichotomises near its tip. By a repetition of this
process the leaflets have a very distinctive appearance when
seen en masse, as contrasted with a pinnate type, all the
subdivisions taking place on the corresponding (posterior)
side of the secondary branches. The figures on PI. 22, fig.
7, will help to make this clear.

The gills so formed are in some species retractile, though
never to the same degree as in Capiiellids. This property
is best developed in the common lugworm, in which the whole
line of gills contracts from behind forwards, and so, as Milne
Edwards (1838) pointed out, assists in maintaining a circula-
tion of the blood.

The gills of the Arenicolide are usually considered to be
special structures rather than modifications of a dorsal cirrus,
on the grounds that in development each gill arises from a
slight evagination of the body-wall without the appearance
of any specially sensory structures such as in the Nereidi-
formia occur on the dorsal cirri before their transformation
into gills (Benham, 18938, p. 50). The gills of Arenicola, in
fact, develop from the first in connection with a capillary loop,
and function at once as respiratory structures.

Cirri, in fact, have never been demonstrated in the
Arenicolide. In A. cristata, however, certain large
papilla occur on the tail (Pl. 22, fig. 1, and PI. 24, figs. 30
—32), and these have been variously interpreted as cirri,
as accessory gills, or as merely somewhat large purely
epidermal processes. Stimpson (1854) and Liitken (1864)
have referred to them in describing American and West
Indian specimens. Levinsen (1883) suggested that they

¢

“ANATOMY AND CLASSIFICATION OF THE ARENICOLIDA. 448

might be gills, but Ehlers (1892) was not disposed to take
this view. No good description has been hitherto published,
and no histological details exist up to the present.

On the first caudal segment of the large specimen lent to
us by the authorities of the Harvard Museum there exists
a pair of rudimentary gills. This is clearly shown by the
one on the right side being composed of four distinct
branches bearing short processes (Itud. Br., Pl. 24, fig. 31).
These two additional gills agree in position with the normal
ones.

Just dorsal to each of the last four or five neuropodia of
this specimen, and of another from Captiva Key (PI. 24, fig.
39), there is a small tubercle (sometimes a slight depression),
distinct, from its size and colour, from the neighbouring
scattered papillae. The imperfect state of preservation of
these specimens prevents us from making an exhaustive
histological study of these structures, which agree in position
with the “ Seitenorgane ” of Capitellids. It is very possible
that examination of fresh or well-preserved material will
result in the discovery of a sensory epithelium on these
tubercles. There are also segmentally arranged outgrowths
on the tail (Pl. 24, figs. 31, 32). Two of these, as we have
already stated, are accessory gills; and just as beneath the
last few pairs of fully developed gills there are peculiar
tubercles, so beneath these rudimentary gills on the first
caudal segment there is a tubercle, or rather two, one above
the other. The three structures, gill and tubercles, are
placed on a thickened annulus clearly corresponding (PI. 24,
figs. 31, 32) to one of the chetigerous annuli, as is further
shown by their relation to the internal septa (fig. 30). The
more dorsal of these tubercles on the left side was 3 mm.
long, and the one beneath this 2 mm. long. In section these
tubercles are found to be hollow vascular outgrowths of the
whole thickness of the body-wall, and though we have not
ascertained that the epithelium has specially sensory elements
or is ciliated, yet it is undoubtedly composed of columnar
glandular cells, These tubercles are cirriform structures, but

444 F. W. GAMBLE AND J. H. ASHWORTH.

in the absence of any good evidence of their sensory nature it
would be premature to call them cirri.

Each of the remaining segments of the tail bears one or
two such tubercles, which are distinguished by their size and
hollow vascular nature from the scattered epidermal papille.
The annuli upon which they are placed are thickened and
placed regularly at segmental intervals (PI. 24, figs. 31, 32).

Such tubercles, borne on either the last chetigerous seg-
ments or on the tail, occur in all the American and West
Indian specimens we have examined. They are absent,
however, from the Neapolitan examples of A. cristata.

4. Sete (Pl. 23).

The sete of Arenicola may be divided into two kinds:
(1) the capillary setee forming the notopodial pencil; and (2)
the crotchets or chete present in the neuropodial ridge:
though, as we shall point out below (see p. 446), these two
kinds of setee in very young forms are not strictly confined to
the positions above named.

Notopodial Seta.—The notopodial sete are similar
throughout the genus, though there are certain features which
appear to be characteristic of the various species. Hach
notopodial seta is a slender capillary structure inserted at its
proximal end, along with many other similar setz, in a setal
sac, which is moved by special retractor and protractor
muscles. The seta has an almost uniform diameter for a con-
siderable portion of its length, but it tapers at its distal end
to a fine point. This tapering portion bears several rows of
very minute hair-like processes, beautifully and regularly
arranged like the barbs of a feather upon its shaft (figs. 13,
20, 23).

The notopodial sete of adult specimens of A. marina, A.
Claparedii and A. cristata closely resemble each other.
They are moderately stout, and the hair-like processes upon
them are numerous and well marked. The notopodial setz
of A. cristata are very hairy, especially in old specimens,
and the barbs or processes on the setze are more numerous

ANATOMY AND CLASSIFICATION OF THE ARENICOLIDE, 445

than in any other species of Arenicola (see figs. 13, 14).
In the notopodia of A. cristata the capillary setze appear to
be arranged in two more or less distinct transverse rows.
This is more obvious in the American than in the Neapolitan
specimens in our collection. The anterior row contains
shorter sete than the posterior row, those in the former being
about two thirds the length of those in the latter (see Pl], 24,
fig. 33), but in other characters they are identical.

The sete of A. Claparedii are closely similar to those of
A. marina, but are rather smaller and their barbs more
obvious (fig, 23).

The notopodial sete of A.ecaudataand A. Grubii are
identical in form and characters. They are more slender than
those of the three species named above, and taper very
gradually indeed to a long and slender tip. The hairy pro-
cesses are fewer in number, smaller in size, and more closely
appressed to the shaft of the seta, so that they are much less
obvious than those of the setz of the three caudate species
(fig. 20).

The length of the largest notopodial sete we have met
with in the different species is as follows :—A. marina (250
mm. long) 7°5 mm., A. Claparedii (95 mm. long) 2°7 mm.,
A. cristata (360 mm. long) 9 mm. (the shorter sete of the
anterior row are 6'4 mm. long in this specimen), A. ecaudata
and A. Grubii (200 mm. long) 3°8 mm.

The notopodial sete of post-larval stages of A. marina
show several interesting points. The notopodia of a specimen
of A. marina, 3°9 mm. long, bear from four to six sete,
which, on further examination, prove to be of two different
kinds (Pl. 23, fig. 12). Some are typical capillary sete,
about *3 mm. long, bearing on their distal fourth minute
hairy processes similar to, but of course smaller than, those of
the adult setze (fig. 12 a).

The other notopodial setze are quite different, being only
about ‘17 mm. long, and ending in an exceedingly long fine
point. A little beyond the middle of its length the seta
bears a thin lamina or wing on each side, upon which very

446 F. W. GAMBLE AND J. H. ASHWORTH.

faint oblique striations are occasionally visible (fig. 12 8).
Each notopodial pencil contains only one seta of the latter
kind, accompanied by three, four, or five of the normal
plumose setee (Pl. 24, fig. 34).

Mesnil (1897) found these two kinds of sete in the noto-
podia of a small polychzte, which he then identified with
Clymenides sulfureus, Claparéde. On comparing the
post-larval stages of A. marina in our possession with
Mesnil’s descriptions and figures of this polychaete we have
no doubt that his Clymenides is nothing but a post-larval
A. marina, and in a later paper Mesnil (1898) has arrived
at the same conclusion.

The notopodial setze of post-larval specimens of A. ecau-
data are also somewhat different from those of the adult.
Thus in a specimen 7'2 mm. long they are ‘25 mm. to ‘3 mm.
long, and bear a distinct lamina on one side of the distal third
or half of their length. The lamina is divided into two
portions, a short proximal part devoid of hairs, and a longer
distal part, on the greater portion of which distinct hair-hke
processes may be seen (fig. 21), while between the two seta
is slightly constricted. Setz identical with these were
described by Mesnil (1897) from a small polychaete to which
he gave the name Clymenides ecaudatus. On the pub-
lication of Mesnil’s paper we at once identified his speci-
mens with our post-larval specimens of Arenicola ecaudata
obtained in August, 1896, to which conclusion Mesnil has also
arrived in his later paper (1898).

The most remarkable feature noticeable in the sete of
young specimens of A. ecaudata is one to which Mesnil has
also drawn attention, viz. that a crotchet indistinguishable
from those of the neuropodia occurs in some of the posterior
notopodia alongside the ordinary capilliform sete. In the
posterior portion of a specimen 8 mm. long we find a
crotchet in the notopodium in each of the last six segments
which bear notopodial setz, i. e. in the last formed or young-
est segments (Pl. 24, fig. 37). In the last and the last but
two notopodia the crotchet stands alone, but in the others

ANATOMY AND CLASSIFICATION OF THE ARENICOLIDM. 447

it is accompanied by one, two, or three capillary sete. In
the segments anterior to them the crotchets are confined to
the neuropodia, the notopodia bearing only the capillary
setze described above (p. 445). Mesnil (1897) found a similar
condition in the last six to twelve segments of his specimens
of Clymenidesecaudatus (= Arenicola ecaudata), and
in the last six segments of his C.incertus. In his account
of the development of A. cristata, Wilson (1882) figures
a larva eight days old, which bears five paired groups of
sete, each of which groups contains a single crotchet along
with one to four capillary sete. The crotchet is figured,
however, distinctly ventral to the capillary sete, and may
belong to the neuropodium, as Wilson thought, though the
first three (and sometimes four) segments of the adult to
which these segments of the larva correspond are devoid
of neuropodia. As the single crotchet is present only in
the last formed, i.e. youngest notopodia of A. ecaudata,
and in recently formed segments of A. cristata, it there-
fore appears probable that for some time after its forma-
tion each notopodium bears a crotchet, but very soon the
crotchet is lost, and henceforward the notopodium bears capil-
lary sete only. It is interesting to note in Wilson’s figures
of the post-larve of A. cristata (1882, Pl. XXI, figs. 60, 61)
that each notopodium bears one laminated seta similar to
those of the post-larval A. marina described above (p. 445),
accompanied by one, two, or three ordinary capillary sete.
There are other examples of parapodia of polychetes bearing
both crotchets and capillary sete, e.g. the Capitellide. In
Notomastus (Hisig, 1887, p. 565) the segments of the
thorax bear laminated capillary setz similar to those described
above in the notopodia of the post-larval Arenicola marina
(p. 445), while the parapodia of the first eighty segments of
the abdomen bear both laminated capilliform sete and
crotchets. In Capitella (Hisig, 1887, pp. 565, 566), also,
laminated setz and crotchets occur together in the same
parapodium of one segment of the thorax. Thus, in young
specimens 1 mm. to 3 mm. long, they are present together in

448 F. W. GAMBLE AND J. H. ASHWORTH.

the fourth segment ; in specimens 3 mm. to 5 mm. long in the
fifth segment; in older specimens 5 mm. to 10 mm. long in
the sixth segment; and in adult specimens in the seventh
segment.

Neuropodial Chetz or Crotchets.—The neuropodial
cheetz, though exhibiting the same general form throughout
the genus, show more variation than the capillary sete in
their minor characters, not only in the different species but
in the same species at different ages; hence the chetee of a
given species do not present constant characters. It is,
therefore, difficult to determine by inspection of a given set
of cheete to which species of Arenicola they belong. Hach
crotchet consists of a shaft, generally somewhat curved, bear-
ing at its distal end a beak-like rostrum placed at an angle
to the shaft varying from about 70° to about 150°. There is
generally a slight dilatation of the shaft near the middle of
its length. Near the end of the cheta immediately behind
the rostrum there are in most specimens two or more minute
pointed teeth, the tips of which are directed towards the tip
of the rostrum, while below the rostrum, at the junction of
the rostrum and shaft, there is often a minute process which
corresponds in position to the more prominent process? or
tuft of hairs on the crotchets of the Maldanide.

The rostrum is comparatively short, and its tip is generally
rounded in medium-sized or large specimens, but it is larger
and its tip is sharply pointed in small specimens. ‘The teeth
are also better developed in chet obtained from young
specimens than in those from older ones.

By careful treatment with warm caustic potash solution
(about 5 per cent.) the entire band of neuropodial cheetee may
be isolated. It may then be seen that the new chete are
formed at the ventral end of the series, the rostrum
being first formed, then the teeth, and finally the shaft,
which is at first comparatively short (see figs. 9,18). The
neuropodia of young specimens contain very few crotchets

1 In the following description the terms teeth and process will be used
in the same sense as above.

ANATOMY AND CLASSIFICATION OF THE ARENICOLIDA. 449

(see Pl. 24, fig. 37), but in old specimens there is a very large
number of crotchets in each neuropodium. ‘T'wo of the
neuropodia of a large specimen of A. cristata (300 mm.
long) have been treated with caustic potash, and the entire
bands of cheetee isolated. Hach band contains 187 fully
formed chete, and about fifteen others in course of formation
at the ventral end of the series.

A. marina.—Crotchets of post-larval specimens (4°3 mm.
long) are ‘04 mm. to ‘05 mm. long, and bear two, or very
occasionally three, sharply marked teeth behind the rostrum,
and also a well-marked process ending in a long fine point
under the rostrum (fig. 8). In older specimens 17 mm. long,
which have assumed the adult characters and mode of life,
the crotchets are ‘1 mm. to ‘12 mm. long, and bear two well-
marked teeth but no process (fig. 11). Specimens about
100 mm. long have cheetze which are ‘4 mm. to ‘5 mm. long,
each of which bears two or three very small teeth and also a
small process (fig. 10). The crotchets of very large specimens,
especially those of the “ Laminarian” variety, may attain a
length of ‘8 mm. to’85 mm. From the time of their forma-
tion they are devoid of teeth, but bear a small rather blunt
process beneath the rostrum (fig. 9). It is interesting to
note that as the animal grows in size the rostrum of the
crotchet, which in the early stages is at right angles to the
shaft, in later formed chete makes a considerably greater
angle with the shaft, the angle increasing with the age of
the worm from which the chet are obtained, so that in a
cheta from a large worm, e.g. a Laminarian specimen about
250 mm. long, the angle between the rostrum and shaft is
almost 130° (cf. figs. 8—11). Concurrently there is a
reduction in the size of the teeth of successive generations
of chete; so that although in post-larval stages the teeth
are large and comparable to the rostrum in size, they are
entirely absent from the chetz of very old specimens
(cf. figs. 8, 9).

A. Claparedii.—The crotchets are nearly always strongly
curved, sometimes being bent almost into the form ot a

450 F. W. GAMBLE AND J. H. ASHWORTH.

semicircle (fig. 25). Hach bears about five small but clearly
marked and nearly uniform teeth and a minute process
(figs. 24, 25). The chet are slender, and never attain a
very great size, ‘4 mm. (in a specimen 100 mm. long) being
the extreme length attained in any of our specimens.

A. cristata.—The crotchets of this species, especially of
young specimens, are very similar to those of A. marina,
except that the distal end is broader and more curved on the
side opposite the rostrum. Full-grown chetze from a young
specimen 47°5 mm. in length are ‘2 mm. to ‘*3 mm. long.
Hach bears five or six teeth, the first of which (the one
nearest the rostrum) is the largest, the others gradually
decreasing in size (fig. 15). The same change in the angle
of the rostrum is also seen in this species as the specimens
increase in size. The rostrum of the cheta described above
makes an angle of about 110° with the shaft. Fig. 16
represents a seta from a specimen 120 mm. long, in which
there are faint indications of three or four teeth, and the
rostrum makes an angle of about 130° with the shaft. An
unworn cheta from a very large specimen (300 mn. long) is
represented in fig. 17. The cheta bears two very small
teeth and a very minute process. This rostrum and the shaft
are nearly in a straight line, the angle between the two
being about 150°. The cheetz of this species are very long,
the full-grown ones of the large American specimen (360 mm.
long) reaching ‘9 mm. in length. The teeth being so small
are very early worn away, so that if the chete have been in
use they are entirely devoid of teeth, and then closely
resemble those of the large Laminarian specimens of A.
marina, the only characters distinguishing the two being
the curvature of the back of the cheta of A. cristata
(ch tiess O27).

A. ecaudata and A. Grubii.—The neuropodial crotchets,
like the notopodial setz, of these two species are so closely
similar that no constant point of difference can be detected.
The shaft of each crotchet bears a moderately long rostrum,
tapering somewhat towards its point, behind which are two

ANATOMY AND CLASSIFICATION OF THE ARENICOLIDA. 451

or three teeth. In older chet there is often also a very
slight process beneath the rostrum (see figs. 18, 22).

The crotchets of a specimen of A. ecaudata 7:2 mm.
long are about ‘05 mm. long (fig. 19). Hach bears a curved,
pointed, beak-like rostrum, placed at right angles to the
shaft of the cheta, and two large teeth behind it. In some
specimens there is a short pointed process beneath the
rostrum, but this does not appear to be constant. On com-
paring these cheetee with those of older specimens it will be
seen that the same change takes place in the inclination of
the rostrum to the shaft as is described above in A. marina
and A. cristata (see figs. 18 and 19).

The crotchets of A. ecaudata and of A. Grubii never
attain a very great length ; at any rate, the largest cheetz in
our specimens are only one third of a millimetre in length (in
worms 200 mm. long).

In order that the characters of the chete as above
described may be accurately determined, it is necessary to
examine unworn specimens; especially is this precaution
necessary in the neuropodial cheete of medium-sized or large
specimens, in which the teeth behind the rostrum, being very
small, are worn away very soon after the cheetz come into use.
It is therefore best to examine cheete: which have not yet
come into use, and this may be readily done. After isolating
the entire band of neuropodial cheetz by the use of warm caustic
potash solution, the cheete in the ventral portion of the band
should be examined. Besides the cheetee in course of forma-
tion, one or two fully developed crotchets which have not yet
come into action may be usually seen, and these should be
selected for observation of their characters, since they are
uninjured by wear. Especial care is also required in the case
of the notopodial sete of A. ecaudataand A. Grubii, in
which the hair-like processes are very small and soon worn
away.

vou. 43, PART 3,—NEW SERIES, i

452 F. W. GAMBLE AND J. H. ASHWORTH.

5. Epidermis.

The “cuticle” is well developed in all species of A renicola,
but perhaps most abundantly in A. ecaudata and Grubii.
It is formed by the mucus cells of the epidermis. In
post-larval specimens of the common lugworm the “ cuticle”
forms a distinct gelatinous envelope or tube, which in-
vests the body closely and does not impede the swimming
movements, but appears to bend with each undulation and to
be readily cast off. In post-larval A. cristata the envelope
is described as “small masses of a soft gelatinous substance
in which the animals creep actively about” (Wilson, 1883).
In A. ecaudata at the abranchiate stage a similar tube is
formed, and is attached to algz (Fauvel, 1899), but this is dis-
puted by Mesnil. The cells which secrete this covering are
at first confined to certain broad bands which alternate with
non-glandular zones. Rough handling of adult specimens
of A. ecaudata and A. Grubii induces an increased forma-
tion of this mucous secretion, accompanied by a yellow colour-
ing matter which readily stains the hands. There are, in
fact, two kinds of pigment,—a yellow (orin adult A. marina
green) pigment, soluble to some extent in sea water and
especially in alcohol, and probably of lipochrome nature ; and
an insoluble black pigment resembling melanin in its resist-
ance to solution. Both these appear in early post-larve, to
which they give a characteristic colour. We have not,
however, examined these pigments in detail. In adult
specimens of A. Grubii and A. ecaudata the epidermis is
produced into ridges and furrows, resulting in the annulation
and areolation of the skin. In the ridges the mucus cells
are abundant, in the furrows they are absent; but in both
positions the long cylindrical epidermal cells are almost filled
with granules of an insoluble brown pigment, which appears
black in the aggregate. They extend on to the prostomium, and,
in fact, are present all over the epidermis, though to a less
extent in the nuchal groove than elsewhere. In A. Grubii
masses of this melanin-like pigment are actually found in

ANATOMY AND CLASSIFICATION OF THE ARENICOLIDA. 4538

the brain and in the thickness of the body-wall. The appear-
ance of these brown granules is very similar to those of the
secretory portion of the nephridia, but until the micro-
chemistry of each set of granules is known, it is impossible
to do more than suggest that the skin may in Arenicola act
as an excretory organ. In A. marina, A. Claparedii, and
A. cristata the furrows between the annular ridges are free
from pigment, and contain few or no gland cells.

The remaining elements of the epidermis are sensory and
nervous, and are dealt with under their respective sections.

Beneath the epidermis there is a slight connective tissue
which accompanies the nerves, the subdermal extensions of
the ccelom, and the superficial capillaries, which (e. g. in
A. marina) may penetrate between the bases of the epidermal
cells.

6. Musculature.

Tn all species the muscles of the body-wall are similar to
those of A. marina. Immediately beneath the epidermis
there is a layer of circular muscles, and beneath this are the
bands of longitudinal muscle-fibres, which are well developed
in A. Grubiiand A. ecaudata.

Kach bundle of notopodial sete is enclosed in a sac, to
the inner end of which are attached (1) a single retractor
muscle strand, which is inserted into the body-wall at the
sides of the nerve-cord ; (2) six to ten protractor muscles,
which are inserted in the sides of the body at the level of
the setal sac.

The musculature of the buccal mass is well developed in
A. Grubiiand A. ecaudata, forming an almost complete
sheath round the pharynx. ‘The muscles forming this sheath
arise from the longitudinal layer in the region of the first
diaphragm, and are inserted into the anterior region of the
proboscis. They are not quite so well developed in A.
cristata and A. Claparedii.

The muscular fibres are essentially composed of a central

454 F. W. GAMBLE AND J. H. ASHWORTH.

protoplasmic medulla and a contractile cortex which stains
more deeply.

The oblique muscles, which divide the body-cavity into
three portions, vary considerably in their development in
the various species. In this respect A. cristata agrees
most closely with A. marina (see dissection of A. cristata,
fig. 30, and compare with that of A. marina, PI. 2, fig. 5, of
our former paper, 1898). In this species the oblique muscles
commence behind the third diaphragm, and are present
to the end of the tail. They are usually thin, moderately
broad bands, arising at each side of the nerve-cord, and
inserted right and left into the body-wall at the level of
the setal sacs. They partially cover and bind down the
nephridia.

In A. Claparedii these muscles are present in the
same region, but are not so well developed, and they bind
down the nephridia to a far less extent. They are omitted
from the drawing of the dissection in fig. 26.

Oblique muscles are absent from the anterior portion of
A. ecaudata and A, Grubii, in front of the second or third
gills. Behind this point they are feebly developed, the
muscle bands being very thin and narrow (about ;—} mm.
wide), but are present to the end of the body. The absence
of oblique muscle bands in the nephridial region is a most
striking difference between these two and the other three
species of Arenicola. In consequence of this absence of
oblique muscles in these two species, the nephridia with their
nephrostomes, and, in the case of A. ecaudata, the ovarian
processes or spermatic sacs, are clearly visible on opening the

body (Pl. 25, fig. 45).

7. General Anatomy of the Internal Organs
(figs. 26, 30, 44, 45).

The general arrangement of the organs, as seen after open-
ing the body-cavity by a dorsal and median incision, is in all
species similar to that of A. marina, except that in fully

ANATOMY AND CLASSIFICATION OF THE ARENICOLID®. 450

mature A. ecaudata the ovaries or testes are so voluminous
as to conceal the greater part of the nephridia and the
alimentary canal. There are the usual three anterior dia-
phragms placed exactly as in A. marina, the first being
oblique and inserted dorsally, one annulus in front of the first
notopodium, ventrally just behind the first neuropodium ;
while the second and third are placed vertically, two annul
behind the second and third parapodia respectively. From
this point the coelom is uninterrupted by septa for a con-
siderable distance. The septa, in fact, are reduced to
strands of connective tissue binding together the afferent
and efferent vessels which are connected with the nephridia,
and in the “marina” section with the anterior gills. This
tissue increases in amount so as to form a complete septum
opposite the last gillof A. Claparedii and A. cristata, and
regularly between the caudal segments in these forms (figs.
26,30). In A. ecaudata and A, Grubii the complete
septacommence at the beginning of the branchial region, and
are continued to the end of the body (Pl. 25, figs. 44, 45). In
these species also the tissue supporting each of the vessels
going to the nephridia from the ventral vessel may be
regarded as an incomplete septum, since it is expanded peri-
pherally, and inserted partly into the nephridium and partly
into the body-wall in the region of the second groove behind
the cheetigerous annulus—the usual limit of the segments.

The first diaphragm in A. cristata, A. ecaudata, and A.
Grubii is stout, and produced backwards into a pair of long,
finger-shaped, contractile vascular sacs, 5 to 12 mm. long,
which lie at the sides of and slightly ventral to the cesopha-
gus. ‘These diaphragmatic pouches are entirely absent in A,
Claparedii. On opening specimens which are sexually mature
a mass of spermatozoa or ova is often found in connection
with the third diaphragm. ‘The genital products accumulate
either in front of, or more usually behind the diaphragm, and
cause it to become distended, forming a pouch, or often two
pouches or sacs, one on each side of the alimentary canal.

In A. cristata there is, in the tail, a well-marked dorsal

456 F, W. GAMBLE AND J. H. ASHWORTH.

mesentery, connecting the alimentary canal to the body-wall
(see fig. 30, Mes. D.). In A. Grubii, A. ecaudata, and A.
cristata there are, immediately behind the heart, two small
strands, which look almost like thin nerves, but which are
composed of connective tissue, which arise from the ventral
walls of the stomach, and are inserted into the body-wall on
each side of the nerve-cord (Pl. 25, fig. 44). During diges-
tion the stomach is swung to and fro by the movements of the
body, and the function of these strands of connective tissue
is probably to prevent the amplitude of the swing from being
too great, and causing the rupture of some of the delicate
branches of the ventral vessel, the main trunk of which is
attached to and moves with the alimentary canal. It will be
noticed that these strands (see fig. 44, Conn. Tiss.) are placed
at the boundary of the segment.'

8. Alimentary Canal.

The alimentary canal of the four species at present under
consideration varies only in a few details from that of A.
marina. In each there is (1) an eversible buccal mass or
“ nroboscis,” generally pinkish in colour owing to its contained
blood-vessels; (2) an cesophagus, brownish or pinkish in
colour, and often somewhat transversely wrinkled, bearing
glandular pouches just behind the level of the third dia-
phragm ; (3) a gastric region with yellow glandular walls and
numerous blood-vessels, extending from the level of the heart
to about that of the eleventh or twelfth sete (sixteenth in A.
ecaudata) ; and (4) an intestine, generally dark brown or
dark olive-green in colour, extending to the posterior end and
opening at the terminal anus.

The alimentary canal of A.cristata very closely resembles
that of A. marina, the only difference being that in the
former the cesophageal pouches are relatively small. In
A. ecaudata the pharyngeal portion of the alimentary canal
is longer than in A. marina, due to the fact that in the

1 See foot-note on p. 519 re A. marina.

ANATOMY AND CLASSIFICATION OF THE ARENICOLIDAH. 457

former species the anterior achztous region of the body is
longer. The cesophageal pouches in this species and in A.
Grubii are definitely divided into a globular anterior portion
and a thinner hollow stalk, by which they communicate with
the cavity of the cesophagus (figs. 44, 45). The pouches con-
tain a neutral greenish liquid, but they often have a pink
tinge owing to the large amount of blood contained in their
walls. The intestine of A. Grubii and A. ecaudata is not
drawn out asin A. marina into lateral wings by the septa
of the posterior portion of the animal, but is of almost
uniform diameter throughout (see fig. 44).

There is one constant and striking point of difference
between the alimentary canal of A. Claparedii and that of
any other species, viz. the presence of multiple cesophageal
pouches. ‘These are placed in the usual position on the ceso-
phagus, about midway between the third diaphragm and the
heart,and are different in shape from those of any other species.
Sometimes they are little more than hollow papille about
2 mm. in length; more usually they are finger-shaped, and
may be even more elongated, almost filiform structures, at-
taining a length of about 10 mm. to 12mm. They often have
a moniliform appearance (see figs. 26 to 28). In the specimen
drawn in the dissection there are two pouches on each side,
an inner smaller one about 3 mm. long, and an outer one
about 5 mm. long. There are generally, however, three or
four pouches on each side of the cesophagus, and there may
be, as in a specimen from California, fifteen pouches altogether
(fig. 28). The vessels on the intestine are rather differently
arranged in this species (see fig. 26).

The hairy-looking, dark brown, chlorogenous tissue present
in considerable quantity, especially on the ventral vessel in
A. marina (see Gamble and Ashworth, 1898, Pl. 2, fig. 5), is
present in A. cristata in the posterior half of the gill region,
forming small tufts on the oblique muscle bands. In the
other three species it is either altogether absent or feebly
developed (Pl. 26, fig. 54).

The histological features of the various portions of the

458 F. W. GAMBLE AND J. H. ASHWORTH.

alimentary canal are almost identical with those of A. marina.
The cavity of the cesophageal pouches is partially subdivided
by numerous incomplete septa, produced by infolding of
the wall of the pouch. The septa are covered by colum-
nar cells, among which are glandular cells. In each septum
between the epithelial lamelle is a cavity filled with
blood. The gland cells of the stomach are very obvious
in all species. There is a well-marked ventral groove,
commencing about the middle of the stomach, and con-
tinuing backwards to the anus. In the stomach and an-
terior part of the intestine there are, opening into this
groove on each side, oblique grooves which are situated on
the side walls of the alimentary canal, the general direction
of which is downwards and backwards. The cells lining all
these grooves are ciliated, and produce currents towards the
anus.

The anus is not surrounded by processes or by a special
cone-like arrangement as in the Maldanide, but is merely
bordered by simple papille.

The exact nature of the food and the mode by which it is
extracted from the sand and débris, and rendered available
for absorption, are problems upon which we can throw little
light. The great abundance of Arenicola wherever the
sand, mud, or gravel contains a large proportion of decom-
posing matter or sewerage, and its absence from long stretches
of coast where the beach is clean sand, show that these
animals feed on decaying animal or vegetable matter.

9. Vascular System (Pl. 24, figs. 26, 30; Pl. 25,
figs. 44, 45).

Milne-Edwards (1838) figured and described the chief parts
of the circulatory system of a specimen of A. marina, which,
however, possessed only five pairs of nephridia, the first pair
being absent. His figures, while on the whole correct, are in
error in showing the heart in direct connection with the dorsal
vessel. Cosmovici (1880) has also described and figured the
vascular system of the anterior portion of this species. He

ANATOMY AND CLASSIFICATION OF THE ARENICOLIDA. 459

has correctly shown the heart and its relations to the neigh-
bouring vessels, and has also figured the blood-vessels of the
alimentary canal and the nephridia. Jaquet (1886) has
described the vascular system of A. Claparedii, but through-
out his memoir he refers to this species as A. marina,
although the distinction between these two species had been
pointed out some time before by Levinsen (1883). In our
paper on A. marina (1898)! we have fully described and
figured the vascular system of this species, and still more
recently, since our account and figures for the present memoir
were completed, Fauvel (1899) has published a short account
of the circulatory system of A. ecaudata.

The vascular system of A. Grubii (except a figure of the
vessels of asingle segment by Claparéde, 1868, pl. xix, fig. 2)
and A. cristata has not hitherto been described or figured.

The circulatory system is similar in its general arrange-
ment throughout the Arenicolide.

The dorsal vessel arises near the anus and runs forwards
on the alimentary canal to the anterior end, where it breaks
up into small vessels and capillaries. It contracts fairly
regularly from behind forwards. In its course forward the
dorsal vessel gives off intestinal vessels, each of which runs
round the intestine and opens into the ventral vessel. In
the gill-bearing region, in A. Grubii and A. ecaudata, the
dorsal vessel receives an efferent vessel from each gill, while
in A. cristata and A. Claparedii (as in A. marina) only
seven pairs of the posterior gills send efferent branches to the
dorsal vessel. Between consecutive efferent branchial vessels
there are two or three pairs of intestinal vessels. From the
point at which the dorsal vessel receives the most anterior
efferent branchial vessel to the cesophageal pouches, the
dorsal vessel receives no segmental vessels, but numerous
branches of the gastric plexus open into it.

The dorsal vessel has no direct communication with the
heart.

In front of the heart the dorsal vessel receives on each

' See foot-note on p. 519.

460 F. W. GAMBLE AND J. H. ASHWORTH.

side (1) small vessels from the cesophageal pouches (except in
A. Claparedii), (2) vessels from the anterior nephridia (see
figs. 26, 30, 44, 45), (3) on reaching the third diaphragm a
vessel from the third chetigerous sac and body-wall, and (4)
on reaching the second diaphragm, one from the second
cheetigerous sac and body-wall. The dorsal vessel runs for-
ward, pierces the first diaphragm, and then breaks up into
capillaries, supplying the buccal muscles, prostomium, and
otocysts.

The blood from these parts is collected into capillaries
which unite to form the ventral vessel, which, soon after its
origin, gives off a median vessel to the first diaphragm and,
when present, its pouches: while just behind this, in A.
cristata and A. Claparedii, it gives off a pair of vessels
to the second setal sacs and body-wall. A little further back
it supplies a median branch to the second diaphragm and
nerve-cord, and another to the third diaphragm, the cord and
first nephridium (and in A. Grubii and A. ecaudata a
median vessel to the cord about the level of the first
nephridium). From this point the ventral vessel as it pro-
ceeds backwards supplies the chetigerous sacs, body-wall,
nephridia, and gills (if present) by large segmentally arranged
branches. The first and second nephridia of A. Grubii and
A. ecaudata do not receive a branch from the ventral vessel.

The difference of opinion which has existed on the subject
of the nature of the blood-supply of the stomach and intestine
appears susceptible of a very simple explanation. The earlier
writers described this supply as a plexus of minute vessels,
later authors as a continuous sinus, only parts of which are
visible between the chlorogogenous areole. Benham (18938),
however, showed that in the post-larval stage of A. marina
there was a feebly developed plexus, but no sinus, and we
are able to show by the examination of a large number of
specimens of this species, that up to a length of 50 mm., or
even more, the plexus increases, and only here and there
(e.g. in the walls of the cesophageal pouches) fuses to form a
‘“sinus.’ As the lugworm increases in size this formation of

ANATOMY AND CLASSIFICATION OF THB ARENICOLIDA. 461

sinuses becomes more and more marked, until in specimens
several inches long the stomach may be considered as lying
in a gastric sinus, from which, however, the dorsal vessel is
distinct from the commencement. Presumably during this
sinus formation the endothelial linings of the previously dis-
tinct capillaries unite and fuse, at least we have as good
evidence of their presence in the later as in the’earlier stages
of the process.1

The gastric plexus consists, then, at first of a network of
vessels, later on of a sinus.

Two vessels of the plexus which are ventrally situated are
known as the subintestinal vessels. They commence just
behind the heart, and run backwards to the level at which the
first efferent branchial vessel joins the dorsal vessel ; behind
this point they gradually taper and disappear. Hach receives,
in A. marina and in A. Claparedii, six vessels, and in A.
cristata four vessels, from the nephridia and gills situated
in segments 7—12 and 7—10 respectively. The subintestinal
vessels are the most ventral part of the gastric plexus, and
they communicate, by means of the ventro-lateral vessels of
the plexus, with the lateral gastric vessel, and so with the
heart. In A. Grubii and A. ecaudata the subintestinal
vessels are small, and receive no vessels from the nephridia
or gills.

The gastric vessel receives blood from the dorsal vessel
and from the subintestinal vessels by means of the branches
of the gastric plexus. It is usually first distinguishable pos-
teriorly about the middle of the length of the stomach, and
becomes more clearly differentiated as it proceeds anteriorly.
It opens into the “ auricle,” which is a thin-walled expansion,
probably of the gastric vessel. After giving off the lateral
cesophageal vessel the auricle opens into the ventricle, the
walls of which are muscular, and by their contraction drive
the blood into the ventral vessel.

The lateral cesophageal vessel gives off a moderately

1 Some authors (Fauvel, 1899) deny the presence of any endothelium, and
state that the gastric sinus exists as such from its formation.

4.62 F. W. GAMBLE AND J. H. ASHWORTH.

large branch (not yet traced in A. Claparedii) to the ceso-
phageal pouch, and then runs forwards supplying the lateral
walls of the cesophagus, breaking up into capillaries near the
second diaphragm. On each side of the nerve-cord there is a
small vessel, which accompanies the cord along the whole
length of the body. In front the neural vessels arise in the
triangular area between the cesophageal nerve connectives by
the union of capillaries from the ventral region of the oto-
cysts. They receive several branches from the ventral vessel
(see above). From these neural vessels small branches are
given off which supply the body-wall in their vicinity.

The vessels of the body-wall are much more highly de-
veloped in A. Grubii and A. ecaudata (and especially in
the former) than in A.marina. There are two chief vessels :
(1) a dorsal longitudinal, or parietal vessel, which runs along
the whole length of the body, except at the extreme anterior
end, at the level of the insertion of the notopodial sete; (2)
a nephridial longitudinal vessel, which is present only in and
immediately in front of and behind the nephridial region, and
runs just ventral to the level of the nephridiopores. An-
teriorly the parietal vessel is distinguishable just behind the
first sete, and the nephridial vessel immediately behind the
second diaphragm, where the two are united by a transverse
connection (Pl. 25, fig. 44). The two vessels run parallel to
each other through the nephridial region, but behind this the
nephridial vessel gradually decreases in size, and in the
anterior part of the gill region (about the level of the second
or third gill) disappears entirely. The dorsal longitudinal,
or parietal vessel receives blood chiefly from the afferent
nephridial vessels. These arise from the ventral, vessel, and
on approaching the nephridium bifurcate, one branch passing
to this organ and the other going to the parietal vessel. An-
teriorly the parietal vessel on each side is connected to the
dorsal vessel by the branch which supplies the first nephridium.
The second nephridium is supplied with blood by a small
branch from the parietal vessel. In A. Grubii the afferent
vessels situated in the three segments following the last

ANATOMY AND CLASSIFICATION OF THE ARENICOLID™. 463

nephridial segment bifurcate near the body-wall, each sending
one branch to the parietal and the other to the nephridial
vessel (see fig. 44). A further account of the relation of
these vessels to the nephridia is elven in the section on
nephridia (p. 517).

In A. marina and A. cristata there is a well-marked
parietal vessel, which runs from the region of the first seta
almost to the posterior end of the body, but the nephridial
vessel is small and difficult to trace. We have not been able
to follow these vessels in A. Claparedii, of which we have only
spirit specimens at our disposal. Judging from sections of
this species, both the parietal and nephridial vessels are very
feebly developed.

The hearts are a pair of contractile bulbs connecting the
gastric and ventral vessels. There is a considerable differ-
ence in the size of this organ in the various species. In A.
marina and A. cristata (fig. 30) the heart is a large organ,
the ventricle especially being capable of great dilatation. In
A. Grubiiand A, ecaudata it is small even at the moment
of diastole (see figs. 44, 45), while at the close of systole it igs
little more than a rhomboidal enlargement at the junction of
gastric and lateral cesophageal vessels. In A.Grubii and A.
ecaudata, even more so than in A. marina, the vascular
system clearly indicates the true segmentation of the body.
An inspection of the drawing of the dissection of A. Grubii
(Pl. 25, fig. 44) will show this point at once.

The blood-corpuscles of all the species are very much alike.
They are minute nucleated, rounded, or ellipsoidal cells from
5a to 10 in length (fig. 40), and in comparison with the
complexity of the vascular system and the large quantity of
blood are very sparsely scattered. ‘Their mode of origin is
unknown.

The Heart-body.—tThe structure of the heart-body re-
quires separate consideration. Though absent in A. Clapa-
redii and A. cristata, this organ is well developed in the re-
maining species. In post-larval and young specimens of A.
marina the heart contains no trace of this body, but it has ap-

464. F, W. GAMBLE AND J. H. ASHWORTH.

peared in examples measuring 65 mm. inlength. At this stage
of growth, the wall of the heart consists of an outer peritoneal
cubical epithelium and an inner but indistinct endothelium.
Between these two layers it is not possible to detect any mus-
cular tissue. The cavity of the heart is, however, invaded by
strands of cells which repeat the structure of the heart wall,
and are probably invaginations of it. In A. Grubii the in-
vagination is clearly marked (figs. 38, 39). Later on, as the
muscular tissue develops in the wall of the heart, fresh
invaginations occur, composed of an extremely delicate en-
dothelium, a muscular layer, and a mass of cells, some
granular, some glandular, forming a fairly definite lining to
the invagination, but projecting at their free ends into an
irregular lumen (PI. 25, figs. 41—43), partially blocked up
by cells within which yellowish or yellowish-brown granules
may be seen. The cells cannot, however, be said to form a
medullary layer. In some places the granules are larger,
and united into a spherical mass lying in a vacuole; in
others very minute and scattered (fig. 43). They agree
in appearance with the chlorogogen granules of the peri-
toneum.

In A. Grubii, 140 mm. long, the first traces of the heart-
body are found as a few short and apparently solid ingrowths
of the muscular and peritoneal layers of the heart wall (fig.
38). These ingrowths occur on the posterior (and to some
extent outer) surface of the heart, where the muscular layer is
specially developed ; elsewhere it is indistinct. The granular
chlorogogenous bodies are in this way carried into the cavity
of the heart. A distinct endothelium forming the outer wall
of the process can in some cases be detected with certainty
(fig. 41). Within this there was a muscular layer, while the
centre of the process is formed by somewhat cubical peri-
toneal cells arranged in a network rather than as a distinct
cortex, and between them muscular fibres are occasionally
seen (figs. 41—43). The outlines of the more centrally
placed cells are somewhat difficult to make out. Within
these cells fine yellowish-brown granules occur, the larger

ANATOMY AND CLASSIFICATION OF THE ARENICOLIDM. 465

ones heaped together as in A. marina. In addition to these
there are colourless vacuolated and granular cells.

Tn older specimens (200 mm. long) the number of ingrowths
from the posterior wall of the heart has increased. A few
are also developed from the opposite wall, and in these the
neck of the involution is hollow, showing the nature of the
ingrowth, involving, as it does, the entire thickness of the
wall of the heart, and a virtual extension of the ccelom into
the processes (Pl. 25, fig. 42).

In A. ecaudata the appearance of the heart-body is very
similar to that of A. Grubii. It is not present in post-
larvee (7°2 and 9:5 mm. long), but in worms 120 and 150 mm.
long it is well developed. In places the outer wall appears
to consist of an endothelium, then follows the muscular layer,
and finally the peritoneal cubical cells, which form an irre-
gular outer layer, within which are scattered granular and
glandular cells, the former with the usual yellow chloro-
gogenous bodies.

The suggestion, first made by Hisig (1887), as to the
nature of the heart-body, and lately confirmed for Cirratulide
by Picton (1898), namely, that this body is a modified
portion of the peritoneal tissue, receives further support
from these observations on Arenicola, but it is necessary
to discuss this conclusion more fully.

In Terebellids and Cirratulids, Picton (1898) came to the
following results. ‘The heart-body is developed by an invo-
lution of the anterior end of the dorsal vessel on its under
surface, and first makes its appearance in Terebellid larve
15 cm. in length. Probably by proliferation of the ingrowth
the body increases in extent, and a secondary lumen appears
in its later strands. In the adult “ the organ is enclosed in
an endothelium, within which cortex and medulla, seen, e. g.,
in Audouinia, are not distinguishable, but the elongated
cells of which the structure is composed form a sort of
network, radiating out from the central axis. There is no
great lumen, but numerous intercellular spaces appear. The
pigment granules are of a greenish-yellow colour, and each

466 F. W. GAMBLE AND J. H. ASHWORTH.

is usually surrounded by a vacuole” (Picton, 1898, p.
289).

This quotation is applicable word for word to the structure
of the heart-body of Arenicola Grubii, so that in this
respect and also in its mode of origin the heart-body,
although absent in A. cristata and A. Claparedii, showsa
close agreement with certain Terebellids (Lanice conchi-
lega, Polymnia nebulosa). Only in its point of origin
does it differ conspicuously from all other Polychetes, in
which it is always unpaired and usually in the dorsal vessel,!
whilst in Arenicola it is formed in each of the paired
contractile “hearts”? which unite the gastric plexus or sinus
and the ventral vessel. There is, of course, no a priori
reason why an involution, followed by proliferation and
resulting in a “ heart-body,” should not occur on any of the
larger vessels, unless its occurrence is determined by some
mechanical function which it may subserve. Now in
Ampharetide (Fauvel [1897] ), Terebellidee, and Cirratulide,
a short dorsal vessel arises from the gastric sinus, and ends
by giving off pairs of branchial vessels, and both Picton and
Fauvel have concluded by direct observation that the heart-
body ensures the whole of the blood at each systole passing
on to the gills. In Arenicola, however, its function cannot
be thus explained. There is no cardiac body in the dorsal
or ventral vessel in the branchial region or on any part of
their course, but only on the vessel connecting on each side
the gastric plexus and the ventral vessel. The heart-body,
in fact, appears to be a means of preventing regurgitation of
the blood into the gastric plexus after systole, and of ensuring
its passage into the ventral vessel. Whether, in addition, it
performs important excretory functions can only be decided
when more data shall have been collected on the nature of
the substances collectively termed chloragogen.

1 In Pectinaria Claparéde and Wirén have described a cardiac body in
the ventral vessel,

ANATOMY AND CLASSIFICATION OF THE ARENICOLIDM. 467

10. Ccelom.

The ccelom of A.marinaand A. cristata is very spacious,
that of A. Claparedii moderately so, but in A. Grubii and
A. ecaudata it is comparatively small. Asin A, marina
the middle region of the body is devoid of septa, but, as
noticed above, there are structures in A. Grubii which may
be regarded as rudimentary septa, viz. the thin sheet of con-
nective tissue which supports the afferent nephridial vessel
on its course from the ventral vessel to the nephridium (PI.
26, figs. 53, 54). In all species there are in the posterior
region of the animal septa only incomplete ventrally.

In the fresh condition A. Grubii and A. ecaudata show
the peristaltic waves which pass along the body from behind
forwards even better than A. marina. As pointed out in
our account of A. marina (1898) this peristaltic motion is of
considerable importance in promoting the efficient circulation
of fluid in the coelom; in inflating the anterior portion, thus
aiding in burrowing; in assisting the gut muscles to cause
the backward motion of the sand in the alimentary canal ;
and in assisting defeecation.

The ccelomic fluid of all species resembles that of A.
marina. It contains ccelomic cells and reproductive pro-
ducts. Coelomic cells are tolerably abundant in all species, and
consist of fusiform cells about 40 u in length, and smaller
more spherical or amceboid cells. On the coagulation of the
ccelomic fluid, which occurs very soon after its exposure to
the air, the fusiform cells and to a less extent the amoeboid
cells unite with the fibrous network which is formed during
coagulation to forma clot. Fusiform cells are fewest in our
specimens of A. cristata, and most abundant in A. Grubii.

Instead of floating freely in the ccelom, a great proportion
of the gonads present in the ccelomic fluid accumulate in
the space between the oblique muscles and the body-wall.
In A. Grubii and A. ecaudata they accumulate in the
posterior region of the body, well behind the nephridia.

The ccelom is lined throughout by a layer of flattened

VOL. 43, PAR! 3,—NEW SERIES. KK

4.68 F. W. GAMBLE AND J. H. ASHWORTH.

endothelial cells,! which apparently arise from the same
embryonic tissue from which the longitudinal muscles are
developed. The material at our disposal is, however, not
young enough to enable us to trace the details of the process.

11. Nervous System.

Methods.—Examination of the fresh nerve-cord of
Arenicola is not of great use (except for the study of the
“giant-fibres”) on account of the pigment and_blood-
capillaries. We have tried a number of the modern methods
for determining the course of the nerve-fibres and the
histology of the cellular and fibrous parts of the cord, and
the results of these trials are given below.

Numerous attempts to obtain staining of the elements
(particularly the giant-fibres and giant-cells) of the cord
by methylene blue were ineffectual. The same _ process
applied to Nereis or Polynoé resulted in a selective
staining, which at the present time, fourteen months after
the colour was fixed by Bethe’s ammonium molybdate method,
is as sharp as it was when the preparations were first made.
But though we tried three species of Arenicola and varied
the process in several ways only a very few preparations
were at all successful, and in none of these could we trace
the origin of the giant-fibres from cells of the cord or brain,
Impregnation by Golgi’s rapid method was given a trial,
but, as other workers have discovered, this method rarely
gives satisfactory results with marine objects. Most of our
observations are based on sections fixed with the corrosive-
acetic mixture and stained with iron-hematoxylin, but for
comparison with Apathy’s (1897) results, we have employed
the hematein stain 1 a of this author (the details of the
recipe are given in the treatise 1897, pp. 710-16). For
differentiating the giant-fibres and other stout tracts, vom
Rath’s picro-osmic-acetic mixture was tried, since both Lewis

1 The appearances presented by this endothelium from different parts of
the ceelom have been figured and described in Arenicola marina by
Viallanes (‘ Ann. Sci. Nat.,’ ser. 6, vol. xx, 1886).

ANATOMY AND CLASSIFICATION OF THE ARENICOLIDA. 4.69

(1898) and Hamaker (1898) have obtained good results on
Polychztes by its use. The cord after fixation and washing
was treated with pyroligneous acid or with pyrogallol until
quite blackened. It was then hardened and cut, but the
results were inferior to those obtained by fixing with the
corrosive-acetic mixture and subsequent staining by one of
the hematoxylin solutions.

There are the usual components of the nervous system in
Arenicola, the “brain,” the circumcesophageal connectives,
the stomogastric system, the ventral cord, and the peripheral
nerves. Professor Ehlers (1893) has described the general
form of the brain in A. marina, A. Claparedii, and A.
Grubii; and Retzius (1891) has figured one or two examples
of the nerve elements stained with methylene blue, but there
has been very little work published on the minute histology
of the nervous system. We propose in this section to go
rather more into the detail of this subject than we have done
in the other organs.

ie Bre <eBaranm 2% eels).

As with so many organs, the structure and form of the brain
follow one modification in the “marina” section of the genus,
another in A. ecaudata and A. Grubii. Both, however,
belong to the same plan, and thanks to the comparative work
by Racovitza, Retzius, and others, it is now possible to regard
this plan of cerebral structure as common to all Polychetes,
although there is still much difference of opinion as to the
relative importance of many structural details. According to
Racovitza (1896) this common plan may be considered to be
composed (1) of a pair of anterior lobes connected with the
epidermis at the point of origin of the median or paired
prostomial palps ; (2) of a median or secondarily subdivided
middle region connected with the upper surface, of the pros-
tomium, and the sense-organs (eyes) borne on that surface ;
(8) a pair of postero-dorsal lobes continuous with the epi-
dermal invaginations which form the ciliated grooves or
nuchal organs. According to this view the brain is regarded

470 F, We GAMBLE AND J. H. ASHWORTH.

as having been formed exclusively by the fusion of sensory
areas which at first were simply modified portions of the
prostomial epidermis, and which in all Polycheetes develop in
connection with it, while in some the connection is retained
throughout life.

These sensory lobes, however, do not constitute the entire
brain even of such forms as Arenicola. In addition there
are tracts arising from groups of cells in the brain which
traverse the connectives round the cesophagus and extend
into the cord, and may even terminate peripherally. Although
we know comparatively little of the course of these fibres,
the cells from which they spring must be included in any
complete explanation of the origin of the brain. Racovitza,
however, takes no cognizance of them, and in this respect his
explanation of the brain of Polychetes is incomplete, and
his fundamental plan incomplete also. Yet in spite of this
the plan is one with which the brain of Arenicola may be
usefully compared.

In the “marina” section there are two pairs of lobes, an-
terior and posterior, connected by an intermediate region
which partakes histologically of the characters of both. The
anterior lobes are specially related to the front end of the
prostomium, and the cesophageal connectives are given off
from them. ‘lhe posterior lobes are as closely connected
with the ciliated groove or nuchal organ. The intermediate
region supplies the upper surface of the prostomium.

In the two species, A. ecaudata and A. Grubii, this differ-
entiation is absent. ‘he brain is commissural in form, and
merely unites the ends of the esophageal connectives. Some-
times a posterior expansion underlies the ciliated groove, but
as a rule this is suppled by several of the branches, which
are rather cerebral nerves than lobes. ‘This simplification of
brain structure, as Racovitza has pointed out, corresponds with
the simpler character of the prostomium in these species.

The brain of young specimens (50 to 75 mm. long) of
A. marina is pyriform, the broader end being anterior. It
might, however, be more correctly described as roughly

ANATOMY AND CLASSIFICATION OF THE ARENICOLIDE. 471

T-shaped. It is hollowed out by ccelomic spaces accom-
panied by blood-capillaries. Externally it is in close contact
with the epidermis by means of its ganglionic layer, which is
about equal in thickness to the extremely delicate neuropile
forming its inner fibrous portion.

In A. Claparedii and in young specimens of A. marina
the intimate structure of the brain is very similar. The
anterior lobes are separated from each other ventrally by a
coelomic space. At a higher level they become almost con-
tinuous, but until the superficial ganglion cells are reached
there is a narrow slit continued between the lobes. At their
hinder end these lobes are connected by a band of transverse
fibres which form acommissure. It is not, however, possible
to delimit them exactly, for they are continued into a pair of
narrowed longitudinal tracts (continuous dorsally with the
anterior lobes by a common covering of ganglion cells).
These pass downwards to the margin of the ciliated groove,
and then come into contact with a pair of posterior lobes
specially related to these sensory organs (PI. 27, fig. 63).

The anterior lobes are composed of at least two kinds of
ganglion cells: (1) large unipolar elements ‘016 mm. in
diameter, the nuclei of which have one distinct nucleolus
and contain very little chromatin; (2) small cells (‘08 mm.)
with nuclei rich in chromatin, and with no distinct nucleolus.
The distinction, in fact, appears to be exactly the same as that
which holds good for the two chief kinds of ganglion cells of
the cesophageal connectives and of the ventral cord. Both
these kinds of cells occur in the intermediate region, but in
the posterior lobe the second kind are alone present, or at
least they preponderate.

The fibrous part of the brain is composed of an extremely
fine neuropile, and, in the anterior lobes, of tracts passing
from groups of ganglion cells into the connectives. There is
but little neuroghal tissue, and the neurilemma forms a
delicate membrane on the ventral and anterior surface of
the brain, and sends processes dorsally which divide in the
neuropile.

472 F. W. GAMBLE AND J. H. ASHWORTH.

The brain of A. cristata is composed of the same elements
as that of the two species just described. It is, however,
somewhat shorter, the anterior and posterior lobes are more
approximated, and the intermediate region correspondingly
reduced.

In A. ecaudata and A. Grubii the brain is wide from
side to side, and narrow from before backwards. The layer
of ganglion cells on its upper surface is produced into short
blunt processes, with intervening ccelomic and vascular
spaces. It contains the same two chief kinds of elements as
in A. marina, but the neuroglia is much more strongly
developed, and consists of multipolar cells lying in the fibrous
part of the brain, and sending processes in all directions.
The neuropile, especially in the brain of A. Grubii, is not
so fine as in, e.g., A. Claparedii.

The ganglionic layer of the brain in all species is in contact
with the epidermis of the prostomium. In the “ marina”
section this occurs along the entire dorsal surface; in the
“ecaudata” section it is affected by the ganglionic out-
growths, andis not so intimate. In this respect and in histo-
logical structure the brain of the latter section of the genus
Arenicola resembles that of Clymene (Maldanidz) as de-
scribed by Racovitza; that of the former is more closely similar,
however, to the brain of Mastobranchus (Capitellidss).

Cerebral Nerves.—The anterior brain lobes, in addition
to the cesophageal commissures, give off nerves to the anterior
end of the prostomium, to the upper lip, and the eversible
buccal mass. The latter are probably connected with the
cesophageal and gastric plexuses. In A. ecaudata and
A. Grubii, as was mentioned above (p. 470), the ciliated
grooves are generally supplied by several nerves arising
from the simple commissural brain.

The Growth of the Brain.—The changes which take
place in the arrangement of the nervous elements of the
brain during the life of Polycheetes, and especially those which
occur up to the attainment of the adult characters, have
hitherto scarcely been investigated at all. Nevertheless even

ANATOMY AND CLASSIFICATION OF THE ARENICOLIDM. 473

the rough method of sections shows that many obvious changes
are at work to which we are unable (in the case of Arenicola
marina at least) to fix an age limit. The brain of the oldest
specimens exhibits additional changes from those of slightly
younger and smaller examples, although in this respect the
species of Arenicola differ ; for the limit of growth, and with
it the definitive arrangement of the brain-elements, appear to
be reached sooner in A. ecaudata, A. Grubii, and A.
Claparedii than in A.cristata or A. marina. Indeed, in
the two latter, growth in the length and bulk of the body
seems to be coterminous with the life of the individual.

The changes occurring in the brain of A. marina (in
which we have examined a larger series of stages than in
the case of the remaining forms) are of two kinds: first, an
increase in the number of elements, involving a growth of the
brain in the later as well as in the earlier and post-larval
stages; and second, a differentiation of the form and arrange-
ment of the ganglionic centres and the fibrous tracts.

In a post-larva 4°5 mm. long the brain is ‘11 mm. long,
"065 to -7 wide, ‘02 to ‘03 deep; while in a specimen
75 mm. long the brain has almost exactly twice these
dimensions.}

Again, a lugworm 17:5 mm. in length, i.e. rather more
than twice as long as the latter and four times the length of
the first, has a brain of correspondingly greater dimensions.
Beyond this point the rate of increase of the brain is much
slower, but the limit is scarcely reached (‘9 mm. long) when
the animal attains a length of ten inches, for still larger
specimens, fourteen and fifteen inches long, have a slightly
larger brain, 1 mm. (see the table giving dimensions of the
brain and nerve-cord in specimens of different body-lengths).

' The measurements taken from preserved material are probably somewhat
less than the actual ones, on account of the contraction of the ccelomie spaces,
which to a certain extent distend the brain in the living animal.

474, F. W. GAMBLE AND J. H. ASHWORTH.

Taste showing the dimensions of the Brain and Ventral
Nerve-cord at different stages of growth of the species
of Arenicola. Measurements in millimetres.

Nerve-cord measured
Brain. 1 mm, behind union of
connectives.
Length of body. ale.
| Length. Breadth. Depth. Depth. Breadth.
A. marina
4°5 mm. 12 07 05 “025 06
cole 5 2 19 14 13 16
WAY 55 "A 3 16 | 13 12
25 oe *33 24 "24 13 16
60 o ‘D3 43 *36 All 22
150 Sy 5) 73 4 29 | 24
250 55 9 1°22 58 33 65
A. Claparedii |
20 mm. 4, "66 12 ‘08 16
A. cristata |
47°5 mm. *36 "52 "24 2 23
2850) mess 1-1 8 33 “27 ‘ol
A. Grubii |
38 mm. | °33 1:0 12 ilk 12
WS op | 2 1:0 yal 16 "145
| A.ecandata |
| 7°72 mm. ‘085 "26 “06 | i ‘065
QA ,, “09 28 “064 “08 “if!
| 150 a “52 2:0 27 “21 “21
| 180 53 5} 7/ 16 3 °29 "48

| ab | nal pele

This table shows that the linear dimensions of the brain in-
crease in the same proportion as does the length of the body
from the post-larva to a stage when the body measures about
17mm. Beyond this limit the brain increases more slowly,
and attains its maximum (‘9 to 1 mm. in length) in specimens
120 to 250 mm. long, according as they belong to the littoral
ov Laminarian varieties of the lugworm,

ANATOMY AND CLASSIFICATION OF THE ARENICOLIDA. 475

The second series of changes in the brain involve the for-
mation of ganglionic outgrowths on the dorsal surface of the
anterior lobes, the segregation of large cells (‘04 mm. in
greatest length) into centres, from which definite fibrous
tracts arise and pass into the cesophageal connectives, and
also into other parts of the brain. Separation of the smaller
kind of ganglion cells into discrete masses also takes place.
The neuroglia develops rapidly, and the fibrous part of the
brain assumes a much more complicated structure.

These are no doubt only the most gross of a long and im-
portant series of steps in the gradual differentiation of the
brain. In the post-larval stages, the ganglionic covering and
the delicate, almost homogeneous fibrous region show no
separation into centres and tracts, nor even a clear division
into differently constituted elements. In lugworms 60 mm.
long, at least two kinds of elements are distinct, but the cover-
ing of ganglion cellsis uniform and scarcely subdivided. ‘I'he
neuroglia is but slight in amount, the fibrous material still
neuropilar in aspect. Specimens of 150 mm. in length (mature
examples of the “ littoral’? variety) exhibit all the changes
we have just indicated above, but they are even better marked
in still larger individuals (250 mm.).

Both series of changes occur in the other species of
Arenicola. In A.ecaudataand A. Grubii the subdivision
of the primitively uniform ganglionic covering occurs some-
what earlier than in A. marina, and there are indications of
segregations of large pyriform and of smaller cells to form the
centres of tracts to different parts of the brain, and from the
brain to the connectives. In a specimen (26 mm. long) of A.
Claparedii (which, however, is quite a young one and not
by any means mature) the brain resembles in form and
structure that of an individual of A. marina 50 to 60 mm.
long. In spite of the more strongly developed prostomium in
A. Claparedii the brain does not appear so complex as in
the common lugworm, and this is probably due to the fact
that the brain is in intimate contact with the prostomial epi-
thelium through its dorsal ganglion cells, and not by special

476 F. W. GAMBLE AND J. H. ASHWORTH.

nerve tracts, while the comparatively small size attained by
A. Claparedii may account for the lack of demarcation of
regions which is such a noteworthy character in the brain of
large specimens of A. marina.

These considerations raise the question of the real nature
of the so-called brain in these forms. No doubt it is essen-
tially a centre for afferent impulses received from the sensory
prostomium and prostomial sense-organs, as well as from the
nerves of the buccal papille, of the lining of the buccal mass
and possibly from the gastric plexus further back still. But
in addition to this, at least one pair (and probably more) of
efferent centres! are found in it, and it is probable that from
these efferent impulses travel down the connectives by certain
tracts to the nerve-cord. Compared with the arthropod
brain, however, the development of these tracts binding
the different parts of the brain together, and connecting the
brain through the cord with peripheral endings, must be con-
sidered in Arenicola and Polychetes generally as but slight.
Still there are indications of them, and future investigation
will have to discover how far the impulses derived from the
prostomium and buccal sense-endings are followed by effer-
ent impulses affecting the muscular glandular tissues ; what
is the course taken by the reflex action, and also what
reflexes are possible in the absence, or apart from the control,
of the brain. The few physiological observations which
have hitherto been made on Polychetes .scarcely afford
ground for conclusions on this subject. In Crustacea, how-
ever, some recent and very suggestive results have been ob-
tained by Bethe, which have a distinct bearing on the problem
of the significance of neuropile in initiating efferent impulses.
Since it is in the brain of Arenicola, and also, according to
Hamaker (1898), in that of Nereis, that neuropile is chiefly
present, Bethe’s experiments may throw some light on the
function of the Polycheete brain.

Bethe’s experiments (18984) were carried out on crabs.

1 The paired masses of large pyriform ganglion cells placed near the middle
line of the anterior cerebral lobe (p. 475),

ANATOMY. AND CLASSIFICATION OF THE ARENICOLIDA. 477

After completely removing every ganglion-cell from which
the motor fibres of the second antenna arise (as shown by the
methylene blue method), Bethe still obtained movement of the
antenna on stimulation for two days after the operation, but
the response became weaker and weaker, and after this
interval no reflex action could be induced. This, he suggests,
is due to the loss of the normal trophic action of the ganglion
cells which were removed; while the efferent impulse is due,
not, as is generally thought, to the motor ganglion-cells, but
to the neuropile which connects the end of the afferent fibre
with the commencement of the efferent one. The ganglion
cells are, then, nutritive, and the reflex action can go on for
some time when they have been removed go long as this
operation is effected without injuring the neuropile to which
they are connected. Slight injury to the neuropile, however,
causes a most serious loss of the power of response to stimu-
lation. According to this important experiment, of which we
have given the merest outline, the series of changes by which
an afferent impulse sets up an efferent one, aud so determines
the character of, e. g., a muscular contraction, takes place in
the neuropile which connects the recipient fibre from the
surface and the motor fibre to the muscle; while the ganglion
cells which are intercalated in the path from one fibre to the
other exert an important nutritive influence on the reflex
mechanism, but cannot be stated to be essential to the reflex
act.

This experiment certainly suggests that the greater develop-
ment of neuropile in the brain than in the cord of Arenicola
(and other Polycheetes) may confer upon the brain the power
not only of receiving afferent impulses from the prostomial
and buccal sense-organs, but also of converting these into
efferent ones, which may issue as movements of the somatic
or splanchnic musculature as an increased glandular secretion,
and in other ways. ‘To determine how far this is the case,
and along what tracts these efferent impulses are carried out,
will be the work of future investigation.

478 F. W. GAMBLE AND J. H. ASHWORTH,

II. Hsophageal Connectives.

Inthe “marina” section of Arenicola the connectives are
slender. They spring from the ventro-lateral angles of the
anterior lobes of the brain, which at this level are widely
separated by a ccelomic space. In the ecaudata section,
however, the brain is so short and broad that it passes almost
insensibly at its outer ends into the connectives.

The further course of the connectives is marked externally
by the “metastomial” grooves. In A. marina these grooves
are sometimes quite distinct, especially in living specimens,
in others they are faint and sometimes invisible. In A.
Claparedii they attain their maximum development (PI. 27,
fig. 62), and may be traced as oblique grooves on the body,
commencing on each side at the nuchal organ, where they are
deepest. They unite in the mid-ventral line on the third
annulus. In A. cristata they are absent, while they are
rather faintly indicated in A. ecaudata and Grubii.

The connectives lie just to the inner side of the epidermis
lining these grooves, and they unite in front of the first
chetigerous annulus. The exact position of their point of
union—the beginning of the ventral cord—occurs just an-
terior to the annulus in front of the first parapodium.

In the post-larval stages of A. marina the union of the
connectives occurs in an annulus, dorsally possessing the
vestigial cheeta seen by Benham, and belonging to the first
segment following the peristomium. Counting the peri-
stomium as a segment, this would place the origin of the cord
in the second segment, one annulus in front of the first
chetigerous segment of the adult; and the same applies to A.
Claparedii. In A. cristata the union of the connectives
occurs even further forwards. At first they are slender, and
arise from the anterior end of the brain, which is here not
distinctly lobed, though distinctly subdivided into right and
left portions. From this point they run almost vertically
downwards and slightly outwards, but do not lie close to the
epidermis.

ANATOMY AND CLASSIFICATION OF THE ARENICOLIDE. 479

In the “ecaudata” section the commissures are much
stouter. They run downwards on each side of the mouth
and then backwards, uniting at a distance of two annuli from
the first parapodium, so that in all species of Arenicola the
origin of the ventral nerve-cord lies in the second segment
of the body.

Branches.—The connectives give rise to nerves (1) to the
skin at the level of the interannular grooves through which they
pass; (2) to the otocyst; (3) to the ventral half of the buccal
mass. ‘The last nerve constitutes part of the stomogastric
system, or, more correctly, it is probably united at the end of
the eversible buccal region to the stomogastric system. The
nerve to the otocyst deserves a separate description. It is
‘2 mm. long, and is given off just opposite its otocyst, to which
it runs upwards and inwards. Its chief peculiarity lies in the
rich collection of ganglion cells, both at the point of origin of
the nerve and along the greater part of its course. They are
of two kinds. One, large, pyriform, measures ‘008 mm. in
breadth and ‘016 in length. Their nuclei are ‘007 mm. in
diameter, and have a vesicular nucleus and a distinct nucle-
olus. The other kind of cell is smaller, of undetermined
shape, and a nucleus ‘004 mm. diameter. The former occur
chiefly on the outer side of the nerve, and do not reach the
otocyst itself. The latter are more abundant, and are packed
away between the larger cells and occur on the nerve right
up to the base of the otocyst.

This ganglionation of the otocyst nerve is, however, only
an expansion of a local thickening of the connectives which
underle the nerve to the body-wall, and this, again, is an en-
largement of the continuous ganglionic covering which in-
vests the inner side of the connective along its entire length ;
but the great development of their ganglion cellsin the nerve
to the otocyst is peculiar, and not met with in any other
peripheral nerves,—at least, not to the same degree.

480 F. W. GAMBLE AND J. H. ASHWORTH.

III. Ventral Nerve-cord.

The position of the cord in the body varies in different
species and in different parts of the body of the same species.
In Arenicola Grubii and A. ecaudata the cord is ce-
lomic throughout. In A. Claparedii itis epithelial, or only
covered externally by circular muscles, while its ganglion
cells lie practically in the epidermis. In A. marina and A.
cristata the cord is epithelial in the tail, but 1s coelomic in
position in the branchial and anterior regions. This varia-
tion is exactly parallel to the varying position of the cord
in Capitellids, with which the Arenicolide also agree in the
structure of their cord.

There are no signs of a segmentation or ganglionated
arrangement of the elements, except the presence of the
“ giant-cells”’ at intervals corresponding to the segments.
Around these giant-cells there are rather more ganglion cells
of the larger type than elsewhere, but this cannot be said
to constitute a ganglionic segmentation. Ganglion cells, in
fact, occur along the whole length of the ventral and lateral
surfaces of the cord, and this continuous covering is only
interrupted by the exit of the spinal nerves.

When the cord has a ccelomic position (as in A. Grubii),
it is attached by its lower angles and under surface to the
longitudinal muscles which are inserted partly into the
neurilemma covering, and partly beneath this into the sheath
of the more ventrally placed ganglion cells. The vascular
supply is poor, and except for a superficial collection of
capillaries there are few traces of blood-vessels in the truly
nervous structures of the cord.

In transverse sections the cord exhibits the usual arrange-
ment of a ventral cellular and a dorsal fibrous portion. There
is a marked development of neuroglia, as a sheet of tissue in
a vertical plane separating the right portion of the cord from
the left. This sheet of neuroglia is continuous with a net-
work of the same tissue which invests the ganglionic layer.

The neurilemma forms astout, deeply staining, laminate.

ANATOMY AND CLASSIFICATION OF THE ARENICOLIDA. 481

sheath for the whole cord. Here and there it penetrates
deeply into the fibrous region, which it subdivides into
areas. In A. Claparedii it is very feebly developed, and
practically replaced by muscle-fibres of the circular series.

The neuroglia is composed of delicate nucleated cells,
and of fibrille which invest the nervous elements. The
structure of this tissue is more fully dealt with in connec-
tion with the giant-cells (p. 486). In horizontal sections it
forms a number of deeply-staining fibrillee which run longi-
tudinally between the two lateral masses of ganglion cells,
and fills up the spaces between these and the giant-cells.
The resemblance between these longitudinal glia-fibrille
and the neuro-fibrillar processes of the true ganglion cells is
at first sight, in many preparations, a very close one, but
the relation of the fibrille to the cells (in the case of neuro-
glia forming sheaths, while the neurofibrille enter the sub-
stance of the ganglion cells through their process). enables
one to distinguish them.

Ganglionic Covering.—The majority of ganglion cells
in the nerve-cord of Arenicola Grubii are unipolar, and
are collected into two lateral masses, which at the point of
emergence of a spinal nerve become subdivided into four—
two median and two lateral. The largest of the ordinary
ganglion cells are placed near the “ giant-cells,” and in
most cases their fibrillar processes divide, one part going
outwards as a constituent of a nerve and the other breaking
up in the fibrous part of the cord. It is difficult to ascertain
the detailed structure of these ganglion cells, since even the
larger ones only attain a diameter of (02 mm. ; but a distinc-
tion may certainly be drawn between these larger cells and
the more laterally placed smaller cells ((008—-01 mm.), on
account of the constant difference of their nuclei. ‘The
nuclei of the larger pyriform cells measure ‘(012 mm. in
diameter, and are clear vesicles with one large (and some-
times one small) nucleolus, but with a very slight development
of chromatin network. The cell-body is composed of a more
deeply staining central region and a peripheral alveolar zone.

482 F. W. GAMBLE AND J. H. ASHWORTH.

The nucleus is placed near the broader end of the cell, while
from the narrow end the single process arises, and within
this a few stout neuro-fibrille can often be seen pursuing a
characteristically sinuous course into the fibrous part of the
cord. The smaller ganglion cells are placed more laterally.
Their shape is very difficult to determine, and we are not
sure whether they possess more than one process. The
nucleus measures ‘004 mm., and has a well-marked chromatin
network with a very small nucleolus.

Fibrous Part of the Nerve cord.—Except in the
dorsal region under the giant-fibres, the two fibrous tracts
of the cord are separated by a vertical sheet of neuroglial
tissue embedded in a transparent matrix. In transverse
section they do not present the same appearance in all
regions nor in all parts of a segment. Posteriorly they are
much more extensively invaded by branched processes of the
neurilemma, which is only slightly developed in the branchial
region; and at the origin of the spinal nerves the processes
of the two central masses of ganglion cells give the section
at this point a more strongly fibrous aspect than in the
intermediate zones.

The methods we have chiefly employed are not adapted
for a successful study of the difficult subject of neuropile.
Yet we may say that the characteristic appearance of this
tissue is almost absent from the nerve-cord, while it is well
shown in the brain. The nerve-fibres themselves, though
surrounded by an intricate neuroglia investment, do not stain,
or at most show faint indications of fibrillee.

Spinal Nerves.J—A pair of nerves arise from the cord
opposite each interannular groove, along which they run
upwards and supply the body-wall. Opposite each cheti-
gerous annulus, however, there are from two to four pairs of
nerves. Hach nerve consists of a stout band of fibres which
pierces the ganglionic layer at the outer angles of the cord,
and then runs outwards between the circular and longitudinal
layers of muscle, each of which it supplies. In several cases

1 See Pl. 29, fig. 78.

ANATOMY AND CLASSIFICATION OF THE ARENICOLIDM. 483

we have been able to trace a process of the lateral “ giant-
fibres” into the spinal nerves (p. 491), but this does not occur,
so far as we ascertained, in the case of every pair of nerves.
This processis generally distinguishable from the other fibres
by its sheath and delicately fibrillar contents.

In addition to the motor and sensory fibres, the nerves also
contain stellate cells, generally somewhat shrunken, so that a
space separates the body of the cellfrom the surrounding fibrous
tissue. The nucleus contains a chromatin network, and the
protoplasm is differentiated into fine sinuous fibrille staining
deeply with iron hematoxylin. These cells are doubtless
of neuroglial nature. We have also noticed a few scattered
cells which are apparently ganglionic. They occur chiefly
at the commencement of the nerve just after it leaves the
cord, but owing to the failure of the elements to respond
to methylene blue we are unable to trace the processes of
these cells, or to distinguish satisfactorily the motor from
the sensory fibres of the nerves.

IV. Giant-cells and Giant-fibres.
A. Giant-fibres.

Giant-fibres occur in all species of Arenicola except A.
Claparedii, but we have studied them with most care in A.
Grubii. In a piece of the fresh cord of this species they
appear as tubes (‘1—'3 mm. diam.) with a distinctive wall and
homogeneous contents. Anteriorly there is a single median
fibre ; in segments five to ten there are two; in the central
region of the body there are generally three ; and posteriorly
only one. From the inner surface of the wall of the fibre,
shreds or granular tags project into the interior, but owing
to the opacity of the enveloping neurilemma and the granu-
lar cells of the peritoneum, it is impossible to make an ex-
haustive examination of the giant-fibres by the simple
inspection of the fresh cord. Some evidence of the nature
of these fibres is afforded by their behaviour towards re-
agents. Ifa 2 per cent. solution of osmic acid be added to
unaltered pieces of fibre they become brownish, but not black,

VOL. 43, PART 3,—NEW SERIES, LL

484, Fr. W. GAMBLE AND J. H. ASHWORTH.

and the effect is limited to the sheath, while the contents
remain translucent and colourless. In sections of the nerve-
cord taken from pieces fixed with vom Rath’s (osmic-acetic-
platinic chloride) mixture and subsequently treated with
pyrogallol or crude pyroligneous acid, the sheath is staimed
brown. The nature of this sheath is demonstrated by sections
prepared by the various methods described on p. 468. There
is first, the neurilemma sheath which envelops the entire
nerve-cord ; but within this, directly enclosing the giant-fibre
and sending tag-like processes into its contents, is another
sheath, which is slightly laminated or fibrillated, and composed
of nucleated cells of what we consider neuroglial nature
(Pl. 27, fig. 66). This is the true sheath of the giant-fibre,
and from its reactions, evidently contains a certain amount
of myelin,’ though not so much as in the earthworm or in some
members of the family Maldanide.

The contents of the fibres appear in transverse section to
be extremely finely granular, staining faintly with iron hema-
toxylin. In longitudinal sections, and also at points where
the lateral fibres anastomose with each other, or with the
central one, they present a distinctly fibrillar structure, but
so fine are the fibrille that they are irrecognisable when cut
transversely. The fibrillaee are embedded in an almost homo-
geneous protoplasm, which in many places shrinks away some-
what from the neuroghal sheath. ‘This is due to the myelin
sheath being dissolved by most of the reagents employed with
the exception of osmic acid. In the fresh condition and in
many series, however, the contents of the giant-fibre almost
fill the sheath.

The giant-fibres arise from giant-cells of the cord. Many
of our preparations give direct evidence of this mode of origin
(Pl. 28, figs. 70—73), and although on account of the sinuous

1 The fullest proof that myelin does occur in the sheath of Chetopods is
given by Friedlander (1894). The presence of this substance is a very impor-
tant fact, for it furnishes an exact parallel to the medullary sheath of Verte-
brates. Not only so, it will now be possible to trace the course of i giant-
fibres by the degeneration method.

ANATOMY AND CLASSIFICATION OF THE ARENICOLIDA. 485

course of the cell process which enters the giant-fibre it is
not always possible to trace the connection in one section, yet
it can be seen on following the process through one or two
adjacent sections. We have verified this point again and
again in the case of the majority of the giant-cells in one
specimen of Arenicola Gru bii, by the examination of a con-
tinuous series of sections through the entire length of the
worm. Additional evidence on the point is given by prepara-
tions of the nerve-cord of the common lugworm (A. marina) ;
and as all species of the genus except A. Claparedii possess
giant-cells (arranged just as regularly as, but not always at-
taining the size of those of A. Grubii) we may fairly pre-
sume that this mode of origin occurs throughout the entire
genus.

It is necessary, however, to go into the details of these cells,
their processes, and the connections of the median and lateral
fibres with each other and with the cord.

B. Giant-cells.

The giant-cells of the nerve-cord of Arenicola Grubii
are conspicuous by reason of their large size and singularly
regular arrangement. Throughout the greater part of the
length of the cord, as is shown on PI. 29, there are, as a
rule, two of these cells placed in line an annulus apart, close
to the hinder limit of each segment. The limits of the
segments are marked externally by the groove separating the
first from the second annulus behind the chetigerous one.
The giant-cells are therefore placed in a fully extended animal
just in front of this groove, and where there is only a single
giant-cell, as is the case in the anterior one or two of the
branchial segments of the body, this single one usually corre-
sponds in position to the more posterior of the two present in
the majority of the segments. In the singular regularity
displayed by the arrangement of these cells Arenicola
Grubii appears to be paralleled by Polynoé (Rohde, 1887).

We have been at considerable pains to ascertain and plan
out these cells from an entire series of sections of a complete

486 F. W. GAMBLE AND J. H. ASHWORTH.

specimen 78 mm. long, and the result is given in Pl. 29, fig. 79.
There are no giant-cells in the brain. The first one occurs at
the point of union of the cesophageal connectives well in front
of the first cheetigerous segment, and it therefore probably
belongs to the (in the adult) achetous segment immediately
following the peristomium. In the second and third che-
tigerous segments there is only a single giant-cell, while in
the fourth segment the posterior of the two cells is represented
by two rather small ones close together side by side. Behind
this point the arrangement is uniform, being subject merely
to slight irregularities in position. In one segment (thirty-
fifth), however, the cells are absent. In the last segment two
small cells are present.

In sections of the cord, the giant-cells occupy an almost
median and ventral position among the ganglion-cells which
cover the lower surface. On the average each giant-cell
occupies a third of the width of the cord in transverse or
horizontal sections, and at the level of the nucleus measures
50 to 80 u in diameter. The real shape of the giant-cells is a
pyriform one, and the narrow extremity is placed laterally and
prolonged upwards into the fibrous matter of the cord. On
the evidence of the methods we have successfully employed,
this process appears to be the only one given off from the
giant-cell in every case.

The structure of the body of the cell merits detailed descrip-
tion. First there is a nucleated fibrillar sheath of neuroglial
nature. In horizontal sections the nuclei are flattened parallel
to the surface of the cell; when transversely cut, however,
they appear more circular. Externally the limits of this
fibrillar sheath are not well defined. They merge imper-
ceptibly into the glia network which fills the interstices
between the surrounding cells. The fibrils of this sheath
give all the appearance in response to hematoxylin and
hematein stain that are attributed to them by Apathy (1898)
in the sheath of ganglion cells of the leech and earth-
worm. Of these appearances the most important are their
extensions between the surrounding ganglion cells already

ANATOMY AND CLASSIFICATION OF THE ARENICOLIDM. 487

adverted to, and the fibrils radiating into the outer layers of
the protoplasm of the giant-cell (Pl. 28, fig. 76, Ngl. fllx.). In
one or two giant-cells the glia-fibrillaee penetrate more deeply
into the protoplasm, and form a definite network, staining
deeply and sharply with iron hematoxylin or Apathy’s
heematein 1 a.

The protoplasm itself presents certain peculiar appearances.
The outermost layer is distinctly alveolar,! and is demarcated
on its inner surface by a distinct membrane, or what seems to
be such, and which in sections is seen to be traversed by pro-
cesses from the glia fibrille of the sheath. The outer alve-
olar layer is clear, non-granular, and does not stain. At each
end of the cell is a distinct vacuole, which has also been
noticed in the giant-cells of other annelids. The rest of the
cell protoplasm can be differentiated into (1) the main body
of the cell; and (2) one, or in some cells two regions, which
have characters similar to those described for the centro-
spheres of the giant-cells of Maldanids by Miss Lewis (1898),
and also resembling to a certain extent the description of
centrospheres in the ganglion cells of leeches and of Lumbri-
cus as given by Apathy (1897). The main mass of the cell-
protoplasm stains lightly. It contains a multitude of minute
granules, and these are often arranged as a network round
or in, a clear non-staining substance, thus giving a character-
istic “ Wabenstructur.” Different giant-cells vary much in
this respect, however ; some, asin PI. 28, figs. 70, 76, showing
it very clearly, while others show a uniformly granular sub-
stance without alveoli. Should the alveolar structure occur,
it is usually very plainly marked round the nuclear membrane,
and may extend up to the membrane noted already. With
reference to the so-called centrospheres we may mention the
radiating arrangement of chromophilous granules round a
central point, usually between the excentrically placed nucleus

1 The whole question of the existence of alveoli and fibrils in living cells
has lately been reopened. See the very suggestive paper by W. B. Hardy
in the ‘Journal of Physiology,’ vol. xxvii, 1899, “On the Structure of Cel!
Protoplasm.”

488 F, W. GAMBLE AND J. H. ASHWORTH.

and the broad end of the giant-cell. Here they form a distinct
deeply staining area which may be observed in almost every
giant-cell. In a few cases a transparent body (‘004 mm. in
diameter) appears to form the focus towards which the lines
of granules converge. The granules are here rather larger
and stain more deeply than those of the rest of the cell-body.
The whole appearance is accurately recorded by Miss Lewis
in Maldanids, with whose descriptions our own preparations
from Arenicola Grubii closely agree, except that we have
not satisfied ourselves that a ‘‘ centrosome” is actually
present (Pl, 28, fig. 77, Centr.).

The nucleus is a large subspherical structure, averaging in
the larger giant-cells 20 » in diameter. Within the distinct
nuclear membrane are the chromatin network, the fluid
contents, and usually one lens-shaped nucleolus about 6 w in
diameter. The nucleus is always excentric, and is usually
placed near the broader end of the cell.

We have reserved to the conclusion of this description
the most debatable element of structure, namely, delicate
fibrillee distinct from the glia-fibrille of the sheath or from
any other usual cell-element, and which we conclude repre-
sent Apdthy’s neuro-fibrilla. They are by no means to be
seen in every preparation, even of those produced by the
same method, but in successful cases they stand out very
clearly, especially in the cell process (see Pl. 28, figs. 70 and 76,
nlle.), whose structures we have so far entirely neglected.

The cell-process is enveloped by a fibrillar nucleated glia-
sheath, which is continuous with that of the cell-body.
The protoplasm within this sheath is clear, and, though finely
granular, does not stain, or at most very lightly indeed. It
is penetrated by delicate, darkly-staining fibrille, which do
not branch in the process, but on entering the body of the
cell break up into at first a few branches (Pl. 28, figs. 70, 71,
76, Nilz.) and these into still finer ones as they approach the
basal part of the cell. Frequently they are only stained as
they enter the cell, and then they appear to end abruptly, but
in successful cases (and especially in horizontal sections

ANATOMY AND CLASSIFICATION OF THE ARENICOLIDA. 489

stained with hematein | 4 or iron hematoxylin) they can be
followed from the base of the cell-process round the body of
the cell, and can be seen to divide and penetrate into the
layer which hes inside the outer alveolar zone. They do not,
however, seem to reach the nucleus, but are limited to the
more superficial layer of the granular and, it may be, slightly
alveolar protoplasm. In some cases the processes of these
neuro-fibrillz appear to terminate in the central granular
network of the protoplasm, but this is probably mere contact.

In order, however, that these “ neuro-fibrille ’’ should
thoroughly conform to the structures which Apathy has so
named, it ought, according to this author, to be shown that,
after branching at the broad end of the cell, they again unite
and run a recurrent course along the cell process, and so
through the fibrous part of the cord to muscle or gland.
This we are not able to show. But we believe that we are
able to distinguish these “ neuro-fibrille’’ by their course,
and especially by their relation to the cell process from the
histologically similar glia-fibrille, which, as we have seen,
either penetrate but a short distance from the sheath into the
outer alveolar layer, or more rarely form a more complete
network within the cell substance.

To further determine the character of these giant-cells it
is necessary to examine the nature and course of the cell
process. We are only able to demonstrate one stout process
to each giant-cell, forming, so to speak, the stalk of the cell.
The fine granular contents of this stalk do not stain; they
contain “ neuro-fibrille,” and they are ensheathed in a fibrous
envelope of a deeply staining character. The process so
formed runs a somewhat sinuous course through the fibrous
part of one side of the cord towards the upper surface.
Shortly after leaving the cell it gives off a branch to the
outer side of the cord, and further on another. These
branches end apparently in the fibrous region of the cord,
and are not invariably present. When the cell-process has
arrived near the median dorsal line of the cord its further
course varies according to the region of the body with which

4.90 F. W. GAMBLE AND J. H. ASHWORTH.

we are dealing. In the first few segments and in the last
two the process enters into the median giant-fibre. The first
cell, placed at the point of union of the cesophageal commis-
sures, may be said to be the starting-point of this fibre; and
though, as we shall see, the median fibre gives off branches
and fuses from time to time with the lateral ones, yet it may
be said to be continuous from one end of the body to the
other (see Pl. 28, figs. 67—73).

The greater number of the giant-cells, from the fifth
segment to the last but two or three, of Arenicola Grubii
enter into direct connection, not with the median giant-fibre,
but with the lateral ones. In several cases we have noticed
that their cell-processes at first behave as do those which
join the median fibre; that is to say, they curve upwards
towards the dorsal surface, giving off one or two small
branches to the cord on their way. ‘Then they enter one of
the lateral giant-fibres, usually at a point where it is connected
with its fellow by a junction which runs beneath the median
fibre (Pl. 28, figs. 67—70). The exact behaviour of the cell
process at this point varies in different cases, and requires
additional methods to those we have employed for its com-
plete investigation. It appears almost certain, however, that
the cell-process divides in a T-like fashion. The stalk of the
T represents the process, and the cross-piece the lateral
neurochord, which, starting from the cell process, runs for-
wards and backwards, and at once, or after a very short
course, unites with or sends a branch to, the giant-fibre of the
opposite side. A single branch or a pair of lateral branches
are also given off from the cell process to the fibrous part
of the cord just at its point of division into the neurochord.
In other cases the cell-process divides; one small branch
entering a lateral fibre, and the rest gradually lose them-
selves in the cord without any definite termination.

In attempting to trace the lateral giant-fibres from their
points of contact with the giant-cell processes, we have found
that in front of these points up to the chetigerous annulus,
the two fibres anastomose in a perplexing way, and give off

ANATOMY AND GLASSIFICATION OF THE ARENICOLID™. 491

two pairs of branches, which run down the sides of the cord
to the roots of spinal nerves. At the level of the chetigerous
annulus the three fibres exhibit a thickening of their fibrous
sheaths; they fuse laterally, and a pair of branches spring
from the fused mass and run to the spinal nerves of this
annulus (Pl. 28, fig. 74).

Behind the point of contact of the lateral giant-fibres and
the processes of the giant-cells the arrangement is simpler.
Here, as a rule, one of the lateral fibres, after a little
preliminary branching and crossing, disappears in the cord,
and the other alone continues through several annuli by the
side of the median fibre until the next chetigerous region is
reached, and then the complicated arrangement of the great
fibres begins again.

This is obviously a case where a topographical method is
required to determine with accuracy the connections and
terminations of these fibres, but, as we have explained in a
preceding section (p. 468), neither methylene blue nor Golgi’s
method, applied in the usual manner and varied in several
ways, was effective. We have, however, shown that there is
an intimate connection between the giant-fibres and the
giant-cells, between the giant-fibres and the spinal nerves,
and between the process of the giant-cell and the fibrous
matter of the cord.1 ,

c. The Nature of Giant-cells and Giant-fibres.

The histological features of these giant-cells are identical
with those of unipolar ganglion cells. Indeed, the only other
class to which the giant-cells could be referred would be the
large neuroglia cells of the kind described by Apathy (1897)
in certain leeches as “ grosse mediane Sternzellen” and
“ Leydig’s Zellen.” These glia-cells, however, are not only
multipolar, but they exhibit throughout their cell-body a

1 We are fully aware of the opinion shared both by Retzius and Lenhossek
that the giant-fibres are not nervous, and do not originate in the way we
describe. The discussion of the evidence for and against the view we adopt
is given more fully on p. 492.

492 F. W. GAMBLE AND J. H. ASHWORTH.

characteristic fibrillar network which arises from the outer
fibrous sheath. The chief difference, moreover, between
them and true ganglion-cells lies, according to Apathy, in
the number and arrangement of the neuro-fibrille : these
specially large glia-cells only possessing a few fibrille
which do not exhibit the formation of a network by the
ingoing fibrils, and recombination to form outgoing ones.
In other respects—in their position in the mid-ventral line of
the cord, in their size (70 to 80 » diam.)—they superficially
resemble the multipolar ganglion cells, with which indeed
they have previously been confused by the earlier writers on
the Hirudinean nervous system.

We have compared Apdathy’s description (unfortunately he
has hitherto published no figures) of these ‘‘ Sternzellen ”’
with the appearances exhibited by the giant-cells of Arent-
cola, and we find that the giant-cells differ in being unipolar,
in the nature of their single process, and in the number and
arrangements of the neuro-fibrillee, while they conform in all
these points with ganglion-cells.

Accordingly we feel justified in considering each giant-
cell, its process and branches, as a distinct nerve element of
the cord.

The doubt which has been hitherto felt by many anatomists,
and which is still widely shared, as to whether the giant-fibre
is a process of the giant-cell, and whether it is nervous in
function, arises partly through the negative reply given by
Retzius (1891) and von Lenhossek (1892), and partly by the
lack of analogy of the giant-fibres with any recognised nerve
element either in their structure or in their relation, or rather
want of relation, to the rest of the nerve-cord. It is urged
that every important nervous structure in the cord of Lum-
bricus can be demonstrated by the Golgi method, but that
the giant-cells and fibres cannot be impregnated ; and it is
held that this failure of the method in the hands of such
competent histologists as Retzius and Lenhossek is sufficient
to show that these cells and fibres are other than ordinary
nerve elements, if indeed they be nervous. On the other

ANATOMY AND CLASSIFICATION OF THE ARENICOLIDA. 493

hand, while many equally competent observers by the use of
other methods have shown that even in the earthworm the
giant-fibres do arise from an anterior and a posterior group of
cells, and that in many Polychetes they arise from a couple
or more, of symmetrically or irregularly arranged giant-cells,
yet these observers do not adequately prove a fusion of
elements—which on the face of it would be a serious
blow to the neuron theory,—and they do not show that
the giant-fibres have either fibrillar connections or a mode
of termination comparable with that of fibres which arise
from cells within the cord. ‘he evidence of their nervous
nature is not felt to be so convincing, nor demonstrated by
such experiments—for example, on their degeneration and
subsequent repair, accompanied by loss and renewal of the
power of co-ordination,—as to obtain the general acceptance
of anatomists.

The experimental evidence is undoubtedly very weak.
Friedlander (1895), as is well known, has studied the re-
generation of the giant-fibres which follows section of the
cord in the earthworm. He found that the fibres degenerated
like normal nerve-fibres, but that subsequently from each
cell a number of new fibres arose in the new part of the cord,
but this is almost the only work in this direction.

The Wallerian or degeneration method has not hitherto
been employed, but it will no doubt throw much light both
on the course and termination of the fibres, and also on their
behaviour under this method as compared with ordinary
nerve-fibres. We are, therefore, thrown back upon the
anatomical results obtained by the use of various histological
tests. By this means it has been shown, for example, that in
Lophius, by G. Fritsch (1886), in certain Crustacea (Retzius
[1890], Allen [1894], Bethe), and in many Annelids
(Spengel [1882], Hisig [1887], Rohde [1887], Lewis [1898],
etc.), the giant-fibres arise from giant-cells. In Lophius
the origin and course of the fibres was determined in 1886,
and their structure has since been examined in detail by
Apathy, but their termination is still unknown. The fibres

494, F. W. GAMBLE AND J. H. ASHWORTH.

have a stout sheath, and consist of bundles of delicate
fibrille. They arise from large median cells of the cord,
according to Fritsch multipolar, according to Apathy unipolar,
and they accompany the dorsal roots of the spinal nerves.

The most recent explanation of the structure and function
of giant-fibres is given by Apathy, who has studied them in
most detail in leeches and Lumbricus, but alsoin Lophius.
According to this author, in at least each of the anterior nerves
of leeches, there are three large ‘sensorische Schlauche ”
in addition to the usual motor and sensory fibres. These
“sensorische Schliuche” may be traced into the fibrous
matter of the cord, where they become much smaller. Hach
divides in a T-like manner, and gives off branches which
end in peculiar thickenings, ‘ Endkolben,” from which
extremely fine fibrils are given off. In Pontobdella, how-
ever, there is in each connective between adjacent gangha
a large dorsal and generally median “ Schlauch,” which ter-
minates by divisions as in other leeches. Apathy does not
state whether these sensory structures, which he homologises
with the giant-fibres of, e. g., Lumbricus, arise from peri-
pheral sense-cells, but that practically follows from their
course and termination in the cord. Their structure is
characteristic ; according to Apathy they consist of neuro-
fibrilla embedded in peri- and inter-fibrillar structures, the
whole being enclosed in an inner myelin sheath and an outer
neuroglial sheath. By their structure and their mode of
termination in the cord, the “ sensorische Schlauche ” are dis-
tinguished, according to this author, from the other sensory
elements which form bundles, ‘‘ sensorische Biindeln.” Both
these sets of sensory fibres are distinguished from the motor
ones by the absence of any direct connection with ganglion
cells in the cord, such as those in which the motor fibres as
usual arise ; but inno case does Apathy give any indication of
the starting-points for the formation of these sensory tracts.

In Lumbricus the same distinctions hold good, and it is
pointed out that the “ giant-fibres” are in fact the central
portions of the “ sensorische Schlauche.”’

ANATOMY AND CLASSIFICATION OF THE ARENICOLIDA. 495

Thus in the earthworm Apathy states (1897, p. 624), “Die
Neurochorde enthalten nimlich ausser sehr dunnen Primitiv-
fibrillen eine Anzahl starker, meist trotz ziemlicher Streckung
des Thieres, sehr kleinwellig, aber im ganzen in gerader
Richtung verlaufender Primitivfibrillen in axialer Lage,
und diese starker Primitivfibrillen sieht man in frontalen
Schnitten besonders deutlich (also auch in transversalen
oft sehr schén) an verschiedenen Punkten aus dem Neuro-
chord durch diesen dicke Gliascheide heraustreten, und in
der Fasermasse in transversalen Richtung eine Strecke weiter
gehen.” But no reference is made to the fact ascertained by
Friedlander and Cerfontaine that these giant-fibres, neuro-
chords, or “‘sensorische Schlauche,” by whatever names they
are called, have been traced to what the two latter authors
believe to represent ganglion-cells, and with which these
fibres are certainly connected.

Lastly, in Lophius, in which, as is well known, giant
cells and fibres have been discovered by Fritsch (1886),
Apathy describes giant-fibres in the dorsal spinal nerve-
roots, and states that he traced them from the large pyriform
_ganglion-cells discovered by Fritsch, and out of the dorsal
furrow of the cord into the dorsal root (which contains
sensory and motor fibres). He adds, however, that he is
about to re-examine this result. Though their origin may
be doubtful, Apathy states on the ground of their structure,
that the giant-fibres of Lophius are also ‘ sensorische
Schlauche,” and equivalent to the structures so named in the
nerves of Hirudo. A noteworthy distinction to which he
does not draw attention, is the central course of these fibres
in Lophius. For no one has, as yet at least, described a
T-shaped bifurcation followed by subsequently branching,
and termination by minute fibrils in the neuropile of the cord.

Apathy’s conclusions, in fact, may be summarised thus.
Giant-fibres are a normal constituent of the ordinary mixed
nerves of leeches, Oligochetes, of the dorsal (also mixed)
nerves of Lophius, and of the nerves of Astacus and
Palewmon. These giant-fibres are better called sensory

4.96 F. W. GAMBLE AND J. H. ASHWORTH.

tubes (sensorische Schliuche), partly from their central ter-
minations in the neuroglia of the ventral cord of leeches and
Lumbricus, and partly from their large size, non-refractive
contents, and myelin and neuroglial sheaths. They are
nervous, for they contain the essentially nervous element, the
neuro-fibrillee.

These conclusions are in one way or another at variance
with those of almost every other writer on giant-fibres. In
Crustacea, for example, the central origin of the fibres in
large ganglion-cells of the brain, and their course as deter-
mined by Allen, Bethe, Retzius, is entirely opposed to an
explanation of them as sensory structures. Neither have
they in this group been traced into any connection with
peripheral nerves except by Apathy himself, and his state-
ment is not accompanied by descriptions or figures.1

In Lumbricus and in an increasingly large number of
Polycheetes it has been shown that certain giant-cells of the
ventral cord are directly connected with the giant-fibres,
and it is usually supposed that each cell gives off a process
which fuses with that of the next giant-cell, and so on; but
very rarely do the upholders of this view show that the
giant-fibres so formed possess either a connection with the
fibrous part of the cord (through delicate fibrille or colla-
teral branches or otherwise) or a connection through spinal
nerves with peripheral organs. In the case of Lumbricus,
however, it has been shown that branches of the giant-fibre
do pass into the nerves (Cerfontaine, 1892). Still, if their
origin in giant-cells of the cord can be considered to be
proved (and the cases of Sigalion, Clymene, Axiothea,
certain Capitellids, and we may add Arenicola, are, we

‘ Indications are not wanting in fishes that we must distinguish two groups
of fibres : (1) originating in the medulla, and traversing the length of the cord
without ending peripherally ; and (2) the fibres, such as those described in
Lophius, with central spinal origin and peripheral (probably motor) termina-
tion. It is possible that the giant-fibres of Crustacea correspond to the
first set, those of Annelids to the second. The whole question is urgently
in need of thorough investigation,

ANATOMY AND CLASSIFICATION OF THE ARENICOLIDA. 497

think, beyond doubt), then Apadthy’s interpretation of giant-
fibres as “sensory” can hardly be accepted. What is
wanted more than anything else to settle the question is
an investigation of their peripheral ending by a physiolo-
gical method, such as the results of section of the giant-
fibres, and of the destruction of the giant-cells.

While, at any rate, one result (the exit of fibrils to the
cord) obtained by Cerfontaine (1892) by the use of methy-
lene-blue on the giant-fibres of the earthworm has thus,
at Apathy’s hands, received confirmation, there has been no
corresponding confirmatory work in Polychetes. The ten-
dency of recent research has certainly been to accept the
continuity of giant-cells and some element of the giant-
fibres; but beyond the fine lateral branching of these fibres
observed by Hisig (1887) and Friedliinder (1899), in Masto-
branchus (Capitellidz), there has been no proof of entrance
of the processes into the spinal nerves, nor has any complete
analogy been drawn between the giant-fibres of Polycheetes
and ordinary nerve-elements. This discordance is most
plainly seen in the rarity of statements to the effect that
any connection exists between the giant-fibres and the cord
itself. Hamaker (1898), however, has shown that in Nereis
the giant-fibres are pierced by ordinary nerve-fibres (especially
by his “set B”’) on their course to the periphery. A com-
parison of Hamaker’s fibres (“set B”) with Apathy’s “ sen-
sorische Schlauche ” in leeches suggests, however, that these
fibres are part of the same set of elements to which the
giant-fibre itself belongs: and further, that processes of indi-
vidual giant-cells, which in other Polychztes, form an appa-
rently continuous giant-fibre, may in reality represent a
number of fibres, which though anastomosing and decussat-
ing, yet ultimately escape from the giant-fibre into a spinal
nerve without the adjacent fibrils or axis-cylinders under-
going the intimate anatomical continuity which is sometimes
stated to occur.

At this point the evidence we have obtained from Areni-
cola Grubii has a distinct bearing on the problem, We

498 F. W. GAMBLE AND J. H. ASHWORTH.

have shown that from several, if not from all of the meta-
merically arranged large unipolar ganglion-cells, there arises
in each case a single process which gives off fibrillations to
the cord, both to the right and to the left sides. The process
then enters a giant-fibre, which may divide, some of its
branches entering the spinal nerves, and others, proceeding
for a longer or shorter distance, anastomose with the other
giant-fibres, and again give off branches to nerves. The
structure of the cell-process and giant-fibre is undoubtedly
that of an axon, and corresponds with what Apathy calls
“‘ sensorische Schlauche,” but there is no proof that an inti-
mate fusion of the process of one cell with that of a suc-
ceeding cell takes place. A more successful topographical
method must first be employed to decide this point, and also
in order to determine in what manner the fibrille of the cord
enter the giant-cell, how they are connected through the
collaterals with the axon, and in what way these fibrille run a
recurrent course along the cell process to the giant-fibre and
spinal nerves, and so reach their termination.

p. The Occurrence of Giant-cells in Arenicola.

With reference to the presence and development of giant-
fibres and giant-cells in the different members of the genus
Arenicola, we have ascertained the following particulars.
In the common lugworm (A. marina), a specimen 17°5 mm.
long showed an arrangement of the giant-cells precisely
similar to that described above in A. Grubii. In the great
majority of the segments there were two of these cells placed
in line and near the hinder border of the segment; in the
remainder only one was present. The caudal region was
carefully examined, and giant-cells were found apparently
regularly (in the middle of the tail) two annuli apart. The
cells measured ‘04 mm. in length and about ‘02 in breadth.
They were pyriform, unipolar, and their process extended
towards the dorsal surface of the cord, but was not ascer-
tained to end in the giant-fibre. ‘The nucleus is large, and

1 PL. 29, fic. 80.

ANATOMY AND CLASSIFICATION OF THE ARENICOLIDA. 499

has often two lenticular nucleoli. The protoplasm of the cell
stains but slightly. The neuroglial sheath was less developed
than in A. Grubii, and neither the radiating glial processes
which extend into the cell protoplasm nor the neuro-fibrillz
could be demonstrated so clearly as in that species.

The giant-cells and giant-fibres do not appear to be differ-
entiated in a post-larval specimen 4°5 mm. long. In specimens
50—75 mm. three such cells occasionally occurred in segments
38—6, but they would appear to be less regular and no larger
than in the individual 17°5 long referred to in the preceding
paragraph. In large specimens (250 mm. or even longer) at
least one cell with a very distinct. process prolonged into the
giant-fibre was met with, close behind the union of the
cesophageal commissures.

In Arenicola cristata we examined sections of seg-
ments 11 and 12 and found a single giant-cell in each, in
a position exactly corresponding to the hinder of two cells
of A. marina or A. Grubii (see fig. 81). The preservation,
however, of this and other specimens of the species does not
permit us to add any histological characters.

In A. Claparedii there is, curiously enough, no trace
either of giant-cells or giant-fibres.

In A. ecaudata (150 mm. long) we have found six giant-
cells in segments 2—7, and probably therefore they occur
segmentally throughout the length of the body. They vary
somewhat in size, but attain dimensions as great as those of
A. Grubii, measuring ‘08 mm. in length and ‘048 in depth.
The histology of these cells and their connection with tie
median giant-fibre are identical with those of A. Grubii. A
single process arises from the cell, courses laterally through
the fibrous part of the cord, and ends in the median giant-
fibre. In two post-larval specimens of this species (9°4 and
7-2 mm. long respectively) the median giant-fibre is already
developed, but the giant-cells cannot be made out.

No further description need be given in this place of the
giant cells and fibresof A. Grubii. In adult specimens they
persist, and are apparently as large and well developed as

VOL, 45, PART 3,—NEW SHRIES, MM

500 F. W. GAMBLE AND J. H. ASHWORTH.

those in the example, 78 mm. long, figured in Pls. 28
and 29.

In conclusion it may be said that, with the exception of A.
Claparedii, the median fibre is constant in all species, and
arises from median giant-cells segmentally arranged at the
anterior and posterior ends of the body; while the lateral
fibres are more inconstant, pursue an intricate anastomosing
course, and are related to the giant-cells of the middle region of
the body. The cells are as well, if not better, developed in
immature than in full-sized individuals, and in all cases exhibit
the characters of unipolar ganglion-cells. The exact connec-
tion of the giant-fibre with the cord, and especially the ter-
‘ mination of its branches and of those of the more inconstant
lateral giant-fibres, will require further investigation, but we
have shown that in A. Grubii the branches accompany the
peripheral nerves, and are connected by short offsets with the
fibrous matter of the cord, thereby increasing their likeness
to efferent nerve-fibres.

12. Sense-organs.

The otocysts are the best developed and most characteristic
sense-organs of the Arenicolids. In addition to these,
however, there are (1) the eyes, (2) the sensitive surface of
the prostomium, and (3) the nuchal organ or ciliated groove.
As stated on p. 444, we have not been able to prove that the
cirriform hollow processes of the tail of Arenicola cristata
are definitely sensory, but both these and the tubercles
placed just below the last few pairs of gills (which may also
prove to be reduced cirri) probably contain sense-organs.
The constant and rapid movements of the notopodial bristles
suggest that on these a sensory ending may occur. Indeed,
Retzius (‘ Biologiska Foéreningens Forhandlingar,’ Band 11,
Hefte 4—6, 1891, p. 85) has shown that in A. marina,
nerve-endings may be traced to the bases of these sete.

The Otocysts.—Ehlers (1892) has given an almost ex-
haustive account of these interesting structures, but we have
gone over the ground again, since one species, Arenicola

ANATOMY AND CLASSIFICATION OF THE ARENICOLID®. 501

ecaudata, not examined by him, possesses, according to
Fauvel (1899), otoliths of an entirely different nature from
those of A. Grubii, and also because we do not agree with
Ehlers that there is an open pit in A. Claparedii which
represents the earliest stage in the development of the organ.

The otocysts are a pair of vesicles derived from the skin.
In the common lugworm they open on the surface of the
body just behind the prostomium : more strictly speaking, on
the upper surface of the peristomial segment. In three other
species (A. cristata, A. Grubii, A. ecaudata) the vesicles
are closed, but they lie exactly below the point at which, in
A. marina, they open to the exterior. Finally, in A.
Claparedii there is no sense-organ, but Ehlers claims to
have shown that there is a pair of pits at the corresponding
points on the peristomium. We have examined several
series of sections of Naples specimens of this form, and we
find (Pl. 27, fig. 56, wa) that there is an enlargement of the
metastomial groove at its point of origin behind the pro-
stomium. This enlargement in sections, taken in the same
plane (horizontal) as those figured by Hhlers, occupies the
site of the pit, which he refers to as marking the position of
the otocyst of other forms. In these sections the metastomial
groove is conspicuous on each side from the dorsal to the
ventral surface of the animal. The position of the otocyst (in
those species which possess the organ) lies slightly dorsal to
the point of intersection of the second transverse groove
behind the nuchal organ with this metastomial groove. This
point lies dorsally and to the inner side of the metastomial
pit of A. Claparedii, but we find no trace of any depression
in this species which can be accurately localised with the
point of origin of the otocyst. Ehlers states that the pit to
which he refers as marking this site is in no way modified ;
there is no special sensory epithelium, and no special oto-
cystic nerve. After careful examination we have concluded
that there is in this species no trace of the otocyst, nor is it
possible to localise the position it occupies in other forms
by any particular diverticulum of the metastomial grooves.

502 F. W. GAMBLE AND J. H. ASHWORTH.

This entire absence of any trace of the otocysts in A.
Claparedii is very remarkable, since in other species of the
genus these sensory organs are perfectly constant, and, so
far as is known at present, they are unrepresented in any
of the families (Maldanide, Opheliide, Scalibregmide,
Capitellide) with which Arenicola shows a more or less
close degree of resemblance according to the organs under
consideration.

In A. marina the structure of the otocyst and the nature
of the otoliths are both well known. In describing the
cesophageal connectives we pointed out that the nerve to the
otocyst arises from them, and is strongly ganglionated. We
have now only to add that in post-larve 4°5 mm. long, taken
while swimming freely in their gelatinous tubes, the otocysts
contain minute quartz-grains covered by a delicate chitinoid
film. This seems to point to the conclusion that these young
stages are not strictly pelagic, but that they sik to the
ground for a longer or shorter period of time, and probably
are disturbed by the incoming tide and so brought near the
surface, for it was at high tide that our specimens were taken
at Lytham by Mr. Ascroft. Wilson’s observations on the
habits of very young A. cristata show that the true early
larval stage is a free-swimmer, but that later on the animals
sink to the bottom and creep about while retaining the power
of swimming.

Of the three remaining species the otocysts of only one
specimen of A. cristata have been examined by khlers,
with whose account we are in full accord. There is only a
single otolith, chitinoid in nature, which appears to increase in
size with the age of the Arenicola. A small specimen of
this species, 47°5 mm. long, had an otolith of lenticular shape,
and measuring ‘07 mm. in length, ‘028 mm. in width, and
‘(056 mm. in thickness; while in another example from
Naples, 300 mm. long, the cavity of each otocyst measured
‘018 mm. in diameter, and the almost spherical otolith 013
by 012 mm. We have fully confirmed Ehlers’ statement
that in this species the otocyst is closed; in fact, the

ANATOMY AND CLASSIFICATION OF THE ARENICOLID®. 508

chitinoid otoliths appear to be correlated with a closed
vesicle,

We are unable to give a detailed account of the structure
of the wall of the otocyst in this species, as our specimen
was not sufficiently well preserved. The cells of the wall
are of two kinds,—columnar supporting cells and fusiform
sense cells; and the cavity of the vesicle possesses a dis-
tinct cuticular lining (PI. 27, fig. 65). The nerve-supply to
the organ is derived from the cesophageal connectives.

In A. ecaudata and A. Grubii the two otocysts (Pl. 27,
fig. 64) have the same relative position (peristomial) as in the
two former species. ‘They are closed vesicles, into the base
of which a sheet of muscle derived from the body-wall is
inserted, as Ehlers has described in detail for A. Grubii.
The long columnar cells forming the wall of the otocyst are
of two kinds—sense cells and supporting cells. The former
end in one or more delicate points which project through the
cuticular lining into the fluid with which the vesicle is filled.
Around the basal ends of these columnar and sense cells, there
is a slight amount of connective tissue, and in it is embedded
a plexus of nerve-fibrils—the termination of the nerve to the
otocyst,—which enters the organ at its outer and under side
and spreads out over its surface (Fig. 64, N. Sh.). The special
development of ganglion cells on the course of this nerve and
at its point of origin from the connective is described in con-
nection with the nervous system (p. 479).

The otoliths of perfectly fresh specimens of both these
species, often, but not always, exhibit the peculiar rotatory
movement which was first described by Quatrefages in the
otocyst of the common lugworm. It is best seen if the
otocyst is rapidly dissected out under sea water. If the
lugworms are not quite healthy the movement of the otoliths
does not occur, and these cases of immobile otoliths are
probably due to some alterations in the fluid inside the
otocyst. We have examined the lining of the vesicle very
carefully without detecting any trace of cilia, and we are
inclined to consider the movement due to diffusion currents,

504 F. W. GAMBLE AND J. H. ASHWORTH.

although it has precisely the same appearance as the move-
ment of the otolith of certain Lamellibranchia, e. g. Cyclas,
which is caused by ciliary action.

In post-larval A. ecaudata there is only a single minute
otolith, which floats in the viscous fluid with which the
vesicle is filled. The otolith is spherical, 7 « in diameter,
and has a minute central granule. As the worm increases in
size this otolith becomes larger and others arise, but the first
one always remains conspicuous from its larger size. In full-
grown specimens the large otolith measures ‘036 to ‘04 mm.
in diameter, and the small ones ‘003 to ‘01 mm. They are
all spherical, somewhat yellowish, highly refractive bodies;
with slight indications of concentric lamination. Hach is
covered by a thin transparent envelope. In the centre of
each otolith there are usually a few dark granules. ‘The
characters of the otoliths in A. Grubii agree precisely with
the foregoing description.

The chemical reactions of the otoliths in A. Grubii have
been somewhat fully recorded by Hhlers, with whose state-
ments and results we are in full accord. ‘Ich halte,” says
Ehlers, “die Substanz dieser Otolithen danach fir eine,
welche dem Stoffe gleich kommt, der die Cuticula und die
Borsten bildet.””. The chief ground for this conclusion is the
behaviour of the otoliths on the addition of acids. Weak
hydrochloric and strong acetic acids have no effect. Strong
hydrochloric acid, however, causes the otoliths to swell,
become clear, and lose their original shape; but while these
alterations are going on there is no trace of the evolution of
gas. We have obtained exactly the same result. Further,
on placing the otoliths in eau de Javelle they become more
transparent, especially if slightly warmed, and at the same
time lose their refringent character. ‘The otoliths apparently
arise in the glandular cells of the otocyst wall, and are
discharged into the fluid filling the cavity when they are
still minute (1 mw or so in diameter). In the fluid they
gradually increase in size, but appear never to attain a greater
diameter than 40 p.

ANATOMY AND OLASSIFICATION OF THE ARENICOLID®. 505

All these characters point to the otoliths being chitinoid in
nature. The absence of gas bubbles under treatment with
acids, precludes the possibility of carbonates having any
share in their composition.

Fauvel, however, though accepting this conclusion for the
otoliths of A. Grubii,! states that those of A. ecaudata (a
Species not examined by Ehlers), when treated with Perenyi’s
fluid, react quite differently, and that those of the former
species stain with hematoxylin, while those of the latter
do not. ‘The black granules enclosed in the otoliths of
A. ecaudata acquire “laspect d’inclusions du quartz. Ce
sont probablement des fines bulles gazeuses produites par
action des acides sur le carbonate de chaux au sein d’une
masse solide ou pateuse qui s’oppose 4 leur fusionnement en
une grosse bulle.’ Further on he adds, “ Les reactions des
otolithes avec les colorants indiquent qwils sont probablement
de nature chitineuse au moins dans leur parti périphérique ”’
(1899, p. 25).

With the exception of the last sentence our experience is
entirely at variance with that of M. Fauvel. We find that
the otoliths of A. ecaudata, when treated with acids weak
and strong, cold and warm, with alkalies, and with staining
reagents, agree in their reactions in every particular with
those of A. Grubii, and we conclude that in both species the
otoliths are chitinoid in nature throughout, and do not contain
any trace of carbonates, nor do they give off gaseous bubbles
on treatment with acid. As mentioned above (p. 504), there
are in the centre of some of the fresh otoliths of both
species (before treatment with acid) a few small inclusions.
Some of these are spherical, and look almost like small gas
bubbles having refringent walls, but they are in reality
minute spherical granules. Some of the included granules
are elongated, rod-like bodies, and others are somewhat
irregular in shape.

1 This author (1889, p. 25) mistakes the ground for Ehlers’ conclusion that
the otoliths are a secretion of chitinoid nature, since he says that the Gottingen
zoologist obtained no result with hydrochloric acid,

506 F. W. GAMBLE AND J. H. ASHWORTH.

The Nuchal Organ.—The general appearance of this
ciliated groove has been described in the section (pp. 439, 440)
dealing with the external characters. It is a single, curved,
narrow depression of the prostomial epidermis, and corre-
sponds to the pair of grooves in Maldanids, and to the pair of
eversible “ Wimperorgane” in Capitellids and Opheliide.
The epithelial cells which line it are of different kinds.
Some are secretory, others sensory, many are ciliated, and
these are the only ciliated cells which occur in the epidermis.
At their bases the epithelial cells are continuous with the
ganglion cells of the posterior brain lobes.

The Hyes.—These structures were discovered in larve
and post-larve of A. cristata by Wilson (1882-3), but
they have only been recently re-described by Mesnil (1897)
in specimens of what the author considered to belong to the
genus Clymenides, Clap. More recently he has entirely
given up this conclusion, and has referred his specimens to
species of the genera Arenicola and Branchiomaldane.
We are able to show that eyes of an extremely simple struc-
ture occur in the post-larvee of three species of Arenicola,
and in the adult stages of all species.

In the only trustworthy embryological account of Areni-
cola (the paper by Wilson on A. cristata, 1883) two eyes
appear on the prostomium when the larva is only a day old,
and they persist up to the latest stage that Wilson obtained
(fifteen days old, with six chetigerous segments). In
sections of a Jamaican specimen, 7°5 mm. long, we can still
see embedded in the anterior brain lobes several eye-specks,
each consisting of a mass of brown spherical pigment granules
arranged round a clear central body which projects anteriorly
somewhat like a lens. The structure of these organs is not
well preserved.

In A. marina (PI. 24, fig. 34, Oc.) there are, during the
post-larval stage, four to five eyes on each side of the prosto-
mium embedded in the ganglionic layer of the brain. They
measure ‘008 mm. in diameter, and consist of a cup-shaped
mass of brown pigment granules partially enveloping a clear,

ANATOMY AND CLASSIFICATION OF THE ARENICOLIDE. 507

solid-looking body which projects outwards. Similar eyes
are found in specimens of the common lugworm, 25 mm. long.
It is difficult to say whether they persist throughout life,
owing to the quantity of pigment in the prostomium increasing
with the age of the animal.

In specimens of A. Claparedii (17 and 26 mm. long)
there are three to four eyes in the deeper parts of the
prostomial epithelium and between the ganglion cells of
the anterior cerebral lobes. The largest measure ‘01 mm.
in diameter, and are provided with a layer of red pigment
granules.

In A. Grubii and A. ecaudata we have obtained the
clearest preparations of the eyes. In a post-larva of the
latter species, 7°2 mm. long, there are about twelve eyes on
each side of the prostomium along the greater part of its
length. They were arranged in two linear series, one on
each side. Occasionally two eyes occur close together, and
one or two are placed nearer the median line than the rest.
The eyes measure ‘01 mm. in diameter, and consist of a clear,
lens-like structure pointing outwards and upwards: of a
transparent, less highly refractile central portion: and of a
hemispherical coat of sepia-coloured, rounded pigment
granules (Pl. 27, fig. 63 a).

The anterior eyes are placed in the nervous layer, imme-
diately below the epidermis and on the course of the nerves
given off from the front edge of the commissural brain to
supply the prostomium. Further back the eyes are sunk in
the ganglionic layer of the brain itself.

In full-grown specimens of A. ecaudata (six to seven
inches long) the eyes are still present, and apparently more
numerous than in the post-larval stage. They measure ‘012
mm. in diameter, and are now partially surrounded by a red
pigment in the form of minute spherical granules. They
occur in the same regions as before, but are also found in the
median brain lobe which underlies the nuchal organ.

In their simple form and deep situation the eyes of
Arenicola recall those of Mastobranchus (Capitellide),

508 F, W. GAMBLE AND J. H. ASHWORTH.

which they also resemble in structure. The earliest stage
in the development of the eye of Nereis, figured by
Andrews (1892, pl. xii, fig. 60), is directly comparable with
the grade of structure which these organs retain in Areni-
cola. The brown or red pigment is very distinctive, and
unlike the black pigment with which the epidermis is gene-
rally loaded.

The remaining sensory structures of Arenicola are the
sense-cells of the surface of the prostomium, and possibly the
notopodial sete. Whether the scattered epidermal sense-
cells which have been found in Axiothea and Clymene by
Lewis (1898) occur in Arenicola we cannot state, as we
have not specially investigated the subject, but, judging
from the general similarity between these forms in the
nervous systems and other sense-organs, it 1s very probable
that peripheral sense-cells will be found in Arenicola.

13. Nephridia.

The nephridia of A. marina have been investigated by
several anatomists. The general form and blood-supply
of the organ have been recorded by Cosmovici (1880),
Cunningham (1887), Benham (1891, 1893), Kyle (1896), our-
selves (1898),and others. The detailed histology of the adult
and post-larval nephridium has so far only been described in
detail by Benham (1891, 1898). The chief points of interest
as yet undecided are the origin of the nephrostome, the
changes which the whole organ undergoes at different periods,
and the relation of the gonad to it.

The nephridia of A. Claparedii have never been fully
described, and the only drawings relating to them are found
in Jaquet’s paper on the vascular system of Annelids (1886).

The nephridia of A. cristata have never been investigated,
and the descriptions of the organs in A.Grubii by Claparéde
(1868), and in A. ecaudata by Fanvel (1899), merely relate
to the general form of the adult organ without reference to its
condition in the post-larva or to its finer histological structure.

The genus Arenicola may be divided into two sections by

ANATOMY AND CLASSIFICATION OF THE ARENICOLID™. 509

means of the characters of the nephridia, the first section con-
taining A. marina, A. Claparedii, and A. cristata, the
second A. ecaudata and A. Grubii.

I. The nephridia of the “marina” section agree through-
out. Hach consists of a funnel or nephrostome, a secreting
portion, and a posterior terminal vesicle or bladder (Pl. 24,
fie. 29). The funnel is always bright red in colour, owing to
its rich vascular supply. Its narrow slit-like aperture, which
is generally directed forwards and inwards, is bordered by
an entire plain ventral lip, and a somewhat large dorsal
lip fringed by ciliated vascular processes which are placed
moderately close together on the edge of the lip. The pro-
cesses are flattened, spatulate, or triangular structures fixed by
their narrower end to the lip of the nephridium; their flat
faces are turned towards each other. Hach process, which
may be branched distally into two, three, or four, contains a
large blind diverticulum of the blood-vessel which traverses
the edge of the dorsal lip; hence the processes are always
bright red. The free edge of the ventral lip is almost semi-
circular. The edges of both dorsal and ventral lips are
richly ciliated, and there are also very numerous long cilia
within the mouth of the funnel, the motion of which is very
obvious in fresh nephridia examined on a slide in sea water.
The secreting portion of the nephridium is a moderately thin-
walled sac, usually dark brown, sometimes almost black in
colour, owing to the presence of enormous numbers of brown
excretory granules in the cells lining the sac. ‘The secreting
portion of the nephridium tapers posteriorly and opens into
the bladder, which is also usually brownish in colour. When
expanded the bladder is more or less spherical, but in the
contracted condition it is rosette-like. Hach bladder opens
to the exterior by a small oval aperture just above and
behind the dorsal portion of a neuropodium.

Immediately behind the posterior portion of the nephro-
stome there is a small whitish or pinkish, ovoid, club-
shaped, or cylindrical mass of cells. These masses of cells
are the reproductive organs of the worm, ovaries or testes, as

510 F. W. GAMBLE AND J. H. ASHWORTH.

the case may be. They are not present on the first pair of
nephridia. A further account of these structures is given
below, p. 521.

A. marina.—There are six pairs of nephridia opening on
the fourth to ninth chetigerous annuli. The smallest speci-
men of A. marina which we have obtained from the sand is
13:5 mm. in length (in spirit), but as it is somewhat contracted
its length when living would probably be about 17 mm. The
nephridia of this specimen, which are about *5 mm. long, have
already assumed the adult form. The funnel is of consider-
able size and has well-marked lips, the dorsal one bearing from
three to five short, blunt, conical elevations, which later on
become the large spatulate processes of the older nephridium.
The secreting portion of the first nephridium is a rather wide,
almost §-shaped tube; that of the following nephridia is much
wider and sac-like. There is a very rich vascular supply to
all parts of the nephridium. Ina specimen 44 mm. long the
nephridia are about a millimetre in length. There is little
change from the condition described above, except that all
the parts are larger; the dorsal lip of the nephrostome bears
from four to seven small blunt conical processes, and the
secretory portion is larger and more sac-like. A nephridium
from this specimen is figured in our previous paper (1898,
pl. iv, fig. 16).

Nephridia of large specimens may attain a length of 8 mm.
The funnel of such nephridia is large, and its dorsal lip bears
as many as thirty-two large spatulate processes, often branched
into two, three, or four distally. The processes are placed
slightly obliquely on the dorsal lip, i.e. a line drawn parallel to
their flat faces does not cut the lip of the nephridium at right
angles. The first pair of nephridia of A. marina is unrepre-
sented in any other species of the genus. Their nephrostomes
are situated anterior to the third diaphragm, and the external
opening is on the fourth chetigerous annulus. In all other
species the first nephridium is situated in the segment pos-
terior to this one, with its external opening on the fifth
chetigerous annulus. ‘The first nephridium of other species

ANATOMY AND CLASSIFICATION OF THE ARENICOLIDS. 511

corresponds in position to the second nephridium of A.
marina.

The first and last nephridia of A. marina are subject to
considerable variation; the first pair especially are often
appreciably smaller than any of the succeeding nephridia.
Out of about 160 specimens examined, we have found eight
instances, in each of which there is some considerable de-
parture from the normal condition. Six of these specimens
show reduction or loss of the first nephridium. In one case
the first nephridium of each side is very small, its secreting
portion being only as thick as an ordinary pin; in a second
example the first nephridium of the left side is normal, but
that of the right side has no funnel; in a third specimen the
first nephridium on each side has no funnel; in the fourth
and fifth examples the first nephridium of one side has a very
small funnel, while the corresponding one of the other side is
represented by a funnel only; and in the sixth specimen the
first nephridium of the left side is totally absent, the corre-
sponding right one being present but without funnel.

In the other two instances of variation the last nephridia
are affected. In a large specimen (250 mm. in length) the
sixth nephridium of the right side is normal, but the corre-
sponding one of the left side consists of funnel only. Another
specimen, 100 mm. long, has only five pairs of nephridia
opening on the fourth to the eighth chetigerous annuli, the
sixth pair being totally absent.

From the above records it is evident that the funnel and
the rest of the nephridium are to some extent formed in-
dependently, for in the examples of A. marina mentioned
above there are four cases in which the funnel is absent, and
three in which the nephridium is represented by a funnel only.

The first nephridium in A. Grubiiis sometimes represented
by a funnel only (see p. 513), and we have also dissected and
figured a specimen of this species in which a funnel is present
in the segment behind the last normal nephridium (PI. 26,
fig. 54).

It therefore appears probable that the funnel develops at

012 F. W. GAMBLE AND J. H. ASHWORTH.

first quite separately from the rest of the nephridium, and
only subsequently fuses, as is known to be the case in other
Annelids. The post-larval nephridium, in fact, is only com-
parable to, e. g., the nephridium of the earthworm minus its
funnel. (For further remarks on this point see p. 519.)

A. Claparedii.—The five pairs of nephridia present in this
species open on the fifth to the ninth chetigerous annuli.

The nephridia are much smaller than those of A. marina,
seldom exceeding 4 mm. in length. The dorsal lip bears
ten to fifteen large ciliated, spatulate, or sometimes almost
reniform processes, several of which may be divided distally
into two or three (PI. 24, fig. 29). The first nephridium bears
no gonad, but in other respects resembles the succeeding
nephridia, and is not usually reduced in any way. In only
one example have we found any variation from the normal.
In this, a specimen about 80 mm. long, there are five
nephridia on the left side, but only four on the right, the first
one being absent.

In all our specimens of this species the secreting part of
the nephridium is not brown, but light yellow, there being
very few excretory granules present in the cells of the ne-
phridia of even large (80 mm. long) specimens. The secretory
portion of the nephridium tapers gradually posteriorly and
opens into the well-marked spherical or rosette-like vesicle.

A. cristata.—There are six pairs of nephridia in this
species opening on the fifth to tenth chetigerous annull.

The Jamaican specimen, 47°5 mm. long, has very elongate
slender nephridia about 2 mm. in length. The funnel of each
bears about fifteen to twenty flattened processes, some of
which are already divided into two or three distally. The
nephridia of a large Neapolitan specimen (300 mm. long) are
naturally much larger, being 11 mm. to 15 mm. in length.
The dorsal lip of the funnel bears twenty to thirty processes
similar in shape and arrangement to those of A. marina.
The secretory portion is brown and the vesicle small and
rosette-like (being contracted in our specimens). ‘The ne-
phridia of the large American specimen, 860 mm. long, attain

ANATOMY AND CLASSIFICATION OF THE ARENICOLIDA. 5013

a very large size, some of them being over 20 mm. in length
(Pl. 24, fig. 30). In this specimen there is a seventh com-
plete nephridium on the right side, but only the normal
number (six) on the left side.

II. The nephridia of the second section of the genus—
containing A. ecaudata and A. Grubii—differ from those
described above in several constant characters.

They seldom exceed 7 mm. in length even in the largest
specimens of these species. The vascular ciliated processes of
the dorsal lip are less flattened than those described in the pre-
ceding section; they are stouter, cylindrical, and digitiform,
generally branched distally. ‘The most obvious difference is,
however, seen on examining the ventral lip, which in these
two species is deeply notched in the centre, the two halves
into which it is thus partly subdivided being semicircular
in shape. The dark brown secreting portion of the nephri-
dium and the rather lighter coloured vesicle are similar
to, but not quite as sharply demarcated as those of A.
marina.

A. Grubii.—There are five pairs of nephridia, opening,
as in A. Claparedii, on the fifth to ninth chetigerous
annuli (Pl. 25, fig. 44).

In a specimen 35 mm. long the nephridia are 1°3: mm. to
1°6 mm. long. The dorsal lip bears about eight short un-
branched vascular processes. The nephridia of full-grown
specimens are 4mm.to 7mm. long. The processes of the
dorsal lip are comparatively few in number, there being
usually only about 12-15 (figs. 53, 54). They are stout,
digitiform or club-shaped outgrowths, often divided into two
or occasionally three, distally. There is no sharp distinction
between the middle and terminal portions of the nephri-
dium. The terminal part is often drawn out into an irregular
somewhat foot-shaped sac (fig. 53). There is a reduction of
the first nephridium in two of the specimens we have exa-
mined. In an adult specimen from Port St. Mary the first
right nephridium is represented by a funnel and the first left
one is absent, there being only four nephridia on the left

514 F. W. GAMBLE AND J. H. ASHWORTH.

side. In another specimen the first left nephridium is repre-
sented by a very small funnel, but all the other nephridia are
complete. There is an interesting abnormality in a full-
grown specimen from Naples. There is on the right side,
in the segment posterior to the fifth or last nephridium, a
small funnel about one millimetre long (fig. 54). It consists
of a well-marked dorsal lip traversed by a large blood-
vessel, and bearing six stout, club-shaped, ciliated vascular
processes. ‘I'he ventral lip of the funnel is small and feebly
marked.

A. ecaudata.—There are thirteen pairs of nephridia open-
ing on the fifth to the seventeenth chetigerous annuli.
They resemble those of A. Grubii except that the funnel is
often a little narrower from side to side, and that the
dorsal lip bears a greater number of processes. All the
nephridia, except the first pair, bear gonads, which are indeed
the most characteristic feature of a dissection of this species
(see p. 455, and figs. 45, 46, 48). The nephridium of full-
grown specimens is 5 mm. to 7 mm. long, and the dorsal lip
bears from about fifteen to twenty-five processes, many of
which are subdivided distally; in some specimens there
are five, six, or seven branches, but in most specimens only
two or three. The secreting portion of the nephridium is
usually less stout than that of A. Grubii. The bladder is
generally large. In mature females of this species ripe ova
sometimes accumulate in the vesicle of the nephridium in
very large numbers. In such specimens there is produced
on the inner side of the nephridium a thin-walled, sac-like
outgrowth of the vesicle, 3 mm. to 4 mm. in length, through
the semi-transparent walls of which the large ripe ova may
be seen (fig. 47).

Although we have examined very many specimens of this
species we have not met with any case of reduction or loss of
nephridia, but Fauvel (1899) states that the number of ne-
phridia is only occasionally thirteen, twelve being the usual
number, the last pair of nephridia being absent from his
specimens.

ANATOMY AND CLASSIFICATION OF THE ARENICOLID™. 515

Histology of the Nephridia.—There is a close simi-
larity between the different species of Arenicola in refer-
ence to the histology of the nephridia. The lips of the
nephrostome are lined by a single layer of ciliated columnar
cells. In young specimens the cells are small, and the
greater part of each cell is occupied by the deeply stain-
ing nucleus, but in older specimens in which the cells are
much larger, the nucleus occupies only a small portion of
the cell. Immediately within the mouth of the funnel of
A. ecaudata and A. Grubii there are numerous long ridges
or corrugations, which converge towards the entrance to the
secreting part of the nephridium. This region of the funnel
is very richly ciliated, and in fact, if a living nephridium
be examined in sea-water on a slide, the ciliary action is
most obvious in this portion of the organ.

There is a moderately sharp line of demarcation between
the cells of the funnel, which are columnar, strongly ciliated,
and have no concretions; and the cubical columnar or pear-
shaped cells of the secretory portion of the nephridium, which
even in young specimens contain some excretory granules.

Sections of young specimens show that the cells lining the
middle portion of the nephridium are ciliated on their inner
ends, and their somewhat vacuolated protoplasm contains
only comparatively few concretions.

In old specimens, however, concretions are very numerous,
and in the nephridia of a full-grown specimen of A. ecaudata
which we have cut into sections the concretions are of two
different kinds (Pl. 26, fig. 49). The columnar or pear-
shaped cells which line the secretory portion of these ne-
phridia are about 20 to 30 winlength. ‘The distal portion
of the cell which projects into the nephridial cavity is quite
clear, nothing but the very thin cell-wall being visible, looking
almost like a “collar.” The protoplasm of the middle por-
tion of the cell (for a distance of about 10) contains
numerous minute, more or less spherical granules, which stain
quite black with iron-hematoxylin ; while in the protoplasm of
the basal portion of the cell there is often a considerable mass

VOL, 43, PART 3.—NEW SERIES, NN

516 F. W. GAMBLE AND J. H. ASHWORTH.

of small spherical yellow granules which are not stained by
hematoxylin. In another specimen of the same species the
distal fourth of the cell is almost hyaline, containing only a
small amount of granular protoplasm; and the concretions,
which are in this example all yellow, are situated in the
middle part of the cell only. In nephridia from full-sized
specimens the cells invariably present the appearances
described above, the distal portion of the cell being very
constantly free from granules. Granules are discharged
from the cells into the cavity of the nephridium, as we have
found rather large collections of yellow excretory granules
in the lumen of the organ. We believe each cell bears a
long cilium, but it is very difficult to distinguish between
cilia, the very thin walls of the distal portion of adjacent
cells, and also the fibrils of the coagulum in the nephridial
cavity ; but we have seen in some preparations cilia similar to
those drawn by Benham in A. marina (1891, pl. xxv, fig.
41). In this case, as in A. ecaudata, each cell bears a
single moderately long flagellum (about 5 in length) on its
clear distal end.

Both the funnel and the secreting portion of the nephri-
dium are covered by a thin layer of ccelomic epithelium. In
the middle region of the secretory portion of the organ there
is a very thin, almost structureless layer, apparently of the
nature of connective tissue, between the secretory cells and
the coelomic epithelium, while in the walls of the posterior
portion, i. e. the vesicle, there is a thin layer of muscle-fibres
in a corresponding position between the two cell layers. In
young specimens the cells of the vesicle contain fewer granules
than those of the secreting portion of the nephridium, but in
old specimens there is little difference in this respect between
the cells of the two regions.

Blood-vessels of the Nephridia.—All the nephridia
of the various species of Arenicola (except the first and
second of A. Grubii and A. ecaudata) are supplied with
blood by segmentally arranged branches of the ventral vessel.
The first nephridia of A, Grubii and of A. ecaudata are

ANATOMY AND CLASSIFICATION OF THE ARENICOLID®. 517

supplied by a branch from the dorsal vessel, and the second
nephridia by a branch from the dorsal longitudinal vessel
(Pl. 25, figs. 44, 45, D.D.V.).

The afferent nephridial vessel, given off from the ventral
vessel, divides on approaching the nephridium, one branch
passing to the setal sac and body-wall (and to the gill when
present), and the other to the nephridium. The latter goes
directly towards the nephrostome, but generally just before
reaching it, divides, sending off a branch to the anterior
secretory portion of the nephridium (fig. 53). The vessel
then enters the nephrostome, its main portion traversing
the dorsal lip close to its edge and sending a blind vessel
into each ciliated process. Immediately after entering the
nephrostome the vessel gives off a branch to the ventral lip,
and from this and from the vessel of the dorsal lip, numerous
small vessels pass to the two lips of the funnel, forming a
close network upon them. Benham has pointed out (1891)
that in A. marina some of the vessels on the funnel have
blind dilated terminations. We have also found similar
blindly-ending vessels on the funnels of A. Grubiiand A.
ecaudata (figs. 46, 48).

After traversing the dorsal lip of the nephrostome, the
large vessel leaves it at the posterior angle, where it is
usually joined by the vessel which has traversed the ventral
lip. Itis sometimes also joined by a vessel from the anterior
secreting part of the nephridium. The vessel so formed is
the gonidial vessel, which runs parallel to and appled to, the
secreting part of the nephridium, ramifying on the posterior
part of this portion of the organ and on the bladder. The
cells covering the anterior portion of the vessel proliferate
and give rise to a mass of reproductive cells. No gonad is
formed on the gonidial vessel of the first nephridium in any
species of Arenicola. In A. ecaudata and A. cristata
the gonad extends along the greater part of the vessel, in the
former species covering the vessel from the point at which it
leaves the funnel almost until it reaches the vesicle of the
nephridium (figs. 46, 48),

518 ¥. W. GAMBLE AND J. H. ASHWORTH.

The anterior portion of the secreting part of the nephri-
dium is supplied with blood by a vessel given off from the
nephridial vessel just before entering the nephrostome ; while
the posterior portion and the bladder are supplied by the
gonidial vessel. The branches of these vessels form a close
network upon the nephridium (figs. 46, 48), which is well
developed even in young specimens (Gamble and Ashworth,
1898, pl. v, fig. 18). As pointed out by Benham (1891),
the network of vessels lies between the secreting epithelium
and the ceelomic epithelium which covers the nephridium
(fig. 49).

In A. Claparedii there is a tuft of filiform, blindly-ending
vessels given off from the gonidial vessel as it leaves the pos-
terior angle of the nephrostome (Pl. 24, fig. 29). These
vessels, which are 1 to 2 mm. long, are free at their distal
blind ends. They have very thin walls, on some of which
small brown cells (probably chlorogogenous) may be seen.
A few similar vessels are also given off all along the course
of the gonidial vessel, but they are found chiefly in the region
of the gonad. A few arealso given off the afferent nephridial
vessel before it reaches the nephrostome. Similar vessels
are also found in A. Grubii in association with the vessels of
the body-wall in the region of the nephridia (Pl. 26, fig. 54).
The blindly-ending vessels given off from the gonidial vessel
of A. Claparedii, are probably homologous with the similar
vessels which grow out from the gonidial vessel of A.
ecaudata, and around which the gonads are developed,
though in the former species these vessels are not associated
with the gonad in any way.

The first three nephridia of A. marina, the first two of
A. Claparedii, and the first of A. cristata return blood to
the dorsal vessel. The blood from the fourth nephridium of
A. marina,! the third of A. Claparedii, and the second and

1 Since writing our previous paper (1898) we have found thatin A. marina
the vessel printed in red on Plate 2, fig. 5, and lettered WV. H7:*, is not, as it
appears to be, a blood-vessel with thick walls, but is a solid cord of connective
tissue which accompanies the afferent vessel (WV. 47-*) of the fourth nephridium

ANATOMY AND CLASSIFICATION OF THE ARENICOLIDA. 519

third of A. cristata is collected into vessels which open into
the parietal vessel or into the nephridial vessel. The remain-
ing nephridia of these three species return blood to the sub-
intestinal vessel (Pl. 24, figs. 26, 30).

The blood which passes through the nephridia of A:
Grubii, and all except the last two nephridia of A. ecau-
data, is returned to the Jongitudinal nephridial vessels, which
are much more highly developed in these two species than in
the other three species (Pl. 25, figs. 44, 45, and Pl. 26, figs.
53, 54).

Nephridia of Post-larval Stages—A. marina.—
As in the adult, there are six pairs of nephridia, opening
near the fourth to the ninth neuropodia. The first nephri-
dium is in some cases smaller than the others (see Benham,
1898, p. 52). We can confirm Benham’s account of the
structure of these organs of the post-larva in all particulars.
The nephridium is a simple, slightly bent tube, opening
anteriorly into the ccelom by a small round or oval aperture,
which is ‘quite simple, i.e. there is no funnel. ‘The nephri-
dium is of almost uniform diameter throughout, and its
walls are formed of a single layer of columnar or cubical
ciliated cells covered by an exceedingly delicate layer
of ccelomic epithelium. In our specimen (4°5 mm. long)
the cells of the nephridium are apparently all alike, but
Benham found in a post-larva (6°8 mm. long) probably a
little older than ours that the cells of the anterior part of
the nephridium contain excretory granules which are not
present in the cells of the posterior portion. In our specimen
45 mm. long the nephridia are ‘12 mm. to *15 mm. in length,

along its course from the ventral vessel to the nephrostome. It is generally
whitish, but sometimes pinkish in colour in life, and may readily be mistaken
(as it has also been by Milne Edwards and Cosmovici) for a blood-vessel with
thick walls. Such, however, is not the case ; it is a strand of connective tissue
homologous with the strand occurring in exactly the same position in A.
cristata and A. Grubii. Thus the first efferent vessel passing to the sub-
intestinal vessel in A. marina, is in the segment behind the one which bears
this deceptive connective-tissue strand, i.e. in the first gill-bearing segment,

520 ¥. W. GAMBLE AND J. H. ASHWORTH.

while in Benham’s specimen the nephridia are about *3 mm.
long.

A. ecaudata.—A post-larva, 7°2 mm. long, was embedded
in paraffin, and cut transversely as far back as the beginning
of the nephridial region. The remainder of the specimen
was afterwards cut sagittally until the middle line, as indicated
by the nerve-cord, was reached; the paraffin was then
thoroughly removed from the portion of the worm still in the
paraffin block by solution in xylol, and the half of the ali-
mentary canal remaining in the body of the worm dissected
out, thus leaving only the body-wall and the nephridia
attached to it. The object was then transferred to thick
cedar-wood oil, in which it became transparent, thus enabling
the observer to examine the nephridia in detail. The object
as it now appears is represented in Pl. 26, fig. 50.

The nephridia of this specimen are all provided with
funnels ; the anterior ones are large, but the posterior ones
are much smaller. The thick lips of the funnel are formed
by cubical ciliated cells, the greater part of which is occupied
by the deeply staining nucleus. The long cilia of these cells
hang into the mouth of the funnel. On the dorsal lip of the
second nephridium there is at one point a small conical heap
of cells, the commencement of the first vascular process of
the lip. ‘The funnels of several of the nephridia are bent
or twisted upon themselves ; those of the last four or five
nephridia are smaller and simpler than the anterior ones,
The funnels of the ninth and tenth nephridia are connected
to the secreting portion of the organ by an elongated narrow
tube (‘06 mm. and ‘1 mm. in length respectively) ; those of
the other nephridia are almost sessile upon the secreting por-
tion of the organ. ‘The secretory portion of the nephridium
is a somewhat irregular, thin-walled, hollow sac, the walls of
which are formed by a single layer of ciliated columnar cells
which contain very numerous excretory granules, which stain
black with iron-hematoxylin. There is no line of demarca-
tion between the secretory and terminal portion of the
nephridium. The cells of the latter also contain excretory

ANATOMY AND CLASSIFICATION OF THE ARENICOLID’. 521

granules, though not quite in such large numbers as those of
the middle portion of the nephridium. ‘The whole nephridium
is covered by a very thin layer of coelomic epithelium. In
both this and another post-larva we have carefully examined
the segments anterior and posterior to those in which the
nephridia occur, but have found no traces of rudimentary
nephridia in these segments.

14. Reproductive Organs.

The reproductive organs of A. marina have been described
by Cosmovici (1880), Cunningliam (1887, 1888), Kyle (1896),
and others, but until very recently these organs had been
investigated in this species only. Our former paper (1898,
p. 33) contains the first reference to the large and complicated
gonads of A. ecaudata, and a brief description of them has
been subsequently given by Fauvel (1899).

The reproductive organs of Arenicola are closely asso-
ciated with the nephridia. Immediately behind and con-
tinuous with, the posterior portion of the nephrostome there
is a small whitish or pinkish mass of cells, ovoid, club-shaped,
or cylindrical (Pl. 24, fig. 29, and Pl. 26, figs. 53, 54). This is
one of the reproductive organs, ovaries or testes as the case
may be. The gonad is developed around, or in contact with,
a large branch of the afferent nephridial vessel, which we may
call the gonidial vessel. The afferent nephridial vessel, after
giving off a branch to the sete and body-wall, generally gives
off a branch to the secretory portion of the nephridium, the
main portion of the vessel traversing the dorsal lip of the
nephrostome. On entering the nephrostome, this vessel often
gives off a branch which runs across the ventral lip, and joins
the vessel from the dorsal lip again as it leaves the nephro-
stome (Pl. 26, figs. 46, 48). The vessel which leaves the
nephrostome and runs down the inner side of the secretory
portion of the nephridium is the gonidial vessel, and around
this the gonad is developed by proliferation of its peritoneal
covering.

522 F. W. GAMBLE AND Jj. H. ASHWORTH.

Gonads are not present on the first pair of nephridia, but
the gonidial vessel has the usual position and relations. On
the first nephridia of A. ecaudata (as will be further
described below) there is, however, a distinct strand of tissue
homologous with the genital strand, and occupying a similar
position, but not producing reproductive cells (Pl. 26, figs.
46, 48, C. Str.). The gonad is a closely packed mass of cells,
in which at the anterior end, i.e. at the end in contact with
the nephrostome, the cells are small, almost uniform in size,
and have well-marked, deeply staining nuclei. In the middle
and posterior portions of its length, the cells on the surface of
the gonad become differentiated, and in females young ova,
in males young spermagonia, may be recognised. ‘The
anterior portion of the gonad is covered by a thin layer of
coelomic epithelium, but the portion of the gonad from which
young ova or spermagonia are being shed is not covered by
an epithelium. ‘The ova remain attached to the gonad until
they have attained a diameter of 16 to 20m. On reaching
this size they are shed from the surface of the ovary into the
coelom, where they complete their development. At the sur-
face of the testes there may often be seen groups of two, four,
or eight cells—young spermagonia,—which at this stage are
shed into the cclom and there undergo the numerous
divisions resulting in the formation of the large masses of
spermatids figured in our former paper (1898, PI. 5, fig. 34).
‘hese remarks on gonads apply to all the species except
A. ecaudata, in which the reproductive organs are much
more complicated (see p. 524).

The goviidial vessel is developed on the nephridia in very
early life. It may easily be recognised in a specimen of A.
marina 17 mm. long; and in the last four nephridia of a
specimen of A. Grubii 35 mm. long, the cells of the peritoneal
covering of the gonidial vessel have already begun to pro-
liferate, and have given rise, fora distance of ‘0 mm. to’6 mm.
to a cylindrical covering of small uniform reproductive cells
with well-marked nuclei. In A. marina the gonads do not
appear until the specimens are somewhat larger ; e.g. they

ANATOMY AND OLASSLFICGATION OF THE ARENICOLID®. 523

are exceedingly small but just recognisable in a specimen
44 mm. long.

In full-grown specimens of A. marina the gonad on the
last five pairs of nephridia is a somewhat elongated, club-
shaped, or cylindrical body, from *4.mm. to 1 mm. in length,
surrounding the gonidial vessel immediately after it leaves
the funnel. Cosmoevici (1880) says that there are six pairs of
gonads, but in all our specimens there are only five, the first
nephridia not bearing gonads.

In A. Claparedii the gonad which is present only on the
last four pairs of nephridia occupies a similar position to
that of A. marina. It is ovoid or club-shaped, and about
‘4mm. to ‘9 mm. long (Pl. 24, fig. 29).

As in the two preceding species, the first nephridium of
A. cristata bears no gonad, but the gonidial vessel is
present. The gonidial vessel of the other five pairs of
nephridia is thinly covered by genital tissue from the point
at which it leaves the posterior portion of the nephrostome
almost until it reaches the vesicle, a distance of 5 mm. to
7 mm. in the specimen shown in PI. 24, fig. 30.

The gonadsof A. Grubii appear early, being already present
on the last four pairs of nephridia of a specimen 35 mm. long.
At this stage the gonad consists of a small cylindrical mass
of small uniform cells with well-marked nuclei covering the
gonidial vessel, but it is impossible yet to say whether they
will give rise to ova or spermatozoa. In the adult the gonad
is a club-shaped or cylindrical structure, 1:3 mm. to 15 mm.
long, surrounding the gonidial vessel (Pl. 26, figs. 53, 54).
The first nephridium has a well-developed gonidial vessel,
but no genital cells are formed upon it. The cells covering
the vessel are brown in colour, due to the presence in them
of chlorogogenous granules.

The gonads of A. ecaudata differ considerably from those
of any other species, being larger, more complicated, and
more numerous, there being twelve pairs (Pl. 26, fig. 45).
On each side of the nephrostomes of this species there is a
strand of cells which, owing to the numerous well-marked

524 F. W. GAMBLE AND J. H. ASHWORTH.

nuclei of its cells, stains deeply with haematoxylin, carmine,
etc. (Pl. 26, figs. 46, 48). Only one of these strands (Gen.
Str.), the longer one nearer the middle of the body of the
animal, gives rise to gonads. The other strand (C. Sér.),
which is shorter, often bears small heaps of cells produced by
proliferation of the strand ; these possibly give rise to coelomic
corpuscles.

Both these strands are present on the first pair of
nephridia of this species, but the genital strand in these
nephridia always remains small and thin, being discernible
as a thin covering on the inner side of the gonidial vessel,
and never giving rise to gonads. In the posterior nephridia
of a young female specimen about 120 mm. long the gonad
very much resembles that of an adult A. Grubii. It is a
cylindrical mass of cells, thickened somewhat posteriorly,
surrounding the gonidial vessel for a distance of about
1:5 mm. behind the nephrostome. It is not possible to say
with certainty from an examination of this gonad whether
the cells will give rise to ova or spermatozoa. The gonads
of the anterior nephridia of this specimen are rather more
advanced, and they already show young ova.

In adult specimens the genital strand runs from its point of
origin on the funnel, parallel with, and closely applied to, the
secretory portion of the nephridium along its whole length.
From this strand, which is traversed axially by the gonidial
vessel, the large genital organs of the adult are produced.

In the female the genital strand soon gives rise to a few
digitiform outgrowths, which at first are small, blunt, and
conical, but later they become more numerous (there may be
twenty to thirty), elongated and flattened, or filiform, attain-
ing a length of 3 to 5 mm. (PI. 25, fig. 45, and Pl. 26, fig. 46).
At first the cells of these processes, which are obviously
young ova, are nearly equal in size, being about 15 mw in
diameter, and having large vesicular nuclei. In old speci-
mens, however, each process bears ova in every stage of
development, from the smallest recognisable to the almost
ripe ova, which are surrounded by their thick conspicuous

ANATOMY AND CLASSLEICATION OF THE ARENICOLID®. 525

vitelline membrane. Young ova are found along the axis of
each process in close association with the vessels which
traverse the process. They are, in fact, formed from the cells
covering the vessel, just as are the gonads of other species
(Pl. 26, fig. 51).

The vessels passing into the processes are at first blind
outgrowths of the gonidial vessel (as recorded by Fauvel,
1899, p. 27) ; but later, when two or more vessels are present
in one process, there are transverse connections which place
the vessels of the process in intimate communication with
each other (fig. 52). These vessels are probably homologous
with the tuft of blind vessels given off from the gonidial
vessel of A. Claparedii (Pl. 24, fig. 26), but in the latter
species they are not associated with the gonad, their cellular
covering being chlorogogenous.

The genital strand of the female A. ecaudata, which is of
considerable thickness, is covered by a layer of unaltered
epithelium, which also covers each process, and which is
ruptured when the ova are shed into the ccelom (fig. 51).
The genital strand and the processes arising from it, may be
regarded as the ovary of this species, which thus reaches a
greater size and complication than that of any other species
of Arenicola.

In males there are also two strands commencing on each
nephrostome and running backwards, the one only a short
distance, but the other closely applied to and along nearly
the whole length of, the secreting portion of the nephridium.
Only the latter, which is on the inner side of the nephridium,
gives rise to gonads. From this strand there is produced on
the inner side towards the middle line, one (or in some cases
two or three or even four) pinkish, greyish, or milk-white,
thin reniform outgrowths, which may attain a length of
5 mm. to 7 mm., and a breadth of 3 mm. to 5 mm. (fig. 48).
The thickness of these reniform sacs is only about a milli-
metre. Hach contains spermatozoa in all stages of develop-
ment. ‘he gonidial vessel which runs through the genital
strand gives off several branches into the reniform lobe.

526 F. W. GAMBLE AND J. H. ASHWORTH.

The cells covering these branches of the gonidial vessel give
rise to male genital cells; and the younger stages in their
development are therefore found in close association with
the blood-vessels of the lobe. The male genital cells are at
first small, uniform in size, and have large, sometimes
vesicular nuclei. ‘hese soon undergo divisions resulting in
the formation of stages in the development of spermatozoa
similar to those which are found in the ccelomic fluid of
other species (see Gamble and Ashworth, 1898, Pl. 5,
figs. 830—34). As in the female, the superficial portion of.
the genital strand is unaltered epithelium, which also forms
the outer membranous covering of the reniform lobe within
which the developing spermatozoa are contained. ‘The
branches of the gonidial vessel divide freely among the
developing spermatozoa, so that every portion of the reni-
form lobe is well supplied with blood. The genital strand
and the reniform lobe (or lobes) together form the testes of
the worm.

In other species the reproductive cells leave the small
gonad at a very early stage of their development, and com-
plete their development while in the coelomic fluid. In
A. ecaudata the reproductive organs are large, being
produced in one or more outgrowths covered by epithelium,
and well supplied with blood-vessels. ‘The reproductive
cells retain their connection with the gonad for a much
longer period, and in fact are not discharged until they are
nearly ripe. Hence reproductive cells in an advanced stage
of development only are found in the coelomic fluid of this
species.

When the ova have attained a diameter of about 16 to 20 p,
they break through the ccelomic epithelium of the gonad
and fall into the ccelom (except in A. ecaudata, in which
they are retained until they are almost ripe). The nucleus
increases in size and becomes vesicular, its diameter being
about half that of the ovum. ‘There is generally also a well-
marked germinal spot or nucleolus. Very small yolk granules
are deposited in the protoplasm. They are most abundant

ANATOMY AND CLASSIFICATION OF THE ARENICOLIDA. 527

round the nucleus, the peripheral portion of the protoplasm
containing very little yolk (fig. 51).

The ripe ova of the various species are almost equal in
size. Those of A. marinaare the largest. They are gener-
ally spherical, about ‘16 mm. in diameter, and have a distinct
but thin vitelliine membrane. The ripe ova of A. Claparedii
are spherical, or sometimes rather oval, about «14 mm. in
diameter, and similar in every respect to those of the common
lugworm. ‘The spherical or slightly oval ova of A. cristata,
which are about ‘14 mm. in diameter, have a rather thick
vitelline membrane, thus differing from the two species pre-
viously mentioned. The ripe ova of A. Grubii and A.
ecaudata are identical in shape, size, and other characters.
They are generally oval in shape, though some are spherical.
The average length of their longer diameter is ‘13 mm. to
‘14mm. They have a thick vitellme membrane (fig. 51).

The spermatozoa of all species of Arenicola develop in a
manner similar to those of A. marina, briefly described in
our former paper (1898, p. 32, and Pl. 5, figs. 29—84).
Except in A. ecaudata the male genital cell falls from the
testes after two or three divisions, and completes its develop-
ment while in the ccelomic fluid. Further divisions result in
the formation of a disc-shaped mass of spermatids containing
a central cavity in which there is a small coagulum, the
remains of the blastophore. We have hitherto seen only the
ripe spermatozoa of A. marina (1898, Pl. 5, fig. 29), but
those of A. Grubii have been seen and figured by Claparéde
(1868, p. 299, and Pl. 19, fig. 2, ¢.). The latter closely
resemble those of A. marina, except that they are somewhat
smaller.

The genital products escape by means of the nephridia.
Although the first pair of nephridia do not bear gonads they
nevertheless, like the other nephridia, serve as genital ducts.
The terminal portions of the nephridia are, during the breed-
ing season, often distended with ova or spermatozoa. In a
specimen of A. marina, 200 mm. long, the vesicles of some
of the nephridia measured 14 mm, in length and about

528 F. W. GAMBLE AND J. H. ASHWORTH.

6 mm. in width owing to distension by ova, while in another
specimen the vesicles of the nephridia were filled with sperms,
and were 5 mm. in length and 4 mm. broad. In mature
females of A. ecaudata ripe ova accumulate in large num-
bers in the vesicles of the nephridia, producing on the inner
side of the vesicles thin sac-like outgrowths which may attain

a length of 4 mm. to 5 mm. (fig. 47).

15. The Specific Characters and Classification
of the Arenicolide.

The characters which cheetopodists have relied upon when
separating the different species of Arenicola, and which
are in general use throughout the Polychetes, are furnished
by the external organs. The general divisions of the body,
the arrangement and structure of the gills, parapodia, and
sete, are thought sufficient to differentiate one species from
another. The internal anatomy has not been so carefully
studied from this point of view, with the exception of the pro-
stomium and otocysts, which have been carefully examined by
Ehlers. The result of his work was, amongst other things,
to show that, with reference to these organs, the species exhi-
bited a series of developmental stages. The otocysts, for
instance, proved to be very different in A. Grubii from those
of A. marina, while they are absent (or, as Ehlers concluded,
merely indicated) in A. Claparedii. With the exception
of this paper, however, there has been no attempt to show
how far the internal organs furnish evidence for specific
characters. It has been thought that external features were
sufficient.

The result of this idea of the sufficiency of obvious marks
is well shown by the confusion of different species under one
name, and by the same form at different stages of growth
receiving different names. As an example of the first kind
of mistake we may refer to the doubt which has so long
hung over the specific identity of A.ecaudata. Named
originally by Johnson in 1835, it has been confused with A,

ANATOMY AND CLASSIFICATION OF THE ARENICOLIDA. 529

Grubii so long that even Ehlers himself doubted it being a
distinct form. Yeta moment’s glance at the internal anatomy
would show that it is by far the most smgular species of the
genus, in possessing voluminous complex ovaries or testes
and a larger number of nephridia than any other member
of the family. The confusion between A. Claparedii and
A. marina is another case due largely to the exclusive value
set upon external features in discriminating species.

The second class of error, that of regarding young forms ofa
given species as distinct from it, is due not only to the lack
of comparison between the internal organs of young and old
stages, but also to the lack of perception of the important fact,
that even such features as sete and gills, are not precisely
similar in form in the post-larva as in the adult. In fact,
there are two kinds of variation which systematists have to
reckon with,—developmental variation in such organs as sete,
of which several different sets appear in an individual’s life-
time ; and variation in the homologous organs of the indi-
viduals of a species. If it can be shown that the first kind
of variation in the case of any organ, e. g. sete, is as great
as, and similar to, the variation of the second kind, then
such an organ ought not to be employed for accurate specific
diagnosis. By disregarding this principle, Mesnil (1897)
recently published a paper which contained an account of
some form intermediate between the Arenicolide and Mal-
danide. These intermediate forms were referred to the
genus Clymenides of Claparéde, on the ground of external
characters, setzee and the absence of gills. Further, Mesnil
endeavoured to prove that the post-larval stages of Areni-
cola marina, described fully by Benham (1893) from speci-
mens taken at Plymouth, were in reality also members of
this genus Clymenides, which he regarded as combining
characters found in Arenicolide# and Maldanidz, and as
forming a parallel series to the species of Arenicola. Soon
after the publieation of this paper, however, another appeared
by the same author, in which he showed that his so-called
species of Clymenides were partly species of Arenicola

530 F. W. GAMBLE AND J. H. ASHWOR'H.

and partly of Branchiomaldane, a form described origi-
nally by Langerhans from the Canary Islands.

These examples suffice to show, first, that the two kinds of
variation must be ascertained ; and second, that the internal
organs must be reckoned within an attempt to base the classi-
fication of the members of the genus on a firm footing.

The question, then, which is raised by these considerations is,
What variation do the organs of Arenicola exhibit in differ-
ent specimens and in the growth of the individual? When
the range of these variations is known, the systematic arrange-
ment of the growth-stages and the adults will be more soundly
based than heretofore. The gills and sete may first be
considered, as they are usually held to be diagnostic. With
reference to the gills we have shown that the common lug-
worm has two varieties of the gill, a pinnate and a dendritic
type. The pinnate type also occurs in A. cristata and less
conspicuously in A. Claparedii. ‘These three species cannot
then be separated by appealing to the form of the gill-plumes,
though as a group they are clearly separated by their common
type of gill from the two remaining forms, A. Grubii and
A. ecaudata, in which the mode of branching is quite dis-
tinct, but which agree so closely inter se in the matter as
to be indistinguishable on this character alone. With regard
to the development of the gills, different post-larvalindividuals
of A. marina vary in the time of origin and relative degree
of growth of these organs, but in all cases the gills appear to
arise in the centre of the future branchial region and spread
forwards and backwards. Accordingly until the full number
is attained it would be impossible to separate any of the three
caudate species of Arenicola by the position and number of
their gills.

The setze show very much the same kind of variation.
Their form and characters are gradually changing through-
out life, so that there are very considerable differences
between the sete of a given species taken from specimens of
different age, differences more considerable in some cases than
between the sete of specimens of the same age but of different

ANATOMY AND CLASSIFICATION OF THE ARENICOLIDA. 581

species. For example, the neuropodial cheete of post-larval
stages of A. ecaudata are totally different from the crotchets
of a full-grown specimen, but after examining a long series
of preparations we cannot find any constant feature by
which the crotchets of full-grown A. ecaudata may be
distinguished from those of full-grown A. Grubii. There
are differences between adult individuals of A. marina, and
there is a considerable amount of difference between the
early post-larval sete and those of the full-grown worm.
In the post-larva there are two kinds of notopodial bristles
(spear-shaped and capillary), and three kinds of neuropodial
ones (one-, two-, and three-hooked ), and among the latter the
subrostral processes may be distinct, faint, orabsent. Again,
as Mesnil has pointed out, setze identical in form with those
of neuropodia occur in the notopodia of early post-larval A.
ecaudata, disappearing later on, and the same holds true
for A. cristata. When we further consider that the differ-
ences between the sete of any of the species is not greater
than the difference between the earlier and later formed sete
in one individual, the systematic value of these organs
becomes in this genus practically nil, although by contrast
with other genera they may have a certain generic value,
though this is lessened by the distinctly Maldanid character
of the sete in the post-larval stages (the curved rostrum and
the subrostral process of the neuropodial crotchets, and the
hastate notopodial sete).

The prostomium has not usually been employed for dis-
criminating species, since it is often concealed in the nuchal
groove. Moreover anyone who has examined a long series
of A.ecaudata and A. Grubii will realise how apparently
identical are the prostomial outlines and indentations. But
we are able to show that A. cristata and A. marina have
quite as similar prostomia, and further that in A. Claparedii
there is considerable range of variation, though none of the
terms approach to A. marina or A. Grubii. In this respect,
however, A. Claparedii is well separated by its compara-
tively large and well-developed prostomium.

VOL, 43, PART 3.—NEW SERIES, 00

53h) F. W. GAMBLE AND J. H. ASHWORTH.

We have tested an external character which has not been
hitherto much examined—the number of nephridiopores. Of
these there are six pairs in A. marina, the last five of which
are present in Claparedii, cristata,andGrubii. A.ecau-
data is, however, easily separated by the thirteen pairs; the
first five of these correspond with those of A. Grubii.
Partly, then, because of the close agreement of three fourths
of the genus, partly because of the difficulty of detecting the
apertures in contracted specimens, the number of nephridio-
pores can only be ancillary in systematic work.

On the whole, then, it must be admitted that the external
characters usually relied upon by chetopodists fail to sepa-
rate the species of Arenicola, for though they may be of
generic value, the specific differences which they afford are
either paralleled by individual variation, or are too slight to
admit of satisfactory definition. It therefore behoves us to
seek diagnostic characters in the features of the internal
anatomy.

'wo years ago we came to the conclusion that Arenicola
Grubii and A. ecaudata form a separate section of the
genus, characterised by the suppression of the prostomium,
the extension of parapodia and gills to the hinder end of the
body, and by the possession of closed otocysts, with at first
one and afterwards many otoliths, which are secreted from
within, not introduced from without. Mesnil has come to the
same conclusion, and has suggested a separate genus Areni-
colides for these two forms. Such a step appears to us inad-
visable. The reduction of the prostomium, and pari passu
the simplification of the “brain,” form the most important
character which could be adduced to support the erection of
anew genus; for the posterior extension of parapodia and
their associated structures, though very valuable for practical
purposes of determining forms, is a feature shared by Bran-
chiomaldane, and a posterior extension occurs occasionally
in A. cristata. The peculiarity of the otocysts is nearly
paralleled by A. cristata, which possesses a closed vesicle,
but only a single large otolith of endogenous origin. Finally,

ANATOMY AND CLASSIFICATION OF THE ARENICOLIDA. 533

the presence of thirteen pairs of nephridia and the large
genital sacs appended to them (except the first pair) in A.
ecaudata is a feature by which this species is sharply dis-
tinguished from all the rest. ‘The balance of evidence does
not seem sufficient to justify the union of A. Grubii and A,
ecaudata into a distinct genus, although they form a distinct
section of the genus.

The genus Arenicola may, then, be divided into two
sections, the first containing A. marina, A. Claparedii, A.
cristata, characterised by a well-marked prostomium, a well-
developed brain with anterior and posterior cerebral lobes,
the presence of six pairs of nephridia in segments 4 to 9
or five pairs in segments 5 to 9, and the absence of the
gills and parapodia from the posterior region. ‘The second
section contains A. Grubii and A. ecaudata, with simple
conical non-lobate prostomium and commissural brain, and the
gills and setigerous sacs continued backwards to the pygidium,

Of the first section A. Claparedii is the most distinct.
The prostomium is complexly folded, and produced laterally
into short hollow processes into which the anterior cerebral
lobes are extended. The otocysts are absent. The meta-
stomial grooves are very distinct, and expanded at their origin
just behind the nuchal groove. ‘This expansion has been
previously considered (Khlers) as indicating the position of
otocyst, but there is a similar expansion of the groove in A.
marina, and it does not occur in the region accurately corre-
sponding to the opening of the otocyst. Internally, the
multiple cesophageal glands and the absence of diaphrag-
matic pouches are distinctive. Five pairs of nephridia are
present.

A. marina and A. cristata are closely similar to each
other in many points, such as the prostomium, brain, and
many of the external characters. The former, however, has
two additional pairs of gills. The presence of anephridium in
the third chetigerous segment, opening just behind the fourth
row of neuropodial chet, and the possession of an external
aperture to the otocyst, and presence of foreign particles

534, F. W. GAMBLE AND J. H. ASHWORTH.

serving as otoliths, distinguish A. marina. A. cristata
sometimes, but by no means always, has small cirriform pro-
cesses on the achetous caudal region. One diagnostic feature
of A. cristata is the closed otocyst with its single large
otolith formed by secretion of the walls of the vesicle, and in-
creasing in size apparently throughout life. There are six
pairs of nephridia and sometimes a seventh, but the first pair
correspond to the second nephridia of A. marina.

Enough has already been said to differentiate the members
of the second section. The large number of nephridia and
the size of the gonads readily separate A. ecaudata from A.
Grubii, which has only the five pairs of nephridia found in
some of the first section of the genus. The gills commence
on the sixteenth chetigerous segment in A. ecaudata, on
the twelfth in A. Grubii; and this arrangement is so constant
that in rare cases (A. Grubii) where the gills commence on
the thirteenth segment, the first branchiferous segment should
then be reckoned really as equivalent to the second in the
typical arrangement. The arrangement of afferent and effer-
ent vessels, and their presence, even when the true first gill is
very small (or absent), fully confirm this manner of regarding
the position of the first gill as a really fixed point. In this
connection we may remark that it would conduce to reliable
systematic work if the doubtful species A. branchialis,
Audouin and Milne-Edwards, were altogether neglected, since
the original description does not accord with that of any
accurately known species of Arenicola; no naturalist has found
an undoubted specimen of that form, though many have
worked at the locality (St. Vaast) where it was obtained by
Audouin and Milne-Edwards. Lastly, the original speci-
mens at Paris and those named by Johnston in the British
Museum have been lost.

Having settled the diagnostic features of the species of
Arenicola as seen in adult forms, we must now shortly dis-
cuss how the post-larval stages can be discriminated, using
the term post-larval in the sense already indicated, as imply-
ing an Arenicola with the full number of segments, but in

ANATOMY AND CLASSIFICATION OF THE ARENICOLIDM. 585

which the gills were either not present or not in the full
number.

Hitherto only three species have been seen in this stage,
A. marina, A. cristata, and A. ecaudata, and each of
these differs from the adult in the arrangement and the form of
the gills, sete, and to a lesser extent the form of prostomium ;
but can only be adequately determined by the nature of the
otocysts, cesophageal pouches, and nephridia. The gills arise
in A. marina as hollow papille in the centre of the branchial
region, and are marked by their efferent and afferent vessels.
Their rate of development appears to vary, but possibly is
constant for the young of the ‘ Laminarian ” or pinnate-gilled,
and “littoral” or dendritic-gilled varieties respectively.
Hence the gills are not valuable for determining this species.
The absence of cheetz from the tail gives a characteristic
appearance to that region, but probably A. Claparedii is
similar in this respect, though its post-larval stage has not
been described. ‘The cheetz themselves differ in A. marina
from previous descriptions of the post-larva. Notopodially
there are hastate and capillary forms; neuropodially the
crotchets have the rostrum bent very strongly on the axis,
and above it there may be one or two (rarely three) teeth ;
below it a minute process is often present. Weare thus com-
pelled to fall back on the internal organs; and the combination
of their characters—the open otocyst with foreign otoliths, the
single pair of oesophageal pouches, and the small pair of
nephridia in the third chetigerous segment unrepresented in
any other species at present known—sufiices, and is only suffi-
cient, to characterise post-larval A. marina.

Somewhat similar is the case with A. ecaudata. It is
probable that the post-larval stage of A. Grubii will soon be
known; indeed, since the latter is the commoner of the two
it is singular that its post-larval stage has not already been
met with. ‘lhe post-larvee of either could be differentiated by
the sectional character—the extension of neuropodia and
notopodia almost to the hinder end of the body, and the
otocysts ; from each other by the presence in A. ecaudata of

536 F. W. GAMBLE AND J. H. ASHWORTH.

thirteen pairs of nephridia, in A. Grubii of five pairs. The
characters derived from the setze are even more inapplicable
here than in previous cases, since A. Grubii and A. ecau-
data are closely similar in this respect, except that we find
(with Mesnil) that a crotchet identical with those of the
neuropodia occurs temporarily in the notopodia of each of
the last six segments or so of A. ecaudata 10 mm. long
(Pl. 24, fig. 37).

These considerations lead one to a fairly wide definition of
the genus as a whole. The absence of the otocysts in A.
Claparedii unfortunately prevents the presence of these
organs being recognised as of generic value, but undoubtedly
they are one of the most critical points. Before, however,
deciding what the limits of the genus should be, it is neces-
sary to discuss Branchiomaldane, a small hermaphrodite
form, the structure and development of whichis partly known
from the work of Langerhans (1881) and Mesnil (1898).
This form (for specimens of which we are indebted to the kind-
ness of M. Mesnil) is 8 to 20 mm. long, and becomes mature
when of the latter dimensions. It lives in transparent
““mucus’’ tubes attached to calcareous alge in the English
Channel, and also inthe Canary Islands. The prostomium is
somewhat larger than that of specimens of Arenicola ecau-
data of the same size, but is similarly conical and provided
with two lateral groups of eye-spots. The peristomium is
achetous (and next segment?) ; the following segments, of
which there may be thirty-three to fifty-one, bear notopodia
and neuropodia. The notopodial sete are intermediate be-
tween those of post-larval A. marina and A. ecaudata,
while the neuropodial crotchets resemble those of A. marina
in every point. The distinctive character is found in the gills,
which only commence in the hinder region (segments 18 to 21),
and occur as simple or slightly bifurcated filaments up to the
pygidium, those of the central part of the branchial region
being larger and bearing more processes (four) than the re-
mainder, which are simple, bifid, or trifid. This character
is considered of generic value by Langerhans, and accord-

ANATOMY AND OLASSIFICATION OF THE ARENICOLIDE. 537

ingly Mesnil has included Branchiomaldane as a second
genus of the family Arenicolide. Further distinctive features
are derived from the nephridia, the absence of otocysts, and
especially the sexual maturity of these hermaphrodite worms.
One or two of the early developmental stages are roughly
figured by Mesnil.

Before accepting this conclusion we may be permitted to
add some observations made on the specimens with which
M. Mesnil kindly supplied us. We have only been able to
find in a specimen 11 millimetres long, which we cut into
transverse sections, two pairs of ducts opening on the fifth and
sixth chetigerous annuli. Moreover very distinct apertures
in these segments occur in all our specimens, but Mesnil (1898)
describes a specimen 15mm. long, “les organes segmentaires
plus ou moins pigmentés de noir dans les somites 7, 8, 9, 10.”
In the later paper he states, ‘‘Il n’y a que quatre ou cing
paires de nephridies.”’ The two pairs of tubes in our sections
have no funnel, and resemble the nephridia of a post-larval
Arenicola in structure and relations. They contain gonads,
and apparently function as ducts. More recently Fauvel
(1899) has stated that there are three to five pairs of ne-
phridia in segments 5—9.

A point in which this Branchiomaldane differs very
widely from Arenicola is the mode of origin of the gonads.
Both ovaries and testes are found in the lateral section of the
ccelom in the tail region. They certainly are not confined to
the nephridia or the nephridial region, unless there be a large
number of larval nephridia which disappear at a very early
stage. ‘The absence of the otocysts we have confirmed. The
gills are outgrowths of the body-wall, with ccelomic cavities
containing afferent and efferent blood-vessels.

On the external characters alone there is little to be said
against including Branchiomaldane in the family Areni-
colide. The question is whether the absence of otocysts,
the hermaphrodite character and peculiar mode of origin of
the gonads taken together form a stronger claim for affinity
to Arenicolide or to the Maldanide. Now one species

538 F. W. GAMBLE AND J. H. ASHWORTH.

of Arenicola (A. Claparedii) is without otocysts, but all
have at least five pairs of nephridia, and in all species of this
genus the gonads arise directly from the peritoneal cover-
ing of the vessel supplying the nephrostome. On the other
hand, Maldanide have three to four pairs of nephridia (in
segments 5—8), they have no otocysts, and in so far
Branchiomaldane agrees with them. No Maldanid, how-
ever, is known which possesses gills, though Johnstonia
clymenoides has small processes on the posterior segments
which have not been fully described, and which may prove to
be respiratory, though their multiple character in each seg-
ment renders it unlikely that they are homologous with the
gills of,e.g., Arenicolaor Branchiomaldane. The account
of the origin of the gonads by Cosmovici (1879) in Clymene
is the only record we are aware of in the family, and shows
that they are as intimately connected with the nephridial
vessel asin Arenicola.

On the whole the evidence seems to show that Branchio-
maldane should provisionally be included as a distinct genus
in the Arenicolidee. .

The characters of the family thus constituted may be stated
as follows. The body is cylindrical, elongated, and divisible
into two or three regions in addition to the prostomium.
The gills are present either in the middle region, in which
case the posterior section is acheetous as well as abranchiate,
or in the middle and posterior sections, which together form a
single cheetiferous region, but they are never present in the
anterior seven segments. In structure, the gills of Branchio-
maldane represent an arrested stage of A. marina. The
prostomium though small is distinct, and is bounded pos-
teriorly by the ciliated groove or nuchal organ. In shape it
is conical or trifolate, with lateral hollow lobes. The peri-
stomium and next following segment appear to have fused in
the adult into an achetous mass. This region, however, in
post-larval stage is subdivided, and bears a vestigial seta
(as shown in A. marina by Benham, and in A. ecaudata
by Mesnil) which we have failed to demonstrate satisfactorily.

ANATOMY AND CLASSIFICATION OF THE ARENICOLIDM, 539

This seta belongs to the segment following the peristomium.
It is tempting to regard (with Ehlers) the otocysts as a pair
of modified dorsal cirri belonging to the peristomium. The
constant position of these organs, the nerve supply from the
same part of the cesophageal commissures, establish the
homology of the otocysts, but their absence in A. Claparedii
and Branchiomaldane, and the absolute lack of knowledge
of their mode of development, render it impossible to prove
this morphological explanation of them as modified dorsal
peristomial cirri.

The parapodia are but slightly indicated by a transverse
neuropodial thickening with vertical row of crotchets, and
conical notopodia with capillary sete. The gills do not
appear to be modified cirri, since in development they are not
preceded by sensory structures, but arise at once as re-
spiratory organs.

Internally there are two or more pairs of cesophageal
pouches. The heart contains a ‘cardiac body” of partly
glandular, partly muscular nature, except in A. Claparedii
and A. cristata, where it is absent. Complete septa occur
in the tail region of the caudate forms, and through
the greater part of the branchial region in the ecaudate
species.

There are constantly three strong septa or “ diaphragms ”
at the beginning of the first, third, and fourth chetigerous
segments. Five, six,and thirteen pairs of nephridia occur in
different species, but altogether they occupy fourteen seg-
ments (4—17). The development is only known in A.
cristata. In Arenicola generally, the gonads develop on
the peritoneal covering of the gonidial vessel, and pass out
by the nephridia themselves. The segmentation of the egg
in A. cristata is complete but somewhat unequal. The
larva is telotrochous, with a ventral band of cilia and with a
pair of eye-spots, and swims freely for a day or so ; afterwards
forming a gelatinous case, and developing its seements and
other adult organs. Hence the metamorphosis is very
slightly marked so far as is known. ‘he various descrip-

540 F, W. GAMBLE AND J. H. ASHWORTH.

tions by Max Schultze, Horst, Cunningham, and others, of
the development of A. marina have not been made from
egos and larvae which indubitably belong to this species or
even genus. While, if Mesnil is right in regarding Bran-
chiomaldane as an Arenicolid, its development is entirely
without metamorphosis, judging from his description and
figures.!

The following statement contains a summary of the charac-
ters of the genus and species (Woodcut, p. 542).

Arenicola.

Limnivorous Polycheta provided with numerous pairs of
branched gills, not present on the anterior seven segments.
Prostomium small or moderately well developed, bounded
posteriorly by the nuchal organ. There are no tentacles or
palps, Parapodia consisting of transversely thickened neuro-
podia, each bearing a vertical row of crotchets, and of conical
notopodia bearing sete. In the chetigerous region of the
body, except in the first three segments, there are four
annuli between successive chetigerous annuli. Internally
there are three strong diaphragms at the anterior end of the
first, third, and fourth somites. There is no armature to the
pharynx. A pair of hearts places the gastric vessels in
communication with the ventral vessel. There are five, six,
or thirteen pairs of nephridia. A pair of peristomial otocysts
present except in A. Claparedii.

I. A distinct tail present, the parapodia and gills not
extending to the posterior end of the animal. The body is
often swollen anteriorly. Gulls pinnate or derivable from
pinnate type, eleven to thirteen pairs, the first gills (some-
times small) on the seventh chetigerous segment. Well-
marked prostomium consisting of a median and two lateral
lobes. Brain well developed, with anterior, middle, and
posterior lobes.

Nephridia with dorsal lip well provided with flattened
spatulate ciliated vascular processes; ventral lip ciliated

1 Mesnil (1898), p. 636, figs. 1—5,

ANATOMY AND CLASSIFICATION OF THE ARENICOLID®. 541

entire. Gonad small. Found on both sides of the North
Atlantic and on the western coasts of America.

(a) A. marina. Thirteen pairs of gills (the first may be
reduced), dendriform or pinnate. Otocysts opening to the
exterior. Otoliths many, composed of foreign bodies (quartz
grains, etc.). Six pairs of nephridia opening on segments
4—9. One pair of cesophageal pouches, cylindrical, club-
shaped, or conical. Diaphragmatic pouches (on the first
diaphragm) small, globular, or flask-shaped. Ova spherical,
with thin vitelline membrane.

(b) A. Claparedii. Lateral lobes of prostomium well
developed. Thirteen pairs of gills, pinnate. No otocysts.
Five pairs of nephridia opening on segments 5—9. 'I'wo or
more pairs of cesophageal pouches, papilliform, digitiform, or
filiform. No diaphragmatic pouches. Ova spherical, with
thin vitelline membrane.

(c) A. cristata. Eleven pairs of gills, pinnate. Otocysts
closed, spherical sacs, each containing a single large spherical
chitinoid otolith. Six pairs of nephridia opening on segments
5—10. Cisophageal pouches as in A. marina. Diaphrag-
matic pouches large and finger-shaped. Ova spherical, with
moderately thick vitelline membrane.

II. No tail, the parapodia and gills continued to the pos-
terior end of theanimal. Body generally of uniform diameter.
Number of gills variable, gills branched unilaterally. Pro-
stomium simple, conical, non-lobate. Brain commissural.
Otocysts closed spherical sacs, otoliths spherical. Diaphrag-
matic pouches long and finger-shaped. Cisophageal pouches
flask-shaped. Nephridia with dorsal lip bearing somewhat
cylindrical, digitiform, often branched, ciliated vascular pro-
cesses ; ventral lip deeply notched in the middle, the two
halves semicircular in shape. Ova generally oval, with thick
vitelline membrane.

(a) A. Grubii. First gill on segment 12 (may be small),
five pairs of nephridia opening on segments 5—9. Gonad
small. ‘Twelve to twenty-eight pairs of gills.

(b) A.ecaudata. First gill on segment 16. Thirteen pairs

542 F. W. GAMBLE AND J. H. ASHWORTH.

es | 0 IN!

A

G1 ~NIDB A

—

A. ecaudata. A grubii. Amarina. Acristata. A.caparedii.

The first twenty chetigerous segments of five species of Arenicola to show
the chief external characters. The horizontal lines represent the
boundaries between the segments. Prost. Prostomium. O#. Otocyst.
N.O.-}3 Nephridiopores. Br.!~** Gills.

ANATOMY AND CLASSIFICATION OF THE ARENICOLIDH. 543

of nephridia opening on segments 5—17. Gonads large,
twelve pairs; in females each ovary bears as many as thirty
digitiform vascular processes bearing ova; in males each
testis is produced into one or more large thin reniform lobes.
Nineteen to forty pairs of gills.

For diagram illustrating this classification see woodcut on
p. 542.

16. Affinities of the Arenicolide.

On account of the very incomplete condition of knowledge
concerning the anatomy and development of allied families
(Maldanidz, Opheliide, Scalibregmidee, Chlorhemide) it is
impossible to speak with any confidence of the affinities of
Arenicola.’ In its external characters (with the exception
of the gills) this genus perhaps resembles the Maldanide
more closely than the other families. ‘The peculiarities
of the gills, however, cannot be overlooked. They form
the distinctive mark of the genus Arenicola, and it is
probable that they are special vascular processes rather than
modified dorsal cirri. The branched gills on the first few
segments of Scalibregma and Humenia are somewhat
similar to those of Arenicola in form, but different in
“arrangement, since they are present both above the noto-
podium and below it, and they are confined to the anterior
segments, on which they never occur in Arenicola. If then
the gills in two families have been independently acquired,
we have to look for other indications of affinity.

The general agreement in the subdivision of the ccelom
by septa, and the segmental blood-vessels in Arenicolide,
Scalibregmide, and Opheliide has been pointed out by
Wirén (1887). In these limnivorous families the coolom is
septate in its anterior and posterior regions, but in the
middle portion, apparently to allow the gastric loop room for

1 Tn this summary we purposely exclude Branchiomaldane, since its

anatomy is not sufficiently investigated. We have discussed its position on
p. 536,

544, F. W. GAMBLE AND J. H. ASHWORTH.

peristaltic movement, the septa have been reduced to the
narrow strip of connective tissue binding the segmental
vessels together. The three strong anterior “diaphragms,”
the loss of septa in the gastric region, and their reappear-
ance in the tail are important features which Arenicolide,
Scalibregmidz, and Opheliidee have in common. ‘The ne-
phridia of the three families agree in general form. In the
Scalibregmide they have never, of recent years, been care-
fully examined, so that Danielssen’s little-known account
of them may be worth quoting (‘ Anatomisk-physiologisk
Underségelse af Scalibregma inflatum,’ 1859, p. 69) :
‘Along the inner side of the body-cavity, from the sixth
segment up to the anus, there is a row of obliquely placed
loop-like bodies. The external upper and smaller end is
placed on the inner side of a swelling near the ventral
parapodium, while the rounded inner or lower end hangs
free in the body-cavity at the sides of the ventral vessel.
From the sixth to the thirteenth segments, at the sides of
each segment, these looped bodies are placed so close together
that the more anterior ones seem to have grown together.
These six are the largest (four lines long). In the following
sixteen segments they become smaller as one goes back.
Altogether there are forty to forty-two on each side. Hach
is composed of a fine sac-like membrane, ciliated internally.
They are crammed with large, round, clear cells and yellow-
green ‘ molecules,’ which lie in a clear fluid. I found no
ducts to these organs, nor did I see developed eggs in them,
though the body-cavity fluid was full of eggs. Yet I believe
they were the ovaries.” Further on Danielssen gives an
account of the testes which are present in addition to the
ovaries in these Scalibregma. In captivity the eggs are
discharged by rupture of the body-wall.

This, we believe, is the only account of the nephridia of
this genus. For it is pretty certain that the sac-like bodies
which Danielssen thought were ovaries are the nephridia,
which, as he says, are ciliated internally, and therefore
presumably have a distinct nephrostome, while the yellow-

ANATOMY AND CLASSIFICATION OF THE ARENICOLIDA. 545

green molecules are either excretory products of the walls of
the nephridia or else chlorogogenous cells which have been
swept into the nephridia. Further, the description and
plates show that the gonads are developed in connection with
the funnels.

From the rest of this interesting account of Scalibregma
it appears that there is a single dorsal “ heart’ which drives
the blood forward to the gills like a erebellid, and unlike
Arenicola. There are two esophageal pouches. But more
distinctive than even these is the definitely ganglionated
ventral nerve-cord. ‘These characters, taken in connection
with the far more complex parapodia which form swimming
plates, the absence of crotchets, and the arrangement of the
gills, seem to show that the Scalibregmide have a resem-
blance to the Arenicolide merely in the general arrange-
ment of the ccelom, in the digestive system, in the form of
the nephridia, and structure of gonads; but that in all other
respects—in external features, in the vascular and nervous
systems—the two families are widely different. In fact, it
seems more likely that the Scalibregmide are aberrant 'T'ere-
bellids.

The accounts of the vascular, nephridial, and reproductive
systems of the Ophelidz are so fragmentary as to preclude
any general comparisons with these organs in Arenicola.
Rathke’s (1843) excellent descriptions of their anatomy are
still the only accounts of the genera Ammotrypane and
Ophelia that can be considered at all complete, but naturally
some of his statements, e. g. that besides the opening of the
nephridium there are in Ammotrypane cestroides (now
called Ophelia acuminata) ovipores and openings into the
coelom, require corroboration ; which, however, has not been
attempted. ‘Thirteen pairs of nephridiopores are described
in this species, six in Ophelia limacina, and the drawing
of a nephridium of the former might stand for that of
Arenicola. The large funnel, the nephrostomial vessel, the
oblique muscles, are all exactly given in Rathke’s figure of
Ophelia, as they le in a specimen of a lugworm., Further

546 F. W. GAMBLE AND J. H. ASHWORTH.

agreement is indicated in Cosmovici’s work (1880), in which
he describes a gonad attached to the nephrostome, but in
such aconfused way as to render his conclusions of little value.
From the little we know, however, there seems to be a close
resemblance between the Opheliidee and the Arenicolide in
reference to the nephridial and reproductive systems. In
addition to this, the digestive system and the segmentation of
the ccelom are also fundamentally similar in the two cases.
Here again, however, as in the Scalibregmide, the external
features, the vascular system, especially the heart, the gan-
elionation of the nerve-cord, and, to judge from Kukenthal’s
account (1887), the brain, are very different from those of
the Arenicolide.

With the Maldanide the case is somewhat better. But
even in comparing this family with the Arenicolide the
differences are more obvious than the resemblances: for
though the absence of conspicuous cirri, the general form of
the parapodia, the reduction of the prostomium and ciliated
grooves, the small number of nephridia and gonads, the
simple subepidermal brain, the ventral cord with giant-cells
and a continuous covering of ganglion cells,—all agree fairly
closely with the corresponding structures of Arenicola, yet
the habits, the external features, and particularly the absence
of gills, of otocysts, and of hearts, separate the two families
very decidedly. The case of Branchiomaldane discussed
above makes it, however, clear that, apart from the seg-
mentation of the ccelom and the vascular system, of which
practically nothing is known in Maldanids, there is a closer
resemblance between this family and the Arenicolide than
exists between the lugworms and any third group.!

Benham (1893, p. 49) has suggested “that the closely
investing gelatinous tube (of the post-larva of Arenicola
marina) seems, when taken in connection with sundry
internal arrangements, such as nephridia, septa, etc., to point
to an affinity with the Chlorhemide.” The nephridia and

1 Mesnil (1898) has suggested an approximation of the Arenicolide and
Maldanide on the ground of the similarities of the sete.

ANATOMY AND CLASSIFICATION OF THE ARENICOLIDA. 547

septa of this family, so far as is known,! are, however, widely
different from those of Arenicola. In fact, until knowledge
of Chlorhemid anatomy and development is in a more
advanced condition, any conclusion as to the affinities of this
family must appear premature.

Mfc Summary of Results.

I. In this paper we show that there are three British
species of Arenicola—A. marina, A. ecaudata, and A.
Grubii. The last has not hitherto been recognised as a
member of the British fauna. It has, no doubt, often been
mistaken for A. ecaudata. From the Pacific coast of
America we record A. Claparedii, hitherto only known from
the Mediterranean.

II. The anatomy of A. Claparedii and A. cristata is
fully described for the first time.

III. The genus Arenicola may be divided into two
sections, according to the characters of the prostomium, the
arrangement of the gills and sete, the form of the ventral
lip of the nephrostome, and other features. To the first
section belong the common lugworm (A. marina), A. Cla-
paredii, and A. cristata, in which the prostomium is
well developed, the gills and sete are not continued to the
end of the body (i.e. there is an achetous and abranchiate
“tail”’), and the ventral lip of the nephrostome is entire.
The second section includes A. ecaudata and A. Grubii, in
which the prostomium is reduced, the gills and sete are
continued to the posterior end of the body, and the ventral
lip of the nephrostome is deeply notched at its centre.

IV. The external features usually relied upon by cheto-
podists to distinguish these five species from each other are
hable to such great variation in different specimens and in
the life-history of the individual as to render them (taken
alone) insufficient for accurate diagnosis. The characters of
the otocysts, prostomium, and nephridia taken together
afford a far more reliable basis for specific determination.

1 See Bles (1892).
VoL. 43, PARY 3.—NEW SERIES, PP

548 F. W. GAMBLE AND J. H. ASHWORTH.

V. We have adduced additional evidence in favour of
Benham’s statement that the achztous region between the
prostomium and the first chetigerous segment is formed by
the fusion of two segments. ‘The evidence consists (1) in the
presence in this achetous region of one of the segmentally
arranged “ giant-cells” in the nerve-cord, immediately behind
the point of union of the cesophageal connectives; this cell
belonging to the second segment, in which Benham found a
vestigial seta; (2) in the distinctness of these two segments
in the post-larva of A. ecaudata. Consequently the first
chetigerous annulus of the adult belongs to the third segment
of the body.

VI. The neuropodial crotchets undergo considerable
changes in form during the life of a worm. The rostrum, which
in cheetee from young specimens is at right angles to the shaft,
in later formed chete makes a considerably greater angle,
the angle increasing with the age of the worm. Concurrently
there is areduction in the size of the teeth of the chete, and
finally they disappear. We have confirmed the observation
of Mesnil that a crotchet, identical in form with those of the
neuropodium, occurs in the notopodium of each of the last six
setigerous segments of the post-larva of A. ecaudata. The
crotchet is soon lost from the notopodium, and henceforward
only capillary sete are found there.

VII. The heart-body, though absent in A. cristata and
A. Claparedii, occurs in A. marina, A. ecaudata, and A.
Grubii. It is absent in young specimens, and does not
develop until the animal is two or three inches in length. In
later stages it arises as finger-like ingrowths formed by
proliferation of the cells of the wall of the ventricular part
of the heart which connects the gastric vessel or sinus on
each side of the stomach with the ventral vessel. These
proliferations are very soon followed by invaginations which
carry the endothelium, the muscles, and the peritoneal lining
of the cardiac wall inwards. From the inner ends of these
short invaginations further proliferation takes place, so that
ultimately the cavity of the heart is reduced to a series of

ANATOMY AND CLASSIFICATION OF THE ARENICOLIDA. 549

narrow spaces filled with blood. The histology of the cardiac
body closely resembles that of the same organ in the dorsal
vessel of 'l'erebellids, as described by Picton. Hach invagi-
nation has an outer endothelium, a muscular middle coat, and
an irregular central cavity in which the peritoneal chlorogo-
genous tissue forms an irregular network of granular, glan-
dular, and often vacuolated cells, sometimes exhibiting a more
regular arrangement approaching an epithelium. These
peritoneal cells are the essential part of the heart-body, and
the function of the latter may be considered to be at least
twofold, excretory and valvular. On the one hand it removes
waste matters from the blood of the heart, on the other it
serves to prevent the regurgitation of blood into the gastric
vessels during systole.

VIII. With the exception of A. Claparedii all the species
of Arenicola possess longitudinal giant-fibres and seg-
mentally arranged ‘‘giant-cells” in the nerve-cord. The
giant-cells have been specially examined in A. Grubii. They
exhibit a complicated structure, and are enclosed in a sheath
of neuroglial fibrille which penetrate into them for a short
distance. The protoplasm is histologically identical with that
of ganglion-cells, and in particular contains structures which
we believe are identical with Apdthy’s neuro-fibrille. The
giant-cells are unipolar, and the process is free from chromo-
philous granules. This process we regard as an axon. It
contains the same kind of neuro-fibrille which are found in
the body of the cell, but they are stouter. Inthe case of each
of the anterior and posterior three or four giant-cells the
process enters a median giant-fibre. In the case of several
of the intermediate giant-cells the process enters one or both
lateral giant-fibres. In either case, however, before doing so
it gives off branches to the fibrous matter of the cord. ‘The
giant-fibres have the following structure :—a central, partly
fibrillar, partly homogeneous substance, enclosed in a myelin
sheath, and this again in a neuroglial one. There is free
anastomosis between the median and lateral fibres, and
between the two latter inter se. Branches from the lateral,

550 F. W. GAMBLE AND J. H. ASHWORTH.

and apparently (at least opposite the cheetigerous annuli) from
the median fibres, enter the spinal nerves.

As far as histology can go, the cells and fibres certainly
seem to be truly nervous, while their arrangement strongly
suggests that they are motor elements. Apdathy’s contention
that (on histological grounds alone) giant-fibres are sensory
appears in the present state of knowledge to be only partially
true.

IX. The brain exhibits two types of structure, not, however,
widely different. ‘The first is seen in A. marina, A. Clapa-
redii, and somewhat less distinctly in A. cristata. In
these forms there are three regions: an anterior pair of cere-
bral lobes, specially connected with the anterior sensory
prostomial epithelium, and through nerves with the buccal
papilla and buccal mass; a posterior pair of histologically
different lobes continuous with the epithelium of the nuchal
organ; lastly, a region intermediate both topographically
and histologically, supplying the upper surface of the pro-
stomium. In addition to these centres, the anterior lobes
contain near the median line a pair of groups of large pyri-
form cells, from which fibres pass to the circumcesophageal
connectives. The ganglion-cells for the most part form a
dorsal covering to the brain. ‘I'he more ventral fibrous region
is composed of cell-processes and their branches, which form
a delicate neuropile. This arrangement becomes more com-
plicated as the animal gets older, and there is an actual
increase in the size as well as in the complexity of the brain
apparently throughout life.

In the second section, which includes A. Grubiiand A.
ecaudata, the brain is a transverse band of nervous tissue.
Its upper surface is early in life produced upwards into short
irregular lobes, and from its outer angles the connectives are
given off. It appears to correspond to the united anterior
verebral lobes of the other section of the genus. Occasion-
ally a short median process extends backwards so as to
underlie the nuchal organ, but this sensory structure is also
supplied by several nerves from the commissural brain.

ANATOMY AND CLASSIFICATION OF THE ARENICOLIDA, 551

X. All species of Arenicola possess eyes, at least during
their immature stages of growth. Although these organs
have been previously discovered by Mesnil and Fauvel in
post-larval A. marina and A. ecaudata (in which they per-
sist), their presence in A. Claparedii, A. cristata, and A.
Grubii is here noted for the first time. The eyes arise in
the skin of the larva, and gradually assume a deeper position,
until in the adult they are found among the ganglionic cells
of the brain. They consist of a clear lenticular body par-
tially surrounded by a cup-shaped mass of brown or red
spherical pigment granules, which apparently are embedded
in a single cell. At their earliest appearance they correspond
in position to, while throughout life they retain the structure
of, the larval eyes of Nereis. Still more closely do they
resemble the simple eyes of the Capitellid Mastobranchus.

XI. The minute structure of the otocystic epithelium of A.
cristata resembles that of the other species, but there is a
more marked distinction between the supporting and sensory
elements. In A. Claparedii we have not found any trace of
the otocyst. The structure and microchemical reactions of
the otoliths of A. Grubiiare precisely similar to those of A.
ecaudata, and point to the conclusion that in both cases
these bodies are of chitinoid nature.

XII. There are no traces in the post-larva (i. e. the stages
of growth after the full number of segments has been
attained, but in which the gills have not yet assumed their
adult number and arrangement) of nephridia other than
those found in the adult. Nor is there a suppression in the
number of these organs in the life history of theanimal. But
there is one noticeable histological alteration in connection
with sexual maturity. Nephrostomes are absent from the
nephridia of our post-larval specimens of A. marina 4°5 mm.
long, as they were from Benham’s specimen 6'8 mm. long.
They are present in later stages, and in post-larve of A.
ecaudata 8 mm. and 9'4 mm. in length. It is probable that
the nephrostomes develop independently, and afterwards fuse
with that portion of the nephridium already present m the

552 F, W. GAMBLE AND J. H. ASHWORTH.

post-larva. Further evidence in favour of this independence
between the two parts of the nephridium is afforded by (1)
the occasional presence of a funnel alone, representing the
first and last pairs of nephridia of A. marina and the first
pair of A. Grubii; (2) the presence of a funnel only on one
side behind the last normal nephridium in A. Grubii; (3)
the presence of secretory and terminal portions only, as a
variation in A. marina.

XIII. All the species of Arenicola are of separate sexes. In
all, the gonads arise exclusively in close connection with the
nephridia. They are formed by proliferation of the peri-
toneal covering of a nephrostomial vessel, which we call the
gonidial vessel. In the structure of the gonad A. ecaudata
is widely removed from the other species, and is almost
unique among Polycheta. In this species there are two
deeply staining strands of cells, one on each side of each
nephrostome. Only one of these strands, the larger one
nearer the middle line of the body of the animal, is fertile.
These strands occur also on the first pair of nephrostomes,
but in this position they never give rise to reproductive cells.
In the case of the remaining twelve pairs of fertile gonidial
strands, the peritoneal tissue, of which they are proliferations,
is continuous in front with the peritoneum of the neck of the
funnel, while further back it forms the covering of the
gonidial vessel which runs down the side of the secreting
portion of the nephridium. From this vessel outgrowths are
formed at intervals towards the middle line, each outgrowth
carrying with it peritoneal covering of the vessel. All the
outgrowths are connected at their bases by the original
gonidial vessel and its peritoneum. ‘The ovaries are formed
by further division and growth of the peritoneal cells of the
vessels. The cells of the ovary are of two kinds; (1) an
enveloping layer of flattened cells, and within this (2) the
different stages of the ova themselves. The ovary is well
supplied with blood by branches from the gonidial vessel and
by anastomosing vessels, which are formed later, and connect
adjacent branches,

ANATOMY AND CLASSIFICATION OF THE ARENICOLIDA. 553

The testis of A. ecaudata is a thin, flattened, and slightly
folded reniform plate, and its mode of origin is similar to the
ovary. The early stages of the spermatozoa are completed in
this organ. Rupture of the wall sets them free into the body-
cavity, but whether the ovary or the testis subsequently
undergoes changes by which a new formation of ova or sper-
matozoa is accomplished in the following year, or whether
periodic discharge takes place at shorter intervals, we have
notascertained. In any case the result of the development of
vascular ovaries and testesin A. ecaudatais, that this species
retains the gonads within the reproductive organs for a much
longer time than is the case with its allies, and discharges
them into the ccelom in a more fully developed condition.

In the other species of the genus the gonads are merely
proliferations of the peritoneum of the nephrostomial vessel.
They are absent from the first nephridia. Hach of the follow-
ing nephridia bears a single gonidial strand on its inner side.

In all species all the nephridia act at certain times as the
oviducts or sperm-ducts. In A.ecaudata a special diver-
ticulum of the vesicle often occurs, in which the ova or sperms
are stored for a short time before being expelled.

XIV. Branchiomaldane Vincenti resembles in its ex-
ternal characters a late post-larval stage of one of the ecau-
date Arenicolide. The internal anatomy differs in the
absence of otocysts; the origin of both ovaries and testes
in the same animal from the septa; the variable number of
nephridia (two to five pairs in segments 5—9). The resem-
blances lead us to include it in the family Arenicolide, but
in a distinct genus.

XV. Though the Arenicolide show a closer affinity to the
Maldanide than to any other family of Polycheetes, they form
a very well-defined group. ‘The points of resemblance to the
Maldanidz are limited to the parapodia, the prostomium,
the brain, nerve-cord (especially the structure and arrange-
ment of giant-cells in the cord), the nephridia, and gonads.
The differences, however, are quite as striking, e. g. the seden-
tary, strictly tubicolous habit of the Maldanidw, their simple

554

F. W. GAMBLE AND J. H. ASHWORTH.

segmentation, the absence of gills, of paired hearts, and
otocysts. From the Opheliidee, Scalibregmide, and Chlor-
hemide, the Arenicolidz are still more widely separated,

1834.

1838.

1843.

1851.

1856.
1856.
1859.

18638.

1864.

1865.

1865.

1868.

1880.

1881.

188].

1882.

18. LitreERATURE.

Avupourn and Mitne-Epwarps.—‘ Recherches pour servir a Phistoire
naturelle du littoral de la France,’ Paris, 1834.

Mitne-Epwarps, H.—‘ Ann. des Sciences naturelles,’ p. 193, series 2,
tome x, 1838.

Ratuke, H.— Beitrage zur Fauna Norvegens,” ‘ Nova Acta Academic
Nature Curiosorum,’ tome xii, Breslau, Bonn, 1843.

Gruspr.— Die Familien der Anneliden,” ‘ Archiv f. Naturgesch.,’ Jahrg.
xvi, p. 136, Berlin, 1851.

Grrarp, C.—‘ Proc. Boston Soc. Nat. Hist.,’ p. 88, tome v, 1856.

Stimpson, W.—‘ Proc. Boston Soc. Nat. Hist.,’ p. 114, tome v, 1856.

DANIELSSEN, D. C.—‘‘ Beretning om en zoologisk Reise i Sommeren,
1858, Anatomisk-physiologisk Undersdgelse af Scalibregma in-
flatum,” ‘ Kel. norske Videnskselsk Skrifter,’ Aar 19, Bd. iv, Heft 2,
p. 69, 1859.

CraparkpE, E.—‘ Beobachtungen iiber Anat. u. Entwickelungsgesch.
wirbelléser Thiere,’ p. 30, Leipzig, 1863.

Lurken, —.—‘ Vidensk. Meddel. fraden naturh. Foren. i Kjobenhavn’
in Aaret, 1864, p. 120 (1865).

Jounston, G.—‘ Catal. of the British Non-parasitical Worms in the
Collection of the British Museum,’ p. 229, London, 1865.

QuaTreracrs, M. A. pE.—‘ Histoire naturelle des Annelés,’ Paris,
1865.

CraparrpE, E.—‘ Annélides chétopodes du Golfe de Naples’ Genéve et
Basle, p. 296, 1868.

Cosmovicr, L&on-C.— Archiv. Zool. expér.,’ tome vill, p. 233, 1879-
80.

Czerniavsky, V.—‘ Bull. de la Soc. Imp. des Natur. de Moscou,’
vol. lvi, pp. 853—356, 1881.

Laxcernans, P.—‘ Nova Acta Academie Nature Curiosorum,’ Bd.
xlii, No. 3, p. 116, Halle, 1881.

Levinsen, G. M. R.—‘ Vidensk. Meddel. fra den naturh. Foren, i
Kjobenhavn,’ pp. 136-8, 1883.

ANATOMY AND CLASSIFICATION OF THE ARENICOLIDA. 555

1882,

1883.

1885.
1886.
1886.
1887.
1887.

1887.

1887.
1887.

1888.

1888.

1889.
1889.
1890.
1891.

1891.
1891.

1892.
1892,

1892.

1892.
1892.

1893.

1893.

SpenceL, J. W.—‘ Mitth. Zool. Stat. Neapel,’ p. 15, and Taf. iv,
fig. 54, Band iii, 1882.

Witson, E. B.—‘ Studies from Biol. Lab. Johns Hopkins Univ.,’
p. 278, vol. ii, 1883.

Pruvot, G.—‘ Archiv. Zool. expér.,’ ser. 2, tome iii, 1885.

Fritscn, G.—‘ Archiv f. mikr. Anat.,’ Band xxvii, p. 13, 1886.

Jaquet, M.—‘ Mitth. Zool. Stat. zu Neapel,’ p. 297, Band vi, 1886.

Cunnineuam, J. T.—‘ Quart. Journ. Micr. Sci.,’ vol. xxviil, p. 239, 1887.

Ersi¢é, H.—‘ Monographie der Capitelliden des Golfes von Neapel,’
Berlin, 1887.

KuKENTHAL, W.—‘ Jenaische Zeitschr. f. Naturw.,’ Band xx, p. 511,
1887.

Roupr, H.—‘ Zool. Beitrage’ (Schneider), p. 73, Band ii, Heft 1.

Wiren.—‘ Kel. Vetensk. Akad. Handler.,’ Band xxii, No. 1, Stock-
holm, 1887.

Cunnincuam, J. T., and Ramacr, G. A.—‘ Trans. Roy. Soc. Edin-
burgh,’ p. 648, vol. xxxiii, 1888.

Frrepianver, B.—‘ Zeitschr. f. wiss. Zoologie,’ Bd. xlvii, Heft 1,
1888.

FrippDLANDER, B.—‘ Mitth. Zool, Stat. Neapel,’ Bd. ix, Heft 2, 1889.

Horst, R.—‘ Notes from the Leyden Museum,’ vol. xi, Note x, 1889.

Ives, J.—‘ Proce. Acad. N.S. Philadelphia,’ Part 1, pp. 73-5, 1890.

Benuam, W. B.—‘ Quart. Journ. Micr. Science,’ vol. xxxii, p. 325,
1891.

Cutnot, L.—‘ Arch. Zool. expér.,’ series 2, vol. ix, 1891.

Rerzius, G.—‘ Biologische Untersuchungen,’ neue Folge, il, p. 12, and
pl. iv, fig. 4, Stockholm, 1891.

Anprews, EK. A.—‘ Journ. of Morphology,’ vol. vii, p. 169, 1892.

Buss, BE. J.—‘ Report of Sixty-first Meeting of the British Association,
held at Cardiff, 1891,’ pp. 372-6, London, 1892.

Cerrontaine, P.— Bull. Acad. Roy. Belgique,’ series 38, tome xxiu,
p. 742, 1892.

Euters, E.—‘ Zeitschr. f. wiss. Zoologie,’ vol. lili, supplement, 1892.

LennosseK, M. von.—‘ Archiv f. mikr. Anat.,’ Band xxxix, Heft 1,
pp. 102-36, 1892.

Benuam, W. B.—‘ Journ. Marine Biol. Association,’ new series, vol. iii,
No. 1, p. 48, 1893.

Lo Branco, S.—‘ Atti della Reale Accademia delle Scienze Fisiche e
Matematiche, serie seconda, vol. v, No, 11, p. 9, Napoli, 1893,

556

1894.

1894.

1894.
1895.

1895.

1896.

1896.

1896.

1896.

189%.

1897.
1897.

1897.
1897.

1897.

1898.

F. W. GAMBLE AND J. H. ASHWORTH.

Auten, E. J.—‘ Quart. Journ. Micr. Science,’ vol. xxxvi, part 4, p. 461,
1894.

FRIEDLANDER, B.—‘ Zeitschr. f. wiss. Zoologie,’ Band lviii, Heft 4,
p. 661, 1894.

ScuaEprt.— Jenaische Zeitschr.,’ Band xxviii, p. 247, 1894.

FRIEDLANDER, B.—‘ Zeitschr. f. wiss. Zoologie,’? Band |x, Heft 2,
p- 249, 1895.

Lennossex, M. von.—‘ Archiv f. mikr. Anat.,’? Band xlvi, Heft 2,
pp. 845-69, 1895.

Au.En, H. J.—‘ Quart. Journ. Mier. Science,’ vol. xxxix, part 1, p. 33,
1896.

Brnuam, W. B.— Archiannelida, Polycheta, and Myzostomaria’ in
Cambridge Natural History, vol. ii, London, 1896.

Kyte, H. M.—‘ Annals and Mag. Nat. Hist.,’ series 6, vol. xviii, p. 295,
1896.

Racovitza, E. G.—‘ Arch. Zool. expér.,’ series 3, tome 4, p. 133,
1896.

Avdtuy, §8.—‘ Mitth. Zool. Stat. Neapel,’ Band xii, Heft 4, p. 495,
1897.

Betue, A.—‘ Pfliiger’s Archiv,’ Band lxviii, 1897.

Fauvet, P.—‘ Bull. scientif. de France et de Belgique,’ tome xxx,
1897.

Lewis, M.—‘ Proc. Boston Soc. Nat. Hist.,’ vol. xxviii, No. 5, 1897.

Mesnit, F.—‘ Bull. scientif. de France et de Belgique,’ tome xxx,
p. 144, 1897.

Saint-JOSEPH, DE.—‘ Ann. des Sciences naturelles,’ eighth series,
tome v, 1897.

Brtue, A.—‘ Pfliiger’s Archiv,’ Bd. lxx, 1898.

1898 a. Berur, A.—‘ Biolog. Centralbl.,’ Bd. xviii, p. 843, 1898.

1898.

1898.

1898.

1898.
1898.

1899.

Game, F. W., and AsHwortu, J. H.—‘ Quart. Journ. Micr.
Science,’ vol. xli, part 1, p. 1, 1898.

Hamaker, J. I.—‘ Bull. Mus. Compar. Zool. at Harvard College,’ vol.
xxxii, No. 6, Cambridge, U.S.A., 1898.

Lewis, M.—‘ Proc. Amer. Acad. Arts and Sciences,’ vol. xxxiii, No. 14,
1898.

MesniL, F.—‘ Zoolog. Anzeiger,’ Band xxi, p. 630, 1898.

Picton, L. J.—‘ Quart. Journ. Micr. Science,’ new series, vol. xlii,
part 2, p. 263, 1898.

Aprdtuy, S.—‘ Proc. Fourth Internat. Congress of Zoology,’ held at
Cambridge, 1898, p. 125, London, 1899.

ANATOMY AND CLASSIFICATION OF THE ARENICOLIDE. 557

1899. Fauves, P.—‘ Bull. Soc. Linnéenne de Normandie,’ series 5, vol. ii,
fasc. 1, Caen, 1899.

1899 a. Fauvet, P.—‘ Proc. Fourth Internat. Congress of Zoology,’ held at
Cambridge, 1898, p. 229, London, 1899.

1899. Lo Branco, S.—‘ Mitth. Zool. Stat. Neapel,’ Band xiii, p. 484, 1899.

EXPLANATION OF PLATES 22—29,

Illustrating Messrs. F. W. Gamble and J. H. Ashworth’s
Memoir on “The Anatomy and Classification of the
Arenicolidze.”

List oF REFERENCE LETTERS.

A. Cr, Anterior cornu of brain. dz, Anus. dz. Fr. Fibrous portion of
anterior brain-lobes. Ant. Gang. Gauglionic portion of anterior brain-lobes.
Au. Auricle of the heart. 8/7. Bladder of nephridium. B. Pap. Buccal
papille. Br. Gills. Br. AZ Afferent branchial vessels. Br. Hf. Efferent
branchial vessels. BR. Brain. B. S. Blood-spaces in the heart. B. SA.
Sheath formed by buccal retractor muscles. B. V. Blood-vessel. Buce. M.
Buccal mass. Cell. Gang. Ganglion cells of nerve-cord. Cen/r. Centrosome-
like body of giant-cell. CA. Z. Chitinoid lining of otocyst. Cal. G. Chiloro-
gogenous granules. CA/. Tiss. Clhlorogogenous tissue. Cel. Celomie space.
Cel. Epith. Celomic epithelium. Cozz.-tiss. Connective-tissue strands. C. P.
Cirriform processes on the tail of A. cristata. C. Sp. Caudal septa. C. Str.
Strand of modified peritoneal cells on the first nephridium. D. Z. V. Dorsal
longitudinal vessel. Dph. Ph. Diaphragmatic pouches. Dphm2-* Dia-
phragms. xdth. Endothelium of heart-body. pith. Sec. Secreting cells of
the epidermis. FG. Yolk-granules. Fr. Fibrous part of the nerve-cord.
Gast. Lat. Lateral gastric vessel. Gast. V. Small gastric vessels. G. c.
Giant-cell. G. c. proc. Process of giant-cell. G. c. proc. fb. Branch of
process of giant-cell to fibrous part of nerve-cord. Gen. Str. Genital strand
or gonad. G. F, Giant-fibre. G. f. dat. Lateral giant-fibre. G. f. m.
Median giant-fibre. G. F. Sh. Neuroglial sheath of giant-fibre. G@. V.
Gonidial vessel. H¢. Heart. H¢. B. Heart-body. Jz¢. Intestine. Int. V.
Intestinal vessels. Met. Gr. Metastomial groove. Mid. Gang. Ganglion of
middle brain-lobe. Mo. Mouth. M. Pro. Protractor muscles of sete.
M. Ret. Retractors of sete. MN. Nucleus of giant-cell. NW. Af. Afferent
nephridial vessels. MN. C. Nerve-cord. WN. Hf. Hfferent nephridial vessels.
N. form. Nucleus of cell from which the eye is formed. Nrgl. Neuroglia.
Nol. fle. Neuroglial fibrille. Nl. Sh. Neuroglial sheath. MW//e. Neuro-

558 F, W. GAMBLE AND J. H. ASHWORTH.

fibrille. N/m. Neurilemma sheath. NW. Z. VY. Nephridial longitudinal
vessel. Nm. Neuropodium. Nm. Ch. Neuropodial crotchets. NW. V. Nuclei
of nerve-cells. WV. 0.!-% Nephridiopores. Notm. Notopodium. Wot. 8.
Notopodial sete. Mph. Nephridium, Nphm. Nephrostome. Nphm. D.
Dorsal lip of nephrostome. Nphm. V. Ventral lip of nephrostome. NV. SA.
Nerve-sheath. Nuc. Gr. Nuchal groove. Nuc. N. Nerve to nuchal groove.
N. N. Neural vessels. O. a/v. Outer alveolar layer of giant-cell. Oc. Eyes.
CG. Esophagus. Ci. Comm. Circumeesophageal nerve-connectives. Ci. Lat.
Lateral cesophageal vessel. O/. Otocyst. O¢h. Otoliths. Of. N. Nerve to
otocyst. Ov. Proc. Process of ovary. Par. V. Parietal vessels. Per. Peri-
stomium. Proc. Process of crotchet. Prost. Prostomium. Prost. Lpith.
Prostomial epithelium. Prost. Lat. Lateral process of prostomium. Prost.
Mid. Middle lobe of prostomium. Prost. Muse. Muscles of prostomium.
Prost. Sens. Sensory cells of prostomium. Rad. Br, Rudimentary gill on the
tail of A. cristata. Sez. C. Sensory cells. Sp. Septum. Sup. C. Support-
ing cells of the otocystic epithelium. VY. Ventricle of heart. VY. J/. Vitelline
membrane. V. Vph. Ventral lip of nephridium. V. V. Ventral vessel.

PLATE 22.

Frc. 1.—The large American specimen of A. cristata from the Harvard
Museum, seen from the left side to show the external features, sete, gills,
nephridiopores, and the segmentally arranged processes on the tail. There
are six nephridiopores on the left side and seven on the right side of this
specimen. The neuropodia of the first four segments are not visible exter-
nally. The cirriform processes of the tail are also shown on Pl. 24, Figs.
380—32. x 4.

Fic. 2.—Dorsal view of the anterior of a specimen of A. cristata, 300
mm. long, from Naples, to show the prostomium and nuchal organ and the
papillae of the buccal mass. x 4.

Fic. 3.—A large specimen of A.Grubii from Port St. Mary, Isle of Man,
seen from the left side to show the external features, setee, gills, and ne-
phridiopores (5 in number). x 12.

Fic, 4.—A large specimen of A. ecaudata from Port St. Mary, to- show
the external features, sete, gills, and nephridiopores (13 in number). xX 1.

Fie. 5.—Two views of the anterior end of A. Grubii from Port St. Mary,
showing the prostomium and nuchal organ.

Fie. 5 a.—From the dorsal surface. x 3.

Fic. 5 s.—From the left side. x 3.

The anterior end of A. ecaudata closely agrees with this.

Fic. 6.—Posterior end of a specimen of A. Grubii from Jersey, showing
the sete and developing gills. x 6.

ANATOMY AND CLASSIFICATION OF THE ARENICOLIDM. 559

Fie. 7.—The gill of A. ecaudata.

Fie. 7a.—The third left gill, to show the plan of branching from the
base. x 10.

Fic. 7 8.—The terminal branches of one of the gill plumes. x 10.
The gill of A. Grubii closely agrees with this.

PLATE 23.

Fig. 8.—A. marina. Neuropodial chet from the post-larval specimen
(3°9 mm. Jong) shown in Fig. 34. Note the rostrum (Rost.), the teeth (7),
and the process (Proc.). The last is more highly developed in, and very
characteristic of Maldanide. x 1000.

Fic. 9.—A. marina. The ventral portion of the neuropodium of a large
Laminarian specimen, showing the stages in development of the chete. The
line marked Wm. is the outline of the neuropodium. ‘The chete are devuid of
teeth, but show a small blunt process (Proe.). x 85.

Fic. 10.—A. marina. A neuropodial cheta from a littoral specimen
100 mm. long. In worms of this size the chaete bear two or three small
teeth, and a very minute blunt process. x 150.

Fie. 11.—A. marina. A neuropodial cheta from a small specimen
17 mm. long. The teeth are well marked. x 500.

On comparing the four preceding figures there is seen to be, following the
erowth of the worm, an increase in the size of the chete, a decrease in the
size of the teeth of the chete, and also a gradual change in the incli-
nation of the rostrum to the shaft, the angle increasing with the size of the
specimen,

Fie. 12.—A. marina. Notopodial sete from the post-larval specimen
(3°9 mm. long) shown in Fig. 34, Hach notopodium bears about two to five
ordinary capillary chete (Fig. 12 a), and one similar to those shown in
Fig. 12 3.

Fie. 12 a.—Capillary seta showing the barbs or processes upon its distal
portion. x 500.

Fic. 12 B.—Notopodial sete bearing a lamina along a portion of their
length. x 1000.

Fic. 18.—A. cristata.
Fie. 13 a.—Represents a notopodial seta from a specimen 47°5 mm. long
from Jamaica, to show the barbs or processes upon its distal portion. x 93

Fic. 13 8.—A portion of the same seta from the region marked +, more
highly magnified. x 1000.

Fie. 14.—A. cristata. The tip of a notopodial seta from the large

specimen shown in Fig, 80. Note the very numerous barbs or processes.
x 500.

560 F. W. GAMBLE AND J. H. ASHWORTH.

Fie. 15.—A. cristata. Two neuropodial chete from a specimen 47°5 mm.
long from Jamaica. x 500.
Fie. 16.—A. cristata. A neuropodial cheta from a specimen 120 mm.
long from Captiva Key. x 180.
Fie. 17.—A. cristata. A neuropodial cheta from a specimen 300 mm.
long from Napies. x 180.
Figs. 15, 16, 17, should be compared to show the change in the

inclination of the rostrum to the shaft of the cheeta, and the decrease in
size of the teeth with advancing age.

Fic. 18—A. ecaudata. The ventral portion of a neuropodium of a
specimen about 160 mm. long (from Port St. Mary, Isle of Man), showing the
stages in development of the chete. The line marked Nm. is the outline of
the neuropodium. The chete bear two or three teeth, but are devoid of pro-
cesses. xX 180.

Fie. 19.—A. ecaudata. Three neuropodial chete from a_post-larval
specimen 7°2 mm. long from Port Erin, Isle of Man. One of them bears a
small process under the rostrum. x 1000. Compare with Fig. 18.

Fic, 20.—A. ecaudata.

Fic. 20 a.—A notopodial seta from a specimen about 160 mm. long. Note
that the seta gradually tapers toa very long slender tip. Under this magnifi-
cation the minute barbs or processes are not visible. The seta is 3°02
mm. long. x 43.

Fie. 208.—The distal tenth of the same seta, showing the minute barbs.
x 350.

Fic. 20c.—A portion of the same seta from the region marked +, more
highly magnified. x 2000. The notopodial sete of A. Grubii are identical
with this.

Fie. 21.—A. ecaudata.

Figs. 21 a and 21 c represent two notopodial sete from a_post-larval
specimen 7°2 mm. long from Port Erin. x 366.

Fic. 21 8.—The distal portion of the seta shown in Fig. 21 4 more highly
magnified, to show the barbs and lamina. x 1000.

Fic. 22.—A. Grubii. ‘Three neuropodial chete from a medium-sized
specimen from Port St. Mary. The teeth are small, and each cheta bears a
minute blunt process (Proc.). These chet are practically identical with
those of A. ecaudata shown in Fig. 18. The minute process is not a constant
character of the cheete of either of these two species. x 180.

Fig. 23.—A. Claparedii.

Fie. 25a4.—The distal fourth of a notopodial seta of a specimen about
70 mm. to 80 mm. long from Naples, to show the numerous barbs or
processes. xX 350,

ANATOMY AND CLASSIFICATION OF THE ARENICOLIDA. 561

Fig. 238.—A portion of the same seta from the region marked +.
x 1000.

Fic. 24.—A. Claparedii. The ventral portion of a neuropodium of a
Neapolitan specimen 95 mm. long, showing the stages in the development of
the chete. x 180.

Fie. 25.—A. Claparedii. A neuropodial cheta from a Neapolitan
specimen 75 mm. long, to show the great curvature of the cheta. x 180.

PLATE 24.

Fic. 26.—Dissection of a specimen of Arenicola Claparedii from
Naples, to show the general characters of the internal anatomy. The special
features shown are the three anterior diaphragms, the caudal septa, the
alimentary canal and the cesophageal pouches, the vascular system, and the
nephridia. The vessels of the posterior portion of the alimentary canal are
more highly developed than usual in this specimen. The oblique muscles and
longitudinal muscle-bands are not shown. xX 2.

Fie. 27.—A portion of the esophagus of a specimen of A. Claparedil
from Naples, showing the multiple cesophageal pouches. x 4.

Fic. 28.—A portion of the cesophagus of a specimen of A. Claparedii
from Crescent City, California. In this specimen fifteen cesophageal pouches
are present. xX 3.

Fie. 29.—The fourth right nephridium of a Neapolitan specimen of A.
Claparedii, seen from the dorsal aspect, showing the dorsal lip of the
nephrostome (Vphm. D.) with its spatulate ciliated vascular processes, the
secreting portion of the nephridium (Vp4.), and the bladder (B/.). Note also
the blood-vessels, the gonad (Goz.) upon the gonidial vessel (G. V.), and the
bluntly ending filamentous branches of the gonidial vessel. x 16.

Fie. 30.—Dissection of the large specimen of Arenicola cristata from
the Harvard Museum, to show the general characters of the internal anatomy.
The special features shown are the three anterior diaphragms, the caudal septa,
the muscles, the alimentary canal, the vascular system,and nephridia. A
complete (seventh) nephridium is present on the right side in addition to the
normal six pairs. ‘The position of the first gill is clearly indicated by the
appearance on segment 7 (Wot. 8.7) of both afferent and efferent branchial
vessels (Br. Aff’, Br. Eff). The cirriform processes (C. P.) on the tail are
seen to be segmentally arranged. Natural size.

This figure is to be compared with the similar dissection of A. marina
(Gamble and Ashworth, 1898, Pl. 2).

Fre, 31.—The posterior branchial and anterior caudal region of the same
specimen of A, cristata, seen from the right side, to show the last fully
developed gill (Br.?, the branches of which are cut short), the presence of a
rudimentary gill (Awd. Br.) on the first caudal segment, and the cirriform pro-

562 F. W. GAMBLE AND J. H. ASHWORTH.

cesses (C. P.). The notopodial sete are in two rows, those in the anterior
row being about two thirds the length of those in the posterior row. X 2.

Fic. 32.—View of the same region from the left side. Note the cirriform
process just dorsal to the last neuropodium (Mm.). The other features are as
in the previous figure. xX 2.

Fre. 33.—The tenth branchiferous annulus of a specimen of A. cristata,
120 mm. long, from Captiva Key, seen from the left side, to show the small
greyish pit situated on a slight elevation just dorsal to the neuropodium.
There is a similar structure on each of the last seven chetigerous annuli of
this specimen. The anterior row of shorter sete and the posterior row of
larger sete are shown (slightly displaced) in the notopodium.

Fic. 34.—Post-larval specimen of A. marina, 3°9 mm. long, taken in the
tow-net by Mr. R. L. Ascroft at Lytham. The animal is seen from its left
side, and shows the eyes on the prostomium, the two kinds of notopodial sete
(see also Pl. 23, fig. 12), the gills, and the otocysts. From a preparation.
x 50.

Fig. 85.—Post-larval specimen of Arenicola ecaudata, 94 mm. long,
Port Erin, August, 1896. The figure is from the left side of the animal,
and shows the external characters and nephridiopores. There is a distinct
groove separating the peristomium ( Per.) from the following achetous segment.
The first cheetigerous segment is therefore (as is further explained in the text,
p. 441) the third segment of the body. x 22.

Fig. 36.—Another post-larva of A. ecaudata (8 mm. long), lightly stained
and then cleared in cedar-wood oil. The anterior half is viewed obliquely from
the left side and ventral surface, the posterior half is twisted upwards and
seen from the ventral surface. The alimentary canal is shaded, the nerve-cord
left white. The nephridia of the right side are clearly shown. Note also the
otocyst (O¢.) with its single otolith. x 24.

Fic. 37.—Posterior extremity of the same specimen, to show the presence
of crotchets in the last six notopodia in addition to the capillary sete. The
intestine (Zvé.) is drawn out into concertina-like folds by the septa (Sp.). »« 130.

PLATE 25.

|

Fic. 38.—Longitudinal section of the heart of a specimen of A. Grubii
140 mm. long from Port St. Mary. The wall of the heart is thin, and “s com-
posed of three layers,—an endothelium internally, a muscle layer, and/a peri-
toneal covering, the cells of which often contain chlorogogenous granules. The
muscle layer is only feebly developed in worms of this size, it becomes much
more highly developed in older specimens (see Fig. 39). On the posterior
(right) side the wall of the heart is being invaginated at several points, thus
giving rise to the heart-body. Each invagination involves the whole wall of

ANATOMY AND CLASSIFICATION OF THE ARENICOLIDA. 563

the heart. Sections of the invaginated processes show the central core of the
peritoneal cells surrounded by the muscle layer (the endothelium cannot be
shown on this scale of magnification). The space occupied by the blood is
coloured red. x 86.

Fie. 39.—Longitudinal section of the heart of a specimen of A. Grubil
225 mm. long from Port St. Mary. The wall of the heart is much thicker in
this older specimen, chiefly owing to the greater development of the muscle
layer. The invaginations of the wall are very numerous and complex, filling
up the greater part of the cavity of the heart, and forming the well-marked
heart body. Compare the blood space in this specimen with that of the
specimen drawn in Fig. 38. x 96.

Fic. 40.—Blood-corpuscles of A. Grubii. Many of these were found in
sections of the heart shown in Fig. 38, embedded in the mass of blood con-
tained in the cavity of the heart. x 1000.

Fig. 41.—A portion of the tip of one of the invaginated processes of the
heart-body of A. Grubii (from a specimen about 150 mm. long), to show
the endothelium (Hzdth.), the muscle layer (musc.), and the core of loosely
arranged peritoneal cells (Per. C.). The last are either vacuolated or

granular, owing to the presence of chlorogogenous granules in the protoplasm.
x 470.

Fie. 42.—A similar process from the heart-body of a full-grown specimen
of A. marina, showing the endothelium, the muscle-fibres, and the peritoneal
cells. x 240.

lie. 43.—Another process from the same specimen of A. marina. In this
and several other processes there is a large collection of chlorogogenous granules
in many of the cells. These are shown in the figure in red, but they are naturally
of a yellow colour. In many of the cells the granules are aggregated into
small heaps, sometimes lying in a vacuole. The ceil-outlines of the cells
which are loaded with chlorogogenous granules are diflicult to distinguish.
The protoplasm of many of the other peritoneal cells is granular, but the
granules are very small and of a different nature from the chlorogogen
granules. x 600.

Fic. 44.— Dissection of a specimen of A. Grubii from Port St. Mary, to
show the general characters of the internal anatomy. The special features
shown are the three anterior diaphragms, the buccal musculature, the septa
present in the posterior portion of the animal, the alimentary canal, the
vascular system, and the nephridia. The vessel which passes from the dorsal
vessel to the first nephridium is shown on the right side, but omitted on the
left side. The second nephridium derives its blood-supply from the dorsal
longitudinal vessel (D. Z. V.). The oblique muscles which are present in the
septate region of the body are very narrow bands about + mm. in diameter,
and cannot be shown in the drawing. Note the two strands of connective tissue
(Conn. Tiss.) attached to the alimentary canal and to the body-wall at the level

VOL, 43, PART 3,—NEW SERIES. QQ

564 Kk. W. GAMBLE AND J. H. ASHWORTH.

of the heart. The position of the first gill is indicated internally by the
afferent and efferent branchial vessels (Br. 4f' and Br. Hf). xX 14.

Fie. 45.—Dissection of a medium-sized female specimen of A. ecaudata
from Port St. Mary (April, 1897), to show the general characters of the
internal anatomy. Note the three anterior diaphragms, the buccal muscula-
ture, the septa in the posterior portion of the animal, the oblique muscles, the
alimentary canal, the vascular system, the nephridia, and the ovarian processes.
The second nephridium is supplied with blood by a small vessel from the
dorsal longitudinal vessel (D. Z.V.). The position of the first gill is shown
internally by the afferent and efferent branchial vessels (Br. Af’, Br. Eff).
The first two efferent branchial vessels are accompanied by a thin band of
connective tissue, the representative of the septum of the following segments.
The septa and oblique muscles are present to the posterior end. The first
nephridium does not bear gonads. The ovarian processes attain a larger size
in larger specimens. The last twenty-seven segments of the worm are omitted,
<2:

PLATE 26.

Fie. 46.—One of the nephridia of the right side of a medium-sized female
specimen of A. ecaudata (Port St. Mary, Isle of Man, April, 1897) seen
from the ventral aspect. The nephrostome (red) is formed of two lips, a
deeply notched ventral one (Wphm. V.) and a dorsal one (Vphm. D.), bearing
numerous digitiform ciliated vascular processes. The network of blood-
vessels upon the nephrostome is somewhat closer than shown in the figure.
Note the blood-vessels with blind dilated ends on the ventral lip. The
secreting portion of the nephridium and the vesicular bladder are covered by
a network of blood-vessels. ‘he genital strand arises on the inner side of the
funnel, and runs parallel to, and applied to, the secreting portion of the
nephridium. It is pierced axially by the gonidial vessel (@. V.). On the
outer side of the ventral lip of the nephrostome there is a deeply staining
strand of cells (S¢ér.), which probably gives rise to ceelomie corpuscles. The
long finger-shaped outgrowths from the genital strand contain ova in all
stages of development. ach is supplied by one or more vessels—branches
of the gonidial vessel (see Figs. 51, 52). The processes are considerably
larger in mature specimens than in the specimen drawn. X 22.

Fie. 47.—Sixth right nephridium of a large female specimen of A. ecau-
data (from Port St. Mary, April, 1897), seen from the ventral aspect. The
ova, having been discharged from the ovarian processes into the ccelom, have
been taken up by the nephrostome and passed into the bladder of the
nephridium, causing the thin-walled sac-like diverticulum shown in the figure.
This sac is full of large ova. There were similar vesicles attached to the
bladders of the fifth and sixth nephridia of the left side. x 8.

Fic. 48.—A nephridium from the right side of a male specimen of A.
ecaudata (Port St, Mary, April, 1897), seen from the ventral aspect,

ANATOMY AND CLASSIFICATION OF THE ARENICOLIDA. 565

Note the deeply notched ventral lip of the nephrostome, some of the blood-
vessels of which have blind dilated endings; the dorsal lip fringed with
ciliated vascular processes ; and the secreting portion of the nephridium and
the bladder with this network of blood-vessels. The genital strand commences
on the inner side of the ventral lip of the nephrostome, and runs parallel to
and close to the secreting portion of the nephridium. Note also the sterile
strand of deeply staining cells on the ventral lip. The gonidial vessel (G. V.)
runs axially through the genital strand. The large, flat, reniform lobe of the
testes is attached to the genital strand by a mesentery, through which pass
branches of the gonidial vessel covered by genital cells (B. V. and Gen. C.).
x 22.

Fie. 49.—Section of the wall of the secreting portion of the nephridium of
a medium-sized specimen of A. ecaudata. The wall is formed by (1) columnar
secreting cells, the inner or free ends of which abut on the cavity of the
nephridium; (2) a small amount of almost homogeneous supporting tissue
situated at the bases of the secreting cells ; the nuclei of this tissue are shown;
(3) a thin layer of ccelomic epithelium (Ce/. Epith.), immediately within which
are the blood-vessels (B. V.). The inner or free ends of the secreting cells
are very clear and free from granules. In many examples this clear portion
is much larger than in the specimen drawn. The outlines of the secreting
cells may be seen near their free ends, but they are not distinguishable towards
the bases of the cells. The excretory granules present in the cells are of two
kinds: (1) those nearer the free ends of the cells, which stain black with hema-
toxylin ; and (2) those nearer the basal portions of the cells, which are yellow,
and do not stain with hematoxylin. The latter are often aggregated into
heaps. They are drawn in red in the figure, but their natural colour is yellow.
x 570.

Fie. 50.—A portion of the post-larval specimen of A. ecaudata shown in
Pl. 24, fig. 35. The specimen was embedded in paraffin wax, and cut trans-
versely to the middle of the first nephridium. The remainder of the specimen
was cut longitudinally (sagittally) until the middle line, as indicated by the
nerve-cord, was reached. The portion then remaining was removed from
paraffin by immersion in warm xylol, and the half of the alimentary canal
remaining in the body of the worm dissected out. The body-wall and nephridia
attached to it were then mounted in cedar-wood oil. The preparation as it
now appears is shown in the figure. The left-hand side of the figure is dorsal,
the right-hand side ventral, A portion of the first nephridium was cut away
in the trausverse sections. The other twelve nephridia are shown. On the
nephrostome of the second nephridium there is a small heap of cells—the com-
mencement of one of the ciliated processes of the dorsal lip. The edges of
the nephrostome are thick, being formed of large columnar or cubical celis.
The nephrostomes of the ninth and tenth nephridia are connected to the
secreting portion by narrow tubes ‘006 mm, and ‘01 mm. long respectively,

566 F. W. GAMBLE AND J. H. ASHWORTH.

The nephrostomes of the three posterior nephridia are much smaller than
those of the anterior nephridia. x 70.

Fic. 51.—Longitudinal section of the proximal part of one of the ovarian
processes of A.ecaudata. On the left a portion of the gonidial vessel is
seen, a branch of which traverses the axis of the process. The wall of the
blood-vessel, which is formed of a very thin layer of cells well seen on the left,
is covered by a layer of cells produced by divisions of the ecelomic epithelium.
From these the ova are differentiated near the vessel, and recede from it as
they increase in size. The ova are covered by a layer of unaltered coelomic
epithelium. The nuclei of the ova gradually increase in size and become
vesicular (germinal vesicle, Germ. V.). The germinal vesicle contains a small
amount of chromatin in the form of a network, and usually a well-marked
nucleolus (Nzel.). Yolk granules are deposited in the protoplasm, but the
peripheral layer of protoplasm in a ripe ovum is almost free from granules
(see the large ovum near the middle of the figure). The ripe ova have a thick
conspicuous vitelline membrane. xX 420.

Fie. 52.—One of the ovarian processes of a medium-sized female specimen
of A. ecaudata, showing the blood-vessels. At first the process contains only
one axial blood-vessel (as in the preceding figure), but later more vessels
penetrate into the process and become connected as shown. X 12.

Fie. 53.—A portion of a dissection of A. Grubii from Plymouth (Jan.,
1899). The second and third nephridia of the right side with their gonads
(Gen. Str.) and the surrounding structures are shown. The dorsal lips
(Nphm. D.) only of the nephrostomes are visible. The second nephridium
receives blood from the dorsal longitudinal vessel (D. Z. V.). The afferent
vessel of the third nephridium is a branch of the ventral vessel. It is accom-
panied by a thin band of connective tissue, which spreads out fan-wise and
connects the nephridium to the body-wall in the region of the second groove
dehind the chetigerous annulus, i. e. at the boundary of the segment. This is
therefore the representative of the septum of the segment. Xx 4.

Fre. 54.—A portion of a dissection of A. Grubii from Naples, showing
the last (fifth) nephridium of the right side with a rudimentary nephrostome
(Rud. Nphm.) on the septum in the following segment. The dorsal lip of the

ephrostome, the gonad, blood-vessels, sete, muscles, and rudimentary septa
are also shown. x 8,

(Fig. 55 is omitted.)

PLATE 27.

Fic. 56.—The anterior end of Arenicola Claparedii seen from above,
with the top of the prostomium sliced off horizontally. The ganglionic por-
tion of the brain is dotted, the fibrous matter tinted. The course of the
nuchal groove is clearly shown, The point marked z, z is the enlarged

=

ANATOMY AND CLASSIFICATION OF THE ARENICOLIDA. 567

anterior end of the metastomial groove. The circumcsophageal nerve-
connectives and their point of union are shown by dotted lines. The four
coelomic spaces are portions of a continuous anterior extension of the ccelom.
The figure has been constructed from sections cut in three planes. X 100.

Fic. 57.—A slightly oblique section across the middle of the brain of A.
Claparedii (26 mm. long), to show the great development of neuropile
(Npile.), the neuroglial cells (Wrg/.), and the sensory elements of the prostomial
epithelium (Prost. Hpith.). In the brain the ganglion cells of the middle
cerebral lobes (Mid. gang.) form two lateral masses separated by a median
ccelomic space. Cam. luc. x 110.

Fie. 58.—Transverse section across the prostomium of the same specimen
A. Claparedii, cutting the extreme ends of the anterior cerebral lobes. The
neuropile is dotted. Cam. luc. x 110.

Fic. 59.—Anterior end of an adult specimen of A. Claparedii from
Crescent City, California, seen from above to show the form of the prostomium.
x6. Gla

Fic. 60.—The same seen from the side.

Fic, 61.—Anterior end of a young specimen (15 mm. long) of A.
Claparedii from Naples, seen from above to show the highly developed
prostomium. x 18.

Fig. 62.—The same from the side. x 20.

Fic. 63.—Horizontal section of the brain and prostomium of A. marina,
from a specimen 60 mm. long. ‘The neuropile is dotted. The commissure
(Mid. Comm.) which binds the anterior lobes together is cut horizontally.
The arrangement of the large pyriform ganglionic cells (Aué. gang.) round the
coelomic spaces is very evident. ‘The nuchal groove (Nuc. Gr.) is cut across
obliquely. x 75.

Fie. 63 a.—Part of a transverse section of the prostomium of Arenicola
ecaudata, to show the eyes embedded in the nervous tissue underlying the
epidermis. The latter is composed at this point of mucus-forming cells
(Zpith. sec.), broader at their outer ends than at their inner ones. The rest of
the thickness of the section is made up of a nervous tissue composed of cells
(the nuclei of which are seen at 2. 2.) and wavy fibres. The lens-like body
and the pigment granules of the eyes are wellseen. x. form refers to a
nucleated mass which is probably the cell in which the eye has been formed.
x 440.

Fic. 64.—Section across the otocyst of a full-grown specimen of A.
ecaudata. The outer layer is composed of connective tissue supporting a
nerve-sheath (JV. SA.) which results from the branches of the otocyst nerve
(Ot. N.). The sensory epithelium contains supporting cells, which, however,
are not distinguishable in this figure. In the centre of the organ are the
chitinoid otoliths, which have been drawn from a whole preparation of the

568 F. W. GAMBLE AND J. H. ASHWORTH.

otocyst. The otocyst of A. Grubii agrees in all essentials with this one.
x 200.

Fic. 65.—Section across the otocyst of a specimen of A. cristata from
Naples (300 mm. long). The distinction between the sensory and supporting
elements (Sevs. C. and Sup. C.) is clearly shown. Note the single large
chitinoid otolith. x 140.

Fie. 66.—Horizontal section of a giant-fibre of A. Grubii, to show the
outer sheath of neurilemna (WV//m.), the true neuroglial sheath (gf sh.), and
an inner myelin sheath (Jy. Sh.) which is dissolved out in the specimen figured.
The contents of the fibre consist of very delicate fibrille in a faintly staining
protoplasm. x 500.

PLATE 28.

All the drawings of this plate are taken from a specimen of Arenicola
Grubii 78 mm. long.

Fies. 67—70.—These are four camera drawings of consecutive sections
through a giant-cell, its process, and the point of union of this process with a
lateral giant-fibre. In Fig. 70 the structure of the process and cell are well
shown, particularly the neuro-fibrille (W//z.). In the giant-cell the neuro-
glial network and outer alveolar layer should be compared with the enlarged
figures, 76 and 77. The branch of the cell-process to the fibrous part of the
cord is seen in Fig. 69 (G. c. proc. fb.).

Corrosive acetic, iron-hematoxylin. Outline of the figure drawn with oe. 6,
obj. D of the Zeiss system, and the detail under Zeiss oil-immersion apochro-
matic objective with an aperture of ‘02 mm. x 350.

Fics. 71—73.—Three consecutive sections to show the connection between
the giant-cell and the median giant-fibre in segment 5. The alveolar structure
of the cell protoplasm and the ueuro-fibrille of the cell process (Wi/e.) are
distinct. x 350.

Fic. 74.—Trausverse section of the cord in segment 8 to show the fusion of
the two lateral with the mediau giant-fibre and the branch from this union to
the spinal nerve on each side. On the left side the branch is prolonged in
the section to the base of the spinal nerve. x 350.

Fie. 75.—Longitudinal section of the nerve-cord just behind the sixteenth
neuropodium. Two giant-cells are seen surrounded by ordinary ganglion
cells. Each giant-cell has a neuroglial sheath (V/. Sh.), and the process of
each to the cord is cut off transversely (G. ¢. proc.). The neuroglial fibrille
are chiefly confined to the median line. The network in the giant-cell is
neuroglial in nature. X 380.

Fics. 76 and 77.—Consecutive sections of the body of a giant-cell of the
same specimen of A. Grubii, to show the minute structure. The outer

ANATOMY AND CLASSIFICATION OF THE ARENICOLIDE. 569

alveolar zone and its neuroglial envelope are seen. A few neuro-fibrillee are
shown at We. enclosed in a dense glia-sheath.
Corrosive-acetic, Apathy’s hamatein 1 A. x 500.

PLATE 29.

Fic. 78.—A portion of the nerve-cord of a young specimen of A. Grubii,
78 mm. long, to show the giant-cells and spinal nerves in relation to the
annuli. The cut ends of the neuropodial chete of the fourteenth and
fifteenth chetigerous segments are shown. Reconstructed from horizontal
sections. X 25.

Fie. 79.—Plan of the entire nerve-cord of a young specimen of A. Grubii
78 mm. long, to show the position of the giant-cells. The transverse lines
mark the level of the neuropodia, the numbers of which are given at the sides.
The length of the cord in the drawing is twenty times its actual length., The
breadth of the cord and the size of the nerve-cells are fifty times the actual.
Reconstructed from about 5000 sections.

Fic. 80.—A portion of the nerve-cord of a specimen of A. marina 17°5
mm. long, to show the giant-cells. The section extends from the eighth to
the nineteenth chetigerous annuli. Reconstructed from sagittal sections.
x 20.

Fic. 81.—A portion of the nerve-cord of a specimen of A. cristata to show
two of the segmentally enlarged giant-cells. x 2,

=) +o gee Val eee
; . with vi-y WS fae
_ « Aine hpi Ws by Dae alien So oa
< er ti Na o> ae

J ‘ ; ij on o>
» 4 4 c e~eri . r » it's ts «ee Let inal Wi 1 + >
fall i. rin : es ee ls Oe ee f 5
' ° : ry
. é re vy AM Lig wae}
Ss .
\
'
: a)
‘ i] { o§,
7 —d
*
= =
; ce
_
‘
-
~ ‘
= ‘
= =) =
~
.
i
é
.

LIFE-HISTORY OF THE PARASITES OF MALARIA. oT

Diagrams illustrating the Life-history of the
Parasites of Malaria.

by

Ronald Ross, D.P.H., M.R.C.S.,
Lecturer in Tropical Medicine, University College, Liverpool ;

and

R. Fielding-Ould, M.A., M.B.,
Acting Demonstrator, Liverpool School of ‘Tropical Medicine.

With Plates 30 and 31.

THE parasitology of the red blood-corpuscle of Vertebrates
was opened in 1870 by Ray Lankester’s discovery of the
Drepanidium ranarum. In 1880 Laveran made the
important observation that somewhat similar intra-corpus-
cular organisms exist in the blood of human beings suffering
from malarial fever. Since then Danielewsky, Kruse, Koch,
Dionisi, and others have demonstrated allied parasites in the
blood of reptiles, birds, bats, and monkeys, and Smith and
Kalborne have shown that the disease of oxen called Texas
cattle fever is due to an intra-corpuscular parasite of another
kind. As the result of these observations we are now
familiar with a considerable number of such organisms. All
of them are usually classed among the Protozoa, and in the
somewhat artificial order of the Sporozoa. They are generally
divided into three groups, which are as follows.

Group I. The parasite of Texas cattle fever, Pyrosoma
(or Apiosoma) bigeminum, Smith and Kilborne, and
sunilar organisms found in dogs and some other mam-
malia (?); minute pear-shaped intra-corpuscular bodies,

ie RONALD ROSS AND R. FIELDING-OULD.

which are known to be communicated among oxen by the
cattle tick, Boodphilus bovis.

Group II. Organisms apparently allied to the Gregari-
nide ; found in reptiles ; numerous species.

Group III. Intra-corpuscular amoebze or myxopods found
in man, monkeys, bats, birds, and possibly frogs. Four
species are known to undergo further development in gnats.

It is this last group which claims our attention at present.
The diagrams are meant to illustrate a discourse delivered
by one of us at the Royal Institution (‘ Proceedings of the
Roy. Inst.,’ 1900, and also ‘ Nature,’ March 29th, 1900); but
we shall now give a description sufficient to enable the
reader to follow the life-history from this paper alone. The
figures show the appearance of the parasites as seen in
unstained preparations—the cytology of some of the stages
(figs. 53—60) in the gnat not yet being sufficiently estab-
lished to warrant illustration in a scheme of this kind.

We adopt the name Hemamobide, Wasielewsky, for
the whole group. At least three species occur in human
beings (producing the different varieties of malarial fever) ;
one species in monkeys, three in bats, and two in birds. We
illustrate only the species found in man and birds, those of
monkeys and bats being closely similar to the human species,
(but, so far as we know at present, not identical). The deve-
lopment of four of the species has been followed in gnats.
The three human species develop in gnats of the genus
Anopheles, while one of the avian species (Hamameba
relicta) lives in gnats of the Culex pipiens type. The
insect hosts of the remaining species have not as yet been
found.

So far as we know, the life-history of all the species is
practically identical, and is as follows. The youngest
parasites are found as minute amcebule living within or upon
the red corpuscles of the vertebrate hosts. Hach contains a
nucleus, which stains by the Romanowsky method. Growing
rapidly in size, the amcebulz convert the hemoglobin of the
containing corpuscles into a varying number of brown or black

LIFE-HISTORY OF THE PARASITES OF MALARIA. 573

granules, which are called the melanin or malarial pigment.
These granules lie in the bioplasm of the parasite surrounding
the nucleus. After an interval of from one to several days
(according to the species concerned) the amebule, still
contained within the corpuscle, reach maturity, and become
either (a) sporocytes or (b) gametocytes. In the case of the
amcebulee which become sporocytes the nucleus divides into
a number of segments (varying according to the species).
Each segment of the nucleus surrounds itself with a portion
of the bioplasm, and becomes a spore—the process being
obviously one of simple asexual propagation. Finally the
corpuscle which contains the parasite, and which has now
been almost entirely destroyed by it, bursts and liberates the
spores, allowing them and a small nucleus de reliquat,
consisting chiefly of the melanin, to fall into the liquor
sanguinis. The melanin is taken up by the phagocytes of
the host, while the spores attach themselves to fresh red
corpuscles, become amcebule in their turn, and thus continue
the life of the organisms indefinitely within the vertebrate
hosts.

In the case of the amcebule which become gametocytes
the history is quite different. [tis not yet definitely known
what determines a given amcebula to become either a sporo-
cyte or a gametocyte, but the fact must be accepted. In
the gametocytes the nucleus does not divide as in the case
of the sporocytes—the parasite reaches maturity without
showing any sign of spore-formation. In the majority of
species (genus Hamamceba) the gametocyte has a general
form similar to that of the sporocyte before the spores are
produced; but in one species (genus Hemomenas) the
gametocyte has a special (crescentic) shape, which is recog-
nisable at an early stage in its career. As their name indi-
cates, the gametocytes are sexual forms, male and female.
They possess no function within the vertebrate host, but are
meant to continue the life of the organisms within a second
host—a suctorial insect.

When the gametocytes are drawn into the stomach cavity

574 RONALD ROSS AND R. FIELDING-OULD.

of gnats (middle intestine) they immediately undertake their
sexual functions. The male gametocyte (the nucleus of which
is larger than that of the female) is destined to give origin to a
number of microgametes, or spermatozoa; the female gameto-
cyte develops into one macrogamete, or ovum, together with a
residuum consisting chiefly of melanin. A few minutes after
ingestion by the gnat both male and female gametocytes
break from the enclosing corpuscle, and swell slightly.
Attached to the naked parasite one can now often perceive
one or two small spherical objects, which may possibly be
the homologues of polar bodies. A few minutes later a
quivering movement is observed in the male gametocytes,
due to the emission of the microgametes. These bodies are
long filaments endowed with very active powers of locomo-
tion, and consisting of a thread of chromatin surrounded by
a thin scroll of bioplasm. Breaking away from the parent
cell, and leaving behind the melanin of that cell as a resi-
duum, the microgametes travel through the liquor san-
guinis contained in the stomach of the gnat in search of a
macrogamete. ‘This being found, one microgamete enters
the macrogamete and unites with its nucleus, producing a
zygote.

Shortly after the act of fertilisation the zygote may in some
species become motile (when it is technically called a vermi-
cule), and generally changesits shape. At all events, it travels
towards the parietes of the stomach. If the insect be of an
inhospitable species the zygote perishes ; but if the insect be
hospitable the zygote passes through the parietes and affixes
itself on or just under the outer muscular coat of the
stomach. Here it becomes motionless and commences to
erow rapidly in size.

At first of about the size of a red corpuscle, and still
containing the characteristic black granules of melanin, the
zygote, after a week or so, reaches a very large size ; that is,
it becomes about 60 u in diameter, or about eight times its
original diameter, and about five hundred times its original
bulk. As we have said, we are not satisfied regarding the

Tg: aie

SET

LIFE<-HISTORY OF THE PARASITES OF MALARIA. 575

nature of the nuclear changes during the growth of the
zygotes, but it is clear that the parasite acquires a very
distinct capsule, and that its substance divides into from eight
to twelve meres, which can easily be distinguished without
staining. Hach mere seems finally to become a spherical
blastophore, bearing on its surface a number of filamentous,
or rather spindle-shaped blasts, in the manner depicted in
fig, 60; at least, it is easy, by rupturing a nearly mature
zygote, to expel a number of such bodies. When the zygote
finally reaches maturity the blastophores disappear, leaving
the capsule packed with thousands of the blasts (and con-
taining also some residual fatty globules).

The capsule now bursts spontaneously, and pours the
blasts into the body-cavity of the gnat. On drying and
staining the blasts are easily seen to be of about 12 to 16 mu
in length, with a central nucleus, one or two clear oval areas,
and tapering extremities. No definite movements have been
observed in these bodies—possibly on account of the reagent
(salt solution) which must be used to make them visible in
fresh preparations. By some means or other, however, they
find their way into remote parts of the host, and finally pierce
the capsule of its salivary gland, enter the salivary cells, and
lastly the salivary ducts, in all of which situations they can
easily be seen with the aid of a strong salt solution. From
the salivary ducts they evidently pass through the insect’s
middle stylet or tongue into the circulation of a fresh verte-
brate host, in which it is to be presumed they at once become
the amcebule with which the life-history of the parasites
commenced. At all events, numerous experiments, both on
birds and on man, have demonstrated the fact that gnats
whose salivary glands contain the blasts are capable of
establishing infection by their bites in the appropriate verte-
brate hosts.

It should be noted that this life-history is in no way a
hypothetical one. Kvery fact has been confirmed over and
over again by many capable observers. ‘The stages in the
yertebrate hosts, first established by Laveran and Golgi, have

576 RONALD ROSS AND R. FIELDING-OULD.

been scrupulously studied and have given rise to a mass of
literature already very large. The sexual functions of the
gametocytes—which can be witnessed in vitro,—originally
observed by MacCallum, have been seen also by Koch and
Marchoux ; while the facts are confirmed by the cytological
studies of Bignami and others. The development in the
gnat and the infection of the healthy vertebrate host by the
bite of the gnat, originally established by one of us, have
been confirmed by Daniels, Koch, Grassi, Bignami, Bastia-
nelli, and many others, and are accepted by Laveran, Ray
Lankester, Metschnikoff, Manson, Celli, and other distin-
guished men of science. A full history of the subject of the
relation between malaria and gnats, together with a complete
bibliography, has been written by Nuttall.*

The terminology used above was arranged in consultation
with Professor Herdman, F.R.S. It has been adopted by
Laveran and Manson. Grassi and others had previously
employed the terms gamete and zygote, but used sporo-
zooid for the bodies we call blasts. We use the word
blast somewhat in the sense employed in embryology, and
as synonymous with sexually produced spores. Ray
Lankester suggests for them the name filiform young.

It should be added that, within the capsules of mature
zygotes large black bodies (fig. 67) are often to be found.
It is doubtful whether these have any real connection with
the parasites..

We divide the Hemamecebide into two genera (‘ Nature,’
August 3rd, 1899), namely—

Genus I. Hemameeba, Grassi and Feletti. The gameto-
cytes have a shape like that of the sporocytes before the
spores have been produced.

* Nuttall, ‘ Hygienische Rundschau,’ numerous papers, 1898, 1899, 1900.
Also “On the Réle of Insects . . . . in the Spread of Diseases,” ‘ Johns Hop-
kins Hospital Reports,’ Baltimore, vol. viii.

The most recent figures of stages of the malaria parasites are those published by
Koch, ‘ Zeitschrift fiir Hyg. und Infect.,’ 1899 (photographs) ; Grassi, Bignami,

and Bastianelli, ‘ Annalid *Igiene sperimentali,’ 1899 (plates); ‘Sierra Leone
Expedition,” ‘Thompson Yates Laboratories Report,’ vol. ii (photegraphs).

—.

LIFE-HISTORY OF THE PARASITES OF MALARIA. 577

Genus I]. Hemomenas, gen. nov. (syn. Laverania,
Grassi and Feletti, in part). The gametocytes have a special
(crescentic) shape.

DESCRIPTION OF PLATES 30 & 31,

Illustrating Major Ronald Ross’s and Dr. R. Fielding-Ould’s
paper on ‘The Life-history of the Parasites of Malaria.”

Figs. 1—41 illustrate the two avian species and the three human species in
the blood-vessels of the vertebrate hosts.

Figs. 42—52 illustrate the development of the gametocytes of one of the
human species, selected for the purpose, in the stomach cavity of Anopheles,
or in a drop of blood freshly extracted from the finger (in which the parasites
develop much as they do in the stomach cavity of the insects).

Figs. 53—67 illustrate the further development of the parasites in the
tissues of the gnat.

Fies. 1—7.—Development of He mameba Danilewskii (syn. Halte-
ridium Danilewskii, Labbé) in the blood of pigeons, jays, crows, etc.
The ameebula is elongated, and lies by the side of the nucleus without dis-
turbing its position. Several varieties exist.

Fig. 1.—Spore.

Figs. 2—4.—Growth of ameebula.

Fig. 5.—Sporocyte.

Fig. 6.—The containing corpuscle has burst, leaving nucleus, melanin,
and free spores.

Fig. 7.—Gametocyte.

Fics. 8—14.—Development of Hamameeba relicta (syn. Proteosoma
Grassii, Labbé) in the blood of sparrows, larks, crows, etc. The amcebula
lies at one end of the corpuscle, and pushes the nucleus towards the other
end.

Fig. 8.—Spore.

Figs. 9—11.—Growth of ameebula.
Fig. 12.—Sporocyte.

Fig. 13.—Freed spores.

Fig. 14.—Gametocyte.

Fics. 15—22.—Development of Hamameeba malaria, the parasite of
quartan fever of man, The containing corpuscle is a small or medium-sized

578 RONALD ROSS AND R. FIELDING-OULD.

one, the melanin consists of coarse dark brown eranules, the amoeboid move-
ments are slow, the spores are about eight to twelve in number, development
takes seventy-two hours.

Fig. 15.—Spore.

Figs. 16—18.—Growth of ameebula.

Fig. 19.—First appearance of spore formation.

Fig. 20.—Sporocyte.

Fig. 21.—Freed spores.

Fig. 22.—Gametocyte.

Fries. 23—29.—Development of Hemameba vivax, the parasite of
tertian fever of man, The containing corpuscle is nearly always an excep-
tionally large one, the melanin consists of very fine light brown granules,
amceboid movements are rapid, the spores are about twelve to twenty in
number, development takes thirty-six hours.

Fig. 23.—Spore.

Figs. 24—26.—Growth of amebula.
Fig. 27.—Sporocyte.

Fig. 28.—Freed spores.

Fig. 29.—Gametocyte.

Fries. 30—41.—Development of Hamomenas precox, the parasite of
remittent, pernicious, or estivo-autumnal fever of man. Several varieties,
which are possibly distinct species. The amcebule are small, contain only a
few clumps of black melanin, and retire to the spleen, bone-marrow, ete., on
approaching maturity ; the gametocytes have a special crescentic shape.

Figs. 30—34.—Growth of ameebula becoming a sporocyte.

Fig. 35.—Freed spores.

Figs. 36—39.—Growth of ameebula becoming a gametocyte.

Fig. 40.—Male gametocyte (portion of red corpuscle still present).

Vig. 41.—Female gametocyte (remains of corpuscle entirely disappeared).

Figs. 42—52.—Development of gametocytes of Hemomenas precox
in stomach cavity of Anopheles.

Fig. 42.—Male gametocyte.

Fig. 43.—Female gametocyte.

Figs. 44, 45.—Gametocytes become oval five minutes after ingestion by
the gnat.

Figs. 46, 47.—Gametocytes become spherical a few minutes later. Polar
bodies appear at the margin.

Fig. 48.—Male gametocyte emitting microgametes (the so-called “ flagel-
late body”).

Fig. 49.—Female gametocyte or macrogamete awaiting fertilisation,

Fig. 50.—Free microgametes.

Fig. 51.—Microgamete entering macrogamete.

Fig, 52.—Fertilised macrogamete, or zygote,

24s

LIFE-HISTORY OF THE PARASITHS OF MALARIA. 9579

Fics. 53—67.—Development of Hemomenas precox in tissues of
Anopheles.

Fig. 53.—Zygote approaching inner surface of stomach wall.

Fig. 54.—Zygote piercing stomach wall.

Figs. 55, 56.—Zygotes affixed to outer coat of stomach. They possess
an apparently alveolar structure, and still contain granules of melanin.

Fig. 57.—Zygote increases in size.

Figs. 58, 59.—Zygotes increasing in size and dividing into meres, which
become blastophores bearing blasts.

Fig. 60.—A single blastophore bearing a number of blasts affixed to it,
each by one extremity.

Fig. 61.—Stomach seen by a low power, and dotted with a number of
mature zygotes.

Fig. 62.—A fully mature zygote packed with blasts, some of which are
escaping from a rupture in the capsule.

Fig. 63.—Free blasts in body-cavity of Anopheles.

Fig. 64.—Blasts entering capsule of salivary gland; also lying within
salivary cells and duct.

Fig. 65.—Junction of ducts of three lobes of salivary gland of one side,
with blasts.

Fig. 66.—Blasts escaping from extremity of middle stylet or tongue of
Anopheles.

Fig. 67.—Capsule of a mature zygote containing five large black bodies,
provisionally known as ‘‘ black spores.”

Note.—We may point out that the development of the remaining human
species in Anopheles and of H. relicta in Culex are almost identical with
those of H. precox given in the plates.

All the figures, except Fig. 61, are magnified 2500 diameters. Fig. 61
is magnified about 70 diameters, the stomach tissues being flattened and
extended by the cover-glass.

VoL. 43, PARY 3,—NEW SERIES, RR

>

chi AG a he = me f

peeraes 4

gf ee

tr ea sh

VARIOUS PHASES OF HAMAMCEBIDA. 581

Note on the Morphological Significance of the
Various Phases of Heamame bide.

by

E. Ray Lankester.

THe discovery of true sexual zygosis in unicellular or-
ganisms! has so great an importance that I have thought it
desirable to add a few words to the valuable account given
by Messrs. Ross and Fielding-Ould, and to place before the
reader some woodcuts illustrating the recent discovery of
microgametes and macrogametes in the life-history of Coc-
cidiidz, which serve to emphasise and confirm the discovery
of MacCallum of sexual zygosis in the Hemamcebee. A very
interesting and significant fact is that the microgametes of
these Protozoa are neither more nor less than spermatozoa—
agreeing with the spermatozoa of higher organisms in form
and appearance and in mode of development. It is less
remarkable, though significant, that the macrogamete is
identical in character with the egg-cell or ovum of higher
forms.

The Coccidiidz are closely related to the Hemamcebide.
Their sexual history was discovered but very shortly before
that of the blood-parasites.

In the first woodcut (Figs. 1 to 6) is shown in the upper
three figures the development of the spermatozoa or micro-
gametes of Benedenia octopiana, a coccidian parasite
in the Cephalopod Octopus. The spermatozoa are seen to

1 The Protozoa in which microgametes and macrogametes were known

before the year 1898, viz. Volvox and Vorticellide, are multicellular cell-
colonies of which only special cells become developed as gametes,

582 E. RAY LANKESTER.

form as a series of nucleated outgrowths of the original cell,
leaving a non-nucleated “blastophore” or residual mass, as
in Hzmomenas, PI. 30, fig. 48. In the lower three figures
(Figs. 4, 5, 6) we have an egg-cell which is undergoing
fertilisation. Three free spermatozoa are seen attempting to
effect a junction with it. These figures are after the draw-
ings and description of Siedlecki in ‘Annales de l’Institut
Pasteur,’ 1898, and are copied from Mesnil, ‘ Revue générale
des Sciénces,’ March 30th, 1899.

The development of the spermatozoa or microgametes of a

Fics. 1—6.—Development of microgametes or spermatozoa and fertilisation
of the Coccidian Benedenia octopiana. After Siedlecki, from
Mesnil.

complex multicellular animal may be compared with what
occurs in the unicellular Benedenia and Hemomenas. Our
Figs. 7 to 11 show the development of the spermatozoa of
the earthworm ; they are reproduced from Blomfield’s paper
in vol. xx of this Journal (1880). It will be observed that
in the earthworm, as in the Coccidian and the Hzemameeba,
the spermatozoids form by a centifrugal movement of the

VARIOUS PHASES OF HAMAMGBIDA. 583

segments of the broken-up nucleus of the original sperm
mother-cell, and that thus they form a number of outstand-
ing processes, at first short and ovoid, but later filamentous
in form, upon the surface of a “blastophore,” a residual

Fres. 7—11.—Development of spermatozoa of the Earthworm. After
Bloomfield.

central mass of considerable volume to which this name was
originally given by Blomfield.

As in Benedenia, so in Lumbricus and Hemameeba, the
ripe filamentous spermatozoa become detached from the
blastophore and swim about as active independent bodies,
whilst the blastophore disintegrates and disappears.

The exact character of the spermatozoa of a certain Coc-
cidian (Hchinospora) has been well shown by Leger in the

584 E. RAY LANKESTER.

‘Archives de Zoologie expérimentale,’ 1898. In Fig. 12 we
have reproduced (from Mesnil) his drawings. The sperma-
tozoa are seen to be biflagellate, having a flagellum at each
end of the fusiform body. The modes in which these flagella
may be carried and exercised is shown in the drawings.
Compare these with the active filaments produced by the
male gametocyte of Heemamceba (Heemomenas) which are
shown in PI. 30, figs. 48 and 50.

The first discovery of spermatozoa as the product of a
Coccidian cell was made by Simond (‘Ann. de I’Institut
Pasteur,’ 1897. We reproduce here (Fig. 18) one of his
drawings. Simond made his discovery in the typical well-
known parasite of the epithelial cells of the rabbit’s intestine
and liver—the Coccidium oviforme. He showed that
whilst Coccidium oviforme very generally breaks up
into sporocytes, which enter uninfected epithelial cells and
develop into full-sized Coccidia directly, yet the cell indi-
viduals of Coccidium oviforme also can and do under
certain circumstances become gametocytes, instead of break-
ing up into sporocytes; some developing a micropyle and
becoming each a single ovum or macrogamete, whilst others
(lying all the time within an epithelial cell of the rabbit)
give rise to a crop of spermatozoa or microgametes, resting
on a residual mass or blastophore just as in Lumbricus. The
crop of spermatozoa and the blastophore of Coccidium
oviforme is shown in the woodcut Fig. 138.

The existence within the Protozoa of the form and mode
of development of the male microgametes now so long familiar
to us in higher animals, where they are called “ spermatozoa,”
is one of the most striking results of the recent researches
on Sporozoa. It is all the more curious when we remember
that these cell parasites, such as Coccidium oviforme and
Hemomenas precox, are amongst the most minute of
the characteristically minute Protozoa.

T will venture on one further comparison and comment
in regard to the life-history of Haemomenas precox as
described by Surgeon-Major Ross. Ross discovered the

VARIOUS PHASES OF HAMAMGBIDA. 585

history of the fertilised egg (zygote) of the malaria parasite
in the stomach wall and tissues of the gnat (Anopheles), and

Fic. 12.—Spermatozoa (microgametes) of the Coccidian Echinospora.
After Leger, from Mesnil.

he, with Mr. Fielding-Ould, has given a series of important
figures of the development of the zygote in Plates 30, figs.
53 to 57, and Plate 31, figs. 58 to 67, accompanying their
paper in the present number of this Journal. Ross has
shown that the zygote breaks up within its capsule or cyst

Fic. 13.—Stage in the development of spermatozoa or microgametes of
Coccidium oviforme, from the epithelial cells of the rabbit’s intestine.
The microgametes are seen supported on the central “ blastophore.”
After Simond, from Mesnil.

into a number of “meres” (figs. 58, 59), and that each of
these meres gives rise to a dense crop of filiform young on

586 E. RAY LANKESTER.

its surface, which he terms “‘ blasts” (fig. 60). The “blasts ”
or filiform young infect a new host when injected into his or
her blood by the Anopheles which harbours them.

I desire to point out that the fission process by which the
fertilised zygote gives rise to these filiform blasts resembles
the production of microgametes or spermatozoa, and that the
blasts themselves are morphologically identical with micro-
gametes, whilst a blastophore of residual material accom-
panies their evolution. On the other hand, it is a rule in
other organisms that the fission products of fertilised egg-
cells resemble in form and development the macrogametes or
female cells, and do not assume the characters of micro-
gametes. The malaria parasite is, it seems, remarkable in
being an exception to this rule. The fission products of the
fertilised cell are not large cells produced by binary fission,
and comparable in size and form to the female cells or
macrogametes, but are in form and mode of development
identical with male cells or microgametes. We may call
them andromorphous or spermatomorphous “ blasts ” or cells,
whereas in other Coccidia, as well as in Volvocinean flagel-
lates and in the tissue-forming Enterozoa, the “ blasts”
produced by the fission of the fertilised egg-cell are odmor-
phous or gynzcomorphous cells.

In all other cases the spermatomorphous cell seems only to
be produced with the special and limited function of zygosis ;
it is distinctively a fertilising cell. But in the Hamameebide
a generation of spermatomorphous cells is produced which
simply carry on their individual life, penetrate the blood-
corpuscles of a vertebrate host, and divide into sporocytes.

We are certainly accustomed to associate the phenomenon
of non-sexual reproduction in higher animals with the produc-
tion of odmorphous cells. It is only an egg-cell which is
capable of multiplication and the production of new indi-
viduals of the species, without conjugation with a
fertilising cell (parthenogenesis). There are no cases on
record, at any rate among animals, of parthenogenesis by
means of male cells or male individuals. Speculation and

& » Rhee, aoe yy

of OR —~ +

VARIOUS PHASES OF HAEMAM@BIDA. 587

experiment have both been brought to bear on the question
as to whether an odmorphous cell can act as fertiliser to
another, and as to whether an andromorphous cell (a sperma-
tozoon) can be made to develop a new individual if supplied
with a cell body but without the addition of the nuclear
matter of an odmorphous cell. It seems to me that we have
in the case of the spermatomorphous or andromorphous
blasts or “ young” of the malaria parasite a distinct proof
that the spermatozoon is, so far as its essential nature is con-
cerned, capable of acting the part of the solely sufficient
germ in a parthenogenetic reproduction or multiplication ;
and that it is, therefore, not of the essence of “solely suffi-
cient germs” that they should be egg-cells or odmorphous.
At any rate, we have, I think, in the blasts or filiform young
of the malaria parasite an altogether exceptional case of
elements of the male form carrying on without acting as
fertilisers, but as “solely sufficient,” the life of the species.
We have here, indeed, a parthenogenesis by means of male
elements. ‘The parthenogenesis hitherto known in animals
is ‘ gynecocratic ;” that exhibited by the “blasts” of the
Hemameoebide is ‘‘ androcratic.”

Probably some instances among the Protophyta of the fis-
sion and multiplication of flagellate “ zoospores” may be
placed in the same category of ‘androcratic partheno-
genesis.” For instance, the ‘‘coccus forms” of Schizophyta
are oomorphous, and their multiplication without fertilisa-
tion is a “gynecocratic parthenogenesis.” But the bi-
flagellate bacillus form should perhaps be regarded as an
andromorphous cell, and its multiplication by fission is
androcratic parthenogenesis. ‘There is not, however, in this
case the same reason for regarding the flagellate cell as
really identical with a spermatozoid or microgamete as there
is in the case of the Hamamosbide ; for in the latter it is not
only the form of the cell, but its mode of development by
centrifugal proliferation and the production of a “ blasto-
phore ” which characterises the ‘ blasts” as truly male cells.

I may remind the reader in conclusion that the word

vou. 43, PART 3.—NEW SERIES. 8S

588 BE. RAY LANKESTER.

“parthenogenesis ” is conveniently restricted to a repro-
ductive process, not by neutral or ‘ medeterocratic” cells,
but by cells essentially fitted for sexual zygosis which, in the
exceptional cases designated by the term “ parthenogenesis,”
develop to maturity without zygosis.

The word “ parthenogenesis” is equally applicable to the
development of a macrogamete (gynzcocratic), and to that
of a microgamete (androcratic) wher it occurs without union

with a cell of the opposite sex.

With Ten Plates, Royal 4to, 5s.
CONTRIBUTIONS TO THE KNOWLEDGE OF RHABDOPLEURA
AND AMPHIOXUS.
By E. RAY LANKESTER, M.A., LL.D., F.R.S.
London: J. & A. CHURCHILL, 7, Great epeoten Street.

Quarterly Journal of Microscopical

Science.

The SUBSCRIPTION is £2 for the Volume of Four Numbers ;
for this sum (prepaid) the JournaL is sent Post Free to any part
of the world.

BACK NUMBERS of the Journat, which remain in print, are
now sold at an uniform price of 10/-.

The issue of Supprement Numbers being found inconvenient,
and there being often in the Hditor’s hands an accumulation of
valuable material, it has been decided to publish this Journal at
such intervals as may seem desirable, rather than delay the appear-
ance of Memoirs for a regular quarterly publication.

The title remains unaltered, though more than Four Numbers
may be published in the course of a year.

Each Number is sold at 10/-, and Four Numbers make up a
Volume.

London: J & A. CHURCHILL, 7 Great Marlborough Street.

TO CORRESPONDENTS.

Authors of original papers published in the Quarterly Journal
of Microscopical Science receive twenty-five copies of their
communication gratis.

All expenses of publication and illustration are paid by the
publishers.

As a rule lithographic plates, and not woodcuts, are used in
illustration.

Drawings for woodcuts should nor be inserted in the MS.,
but sent in a separate envelope to the Editor.

Contributors to this Journal requiring extra copies of their
communications at their own expense can have them by applying
to the Printers,

Messrs. ApLARD & Son, 224, Bartholomew Close, E.C., on
the following terms :

For every four pages or less—

25 copies : 3 ; : 5/-
1 Same : é : : 6/-
£00. ~,, ; 7/-

Plates, 2/- per 25 if uucoloured ; if coloured, at the same rate for
every colour.
Prepayment by P.O. Order is requested.
ALL CoMMUNICATIONS FOR THE EDITORS TO BE ADDRESSED 'TO THE CARE
oF Messrs. J. & A. CHurcuILi, 7, Great Mar.eorouca Srreet,
Lonpon, W.

THE MARINE BIOLOGICAL ASSOCIATION

OF THE

UNITED KINGDOM.
A032
Patron—H.R.H. the PRINCE OF WALES, K.G., F.R.S.
President—Prof. E. RAY LANKESTER, LL.D., F.R.S.

40)

THE ASSOCIATION WAS FOUNDED “ TO, ESTABLISH AND MAINTAIN LABORATORIES ON
THE COAST OF THE UNITED KINGDOM, WHERE ACCURATE RESEARCHES MAY BE CARRIED
ON, LEADING TO THE IMPROVEMENT OF ZOOLOGICAL AND BOTANICAL SCIENCE, AND TO
AN INCREASE OF OUR KNOWLEDGE AS REGARDS THE FOOD, LIFE CONDITIONS, AND HABITS
OF BRITISH FOOD-FISHES AND MOLLUSCS.”

The Laboratory at Plymouth
was opened in 1888. Since that time investigations, practical and scientific, have
been constantly pursued by naturalists appointed by the Association, as well as by
those from England and abroad who have carried on independent researches.

Naturalists desiring to work at the Laboratory

should communicate with the Director, who will supply all information as to
terms, &e.

Works published by the Association

include the following :—‘ A Treatise on the Common Sole,’ J. T. Cunningham, M.A.,
4to, 25/-. ‘The Natural History of the Marketable Marine Fishes of the British
Islands, J. I’. Cunningham, M.A., 7/6 net (published for tke Association by
Messrs. Macmillan & Co.).

The Journal of the Marine Biological Association

is issued half-yearly, and is now in its fifth volume (price 3/6 each number).

In addition to these publications, the results of work done in the Laboratory
are recorded in the ‘ Quarterly Journal of Microscopical Science,’ and in other
scientific journals, British and foreign.

Specimens of Marine Animals and Plants,

both living and preserved, according to the best methods, are supplied to the
principal British Laboratories and Museums. Detailed price lists will be forwarded
on application.

TERMS OF MEMBERSHIP.

ANNUAL MEMBERS . : 3 . £1 1 Oper annum.
Lire MeMBERs . ; : : . 15 15 0O Composition Fee.
FOUNDERS . - : : : = -1067:0:-0 3 =
Governors (Life Members of Council) 500 O -0 = Ra

Members have the following rights and privileges:—They elect annually the
Officers and Council; they receive the Journal free by post; they are admitted to
view the Laboratory at any time, and may introduce friends with them; they have the |
first claim to rent a table in the Laboratory for research, with use of tanks, boats, &c.;
and have access tothe Library at Plymouth. Special privileges ure granted to Governors,
Founders, and Life Members.

Persons desirous of becoming members, or of obtaining any information with
regard to the Association, should communicate with—

The DIRECTOR,
The Laboratory, ~
Plymouth. .

New Series, No. 172 (Vol. 48, Part 4). Price 10s.

SEPTEMBER, 1900.

THE

QUARTERLY JOURNAL

OF

MICROSCOPICAL SCIENCE.

EDITED BY

KE. RAY LANKESTER, M.A., LL.D., F.R.S.,

HONORARY FELLOW OF EXETER COLLEGE, OXFORD; CORRESPONDENT OF THE INSTITUTE OF FRANCE,
AND OF THE IMPERIAL ACADEMY OF SCIENCES OF ST. PETERSBURG, AND OF THE ACADEMY
OF SCIENCES OF PHILADELPHIA; FOREIGN MEMBER OF THE ROYAL BOHEMIAN
SOCIETY OF SCIENCES, AND OF THE ACADEMY OF THE LINCEI OF ROME;
ASSOCIATE OF THE ROYAL ACADEMY OF BELGIUM; HONORARY MEMBER
OF THE NEW YORK ACADEMY OF SCIENCES, AND OF THE
CAMBRIDGE PHILOSOPHICAL SOCIETY, AND OF THE ROYAL
PHYSICAL SOCIETY OF EDINBURGH ; HONORARY
MEMBER OF THE BIOLOGICAL SOCIETY
7 OF PARIS;
DIRECTOR OF THE NATURAL HISTORY DEPARTMENTS OF THE BRITISH MUSEUM; FULLERIAN PROFESSOR
OF PHYSIOLOGY IN THE ROYAL INSTITUTION OF GREAT BRITAIN.

WITH THE CO-OPERATION OF

ADAM SEDGWICK, M.A., F.RBS.,

FELLOW AND TUTOR OF TRINITY COLLEGE, CAMBRIDGE 3

W. F. R. WELDON, M.A., F.RB.S.,

LINACRE PROFESSOR OF COMPARATIVE ANATOMY AND FELLOW OF MERTON COLLEGE, OXFORD;
LATE FELLOW OF ST. JOHN’S COLLEGE, CAMBRIDGE 5

AND

SYDNEY J. HICKSON, M.A., F.R.S.,

BEYER PROFESSOR OF ZOOLOGY IN THE OWENS COLLEGE, MANCHESTER,

WITH LITHOGRAPHIC PLATES AND ENGRAVINGS ON WOOD.

‘LONDON:
J. & A. CHURCHILL, 7, GREAT MARLBOROUGH STREET.
1900.

Adlard and Son,] [Bartholomew Close.

CONTENTS OF No. 172.—New Series.

MEMOIRS:

Hippolyte varians: a Study in Colour-change. By F. W. GamBte,
D.Se., Owens College, Manchester, and F. W. Kezsir, M.A.,
Caius College, Cambridge, late Assistant, Lecturer in Botany,
Owens College, Manchester. (With Plates 32—36)

On the Nephridia of the Polycheta. Part III. The Phyllodocide,
Syllide, Amphinomide, etc., with Summary and Conclusions. By
Epwin S. Goopricn, M.A., Aldrichian Demonstrator of Compara-
tive Anatomy, Oxford. (With Plates 37—42)

Nouvelles Observations sur les Peripatus de la Collection du Musée
Britannique. Par E L. Bouvier, Professeur au Muséum d’Histoire
Naturelle de Paris

TITLE, ConTENTS, AND INDEX.

PAGE

589

699

749

HIPPOLYTE VARIANS. 589

Hippolyte varians: a Study in Colour-change.
By
F. W. Gamble, D.Sc.,
Owens College, Manchester,
and

F. W. Keeble, MI.A.,
Caius College, Cambridge ; late Assistant Lecturer in Botany, Owens
College, Manchester.

With Plates 32—36.

ConTENTS.
PAGE
Introduction. : 4 : : : : pie)
Section I. Methods . ; ‘ . 595
» ALL. Some Colour Forms of Hinpolyte varians : . 601
», III. “Chromatophores”’ and other Colour Elements. » 605
» LV. The Colour Mutability of Hippolyte varians . O12,
5 V. The Nocturnal Colour—Nocturnes 4 : ~ (88
» VI. Periodicity of Colour-change : 635
», WII. The Control of the ‘*‘ Chromatophores :” the Parts oer
by the Eye, Central Nervous System, and by the
**Chromatophores ” themselves in effecting Colour-
change ; : . 643
», VIII. Summary of Bepedadeutal ecards 3 . 651
Appendix—Experimental Tables ; : F : + 1658
Literature : ; : ; ; . 692

INTRODUCTION.

Ir is well known that the prawn Hippolyte varians may
be found among the seaweeds in the lower tidal pools along
VoL. 43, PARY 4,—NEW SERIES. 7 r

590 F. W. GAMBLE AND F, W. KEEBLE.

the sea-shore or by trawling in the “ Laminarian zone.”
Whilst specimens so obtained may present colours ranging
through the whole gamut of the spectrum, many exhibit an
astonishingly close resemblance to the colour of the weeds,
zoophytes, or other objects to which they obstinately cling.
Attracted by this phenomenon of “ protective resemblance,”
naturalists, who have desired to record its features, have
observed that the prawns change colour ina very short time:
that an emerald green or rich brown colour may lose much
of its brilliancy or even its characteristic tone within the time
elapsing between capture and subsequent examination in the
laboratory. The trivial name varians has thus come to
connote not merely that the colour of these prawns exhibits
great individual differences in tint and pattern, but that, in
addition, the colour of the same individual may alter. It is
but a step further to the idea that all the different colour
varieties may be capable of passing into one another—a
possibility often expressed but never experimentally verified.

The bare fact of colour-change among Crustacea appears
to have first been observed and recorded by Kroyer (1842)
in this very species Hippolyte varians, or, as he called it,
H.smaragdina. “In this species,” he says, “I have ob-
served a very remarkable colour-change. The usual emerald
green colour of those specimens which I have placed with sea
water in a glass vessel passed rapidly into an olive or into a
bluish-green colour. The azure spots behind the anterior
edge of the carapace became so indistinct that did I not
know their position I should have overlooked them. The
longitudinal stripe on the carapace changed from blue to
yellow, and finally disappeared completely. I believe I have
noticed similar changes in other species of this genus, but
none so plain or so striking” (1842, p. 244). Other natu-
ralists have noticed the same kind of change in this and other
Crustacea. Fritz Miller, for example (1880-81), showed
that fresh-water prawns (Atyoida potimirum, Palemon
potiporanga) of South America, when taken from their
habitat and placed in a glass vessel, rapidly lose their brown

HIPPOLYTE VARIANS. 591

or black colour, and become colourless and transparent ; the
first named in the course of a few days, the Palemon in a
few hours. Palzemon, moreover, was seen to pass through
a blue colour phase.

These facts clearly indicated an interesting line of experi-
mental work, which Pouchet took up in the early seventies
with the most important and suggestive if not final results.
From 1872 he published a series of memoirs culminating in
that entitled ‘Changements de coloration sous Vinfluence
des Nerfs’ (1876). In this paper—by far the most im-
portant of those dealing with colour-change in Crustacea—
not only were the facts of colour mutability correlated for
the first time with changes of the pigment spots, but what is
much more important, the rationale of the change was
suggested as the result of experiments made at Coste’s
zoological station at Concarneau on Palwmon, Crangon,
and Hippolyte.

Starting with the vague notions of fishermen, that fishes
and Crustacea change in colour according to the tint of the
sea bottom, Pouchet experimented with white and black
dishes, and found that Palemon serratus (the form upon
which his results are chiefly based) alters its colour sympa-
thetically, becoming dark on a dark, colourless on a white
ground. This change is effected by the expansion and con-
traction of the pigment spots which are controlled by the
nervous system. By cutting off the eyes, a dark coloration
ensued, which remained unaltered until the eyes were re-
generated. The loss of the power of colour-change thus
appeared to be due to loss of sight, and the sequence of
events in a normal prawn was stated by Pouchet in these
terms (Conclusions, Nos. 17 and 18, p. 161) :

“ La fonction chromatique doit étre définie: un ensemble
d’actions réflexes sur les chromoblastes, dont le point de
départ peut étre impression visuelle résultant des propriétés
actiniques du milieu ambiant. Les nerfs sont les conducteurs
de cette action réflexe: ils peuvent done provoquer l’expan-
sion ou le retrait des chromoblastes.” The expression “ pro-

592 F. W. GAMBLE AND F. W. KEEBLE.

priétés actiniques du milieu ambiant” makes it doubtful
how far Pouchet attributed colour-change in the prawn to the
change in tint of the bottom, in other words to the varying
quality of the light, or to the light intensity, or to both
these possible causes. Other passages in the paper show
that Pouchet attributed to the varying quality of the light
reflected from the differently coloured surfaces on which
the prawns happened to be resting, an important and perhaps
the chief share in the resulting colour-change. But there
is still another of Pouchet’s conclusions, which tends to
show that he regarded the varying quantity of the light as at
least a subsidiary factor which, acting through the eye and
nervous system on the pigment spots, may modify the colour.
He says (p. 151), “ L’obscurité de la nuit n’a aucune influence
sur les changements que présentent les animaux, tandis que
Vobscurité artificielle provoque au contraire des modifications
qui pour n’étre pas constantes ni toujours bien définies n’en
sont pas moins sensibles.” This conclusion Pouchet drew
from his observations on fishes (turbot, goby, dragonet) as
well as from those on Crustacea, and it is on this point more
than on any other that we find ourselves opposed to him.
It would, indeed, be singular if an animal were sensitive to
change in light intensity, and yet remained the same colour
by night as by day. In the sections on nocturnal colour and
on periodicity we show not only that Hippolyte varians
undergoes a rhythmical sequence of colour-change composed
of nocturnal and diurnal phases, but that this is a habit which
persists though the light or the darkness is maintained con-
stant for days together.

The effects of varying light intensity on Crustacea have
attracted but little attention since Pouchet’s memoir in 1876.
Matzdorff (1882) has experimented with Idothea and con-
firmed many of Pouchet’s conclusions. Jourdain (1878),
working on Nika edulis (a prawn belonging to a family
distinct from the Hippolytide), obtained some interesting
results. This form, he found, passed from a translucent
nearly colourless condition in sunlight or diffuse hght to a

HIPPOLYTE VARIANS. 593

red colour in the dark. If it was then replaced in the
light the red colour disappeared. Jourdain concludes
(loc. cit., p. 302), “dés lors au moins lorsq’on Vétudie en
captivité le Nika n’a pas la méme couleur la nuit que le
jour,” but he does not appear to have made any observations
at night to verify this. Jourdain also found that if the tem-
perature is lowered to 5° or 6° C. the colour-changes are
effected more slowly. In the case of specimens in which the
eyes had been removed, the colour became and remained
red at normal temperatures, was ultimately lost at or near
0° C., but returned if the water was warmed, and also
when the eyes regenerated. Hye-amputated specimens ex-
posed to very bright light for some time lost some of their
red colour; but in all these experiments a certain number
of the prawns behaved in a different manner.

On the subject of the present work—Hippolyte varians
—but little experimental evidence has been collected. Beyond
the single result that, on a dark ground, green Hippolyte
became reddish brown, Pouchet had little to record. More
recently, however, Professor Herdman (1892, 1893, 1898),
Mr. Hornell (1897), and M. Malard (1893) have made trials
to test the colour mutability of this species on differently
tinted weeds. Professor Herdman concluded (1898) “ that
Hippolyte varians can change its colouring, though not
in a very short space of time,’ but the change was not a
close match with the tint of the new weed. Mr. Hornell
concludes from experiments at Jersey that a power of sympa-
thetic colour-change is equally well shown in the light and
inthe dark. We have ourselves made the observation that
even when the Algzw are changed in the dark, a colour-change
occurs which in some cases may match the tint of the new
weed ; and we offer an explanation of the apparently remark-
able phenomena in the section on recovery from the nocturnal
colour (Sect. IV, pp. 614 and 616).

M. Malard (1898) found that green Hippolyte become red
in the dark, but he does not appear to have followed up this
observation by experiments at night.

594 F. W. GAMBLE AND F. W. KEEBLE.

It will be readily gathered from this historical sketch that
there has been no attempt to completely investigate in Hip-
polyte the different factors which in higher animals, such
as the frog and chameleon, are known to be effective in pro-
ducing a change of colour. In the present paper we deal
with the effects of natural and artificial stimulation—both by
agents, such as light, working through the eye, and by others,
such as temperature, affecting the different parts of the body
equally—on the general colour and on the “ chromatophores.”
The research, on which we are still engaged, was commenced
in the Owens College Zoological Research Laboratory, and
was continued during the greater part of 1898 in the labora-
tory of the Lancashire Sea Fisheries Committee at Piel, near
Barrow. For permission to work in the laboratory we are
indebted to Prof. Herdman, and we beg to tender our hearty
thanks for the manner in which the resources of the labora-
tory have been placed at our disposal. During the present
year (1899) our investigations have been carried on, thanks
to the generous hospitality of M. E. Perrier, in the Labora-
toire Maritime de Tatihou, St. Vaast, Normandy.

The problems of colour-change are so complex that this
research, which promised to be brief, has proved to be
well-nigh interminable ; at least we at present see no pro-
spect of the vein giving out. We therefore have decided
to give our chief results in order that we may be the freer
to pursue our investigations into some of those questions
mentioned in the text, to which these results have given
rise. We desire specially to draw attention to the section
dealing with “ Nocturnal Colour,” with “ Periodicity of
Colour-change,” and to the excellent coloured sketches of
Hippolyte on different weeds. These sketches, which we
owe to the skill and kindness of Miss D. Richardson, repre-
sent animals which had been allowed to make a choice as
to a place of anchorage among a variety of weeds. Even
the briefest examination will show how well in each case
Hippolyte avails itself of its opportunity.

Our thanks are due to Professors Hickson and Weiss for

HIPPOLYTE VARIANS. 595
their kindness in giving us the facilities necessary for the
prosecution of these researches.

Srotion I.
Methods.

There are in any research on colour-change three essential
requirements: a standard illumination, observation
under constant light conditions, a means of rapid
record of the observed colour. No one of these have
we been able to meet satisfactorily.

As our standard illumination we employed light from an
incandescent gas burner.

Our colour records were made by observing Hippolyte
against the white background of a porcelain dish.

In recording colours we at first attempted to supplement
verbal descriptions by the use of Maxwell’s colour top, but
we were compelled to fall back upon water-colour sketches.
We now content ourselves with a terse note of the colour
and a careful description of the condition of the “ chroma-
tophores,” as seen by transmitted and by reflected light
under the microscope.

The experience we have gained leads us to think this
last mode of recording may, after it has served as an aid
in unravelling the complexity of the “ chromatophores”
themselves, prove alone sufficient as a colour record.

It is necessary, of course, to note the condition of the
“chromatophores” at the first moment of examination, since
these bodies, or rather their pigments, are so susceptible to
light as to immediately and profoundly change their con-
dition when exposed to the powerful light necessary for
microscopic observation. When the animal under obser-
vation is not required for further experiment, change in its
colour condition may be considerably retarded by placing it
in water near the freezing-point, or, in some cases, by drop-
ping the animal into water of about 90°F. Hippolyte in
the latter case rapidly succumbs, but colour-changes in the

596 F, W. GAMBLE AND F. W. KEEBLE.

living or the dead animal exposed to these conditions take
place with sufficient slowness to admit of careful examina-
tion.

When trawling and shore collecting, at night or early
morning, the colours of the animals as they appear when
taken out of the net are observed by the light of paraffin
lamps. Though, by this means, it is impossible to judge
the fine shades of colour with sufficient accuracy for close
comparison with those noted under the more constant con-
ditions described above, yet it serves to give a general idea
of the colour of the animal; nevertheless with practice a
fair judgment can be made. The susceptibility of Hippo-
lyte varians to temperature changes, incidentally referred
to, is only one indication among many of the fact that it is
less hardy than many of its allies.

We found it necessary to spend a considerable time in
devising an apparatus in which specimens under experiment
could be supplied with aérated water and with food. Aided
by a grant from the British Association Committee, we
constructed an apparatus which serves for the culture of
the animals, and also for determining whether they flourish
better in vessels through which a constant stream of water
is passing or in similar vessels through which a current of
airis drawn. Inasmuch as the water current in the former
induces the air current in the latter series, we have a means
of accurately determining this question. After a prolonged
trial we find that the prawns on the whole flourish better
in what we will call, for convenience, the “air-circula-
tor” dishes. It is true that we made no effort to exhaus-
tively demonstrate this interesting point, being only in search
of the most favourable conditions for experimenting upon
Hippolyte.

Our apparatus consists of a large aspirator bottle, of a
capacity of about one and a half gallons (Fig. 1,4). The
neck of the bottle is fitted with a cork bearing three tubes
(a, b, c). The lateral opening below has a cork bearing one
tube, the exit-tube. One of the three former tubes is of

HIPPOLYTE VARTANS, 597

Fie, 1,

|

|

[|
iy

il

ih

|

Hl

Circulatory apparatus. A is the aspirator by which air is sucked through the
‘‘air-circulator ” flasks B and C, and then through A to replace the
water circulating through D and EH. The rate of the circulation depends
upon the vertical distance x’ y between the level of x (the commence-
ment of the outlet tube) and y (the point of exit of the water from the
apparatus). Of the three tubes (a, , c) passing through the cork of the
aspirator A, a allows air to escape in filling the bottle through 4 from the
main tank of the laboratory, while ¢ transmits the air from the flasks B
and C.

598 F. W. GAMBLE AND F. W. KEEBLE.

wide bore and of stout glass; it is connected with the main
tank in the Piel Laboratory, from which the bottle can be
filled in about one minute. A second tube (b), the pressure-
tube, passing down almost to the level of the exit-tube,
serves, when the apparatus is working, to give the aspirator
the action of a Mariotte’s bottle,—that is to say, to maintain
the rate of flow approximately constant (see F. F. Blackman,
‘Trans. Roy. Soc.,’ 1895).

To this tube is connected a series of glass flasks, through
which air entering the aspirator must pass (see Fig. 1, B
and C). The exit-tube, fitted into the lateral tubulure of
the aspirator, is at its commencement (x) of a very fine bore,
and connects on by its wider end, which projects beyond the
aspirator, with the first of our series of ‘‘ water-circulator ”
dishes (D and E). Each “ water-circulator” is made of a
glass dialyser frame having the form of a low cylinder, open
above and below and provided with a lateral tubulure. To
the bottom rim of this dialyser a glass plate is affixed by
means of suitable wax. The exit-tube from the aspirator
is connected with another passing through the cork in the
tubulure of the dialyser, and so bent as to follow the curved
side of the dish, in order that the water which it conveys
may enter the dish at a point opposite the tubulure, and
so be constrained to circulate before making its exit.

Through a second hole in the cork a glass tube just pro-
jects into the dish, and serves to carry the water to a second
similar ‘‘ water-circulator,” whence it flows toathird. To the
upper rim of each “ water-circulator” a glass plate ground
at its edges has to be fixed. From the last of this series
the exit-tube discharges the water which has circulated
through the series.

To prepare the apparatus for action, the aspirator is filled,
a wide tube (the escapement-tube) just projecting through
the cork of the neck being opened to allow the air to escape.
The aspirator being full this tube is closed; the “ air-circu-
lator ” flasks (the arrangement of the tubes of which will be
readily understood by reference to Fig. 1) are filled to a

HIPPOLYTE VARIANS. 599

convenient height with water; the “ water-circulator”’ dishes
are filled completely with water, the glass plates are carefully
slid on, and thus each of these dishes comes to be, from the
physical point of view, a mere dilatation of a long tube
completely filled with water.

Suction is now applied at the open end of the exit-tube
from the last ‘ water-circulator,” air passes through the air-
circulators into the aspirator pari passu with the outflow
of water into the water-circulators. The rate of flow is
determined by the difference in level between the lower end
of the pressure-tube and the free end of the exit-tube from
the last water-circulator (x! y). By raising or lowering this
latter tube the rate is varied. The rate which we found
most favourable for the cultivation of our Hippolyte was
from 12 ¢.c. at night to about 65 c.c. per minute during the
day, a rate which necessitates the refilling of the aspirator
some seven times a day. By means of an arrangement of
tubes fitted with two-way cocks, any single “ water-” or “ air-
circulator ” can be cut off without interfering with the circu-
lation through the others.

The form of the “ water-circulator ” dishes described above
was chosen in order that experiments on the influence of
monochromatic light upon the colour-changes in Hippolyte
might be made. To this end we employed the original, as
well as a modified form of Landolt’s “ Strahlenfilter,”’ which
consists of a cylindrical vessel with glass ends and metal
side, glass plates accurately dividing the chamber into two
or three compartments of required depths. These compart-
ments are filled, through openings in the metal side of the
Strahlenfilter, with the coloured solution made to Landolt’s
prescription (see 1894). On some occasions, to ensure high
intensity, light from the incandescent gas burner was re-
flected through the liquid colour-filter into the “ water-circu-
lator” beneath.

The colour-filters were, in our hands at least, eminently
unsatisfactory, and a more convenient form of light-filter is
much to be desired (see Nagel, 1898).

600 F. W. GAMBLE AND F. W. KEEBLE.

We have been experimenting recently with a more simple
colour-screen consisting of a deep narrow “cell,” made by
clamping two pieces of plate glass vertically against a stout
piece of india-rubber tubing curved in the formofaU. The
“cell” so formed is quite water-tight. The coloured solu-
tions (potassium chromate, copper sulphate, and certain
aniline dyes) recommended by Nagel (1898) were then tested
severally in different strengths and in mixtures by a Brown-
ing hand spectroscope. Trial alone gives the strengths
requisite for cutting off any portion of the spectrum which
it is desired to eliminate. By this means either a broad or a
narrow strip of the spectrum can be employed.

In many ways this form of colour-screen is more con-
venient than Landoit’s, but it has the drawback that for
monochromatic work the light intensity is apt to be low—
lower, in fact, than that transmitted by the Landolt screen.

For our “air-circulators”? we now use ordinary glass
flasks, which have the advantage of admitting of ready mani-
pulation, though their curved sides make the observation
of the enclosed animals somewhat more difficult than it is
in the case of the “ water-circulator ” dishes, with flat plates
above and below.

By means of the “circulating” apparatus we have been
able to keep isolated animals under constant conditions for
upwards of three weeks, and it is our intention to endeavour
to ascertain whether by its means broods of young Hip-
polyte from a parent of a known colour may not be reared
under known conditions.

Alge, especially of the more delicate kinds, are greedily
eaten by Hippolyte varians. In default of these the
prawns will live upon dead animals and plants, and may even
kill and eat specimens of their own kind.

We have made a fairly extensive trial of preservatives
with a view to keeping the colour of these prawns. Alcohol,
glycerine, formaldehyde, sugar and water, potassium acetate,
chrome alum, carbon tetrachloride, have been tested for this
purpose. On the whole, formaldehyde (formalin 2 per

HIPPOLYTE VARIANS. 601

cent.) is decidedly the best, and retains the “ chromatophores”
and their pigments remarkably well. It is the only reagent
which preserves the blue colour of some of these prawns, but
the inevitable loss of transparency destroys the delicacy of
the azure tint of the living animal.

For histological work on the chromatophores, owing to the
complete solubility of the pigments of the body in alcohol of
higher grades and their alteration by other hardening re-
agents, we have been compelled to rely very largely upon
careful and repeated observation of living transparent speci-
mens. Only in this way can a true idea be formed of the
several pigments, of their activities towards different stimu-
lation, and of the relations of the chromatophores to the
vascular, muscular, and nervous systems. For staining
chromatophores in the fresh state, methylene blue was given
a short but not altogether satisfactory trial. For subsequent
observation material was fixed with osmic acid or its vapour,
washed with weak chromic acid, and preserved in alcohol.

Secrion IT.
Some Colour Forms of Hippolyte varians.

The close resemblance of Hippolyte in colour and in
pattern to its surroundings has been remarked by many
naturalists. Not merely are the markings and tints similar
to those of the weed or zoophyte amongst which it lives, but,
as in many other cases of ‘ protective resemblance,” the
animal when discovered remains quiescent, often requiring
a vigorous shake to induce it to let go its hold. When dis-
placed it jumps towards some other object, on reaching
which it attaches itself and instantly subsides again into its
quiescent condition. That the prawns exert powers of
selection with respect to their weed will be readily realised
from Pls. 32 and 33, figs. 1 to 9, representing prawns placed in
a dish with sea water, to which subsequently pieces of dif-
ferent coloured weeds were added. The prawns were left

602 F. W. GAMBLE AND F, W. KEEBLE.

free to select their weeds, and, as is seen in the figures, they
succeeded in making wonderfully accurate colour matches.

It is noteworthy that in captivity the prawns often lie
beneath and along the weed, except when the light falls
only from above, in which case the animals tend to place
themselves in a vertical position (Fig. 2).

Iie, WY.

im

MUU

Showing the vertical position adopted by Hippolyte varians when illumi-
nated by diffuse light from above. The jar had been standing under a
stream of water since the previous evening, and had been shaded from
light except that coming through the muslin cover. The prawns at
10.15 a.m., December 17th, 1898, were without exception in the vertical
(head down) position shown, and though the weed was brown in colour
they were of the most varied tints—green, purplish brown, red, and grey.

The brown variety of Hippolyte varians (mature speci-
mens) abounds amongst the masses of brown Halidrys

HIPPOLYTE VARIANS. 603

siliquosa which flourish in the ‘ Laminarian zone.” In
shape, colour, and occasionally in its attitude this form, as
Professor Herdman has pointed out, closely resembles the
Halidrys pods.

Young specimens of a uniform brown tint occur chiefly
among the fronds of Dictyota dichotoma (PI. 33, fig. 9).
Mature green prawns are somewhat rare at Piel, though
young ones are plentiful in the clear and shallow water of
the Zostera pools. Red, again, is not a tint commonly found
in full-grown Hippolyte varians at Piel, though a few
large and many small pink specimens were from time to
time discovered. Very probably the somewhat muddy
water, stunted weeds, and the comparative scarcity of clean
red weed are the causes of the rarity of this form. The
uniformity of their respective tints in these brown, green,
and pink prawns is on a closer examination less apparent.
The dorsal median line is generally marked by a white or
yellow stripe, and the sides of the carapace or of the whole
body may be spotted with minute blue dots, two of which,
just below and behind the orbit, are curiously constant.
Again, the terms brown, green, and pink cover a great
number of shades, from light chestnut to black-brown, light
green to olive, lake colour to mauve. It is, however, the
immature variegated specimens that present the most re-
markable cases of colour pattern and of resemblance to their
surroundings.

One of the commonest of these is the “red liner,” shown
in P]. 32, fig. 5, nestling amongst a tuft of weeds. The colora-
tion is striking, and differs from that of almost any adult
Hippolyte varians. A median dorsal and a median ven-
tral stripe run from end to end of the transparent body,
whilst each segment is crossed by a bar of minute yellow and
red spots. The eye-stalks, the inner edges of the antennal
scales, and the joints of the thoracic limbs are reddish, while
each tail lobe has an elliptical red mark with a clear centre.
The stomach and liver are visible through the carapace, and
appear slightly opaque greenish yellow. By reflected light

604 F. W. GAMBLE AND F. W. KEEBLE.

the body appears of a dull grey colour, the red marking
being much less distinct. Along the mid-dorsal line from
the rostrum backwards, spots of brilliant yellow or greenish
yellow, previously invisible, are now distinct. On parts of
the tail lobes, eye-stalks, and limbs, which appeared trans-
parent by transmitted light, similar bright yellow spots are
now to be seen.

We were able to follow the change in the coloration of
this variety for some little time. ‘“ Red liners” appear in
great numbers in July among the finer sorts of red weeds
in Piel Harbour. Many of them measured only 4 mm. in
length, but as they increase in size the red pigment accumu-
lates along the ventral stripe and the cross-bars; with this
accumulation these regions appear of a dark red or even
blackish colour. These “black liners” become fairly
common in September, much more so in December, when
some of them measured 15 mm. in length, and would now be
described as transparent, and boldly marked by black and
grey or dark purplish lines, the “ hump” or point of flexure
of the tail being nearly free from pigments. Were these
forms to increase considerably in size they would present an
appearance identical with that of Hippolyte fascigera,
whose characteristic habitat is the zoophyte-clad stems of
Halidrys siliquosa, and whose independent specific rank
is no longer maintained by such authorities as Dr. A. M.
Norman and A. O. Walker, Esq., F.L.S.

The occurrence of “‘ green liners,” a specimen of which is
shown in Pl. 32, fig. 2, in which the red colour is more or less
replaced by green in the stripes and bars, is not infrequent.
But in this case the data for the probable progress of sea-
sonal colour-change are not forthcoming. More striking than
these “liners” is the black-barred colour form, fig. 3,
which lives amongst the dark alga Cladostephus spon-
giosus. The body is transparent and crossed by two bands
of dark brown, almost black tint, a broad band across the
carapace and a narrower one near the base of the tail; not
infrequently a third band runs across the apices of the tail

HIPPOLYTE VARIANS. 605

lobes. Another variety (PI. 33, fig. 7), found amongst the
miniature forests of Bowerbankia, is speckled and barred
with light brown on a transparent ground, spotted with
bright yellow when seen against a dark ground. This
variety possesses, in summer, the plumose hairs on the
carapace and abdomen, supposed formerly to be a charac-
teristic of Hippolyte fascigera. In December, however,
these hairs are not usually present. Other colour forms
are seen in yellow and yellow-barred specimens ; in brown
prawns spotted with lighter markings; in the dark opaque
blue and the transparent, almost colourless or greyish forms,
the exact habitats of which have not yet been discovered.
Indeed, it may be said that the forms are infinite in variety ;
yet it would seem to us that a fuller description even than
that here given is very necessary before it can be deter-
mined with certainty whether any given form follows an
ordained colour sequence, whether change of surroundings
can permanently modify this sequence, problems which we
hope ultimately to resolve.

Hippolyte varians exhibits a certain sexual dimorphism
both with regard to size and to colour. This may be ex-
pressed by saying that the males are on the average much
smaller and less elaborately patterned than the females,
which are more resourceful in adjusting their coloration
to that of their surroundings. From the point of view of
“ protection,” this difference is only what might be expected
from the greater sluggishness of the female, burdened as she
almost invariably is with a load of eggs or developing larvee.

Section ITI.
“ Chromatophores” and other Colour Elements.

It has been observed in the preceding section that the
colours of the bands in red- and other lined Hippolyte
change according as transmitted or reflected light is used for
the examination. We now consider the pigments to which
these colours are due and the nature of the colour elements, the

VOL. 43, PART 4.—NEW SERIES. UU

606 F. W. GAMBLE AND F. W. KEEBLE.

repositories of these pigments, which matters appear to have
received hitherto curiously little attention. For the present
we shall regard the condition of a colour form as fixed, re-
serving the account of the chromatophoric changes effected
by light and other stimuli for Section IV.

If a red-lined variety is examined under a low-power
objective by light transmitted through an Abbé condenser,
the colours—except for the green or yellow patches formed
by the stomach and liver and for any food substances in the
intestine—are seen clearly to be due to masses of “ chro-
matophores.” The chitinous investment and the epidermis
being transparent and colourless allow the muscles,
alimentary tract, the gills, heart, and blood-vessels, to be
plainly perceived (Pl. 34, fig. 14). The median dorsal and
ventral stripes of red colour are due to masses of pigment
closely associated with the alimentary canal and nerve-cord
respectively, and require deep focussing for their satisfactory
definition; while the transverse bars which run across the
body near the hinder edge of each segment are composed of
red and yellow pigment spots placed nearer the surface of
the body, though it is easy to determine that they are not in,
but below the epidermis. Closer examination shows, in fact,
that the bodies of all the ‘ chromatophores” lie in the
connective tissue, and are definitely related to the digestive
system, and especially the “liver,” the vascular and muscular
systems (Pl. 34, figs. 14, 15, 19, and Pl. 35, fig. 23).

Thus, as the peristaltic waves of contraction pass along the
alimentary canal, scattered chromatophores move with the
walls of the gut, though for the most part the pigmented
sheath attached to the wall of the great intestinal venous
sinus (in which the blood is slowly travelling forwards to-
wards the heart) remains stationary. In a similar manner,
the ventral layer of ‘‘ chromatophores” surrounding the
nerve-cord is connected with the walls of the ventral blood-
sinus. The pigment spots forming the transverse bars lie
between the intermuscular arteries and venous spaces, and
are frequently closely attached to the walls of the arteries,

HIPPOLYTE VARIANS. 607

either to those of the segmentally arranged vessels supplying
the swimmerets and coming off in pairs from the dorsal aorta,
or to branches of these which divide in the connective
tissue under the skin of the pleura (PI. 34, figs. 14—16).

The best example of this close relation between the pig-
ment and the blood is seen in the eye-stalk (Pl. 34, figs. 17, 18).
Within the eye-stalk lie the optic ganglia enclosed in con-
nective tissue. Between the ganglia are the bodies of two or
more large dark red pigment spots, whose processes extend
right and left, at right angles to the narrower elongated
centres, in a peculiar paired fashion over the ganglia. The
blood is carried by an artery which runs near the surface of
the eye-stalk, and which, after bifurcating, divides into a large
number of branches interdigitating with the pigmented pro-
cesses of the “chromatophores”’ (Pl. 34, figs. 18, 19).

Previous observers of these Crustacea do not appear to have
noticed the abundant store of chromatophoric pigment which
exists in the muscles of Hippolyte, especially in the ex-
tensors and flexors of the tail. In these positions the
‘**chromatophores”’ are so abundant that if, for example, a
piece of muscle is cut out of a pink prawn, the muscle itself
is seen to be pink, and under the microscope the arrangement
of the pigment is similar to that of Pl. 34, fig.20. The trans-
parent or semi-transparent specimens of Hippolyte (par-
ticularly the immature and male examples) owe such colour
or pattern as they possess more to these “ muscle-chromato-
phores” than to the dermal ones underlying the skin. In
larger and more opaque forms the colour is determined
rather by a superficial network formed by the dermal
“chromatophores,” which thus hide the (often similarly
coloured) intermuscular ones (Pl. 35, fig. 24).

The presence of pigment distributed in “ chromatophores ”
among the muscles is by no means peculiar to Hippolyte
varians. In the true prawns (Palemon serratus) the
stripes of colour are due to superficial “ chromatophores” in
the skin, each containing red and yellow pigment surrounded
by a little blue. In the depths of the tail muscles there is

608 F. W. GAMBLE AND F. W. KEEBLE.

a store of (chiefly) blue pigment, which takes no part in the
superficial coloration of the animal.

We turn now to the detailed examination of the “ chroma-
tophores” themselves, and for the purpose we select a pig-
ment spot from one of the transverse bars on the abdomen.
Occasionally such a spot or “chromatophore”’ has a distinct
central “body” from which run branching and anastomos-
ing processes; more usually (Pl. 34, fig. 19) there are two
densely coloured and ill-defined central portions of a red
colour by transmitted light. The processes are either red or
yellow, finely branched, and, in places, continuous with those
of adjacent “chromatophores.” By means of a high power
the processes are seen to be tubes with a distinct wall, a
feature most readily ascertained when the pigment has
broken down into small globules separated by clear spaces.
We have repeated this observation on a great number of
“chromatophores” from different colour varieties, and
though the finer arterial branches resemble chromatophoric
processes free from pigment, the large blood-corpuscles in
the arteries and the indubitable presence of pigment granules
in the intact processes readily serve to distinguish these
structures. In fact, with practice, the translucent, branched
tubes can be seen radiating from a ‘‘ chromatophore”’ whose
pigment is retracted into the central “body.” The “chro-
matophore” is a structure whose outline is fixed,—that is to
say, the processes are limited by a definite membrane.
Colour-changes in the animal are caused by movements of
the pigment within the chromatophores, movements which
may be modified by nervous impulses, but of the nature and
origin of which we know nothing.

Summarising the more striking features of these colour
elements in a red-lined Hippolyte varians, we may point to
the presence of red and yellow pigment (and to anticipate,
we may add blue) in the same “chromatophore ;” the close
relation of these colour elements to certain organs, and par-
ticularly to the vascular system; the tubular nature of the
processes and flowing movement of the pigments; and the

HIPPOLYTE VARIANS. 609

fusion of the branches of one chromatophore with those of
others. On one point, the histological character of these
colour elements, our evidence is incomplete. We have not
been able to demonstrate that the pigment spots or “ chro-
matophores” are “cells.” In most cases the pigment
appears to be stored in connective-tissue lacune. On the
other hand, the flowing movement of the pigment to and
from a “centre” seems only explicable on the view that
these bodies are really cellular. We may point to the
recent work by Holmgren and Schreiber on the crayfish and
prawn for evidence on this head.

Holmgren has shown (1898, p. 409) that in the prawn
(Paleemon) the chromatophores are nucleated connective-
tissue cells the processes of which are frequently confluent.
Both authors describe a peripheral nerve-plexus in close con-
nection with the colour elements and the ordinary nerve-trunks.

So far we have dealt only with the most prevalent kind of
“chromatophores,” but there is another element to which we
must briefly refer. At the bases of abdominal pleura, along
the mid-dorsal line, on the eye-stalks, and in few other
positions a colour element occurs which possesses fine branches
radiating from a well-marked central body. By transmitted
light these spots are almost invisible to the naked eye, whilst
under the microscope they look yellowish or dull greyish
green. By reflected light they are brilliant yellow, more
brilliant indeed than the yellow of the ordinary chromato-
phores. ‘hey are filled with minute granules (often 1 u in
diameter), together with a small amount of homogeneous
yellow pigment. Similar colour elements are of constant
occurrence in allied Crustacea.

Leaving the red-lined variety and turning to the brown
colour form of Hippolyte varians, we encounter an arrange-
ment different from that just described. Under the micro-
scope the colour is seen to be due to a dense red network
enmeshing the clear cells of the epidermis, and blotched here
and there by green patches (PI. 35, fig. 24). Some patches,
bolder than the rest, seem to indicate the position of the

610 F. W. GAMBLE AND F. W. KEEBLE.

centres or bodies of the “chromatophores.” The network is
continuous from one end of the body to the other, and from
the right side to the left. By the aid of the microscope the
green patches can be resolved into yellow and blue pigments
lying in the same! processes: in other parts of the reticu-
lum yellow pigment may be seen close to the red. The
brown colour, in fact, is due to the superficial processes of
“chromatophores,” the bodies of which lie in the subjacent
connective tissue and give off other deep intermuscular pro-
cesses, which are only revealed after the removal of pieces of
the integument. The red pigment is fully expanded, the
yellow considerably less, and the blue very slightly.

This blue pigment, which we here encounter for the first
time, is treated at some length in the section on Nocturnal
Coloration (Section V, p. 622), and we need say little about it
here, as it plays a much less important part as a rule in deter-
mining the tint of the prawn during the day than the red or
yellow. Whether, like these, it pre-exists stored up in the
centre of the “chromatophores,” or can be, under suitable con-
ditions, rapidly manufactured out of the red or yellow pigment,
or whether both these alternatives contain something of the
truth, we have not determined. Till our knowledge of the
chemical nature of the pigments—presumably lipochromes—
is extended in the way which Maly (1881) and Newbigin
(1897) have indicated, these questions must be left open.

To return to our description of the pigment bodies in the
brown varieties of Hippolyte. In addition to the “ chro-
matophores”’ just described, blue spots in the sides of the
body, often visible to the naked eye, are of frequent but not
of constant occurrence (Pl. 35, fig. 21).

These blue spots occur in other colour forms of Hippolyte
—for example, in green and variegated brown specimens,—
and the same description will apply to most cases. In form
and in size they are most variable. They may be spherical,
almost black by transmitted light, and provided with a few
short lighter coloured processes, or they may be elongated,

! Or in closely apposed ones.

HIPPOLYTE VARIANS. 611

half a millimetre in length, and delicately plumose. The
commonest form, perhaps, is that of an irregular blue net-
work somewhat elliptical in outline (Pl. 35, figs. 22, 25).
The marginal strands of the network fray out into thinner,
lighter coloured processes ; the central strands are thick, and
enclose in their meshes a transparent substance. By reflected
light the blue spots are pale opaque blue, by transmitted light
nearly black.

A remarkable feature of these blue spots is that they
are very generally separated, optically at least, from the
surrounding chromatophoric network by a clear enclosing
space. Not entirely, however, for across this clear halo there
extend fine greenish-yellow or bluish radiations, continuous on
the one hand with the frayed-out marginal strands just re-
ferred to, and on the other with the surrounding “ chromato-
phores.” Usually two or more of these radiations are stouter
than the rest and more obviously continuous with the ad-
jacent network.'! They differ, too, not only in being stouter,
but also in the character of the pigment which they contain ;
for by day they contain red pigment and join the red net-
work we have described, whereas at night they contain blue
pigment. We refer to this matter, which belongs to the
next section, for the purpose of showing that the red pigment
must either be concealed by the thick blue granular pigment
at the centre of the “ blue spots,” or that the blue must be
replaced by red radiations formed out of this pigment.

We will now briefly discuss the green and pink colour
forms. Specimens emerald green to the eye, examined by
light transmitted through an Abbé condenser, appear much
paler and yellower in colour; while by reflected light the
green assumes a dull dark tone. The body of the prawn is
transparent enough to allow the spherical, clearly defined,
almost black centres of the ‘ chromatophores,” and the deli-
cate close yellow network formed by their processes, to be
clearly seen. The black centres have a faint bluish or green-
ish halo, and under the high power a delicate blue reticulum

d 1 Pl, 35, fig. 25.

612 F. W. GAMBLE AND F. W. KEEBLE.

can be seen all over the body of the “ chromatophore,” but
particularly clearly at the margins of the “blue spots.” It
is the close association of the yellow and blue network—
perhaps in some regions the two pigments actually form parts
of one reticulum—that causes the green colour.

We saw, in dealing with the brown Hippolyte, that it
was the network alone which gave rise to the colour of the
animal, the greater mass of the pigment of “chromatophores”
playing no part in the naked-eye colour, being, indeed, con-
cealed by the surface colour. Here, inthe green variety, the
same is largely the case, the finer branches and the super-
ficial branches of the colour elements alone give rise to the
gross colour.

In the brown colour form, red is fully expanded, yellow
slightly, and blue least of all; in the green variety, yellow
and blue are fully extruded, while the red is so densely
retracted as to have the appearance of spherical black dots.
To complete the comparison, take the case of a pink specimen,
the nearest approach to a red variety which the neighbour-
hood of Piel or of St. Vaast permits. Here the ‘‘ chromato-
phores” are large, moderately expanded, that is to say,
the red pigment exists in a coarse network (PI. 35, fig. 25),
while, except for the “‘ blue spots,” the blue and yellow are
absent or invisible.

The general conclusion, which must be of great use in future
examination, may be noted: that the colour of the network
defines the gross colour of the animal; and that, in any form,
great stores of pigment, more or less concealed by the net-
work, exist in the intermuscular “ chromatophores.”

Section IV.
Colour Mutability of Hippolyte varians.

We have seen that the young specimens of Hippolyte
varians often exhibit colorations distinct from that of adults,
and we have shown that the patterns of the variegated forms
and the tints of the uniformly coloured specimens are deter-

HIPPOLYTE VARIANS. 613

mined by the mode of distribution of the ‘‘ chromatophores,”
and by the relative degrees of expansion of their contained
pigments. We have described some of the more prevalent
colour forms, without more than incidental reference to their
possibilities of colour-change.

That Hippolyte varians is to some extent capable of
colour-change is well known (see Kinahan, 1857 ; Herdman,
1892, etc.), so that what we have described as different colour
forms are in reality but the most stable phases in animals
undergoing a series of colour-changes. We have now to dis-
cover the extent of these changes in each case, the conditions
under which they occur, and in what way change in condi-
tions affects the redistribution or other modifications of the
pigments of the ‘‘ chromatophores.”

Harlier observers have attributed change of colour to change
in the nature of the ground over which the animal is passing,
to its change of habitat from one coloured weed to another,
and also to a limited extent, in captivity (Pouchet, Malard),
to change in illumination.

When we remember that such classical problems as the
causes of colour-change in the frog and the chameleon have
only been quite recently thoroughly reinvestigated—that of
the frog by Professor Biedermann (1892), of the chameleon by
Dr. Keller (1895)—we shall not be surprised that uncertainty
should still exist as to the nature of the stimuli which modify
the coloration of these prawns. Professors Biedermann and
Keller have shown that colour-change in the frog and the
chameleon is produced not by light only, but also by contact
of the toes with different substrata, by variations in tem-
perature, and by changes in the amount of oxygen available
for tissue respiration. These external changes are all
effective in exerting a certain nervous activity which is mani-
fested by change of colour. We are still engaged in
endeavouring to unravel the tangled skein of causes in the
case of colour-change of Hippolyte; as yet the only factor
the influence of which on colour-change we have investigated
with any fulnessis ight. In this section, therefore, we shall

614 F. W. GAMBLE AND F. W. KEEBLE.

confine ourselves to the consideration of light as a stimulus
to colour-change.

Effect of Colour of Weeds on Colour-change in
Hippolyte.1—In this section and in the tables appended to
it we give some of the evidence we have obtained showing
that by replacing weed of one colour by that of another, a
sympathetic colour-change may manifest itself in the prawns,
though this certainly takes place to a less marked degree
and more slowly than we had been led to anticipate. The
experiments were made either in our “air-circulator”’ vessels
or in dishes placed in the garden of the Piel Laboratory in
full light. The colours in the record are those of the prawns
as seen when placed, detached from their weeds, in a white
porcelain dish, proper precautions being taken to minimise
the ill effects of these artificial conditions. We deal here
only with the diurnal colours.

In case the records of these experiments, which we feel
should be given at some length, are too tedious to be read
by those not engaged in colour work, we preface them with
the following summary.

Adult prawns when placed with weed of a new cclour (the
light intensity being as far as possible unaltered) are, under
the conditions of the laboratory, only capable of very slow
sympathetic colour-changes. Thus green Hippolyte placed
on brown weed conserve this green colour even for a week
or more, but in the end give way and become brown. Their
subsequent recovery when placed with green weed is more
rapid. We have repeated such experiments in the open, time
after time, and have found that the prawns were either quite
refractory or responded in this slow manner.

Two greenish-brown, large female prawns are fully recorded
in Table III, p. 670. They were taken from a number captured
on July 26th, 1898, and were placed on the 28th ina glass jar
with Zostera (green weed). A muslin cover was tied over
the jar, through which a strong current of water was main-
tained. From the table it will be seen that the animals re-

1 See Tables I—IV, pp. 660—672, and Summary, p. 651.

HIPPOLYTE VARIANS, 615

mained during the first three days of an olive-green colour,
but became more transparent. It was only at midday on
the 30th, after having been for about fourteen hours in
the dark, that a distinct green colour manifested itself.
This green colour persisted in the light, and changed on the
31st toa greenish yellow, matching the lower parts of the
Zostera stalks.

The change in this case from olive-green to bright emerald
green, accompanied by an enhanced transparency, is not
very great ; but the close agreement of the colour with that
of the weed is striking.

We have also other records of brown prawns becoming
green on green weeds. ‘Thus three adult and three small
prawns taken the day before (July 27th) were placed (on
July 28th) in a “ water-circulator” dish containing Ulva
and other finer green weed, and exposed to diffuse light.
One of the adults, a dark “fascigera” mottled with grey,
underwent no change during the experiment, which lasted
till August Ist. A second adult became of a lighter brown
colour, developed a temporary green tint, but became brown
again on July 31st, on which day it died. The remaining
adult became dark green on the 29th. Of the three small
prawns two had become bright green by the 29th.

The opposite change from green to brown is well shown in
the case of Prawn d in Flask B (Table II, p. 662). On July
22nd this green specimen was placed with brown weed, and
on the 25th, after being exposed to alternate diffuse light and
darkness, was the same tint as the finer brown weed.

A fourth example of our experiments on the influence of the
colour of the weed on colour-change of Hippolyte may be
given, viz. the effect of red weed (Delesseria) on green
prawns (Table IV, p. 672). The microscopic appearances of
two green specimens were noted (August 8th). The prawns
were then placed with the red weed in a “ water-circulator ”’
jar in the open. The experiment began at 12.30 in bright
sunlight, but after half an hour the weather became dull and
cloudy. At 4 p.m. one prawn had become of a clear brown

616 F. W. GAMBLE AND F. W. KEEBLE.

colour. On microscopic examination the red pigment, which
had before been retracted, was now fully expanded, the yellow
more retracted. The other specimen was dull green, but had
emitted some red pigment. The change was in the direction
of a red tint. The failure to assume it may be connected with
the fact that this red colour is associated with an absence
of yellow, whilst the green prawn possesses much pigment of
this colour.

The four experiments which may be taken as typical of a
large number (pp. 658—669) show that a certain sympathetic
change of colour is possible, but that the range of colour muta-
tion accompanying change in the colour of the weed is not
great, and that the rate of change is generally veryslow. With
some forms, notably the small Hippolyte varians, which
are always of a bright green tint when living in shallow
water amongst the leaf-like branches of Zostera, little or
no colour-change attends their transference to weed of
another colour. Indeed, in a batch of prawns of any colour
there are always a considerable proportion which are un-
affected by such changes.

We must now return to the first of the three experiments
just given, to consider the apparently astonishing result that
a sympathetic change of colour from brown to green takes
place in the dark.

In endeavouring to account for this sympathetic change
occurring in the dark, two facts must be borne in mind, for
in all probability at least two factors are involved. In the
first place, light is not the only efficient stimulus to colour-
change, as we demonstrate in Section VII; and in the second
place the greening of the brown Hippolyte is attributable,
at least in part, to an after effect of the light-stimulus.

During the night the particular trend of nervous activity
which had determined the diurnal colour, in combination
with external conditions, is suspended. The animal during
the night assumes an entirely different hue, of which we
speak later. On the succeeding day, even though light be
excluded, the animal resumes its nervous way, takes up its

HIPPOLYTE VARIANS. 617

chromatophoric habit at the point where, being overtaken by
night, it had been compelled to leave it at the close of the
previous day. That this is so we prove in the section on
Nocturnal Colour. We suggest that a change owing to
change of weed, for example, which may not have had time
to express itself before nightfall on the previous day, may
make its appearance as a modification of colour on the day
ensuing. The argument may seem extravagant, though less
so, we think, than the fact, and less, too, when the section
on Nocturnal Colour has been perused.

Effect of Change in Light Intensity.—Though the
prawns offer no quick change of colour in response to colour-
change in their weed, preferring ordinarily to change their
habitat rather than their habit, they offer a series of re-
markable colour responses to well-marked changes in light
intensity or light distribution. Professor Herdman has sug-
gested that the lack of sympathetic colour-change in response
to change of colour of the accompanying weed is attributable,
at all events in part, to the dulness of light conditions at
Piel. The facts with which we now deal seem, however, to
point away from that suggestion.

The following observations indicate the pronounced nature
of the colour-change which alteration of illumination induces
in Hippolyte varians. The specimens, taken (August
15th, between 4 and 6 p.m.) from the trawl or bottom
tow-net, were at once divided into four lots, each lot con-
taining representatives of the various forms obtained. These
four lots were disposed as follows (Table V, pp. 674—676) :—
(A) in clear glass jar left standing open on deck, (B) ina
glass jar covered with fine muslin, (C) in a white porcelain
jar with muslin cover, (D) in a blackened jar with black
cover. The jars A, B, C, D all contained fresh sea water
but no weed. After an hour the specimens in B (glass jar
with muslin cover), and especially in C (porcelain jar muslin
covered), were found to have undergone a marked change,
whilst those in A (clear glass jar) and in D (dark) were prac-
tically unaltered. We have repeatedly tried the experiment

618 F. W. GAMBLE AND F. W. KEEBLE.

in the afternoon and early evenings of August, 1898, and
always with the same general result. The change in B
(muslined jar) and in C (porcelain jar), no matter what forms
are contained therein, is in the direction of green or blue.
All transitions towards these colours are found, including
some so completely modified as to appear of a bright trans-
parent azure blue. Speaking chromatophorically, the effect
of a short sojourn of the prawns in these jars is a general
retraction of the red pigment, and a slight expansion of the
blue accompanied by increase in transparency. Brown
specimens become green; “ black-barred,” greenish-barred ;
“‘red-liners,” green-lined; and pink, mauve. If these speci-
mens are kept in muslined flasks, or in white jars with muslin
covers, under a good circulation, and supplied with food in
the shape of small pieces of weed or dead Crustacea, the
diurnal coloration remains green or bluish according as the
specimens contain much or little yellow pigment. Whereas
if, under the same conditions, a quantity of weed of one or
more colours is introduced, the red pigment is extruded ;
bluish-lined and barred prawns becoming black-lined and
black-barred, and some green ones turning brown.

The greening effect is also well shown by a short exposure
of Hippolyte varians of different tints in a white porce-
lain dish either to diffuse light, or—in which case the result is
more marked—to sunlight or incandescent light. The change
is very rapid, a few minutes’ exposure being sufficient to induce
the green or blue effect. Some of the evidence for this is given
on Table VI (Light Intensity, Expt. 2), where the chromato-
phoric changes are also recorded. Five brown prawns were
chosen. They were placed, one (E) in a black jar; another
(F) exposed to sunlight in a glass dish on a black plate; a
third (I) in glass jar half filled with dark grey sand ; and the
two remaining prawns (G and H) in a white porcelain dish.
The experiment was begun in the garden at 12.30, in cloudy
weather with occasional gleams of sun. At 2.30 Gand H
had lost most of their brown colour and had become greenish,
G particularly; I was altered to a darker brown; F was

HIPPOLYTE VARIANS. 619

unchanged, and EH had gained transparency and a slight
green tint in the middle of the body, but was otherwise un-
altered. Hxamination showed that in the two (G and H)
which were green the effect was due to retraction of the red
and extrusion of the blue, which with the yellow already out
gave the green tint. These two (G and H) were now put
into the jar standing on the black plate, and at 4.50 and 7.5 p.m.
were full dark brown; while E and F were transferred to
the porcelain dish, and at 4.50 were greenish brown.

Thus we see that alterations of light intensity and of the
distribution of light act as powerful stimuli to colour-changes ;
that light of low intensity scattered evenly from the surface
of the vessel produces a retraction of the red pigment and an
evolution of the blue (possibly also of the yellow) —in other
words, a green colour—during the hours of daylight; that
light of low intensity, either absorbed by the walls of the
vessel or unequally scattered over its interior, effects the full
expansion of the red pigment, and to a less extent extrusion
of the yellow.

Hippolyte avoid high hght intensity by creeping under
the shadow of the dish. It is noteworthy that when, how-
ever, they are compelled to submit to it—placed, for example,
in a porcelain dish in the open—the high light intensity pro-
duces a green effect; whilst if the prawns be similarly ex-
posed, but in a dish with a background which absorbs the
light, the red is maintained fully expanded, or retracts but
gradually.

Effect of Monochromatic Light.—Having ascer-
tained that the distribution of a pigment in the “ chromato-
phores” of Hippolyte varians is profoundly influenced by
the quantity of hight, we next endeavoured to determine
whether the quality of the light to which the prawns were
exposed exerted any similar effect. For this purpose we
employed the Landolt ‘ Strahlenfilter” already described.
As sources of illumination we used, in some cases, diffuse
light, in others incandescent gas-light, and again in others
bright sunlight. The colour-screens do not transmit abso-

620 F, W. GAMBLE AND F. W. KEEBLE.

lutely pure monochromatic light, but the quantity of light
other than that of the colour desired is not considerable, and
has been accurately determined by Landolt.

In none of our experiments did we obtain evidence that the
coloured light exerts, by virtue of its quality, any positive
influence on the diurnal conditions of the pigments. Hven
when bright light of high intensity was reflected on to the
filters by means of mirrors, the results were exactly those
which we obtain by subjecting the animals to very dim hght
or darkness. The prawns exposed to approximately pure
red or blue light rapidly became of their nocturnal colour
(Sect. V). Green light has, however, less effect.

Table VI, p. 678, gives the result of experiments with differ-
ent coloured lights compared with those made by varying
the light intensity. Specimen A, a light brown Hippolyte,
in which the red and yellow pigments were well expanded,
was put at 12.20 under a red colour-screen, through which
daylight was transmitted. - At 1.5 the pigmentary condition
had become entirely altered. The red and yellow were
retracted and replaced by blue. As far as the colour was
concerned the prawn was now a “nocturne” (as we explain
in the next section). The same change occurred in another
specimen (D) placedin blue ight. Those in the green light
' (B and C) had up to 1.5 shown no change; while the brown
prawns (Gand H) in white porcelain dish had become green,
and one on grey-black sand (I) from brown had changed to
an even darker tint. At 2.30 G and H were transferred
toa glass jar standing on a black plate, where they became
and remained dark brown. At 7.5 p.m. all the prawns in
the coloured lights were blue (“nocturnes”’), those in the
porcelain dishes were greenish, and the others, on the black
surface, brown. Our other experiments confirm this result,
that coloured lights, if they produce any effect, cause a
retraction of the red and yellow pigment and expansion of
the blue, accompanied by increased transparency; in fact,
the result is the blue colour normally induced by the darkness
of night (see Summary of Experiments on p. 652).

HIPPOLYTE VARIANS. 621

It might be thought that this surprising result is due to
the “light filters” transmitting a very feeble light, practi-
cally only equivalent to dimness. We have endeavoured by
the use of incandescent light and reflectors to bring the
coloured light up to a high degree of intensity, and the results
are the same as when daylight is employed.

We conclude, then, that whereas light-intensity plays a
considerable part in determining the colour patterns, the
quality of light has no effect; a conclusion which harmonises
with that derived from our observations on the small effect
of different coloured weeds in modifying the colour. It seems,
then, that this small and very slowly effected change is in all
probability due to response to the different intensities of the
light reflected from the differently coloured surfaces of the
red, green, or brown weeds.

A possibility, however, remains—that the quality of light
may exert a directive effect on Hippolyte; may, failing to
cause it to change its spots, cause it to change its position.
Though we have endeavoured to obtain evidence as to the
truth of this conjecture we have not yet succeeded. So far
as our experiments have yet proceeded we find that, though
the possession of a “colour sense” has been ascribed to so
lowly a Crustacean as Daphnia, we have no need, even
though we had the desire, to make a similar demand on
behalf of Hippolyte varians. We may, therefore, refrain
from discussing what exactly the term ‘‘ colour sense’ would
imply with respect to a Crustacean.

Conclusion.—Hippolyte varians is a parasite on sea-
weeds and zoophytes. On these it finds both food and shelter.
Its prime object in life is to anchor itself. Once fixed, rather
than release its hold it will allow the ebb-tide to leave it
stranded. By its immobility it has grown into its surround-
ings and become coloured like them. Should it be forcibly
separated from its favourite weed its movements become of an
aimless sort. Its nervous system is thrown out of gear, so that
it does not, at least for a time, exhibit the phytotaxic irritability
which we believe it (for reasons given on p. 594) to possess.

VoL, 438, PART 4,—NEW SERIES, xx

622 F. W. GAMBLE AND F. W. KEEBLE.

Hippolyte exhibits marked sensitiveness to changes of
light-intensity, but offers no rapid positive response to light
in virtue of its colour. At least three kinds of colour-change
must be distinguished. First, the slow sympathetic colour-
change which accompanies a change in the colour of its weed.
Second, the rapid changes produced by altering the light
intensity. Third, a periodic habit of changing from the
motley of the daytime to blue at night. We deal with this
habit in the next section.

Section V.
Nocturnal Colour.—Nocturnes.

Hippolyte varians, living in the so-called “ Lami-
narian zone,” is subject, owing to tidal movements, twice
every twenty-four hours to change in illumination. At high
tide, the animals may be living in comparative obscurity
beneath twenty feet of muddy water ; whereas later in the day,
in the season of spring-tides at all events, the prawns may be
exposed in shallow pools to fulldaylight. Since Hippolyte
seems not to wander far from its food-plants, and since,
moreover, as we have shown, it is very sensitive to change
in light-intensity, there will doubtless be daily changes of
coloration in the prawns in response to these periodic altera-
tions in light. We find, in fact, that at very low spring-
tides in summer, which always ebb about 6 a.m. and 6 p.m.,
prawns from the Halidrys beds are of a lighter tint than
those trawled from the same spot in several feet of water. A
careful study of colour-changes of the littoral fauna would
probably bring to light many cases showing response to
recurring alterations in illumination.

A much more important colour-change than that which we
have just recorded is effected by the daily alternations of
light and darkness. Every evening, as darkness comes on,
Hippolyte gradually loses its distinctive diurnal colour. In
summer the change begins about 9 p.m., in winter at about
5 p.m. Toward this or that time, according to the season, a

HIPPOLYTE VARIANS. 6238

reddish tint—a sunset glow—the foreshadowing of the
change, makes its appearance. This is followed by a green
tinge which spreads fore and aft from the middle of the body.
The green colour gradually melts into blue, and a general
increase of transparency sets in. Thus, as darkness falls,
Hippolyte is seen to become of a wonderful azure blue
colour and absolutely transparent, except in the region of the
liver and stomach, which are now very clearly visible. The
depth of the blue colour varies in different specimens ; in
some it is almost indigo, in others the faint azure of a sky at
sunset (Pl. 33, figs. 10, 11).

During August or September specimens of Hippolyte in
the laboratory or tankroom undergo this change in one and a
half to two hours, during December in about one hour.

Prawns in this nightly condition, exhibiting a deep yet
transparent blue colour, we propose to call nocturnes; those
which become more transparent, greyish or almost colourless,
“orey” or “colourless” nocturnes. The term semi-
nocturne may be used to designate the antecedent phase
during which the animal is green and semi-transparent.

We give a few cases to illustrate the change. A “red
liner ” (fig. 14) becomes green-lined in twilight: and in dark-
ness, faintly blue-lined on a highly transparent ground. Ina
“ black-barred ” specimen (Pl. 33, figs. 12, 13) the transverse
markings become deep blue, standing out boldly against the
transparent intervals. Dark brown forms become bluish
green and ultimately deep transparent blue. Red specimens
become first mauve, then colourless or bluish. Green forms
pass quickly into the blue nocturnal condition.

To show that this nocturnal change occurs in Hippolyte
living under natural conditions we give the following extracts
from our diary :

I. August 20th, 1898. Dredged with strong tow-nets over
the Halidrys bed at Piel, 9 to 9.30 p.m. Tide low, night
dark but clear. Result :—All Hippolyte were nocturnes
when examined at the moment of capture by the light of
lamps carried in the boat. During the return trip they were

624 F. W. GAMBLE AND F. W. KEEBLE.

exposed to this light, and many recovered to their diurnal
tints, but several were still quite blue and transparent when
recorded again in a white porcelain dish in the laboratory.

II. November 22nd, 1898. Mr. Andrew Scott (Curator
of the Piel Laboratory), working during a very low tide on an
exposed bank called the “Scar” at 5.30 a.m., observed that
the prawns in the tide-pools were brown, green, and pink.
The morning though dark was starlight; the moon, being in
her first quarter, shed little ight.

III. December 15th, 1898. On the Scar from 6 to 7.30
p.m. Very low ebb. Night clear, calm, and starlight. The
‘Hippolyte collected in the pools consisted of nocturnes and
“ diurnes”’ in about equal proportions, while those trawled in
two feet or so of water on the outer side of the bank were all
full nocturnes.

IV. December 16th, 1898. On the Scar by 6.30 a.m.
Very dark thick weather, calm with misty rain. Poor ebb,
only a small portion of the bank showing above water. All
specimens obtained by hand-nets in the pools and among the
weeds were nocturnes (some transparent and colourless).
Dawn commenced about 7, and by this time some of the
Hippolyte showed partial recovery to their diurnal tints.
As it grew lighter the proportion of these increased, until at
7.30 to 7.45 none but fully recovered specimens were to be
found.

These facts establish the conclusions that the transparent
and usually blue nocturnal condition of Hippolyte varians
is due to a normal and nightly change, that the change
occurs while the prawns are still on their beds of weed, -that
the twilight before daybreak may be sufficient to induce a
recovery of the diurnal colour in prawns occurring close to
the surface of the water, and that the recovery is usually to be
associated with the dawn, and gradually affects those indi-
viduals which may be a few feet below the surface.

Hippolyte varians is not the only Crustacean in which
we have discovered such a nocturnal change. In the same
hauls which contained several nocturnes of this prawn we have

HIPPOLYTE VARIANS. 625

frequently obtained specimens of Mysis (Macromysis
neglectus and M. inermis’) of a transparent bluish-green
colour, and other Mysidee of a highly transparent, colourless
appearance, which recovered to a more or less pronounced
brown colour on exposure to light. Pandalus annuli-
cornis, which varies in colour during the day between green
and red, exhibits a transparent and colourless (or slightly
yellowish) nocturnal aspect. Other species of Hippolyte
(H.spinus and H. pusiola), brightly coloured by day, have
a faint bluish and very transparent nocturnal coloration.
We are not aware that this recurring colour-change at night
has been previously described in any Crustacea, but the
observations made by Verrill on several species of fish
(1897) show that they exhibit, when asleep at night, a colour
and position very different from the tints and attitudes
which they manifest during the day.

On bringing a number of nocturnes of Hippolyte
varians into the light, or on flashing a lighted magnesium
ribbon over a dish containing them, the prawns recoil from
the light with a sudden and violent start, and swim actively
about. When rapidly examined under the microscope by
incandescent gas-light their “chromatophores” undergo
such speedy change, that in a minute or less the transparency
has gone and the diurnal colour returned. In winter,
however, the change is generally much slower, so that it is
possible to examine them even with high powers and to
discover the source of the blue colour. The transparency of
the body is wonderful, and, as Professsor Sars found in 1867
to be the case with Mysis, greatly facilitates the study of
their anatomy. ‘The outlines of the individual strands of
muscle, the connective-tissue networks and bridles, the
muscles of the heart and its ostia, the arteries and their
branches, with the blood-corpuscles swiftly flowing along them
and returning more leisurely by the veins, the gills, the
alimentary canal, the nerve-cord, the optic ganglia, can all

1 We are indebted to A. O. Walker, Esq., F.L.S., and W. I. Beaumont,
Esq., for their kind aid in the identification of these Crustacea.

626 F. W. GAMBLE AND F. W. KEEBLE.

be seen, but as though immersed in a clear blue stain. The
“chromatophores” are reduced to shrunken blobs of a
blackish colour, distributed under the alimentary canal,
along the nerve-cord, on the optic stalks, and scattered
through the connective-tissue networks. The ‘ chromato-
phores” are separated from one another by comparatively wide
spaces, and are each surrounded by a delicate blue halo; a
most delicate and intricate blue reticulum connects these
halos one with another. It is this reticulum which gives the
blue tint to the nocturne. The blue network is strongly,
perhaps chiefly, developed in the muscles. The excised
muscle of anocturne is of a brilliant blue colour. In speaking
of the prawns as seen in the daytime, we alluded to the
stores of chromatophoric pigment which occur in the muscles.
In some specimens of a faint blue colour to the naked eye,
the blue tint becomes invisible when viewed by the powerful
light concentrated by a sub-stage condenser, and in all cases
the tint appears much less vivid under a microscope than to
the unaided eye.

The result of a large number of observations on the
‘‘chromatophores ” of nocturnes shows that the red and
yellow pigments are fully retracted, forming irregular
blackish masses. By reflected hight the centre of each
“chromatophore”’ shows as a dark red mass with lighter
yellow patches, the whole enveloped in a blue pigment (PI.
36, figs. 33, 34).

In some specimens strong reflected light reveals peculiar
coloured vacuoles at the “centres.” ‘The nature of these
“vacuoles”? we have not investigated.

During the examination the blue colour fades away from the
reticulum very quickly, and becomes concentrated round the
centres. The colourless branches of the ‘‘ chromatophores ”
may now be seen as the yellow and then the red pigments
flow outwards into them (Pl. 386, fig. 33). By reflected light
the “ chromatophores ” now look green, with a bluer margin.
The further succession of events is difficult to record, as
several rapid changes take place simultaneously ; but it is

HIPPOLYTE VARIANS. 627

worth while noting that the “blue spots,” plainly visible
during the height of the nocturnal phase, are during this
period clearly continuous with the general blue reticulum,
being connected therewith by branches which radiate from
the centres of the blue spots across their clear surrounding
“halos.” As the recovery to the diurnal tint progresses,
these branches become red and join the now red network.

The blue substance has the homogeneous appearance of a
pigment in solution. It takes but a limited share in the
coloration of the prawn during the day. The ventral denser
sheath of “chromatophores” and, in many specimens, the
thoracic limbs are the portions in which it chiefly persists
in the diurnal phase. It is interesting to note in connection
with the general lower light-intensity during the winter, that
more blue is observed in the same colour varieties of Hippo-
lyte varians during December than in July and August.
Whether, however, all the blue of a nocturne consists of
pigment extruded from the “chromatophoric” centres in
which it is stored during the day: or whether there is an
actual transformation of one or all the other pigments into
blue, are difficult questions. Extracts of five brown specimens
and of five brown ones in the full nocturnal phase in equal
quantities of 90 per cent. alcohol gave approximately simi-
larly coloured (red) solutions. This tends, as far as it goes,
to show that the red and yellow pigments are not metamor-
phosed. But more suggestive of a similar conclusion are
Hxps. 1 and 2, Tables I and II, showing that the nocturne
may pass in a remarkably short space of time over into the
diurnal phase and back again to the nocturnal one. We have
nothing, however, to say here concerning the difficult matter
of the origin and relations of the pigments, though we hope
subsequently to follow up this as well as some of the many
other lines of investigation to which these colour-phenomena
point (see Newbigin, 1897, 1898, and authorities quoted).

So far we have dealt with the natural nocturnal colour in-
duced by darkness. We must now consider certain means by
which the assumption of the nocturnal phase may be hastened

628 F. W. GAMBLE AND F. W. KEEBLE.

and the recovery from it postponed. In the previous sections
we proved the sensitiveness of Hippolyte varians to
changes of light-intensity. By exposing prawns in muslined
or porcelain jars, or in white dishes, to bright light in the
open or to incandescent gas-light, a change of colour to green
was shown to be induced. We can now show that by con-
tinuing the experiments on freshly caught specimens till
evening, the green colour deepens into the blue nocturne
phase. In fact, the readiest mode of inducing the nocturnal
condition is to place some prawns in a white jar, to cover the
jars with muslin, and to add only a scrap or two of weed
to serve as food. Placed under a current of water the
specimens assume the nocturnal hue fully an hour or more
before others in clear glass vessels. The following morning,
at an hour when other prawns freely exposed to diffuse
light have fully recovered, some of those in muslined jars
are still nocturnes, and these generally exhibit a preference
for clinging to the under surface of the muslin close to the
light. Similar experiments made in December, 1898, with
flasks enclosed in a double fold of white muslin, with and
without green weeds, show that a green colour becomes
habitual with originally olive, blackish, and brown specimens,
and that this colour readily passes into the nocturnal tint
during twilight. It would seem, indeed, that in captivity
specimens live better in winter than in summer, and acquire
and retain their nocturnal colour more readily.

Scattered white light, then, predisposes the prawns to
change in the nocturnal direction. In this ight, which is
markedly different from that which the animals experience
whilst hanging or lying motionless on their weeds, the colour-
patterns, which their habitat has in some way or other im-
pressed on them, are lost. Nothing could more clearly show
that the maintenance of the colour-patterns in the normal
prawns is the work of the nervous system ; though why the
nervous system fails to maintain the sympathetic coloration
under the peculiar light-conditions just indicated is beyond
us to explain.

HIPPOLYTE VARIANS. 629

So far, we have considered the nocturnal condition as
induced by darkness, or facilitated by the use of muslin
covers on the jars containing the animals. ‘This phase may,
however, be effected in bright hight. If specimens of Hip-
polyte which have stood for some hours in a white dish,
or which have just been caught, be exposed towards evening
in a porcelain dish to the full glare of the incandescent light,
they (in most cases) gradually assume the characteristic
nocturnal colour. These “ light-induced ” nocturnes differ in
several points from normal nocturnes, in which the phase
has been induced by waning light. They are no longer
keenly sensitive to moderate changes of light intensity ;
when placed in the dark or in dim light, if any colour-change
at all occurs in them, it is of the nature of an emphasis of
the nocturnal colour. In fact, the only means by which a fairly
rapid recovery of these “ light-induced nocturnes” can be
effected is the very drastic method of illumination by the
light of a sub-stage condenser. For these reasons ‘“ light-
induced nocturnes” have a peculiar value in experimental
work, and we have used them extensively for determining
the effects of stimulation on colour-changes. It may be
urged that the expression “ light-induced nocturnes” is a
misnomer, or at least far-fetched. If the criticism is delayed
till after the section on periodicity has been perused we think
that it will prove unfounded. We describe the phenomenon
here in order to collect together in one section all the facts
we have discovered concerning the conditions under which
nocturnal colour is assumed ; we offer the explanation later,
since it is only in the light of other phenomena that these
can, we think, be interpreted.

Recovery from the Nocturnal Condition. — The
facts bearing on the recovery of natural and artificially in-
duced nocturnes require further discussion. Do nocturnes
always recover to the diurnal tint of the previous day ?
Have they the power, at the moment of recovery, to assimi-
late their colour with that of new weed if, meantime, they
have left weed of one colour and attached themselves to

630 F. W. GAMBLE AND F. W. KEEBLE.

another of a different tint? Does prolonged darkness pre-
vent their recovery? ‘To some of these queries we are in a
position to give fairly confident answers. The long records
of Flasks A and B (p. 658) furnish evidence on the first and
last of these questions.

Unfortunately, recovery can only be studied in specimens
in captivity, since it is impossible to mark down prawns
at large and find them again in the morning; but, speak-
ing generally, dark-coloured and boldly marked varieties
(lined and barred colour-forms) recover precisely to their
former tints; and in cases where the colour is not the same
as that of the previous day the change is curiously enough
often in the direction of the tint of new weed placed with
the nocturnes the night before, even if the recovery takes
place in vessels completely screened from light.

Returning to the change of colour in the dark we will
quote a case in detail (Flasks A and B, July 22nd to August
4th, 1898, pp. 664—667). We may consider specimen d,
which exhibits changes from brown through green to red.
One of two small brown Hippolyte varians was placed at
5 p.m., July 29th, in the flask with much Delesseria san-
guinea (which was, however, greenish red and not full claret-
coloured). The flask was exposed to diffuse light. On
the morning of the 31st, up to which time the prawn had
exhibited no colour-change during the day, it was “ semi-
transparent, brownish.”’ The flask was covered with black
cloth in the evening of the 31st. At 10.80 the next morn-
ing (August 1st) the prawn was light brownish green.
The Delesseria sanguinea was now replaced by finely
branched red and brown weed, the prawn appearing to
choose the red. The flask was covered on the evening of
the 1st, and at 7.20 a.m. (2nd) Hippolyte was pale brown
with a reddish tinge. At 10.5 a.m. this tinge was scarcely
perceptible. The change toward redness, be it noted, took
place in the dark, and so cannot be considered as being due
to a sympathetic colour reaction. The cover replaced at
10.5 a.m. (2nd) was removed at 2.5 p.m., and the colour of

HIPPOLYTE VARIANS. 631

the prawn seen to be unaltered. Once again the cover was
replaced till 4.30 p.m. (2nd), when examination proved the
prawn to be a nocturne of a delicate blue-green colour.
After ten minutes’ exposure to diffuse light the nocturnal
colour gave place to a dull pinkish brown (tail reddish). On
August 3rd, 9.35 a.m., after having been covered from 4.40
p-m. of the previous day, the prawn was seen to be very
transparent, middle of body pale greyish red, tail brighter
red. Four minutes’ exposure in a white dish sufficed to
diminish the redness; exposure for one hour considerably
reduced the transparency. No further change occurring, it
was put with fine plumose red weed (3.50 p.m., August 4th)
and exposed to diffuse light. At 10.30 p.m. it had passed
from ‘faint red transparent” to dull brown. On August
5th it had become bright red, and on this day it fell a victim
to a larger prawn in the same flask, a fate which overtook
not a few of our experimental animals.

Another case may be given from our experiments. At
1 pm., August 14th, 1898, four green and four brown
Hippolyte were taken and placed with some Zostera in
a current of water. At 4.50 p.m. six were greenish and
two brownish. They were at once covered and placed with
finely divided red weed. At 9.30 p.m., during momentary
examination, two nocturnes were observed. The next morn-
ing at 10.50 a.m. all (except one very transparent greenish
specimen) were brown with reddish tinge, while three were
markedly reddish. Replaced in the dark at 10.50 p.m. all were
nocturnes. The next morning two were nocturnal, two greenish
brown, one light brown, and one yellow-brown. Green weed
was now put in. They nocturned again at night, and the fol-
lowing day four were transparent and green, the rest brown.

With reference to the changes occurring during the course
of this experiment, the following remarks may be offered.
A prawn of a colour other than green which recovers to
green (in the dark), especially after being in captivity a day
or two, does so, not in reference to any weed, but because it
is being acted upon by two impulses, one to full recovery and

632 F. W. GAMBLE AND F. W. KEEBLE.

the other to the retention of the nocturnal phase. Green, in
fact, is, in this case, incomplete recovery. Red, on the other
hand, is a colour specially induced during the diurnal phase
by light of low intensity, and at the onset of the nocturnal
phase; while dark brown is nothing more than the extreme
expansion of red, in a prawn well provided with yellow and
blue. A change in the dark, therefore, from green to brown
or from pale brown to reddish brown (such as we have just
shown) indicates, in the evening, the oncoming nocturnal
hue;-in the morning or afternoon the recovery therefrom
to the diurnally pigmented condition. Changes of colour,
then, occur, and some of these changes, though they occur in
the dark, are of a more or less “ sympathetic” nature, i. e.
changes which tend to effect a match between the creature
and the weed. ‘The experiments, however, seem incon-
clusive ; and not these only, but many others which we made
with a view to settling this curious point.

We believe this inconclusiveness is not due to faulty
methods, for the experiment is of the simplest kind, but in
reality indicates the nature of the explanation. Colour-
changes occur in the dark, to and from the nocturnal hue.
Greenness is frequently the mean between the daily and
nightly extremes. Normally in the dark, then, it will be
possible to catch a brown prawn going over to, or passing
from, the nocturnal condition, either in a reddish phase, or in
a green phase, or as a transparent blue nocturne, or in a fully
recovered brown stage. Hence the fact that some brown
prawns kept in the dark with Zostera appeared green is
capable of explanation. Change in the opposite sense may
also occur, a green prawn becoming brown in the dark, for
what we call a green prawn has no well-marked colour in-
dividuality ; it may have been and indeed often has been,
during exposure to hght of low intensity, of a reddish-brown
colour. At the moment of examination, after dark exposure,
it may be found as a nocturne presenting a remarkable colour
contrast to the weed on which it hangs.! If the ebb of the

1 Pl. 33, fies. 10, 11.

HIPPOLYTE VARIANS. 633

pigments is giving place to the flow, the animal may be seen
green, or, if the flow be at the full, reddish brown or brown.
The prawns in the dark are shown, in the next section, to be
continually passing to and from the nocturnal condition, and
their colour at any moment depends on the point which the
colour pendulum has reached in its periodic swing. If there
is any colour phase more stable than another, it is that
which characterised the animal during its last light experi-
ence, and hence it is to that colour-form that the animal
most frequently reverts after a nocturnal bout.

Whether the nocturnal condition in any way favours
adaptive coloration, whether it be but a defect of the quality
of a nervous system highly strung to colour attunement, a
phenomenon of fatigue, or whether it be but a reminiscence
of a pelagic habit either of the species or of some period in
its own life history, we have no means of deciding. We have
contented ourselves with describing one of the most beautiful
and striking sights imaginable, a medley of colours swiftly
passing into one harmonious hue.

Conclusions on the Nocturnal Phase.—Contrary to
Pouchet, we find that night induces a very distinct phase in
the cycle of colour-changes of which Hippolyte varians
is the subject. The same striking contrast between diurnal
and nocturnal coloration is exhibited by species of Mysidee
and by Pandalus. Pouchet himself, while denying, as we
have seen, that darkness has any effect in altering the
“fonction chromatique” in Crustacea, cites a couple of
experiments, one with two young lobsters, one red and one
blue, and the other with some dark, freshly caught shrimps,
in which darkness produced in the red lobster a blue, in the
shrimps a white coloration (1876, p. 152).

The nocturnal phase is distinguished by the disappearance,
or rather retraction, of all save the peculiar blue pigment, and
is associated with great transparency of the tissues. In some
cases the blue colour of the network is suppressed, and an
almost colourless or greyish appearance results. The phase
commences as darkness sets in, attains its full development,

634 F. W. GAMBLE AND F. W. KEEBLE.

and then passes away with the dawn. The time of the year,
the particular atmospheric conditions, and the special nature
of the coast affect the time at which the full nocturnes
occur. Recovery is determined by the same factors, In
August and September we have noticed at Piel and at St.
Vaast that the change has usually taken place by 10 o’clock,
or in captivity by 11 p.m.; while the resumption of the
diurnal colouring occurs at an early hour of the morning. In
winter (December) the times have been found to be 6 o’clock
at night and 7 in the morning, though on a clear early
morning in November (at dead low water) recovery may have
taken place by 5.30 to 6 a.m.

If this conclusion be, as we believe, correct and new, then
it follows that the full appreciation of the causes underlying
colour-change in any particular case, is not possible until a
large body of experimental work has been gathered together
on this and analogous groups of reactions.

The nocturnal condition, especially the antecedent greening,
may be induced artificially by exposing the prawns to
uniformly scattered light of low intensity.

It may also arise towards evening in “light-induced
nocturnes ;”’ that is, in prawns which are exposed in por-
celain dishes to powerful incandescent gas-light. Nocturnes
artificially produced show marked loss of irritability.

We have evidence that the nocturnal phase is a peculiar
state with respect to organs other than those of colour. The
muscular and connective tissues are much enhanced in trans-
parency, and the heart-beat is nearly twice as rapid (about
240 per minute) as it is during the day (150 per minute),
which facts point to a nervous condition very different from
that which obtains during the day. To establish these
changes in detail we require a much larger body of facts on
the normal nocturnal condition than we at present possess.

The distinctive blue colour is only one of a number of
changes affecting the whole body, and it may prove to be the
least significant character of ‘‘nocturnes.” We have some
evidence that during the nocturnal phase the metabolism of

AIPPOLYTE VARIANS. 635

Hippolyte differs in an important manner from that which
obtains during the day. Indeed, we are prepared to say that
the nocturnal state opens up a new chapter in biological
investigation, and that by a study of this condition increased
knowledge of the succession of metabolic events may be
gained.

Section VI.
Periodicity of Colour-change.

Hippolyte of the most diverse hues become nocturnes
at evening. Daylight invests them once again with their
motley. Change of light-intensity ushers in either colour-
change. As light waxes the diurnal colour appears; as it
wanes, the blue. Change of light-intensity is, we have shown,
an efficient stimulus to colour-change. No other factor of
their environment, as far as we have discovered, so profoundly
affects the colour-state. It might therefore be concluded
that the morning and evening changes are due, and solely
due, to increase or decrease of light-intensity. Recovery
from the nocturnal state seems, however, at times to anticipate
the dawn, though this might be supposed to be due to the
exquisite sensibility of Hippolyte in the nocturnal phase.
But the colour-change occurs, though light-conditions are
constant ; in other words, the change is periodic. The idea
of periodicity is familiar to the botanist and physiologist ;
the former knows it to be a function of growth itself, and of
the “sleep”? and other movements of many sensitive plants ;
the latter recognises it as characteristic of the metabolic pro-
cesses in higher animals. The only case among Invertebrates
in which periodicity has been claimed to manifest itself—
though it cannot be said that it has been demonstrated—is
that of the ascent of small pelagic animals to the sea-surface
at night, and their descent to deep water during the day.
The argument in favour of the periodicity of this movement
lies in the behaviour of the Southern Plankton borne into
northern waters during the short arctic summer. It is stated
(Walther, 1893, p. 148) that, though the light-intensity re-

636 F. W. GAMBLE AND F. W. KEEBLE.

mains relatively high during the night, the vertical movements
of the Plankton still continue. By periodicity is meant that
rhythmic use breeds rhythmic habit; that by recurrent
change of light or other stimulus the organism comes to
manifest the phenomenon of movement or other change, to
lapse again to its former condition, and to repeat this sequence
at regular intervals although the stimulus be withheld.

In the case of the colour-changes of Hippolyte, change
of light-intensity is the efficient stimulus. By this stimulus
the red and yellow pigments may be expanded. By the
stimulus resulting froma lowered light-intensity these may be
retracted and replaced by blue. If these changes are a func-
tion of the time, i. e. if they are truly periodic, they should
exhibit themselves when light-conditions are constant. This
they do. We will not stay to discuss whether a mental pic-
ture of the process can better be obtained by likening the
phenomenon of periodicity to “memory” (see Darwin and
Pertz., ‘ Annals of Botany,’ vi, p. 262), or to a persistent after-
effect of precedent stimuli, but proceed at once to give evi-
dence of the fact. his evidence is derived from experi-
ments on the effects of continued darkness and continued
light on the prawns.

Effect of Continued Darkness (Table IX).—In each
of four “ air-circulators” three specimens of three similar
colour-forms were placed. They were fed with pieces of
other prawns. The eyes of the prawns in two of these flasks
(B and D) were amputated. Flasks A, B,and D were covered
(by double folds of close black cloth); C, a control, was
exposed to the light. The experiment lasted from Septem-
ber 3rd, 10.80 a.m., till September 7th. During each exa-
mination necessary for recording, the black cloths were
lifted for the shortest possible time—usually about fifteen
seconds. In the afternoon of September 3rd, the prawns in
the covered vessels showed distinct change in the direction
of transparency and greenness, one or two being nocturnal.
The prawns in ©, the exposed vessel, showed no colour-
change. In the evening all in the control and inthe covered

HIPPOLYTE VARIANS. 637

vessels were nocturnal, though the depth of the nocturnal tint
varied. ‘Those in the former were all nocturnes of differing
degrees, the latter were fully nocturnal. The next day,
September 4th, 12.30, soon after noon all the specimens had
recovered ; those in the covered flasks had completely regained
their diurnal tint, and even the amputated specimens had ac-
complished the change as fully as the rest. This had come about
while the interior of the covered flasks was absolutely dark.
In the evening (9.50, September 4th) the amputated speci-
mens were clearly behind the others in assuming the nocturnal
phase ; indeed, the two specimens in Flask D as yet showed
no signs of its appearance, while the remainder were full
“nocturnes.” On the next morning (September 5th) the
amputated prawns were brown or reddish brown, the normal
ones in the covered Flask A were transparent green, and the
control specimens in C had assumed the tints they started
with on September 3rd. In the afternoon the only change
was an increase of transparency in Flasks D (covered),
C (control), and a slight greening effect in the latter, so that
the normal prawns in A had not fully recovered their diurnal
tints. At 7 o'clock (it bemg only dusk) C (control) was in
the transparent green stage; the remainder were all nocturnes,
some fuller than others. At this point the experiment was
directed from the effect of constant darkness to ascertain the
effect of short exposure to incandescent light. The most note-
worthy point was that the recovery of the amputated speci-
mens was as complete as those of the normal controls, but
that result is beside our present object. The experiment
shows that although the Flasks A, B, and D are kept in
constant darkness, yet there is the same succession of
diurnal and nocturnal colour-phases as is characteristic
of the prawns under natural conditions. It also shows that
darkness has some effect in retarding the normal times at
which these phases recur, and in weakening them. Further
evidence of the periodic colour-change is seen in Table X
(constant dark experiment, August 26th to 28th, 1898), and
von, 43, PART 4,—NEW SERIES, YY

638 F, W. GAMBLE AND F. W. KEEBLE.

is especially well shown by the brown specimens in “ water-
circulator”? B and those in Fiask Aa (pp. 686, 687).

Other experiments with the same object show that the
longer continuous darkness is employed, the more it seems to
wear down the periodicity ; so that, after a few days, noc-
turnes may be found at almost any hour of the morning.
Moreover an extraordinarily irritable condition supervenes, in
which Hippolyte rapidly responds to alternations of lhght
and darkness. Thus (Table I, specimen A in Flask A) a
large specimen, which had been under observation since
July 29th, and in the dark most of the time, at 7.15 a.m.,
August 2nd, had recovered slightly to a vivid transparent
green, and after two and a half hours’ exposure to diffuse
light, had become brown. It was now covered again, and at
2 o’clock was already almost fully nocturnal, and was then
exposed to light for half an hour, and once more regained
its brown colour though not fully. It was now put in the
dark, and at 4.15 was a good nocturne, but lost much of its
blue transparency during ten minutes’ exposure to light.

Whether more prolonged, more complete exposure to dark-
ness would result in the formation of permanently nocturnal
Hippolyte we have not determined, but experiments lasting
twenty-four hours, eighteen, and thirty-six days, made by
Professors Brooks and Herrick, on Palemonetes varians
(1895), showed that in all three cases when the dark chamber
was unsealed the prawns originally of a shade of light brown
or brownish green had become nearly white and looked
bleached. Unfortunately these authors give no information
as to whether recovery took place, their object being to test
the effect of darkness on the colour of the newly hatched
larve, and on the pigment of the eyes of the young and of
the mother. They found that there was no appreciable dif-
ference between the colour or the optic pigment of these
larvae and of others born under natural conditions, but that
in the eye of the parent prawn continued darkness had pro-
duced a remarkable migration of the pigment and distal
retinular cells outwards towards the cornea.

HIPPOLYTE VARIANS. 639

Effect of Constant Illumination (Table VIII, p. 683,
and Summary, p. 652).—A series of ‘ water-circulator”
glass vessels covered with muslin were placed in porcelain
dishes against a background of white cardboard. The cur-
rent of water circulating through the vessels kept the
temperature low and fairly constant. The vessels were
illuminated by incandescent light, but a source of error was
admitted by our inability to screen the vessels from diffuse
daylight. An experiment was commenced on September 3rd
with six brown, yellowish-green, and red specimens. ‘The
lamp was lit at 5 o’clock, and at 9 p.m. all six were nocturnes.
The next day at noon the prawns had recovered to an emerald
green colour, which was maintained till 6 o’clock, and at
9.50 p.m. had passed again into the nocturnal blue tint.
The next day (September 5th) at 11 a.m. the prawns were
green, but in two cases had recovered in the tail region to a
grey or greyish-brown colour. At 7.30 p.m. two were noc-
turnes, two were sick and moulting (a constant source of loss of
specimens), two were transparent green (Table VIII, p. 683).
In another experiment (made on August 26th and 27th) the
diurnal phase continued during the times of observation, but
the majority of observations on the effect of incandescent
light at night (as was pointed out in another connection on
p. 629) tend uniformly to the conclusion that it does not
inhibit the recurrence of the nocturnal phase, at any rate for
the first two nights; though here again we do not know the
effect of long-continued illumination which occurs in nature,
for example during the summer on arctic shores.

It might be urged, however, in regard to these experi-
ments, that the occurrence of nocturnes should not be con-
sidered as evidence of periodicity (which is our view), but as
indicating the power of response of Hippolyte to a very
small difference of light intensity. or, during the day, the
observation dishes are exposed to a certain amount of diffuse
light (reduced as far as possible by drawn blinds) in addition
to incandescent light, while, during the night, the latter is
alone operative. This objection may be met by an appeal to

640 F, W. GAMBLE AND F. W. KEEBLE.

the previous experiments on the effect of continuous dark-
ness, where the only source of error is the brief exposure of
the animals to light during the recording of their condition.
If the periodicity were more perfect, it would be possible to
eliminate this source of error by leaving the animals in con-
stant darkness for a long time, and then opening some flasks
at morning, others at midday, and so on. Unfortunately the
periodicity is far from perfect, the habit is but imperfectly
acquired. After prolonged dark-exposure the animals may
appear in the nocturnal phase at any hour of the day. Other
difficulties in the way of bringing this method to a successful
issue are the facts that the prawns eat one another with pro-
voking frequency, or die moulting only too often.

But we appeal also to another class of facts, against the
hypothetical criticism that the constant-light experiments
may only show that the prawns are extremely susceptible
to small changes of light-intensity. In the first place, we
have no evidence that when the light-intensity is already
high this susceptibility is a fact. In the second place, we
have the evidence of the “ light-induced nocturnes” already
described which we must now discuss. Prawns exposed to
a bright light—the incandescent—reflected from a porce-
lain surface pass rapidly into a green colour phase, and
toward evening they become brilliantly nocturnal. Toward
morning they revert to their green colour, which is the
“diurnal colour” of prawns subject to this high light-in-
tensity. Viewed in the light of what we now know of the
periodicity of colour-change, it no longer appears a paradox
that change towards darkness or to increased light-intensity
should result in the same nocturnal coloration. The habit
is the dominant factor in the change. Prawns tend to
“nocturne” toward evening, and the tendency is sufficient
to overcome the antagonistic direction which the light
stimulus would and often may induce. Just as a cup of
black coffee at evening may be inefficacious in disturbing the
periodic function of sleep in men, so, too, the stimulant light
may fail to dominate the nocturnal tendency in the prawn.

HIPPOLYTE VARIANS. 641

Further, as black coffee served out to a number of men may
here and there succeed in effecting wakefulness, so we find
that in a batch of prawns subject at evening to high light-
intensity some individuals maintain their diurnal colours and
habits, whereas others are proof against the excitant. Indeed,
in devising the experiment of constant illumination we anti-
cipated that the prawns would, by reason of their periodicity,
resist the stimulus of light, and were delighted to find our
expectations realised.

It may be urged that in the colours of deep-sea Crustacea
we can observe the effects of long-continued darkness, and
that such forms exhibit no permanent nocturnes. Now, in
the first place, we are not prepared to assert that continued
darkness does induce permanent nocturnes. We know that
other organisms exhibiting periodicity pass, after a certain
exposure to constant-light conditions, into a state of rigor.
In this state of rigor induced by constant darkness, the
organism may assume a condition more like that which it
normally displays during the day. So it may possibly be with
Hippolyte. The colour-rigor, if such occur, may possibly
be more like the diurnal than the nocturnal colour-phase,
though the observations of Professors Brooks and Herrick,
already cited, on Palemonetes varians tend to show that,
in the case of that animal, a condition akin to that of our
“nocturnes” is effected by prolonged darkness. In the
second place, although the briliancy and depth of tone
of the red coloration of the arctic and Norwegian deep-
sea species of this and allied genera, adds point to the
possibility which we have just indicated, yet we suggest that
before the colours of deep-sea forms can be appealed to,
these colours must be observed with more precautions than
have yet been taken. We have seen how the colour of a
full nocturne may give place almost instantaneously to the
diurnal condition; hence, before any statement can be made
as to their natural colour, the deep-sea Crustacea must be
protected from light and other disturbing influences on
their way to the surface. Even “shock,” as we shall show,

642 Fk. W. GAMBLE AND F. W. KEEBLE.

may profoundly modify the colour; and though we do not
presume to say how these difficulties can be overcome, we
would point out how small a value colour-records possess,
when made without these precautions.

Indeed, the existing records seem to show that colour-
changes may occur during the ascent of the trawl. Not a
few of the Crustacea figured by Milne-Edwards during the
“Talisman ”’ expedition show the red in patches on a more
transparent ground. Another good case we quote from
Prof. G. O. Sars. In describing the Crustacea of the Nor-
wegian North-Atlantic expedition the author refers (p. 32)
to Bythocaris leucopsis, a prawn allied to Hippolyte.
The colour is a “ magnificent rosy red, a trifle more intense
at the end of each segment of the posterior division of the
body. Extending across the middle of the carapace is ob-
served, moreover, a large irregular saddle-shaped area of
a dark bluish colour. Again, the “ Albatross” brought up
a prawn, Benthesicymus Tanneri, from eight hundred
and sixty fathoms, which showed a considerable amount of
blue colour; and Professor Faxon, in reporting on the pecu-
liar spottiness of the colour, makes the suggestion ‘that the
unique coloration of the deep sea prawn may be due to a
change of colour undergone by the animal as it was brought
up into the full blaze of day” (loc. cit., p. 255).

Conclusions.—During the night, Hippolyte varians
exhibits a condition markedly different from that shown
during the day. The most striking feature of the nightly
condition is the colour (nocturne) ; though other peculiari-
ties, such as the state of nervous irritability and the in-
creased rate of heart-beat, accompany the colour-change.!
The complete colour-cycle, from diurnal phase to nocturnal
and back again, is completed in about twenty-four hours.
Experiments in which the animals are subject to constant
light, as well as those in which they are kept in constant
darkness, show that the change is periodic; that is, it

1 Other changes in the muscular system and digestive-gland, accompany
the nocturnal phase.

HIPPOLYTE VARIANS. 643

declares itself when the external stimulus—change of light-
intensity—is cut off. The ‘dark-induced” nocturnes are very
susceptible to light-stimuli, the “light-induced” nocturnes
are on the contrary refractory to them. The periodicity is worn
down by constant light-conditions. Though we have evidence
that the final phase of long-continued exposure to constant
conditions of darkness is one nearer the nocturnal than the
diurnal state, we are not prepared to state that this is the
case. Blinded prawns exhibit periodicity, though often
the phenomenon is complicated by the immediate effects of
the operation. The shock does not appear to wear off com-
pletely, since prawns, whose eyes have been rendered func-
tionless by section of both optic stalks, are longer in
performing the complete cycle of changes.

The possibility of permanent nocturnes and of “ colour
rigor” must be borne in mind in investigations on the
colour of deep-sea Crustacea.

Periodicity, which we believe is a new fact in colour
physiology, may turn out to be a phenomenon of very wide
occurrence among animals with contractile ‘‘ chromato-
phores.”

Section VII.

The Control of the “Chromatophores:” the Parts
played by the Hye, Central Nervous System, and
by the Chromatophores themselves, in effecting
Colour-change.

The fact that Hippolyte varians is ab any moment of
the day or night passing towards or away from the nocturnal
condition must be reckoned with in any attempt to explain
alteration of the chromatophoric condition. In discussing,
in the last two sections, the effects of external agents such as
differently coloured seaweeds and varying light-intensities we
pointed this out. We have now to keep it in mind whilst
endeavouring to trace the nature and the course of the
impulses which play upon the “chromatophores” themselves.

That the “chromatophores” respond independently of the

644 F. W. GAMBLE AND £. W. KEEBLK.

central nervous system, and to that extent directly to light,
the pigments flowing into the branches from the centre, was
shown by cutting off appendages and making camera draw-
ings of a selected pigment spot. In one case the antennal
scale of a greenish prawn was cut off, and a “chromatophore”’
carefully observed and drawn at short intervals. Twenty-
three minutes after the first drawing, the red and yellow
pigments had considerably expanded and penetrated into
the branches. In another case, Pl. 36, fig. 86, a chromato-
phore was chosen from a prawn which was undoubtedly dead
after the first sketch was made ; the heart had ceased to beat
and the scaphognathite had stopped. Thirty-five minutes
afterwards, when the last sketch was made, the red and yellow
pigments were still actively spreading into the branches.
To make the crucial test of the direct power of response of a
“chromatophore ” it should of course be completely severed
from all its nervous connections. ‘This we have not yet done,
and consequently the results of the observations just quoted
cannot be regarded as definite proof of a direct response of
the chromatophoric pigments to changed light conditions.
We employed several methods in attempting to render the
eyes functionless without causing shock. First, we tried to
render the cornea opaque by means of a mixture containing
Indian ink, which when dry is insoluble in sea water, but the
difficulty in maintaining the respiratory current whilst allow-
ing the cornea to dry, and the uncertainty that light is
totally cut off from the retina, made us abandon this method.
We succeeded better by painting the eyes either with a
solution of collodion in ether, or with silver nitrate, and the
results thus obtained were confirmed in animals blinded
either by snipping off the eyes near the base of the eye-
stalks, or by pinching the optic ganglia with fine forceps.
Different specimens of Hippolyte varians exhibit curi-
ously different degrees of shock under the operation. Noc-
turnes, for example, either remain motionless and strongly
bent, moving erratically if at all, or immediately find their
legs and exhibit little outward sign of discomfort. Ampu-

HIPPOLYTE VARIANS. 645

tation of one eye produces little effect. In the dim light or
towards evening, prawns thus treated often become beauti-
fully nocturnal, and recover quite symmetrically when
brought into light. Amputation of both eyes causes, in a
large proportion of cases, in brown specimens, a sudden
appearance of the green colour, and, if the specimens be then
put in the dark, a rapid transition to the nocturnal colour
(Table XI, p. 689, Specimen G). In speaking of periodicity
it was pointed out that amputated specimens nocturne and
recover, though somewhat irregularly, and we can now bring
additional evidence to confirm this. The preliminary green
effect which often followed all our methods appears due in
part to shock ; more largely, however, to suddenly cutting off
the light by way of the eyes (some, however, became reddish).
The most complete evidence of the behaviour of prawns
when amputated or “nitrated” in comparison with normal
control specimens is given in T'able XI, pp. 688—691. Thus
G, originally a dark brown form (August 19th, 12.45 p.m.),
became greenish after removal of the eyes, and by 3.50 had
become nocturnal. It was then placed in a white porcelain
dish and exposed to daylight in the open till 7 p.m., after-
wards to the incandescent light. By 9.30 both G and BE
(a specimen whose cornea had been treated with silver
nitrate) had become semi-nocturnal, while the normal control
specimen (I*) was now a full nocturne; that is, the speci-
mens whose eyes had been operated upon had become
nocturnal, and then in part recovered before the time of
nocturning of uninjured specimens. G recovered fully by
9.50, H in two minutes, and both were now put with F in
a muslined jar. At 10.40 p.m. G@ and E were again
nocturnalish, I nearly full nocturne.

Another example is C, which appears to show in addition
that amputated specimens respond more slowly to change of
light-intensity than do normal ones. ‘The specimen operated
upon (C), and a control (I), were placed in a vessel beneath
a Landolt lght-filter arranged to transmit red light. C,
originally put into red light at 3.50, had, together with the

646 F. W. GAMBLE AND F, W. KEEBLE.

control (I), become greenish or greenish blue at 7.10; but
when again examined at 9.5 p.m. the normal specimen was
(as is usual with uninjured Hippolyte) a full nocturne. (C)
was partially nocturnal, but recovered to brown after five
minutes’ exposure to white light.

Both these experiments show that the difference in beha-
viour between amputated and normal specimens is due in part
to the effect of shock, in part to the loss of sight, and hence
that the direct action of these changed light conditions on
the chromatophores themselves is negligible. A series of
camera drawings of amputated nocturnes exposed to light,
Pl. 35, figs. 29—32, exhibits the flow of red and yellow pig-
ments from the centre to the branches of the chromatophores.

So far we have dealt with the results of the elimination of
the eye’s action during the diurnal phase. Amputation of the
eyes of a full nocturne at 9.15 p.m., August 5th, caused no
immediate colour-change, nor had any change occurred at
9.40 nor at 10.25 p.m.

Stimulation by Section of the Ventral Cord, by
Ether, Electricity,and Change of Temperature. The
nocturning and recovery of amputated specimens indicates
that the periodicity does not reside in the eye and optic
ganglia, but is a function of the rest of the nervous system.
The colour-effects produced by the response of this system to
various forms of stimulation have now to be considered.

A very curious result is obtained by section of the nerve-
cord in the middle region of the abdomen just below the
“hump” or line of flexure of the tail. The behaviour of
nocturnes may first be mentioned.

The cord of a large full nocturne was cut just below the
“hump,” and the prawn was then exposed to light in a white
porcelain dish. The tail region recovered first and almost
immediately after the operation. The head recovered some-
what later, while the middle part of the body retained its
nocturnal colour after half an hour’s exposure to light. The
sudden shock may be pictured as setting up impulses
which, besides effecting violent contraction of the swimmerets,

HIPPOLYTE VARIANS. 64:7

inhibit the normal tonic impulses which hold the red and
yellow pigments retracted. ‘The tardiness of the middle
region of the body to recover is perhaps due to the structural
peculiarity of the nervous connections with the chromatophores
of that region, since, in the course of recovery of intact
animals from the nocturnal condition, the middle region is
frequently bluish green when the head and tail are brown.

Returning to the effect of section of the cord in intact
Hippolyte, we record the result in a brown specimen which
was put in the dark after the operation. At 7 p.m. it was
examined and was found to exhibit a full nocturnal tint
behind the eyes, while the region of the tail, just in front of
and behind the line of section, had remained brown.

In this connection experiments made by immersing Hippo-
lyte in a mixture of ether and sea water, may be mentioned.
Intact and eye-amputated (brown) specimens react to this
mixture in a similar way. ‘They exhibit no immediate colour-
change, but when taken out and placed in a current of sea
water a green effect frequently appears just behind the eyes
and extends back to the hinder end of the carapace, the
remainder of the body resting unchanged or becoming lighter
and more transparent. Intact specimens, in twenty minutes
or so, revert to their original colouring or remain somewhat
hghter. Amputated specimens exhibit the green effect more
conspicuously as a rule, but also recover ina short space of
time.

An even more marked change of the same kind is obtained
by painting the eyes with collodion. Here the operation is
complicated, involving blindness and ether-poisoning. ‘The
green effect took place all over the body (on brown speci-
mens), but subsequently passed away. A second coat re-
induced the change, from which, as well as from the ether-
experiments, it seems clear that the green effect is due to the
action of the ether on the central nervous system—possibly
(in the case of painting the eyes) on the optic ganglia.

The action of the interrupted electric current is somewhat
similar. Thus if a “light-induced nocturne ” is exposed to

648 F. W. GAMBLE AND F. W. KEEBLE.

a fairly strong current for thirty to sixty seconds, no imme-
diate result follows, but if replaced in water (when it les
motionless except for the beating of the swimmerets) it soon
loses its nocturnal colour and transparency, the tail becoming
brown in half an hour, and the head either brown or green,
while the middle region retains the nocturnal effect longest,
as in stimulation by high light-intensity. On green specimens,
thirty-seconds exposure to the interrupted current is fol-
lowed, after a lapse of half an hour, by a brown coloration.
In order to determine the mode of action of the current, a
green specimen was taken from a jar placed in the same
hght-intensity as that in which the induction coil was stand-
ing. The body was cut across the middle. First the front
half was stimulated, examined after the lapse of ten minutes,
and found to have extruded some red pigment and recovered
brown. Ina similar way the tail-half recovered. In other
cases the latter was stimulated first and recovered to brown
while the former remained unchanged. These results tend to
show that the interrupted current acts through the ventral
ganglia, or on the chromatophores directly, and not through
the cerebral centres.

Finally a simple but distinct effect follows a sudden ex-
posure to high or low temperature. In one experiment, of
three light-induced nocturnes, one was placed in water at the
temperature of the laboratory (60° F.), a second in water
cooled by a jacket of ice and salt to 8° C., and a third in
water standing at first at 93° F., but falling in five minutes
to 83° F. The experiment began at 9.20 p.m., August 6th,
and in five minutes the first had recovered to greenish
brown; the second was unchanged; the third, though appa-
rently killed, was and remained for hours, if anything a more
brilliant nocturne than before. After thirty-five minutes the
nocturne in cold water showed traces of recovery, which,
however, was not fully completed after an hour’s interval.

Conclusions.—In addition to light, other forms of stimu-
lation—ether, or recovery from its effect, electricity, cold,
shock—may affect a change of colour in Hippolyte varians.

HIPPOLYTE VARIANS. 649

While changes in the quality and intensity of light act no
doubt to a large extent through the eyes, other of these
agents must have acted independently of these organs, and
appear to influence the central nervous system directly, and
through it the chromatophores. We have, however, some
reason for believing that a redistribution of the pigments in
these bodies may take place independently of nervous
control. Apart from the periodically varying action of the
nervous system, it seems probable that any condition of the
chromatophores is largely maintained by impulses passing to
them from the nervous system. ‘he impulses passing from
the optic ganglia to the “ brain” cause repeated alteration of
those received from the ventral ganglia. When, for example,
by amputation of the eye the optic impulses are cut off,
profound changes occur often immediately ; changes which
result in a retraction of red pigment, and even in extrusion
of the blue. Recovery subvenes. ‘The central nervous system
would appear to reassert itself and reassume its presiding
influence over the chromatophores.

Two considerations only remain: how can the phenomena
of periodicity and of the nocturnal phase be interpreted in
terms of utility ? and of what practical importance are they in
further studies of the colour-changes of Crustacea? On the
first pot we prefer to say nothing till we have learnt more
of the habits of Hippolyte varians and of its nearest
allies. We require to know, for example, whether periodicity
is acquired during a lifetime, or is transmitted as a quality
of the bodily structure of the larva; whether any of these
prawns are or were naturally pelagic during the whole
or part of the day; whether, in the particular instance of
Hippolyte varians, the change from the free-swimming
larva to the quasi-sessile life of the adult is accompanied by
the appearance or modification of these phenomena. It igs
conceivable that the “nocturne” is a nightly reversion to
the blue-green colour so characteristic of pelagic animals ;
- that the whole purpose of the wonderfully elaborate chro-
matophoric system is to enable the prawn to respond to

650 F. W. GAMBLE AND F. W. KEEBLE.

changing intensities of light; that the nocturnal phase of
colour (or colourlessness) is an extreme expression of the
contractility of this system—is a defect of its qualities; and
that the daily life of the prawns’ colour-work is “rounded
with a sleep.”

The other question, of the practical importance of pe-
riodicity, is one which admits of a more confident statement.
It is clear that this phenomenon has to be borne in mind in
the description of any colour at all, and especially of any
colour-change induced by stimulus; and that since the
colour-condition of the animal is a function of the time of
day, that time of day must be taken into account before
conclusions can be drawn as to the real effect of the stimulus
in question.

(An abstract of this paper has appeared under the title
“The Colour-physiology of Hippolyte varians” in the
‘Proceedings of the Royal Society,’ January, 1900, vol. xlv.)

HIPPOLYTE VARIANS.

651

Section VIII.—Summary of Experimental Records.

Name of

Table. :
experiment.

Object of
experiment.

Results.

I Weed colour

experiment 1.

Flask A

II | Weed colour |
experiment 2.|

Flask B

IIL | Weed colour
experiment 3
IV | Weed colour
| experiment 4

V | Light.

intensity
experiment 1

To test result
of placing
Hippolyte
of one colour
with weeds of

| a different tint

Same as that
of Table I

Same results.

No evidence that the colour of the weed

as such has any effect. Changes of
colour, referable in every case to a
daily cycle of colour-change, influenced
to some extent by the illumination.
Irritable coudition on Aug. 2nd seen iv
A, B, and C, followed by rapid changes
to and from the nocturnal state of
colour.

The changes to green and
to red noticeable in specimens A and d
respectively occur in the dark, and
therefore cannot be due to the colour of
the weed, although in both cases the
change was in the direction of the
colour of the weed.

To test result |The two Hippolyte exhibited rhyth-

of putting two
greenish-brown
Hippolyte
varians and
one Spironto-
caris pusiola
with green
Zostera

Two green
Hippolyte
placed with red
Delesseria
in the open

mical nocturnal changes, and assumed
during the day a bright emerald-green
and greenish-yellow tint matching the
leaves and stalks of the Zostera.
These changes took place as well in
the dark as in the light (see July 30th,
12.30 p.m., and Aug. 2nd, 10.10 a.m.),
and therefore cannot be attributed to
the colour of the weed. Spironto-
caris remained throughout of a trans-
parent bluish colour.

In 34 hours one became brown, and

showed expansion of red pigment on
being examined microscopically.

To test result |Begun 4.6 p.m.; examined 7.30 p.m.

of placing
freshly caught
Hippolyte
under varying
light
intensities

Dim scattered light produced by
covering a porcelain pot with muslin
is most favourable to the induction of
“nocturnes.” A muslined glass jar
produces a green colour. Clear glass
jar standing exposed to full daylight
and black covered jar produce very
slight changes in the Hippolyte
placed within. [In some of our more
recent experiments (1899) nocturnes
were found in the black covered jar,
but muslined porcelain always is most
favourable. ]

with blinded
Hippolyte

652 F. W. GAMBLE
Table. Name of Object of
experiment, experiment.
VI Light- _|To test effects of
intensity | different light-
experiment 2} intensities
compared with
that of exposure
to red, green,
and blue light ;
on the diurnal
and nocturnal
conditions
|
|
Vit Coloured To test effects
light of green and
experiment | red light on
nocturnes
VALET Constant To test
| illumination | periodicity of
experiment | colour-change
IX Constant To test the
dark experi- | periodicity of
ment 1 colour-change
in normal and
blinded
specimens
D.¢ Constant To test
dark periodicity
experiment 2
XI | Experiment | To test effect

of removal of
the eyes, and of
otherwise
blinding the
prawns, on
periodicity of
colour-change

AND F. W. KEEBLE.

Results.

1. Effect of red and blue light on
“diurnal”? prawns is to produce ‘‘ noc-
turnes.” Green light had no effect.
In the control-jars a more or less green
colour was produced, especially in the
porcelain ones. 2. Nocturnes pro-
duced and maintained though sub-
jected all night to red, green, and
blue light derived from incandescent
gas flame. They persisted till next
morning under these conditions.
‘‘Light-induced nocturnes” also ob-
tained by allowing Hippolyte to-
wards evening to remain exposed to
light in porcelain dishes. Next morn-
ing, however, they had recovered.

This experiment also demonstrates
* periodicity,” in that the habit of the
animal enables it to assume the noc-
turnal hue in spite of the continued
illumination.

As in the previous experiment, nocturnes
under bright red or green light persist
all night and next morning in this
condition, only losing somewhat of
their transparency the following after-
noon. Contrast with control speci-
mens which recovered next morning.

Periodicity shown by the fact that all the
specimens became nocturnes the first
evening in spite of the constant illu-
mination. Partial recovery ensued,
and this was followed by complete
nocturning in three cases. The same
occurred the following day.

Periodicity shown. The blinded ones
nocturne and recover more slowly than
the normal. Proof lies in comparison
with behaviour of a specimen (C) ex-
posed to natural alternation of night
and day.

Periodicity clearly shown, especially in
the small brown specimens in Flask B,
those in Flask Aa, and in the water-
circulator B.

Experiment shows that periodicity per-
sists though the eyes are rendered
opaque or removed. The nocturnal
colour is assumed and the recovery to
the diurnal tint effected as in normal
specimens, but more slowly.

-

(or)
or
Go

HIPPOLYTE VARIANS.

APPENDIX. EXPERIMENTAL 'T'ABLES.
List of Abbreviations.

Colours. —Since each of the terms brown, blue, green, red, covers such a
wide range of colour, it is necessary to define more exactly what we mean by
them. By brown is meant the colour of the brown seaweeds (Fucus,
Halidrys, or Laminaria); by green, emerald green (of Zostera); by
red, a claret colour; by blue, various shades of indigo. Yellow (when seen
by transmitted light) is a straw-colour, but by reflected light yellow is the
most brilliant Indian yellow. By this illumination “frosted effects” are
often recorded. By this term we mean a bright almost sparkling colour,
suggesting a reflecting substance. The yellow, whitish, and blue markings
(invariably quite on the surface of the skin) are of this kind. By transmitted
light such markings are dull and greyish.

Topographical Terms.—The body of Hippolyte varians has a hump in
the middle of its back or tail. As this point of flexure is often distinctively
coloured some term is necessary, and ‘‘ hump” has the merit of being clear
and short. The two flat scissor-like blades of the antenne are spoken of as
the ‘antennal scales.” As the body is frequently of one tint in the middle
region (usually from the stomach to the hump), and of another in front of
and behind this central portion, we speak of the “Mid,” “ Ant.,” and
eid!’

Ground Colour.—Apart from the obvious ‘‘ chromatophores” the body fre-
quently appears to possess a ground colour possibly due to diffused pigment,
possibly to very fine chromatophoric branches.

Chromatophores.—The apparent form of these bodies alters as the pigments
flow outwards from the centre or retreat towards it. When the pigments are
maximally contracted they form irregular masses of one or more colour, and
the chromatophores may then be described as ‘‘ contracted,” though the term
applies rather to the pigment than to the chromatophore, the actual form of
which is probably unaltered. In this condition the pigments (by reflected light)
often show what look like ‘‘ coloured vacuoles ” (see supra, p. 626), the nature
of which is uncertain. As the pigments flow outwards the form of the chro-
matophore appears to change from an irregular to a “stellate,” and then toa
*‘branched” one. The branches unite with those of neighbouring chromato-
phores, and so may form a network in which the “ centres” are unrecog-
nisable.

Blue Spots.—These spots, described on pp. 610, 611, may be surrounded by a
clear ‘ halo ” or transparent envelope crossed by ‘ radiations,’ some of which
(red or blue) are usually thicker than the rest.

Ant. The region of the body in front of the stomach.

VOL. 43, PARTY 4,.—NEW SERIES. Tay

654. F. W. GAMBLE AND F. W. KEEBLE.

Ant. scales. The blades or scales of the antenne.
B.s. Blue spots.

Chrom. “ Chromatophores.”

Covered. Means that the vessel in question is protected by black cloth from
the light.

Drip. A current of water flowing through an experimental vessel.
Ground. Short for ground colour.

Hind. The posterior region of the body from the “hump” backwards.
L.3.3. Leitz’s system, 3 ocular and 3 objective.

Mid. The central region of the body from the stomach to the ‘“ hump.”
Noct. Nocturne.

Ntwrk. Network produced by anastomosing branches of ‘‘ chromatophores.”
R. By reflected light.

Recovery. Resumption of the diurnal colour after the nocturnal phase.
7. By transmitted light.
Transp. Transparent.

Uncovered. Means that the vessel in question is left exposed to diffuse
light.

655

i VARIANS.

HIPPOLY'T

‘u9eis YSINTq “y

‘papuedxa Ajeyerepout ‘yovlq \L

‘por gavd ut ‘yacoa\jou ontq

“ystn[q-ueerS “yueredsueary,

“0S°6 paumexg “(onyq

ssay faaueets ‘yuoredsuvay a10ut 2)

aka poyen 0} Alaa0v01 OU (G6 TV

o0I—8 F# A9zBm WI OSG 9” pIorid (1)

"urd 086

aq qista
mnaconat (9)
JO soat4ua0
ou ‘uaars
-pox [ap
YIOMIOUW “AY
AOA SOUL
= 11e ‘Apoq
[v4jueo OU *Y,

Moos
pue ‘teers

‘poysouy ‘MaedS YsInyq YLoageu |‘pert “1oagzou
[fuses yavp “yovlq ysomye “yy

euy Art0A
yytas “moTpak

YIM uaerS ystmorjek punors *y| punoas +7,

pow
apissuoye Ajquereddy Sutk] soyoursq meats
‘pPABMJNO SatjM9O WAZ YSItIIeIS SurutoDeq |
“TLOAT[D SWOS ‘Sa1}UD pat PUR ‘UIEIS ‘mor[o4 |
quelyiag yi “utoayo AraAo ysoumye “yy!
UOOULO4 FB UI
sv sayojed eer8 YAIM WNTNOYAI pat asoo[
fsaTONoVA OINIG-oTYAM YIM pot yup “|

MOTIOA “yy,
AMO
-oq oes ‘AroAooar [eyyaed 10978 poutmex|

— = = avy WH |
uses UMOLQ UMOIQ euinqoou
YSIUMOIg pury, ‘wae1y JIB | ystuMorg Wa
|
Jeter “wid SLOT ‘wd OL‘OL we'd OT
~u'd cfg ule O88 Re ee ee ee
WO “SNy

“QU SIT JUdOSopuROUT

\YStuaeds YqTAs

soyoqed

ytomyou saroyd
vB UT poy -OFEUIOIYD
aMoyjoo
punoas
ee "I a1doosos01 yl
auou ouoaed
10 9]49UT -SUBL,
yoryq INo]oo
-UMOIG [eatauex)
“urd ¢

“aut] oyyM ou (;)
*“youlq-uMorqg asavy

‘SUOIJIPUOD eUINooNT dtoyy Jo pue ‘oyAjoddiy UMoAg omy, Jo sploooy ordoosorory

268] ‘Hig isapoy ‘gq YSVIq Woud (Z) aNV ({) SNaWIOadg

(‘g99 ‘4 ‘TT e1qeL 0288)

‘aquooay YOOTOS) AO A1dNVXi

W. GAMBLE AND F. W. KEEBLE.

i

656

‘giqistaur Aycvou

wnypnoyet
‘ora
u90a3 [[Np "Y quieyz ystuaois "yy
“VuIRy ‘mINNOIYea soovd ur
winner | ontq fueedS | morjeé wnynoryer
f anyq-aorpad ystaopja£ fonjq guoavd
punoas *y, punoas “J, -suvay oped *y,
pur ‘uy worsad [THD

"UOISad [ILS qynoqe “g00u Ayarez
pue ‘gue “goou A[jnz jou ‘onyq yu

£UMOIG PUTT
arvdsuvay oe

‘par yaup
mnnoyet

£punoas

ystumorq “YT
pea unjnoros

£ moypoXk

ayud anojoo
puno1s *y,

UAOIG
WIR AA

mOOU.A4 FB
UI SB yromgou

pot asojo

Mou f pad
&q paovidoa
Saag suLoas

“Y90T “md 086

“we 08'S

‘U40L “suy

(x10mjou
qsinyq

up) anqq

atud ‘e043

—_— Ytomgou ony) ystmoyjos +7,
ad aly qS5'H
UMOAG u0018
yang UMOA ysiniq
“quod sapuRour “wid OL

urm g—g LYyV

‘qysta Sulinp pred

§quoredsurag you £ u90dS8-oAT/O |
YAwp JUEM UWOIYVAIOSqO Jepuy

*SUOTZBIPRL
ony Furey YT on FySIAq “yY

*suo1qe
-IpBI ONT FUIVF puv soTey youry
-sIp yqIa sjods onjq osavy ZL,

sjods ony{q "yy

OTBy yourgstpul
YqtAy “Tp BUIs
souduavo 10

‘e 10 Z ‘Maz “I,

au0u
10 9[941'T

uMOIg

‘mdg

*jeuanqoou Fo Lr9aodaa 4yLSts (ura OZ)
aul} EWOS JOIZB f YOO[I,O J AV AozVA YT YLep ur youg gud

05°6 patiwmexg ‘oaniq
ssay f1queat3 fyua1edsue.ty aout 2)
aka paxeu 0} A1aA0da1 OU 08'6 IV

‘wd CP's

*o0I—8 98 dojem Wl 0g'6 38 PIRI (T)
‘urd 9g"6

|

“ure 0g'8
“W401 “SUV

T oansodxo eyo} £ paseo
‘urepeodod ut oou0 4v gud “qry

‘urd e101 “urd OVO

“S5I[ JUaoSapuRKoUy

ystumorq AJourystp Surut09eq sv
4I ftojzv soqnuiM QT poulmexe * oqnutot

wey} “qstp
opUL FYSNog

[jvus Z

IMopoo punoas
o1dooso.01 yy

fouoaed
SURAT,

Inojoo
[erouer

‘aut ory & (,)

aka MOTEq T
pus puryeq T
‘apis youe uo
sjods onjq Z

‘aga

“QULT} “MOT4VA

-rasqo Sutanp
acuvyy

sjods oniq

‘w'd OL

ee

‘ad ¢

‘(ponuljuo0d) GxoOoTY ANOLOY AO WIdNVXUf

657

HIPPOLYTE VARIANS.

“9UlI} UOTywAadtosqo

pa.aaa00
Sump paraaooaa | SV Sty
A[repnoraed yon —_ peorday

| sqoqq anqq
YI} UI spua pa sosva
‘sojonova ystmorjes | autos uy ‘woaryo par en{q

WII s.10y40 “ontq d10Ul 10 J UI SuIpus AY Si1q “37
TIM amos “ped Yrep “yep Soaar ontq aqSqy “yy qourystput
*sassoooid sossao0id SUOTJRIPVA

YStMo]ja£ yoryy gatos

Ontg I STT GIT ‘soyey Yaup
TM “paa Yap 7

‘asavl ‘snotemnu “J, |yoelq-antq “J,

sayoqed
studels uvyy
Iasiry yng
SuIplwuUrood
‘satfoqo[q,
ystusars
IV[NGITAL YIM
twanynoMat
‘pat "7
sayoqud
*soponova ystmorjek £41248 soyouesq ystuaais
aNTqA YOM wos ‘sopvy ontq YIM pea yaep “y YIM pat
“YORlA “pozowrqgar *mMoayo * J |‘ozepNoyYo1 “iL

THOL “wd 0g'6 “WHOL “mre Og'g |

skaprpe yy
UMOIG PUT
BI94SO7 040 ‘awly
ueais “MOIQBA.LaSqoO
V | a9 fore Surmp
pewaoouy) |AS{q ur gnd puv peraaooug|! 4e paaaao0g sosuvyg
satpuviq ontq
YO Surpues osye ‘pat soys
-asioy JO pua £ suolzenorqea
aniq ‘sayouviq sSuryerpet
auy YyIA. gods ontq eoys
-astoy B fsqo[q pax o10ut
to g Ul Sutpuea [je Ajrwou “y) aay pus
Auryq YOR]G-on[q Yavp *y| snoswny | sgods ong
so[ONOvA
poepurdxe mood
A[qu.apisuoo ou ‘paa YIOMZou
“MOLY “UIU |‘paqgovaqgad yy aso[o
as G—T 109FV | pot Yup, | Surmtoy pay} *moryy
|
aesepimy) wor wde

‘aut ogg & (,)

658 F. W. GAMBLE AND F. W. KEEBLE.

Taste I.—WEED

Piel, July 29th, 1898, Flask A, Air Circulator.—Hippolyte varians
behind Piel Castle. Weeds at first brown, then green,

July 29th. July 30th. ‘ July Bist.
10 a.m. 9.30 p.m. 1.15 p.m. 3 p.m. 10 p.m. 9.49 a.m.
aa ers |
A. @ fasci- | Transparent Very | Light clear | Faint olive- | Faint olive-
gera, light | pale blue-green | transparent, | brown brown, not | — brown
brown (nocturne) greenish; | bluish
head and tail
brownish
B. 2, dark Transparent | Light blue; |Added at 5 p.m. Light Greenish
brown with | light blue, ant. dead (Sa odark transparent blue ;
white mid- and hind olive-brown ; no| blue; brown | extremities
dorsal line |brownish (semi- white stripe | at ends of brown
nocturne) body
C. 9, dark Blackish ; Dead; y. 2 light Light Clear dark
brown, almost pleura of bluish in mid, jolive-brown; no} transparent | olive-brown
black, with | abdomen trans- white stripe | blue; brown
white dorsal] parent blue at extremities
line
D. 9, light | Light trans- | Light olive- = Light Dead;
olive-brown, | parent blue; brown transparent | opaque; light
without white|brownish at ends blue; faint blue
line of body brown at ends
of body
E. Small, dark Fairly Dark blue — Transparent Dark
blue transparent ; dark blue | purplish
clear blue-black brown; blue
| at margins
F. Small, blue- Bluish Greenish _ Light | Greenish
green brown greenish blue — brown
G. = = = = | =
H. Weed Covered with | Uncovered Weed changed;) 6 and y dis- — Weed
Halidrys;| black cloth /green Entero-|tinctly darken changed;
flask left | morpha and | after 2 mins. brown
uncovered | Ulva added | exposureto Dictyota
gas-light; | and green
| covered Ulva;
| uncovered

HIPPOLYTE VARTANS.

Cotour Hxprriment 1.

and the variety fascigera, taken from Halidrys in Bass Pool,
then green and brown, then brown, and lastly red.

July 31st.
10.15 p.m.

Transparent
pale olive-
brown ;
slightly green
in mid.

/Ant. and hind
| brownish ;
mid. clear
deep blue

Dead

Dark brown ;
blue at sides
of body

Dead

Covered

10.15 a.m.

Semi-
transparent
light
brown

Ant. and
hind dark
brown ;
mid. bright
green

Added

mauve

Opaque
brown with
mauve
tinge

Covered

August Ist.
4.15 p.m.

Ant. and hind.)
light brown ;
mid.
brownish
green,
especially on |

abdominal |
pleura
Ant. and hind
brown; mid.
semi-
transparent
greenish
brown

Transparent
light blue ;
margins dull
mauve; ant.
and hind
dark reddish

Added
Small green

Opaque dull
greyish
brown;
mauve

margins

Ulva re-
moved, now
only brown
weed. In
evening ex-
posed to gas;

uncovered

10 p.m.

Ant. and hind
brownish,
semi-trans-
parent and
bluish on
pleura

Very trans-
parent blue-
green to tip
of body (full
nocturne)

As at 4,15

Green

Greyish
mauve; sick ;
moulting

Covered

August 2nd.

7.15 am. 10 a.m.
Transparent | Full
light green | brown

and brownish
extremities

Vivid trans- Full

parent green ;! brown

faintly brown

at extremities
Transparent | Pale
light blue, mauve
with trace

of mauve

Yellowish Bright

green green
Dead Covered

Exposed to
diffuse light
till 10 a.m.

2 p.m.

Tail to hump
brown ; rest
of body |

greenish blue|

Greenish
blue; espe-

cially blue

anteriorly

Mauve, with
blue tint ;
transparent

Bright green

Exposed to
diffuse light
2—2.30

660

F. W. GAMBLE AND F. W. KEEBLE.
Taste I.—Wurp Corour
August 2nd. | August 3rd. August 4th.
2.30 p.m. 4.15 p.m. 4.25 p.m. 6.25 p.m. 930 am. | 3.5 p.m. 2.5 p.m.
A. Light Transparent Brown, Unchanged) Brown Brown, Brown
olive- green-blue | except for | fairly
brown ; (nocturne) ; |trace of green trans- |
no green, tail faint | on hump and parent
slightly brown 2 patches |
trans- behind eyes |
parent
|
B. Dull Nocturne ; Brownish, |Unchanged Brown Brown Brown
greenish | tail greenish | fairly trans-
brown brown parent; dull
in front; green in
hump faint mid.
greenish;
behind
brown
C. Darker Nocturne; | Mauve-pink, Bluish Bluish to |Full blue Dead
reddish tail faint no blue hump, (sick)
mauve, pinkish behind
not blue reddish grey
D. Bright Bright green| Bright green| Bright | Light green | Light | Dull green
green green | green
E. Covered Exposed to | Put in dark | Uncovered Uncovered Un- |Left in white
2.33 diffuse light | 4.30, at 4.45 6.30 9.35; fresh | covered |porcelain dish
4.15—4.25 | exposed for Dictyota with scrap of
2 mins. ; (brown weed) weed till
no change; added 2.40
re-covered
4.47

eo ;

HIPPOLYTE

Flask A (continued).

EXPERIMENT 1.

August 4th. August 5th.

2.40 p.m. 10.30 p.m. 2.30 p.m. 2.32 p.m.
Dull brown; |Transparent ;|Uniform dark} Greenish
behind hump,| light bluish brown tinge
and antennal| green; ant.
scales green and hind

light brown
Olive-green | Same as A Clear =
“Fucus
brown ”

Bright Transparent | Dull green Bright
transparent greenish green

green

Light Brown with | No record |
bluish green,| green mid. |
transparent ;
light brown
ant. and
hind
Yellow-brown
Brownish, Grey, Behind eyes | No record
freckled with] transparent;| dull brown
white antennal
scales

freckled grey

VARIANS.

August 6th.
6.25 p.m

Light brown

Mid.

greenish ; ant.

and hind
brown

Record
closed

Greenish
yellow |

Tohump |
dull brown, |
behind hump
dull grey-

brown

Uncovered

Brown weeds} Uncovered Uncovered |F examined
taken out and put in micro-
and red porcelain dish} scopically ;
Odonthalia for 2 mins. | uncovered
put in ;

uncovered

August 7th.
10.30 a.m.

Record
closed

Brown,

darker on
tail; hump

greenish

Record
closed

No change

Uncovered

August 8th.
3 p.m.

Dead.

Dead.

662 F. W.

GAMBLE AND. F. W. KEEBLE,

Taste I].—WeEeED

Flask B, Air circulator

July 22nd, 1.30 p.m.,
not covered.
|

ee

\a. 2 deep brown
with long white
stripe; had been on
Ulva; under
circulation 3 days

b. 2 deep brown
without stripe,
from same bottle

e. Q fascigera
greenish

d. $ green with
reddish stomach

iss)
:

4 small green,
from Foulney

Scott said
had shown
transparency and
recovery effects ;
not covered

25th, 2 p.m.

26th, morn.

27th, 10 a.m.

Dark brown white
stripe

No change

Browner

Delicate brown
tint of finer brown
weed

1 bright green,
2 green

Covered

Bluish above egg-
sac; rest deep brown;
recovery

Recovered

Transparent parts
bluish

Light
transparent
greenish brown

Not to be found ;
eaten !

Covered

Dark brown, white |
stripe, no blue ;
recovered

Recovered

Browner,
darker

Dead

_ Covered; brown
| weed replaced
| by Ulva

|

Cotour ExpPErImMeEnt 2.

HIPPOLYTE VARIANS.

with brown weed and little sand.

663

28th, 9.55 a.m,

Bright |
transparent blue, |
except antennal |
scales and tail: not
green; nocturne
effect persisting

Like @

Like a and 6

28th, 2 p.m.

5.10 p.m.

Covered ; Ulva
replaced by |
brownand |

adhering red |
weed |

Dark
brown

Dark

brown

Light
greenish brown
(no blue)

Covered

Transparent blue |
except antennal
scales and tail
which are brown;
long persistance |

of nocturne

Light olive-
brown, no blue

Seales and tail
light brown:
green and blue
in middle

| even to antennal

Uncovered

29th, 9.15 a.m.

Transparent blue |

scales

Dead ;
light olive-
brown

Light trans-
parent greenish
brown, not blue

Covered

Green-brown
with white
stripe.

Light brown.

Covered.

664 F.

July 29th, 5 p-m.

W. GAMBLE AND F.

W. KEEBLE.

Taste II.—WeeEp Cotour

Flask B, Air circulator, Weed

9.45 p.m.

a. @ greenish
| brown, white
stripe

brown,

e. Small, semi-
transparent,
faintly red hind
(added)

d. 2 small
brown
(added)

e. Uncovered,
Delesseria

Bluish flanks and |

pleura; greenish

rest, except brown
ant. and hind

6. Dark olive- |

without stripe |

Brown ; pleura
not greenish

Reddish limbs ;
bluish about

10 p.m.

81st, 9.20 a.m.

Bright green,
except ant. and
hind. brownish. |

except limbs and |

carapace blue

carapace

2 greenish

Covered

| Transparent blue,
except ant. and
hind. brownish |

Dark brown,

except pleura and
margins of

carapace blue

Transparent,

red lined

1 semi-
transparent,
brownish

Uncovered

Bright olive-
brown, not
transparent

Dark olive-
green

Reddish lined ;
sick, pickled

Unaltered

Uncovered

Experiment 2 (continued),

HIPPOLYTE VARIANS.

Delesseria, old and greenish.

10.20 p.m.

Aug. Ist, 10.30 a.m.

10 p.m.

665

Aug. 2nd, 7.20 a.m.

10.5 a.m.

Dark brownish
green, semi-
transparent

Dark greenish
brown, semi-
transparent, not
bluish

Added 2 under-
sized bright
green, with

eggs

Light brown,
semi-
transparent

Covered

Hind greenish
brown; ant.
brown behind
eyes and pleura;
nocturnal blue ;
rest of body
brown

Dead;
put in 70 per
cent. alcohol

No change

Transparent,
light brownish
green

Uncovered; |
removed
Delesseria;
added fine red
and brown
weed

Bluish green,
fairly trans-
parent; dull
brown hind and
ant.

1 small bright
bluish green,
and trans-
parent; other
lost

Pale greyish
brown,
transparent

Covered

Transparent
green; ant.
and hind brown

Unchanged ;
sick

Pale brown
with reddish
tinge

Uncovered ?

Full brown-
white line.

Full
green.

Faint brown,
transparent,
with only
tinge of red.

Covered.

iE

Aug. 2nd, 2.5 p.m.,
after dark.

a. ® large brown-
white stripe, full
brown

a

9 with eggs,

green, small;

blue-green on
tail; dead

Small green
(added)

©

Medium-sized
brown, faintly
reddish

es Put back in
dark, 2.10 p.m.,
Aug. 2nd

Tank-room, Piel.

Aug. 2nd.—Dull, cloudy, occasional sun.

W. GAMBLE AND F. W. KEEBLE.

Taste I1.—Weep Cotour

Flask B, fine red

4.30 p.m.

4.45 p.m.

6.30 p.m.

Brilliant blue-green,
except ant. and below
hump brown

Transparent green,
middle bluish

| blue-green ; tail

behind hump blue

Exposed to diffuse
light, 4.35 to 4.45
p.m.

Aug. 3rd.—Cloudy all day, with rain.

Transparent, delicate |

Dull green-brown at
sides of white stripe ;
brown parts darker

No bluish tinge, very
transparent

Less transparent,

| dull pinkish brown ;

tail reddish

Put back in dark
4.45 p.m.

Head to hump
green-blue ;
behind hump and
ant. scales brown

Transparent,
especially in front
of hump

Trace of blue,
behind eye; more
transparent ; loss

of red

Put back in dark
6.35 p.m.

Colours examined by pouring all contents

HIPPOLYTE VARIANS.

HxPERIMENT 2 (continued).

and brown weed.

607

Aug. 3rd, 9.35 a.m. = 10.80 a.m. 3.10 p.m.
Head to hump brilliant trans- Diffuse light; after 3) Ant. scales brown; Brown-
parent blue; behind hump minutes’ exposure behind that dull | white
1 segment greenish, rest blue lost; now green green; behind | stripe
greenish brown ; antennal with dark blue spots, hump brown
scales brownish red; white, with great disposition
| mid-line; eye-stalks blue-| to take cover under
green; eye black red weed
Transparent, specially in mid,| No noticeable Unaltered Green,
green change not very
bright
Very transparent; behind) In 4 minutes reddish Less Transparent,
hump, ant. scales, and eye- tinge lost; ant. transparent faint,
stalks reddish; mid. pale) scales only faintly reddish
ereyish red reddish
‘Exposed in white porcelain dish to diffuse light till) Added from circu- | (fly ery:
10.30 p.m. lator air dish with | | transparent

Ulva, 2 small green
specimens (Ulva not
added) ; put back
in dark 10.35 p.m.

ee

bright green.

Smaller,
bright green ;
put back in
dark.

into porcelain dish, using hand-mirror, Fresh water added after each examination.

|
|
|

668 F. W. GAMBLE AND F. W. KEEBLE.

TasLe I1.—Weep CoLour

Flask B, fine red and brown weed (after dark). Started Aug. 4th,
Weed red, delicate

Aug. 4th, 3.10 p.m. 3.50 p.m.

a. Showed nocturnal tint. Was at once decapitatedjc. As before
by cutting off the head close behind eyes. Ant. and
hind brown ; mid. transparent blue-green. Hand-lens,
ground colour light bluish green; numerous brown
chromatophores; large “blue spots” with clear space
round each; smaller blue spots without clear spaces.|d. Transparent, faint reddish
Reacts violently to touch of tail (and occasionally spon-
taneously) for more than 5 minutes. In 5 minutes
loses transparency. Belly first to darken. In 10
minutes brown chrom. on the belly (which is now quite
brown) form under hand-lens reticular patchwork,|? uniform dark brown-black.
with occasional blue spots. Reacted to stimulation of] Chromat. not distinguishable

tail after fifteen minutes (hand-lens) ; no blue spots
Dorsal surface of mid. remains somewhat transparent]? dark brown white line; no
greenish chromat. nor blue spots (with

The head cut off: young Hippolyte anchored on it, and} lens)
apparently ate some of it

Rest as before —

Weed changed; new specimen added; left in diffuse

light

e. f. As before. Put back;
left uncovered

EXPERIMENT 2 (continued).

HIPPOLYTE VARIANS.

669

3.50 p.m., with four specimens from Flask B., Aug. 3rd, at 3.10.
plumose after diffuse hight.

10.30 p.m.

Aug. 5th, 3 p.m,

2 small
transparent
nocturnes ;
PAO QS IP

d. Very
transparent,
dull brown,

not blue

blue, trans-
parent ; hind
and ant. light
brown

1 small
brownish ;
dead

Put back ;
uncovered

Nocturnal light

d. Bright
reddish

Dark brown-
black

Dark brown,
almost black ;
no chrom.

e, Transparent,
blue-green ;
examined
microscopically

Ff. Dull green

"Uncovered

6.30 p.m. Aug. 7th, 10.30 p.m. Aug. 8th,3 p.m,
(Bitten) == pone
eaten
Dark Unaltered Brown-black

brown-black
Dark brown,

almost black

e. Bluish
green

Brownish
green

Uncovered

Dark brown,
white line very
clear

Dull green

Uncovered

(1).

Dark brown
(2).

Dead ;
casting skin.

Put 1 and 2 back
with green weed
and Halidrys
(see p. 655).

von, 43, PART 4.—NEW SERIES.

AAA

670 i. Ws

GAMBLE AND F. W. KEEBLE.

Taste I1I].—Weed

July 26th.—T wo large ? Hippolyte varians and one ? Spironto-
latter claret-coloured mid., and opaque speckled patch on head ;

July 28th, 10.35 p.m., | 29th,

after exposure to light. | 9.45 a.m.,

Weed—Zostera. | after dark.
oe!
rca
ile Large 9, Semi- |
perfectly trans- transparent)
parent, and _olive- green
blue to tips of (w hite line)|

the tail

2. Ditto Ditto |
(dark spot |

on back)

3. SS. pusiola, | Perfectly

very transparent ; transparent)
colourless eggs
showing clearly
through dorsal
surface

Put into dark Left in

light

29th,

5 p.m.,
after light.

Light
olive-
green ;

fairly

transparent

Ditto

Very trans-
parent,
but now
slightly
bluish

Put in
light

™.,
after light.

Clear

itransparent)

blue

Ditto

Unaltered ;

bluish

Put in
dark

|
| 30th, 10 p.m.,
| after light.

> Bright green |
to tip of tail

|
|
|

Mid. bright
green; ant. and
_ hind brownish

Very trans-
parent, slight |
bluish

Putin light |
12.30—2 p.m.,
both 1 and 2 on}

stem of
| Zostera and
exactly
| matching the
colour. Put in
light

|

30th, 3lst,
10 p.m., 9.15 a.m.,
| after light. after light.
Perfectly Semi-

itr ansparent|transparent

| light blue bright
green
Perfectly | Duller ~
transparent; green,
| light blue, | brownish
except jon ant. and
ant. and hind

hind tinged
with brown

| Unaltered | Unaltered

Put in Put in
light light and
in slightly
| slower
current

ee

HIPPOLYTE VARIANS.

Colour Experiment 3.

671

caris pusiola trawled. The former were both greenish brown, the
left for two days in light and under strong current.

3lst,
10.35 p.m.,
after light.

August Ist,
9.30 a.m., after

light.

| Ist,
| 10.30 p.m.,
| after light.

2nd,
7.45 a.m.,
after dark.

Light blue-
green; not so

perfectly
blue to tips
of body as
last night

Light blue;
transparent
except at
ends of body,
which are
brownish

Unaltered

Put in light

Greenish yellow- |

white stripe

distinct ; semi-

transparent

Clear greenish
yellow ; tail and

ant. scales

brownish, exact
colour of lower
part of Zostera;
semi-transparent

Unaltered

Put in light

|
| Very
transparent,
light blue ; |
very slight
brownish
tinge on
| ant. and
hind

Ditto

Unaltered

Put in

dark ;

weeds,

| Zostera
and

Entero-

| morpha

Trans-
parent pale
ereen ;
behind
hump faint
brownish

Trans-
parent
green; ant.
and hind
brown

Unaltered ;
still very
trans-
parent, and
only a
bluish tint
on tail

Put in
dark

2nd, 10.10 a.m.,
after dark,

Zostera.

2nd,
10.30 to 12,
in open.

Fairly trans- |

parent bright
green

Fairly trans-
parent dull
green, except
behind hump
brownish

Unaltered

10.80.—Taken
into the open,
sunny; added
Bryopsis;
temperature of
water 20°5° C.;
small yellowish-
green Hippo-
lyte slipped in

) with the weed

Green,
transparent
(brilliant
blue spots
on cara-

pace)

Trans-

parent,
duller
green

Unaltered

Left in
light with
Bryopsis

2nd,
7.15 p.m.,
after light.

Perfectly
green and
trans-
parent.

Quite
green and
trans-
parent.

Unaltered.

Put in
dark.

672 F. W. GAMBLE AND F. W. KEEBLE.

Taste [1V.—Weed Colour Experiment 4.

August 8th, 1898.—Experiment made with a cylindrical
glass jar filled with Delesseria sanguinea and placed
on grass in the open. First half-hour bright, very dull
subsequently ; water circulation maintained during expe-
riment. Commenced 12.20 p.m.

12.20. 4 p.m.

(1) Colour... $< Semi-transparent Bright brown.
greenish

T. No ground-colour _ T. Yellow ground, with
| close red network and
| green patches
| T. Chromatophores
red, fully expanded
R. Yellowish-green R. Ground brownish.
ground; fine yellow
network

Microscopical
examination

(2) Colour Green Dull green (dead).
|T. Green ground colour, T. Chrom, red
Microscopical yellow network, branched 3 in anterior
cee ation chrom. red region stellate.

R. Chrom.red branched R. Chrom. stellate
green.

(a EN ; a eT

GAMBLE AND F. W. KEEBLE.

W.

F.

674

JUST esngFtp 09 posodxa

ystp urvjootod ur pooqg
ystusads

qqst quoaedsuvay Atoa %

(dtap tapun 4yory)
(4{[voidooso.worut
pourmexe ‘poulf-uedts T)
aUAINJZOOU-1WW9s T
sour
-00u ][NZF Juordsuvsy G
UMOIG YAVpP T
ont YAVp T
(wa0a3
qstfors dummy pur ‘se[vos

(ju090

-sopuvour 03 pasodxa
ystp ulepooaod ur 4jory)

WITS SIM] 4S]
queavdsuvry capulvu1oy
«HOUT ,, W0Isd T

(Wo1gBAdaS
-qo Sulmnp anojoo yYSst
-udaIs 0} d5uBYO 9M0G
‘YsTUdALS G 4svaT 9B nq

UMOIq 1

so[vos [vUUIZUe
pepyoods 441M “ystuses Z|
UMOIG YSIS T
ua0d5-MOTOA T

‘drip saoys v ur 4j0] Buteq
1yJ¥—"W'? CT TL ‘QL ystony

*quaDSapPUVIUL 0}
ainsodxo [uj toyyy—'"w'd Gp'6

jUdISOpPUBIUT SaqnUI G OF
pue ysip uiejeotod ur 4ystpAep
0} aansodxa ta3yy—'w'd g

-o010g *0 {UI[SNUI YIM 1oAO [[V podoaco aul ssuly) “a
joj oyur orngdvo jo yuomow 4v qnd orem sumed oy,
‘avejo ktea you soqem f-urd g—FpP “oury,
purv ivog oY} Worf SAY popMUd SUBIABA oykjoddipg yo suowtodg—‘ggg] ‘9[—G] ysuony ‘Tord

‘yystpkep Xq stp urejaosod
ur ‘urd gE) (AroqRioqry
0} SUIMINgoL WO) PouUMeX Ty

UMOIG YSItoets [[VUIs Z\que popyoeds) uses T (peppeds soyvos |4uryy umorq ystXous UMOAg-MoT[ox T
UMOIG YSIUIIS T user |[eauoque) uasors-onjq T|}Uuoredsuery v Jo [vsoacg) MOT[OA-.490 T
UMOLG JUST T]fo 90v19 WIM § UMOAG T an{q YAVp T peuly-yor[q T YOV[Q-UMOAQ [[BUUS T;

UMOIG AVP T auIny quoredsura4 UMOIG Yacvp [[wuUIg & Yovyq
& UMOAG-PAT[O Zj-oou uaers-on{q [NF ‘Ss T\-1wes ‘S uaais-antTd ZF 6 UMOAG YIVp Z-UMOIq Yep ooary Z!
= = a
“4ysly |

‘uado Surpurys
‘rel sseps Uva] Uy “Vv

-I9A00 Yourq yA rel pousyoeg “a ‘1000 urpsnut yy god urey

‘T guowmisodxg

PRECIP Ted

"KLISNTIN]T LHOIT—'*A #TAV,

‘aul sseps avo[Q ‘V—! s[essoa yUorIOyIp
“Mol “yours opty {Apnojo ‘avez aoyyvom
aeou ‘poq SAIpIl[Vy, oy} Wor uwosyy

675

HIPPOLYTE VARIANS.

UMOIG IY SI] Z
TIUTT-ONTY FYS!Y T
(sapvos
pepyoods) udeaS-aatjo § T
use1s yep AoA T
90S ISI] Z
udaLS FYSIIq Z
DANVOL T
(qsor 3 T)
quorrdsuvay
-Iules “Ueeds 4ysi, ‘Sh T
« dumny ,, puryoq
uMoIg fuses yaup Sd T

ssopNo[oo
qsomye ‘quaivdsuray A120 T
dtp ¥ tapun gyory|4gsoue “uoredsuvag A109 T porieq-an]{q T
ssapInojoo “quoavdsueasy T udeds gy Staq T\wse1s yy SI] gueredsuvsy Z
udeds-an{q Yap Z\(seyvos pepyoods) ysmyq T uUMOIG FIVpP T

(soyeos | ua0a8-on[q quorvdsuvay F antq onbedo {

pe[yoeds) onjq Yystusets T UMOIG-Ud2IS YAVp Z| m9018-an]{q E
U9dIS YYSIT G PANVUL [[VUS Z aAnVU Z

(yarep) onyq Yystusde1s T [eumyoou uears ystutq ‘4
eaneu ystmniq giAysys ‘amoriq ‘6 T udois yuordsuray ‘5

seuanjzoou [[nz ‘Ss g saurnjoou ays‘ s Z yoryq-onyq ° 4

Sso[Ano[oo

“dtp UL yJoT—' Ue 6ST TL

‘(ponuryuoo) [ yuowmriodxg

“yuaosapuRout
Jo Mopeys ur urepoor0d
ur yjaT— ‘wd 09°6

"SUIM GT Joy JWsosopuBoUt
pue 41psi,kep 0} posodx9
Suloq 1oysy—'ur'd OTE

“MOTjeUIMeXE SULIMP
‘qsip urepaoiod ur 4ysttdep
0} pasodxm— ‘wd g*y

deois JY SIT T
umoiq-morad Z
ugeas-mojfak T

UMOIG YSIMIaLs T
UMOIG Gg

pele

ugats-aATjo yaup 6S T

yoriq-umoaq 4 Z

“UI[STLUL JO
JOA00 PUL FI PUNO WIsNnUT
JO ploy UO T}LM “Ael ssKPy “

‘ALISNGIN] LHOIT—' A AAV,

KEEBLE.

GAMBLE AND F. W.

WwW.

F.

676

Sul
YIM pasar ‘patieg-yov[q |
potieq u9e5-9AT[O |
UaIS FPS T
woeei8 yuiez AOA T
WIIIS YSIUMOIG Z
(sofa puryaq
qsnf ueo18) roury ysttdand T
SANBUL YSIN[q T

AANVUL

qurey “uotudsurty AoA T
quorwdsurty

you fuses ysmntq ‘S T
quoiedsuvty

jou fyeurnjoou-tmes *s T
qso] T pus pvop 6 T

(auoyoo
[eurngoou [NF ley
JO aUOS 4SO] aseq} Uu04
-BUIULXO SUIIUp 4yuaosep
-uvout 03 posodxa ott A)
¢¢ POTIVG-ONTY 5, ]
SOTPIWIIAZXO JV UMOIG
Jo 90819 YIM “WdaIs-an[q T
JANVU JO
aovly YQIM Quoaedsunsy T
OANVUL
a0vlg jim ‘aniq T
udaI1S-9n]q
yqst] quorvdsuvay Ar0A F
(a.sury ysTUAMo1q
FASS yILA ouo0) yuornd
-suviy “Meers-ontq ‘hb Ff
soaurinjoou [[NF [LV

fo

patavg-use1s Ys] Z%
JOU] WIAs T
W9d18-an]{q [BUS T
aAnBUt
pee
quorvdsuvay AtaA ¢
aU.inyJoou T
umorg yyst fs T
quorsdsuvay
‘aaais-ontq “4 T
auanqoou [Inj ‘4 Z

you

porteq-ontg
an[q ystuse1s

uotdsuvsy gyurey “yuoredsuvay As0A §,

@ANVU O9BOITAP T

[VuaIngoou [[® 4sey
*plut ul ueeIs Jo

a0el, YIM ‘umomq ‘4S T

Ting Ajavou $& T

sournjoou [nj ‘sd Z

¢¢ POTIVG-FYOVT 5, T
por Fo osury

quia ‘Aors yuorrdsuvsy T
(sofa puryoq

qsul moras ATQy Sts) por T

<< SHOUT[-Por ,, Z

MOTOA [[VUIB T

mopjak 4qSt] T

uMoIq-MOT[OL T

& Yovlq-umoaq ¢
& YOVlq-Ys!waaty

“I9A09 UT[SNU 0} TO SUISURY
PUP 4YSIT 0} SurpModo |[vus Z
pus & aie] G) Wee OS TL

*yuaosopuRout
qoolIp wo. papeys ‘urefaoiod
UI poo}ys peH—‘ard /p'6

*SUTUL QT 10J
quaosapuvoul pue yysipkep |
0} Ystp utejaorod ut |
pasodxa naeq pey}— urd ¢"g |
|

*KIORIOGR] 4B
[PALIIe uo “td J ynoqy

*19A00 UITSNU
LM jyod wiejaoriog *9

‘(ponutyuod) [ yuowtsedx a

“ALISNGIN]

LHOIT— A Wavy,

677

HIPPOLYTEH VARIANS.

4ST asngz
-jiIp UI urepeo10d ur pooyg
yuid |
poareq-yoeyq T

spueq ysraneut
qurey yyIM ‘guoredsuvs T
MoT[Ad FUSIT T
UMOIG YAIVP T
UMOIG WAIL [[VUIS T
UMOIG YSIUIIS ¢
udeais-aATlo yrep 6S T

soul
“yeu =: paatno[oo- Apurs
qjIM = ‘punois = uaa

ystumorq ‘6 Balaclosey

“wre GSI

(aystu
Sutmnp diap aapun 4jery)
aAntut oped T
[YER E
JANVUL T
paqteq-oelq T
udets-an|q YIVp T
udeds
qys1] juoiedsuvyy Ar9A T
WddIs ISI] F
quoredsues
A19A Jou ‘usars-en[q ‘sh |

aANvUL
Yysmyq qurey Quoavdsuvay Z
JANVUL T
|. podaeq-HOvyTq,, [[VUs T
(sa[Bos
pepTyoeaz) oonyq yarp T

an[q YARp T
UMOAG YSLMOT[a4 T

UddIS 19YIVp T
wae
aystt queavdsuvay A190A Z
UMOIG JUST T
suLS
|-1vU UWeets-onTq yusted
-suvay fuMmorq yaep ‘Ss T
UMOAG YStudseIs pury
fdamy 07 uaeu8 §yuored

(suet aaqgo
oy} FO sqzuequod oy
uvyy pasuvyo sset Yony)
pet ystanvur ¢

paling Vlg

antq
ysiusers quoivdsurry Z

UMOAG YSTUdeIS J
MOTEL T

UMOIG YSTYORyq T
ysinyq A[gy sys‘ 6 usorg T
az M FILM pepyoods

poreqjvun ‘4 viloStosvgq-suvy ‘4 waostosvg|‘etocrosey & umoiq T
"ecg “aul, Jo jed V omaial ane ‘md p
MO[Aq ULepeoL0d UI pooys peyT , S18 qe ATOJRAOGRT UT [VALLIG 19FV

pat ¢
« P2LIBG- OBIT 5» T

(seTvos

[vuuequB papyoods
YIM) uMoIg YsTueeds JT
uoer8-MoTok T
umorq-Mo][ak T
porteq-pat T
Mood T
umorq oped T
UMOIG Z
& woers yarep T

& YOvlq ysourys T

“ref poiaaoo youlg *a

‘(popnpouoo) 7 yuowlsodxg

‘ALISNHIN]T LHOIT—*A WIV],

678

F. W. GAMBLE AND F. W. KEEBLE.

TasLe VI.—Licar lyrensiry.

Aug. 22nd, 1898.—On comparative effects of exposure to red,
glass dish on black plate), and transparent jar containing

tank-room.

Morning grey after occasional bright sun.

water frequently changed. Experiment

1.5 p.m.

A. Mid-sized, ight brown
Microse.—
T. Ground yellowish
Network red with green patches,
Chrom. well expanded, red
Blue spots many, big, no halos

B. Large, brown

T. Ground red |

Network close, red, with green
patches

Blue spots few, slightly arbo-
rescent, with halos

C. Mid-sized, full brown

YT. Ground yellowish
| Network dark red with green|
| patches
| Blue spots arborescent, without;
| halos |

D. Mid-sized, greenish brown
T. Ground yellowish green
Network none
Chrom. fairly expanded, some
green in centres of chrom.
Blue spots not arborescent, with
halos and distinct radiations |

E. Similar to A
Network only in mid.
Blue spots arborescent; in mid-
line with halos

Put in red light
12.20 p.m.

Put in green light
12.25 p.m.

Put in green light
12.25 p.m.

Put in blue light
12.25 p.m.

Put in black jar
(with black cloth
cover)

| Good nocturne; very

transparent.
Network blue.

| Chrom. fully retracted,

_ red, with blue branches. |

Blue spots with

| distinct blue radiations
crossing halos

1.5 p.m.,
very dark brown

|
| :
|
|

1.5 p.m.,
dark brown

1.5 p.m.,
nocturne

1 p.m., transparent
greyish, as if greenish
through brown.
Ground light yellow-
brown. Network half
green, half red. Chrom.
half green, half red

Hxperiment 2.

green, blue lights, darkness.

Microscopical examination by daylight.

HIPPOLYTE VARIANS.

679

White (porcelain dish), black (a
sand. Hippolyte had been in drip from 18th uncovered in

lasted till 5 p.m. in open, then in laboratory.

2p.m.

3.20 p.m.

Light brown ;
trace of green
behind eyes

2 p.m.,
dark brown |

2 p.m.,
dark brown |
|
|

2p.m.,
; good nocturne; |
| recovered
| immediately
| during examina-
| tion in porcelain
| dish
|

2.30 p.m.,

Put in blue
at 2.30 p.m.

Put in red at
2.30 p.m.

Put in red at
2.30 p.m.

Put in green at

2.30 p.m.

Put in

\Brown with faint)
| trace of green
|

3.20 p-m.,
dark brown,
almost black

| 3.20 p.m.,
| brown with tinge
of green

|
|
|
|

3.20 p.m.,
light brown

3.20 p.m.,

very transparent ; porcelain dish very transparent,

slightly greenish
| in mid.; brown |
ant. and hind

at 2.30 p.m.

| light brown ;
tinge of green in
mid,

4.50 p.m.

Greenish
brown

4.50 p.m.,
dark brown

4.50 p.m.,
nocturne in mid.,
ant. and hind
brownish

4,50 p.m.,

yellowish brown |

with trace of
green

4.50 p.m.,
dull green;
ant. and hind

brown

|
|

R. not possible ;

7.5 p.m.

Bright green
mid.; brown
ant. and hind.

Nocturne.

Nocturne
(recovered
1 minute or so

during examina- |
tion in porcelain |

dish).

Nocturne.

No record.

680 F. W. GAMBLE AND F. W. KEEBLE.

Noon, August 22nd. |

F. Mid-sized, brown ae 1.5 p.m.
T. Ground yellowish brown (had jumped out),
No network /| greenish brown
Chrom. fairly expanded, some 5 :
ereen in centres | Put in glass dish on |
Blue spots small, slightly ar- Seay a plate
| borescent; halos eee |
IG. Large, full brown | White porcelain 12.50 p.m.,
| T. Ground yellowish brown photo. dish good green. T. yellowish
Network red | 12.30 p.m. | green. Network blue.
Chrom. well expanded, red; | Chrom. very retracted,
many with green centres | dark red, arborescent,
MY s
Blue spots few, arborescent, without halos

without halos

|
|
|
|
|

H. Similar to A

White porcelain | Greenish.
Blue spots many, arborescent,, dish12.30p.m. | TT. Ground yellowish
with halos green. Network green.

Chrom. slightly

expanded, red; slightly

arborescent ; clear
halos, giving off

| /seemingly blue reticulum

I. Large brown Glass jar half filled 1.5 p.m.,
T. Ground red | with grey-black | dark black-brown
Red network with green patches | sand 12.30 p.m.
Blue spots few, 1 small behind
eye

Added I and E to red light (not with above, but using Griffiths’s vessel), but at 7.5
Light incandescent. 7.5 p.m., Aug. 22nd.—Exposed A in blue, B and C in red,
two porcelain dishes, one with I, and E, other with F.
10.30 p.m., Aug. 22nd.
A. (in blue light, incandescent, mirror) Good nocturne . : : :

B,C. Redlight. ; ; : : - Good nocturne .

D. Green light . 2 - : : - Good nocturne .

F. Porcelain : : ; : : . Fair nocturne . - : :
; ‘ j Slightly nocturne; transparent; brown
G, H. Black plate . : E A < + tra iente BERIIO ?

: I. Brown, trace of blue
I, E. Porcelain : : : : : co ant on Ps

HIPPOLYTE VARIANS.

681

2.30 p.m.,
brown

2 p.m.,
greenish
brown; a few
minutes later
brown

2 p.m.,
greenish

p.m. replaced them in porcelain dish.
D in green light, the two latter well mirrored.

Nocturne.

Put in
porcelain dish
at 2.30 p.m.

Put on black
plate at
2.30 p.m.

Put on black
plate at
2.30 p.m.

3.20 p.m.

Brown with

tinge of green in |

mid.

Brown but
distinctly
greenish,

especially in
mid.

3.20 p.m.,
dark olive-
green

4.50 p.m.,
dull greenish
brown

4.50 p.m.,
dark brown

Dark brown

Brown with
tinge of
green

7.5 p.m.

Brown with
touch of
nocturne.

Good brown.

Good brown.

No record.

11.10 a.m., Aug. 28rd.

Nocturne in mid.; ant. and hind brown.

Good nocturne.
Brown, dark.

Dark brown.
Dead.

Very transparent, grey.
Microscopically : (E.)

T. Incandescent.

Ground colour none.
Network faint, blue-green.
Chrom. slightly expanded, yellowish red.
R. Ground dull grey.
Network invisible.
Chrom. branches red ; centres greenish yellow,

Had been exposed rather to daylight than to incandescent.

Black plate standing near, and also

GAMBLE AND F. W. KEEBLE.

SW

682

0]. “ Suh al) "a Li aL a a SS eee eee :

-“BALOSGO Sutanp yno Suro poa

£ Worqtaaasqo

‘Oley
ou fqudosoa
-oqie = Kueyy

*soyounsg
enTq
quoosa.toq
“1B oped fq
popunoains
‘pot Yep “yy
Syovlq ‘po
govtjet A194
"m90a8
‘7 «6 f wood
qsmyq oun
“uaa
{rep eal
‘ W90tS-MOT[O X
q00u ou
‘M001d poor

“4 SI, wae.
%G

“uory

Sump duny, you
jamooeq = — ‘saaoryd
-oyvutoryo «= Kunz
SUOIPUIPBI ONG “YY
oyey Sur
“UAMOIN STOIQRIPVA
anyq YIM sofon
-OVA [BAQOD puNoL
Auvut ojUr uayo.q
‘snoretinu Apa ‘7,
(sdurmy ojex
-wdos Jo poesodmoo
19SU0] OU) seyoUTAG
QMOYS UGTA uMoTG
qsippot wan
sdumy fF 10 e YgIA
‘sag ta0 pao
“OL UMOIG YaAUp

wel

WL

on] Ystudeas +47
OnTq JOUTSIP *L

U0 YSN Yarep ‘yy
fudeds ystaop[ak +g,
pury pue que uMo01q

“pra Ul WaaIs oUt

WAST] poy
T|

"urd 0R'g

“urd 03°

*oq9 “omy
UOlI4BATASqO

sunmp oSuvyo

sgods oniq

sotoydoyermo.ayo

(UNPNOg Or pue

Ino[oo

puno.wy

d1doosoaot
Aduoiedsuvay

1S i

INOTOO [ea

-9010.5 afo-poyeyy

uol1y

“VULUIEXO OOF

-Oq

quoMyvony,
UO BULENT]
* AAQMepy
* -[ossa A

uMoOIq
TP 1s
prop
bai >
PLOOTOSR iT
*sOqO] [Ra
puR so[vos
poppoods
pur ‘umorq
qsor f "prim
UL YSTUdALS
Ayqure
ournjoou
oqib [L199

“JOON | “JOON

UMOAC
pur pues “que
femangjoou
ny ogmb | |

gou fad TT |

poaomoar |
LOLALTAT | “QOONT | "QO0NT
— aa Bec, =
“WB 08'6— "ST | pate wd OT

UMOAG
Ayouts ([01}u09 Y)
qsoa f Ystn{q ouanjoou
UMOIG [[Np | uored tog Aqqoad
— 07 AraAoooxy -SUBL, £01990q ssupg
RGLOCGION bs) uMOTG
pus qsou § dung
quored | umoaq pu |ynoqe usead popuryq
“Suva uddts pus ystfors ‘quoredsuvay
er1our | Quoredsuvy | “uornd ‘ysrmoaas
8'6 Ayqoad [4g |-suv.cq-1u19g] ‘vao S108 vy (p)
Sq ual] £ auingoou [Ny
an[q-UMoarg}oqmb you 7 (¢g)
— poreqyeay, Ayourg | favl urepoor0g
qYSt] Ud9IS vu
“VOON _ — -1njoou siq (z)
TOMATO
Aq soystp
ud0Ld puv pot
01 U0 paqooqpoa
QUST pus quy.dru
1l® suring
4ST] quaosap
-uwour £4431]
“qoou pat of pasodxe
oq?) — --- [Bumyo0u 31q (T)
‘wid 0876 ‘urd 66 "md 99°g ‘urd 398

‘uns Ou ‘Ko13 S4y Sty wood 0} % ‘pox

0} posodxa [ Suodo wi 4yor "urd 0g'g [119 “U'e OZ'6—" NBT

“B1q [[e ‘Avp [yu yawp ul u99q pey smowioo0dg—'g¢6g1 “HILT ysndny
SS De

“INGNIYGAXH] LHYIT GXAIn01I0N—]T A AAV,

683

HIPPOLYTE VARIANS.

"Vv ul ‘9 ‘gp Sq ul gE
GL § yalep oy] Ut 109R]
-nodto ae ‘tr gnd meyy
‘saqnurut QT Ur asuvyo
ou fyarup ul WY sep
ur gnd ‘urd cey 9y

“SULJTNOM poi

“UMOIG

[ivy puw yuoIZ oUt
f*plut UL eu.mgjoou [Ny

aSUvYO ON

asuryo ON
UAMO.L
-faas uored
-suBI] JSoa

ISULYD ON

-

aSUVyO ON

£dwny auanqoou
“9MINJOOU [[N,7| 07 eUINJOON auce
| puryeq
| YSIM Mog
(:[218 Agysys
*(yors) puryoq ystp | Apjueredde) | ‘users yy 817
-pat qurey Quoredsur.y uMomq —- f quoaedsuray
‘dummy oy umoiq ystiary poox Kia A
udaIs aurngjoou
"Ud0IS YY SVT Toa TeuGE
‘aurngoou duinq
AT[nAqQnop ynq ‘teas | puryaq Aors | ouangoou
[nz fgueredsuvaqg AOA} Systucery | Wa
“urd gg) hi rates "wd 09°6

UMOLG
aa = | pred Ww
| U9dIS FY ST
aumnjoou aurnjoou | fquordsuvay
UVaIS TN] Wa LUGE Kaa A
ssopInojoo | anyq
qsowly aSuRYD ON Quin, asuvyo ON
|
auanjoou | | (euinjoou)
Way | ueatg =| oumgoony:s (| UeOAS YSTNTG
|
| |
| |
| euangoou Kaas
| WeeIs JUILF jon{q UIeT puv| puUe Nees
pue ysthors | quoavdsuvx4 YSIUMOLG
usar [ny | fyueredsueay, A190 A Squoandsuray,
puryaq
Ysa aoaq
‘duny
uddaIs | [NF auInjoou [09 udeas FY ST]
uda1s [[ny | fgueardsuvzy | Wag Squoavdsuvay,
waar |
Waals [[N Plecouayy aUInjo0N uaa)
“wd OT'9 ae aF cl md QT’ “urd ¢
wap “dag ore &

19A00 ou £ diap
ou £youeq uo sivl
ssvps ul pooys £ (peqey
-undaw sofa) ears
ystmoypok ‘astey *Z

“prot url WMOIq
qstmojoh £ ssayanojoo
‘quoredsuray ‘asaey “9

yuid osuery *g|

MOOI [[NJ“Pazis-PUN “F

UMOIG JSUT “€

UMOIG
ystmop]aX “pazis-prI “G

“pita UI Uaets “MMOIG
qstmo[jas esivy “TT

“UR GH TT ‘pag 4ydag

Vy

‘smopurm ATOJRLOGeT OY FO oMOS MOAT 4ST] ‘Avp oy) SuLIMp
‘poatooor Yor ‘savl oy} Fo Youq oy} ye poovyd sv paxvoqpavo oj Jo yooys

"S681 ‘W1G 07 pag “gdog ‘ferg
“LHOIT TNGOSHAONVONT HIM DENGAN d XG NOILYNIWATTT INVISNO)— [ITA Wd if, ,

‘1OJVM JO 4UadINo B dopuN YsIp uLepoodod o4ryM UI SuIpueys stoAoo UT[suM [ITA savl sel

KEEBLE.

GAMBLE AND F. W.

W.

F,

684:

“UMOIG- pat
quorudswea y,

“UMOAG-Pat
quaiedsuety,

"udadS QYSVT

“UMOTG YSTUAALD
UMOAG,
ysranear dummy
03 youq £ udeIs
sofa purryoq
fquortedsunay,

‘a.SUBIIO ON

‘U90I8 POOS
quoredsurry
Ki0 A
‘usais oped
quoredsurcy
Kio A

“wd ggg

asuvygo ON

asuvyo ON

UddIS [[UYT

UMOTG YSTMOTLA X

UMOAG
quotudsurea y,

UMOAG-9}L[O00Y,

Ysippou
£ quorwdsurvay,

onTq jou “Wea
quoredsung
Kio A

anT{q JOU StaaL5 |

£quoredsuesy
A104

WR ST TL Wg “4dag

aSUBILD ON

asuUBYyO ON

ptooat ON
oUINZo0U [[OyT
auIMgQooU [QT
ua Ystdoas

quvd apppru
‘UMoOrq [Up

[ley pus pro

OUIN{ZOOU [TOY

duINgooU [LT

‘urd 99°6

UMOAG-PYT

UMOAG “PO

UdOLD OUT
quorvdsuvty
Kaoa §u9aas Apog

JO JSot UMOTG [IV]

UMOLG JULI]

YSLUMOL ET

UMOAG FO 08U1y
Gia ‘Mo90a9 [NG

W998 FO a9u1y

(GIM ‘UMOrg FYSTy

‘urd Qg'@T “Wp dag

suviava oykjoddry jo suomroods [jv q pur g UT
fMOTJVALOSGO Loy LAVSSOOU OWL} 4SOJAOYS LOF POAOWIO SBA OITA “YOO Youlq YIM potoAoo (T pur
‘¢ “WV syseiy ‘pooy se uoats og Ajoddryx Jo sooord [pems f poom ou f ATLep oora\g 10 ooU0 pasueyo

IoyVM Younoiyy suyepno11o «Ary

[vuangoou
Aysts

OUI 490 NY

ouANgoou [Ny]

oUAIngoou [LOT

AUINJOOU [Myf

YStuodde
Squorvdsuncy
ATHY SIS

[189 9B YSIUMOAG
£ OULINJOO NY

paiog {eu y

“urd 03'6

|
|

“peed
Koad quoaed
-suviy £10 A

YSTUMO.LG,
Tez F asin
quriey “quored
-suvty £10 A

ud0L [[NG

aSuvnyo ON

aoUvyD ON

eqgepoooyg |

“peo
“p t0(]

“HOY UOT

aUANZOOU [VT |

dwny |
purgoq umo4rq |
S OTUNJOON

ud ¢

‘poyejndure soo A1oyy pvt

uooas oped [Rug
udaIs JO adult YUM
UMomd 44ST pazis-pL

UMOIG
qs, quoardsuray osaury

:(pozeyndme soko) q YsVpq
; : oars oped [peurg

woaas YStmol[ak pazis-pryl

UMOLG
quowedsueay as.very
:(paatoaoos you) O ysl q

EST

: * UMOAG [TRIG

‘ Udd.15 POZIS-PLINT

: UMOAG [[QJ 0.0.0UrT
:(poyugndu soko) q SULA

; * Weed AYLST] [BUG

Uda.
[Up quorvdsavag pozis-priyy

Ud9dLS YSIUMOAG
quoavdsuvig a.d.vUry

Vv ASvLdl

{Tap

‘4YoI] posnyip 07 posodxo [oaquo0d & —) SVL]

‘T INGWIUHdxXG, WAV LNVLSNOSF)—'X] Wavy

‘quowldodxiy Yalvq gueysuog—'ggst ‘WIZ 07 pag aoquioydeg “ford

685

VARIANS.

HIPPOLYTE

Ig “ydag uo
perp fraud 4
48 aSueyo ou
fuedo ul VAT Q
qgim gnd
ulese fumo1q
tye eh
pesuvyoug

BAT
Reese elt
£1078.10q¥]
uo pooys

fasanyo ON

“we 08°01
Wah “ydag

drip v
SE UB U tas
FYSIU Te 450]
f asuvyo ON

“ud01s
plecouigy

‘u9da18 yuored
-suvdy [ING

‘ud g

UMOIG YsIppet
quorvdsuray,
{ uMoaq
ry | -Ueers
oo Tap
a=: | guard
Ors -SUBI
09 L
a = { UMOIq
= oy -Wa01s
me Il8@p
5 queried
{_ -sueay,
‘mda

REST

ureyeo.r0d
UI BAT) UI

UMOIG FYST]
quoredsursy
Ki9 A

UMOIG FY SI]

UMOIG YSIppet 07 pataaodey]

qusosepuBout

gnd fumoaq |quoredsueay)ur uMorq Ystppet 03 Ayoqoqd

[vuinqoou
“TUG

suinjoou poor)

(-quoo) Set

UdaIS 4ST]
quorvdsuvay
S10

Ud0IS 4ST]
queredsurty,
uddaIS FSI]
quoredsuvay,

(qu00) D YsVlq

ou.injoou
“18g
(-qu09) gq YSVyA

aUINgooU [NT

auinjoou pooy
(-qu09) VAS"

({stpper gusty] AxoA |-wood pasoaooea pey OzZ'L FV
“MdaIS JYSI] pouremay
“mue0IS
JUST gset rey uo uMOIqG
-morfok may, svm £ sognuTUT
GI uoosopuvour ur yng
*paloaooad Jou pry OFZ
qe $gzg'), Jueosepuvout ul yng
INO[OO YSIMTMOIG
quoivdsuesy 03 19A00
“Ol JourysIp OSL 98 SOT
‘pveqd |jysIT guaosepuvour ur yng
Ax0ye.10qvy Ut
qoueq rtepun
qysiy] wrp [req wo
urgnd fueers| uwaeis jsay[np {users yuorvdsueay
p[Bi1oury pletomg joz AroAooar f4y51[hep ur yng
UMOIG JILSIT
[ley fystuse1s yuerdsursy
asuvyo ON | ueeIS [nq |oz Arpaovea f4ySyAvp ur yng
‘ud 0¢'g ‘urd OL'ST er aya :
. “y49 ‘4dag wd og L 0} sb

‘(penulyuo0od) XT WTaV],

‘wd g*f “qyg “ydag

BBB

VOL. 43, PART 4.—NEW SERIES.

686 F. W. GAMBLE AND F. W. KEEBLE.

TaBLe X.—COoNSTANT

Piel, Aug. 26th—28th, 1898.—Constant dark experiment with

of examination

Flask B, air circulator, Aug. 26th, 12 noon. 7.10 p.m. | 10 p.m.
Large brown Hippolyte Semi-nocturne Nocturne
Mid-sized, transparent, brown Slightly nocturnal; trans- Nocturne

parent, grey
‘Small, brown Dull grey Nocturne
|
Flask A—
Large, brown Went slightly nocturnal
Mid-sized, light brown | Eyes after operation and re-

Larger, light brown | amputated covered. At 7.10 p.m. all)
2 small, light brown dead.

Flask Ag@— Cut
ventrally |Nocturne; brown hind
with view |Nocturne
of section- |Nocturne
| ing nerve- |Transferred to flask A
cord

Large, dark, black-brown
Mid-sized ,, ”
Small = »

| All with suggestion of grey

Good nocturne
Good nocturne

One not seen

Water circulator B—
12.40 p.m. Scraps of Dictyota weed |

Large, transparent, yellow-brown Unchanged
| Mid-sized, brown Unchanged
| 2 small, lightish brown \Unchanged

‘Water circulator A. No weed—
| Mid-sized, light brown Light brown

| Mid-sized, transparent green Light brown

Mid-sized, yellowish green Greyish brown

Mid-sized, almost black, freckled with
lighter spots

Unchanged

Very transparent;
almost colourless ;
tinge of green

Unchanged

2 nocturnes

2 very transparent
and almost colourless;
1 of them slightly
greenish

HIPPOLYTE VARIANS.

Dark Experiment 2.

air and water circulators.

(4—4 minute).

Aug. 27th, 10.45 a.m.

3.45 p.m.

9.30 p.m.

Nocturne

Nocturne

Transparent,
brownish

Large, opaque,

mauve tinge
Small, dark brown

Transparent, pale
brown

No further record

2 brown

2 green and
1 red-brown
1 dead.

reddish brown, with

Good nocturne; ant.
and hind brown

Nocturne

Brown

Almost black

Dark brown-black

Very transparent,
almost colourless

2 brown

2 light green
1 reddish brown

Nocturne

Nocturne

Nocturne

Good nocturne

Good nocturne

Transparent; very
light yellowish

2 full nocturnes

2 nocturnes
1 light brown

687

Contents exposed only during time

Aug. 28th, 12.10 p.m.

Mid. faint blue-green;
ant. and hind brown.

Brown.

Transparent,
greyish.

Dark brown.

Dark brown.

| Light, transparent, |
yellow.

2 reddish brown.

| 2 light green.
| 1 reddish brown.

688

F. W. GAMBLE AND F. W. KEEBLE.

TaBLe XI.—ExPERIMENT

August 19th, 20th.—Effects of darkness, scattered, and red light

August 19th.

12.30 p.m.
A. Black-brown
T. Ground pale yellow; net-
work red and green; blue
spots fairly numerous, with
clear halos
B. Similar to A.
Green streaky network
R. Yellow marginal chrom.; some
blue spots with dense red
mass round them

C. Dark olive-brown
T. Red and green patches
R. Chrom., red with green, and
some with yellow centres;
blue spots regular, some with
dense red halos

D. Dark brown

T. Ground reddish; network red
and green; blue spots numer-
ous, without halos

12.45.
EK. Dark brown
R. Light brown ground; red and
green network; few blue
spots without halos

F. (A control.) Same as E

Eyes amputated ; no obvious
microscopical change; put
in drip in dark

Put in drip in dark

|

Examined

no change; eyes painted

with AgNO,; expansion|

of light frosted green

branches concealing red
reticulum

Put in drip in dark

microscopically,

3.50 p.m.
Very sick ; putin dark (see
below).

Dark brown; put in open
in white porcelain dish
(see below).

3 p.m.

Eyes painted with AgNO,;
T. Chrom. green cen-
tres and branches more
marked ; red less
marked ; put in drip.

3.15 p.m.
Eyes amputated by squeez-
ing; no change.

3.50 p.m.
Good nocturne; R. Fine
green network; red
more contracted; blue

spots with blue-green
branches.

HIPPOLYTE VARIANS. 689

with Brinpep HippoLytTe.

on amputated, nitrated, and normal Hippolyte varians.

August 19th. _ =

12.45 p.m.
G. SameasE . ; : : ..Examined, no change;
amputated eyes; green
more marked; left in
drip in light; went full
nocturne.
1 p.m., incandescent. 3.35 p.m.
H. Dark black-brown Left in drip Examined by incandescent,
(Opaque to T.) no change; eyes nitrated
R. Red and green network; 2 with AgNO,; slight but
small blue spots distinct increase in green-
ness.
1.10 p.m., incandescent. 4.35 p.m.
I. Dark brown . : |Went lighter during exa-|Put in red light incandes-

R. Red and green patches; blue| mination; put indrip3.40| cent and mirror.
spots arborescent ZZ
ee ee ee re | ee
9.5 p.m., incandescent.

I. After red light. Colour—blue

T, Delicate blue network; chrom.,
with black centres

R. Network blue; chrom. dark
red, with blue-green vacu-

oles; blue spots small, blue-
black, no arborescence

aa

9.8 p.m., incandescent.
Blue-green
T, Network in part red; network
in part biue; chrom. dark
red; microscopically exa-
mined
R. Yellow-green ground; net-
"work red; chrom.as before,
but centres not so clear

690 F. W. GAMBLE AND F. W. KEEBLE.

Taste XI—
Angust 19th, put in dark.
3.50 p.m. 4 p.m.
A. Amputated . 5 : : ; > . Dead.
H. Nitrated - - - . : 5 . Slightly nocturnal.
F. Normal control : : : ; ; : : :
ee |
In porcelain dish in open, 3.50 p.m. | Colour at 3.50. | 7 p.m., incandescent. 9.32 p.m.
G, Ampntated : : . Good nocturne Green behind eyesto Blue-green in
| hump; rest brown mid.; ant. and hind
brown
E. Nitrated . ; : . Dark brown-black | Dark brown, last | Semi-nocturne;

2 segments blue recovery in 2 min.
(= network by

| | microscope) |
|E. Normal . : : -| Dark brown-black Dark brown | Full nocturne |
In red light. Colour at 3.50. 7.10 p.m. 9.5 p.m.
D. Amputated : : .. Dark brown ) Brown, slightly ))
transparent
| behind eyes
IC. Nitrated . . ; .| Brown Two green Fair nocturne ;
L nocturnes and one recovered con- L
greeninmid. siderably to brown [
| (not taken out) in 5 min.
I. Normal control . : ‘ Brown Full nocturne | |—
J J |

(continued).

10 p.m.

Dead.
Light brown (put in muslin jar)

HIPPOLYTE VARIANS.

August 20th, 11 a.m.
Dark brown

691

7 p.m.
Slight nocturne.

|

9.50. = 10.40. - Be eae 10.55. |

: ue ea |

Fully ‘) Nocturne in) | Nocturne at Recovered to |
recovered |. mid | sidesand behind) full brown.

eyes |

No record | : Dull blue; : Dead Putinmuslin.

Put in Fe Faery pat lbp ane

r/muslin Td Neck ie ei f/ereen light |

green Ps |

Dull blue- | Nearly full Dark brown No record. |

green ) nocturne J

10 p.m.

Put in porcelain
dish with
incandescent for
20 min.

No nocturnes

Put in inean-
descent all
night

August 20th, ‘ 5
| 10.40 a.m. 11.40 a.m. 12.45 p.m.
|

Dead.
| |
_ Dark brown. | Unaltered; fair Unaltered.

Good nocturne
| except ant. and
hind
Left in
incandescent

nocturne except |
ant. and hind
brown
Put in porcelain Partly recovered ;
in open ; cloudy stillopaque |
greenish.

692

1842

1857
1867
1867

1872

1876

F. W. GAMBLE AND F. W. KEEBLE.

LITERATURE.

. Kroyer, H.—‘‘ Monografisk Fremstilling af Slaegten Hippolyte’s
Nordiske arten,” ‘Kong. Dansk. Vid. Selskab. Afhandlinger,’
Deel 9, p. 244.

. Krvanan.—‘ Proce. Nat. Hist. Soc.,’? Dublin, p. 48.

. Sars, G. O.—‘ Histoire naturelle des Crustacés d’Eau douce de
Norvége,’ p. 28, Colour Change in Mysis relicta.

. Kinanan.—‘ Proce. Nat. Hist. Soc.,? Dublin, p. 47, figs. 1—6, Hip-
polyte varians at Kingstowa.

. Poucuet.—‘“‘ Sur les rapides changements de coloration provoqués
expérimentalement chez les Crustacés,” ‘Comptes rendus,’ vol.
Ixxiv, p. 757.

. Poucnet.—“ Changements de coloration sous l’influence des nerfs,”
‘Journal d’Anatomie et de la Physiologie,’ pp. 1—90 and 113—165,
vol, xii.

1880-81. Mituer, Fritz.—‘Farbenwechsel bei Krabben v. Garneelen,’

Kosmos, iv Jahrg., Heft 12, p. 472.

1882. Matzporrr.—“ Ueber die Farbung von Idotea tricuspidata,”

1891

‘ Jenaische Zeitschrift,’ xvi, pp. 1—59.

. Exner.—‘ Die Physiologie der facetterten Augen von Krebsen und
Insekten,’ Leipzig und Wien.

1892. Herpman.—‘ Sixth Annual Report Liverpool Marine Biological Com-

1892

1892

1892

1892

mittee,’ December, 1892.

. Acassiz, A.—‘ Studies from the Newport Marine Zoological Labora-
tory. XXIX. Preliminary Note on some Modifications of the Chro-
matophores of Fishes and Crustaceans,” ‘Bulletin Mus. Comp.
Zool.,’ Harvard, vol. xxiii, No. 4.

. Matarp, A. E.—* Bulletin Société Philomathique d. Paris,” Sec. 8,
vol. iv, p. 28, Trans. ‘Ann. Mag. Nat. Hist.,’ vol. xi, 1893.

. Brepermann, W.—‘ Ueber d. Farbenwechsel d. Frésche,” ‘ Pfliiger’s
Archiv,’ Bd. li, pp. 455—608. .

. Brooxs anD Herrick.—‘‘ The Embryology and Metamorphosis of
the Macroura,” ‘ National Academy of Sciences,’ vol. v, memoir iv;
especially p. 333, “¢ Variation in Habits and Colour of Alpheus;”
pp. 454—458, “The Eye under the Influence of Light and Dark-

ness.”

1893. WatrHEeR.—‘ Bionomie des Meeres,’ Jena, Gustav Fischer.

1893

1894.

1895.

1895.

1896.

1896.

1897.

1897.

1897.

1897.

1898.

1898.

1898

1898

HIPPOLYTE VARIANS. 693

. Herpman.— Seventh Report Liverpool Marine Biol. Committee.’

Lanpout, H.—‘‘ Methode zur Bestimmung d. Rotations-Dispersion
mit Hilfe von Strahlenfiltern,” ‘Bericht deutsch. chem. Gesellsch.,’
p. 2872.

Faxon.—*‘ Reports of the ‘Albatross’ Expedition. XV. Stalk-eyed
Crustacea,” pp. 251-3, ‘Memoirs Harvard Museum,’ No.
XVill.

Keiier, R.—‘‘ Ueber den Farbenwechsel d. Chamaleons u. einiger
anderer Reptilien,” ‘ Pfliiger’s Archiv f. d. gesammt. Physiologie,’
Bd. lxi, pp. 123—168.

Rosrenstapt.—“ Beitrage zur Kenntniss des Baues d. zusammen-
gesetzen Auges bei den Decapoden,” ‘ Archiv mikroscop. Anatomie,’
Bd. xlvii, pp. 748—770: Lucifer, Sergestes, Virbius, Pale-
mon.

Hotmeren.—“ Zur Kenntniss d. Hautnervensystems d. Arthropoden
(Chromatophores of Mysis),” ‘Anat. Anz.,’ Bd. xii, Nos. 19, 20,
Nov., pp. 449—487.

Hornetu.—‘ The Protective Colouring of the sop Prawns,”
‘Journal of Marine Zoology and Microscopy,’ vol. ui, No. 6, Dec.,
pp. 101-3.

NusBAUM AND SCHREIBER. —‘ Beitrag zur Kenntniss d. peripheralen
Nervensystems bei den Crustaceen,” ‘ Biol. Centralblatt,’ Bd. xvii,
No. 17, Sept., pp. 625—640 (Astacus).

VerRiLt, A. E.—* Nocturnal and Diurnal Changes in the Colours of
Certain Fishes and of the Squid (Loligo), with Notes on their
Sleeping Habits,” ‘American Journal of Science,’ ser. 4, vol. iui,
p. 135.

Nerwsictn.—“ The Pigments of Decapod Crustacea,” ‘Journal of
Physiology,’ vol. xxi, pp. 287—257 (Astacus, Nephrops,
Homarus).

HerpmMan.—‘ Twelfth Annual Report Liverpool Marine Biol. Com-
mittee,’ pp. 19, 20.

Hotmeren.—Zum Aufsatze W. Schreiber’s ‘‘ Noch ein Wort iiber das
peripherisch sensible Nervensystem bei den Crustaceen” (Nerve-
plexus, chromatophores in Palewmon), ‘Anat. Anz.,’ Bd. xiv,
No. 16, May, pp. 409—418.

. SCHREIBER, W.—“‘ Noch ein Wort iiber das peripherisch sensible

Nervensystem bei den Crustaceen,’’ ‘Anat. Anz.,’ Bd. xiv, No. 10,
Jan., pp. 273, 277.

. Nacet.— Ueber fliissige Strahlenfilter,” ‘ Biologisches Centralblatt,’

xviii, No. 17, Sept.

694. F. W. GAMBLE AND F. W. KEEBLE.

1898. Newsiern, M. E.—‘Colour in Nature: a Study in Biology,’ John
Murray, pp. i—xii, and 1—343, especially pp. 117—129, “‘ Colours
of Crustacea” and Literature.

1900. Kersie, F. W., and Gampiz, F. W.—< The Colour Physiology of
Hippolyte varians,” ‘ Proc. Roy. Soe.,’ vol. lxv, January.

EXPLANATION OF PLATES 32—36,

Illustrating Messrs. F. W. Gamble and F. W. Keeble’s paper
on “ Hippolyte varians: a Study in Colour-change.”’

PLATE 32.

Plates 1 and 2 illustrate some of the more distinctive colour forms of
Hippolyte varians found at Piel, and show the close resemblance be-
tween the colour or coloration of the prawn and the tints of the seaweed
which it selects. The drawings (except figs. 12 and 13) were made by Miss
D. Richardson, from specimens placed with the weeds trawled at the same
time. After a number of trials it was found that certain colour varieties
selected particular weeds; in other cases direct observation showed that green
prawns affect Zostera, brown ones Halidrys and Dictyota.

Fic. 1.—Two of these specimens show the full green tint assimilating these
prawns to the “leaves,” and one shows the yellowish colour of the lower parts
of the stalks. This difference of tint, associated with a preference for the
upper or lower parts of the Zostera, was frequently observed by us.

Fig. 2.—A green-lined Hippolyte on a piece of green Griffithsia.

Fie. 3.—Two black-barred specimens on the alga Cladostephus spon-
giosus.

Fic. 4.—Two adult prawns on Laminaria.

Fic. 5.—A finely red-lined and barred specimen hiding away amongst
Gigartina. This is, however, by no means the only red weed affected by
this colour variety.

Fic. 6.—Brown Hippolyte on Halidrys siliquosa.

PLATE 33.
Fie. 7.—Young specimen of the “fascigera” variety found among
Bowerbankia growing on the stems of Halidrys.
Fic. 8.—Small “ red-liners ” sheltering among red Griffithsia.
Fig. 9.—Mid-sized brown specimens on Dictyota dichotoma,

HIPPOLYTE VARIANS. 695

Fic. 10.—Two full “ nocturnes,” which had, during the day, been brown in
colour, x 2.

Fie. 11.—A nocturne showing on the antennal scales and abdomen a
trace of the expanded red and yellow pigment. (In the tables this condition
is registered as nocturne in “ mid.,” “ant.,” and “hind,” brown.) xX 2.

Fic, 12.—A black-barred specimen in the nocturnal! condition. x 2.

Fic. 13.—The same in the diurnal colour phase. x 2.

PLATE 34.

All the figures in this plate are taken from “red-liners” (see text, pp.
606 to 608).

Fie. 14.—A “red-liner,” showing the characteristic bars and stripes of
colour. ‘I'he specimen was outlined with the camera, and the painting made
by transmitted light. Hence the (apparent) absence of yellow spots spoken
of in the text (p. 609). x 7.

Fie. 15.—A camera drawing of the chief arteries of the abdomen, taken
from a red-lined specimen in all respects comparable to Fig. 14, except that
the colour was very faint, and the increased transparency thus aided the
definition of the deeper vessels. This figure is to be compared with Fig. 14,
in order to show the close agreement between the course of the segmental
arteries going to the swimmerets, and the bars of red spots in Fig. 14. In
the specimen (Fig. 15) the bars of colour were placed exactly behind the seg-
mental artery, which often gave off a small branch to them. The heart was
beating about twice a second. No sign of an inferior abdominal artery could
be detected, though the passage of the blood from the arterial capillaries into
the sinuses was clearly seen. ‘The sternal and thoracic arteries are omitted.
x 7.

Fie. 16.—Three abdominal segments from the tail of a red-liner to show
the aorta (D. 4.); the pigment attached to the wall of the intestine, and
moving during peristalsis (I. P. Z.); the pigment associated with the venous
intestinal sinus (which is dotted); the dense pigmented sheath (V. 8.) round
the ventral cord, and the blood-vessel accompanying it. S&. WY. A swimmeret.

Fic. 17.—Eye of a red-liner, to show the deep chromatophores in connection
with the optic ganglia, and in the more superficial parts of the stalk. x 10.

Fic. 18.—Eye of a faint red-liner in which, owing to the small quantity of
pigment, one can see the ophthalmic artery and its branches, which later inter-
digitate with the processes of the large chromatophore between the first and
second optic ganglia. Only some of the venous spaces at the proximal end of
the stalk are indicated. There are other venous currents from the retina,

> MY).

696 F. W. GAMBLE AND F, W. KEEBLE.

Fic. 19.—A “chromatophore” from a red-liner, to show the way in which
these colour elements frequently wrap their processes round the walls of an
artery. The blood-corpuscles are about equal in diameter to the calibre of
this capillary. In the chromatophore the two pigments (red and yellow) are
distinct, and a point of fusion with a neighbouring pigment spot is indicated.
The anastomosing tendency of the branches is here distinct. Leitz, oc. 3,
obj. 5. Camera lucida. September 20th, 1898. x 190.

Fic. 20.— Deep intermuscular chromatophores of a red-liner. Leitz, oc. 3,
obj. 6. Camera lucida. August 24th, 1898. x 250.

PLATE 35.

Fic. 21.—Right side of the carapace of a green specimen drawn with the
camera, to show the varying form and size of the “blue spots.”’ Transmitted
light. Leitz, oc. 1, obj. 3. x 30. September 19th, 1898.

Fic. 22.—A “‘blue spot” from a green Hippolyte varians, sending
out delicate branches which in close association with the yellow of neighbour-
ing chromatophores produce a total effect of green by reflected light. Each
of these chromatophores has possibly its own store of blue colour in addition
to the red and yellow seen in the figure; but it is difficult to determine how
much of the blue constituent of the green effect is derived from the branches
of the large blue spot, and how much is proper to each chromatophore.
Transmitted light. Leitz, oc. 3, obj. 5. Camera lucida. See text, p. 190.
September 20th, 1898.

Fic. 23.—Muscle chromatophores from a small pink Hippolyte varians.
The colour of the specimen was almost entirely due to these deep chromato-
phores. The red pigment (black in the figure) is arranged in tubes which
run parallel to the course of the fibres, and give off branches which pass
outwards and bifurcate. The colour of most small Hippolyte is deter-
mined by the amount and arrangement of the pigments in these muscle
chromatophores. In larger, less transparent forms the superficial network of
colour conceals the great store of pigments which exist in the underlying
muscle. Leitz, oc. 3, obj. 5. St. Vaast. August, 1899.

Fic. 24.—A portion of the carapace of a full brown Hippolyte. The
network is chiefly red witl some yellow strands, and here and there green
patches. It is difficult to distinguish ‘ chromatophores.” Leitz, oc. 1, obj. 3.
Camera lucida. September 16th, 1898.

Fic. 25.—Blue spots and the indefinite irregular reticulum of a pink
Hippolyte. The blue spots have distinct clear envelopes traversed by
yellowish radiations, and by three stouter red processes which arise from the
larger blue spot and mingle with the general reticulum. Leitz, oc. 3, obj.
5. August 5th, 1898.

HIPPOLYTE VARIANS. 697

Kies. 26—28.—Three “ chromatophores ” from different levels of the same
part of the body of a specimen of Hippolyte varians. Fig. 26 is a sub-
epidermal pigment cell with red, yellow, and blue pigments, Focussing down
‘013 mm. (as determined by the distance through which the milled head of
the fine adjustment is turned), Fig. 27 is reached, which shows the appear-
ance of “ chromatophores ” lying between muscle-fibres. Focussing ‘066 mm.
deeper, Fig. 28, a deeply placed pigmented element, comes into view. Leitz,
oc. 4, obj. 3.

Fies. 29—32.—A series of sketches of the same “chromatophores” at
intervals of about ten minutes. They are taken from a specimen of the
“fascigera”’ variety of H. varians, the eyes of which were amputated on
August 22nd, 1898. The specimen was left in a current of water (in the
dark) till11.20 a.m., August 23rd. It was then freckled, sandy-coloured, trans-
parent, not at all nocturnal. Fig. 29 was drawn at 11.25, Fig. 30 at 11.80,
Fig. 3lat 11.45. Fig. 32 is an enlarged view of one of the “‘ chromatophores ”
at 11.55. A had two dark red spots (black in the figure), the remainder
being clear yellowish green. B was bright red. The figures show that for
the first ten minutes after exposure to light the “ chromatophores ” (even after
extirpation of the eyes) began to expand. At 11.35 the specimen was put
back in porcelain dish and covered with black cloth. At 11.45 a certain
retraction of the yellow and red pigments in A and B respectively had
occurred. At 11.55 the specimen was dead. Figs. 29, 30, and 31 are drawn
with Leitz, oc. 4, obj. 3; Fig. 32, oc. 4, obj.5. All camera drawings.

PLATE 36.

Fie, 33.—D, four drawings of the same “ chromatophore;” A at 6.2 p.m.,
B at 6.43, C at 6.83, and D at 8.13 p.m. ‘They are taken from a
nocturne at first rapidly recovering, owing to the stimulus of the trans-
mitted light. Owing to slight movements of the animal there are slight
discrepancies between the figures, but great care has been taken to represent
the same “ chromatophore ” in each drawing. The red and yellow pigments in
A are strongly retracted, while the enveloping blue merges into a delicate
blue reticulum. As recovery proceeds the yellow pigment comes out, followed
by the red, while as the blue retracts from the reticulum it forms irregular
masses at the sides of the “ chromatophore.” The pigment is very granular, or,
what is probably a more correct statement, there are bodies of peculiar optical
properties bathed in a homogeneous yellow pigment. When this pigment is
beginning to expand these bodies are carried outwards, and at first have very
little pigment with them. They then appear dark by transmitted light, but
bright yellowish by reflected light. Leitz, oc. 4, obj. 5. Camera lucida.
December 21st, 1898.

Fic. 34.—“ Chromatophore ” of a nocturne, to show retracted red and yellow
and expanded blue pigments. Zeiss, oc. 4, obj. D. Camera lucida.

698 F. W. GAMBLE AND F. W. KEEBLE.

Fie. 35.—A, B, C, a “ chromatophore” from a full nocturne; A at 6.44 p.m.,
B at 6.483, C at 6.56. At 7.10 there was no further obvious change. In
this case the expansion of the red and retraction of the blue took place slowly
aud only to a limited extent. Such is often the case with nocturnes in
December, though cases of rapid recovery are not rare. December 18th,
1898. Camera lucida.

Fic. 36.—A—F exhibit a series of changes in the same ‘‘ chromatophore,”
though the prawn under examination was undoubtedly dead after B was drawn
as far as could be ascertained by the stoppage of the heart and gill-current.
The pigments were red and yellow. August 25th, 1898. Leitz, oc. 4, obj. 5.
camera lucida.

Fic. 37.—A—C, camera drawings of a “ chromatophore ” at intervals of five
to ten minutes. The specimen was an Hippolyte ofa transparent greyish
colour when its eyes were amputated at 3.25 p.m., August 25th. Up to 6.10,
when sketch A was made, the prawn was kept in the dark. When brought
out it was a nearly full nocturne, though greenish blue in tint. While being
drawn it recovered (owing to the expansion of its “ chromatophores ”’) toa
transparent brown tint, and was undoubtedly alive at 6.40 when the sketches
were finished. This shows that amputated Hippolyte nocturne and recover
just as normal specimens do. Pigments red and yellow. Leitz, oc. 4, obj. 5.

Fic. 38.—A—C, camera drawings of the same “chromatophore ” from a
transparent brown-barred “fascigera” variety of H. varians; A at 2.16
p.m., August 23rd, 1898, B at 2.18, C at 2.20. These show rapid expansion
of pigment into hitherto colourless processes. Leitz, oc. 4, obj. 5.

THE NEPHRIDIA OF THE POLYCHATA. 699

On the Nephridia of the Polycheta.'

Part III—The Phyllodocide, Syllide, Amphinomide, etc., with
Summary and Conclusions.
by

Edwin 8. Goodrich, M.A.,
Aldrichian Demonstrator of Comparative Anatomy, Oxford.

With Plates 37—42.

PHYLLODOCID®.

At the end of Part II of this work I announced the dis-
covery in the Phyllodocidee of closed nephridia provided with
solenocytes, and, indeed, it so happens that in this family
are found some of the most beautiful examples of this type of
excretory organ.

The Phyllodocide are divided into two sub-families, the
Alciopine and the Phyllodocine. Of the Alciopine I have
been able to study fresh and preserved specimens of Al-
ciope cantrainii, D. Ch., A. Krohnii, Gruff, Asterope
candida, D. Ch., Vanadis formosa, Clp., at the Zoolo-
gical Station at Naples.

Amongst the Phyllodocine I have examined more espe-
cially fresh and preserved examples of Phyllodoce Pa-
retti, Blainv., Ph. laminosa, Sav., Hulalia punctifera,
Gr., Eteone lactea, Clp., from Plymouth, and a spirit
specimen of Hteone siphonodonta, D. Ch., from Naples.

' Part I appeared in vol. xl (1897), and Part IL in vol. xli (1898) of this

Journal. For the contents of Parts I, II, and III see the table at the end of
this paper.

700 EDWIN S. GOODRICH.

Already Hering, Claparéde, and Greeff have described in
considerable detail the excretory and genital organs of the
Alciopinee, and Gravier those of the Phyllodocine ; but since
these authors failed to recognise the essential structure of
the true nephridium, and its distinctness from the genital
funnel with which it becomes connected at maturity, it will
be more convenient to delay the consideration of their writ-
ings until after I have dealt with my own observations.

Alciopine.

The Nephridium.—On examining with the microscope a
living specimen of Vanadis formosa compressed under a
cover-glass, the nephridium can be seen in every trunk seg-
ment, after the first two or three, as a long slender tube
running ventrally along the side of the body, between every
consecutive pair of parapodia (fig. 1). Hach nephridium
opens ventrally, and just in front of the base of a para-
podium. ‘T’he external opening leads into a slightly dilated
chamber, which is continued into the nephridial duct extend-
ing forwards, and ending blindly in the posterior region of
the next segment; for the very incomplete septum here
allows the elegantly curved nephridium to project beyond it.
Bunches of solenocytes are set at irregular intervals along
the nephridial canal, chiefly on the outer edge of the curved
surface (fig. 1).

The nephridium of Alciope cantrainii is very similar to
that of Vanadis; but the canal branches anteriorly, and the
solenocytes are fewer in number, and grouped near the ex-
tremities of the blind branches (fig. 3). The bladder-like
dilatation near the external pore is more marked (fig. 5).

In Asterope candida the nephridium is more like that
of Vanadis that that of Alciope.

The detailed structure of the solenocytes in the Alciopinz
and their relation to the nephridial tube are of considerable
interest. The tubes themselves are of remarkable length,
especially in Alciope (fig. 3), narrow, of almost even dia-
meter throughout, and slightly oval in section. They pierce

THE NEPHRIDIA OF THE POLYCHATA. 701

the wall of the nephridial canal, projecting into its lumen for
a certain distance (figs. 2, 3, and 9). At their distal ends
they spring from rounded masses which look so like cells,
in the fresh, that I was at first deceived into the opinion that
they consisted of a row of large cells, each connected with
from four to six tubes (figs. 3 and 9). On further examina-
tion of stained preparations and sections, these rounded, long,
slightly granular masses proved to be made up of a large
number of small nuclei agglomerated together, and each be-
longing to its own tube (fig. 2). Cell outlines there are
none, and of cell substance scarcely a trace. A long flagel-
lum works rapidly down each tube, passing into the lumen
of the nephridial canal.

Characteristic of the nephridia of the Alciopine is the
presence of long powerful cilia situated on the outer or
coelomic surface of the organ in the regions where the
solenocytes are inserted. In Alciope, and perhaps to a less
extent in the other two genera, the tubes of the solenocytes
are regularly disposed in short transverse rows of from three
to six (fig. 4), and the outer cilia appear to work rapidly
backwards and forwards between these rows of tubes (figs.
3 and 9), thus renewing the ccelomic fluid which bathes their
outer surfaces.!

Another detail worthy of notice is that in Asterope
candida, and perhaps also in Alciope (figs. 9 and 2), the
bases of the tubes of the solenocytes are connected together
by a thin web for some distance.

A large number of irregular vacuoles and globules, no
doubt of excretory nature, are generally found in the wall of
the nephridial canal (fig. 9).

There is no internal opening whatever.

The Genital Funnel.—In the quite anterior segments

1 When these nephridia are kept undisturbed for any length of time under
the cover-glass, the cilia soon cease to work; but on the introduction of a
small drop of fresh sea water under the cover, both the outer cilia and the
flagella inside the tubes begin to work again with renewed vigour. The ces-
sation of movement is probably due to the want of oxygen.

VOL, 43, PART 4,.—NEW SERIES, Clerc

702 EDWIN S. GOODRICH,

no other organ is related to the nephridium; but passing
backwards we find in immature specimens deep pouches of
the septa open in front, and ending blindly behind, a right
and a left pouch in every segment. These are the incom-
pletely developed genital funnels.

In Vanadis formosa the funnel is almost tubular in
shape, its inner wall is formed of thick columnar epithelium,
with short cilia not fully developed (fig. 1). The lip of the
opening is continuous all round with the ccelomic epithelium,
into which it gradually passes.

When the worm reaches sexual maturity (as in the Alciope
represented in figs. 8 and 51) the funnels become enlarged
and thin-walled, the lip round the mouth specially differen-
tiated, thickened, and strongly ciliated, whilst the posterior
end fuses with and finally opens into the nephridial duct
about halfway down its course, at a point marked by a bend
in the immature condition (fig. 1).

Such large saccular genital funnels are developed in con-
nection with each right and left nephridium in both sexes
throughout the greater length of the body in all the Al-
ciopids I have examined. The shape of the funnel varies
slightly in the three genera studied, being elongated in
Vanadis, somewhat pear-shaped in Alciope (fig. 8), and more
rounded in Asterope.

In a young specimen of Alciope Krohnii I was able to
follow the development of the genital funnel in the anterior
segments. In the eleventh segment (fig. 6) it was still re-
presented by a mere concave patch of thickened ciliated
coelomic epithelium on the anterior surface of the septum,
quite near the nephridium. Passing backwards, this rudi-
ment was seen to increase in size, and become more concave
in succeeding segments. In segment seventeen (fig. 7) it
had already acquired the essential structure of the adult
organ, excepting, of course, the opening into the nephridium,
which is only formed when the genital products are ripe
enough to be allowed to pass to the exterior. Fig. 8 repre-
sents a longitudinal section through a ripe male Alciope

THE NEPHRIDIA OF THE POLYCHATA. 703

cantrainii, in which the communication between the two
organs has taken place, and the ripe spermatozoa are seen to
have passed down into the nephridial canal.

As already mentioned above, several observers have de-
scribed the excretory organs of the Alciopids. Hering long
ago (18) gave a brief description of these structures, which
he has since corrected and enlarged in a paper published in
1892, to which I shall presently refer (19). Claparéde, in
the supplement to his classical work on the ‘ Annelids of
Naples’ (2), confirmed most of Hering’s early observations,
and gave detailed descriptions and figures of the nephridia
and genital funnelsin Alciope cantrainii and Asterope
candida.

Concerning the former he says, p. 106:

“‘ Les organes seementaires ont une forme trés remarquable.
La premiére paire est placée au second segment sétigeére, et,
jusqu’au 16™ leur conformation reste identique. Cesont de
longs boyaux ciliés dont l’ouverture extréme est placée a la
base des pieds du cété ventral. Le boyau se dirige d’abord
en dedans, perpendiculairement 4 Vaxe, puis il forme un
angle droit, et finit par s’élargir en un petit entonnoir qui
s’engage dans le dissépiment séparant la cavité du segment
de celle du segment précédent. L’entonnoir s’ouvre donc
dans la cavité du segment précédent. . . . Mais 4 partir du
16™° seement sétigére l'appareil se complique, chez le mile,
dune grosse vésicule piriforme, dont le court pédoncule
tubulaire s’insére sur le boyau de Vorgane segmentaire. .. .
Au temps de la maturité cette vésicule est remplie de zoo-
spermes, et joue par conséquent le réle de vésicule sémi-
nale.”

Claparéde’s account is, therefore, nearly correct. He saw
the nephridium, alone in the anterior segments, associated
with the genital funnels in the segments behind the sixteenth.
He failed to find the internal opening of the genital funnel
(vésicule séminale), but saw its posterior communication with
the nephridial canal. He missed, however, the true anterior
extremity of the nephridium, with its solenocytes, and, misled

704 EDWIN 8S. GOODRICH.

perhaps by the notion that a nephridium must necessarily
open into the body-cavity, he erroneously described an open
nephrostome. How near Claparéde was to discovering the
solenocytes will be seen by the following quotation concern-
ing Asterope candida (p. 114):

“ T’ouverture interne de ’organe segmentaire se présente,
comme d’ordinaire, sous la forme d’un entonnoir engagé dans
le dissépiment. . . . L’entonnoir se continue dans le boyau
cilié qui forme une anse en boucle, de forme trés-constante ;

puis le boyau se dirige en arriére . . . presque jusqu’a la
limite du segment suivant. La il se recourbe sur Iui-méme
en s’‘élargissant considérablement .. . il débouche dans un

vaste résérvoir cilié, 4 paroi fort épaisse, qui se dirige en
avant, en s’atténuant par degrés pour venir s’ouvrir a la base
du pied. Ce réservoir est la vésicule séminale de M. Hering.
. .. La particularité la plus remarquable de cet appareil
consiste dans existence de touffes de longs poils raides in-
sérées sur la surface externe du boyau. Ces touffes se pré-
sentent surtout a la surface de lanse en forme de boucle,
mais on peut les suivre au dela, jusque vers le milieu de la
longueur du boyau. M. Krohn, qui se trouvait a Naples en
méme temps que moi, examiné, 4 ma requéte, PAsterope
candida au point de vue de ces singuliéres touffes de poils,
et en confirmé entiérement lexistence. On pourrait songer
& des faisceaux de brides fort ténues, destinées 4 maintenir
Vorgane en position, mais l’extremité des poils m’a toujours
parue parfaitement libre.”

Both Krohn and Claparéde, then, actually saw and figured
the tubes of the solenocytes, believing them to be merely fine
processes (touffes de poils). As shown above, Claparéde
erroneously described and figured the genital funnel of
Asterope as opening forwards directly to the exterior.

Hering in his latest paper (19) gives a very similar de-
scription of the nephridium of Alciope. His figures are
more correct than Claparéde’s; but he fell into the same
errors, believing the nephridium to open in front into the
body-cavity, and the solenocyte tubes to be merely stiff hair-

THE NEPHRIDIA OF THE POLYCHATA. 705

like processes. The genital funnel he looked upon as a
diverticulum of the nephridial canal, probably blind in
front.!

Curiously enough, like Claparéde, he states that the
genital funnel occurs only in the male. This may be due to
the fact that it is more difficult to see in the female, where it
is not crammed with refringent spermatozoa,

Greeff is the third author who has dealt with these organs.
In his general work (14) he gives a very brief and incom-
plete account of their structure, but returns to the subject
in 1885 (15). Describing Rhynchonerella fulgens,
Greeff says, p. 451: “ Bei den geschlechtsreifen Mannchen
finden sich in 10, 11, 12, und 13 Segmente je ein Paar
wurmformig gewundener mit Spermatozoiden erfiillten
Schlauche (figs. 27 f, 28 c, 30a, 33a). Ihr worderes und
inneres Ende hat eine, wie es scheint, sehr feine Offnung, die
ich nur undeutlich geschen habe und vermittels welcher die
Spermatozoiden aus der Leibeshohle aufgenommen werden.”
Greeff seems, therefore, to have actually seen the internal
opening of the genital funnel of which Hering only suspected
the presence.

1 Describing Alciope Edwardsii, Krohn = cantrainii, Clap., Hering
writes as follows (19, p. 726):—‘‘ Das infundibulum jenes Organ (the ne-
phridium) liegt in der Nahe des Winkels zwischen Ruder und Pigmenthigel
nahe der Bauchwand; es hat bei beiden Geschlechtern einen wulstigen, an
den Randern stark lichtbrechenden gewundenen Saum. An letzteren bemerkt
man relative lange, strahlenformig angeordnete, scheinbar steife Harchen,
welche man fiir stark entwickelte Flimmerhaare halten wiirde, wenn sie
beweglich waren. . . . Die mit Samen gefillte Samenblase sicht man
allerdings leicht sowohl mit ihrem abgerundeten, scheinbar blind endendeu
vordertheile, als mit dem spitz auslaufenden hinteren Ende unter dem Pig-
menthiigel hervorragen (Fig. 3, Taf. ii, 5); ebenso lasst sich relativ leicht
der Canal, in den sie ausmiindet, besonders wenn er mit Samen gefillt ist,
bis bis zur nachst hinteren Ruderinsertion verfolgen, wo er, wie gesagt,
einwarts von derselben auf einer kleinen Erhebung der Haut sich nach aussen
Offnet ” (p. 727). And he adds concerning Alciope vittata = Asterope
candida, Clap. (p.751): “Ob die Samenblase in der Nahe des Infundibulums
ein blindes (vorderes) Ende hat, oder hier mit Leibeshohle communicirt, und
ob die etwaige Offuung mit dem Infundibulum in Beziehung steht, weiss ich
hier ebensowenig zu sagen wie bei Ale. Edwardsii (s. d.),”

706 EDWIN S. GOODRICH.

It is evident from the above quotations that although,
through the labours of Hering, Claparéde, Krohn, and
Greeff, the anatomical relations of the genital funnels in the
mature male Alciopids was known, the real structure of the
nephridium and its morphological relation to the genital
funnel were not understood.

Phyllodocine.

The Nephridium.—Like their allies the Alciopine, the
Phyllodocine have a closed nephridium, the inner blind end
of which bears a large number of solenocytes. In all the
genera I have examined, Phyllodoce, Hulalia, Eteone, Ptero-
cirrus, the inner extremity of the nephridium is more or less
branched, the solenocytes being distributed on the branches
in each case in a highly characteristic manner.

In Phyllodoce paretti, for instance, they form fan-like
bunches at the tips of the branches only (fig. 14). The
tubes are here almost as long as in Alciope, the cell-body and
its contained nucleus being perched on the distal end of
each. This little rounded cell-mass gives off no processes,
and contains a few highly refringent globules. There are
no external cilia on the ccelomic surface of the organ.

In most Phyllodocine, however, the solenocytes are ar-
ranged not only at the tips, but also along the whole length
of the terminal branches, as in Nephthys (11). These
branches may be fused at their bases, forming a broad
grooved plate-like organ, somewhat resembling the nephri-
dium of Glycera (12).

In the large worm Eteone siphonodonta, the nephri-
dium of which is just visible to the naked eye, there are an
immense number of solenocytes closely ranged in rows along
the grooves and lobes on the upper surface. As in Phyl-
lodoce paretti, the cell-body and nucleus is supported at
the distal free end of the somewhat conical tube (figs. 10
and 11). The nephridial canal gives off several main
pranches, which divide again into secondary branches, as in
the Glyceride.

THE NEPHRIDIA OF THE POLYCHATA. 707

In Eulalia viridis, Griffithsii, and punctifera, and
in Eteone lactea the general structure is similar; but the
nephridia are much smaller, and the number of solenocytes
much less.

Curiously enough Phyllodoce laminosa, amongst the
forms I have studied, is provided with solenocytes resem-
bling rather those of Glycera unicornis than of its nearer
allies. In this Phyllodocid the cell-body of the solenocyte
is oval, fixed by its base to the surface of the nephridium,
and connected by an elongated ‘‘ neck” with the top of its
flagellated tube (fig. 13). These cells are placed in rows
facing each other, and at the tip of each branch two of them
seem to be joined together by their cell-bodies, as is generally
the case in Glycera unicornis (12, fig. 9).

Numerous long cilia arise from the ccelomic surface of the
nephridium, between the rows of solenocytes, and by means
of their rapid movements serve to renew the fluid in the
neighbourhood of the tubes (fig. 13).

The Genital Funnel.—In the Phyllodocine the genital
funnel has much the same relation to the nephridium as in
the Alciopinz. Sections of immature specimens of Hulalia
show it as a bell-shaped organ, open in front, closed behind,
and formed of a deep layer of ciliated epithelium (figs. 27
and 17). It is so closely connected with the nephridium
that, during a part of its course, the latter is actually em-
bedded in the wall of the funnel (fig. 16), recalling the state
of things described in Nephthys (11), where the nephridial
canal runs through the wall of the ‘ciliated organ” (genital
funnel). Beyond the funnel the nephridial canal continues
alone to the nephridiopore (fig. 15). A longitudinal section
through these organs, in a well-developed but not mature
male Hulalia (fig. 28), shows that the posterior end of the
genital funnel becomes closely applied to the nephridial
canal, and that although at this point the walls of the two
are somewhat thinned out and flattened together, yet they
remain distinct and complete, allowing no passage from the
ccelom into the nephridial lumen.

708 EDWIN 8S. GOODRICH.

In similar sections of a mature male Eteone (figs. 18 and
29) it is seen that an opening has been formed at the point
of fusion; but the limit of the two different tissues is stall
quite plainly discernible. A passage has thus been formed
for the first time from the ccelom into the nephridial canal,
allowing the ripe spermatozoa to pass out to the exterior.

The history of the development of the genital funnel is the
same in both sexes, and in all the genera of the Phyllo-
docine I have examined. Some variation occurs with regard
to the shape of the fully-formed organ, which appears to be
larger and more folded in Eulalia, for instance, than in Eteone
(figs. 23 and 18).

Genital funnels are developed throughout the trunk region,
but dwindle, and finally disappear in the anterior segments,
where nephridia alone are present (from about the twentieth).
There appear to be a few segments in the adult, quite near
the head, where the nephridia themselves have disappeared ;
as, indeed, is generally the case in Polychetes.

Gravier, in his careful account of the anatomy of the Phyl-
lodocinee (18), figured and described their nephridia as simple
wide-mouthed organs, opening from the ccelom to the exterior
and serving as genital ducts. Finding my own results differ
so widely from those of M. Gravier, I examined the prepara-
tions he had worked at,! and found that, in fact, he had
missed the inner end of the nephridium, which is very diffi-
cult to recognise in fully mature specimens, where the ccelom
is filled with genital products and the genital funnel becomes
so much enlarged and so closely fused with the nephridial
duct. As I had surmised, the large-funnelled “ nephridia”
described by Gravier are the compound organs formed by
the grafting of the genital funnel on the true nephridium

(figs. 23 and 24).
Syllide.

My observations on this family of Polychetes, extending

1 T am much indebted to M. Gravier for very kindly lending me his sec-
tions.

THE NEPHRIDIA OF THE POLYCHATA. 709

over various genera and species (Haplosyllis spongicola,
Gr., Autolytus, Myrianida, Trypanosyllis, Pionosyllis, Syllis,
etc.), were made on fresh and preserved material chiefly
obtained at Naples and Plymouth.

Since much has already been written on the nephridia of
these worms by Khlers (6), Saint Joseph (23), Claparéde (2),
Malaquin (21), and others, it will only be necessary to dwell
in detail on certain points which seem to me not to have been
thoroughly elucidated.

In the immature Syllids the nephridium consists of a
slender tube opening externally on the ventral surface, and
internally into the coclom of the next segment in front by
means of a simple nephrostome. It is generally stated that,
at the time of sexual maturity, the nephridium becomes much
enlarged, and serves as a genital duct. Hhlers, in his im-
portant work on the Polycheeta (6), says that “diese Organe
(segmental organs) sind in zustande der Ruhe ausserst feine,
innen wimpernde Rohren mit einer unter der Basis der Fiiss-
hocker gelegenen ausseren, und einer in Mitte des Segmentes
miindenden innerer Offnung. Zur Brunstzeit entwickeln sich
die Organe zu sackartigen Behalten, welche durch aufnahme
der Geschlechtsproducte durch die innere Offnung bis zur
geanzlichen Anfillung des Segmentalraumes ausgedehnt
werden. Die Kntleerung der Hier und des Samens erfolgt
durch die aussere Offnung des Segmentalorganes” (p. 215).
Malaquin, in his ‘ Monograph of the Syllids’ (21), goes a
little further into detail :—“ La néphridie réduite pendant une
grande partie de la vie du Syllidien a un canal étroit, simple-
ment courbé en are et a trajet horizontal présente, a Vap-
proche de la maturité sexuelle, c’est 4 dire au moment ou les
produits des glandes génitales commencent a remplir la
cavité générale, un accroissement secondaire qui se manifeste
tout d’abord par une dilatation du canal néphridien ; puis par
une croissance longitudinale ce qui nécessite un reploiement
de la néphridie sur elle-méme. . . . L’entonnoir vibratile lui-
méme s‘%élargit de facon a laisser pénétrer facilement les
spermatozoides”’ (p. 280).

710 EDWIN S. GOODRICH.

Now I shall endeavour to show that the remarkable changes
undergone by the excretory organs at the time of maturity in
the fertile segments of those Syllids which do not form buds,
and in the segments of the reproductive buds, when they
occur, described by these and other authors, are really due
not so much to the mere enlargement of the true nephridium
as to the addition at its anterior end of a new growth, the
genital funnel.

In the immature condition the nephridia of all the Syllids
I have examined are of essentially the same structure,
differing only in certain unimportant details. In fig. 34
is represented the anterior end of the nephridium of Try-
panosyllis sp. The lumen of the canal is surrounded by
a wall of granular protoplasm containing many excretory
granules and vacuoles. Cilia are present here and there in
groups attached to the inner surface. In front of the septum
the canal projects, and ends by a small funnel, the lower lip
of which alone protrudes far into the ccelom, and bears a
flame-like bunch of cilia. Two nuclei can be detected, even
in the living worm, in the lower lip of the nephrostome. The
upper lip is not provided with cilia (fig. 34). It is formed of
a mass of closely-packed cells continuous with the ccelomic
epithelium of the septum. These are well seen in a section
through the nephrostome of an anterior nephridium of
Haplosyllis spongicola (fig. 37). In this species, how-
ever, small cilia appear to be present in this region also
(fig. 39). The lower lip of the nephrostome, as is well
shown in the latter figure, projects quite freely as a flattened
process.

In Syllis vivipara (fig. 36) the lumen of the nephridial
canal is surrounded by vacuoles, some of which at all events
open into it. Minute globules are also scattered about the
substance of the wall. These globules of varying size, and
the large vacuoles, appear to be formed by the accumulation
of fluid excretory products absorbed by the nephridial cells,
and passing into the lumen of the canal, whence they are
driven to the exterior by the cilia placed on its internal wall.

THE NEPHRIDIA OF THE POLYCHATA. rAal

At the level of the septum the excretory products cease to
appear, the tube becomes narrower, and then enlarges again
as it passes into the funnel. The nephrostome is here also
provided with a long lower lip, to which is attached a bunch
of long powerful cilia. There is shown a short upper lip
without cilia; but this may possibly be only the edge of the
lower lip seen in optical section, since I was unable to find it
in sections (fig. 85). It will be seen, then, that at this stage
the funnel of the nephridium has all the appearance of being
a true nephrostome—the open extremity of the nephridial
tube, continuous with it, and of the same substance. It
bears a strong resemblance to the nephrostomes of the
smaller Oligochetes, such as Enchytreeus (9).

If we now examine the structure of the excretory organ in
a fertile and genitally mature segment of a Syllid, we shall
find a very different state of things (figs. 20 and 38).

Sections of the mature organ show that the lumen of the
canal is somewhat enlarged, and often much distended with
genital products, but that its walls are otherwise little
changed in appearance, whilst in front of the septum, in
place of the little nephrostome, a large ciliated funnel has
become developed. The lip runs high up on the anterior
face of the septum, then curves round to meet below in a
projecting shorter lower lip. The funnel forms a large
trumpet-like opening to the nephridium, and its walls extend,
as those of genital funnels generally do, partly on to the
septum, and partly on to the body-wall (figs. 21 and 38).
The histological structure of this richly ciliated newly deve-
loped funnel is quite different from that of the true ne-
phridium—resembling, in fact, that of the genital funnels
described in the Phyllodocide above ; and it is sharply marked
off from the nephridium at the point where the nephrostome
was previously situated (fig. 30). The nephrostome can no
longer be distinguished. ‘he little mass of cells described
above (fig. 37) as situated over the projecting lower lip of
the nephrostome, must be regarded as the rudiment of the
genital funnel, strictly comparable to the rudiments shown

pil? EDWIN 8S. GOODRICH.

on the septa in the quite immature Goniada (12, Part II,
Pl. 35, fig. 33), or in the Phyllodocids. In these worms, as
in Syllids, the rudiments of the genital funnels in some of
the anterior segments amount to merely a few cells gathered
together just above the point where the nephridium is at-
tached to the septum.

No further development is undergone by the rudiment of
the genital funnel (in the non-reproductive segments) in such
forms as Haplosyllis, where ripe genital products are only
stored in the posterior reproductive buds; but in a mature
Pionosyllis, for instance, every stage is found, on passing from
before backwards, between a nephridial funnel to which the
coelomic epithelium appears to have contributed but little, and
the more posterior perfectly developed genital funnels which
have entirely superseded the nephrostomes (figs. 21 and 35).

Amphinomide|!

This account of the excretory organs of the Amphinomidee
is based chiefly on an examination of sections of Huphrosyne
foliosa, Aud. and Ed., from the coast of Normandy, and
Kurythe sp., from Ceylon.

Ehlers (6), describing the nephridia of HKuphrosyne
racemosa, says: “ Die Segmentalorgane finden sich fast in
allen Korperringen, denn ich sah sie ohne Unterbrechung bis
im zwanzigsten Segmente. Sie legen dort paarweise in
jedem zunichst unter der Riickenoberflache, mit ihrer 4usseren
Miindung am medianen Rande des Kiemenbesatzes. Jedes
dieser Organe ist eine langgestreckte zweischenklige Rohre,
die vom Aufhingepunct an der ausseren Mindung sich unter
der Riickenwand nach hinten wendet und wohl zwei oder
drei Segmente durchzieht. . . Wederan den Miindungen noch
im Lichten der Réhre habe ich Flimmerung gesehen ” (p. 78).

I must confess that [I am quite unable to confirm this
author’s extraordinary account, and am driven to the conclu-

1 Since I hope some day to be able to publish a description of the anatomy

of a large Amphinomid I obtained in Ceylon, the structure of the excretory
organs in this family will be only very briefly dealt with in this paper.

THE NEPHRIDIA OF THE POLYOHETA. “is

sion that, owing perhaps to the scarcity of the material at his
disposal, he has been entirely misled by appearances. Prof.
McIntosh, whose account resembles somewhat Ehlers’ de-
scription, does not seem to have been more fortunate.

The nephridia of the Amphinomide, as, indeed, we should
expect from the general appearance and structure of these
worms, resemble in all essential respects those of the Poly-
noine and their allies. They are, in fact, of the ordinary
large-funnelled type, formed most probably by the fusion of
the genital funnel with the nephridial duct.

In Huphrosyne the nephridia are paired organs, each
opening ventrally by a minute pore, just on the hinder edge
of the groove between the bases of two adjacent parapodia, at
a point marked * in fig. 40. The nephridial canal is some-
what large, slightly coiled, directed from the pore upwards
through the body-wall, then forwards to the region of the
septum, where a large number of muscles intersect the ecelom.
Coiling round some oblique muscles, it narrows, then opens
into a large trumpet-shaped funnel. The only peculiarity
about the nephridium of Huphrosyne is that this large funnel
opens backwards into the same segment that holds the
nephridial canal to which it belongs. Since the same thing
occurs in Hurythoe, it may be concluded that this position of
the funnel is characteristic of the family. Such a_back-
wardly directed opening of the genital funnel is not entirely
unprecedented amongst the Polycheta, since it has been
described by Claparéde in Hunice schizobranchia.

There is in the Amphinomids that marked histological
difference between the structure of the walls of the nephridial
canal and of the large coelomic funnel which we have found
in other cases. Here also, no doubt, the compound organ
fulfils the functions both of a kidney and of a genital duct.

FurtHer OBSERVATIONS ON THE HESIONIDA.

In Part I (11) I gave a description of the nephridium and
genital funnel (ciliated organ) of Tyrrhena and Hesione
(Fallacia). he structure of these organs in some other

714 EDWIN S. GOODRICH.

genera of the Hesionidz has proved to be of such remark-
able interest with regard to the connection gradually estab-
lished between the nephridium and the genital funnel, to the
substitution of the latter for the real nephrostome, and to the
formation of a compound organ—giving us a series of steps
bridging over the wide gap which separates the structure of
such a form as Nereis on the one hand, and the Syllids on the
other,—that I deemed it advisable to return to the considera-
tion of this family.

The two species I shall describe areO phiodromus flexuo-
sus D.Ch., from Naples, and Irma latifrons, Gr., for which I
am indebted to my friend Dr. Willey, who brought a number
of these worms back from New Guinea,

It will be remembered that in Hesione the nephridium
possesses its own nephrostome, which, however, is united with
the large genital funnel at one point (11, fig. 2). In Ophio-
dromus the genital funnel is much smaller (figs. 22, 25, and
26), at least in the specimens I have examined, which are not
quite genitally mature; but it is more intimately connected
with the nephridium, so completely surrounding the internal
opening of this organ that the nephrostome can scarcely be
said to exist as such any more (figs. 25 and 26).

Series of sections through young and mature specimens of
Irma show that the genital funnel becomes increasingly large
as age advances, until in quite ripe individuals it is very
extensive indeed, spreading over the large blood-vessels and
the inner side of the body-wall near the base of the parapo-
dium (figs. 19 and 50). The nephridium fuses with it, and
the compound organ so formed serves as a genital duct. In
the specimen figured, a ripe male, spermatozoa can be seen in
the nephridial canal on their way to the exterior.

The minute structure of the genital funnel in Irma, with
its numerous ridges on the ciliated surface, is exactly like that
of its homologue in Nereis and Hesione, which I called the
“ ciated organ” (fig. 19),

We have, then, in these genera Ophiodromus and Irma (to
which may also be added Kefersteinia) organs, acting both as

THE NEPHRIDIA OF THE POLYCHATA. 715

kidneys and as genital ducts, obviously formed by the
grafting of a large funnel on to the inner extremity
of an originally complete nephridium.

FURTHER OBSERVATIONS ON THE NEPHTHYIDA.

On examining some sections cut through a Nephthys ceca,
Fabr., which had previously been injected with some Indian
ink, I found that the amcebocytes of the ccelomic fluid,
charged with insoluble black particles, were accumulated at
the base of each genital funnel (ciliated organ), and were for
the most part enclosed in a sac formed by a double layer of
flat ccelomic epithelium (fig. 33). Into this sac enters the
ciliated organ, forming its posterior lining. The internal
end of the nephridium with its solenocytes lies quite near,
and rather above it; the nephridial canal passes just behind.
The sac is, no doubt, homologous with the “nephridial
sac”? of the Glyceride (12, p. 446), but it is a much less
differentiated organ, being merely a sort of pocket in which
the loose cells are accumulated by the action of the cilia of
the genital funnel, which thus brings together waste products
within easy reach of the nephridium.}

Polygordiide.

Adult specimens of Polygordius neapolitanus and P.
appendiculatus were studied at Naples and here in Oxford.
The only living larve I have been able to examine were
obtained by me at Trincomalee last summer, and belong to an
unknown species.

1 Since these observations were made, Mr. Stewart has published a paper
on the nephridium of Nephthys ceca (24), in which he describes the
accumulation of loaded phagocytes at the base of the genital funnel. He
does not, however, appear to have seen the sac, which was, perhaps, not
present in his specimen; and he believes the phagocytes to pass into the
lumen of the nephridial canal.

In this paper Mr. Stewart corrects the representation I gave of the vascular
supply of the nephridium in a diagram (11, fig. 8). The blood-vessel marked
d.l.v. should come off further from the nephridium, and the blood-vessel
marked ». /.v. nearer the ciliated organ—as shown in my figure 7 (11).

716 EDWIN S. GOODRICH.

The Adult Nephridium.—Already Hatschek (16) and
Fraipont (7) have given a detailed account of the nephridium
of Polygordius. In most respects I can only confirm their
description, but, with regard to the structure of the nephro-
stome itself, my observations do not quite agree with those of
Fraipont. He describes the nephridial canal as ending in
front in a funnel having a flattened brim of considerable
width, derived from the coelomic epithelium. In fact, in a
previous paper (10) I interpreted his description as favour-
ing the view that the excretory organ of Polygordius is, as in
so many Polycheetes, of double origin.

I have been, however, quite unable to find any trace of
such a peritoneal funnel in living or preserved specimens of
P. neapolitanus, although many of those I examined had
1 The nephridiuam
in this worm runs forwards just below the region where the
oblique muscles join the body-wall (fig. 47), and ends in front
of the next septum in a small nephrostome. Its short

nearly ripe genital products in the ccelom.

anterior lip projects into the ccelom, and is scarcely, if at all,
ciliated. The longer posterior lip, on the contrary, bears a
powerful bunch of long cilia (fig. 46). The nephridium of
P. appendiculatus appeared to be quite similar.

The Larval Nephridium.—In his very important work
on the development of worms, Hatschek described the so-
called head-kidney of Polygordius as a branched organ,
opening internally by small funnels provided with peculiar
stiff processes joined together by a web. Subsequently
Fraipont (7) showed that the branches are blind, that a large
nucleus is situated at the apex of each, and that the stiff
processes are hollow tubes.

I had long suspected that these structures were really of the
nature of solenocytes. It was not, however, till this summer
that I was able to confirm this surmise. On examining some
living larvee at Trincomalee, the general structure of the organ
was found to be very much as described by Hatschek and

1 The lumen of the nephridial canal is exceedingly small, being not only
narrower than the nucleus of the ovum, but even than its nucleolus!

THE NEPHRIDIA OF THE POLYCHATA. wd

Fraipont, but the hollow tubes have each a flagellum working
inside towards the nephridial lumen, and a long and slender
“neck” of protoplasm reaches to the distal end of the tube,
where it is slightly enlarged, and gives off fine irregular
processes, obviously comparable to those in the nephridium
of Nephthys (11). With the instruments at my disposal in
Ceylon I was unfortunately unable to make out for certain
the exact relative position of the tubes, the protoplasmic
“necks,” and the delicate web. Nor have I been able to
settle this difficult point with the help of sections. In fig. 48
these structures are drawn as I believe they really occur, but
this figure must be considered as to some extent provisional.

It will be seen at once that if this interpretation be correct
the nephridium of the larva of Polygordius differs in one
respect very remarkably from the similar closed nephridia of
Nephthys, Glycera, or Phyllodoce. Whilst in these there is
always one nucleus to each tube (forming one solenocyte), in
the larval kidney there are several tubes surrounding one
central nucleus.' As to the presence of this one large nucleus
at the tip of each branch, my observations only confirm those
of Fraipont and Meyer.

Notwithstanding this difference, the structures at the
inner extremities of the “head-kidney” of Polygor-
dius appear to be quite justly comparable to and
homologous with the solenocytes of Polychetes.
And the recognition of this fact is of considerable importance.
Hatschek has shown (and Meyer confirms his observation)
that the second nephridium in the developing Polygordius
has the same internal end, with solenocyte-like structures.
That this second nephridium is strictly homologous with the
third nephridium of the succeeding segment there can be no

1 Professor Edward Meyer has very kindly written to me on this subject,
enclosing several figures of the ‘‘ head-kidney ” of Polygordius, some of which
are, 1 believe, not yet published. Meyer confirms what is correct in the
descriptions of Hatschek and Fraipont, and has moreover discovered the
flagellum which works down the tube. But this tube he believes to be merely

a canal in the process of the cell, a prolongation of the nephridial lumen. He
therefore does not distinguish between a “tube ”’ and a “ neck.”

voL. 43, PART 4,—-NEW SERIES. DDD

718 EDWIN 8S. GOODRICH.

reasonable doubt. And so we are inevitably led to the view
that head-kidneys and posterior nephridia form one homo-
logous series of organs, a conclusion also reached by Meyer,
and in favour of which I have argued in a previous paper
(10). Two of the chief points, urged by those authors who
have attempted to show that the head-kidney is an organ sui
generis, are that it does not open internally, and that its
lumen branches. Now both these characters are common to
the nephridia of Nephthys and Glycera. Hither the head-
kidney is merely a precociously developed nephridium, or
Nephthys must be said to have a pair of ‘‘ head-kidneys” in
every segment of its body. A careful study of the first,
second, and third nephridium in Polygordius will, I think,
dispose once and for all of the view that the “ head-kidney ”
is not a true nephridium.

Summary of the Most Important Facts described in
Parts I, II, and III.

Puaytiopocipm® (Part III, p. 669).

Alciopine.—In Vanadis formosa the nephridia are
paired, slender, longitudinal tubes, opening ventrally near
the base of the parapodium, and continued forwards into the
next segment, where they end in a curved blind extremity.
Placed at intervals along the anterior third of the canal are
bunches of solenocytes. The cell bodies and nuclei of the
solenocytes are massed together at the free distal ends of the
tubes. Long flagella work down the tube into the lumen of
the canal, which is ciliated, and ends posteriorly in a slightly
dilated chamber before the external pore. Cilia are situated
on the coelomic surface of the nephridial duct, in the vicinity
of the solenocytes ; by their action they renew the fluid in
the neighbourhood of the tubes.

The nephridia of other Alciopids examined, Alciope and
Asterope, are of practically the same structure; but the

1 Part I appeared in vol. 40 (1897), and Part IJ in vol. 41 (1898) of this
Journal; see the table of contents at the end of this paper.

THE NEPHRIDIA OF THE POLYOHATA. 719

internal end is more or less branched, and the solenocytes
restricted to the branches.

No genital funnels occur in the quite anterior segments, in
a varying number of which nephridia alone may be present.
From about the ninth segment (Asterope) traces of the
genital funnel may be seen as a thickened ciliated patch on
the anterior face of the septum near the nephridium. Pass-
ing backwards, this increases in size, and bulges into the
segment behind in the form of a blind ciliated sac. In
Vanadis the funnel is long and almost tubular in shape. At
maturity the sac enlarges, becomes filled with spermatozoa
or ova, fuses with the nephridial canal about halfway down its
course, and finally opens into it, allowing the ripe genital pro-
ducts to pass to the exterior by the nephridiopore (Alciope).

Phyllodocine.—The nephridium closely resembles that
of the preceding sub-family ; but the blind internal end is
more branched, the lumen being even subdivided in some
cases (Eteone) into primary and secondary canals. The
solenocytes are generally set in rows chiefly on the dorsal
surface of the lobed extremity. In Phyllodoce Paretti,
however, they are grouped only at the tips of the branches.
In most cases the tubes of the solenocytes support the cell-
bodies at their distal free ends; but, in Phyllodoce lami-
nosa, the cell-bodies are bent round so as to rest on the
nephridium. In this species, also, cilia are developed on the
coelomic surface between the rows of solenocytes.

The genital funnels develop, except in a few anterior seg-
ments, as thickenings of the peritoneum lining the septum
dorsal to the nephridium, which become bell-shaped and
ciliated, grow backwards towards the nephridial canal with
the wall of which they become fused, and open at maturity
into its lumen. The ripe genital products are thus enabled
to escape through the nephridiopore.

Neputuyip& (Part I, p. 188, and Part III, p. 715).

The species Nephthys scolopendroides, and N. cxca,
have been studied. The nephridium consists of a long

720 EDWIN S. GOODRICH.

slender tube, opening ventrally to the exterior near the base
of the parapodium. It passes inwards, and forwards, to the
posterior limit of the next segment, where it ends blindly in
a tuft of from three to five branches. Along these branches
are set rows of solenocytes ; the tubes towards the inside, the
cell-bodies on the outside, joined together in pairs. A long
“neck” connects each cell-body, resting on the nephridium,
with the distal end of its tube. The granular protoplasm
of the “neck” is often drawn out into slender irregular
processes.

Situated quite near the nephridial tuft, so close that the
nephridial tube is embedded for a part of its course in its
posterior wall, is the rounded “ ciliated organ,” or incom-
plete genital funnel. Its ciliated surface is marked by deep
grooves converging downwards towards a point quite near
the epidermis at the intersegmental groove ; here also it is
closely connected with the nephridial duct.

In Nephthys ceca, at this spot the lower extremity of
the genital funnel passes into a sac, or pocket, formed by a
fold of ccelomic epithelium, in which are aceumulated ame-
bocytes loaded with waste products.

“Gtycerip# (Part II, p. 489).

In Goniada the nephridium opens ventrally to the exterior,
and ends internally in a tuft of short blind branches provided
with solenocytes. Goniada emerita has a large nephri-
dium of which the internal end has a much subdivided
lumen, and solenocytes placed in rows, as in the Phyllodo-
cine. The cell-bodies of the solenocytes rest on the surface
of the nephridium.

The genital funnel consists of a trumpet-shaped ciliated
organ, which develops rapidly at maturity, and finally fuses
with and opens into the nephridial canal to allow the genital
products to escape to the exterior by the nephridiopore. In
immature specimens the funnel is in a very rudimentary
state.

THE NEPHRIDIA OF THE POLYCHATA. 721

In Glycera the genital funnel is developed even in young
and immature specimens, and is not known to open to the
exterior at any time. It is situated in front of the septum,
provided with one long lip extending on to the body-wall in
some species, and with another lip leading into a sac. This
pouch of the celomic epithelium, which I have called the
nephridial sac, varies greatly in size in different, species.
Into it are driven floating cells from the cceloin by the action
of the cilia of the genital funnel. Thins waste material is
accumulated in the nephridial sac, brought there by amcebo-
cytes and by the red corpuscles or hematocytes, which may
also be both amceboid and phagocytal.

The nephridial sac is but little developed in Glycera
convolutus, much larger in G. unicornis, and best de-
veloped in G. siphonostoma. In the two latter species it
is provided with a cecal outgrowth, incompletely subdivided
into secondary chambers. Special granular cells are found
loose in the secondary chambers and main sac. The cacum
lies along the nephridial canal, and probably represents that
region of the funnel which in other forms is known to open
into the nephridium.

The nephridium itself is closely connected with the ne-
phridial sac. It is blind internally, and opens externally by a
pore on the ventral surface. The canal passes inwards and
forwards through the next septum to the genital funnel, and
then spreads over the nephridial sac, covering it more or less
completely. The lumen of the nephridium in this region
branches repeatedly, a spongework being formed by the
numerous primary and secondary canals. The latter dilate
at intervals into chambers, on the outer coelomic surface of
which are situated the solenocytes. These cells are thus
scattered over the inner extremity of the nephridium, which
itself spreads over the sac. In Glycera convolutus and
G. siphonostoma the solenocytes are arranged in small
groups of two, three, or more, the cell-bodies containing the
nuclei being supported at the free extremities of the tubes,
and resting against each other; but in G. unicornis they

722 EDWIN 8S. GOODRICH.

are placed in pairs, and the cell-bodies are fixed to the sur-
face of the nephridium.

PotyeorDiDH (Part III, p. 715).

The nephridium of the adult Polygordius neapoli-
tanus is in the form of a narrow tube running just below the
junction of the oblique with the longitudinal muscles. Be-
hind it bends towards the epidermis to open to the exterior ;
in front it opens into the next segment by means of a small
nephrostome, one lip of which only is ciliated.

There appears to be no definité trace of a genital funnel,
the genital products escaping by rupture of the body-wall.

The first nephridium, the so-called heaa-kidney, of the
trochosphere larva (described from an unknown species found
on the coast of Ceylon) has a branched internal end, each
blind branch of which is provided with a bunch of solenocyte
tubes surrounding a single nucleus.

HestionipH (Part I, p. 185, and Part III, p. 713).

Hesione (Fallacia) sicula has a nephridium which
opens ventrally to the exterior, passes inwards and forwards,
becomes considerably coiled, and finally ends just in front of
the intersegmental region by a small simple funnel opening
into the ccelom of the next segment. Connected with the
lip of the nephrostome by a narrow strip of epithelium is a
large crescentic genital funnel (ciliated organ), the ciliated
surface of which is marked by deep grooves. Those of the
middle region converge towards the lower extremity of the
organ, where it is connected with the nephrostome and with
the body-wall. The exact mode of exit of the genital pro-
ducts is unknown.

In Tyrrhena the nephridium is essentially the same; but
the genital funnel is smaller and more closely connected with
the nephrostome.

In Kefersteinia and Ophiodromus it completely surrounds
the inner extremity of the nephridium.

Finally in Irma, where the nephridium is no longer coiled,

THE NEPHRIDIA OF THE POLYCHATA. 723

the large genital funnel surrounds and fuses completely with
its inner end, forming a trumpet-shaped ccelomic funnel.
The genital products, collected together by the action of its
ciliated surface, pass down into the nephridium, and so to
the exterior by the nephridiopore.

Syiuip# (Part III, p. 708).

Those segments of Syllids from which genital products are
not expelled, the regions, whether sterile or not, in which at
all events the generative cells do not reach maturity, possess
a simple nephridium. It is a slender tube, opening into the
coelom by a small nephrostome, running backwards through
the septum into the next segment, where it reaches the ex-
terior on the ventral surface. The canal is ciliated more or
less continuously throughout, as in other Polychetes, and a
special bunch of long cilia is borne on the projecting lower
lip of the nephrostome. ‘he upper lip is generally repre-
sented by a little mass of closely packed cells, which is ap-
parently a thickening of the ccelomic epithelium, and the
rudiment of the genital funnel. In mature specimens of
those forms which do not reproduce by budding, and in the
ripe buds or reproductive regions of those which do, the
genital funnel becomes very much enlarged, extending up
the septum on to the body-wall, and surrounding the opening
of the nephridium. The original nephrostome is then no
longer distinguishable. The canal of the nephridium be-
comes much enlarged, and the whole organ functions as a
genital duct.

Ampuinomips (Part III, p. 712).

In these worms, of which the genera Euphrosyne and
Kurythoé have been studied, the nephridia are provided with
a trumpet-shaped funnel opening inwards and backwards.
The funnel passes forwards and downwards into the nephri-
dium, which is a short, thick, slightly coiled tube, running
backwards, and opening to the exterior ventrally by a minute

724 _ EDWIN S. GOODRICH.

pore in the inter-segmental groove near the base of the para-
podium, corresponding to the segment in which the funnel
opens. These organs function both as kidneys and as genital
ducts.

GENERAL CONCLUSIONS.

Hitherto in this paper I have scarcely ventured beyond the
domain of facts, but I now propose to point out some of the
more important theoretical conclusions which may be drawn
concerning the homology of the Polychete nephridium and
its relation to the genital funnel.

The Genital Funnel.—First of all as to the genital
funnel. Is it, as I have elsewhere contended (10), the mor-
phological representative of the genital ducts of other Anne-
lids? Or is it, as some would appear to believe, merely a
specialised portion of the nephridium, a much enlarged
nephrostome which may become separated off from its duct ?

For various reasons the first of these views seems to me to
be the only reasonable one. It is not advisable here to go
into the general question of the homology of the genital ducts
or funnels of the other Annelids, a subject which I have
already dealt with in some detail in the paper referred to
above (10), but it may be pointed out, that, where the
anatomy and development of the genital funnel in these forms
is understood, it is found to arise from the ccelomic epithe-
lium, being in fact merely a specialised, ciliated, funnel-
shaped outgrowth of the ccelomic follicle, designed to afford
an outlet for the ripe genital products.

From the facts described in Parts I, II, and ITI, and others
we were already acquainted with, we are now in a position to
state that in the Polycheta also a specialised, ciliated, funnel-
shaped segmental region of the ccelomic epithelium is deve-
loped, which forms a duct to lead the genital products to the
exterior. Moreover, that this funnel may secondarily acquire
other functions than the merely genital, and in this case is
generally early developed in the immature animal (Nephthys,
Glycera) ; that it may even occasionally cease to function as

THE NEPHRIDIA OF THE POLYCHATA. 725

Diagrams illustrating the relation between the genital funnel and the
nephridium in the Polycheta: A, hypothetical form with separate
genital funnel and protonephridium; 2B, Phyllodocide and Goniade ;
C, Nephthyide; D, Dasybranchus caducus; #, Dasybranchus
gajole and Tremomastus; F, Nereide; G, Hesione; H, Irma; J,
Syllide, Spionide, Terebellide, ete. The nephridium is drawn with
thick black lines, the genital funnel is shaded with thin cross-lines. ‘The
small circles represent ripe ova.

726 EDWIN 8S. GOODRICH.

a genital duct at all, no longer acquiring an opening to the
exterior, and in some cases dwindle away perhaps entirely.
On the other hand, that it may in various ways become
grafted on to the nephridium, and fulfil its primitive function
with the help of that organ.

Quite briefly the tacts are as follows :—In the Phyllodo-
cide the nephridium has no internal opening, but in most
segments a ciliated genital funnel, developed from the
coelomic epithelium, at sexual maturity fuses with and opens
into the nephridial duct. The compound organ thus formed
functions as a genital duct (Fig. B). In the Glycerida, in
some species (Goniada), the relations of the two organs is
found to be exactly the same as that described in the Phyllo-
docide (Fig. B). But in others (Glycera), the genital funnel
is not known to actually open into the nephridial canal; on
the other hand, it is known to accumulate waste products
near the nephridium, to develop early, and to persist in the
immature individuals, being active throughout lfe. The
method of exit of the genital products is still unknown.

In the Nephthyidz the nephridium is also closed
internally. The genital funnel is not known to acquire an
opening either directly to the exterior, or indirectly through
the nephridial canal. The mode of exit of the ova and
spermatozoa isnot yet known. The flattened genital funnel
is persistent throughout life, serving to collect waste products
in the neighbourhood of the nephridium (Fig. C).

In the Lycoridea, or Nereide, the genital funnel,
although larger than in Nephthys, has not been observed to
acquire an external pore (Fig. F). It is quite independent of
the nephridium, which has a real open nephrostome of its
own (8).

The Capitellide have nephridia with true nephrostomes.
The genital funnel in some forms (Dasy branchus caducus)
is quite independent, acquires at maturity a pore to the
exterior, and functions exclusively as a genital duct (Fig. D).
In others the edge of the lip of the genital funnel may
become connected with the nephrostome (Dasybranchus

THE NEPHRIDIA OF THE POLYCHATA. 720

gajole and Tremomastus, Fig. HE) ; but even in this case the
funnel still develops an opening to the exterior, through
which alone the genital products are shed. Lastly in
Clistomastus, where the generative cells escape through the
rupturing of the body-wall, the genital funnels are found only
in a more or less rudimentary state, and do not normally open
to the exterior.

In figs. 31 and 32 I have represented some transverse
sections of Notomastus latericius, showing that in this
species the large genital funnels open to the exterior (at the
level marked by an asterisk *), and are quite independent of
the nephridium and its nephrostome, several sections inter-
vening between the end of the latter and the beginning of
the funnel.

The Hesionidz present some very important variations
of structure. Hesione (Fallacia) has a very large genital
funnel, not known to open to the exterior; but which is
connected at one point with the open nephrostome of the
nephridium. The exit of the genital products has not been
observed (Fig. G).

In the genera Tyrrhena, Ophiodromus, and Irma, we find a
gradually closer and closer union established between the
funnel and the nephrostome. In Irma, where the genital
funnel is very well developed, it is so completely fused with
the nephridium that the two organs can no longer be dis-

1 These facts concerning the Capitellide are all drawn from Hisig’s mono-
graph (5). The case of Clistomastus is so important in connection with
Nereis and the Hesionids that his statements deserve to be quoted at length.
About Clistomastus Hisig writes, page 146 :—‘ Aber—in einzelnen Falhen sind
doch Spuren der Schlauche .... in den letzten drei Thorax-Segmente
vorhanden. Diese Spuren sind erstens auf die Liebeshohle beschrankten und
stellen dann peritoneale Wucherungen dar, die zwar noch an die Form der
Genitalschlauche erinnern, aber doch jedweder ausseren Mindungen entbehren.
Zweitens kénnen diese Spuren umgekehrt ansschiiesslich aus mangelhaft
ausgebildeten Poren bestehen, welche den Hautmuskelschlauch nich durch-
brechen oder, wenn sie das thun, doch nur in tiberaus kleine und undeutlich
ausgebildete Genitalschlauche tibergehen .... In noch setteneren Fallen
endlich . . . erreichen aber auch bei Clistomastus die Genitaschlauche eine
vollkommenere ausbildung.”

728 EDWIN S. GOODRICH.

tinguished (excepting, of course, by their histological
structure and position). The nephridium thus acquires a
large trumpet-shaped opening into the ccelom, and functions
both as a genital, and as an excretory duct (Fig. H).

In young Syllide the genital funnel can scarcely be said
to exist, being represented only by a few crowded cells in
the ccelomic epithelium on the anterior face of the septum,
just above the opening of the small nephrostome into the
celom. In those Syllids, like Autolytus, Myrianida, and
Haplosyllis, which become differentiated into vegetative and
reproductive regions or buds, the genital funnel advances
little beyond this very rudimentary stage in the regions from
which genital products are not extruded. But in the seg-
ments from which the mature genital cells are shed, the
genital funnel develops into a large trumpet-shaped organ
fused on to the anterior end of the nephridium. The canal
of the latter becomes dilated, and through this compound
structure ova or spermatozoa pass out to the exterior (Fig. I).

In the remaining great families of the Polycheta—the
Eunicides, Amphinomide, Aphroditide, Spionide, Arenico-
lide, Terebellide, Sabellide, and their allies—the excretory
organs are always provided in the adult with large funnels
opening into the ccelom, and function as a rule both as renal
and as genital ducts. The structure of these organs is
sufficiently well known, through the labours of Ehlers (6),
Claparéde (2), Cosmovici (8), Cunningham (4), Meyer (22),
and others, not to need a detailed description in this paper.!
In all essentials they very closely resemble the compound
nephridia of such a form as Irma (Hesionid). The upper
lip of the funnel usually extends for a considerable way
on the anterior surface of the septum (when it is present)
and on the body wall (fig. 21). In some worms the anterior
organs alone may act as genital ducts, as in the Polynoine

1 T have recently investigated the structure of the excretory organs of
Saccocirrus ; but since it appears to be a very highly modified form, and does
not seem to throw much light on the general question here discussed, I shall
reserve my description for a future paper. For Polygordius see p. 715.

THE NEPHRIDIA OF THE POLYCHATA. 729

(Trautzsch, 25), the Opheliide, etc. In others, on the con-
trary, the posterior organs may be exclusively genital in
function, as in the Terebellide, Sabellide, etc. In such
cases, the organs which excrete have the glandular canal more
highly developed ; whilst those which act as genital ducts only
have the funnel region enlarged, and the nephridium reduced.

Now, if we seek for an explanation of these facts, we are
driven to the conclusion that, in a large number of
Polychetes, the so-called “segmental organ” or
“nephridium” is in reality formed by the fusion
of a true nephridium with a genital funnel; two
organs which in certain other Polychetes,' in all other Anne-
lids, and indeed, so far as we know, in all other Coelomates
have always remained distinct.

That the nephrostome in the Oligochetes and Hirudinea
belongs to the true nephridium, and is developed with it
from the same rudiment, has now been proved over and over
again (see 10); that, similarly, the nephrostome in the
Nereide and Capitellide belongs to the true nephridium
there can be scarcely any doubt, although the steps in its
development have not yet been so carefully followed?; that
the wide funnel on the anterior end of the segmental organs
of the Amphinomide, Hunicide, Aphroditide, Spionide,
etc., does not represent the nephrostome, but is the genital
funnel, an organ originating from the ccelomic epithelium
separately, seems almost equally certain; and, indeed, may
be considered to have been proved by Meyer (22) in the case
of the Tubicolous worms.

Unfortunately we have, as yet, no evidence with regard to
the development of these organs in the other families. I can
only add one observation of interest in this connection.

The nephridium of the pelagic larva of Arenicola® is

1 These are, of course, the Nereide (Lycoridea) and some Capitellids.

2 Hd. Meyer has figured the development of the nephrostome of Nereis
from the extremity of the blind larval nephridium (22).

3 First described by Benham, who was unable to find the nephrostome (1).
Since this was written, Messrs. Gamble and Ashworth have described this

730 EDWIN S. GOODRICH.

provided with a small funnel, evidently a true nephrostome,
projecting and opening into the ceelom (fig. 49). Its fringed
lip, with ciliated protoplasmic processes, bears a remarkable
resemblance to that of Nereis (8, and this paper figs. 41, 42,
and 44). It seems but reasonable to suppose that this organ
can be converted into the wide-mouthed “ nephridium” of
the adult worm only by the addition of a genital funnel
derived from the ccelomic epithelium.

The comparison between the large funnel of the excretory
organs of such a worm as Eunice (fig. 21), and the genital
funnel of the Capitellide, might seem, at first sight, some-
what strained and fanciful. But the two structures are so
similar in structure and function, and the intermediate steps
(Hesionidee, etc.) are so complete, that no other view seems
now to be admissible. Although I do not wish to lay too
much stress on histological similarity, and such resemblances
may perhaps rarely be sure guides to the identification of
homologous organs, yet, I think it will be admitted, that the
presence of the peculiar and almost identical ciliated ridges
on the surface of the large funnels of such widely separated
forms as Nephthys, Nereis, Fallacia, Hurythoé,! and Tere-
bella, can scarcely be due to mere coincidence.

Moreover, it must be remembered that the two organs are
mutually exclusive: never do we find a separate genital funnel
in those forms which possess wide-mouthed excretory organs ;
and conversely, with the one possible exception of Polygor-
dius,” never do we find Polychetes having nephridia with
only small true nephrostomes without genital funnels.

The fact that no external pore has been found to the
supposed genital funnel of the Nereids and Glycera cannot

*‘post-larval stage,” denying the presence of a nephridial funnel (“ The
Anatomy and Classification of the Arenicolide,” ‘Quart. Journ. Mic. Sci.,’
vol. 43, 1900). LIcan only state that funnels were certainly present in the
specimen I examined at Plymouth, and moreover that the ciliated processes
have nothing to do with the ciliated folds of the adult organ.

1 An observation I made on a large species dissected fresh.

2 See pp. 715 and 734,

THE NEPHRIDIA OF THE POLYCHATA. 731

be urged as a weighty objection to the homology, since any
day such an opening may be discovered by some observer
fortunate enough to find these worms in the act of shedding
their genital products. If such a pore does not exist at all
we have a ready explanation at hand in the already quoted
example of Clistomastus (p. 726), where its absence is un-
doubtedly due to degeneration of the genital funnel, accom-
panying the adoption by this worm of another method of
shedding its germ-cells.

The position, then, is this: we find two separate organs in
the Oligochzta, Hirudinea, and some Polycheta, the one
excretory, the other genital. I contend that they are respec-
tively homologous in the three groups. Surely the burden
of the proof lies entirely on the side of those who would deny
this homology. If the genital funnel of the Polycheta
be merely a secondary derivative of the nephridium, not
homologous with the genital duct of the others, then it
should be explained why the latter duct is absent in these
worms, and we might even reasonably expect to be shown a
trace of it in some family.

To answer that in the Oligochetes and Hirudinea them-
selves these genital ducts are merely modified nephridia or
their derivatives, is only to throw the question back a step
farther. For then it may be asked, where are the represen-
tatives in the Annelids of the genital ducts of the Platy-
helminths and Nemertines? What has become of these
ducts, have they disappeared, leaving no trace behind them,
to be replaced by organs of exactly similar relations, but not
homologous ?

Perhaps a stronger argument still against such a view, is
that it is directly opposed to the evidence of comparative
anatomy and embryology, which goes to show that, as a
matter of fact, the genital ducts or funnels are not modified
nephridia at all, and have originally nothing to do with
nephridia ; that their function is, and always has been pri-
marily that of carrying the genital products to the exterior,
and that consequently they must always have been in con-

732 EDWIN S. GOODRICH.

tinuity with the coelomic epithelium, and in open communi-
cation with the ccelom (10).

The connection between the nephridium and the
genital funnel:—From the brief review of the facts given
on page 725, it will be gathered that the combination of the
genital funnel with the nephridium is of three different
kinds.

According to the first mode of union, the funnel fuses with
and opens into the canal of the closed nephridium: in
Phyllodocide and Glyceride.

According to the second mode, the funnel, whilst preserv-
ing its original opening to the exterior, may be connected
by the edge of its lip with the nephrostome: in some Capi-
tellidee.

Finally, in the Hesionide, the funnel, losing its external
pore, surrounds and opens into the extremity of the nephri-
dium.

It may now be asked, what is the nature of this connection ?
How far is it really similar in the three types, and is it likely
to have happened independently in these three cases ?

So far as one can judge from the facts now known, and
without a knowledge of the development, it seems probable
that the first mode of union (in the Phyllodocids and Gly-
cerids) was brought about by the gradual approximation of
the originally distinct openings of the funnel and nephridium,
until the two organs opened together, and that the opening
of the genital funnel shifted farther and farther up the
nephridial canal, until it acquired its present position.?

In the case of the Capitellide, the connection between the
two organs is, after all, not very close. It consists in a

1 Of the mere shifting of the pores of both the nephridia and the
genital funnels, we have ample evidence in the Annelids; and that the peri-
toneal funnels have a peculiar tendency to fuse with adjacent tubes is shown
in the case of the sperm-ducts of Oligocheetes and Leeches, and of the pro-
nephric funnels of Vertebrates. Long ago, Nussbaum (‘ Arch. mikr. Anat.,’
vol. xxvii, 1886, p. 466) showed that the mesonephric funnels fused with and
opened into the blood-vessels of Amphibia.

THE NEPHRIDIA OF THE POLYCHATA. 733

running together of their lips, the functional meaning of
which is not clearly understood. There is little difficulty in
supposing that it has been independently acquired, and is
peculiar to the family.

The exact mode of origin of the connection between the
nephrostome and the genital funnel in the third group is
more difficult to determine. It might conceivably have come
about, as indicated above for the Phyllodocide, by a gradual
approximation of two originally distinct apertures, and the
subsequent shifting of the genital funnel on to the tip of the
nephridium ; or, as in the Capitellide, by the fusion of the
lips of the two organs, followed by the loss of the primitive
genital pore. On the whole, I am inclined to think that
neither of these processes was the one adopted in this case ;
but that the connection took place owing to the nephrostome
itself becoming so closely situated to the end of the genital
funnel, as the latter grew towards the epidermis at maturity,
that a fusion took place, leading to the grafting of the
genital funnel on to the internal extremity of the nephridium.!
The genital products then passed down the nephridial canal,
instead of directly to the exterior. It will be noticed that
the nephrostome of the Hesionide is situated very close to
the body-wall. This interpretation seems to be supported by
Meyer’s description of the development of the excretory
organs of Polymnia (22), where the inner end of the ne-
phridial rudiment is represented as fusing with the apex of
the developing funnel.

Judging by the very similar final results obtained, it is
from some such mode of union as this which has been de-
monstrated in the Hesionide, that the compound large-
funnelled excretory organs of the majority of Polychetes
(Syllids, Eunicids, Aphroditids, Amphinomids, etc.) have
been formed.

The consideration of the structure and homology of the

1 The usefulness of the ciliated genital funnel in accumulating waste pro-
‘ducts in the neighbourhood of the nephridium has, no doubt, in all three
eases contributed to bring about the “ rapprochement.”

VOL, 43, PART 4, —NEW SERIES, EEE

734 EDWIN S. GOODRICH.

nephridia themselves, to which we may now turn, will afford
further evidence in favour of the views advocated above.

The Nephridium.—lIt will be readily seen from the facts
summarised above that three distinct types of nephridia are
found amongst Polychzete worms.

The first type, found for instance, in Alciope, has no
internal opening. The second type, as in Nereis, opens
into the ccelom by means of a true nephrostome. The third
type, as in Polymnia, is a compound organ, formed by fusion
with the genital funnel.

Which of these three types is the most primitive? Are
they to be looked upon as three stages in the development
of any one of them, or as three divergent forms derived
from some ancestral type? These are some of the questions
which immediately suggest themselves, and it will help us to
answer them if we first consider an objection that may be
raised against the arguments put forth above with regard to
the secondary nature of the connection between the ne-
phridium and the genital funnel.

It may, indeed, be said that the facts can be interpreted in
exactly the reverse order.

That, in the Phyllodocide, Capitellide, and Hesionide,
for example, we are not dealing with nephridia which be-
come gradually more and more closely connected with the
genital funnel; but, on the contrary, that the wide-mouthed
“nephridia” of the Spionide, Terebellide, etc., represent
the primitive condition of things, and that we can observe in
the series described the gradual separation from its duct of
the nephridial funnel, and its subsequent acquisition of an
opening of its own to the exterior for the extrusion of the
genital products.!

1 Those who support the view that the separate genital funnels in the
Polycheeta are not primitive organs, might point to Polygordius as an example
of a primitive form in which these funnels have not yet become separated off
from the nephridium. But such a statement, if acecpted, would prove too
much. For if Polygordius really occupied the position assigned to it near
the base of the Annelid stem, it is surely in this of all worms that we should
expect to find the nephridium opening into the ceelom by means of a wide

THE NEPHRIDIA OF THE POLYCHATA. 735

It will be seen at once, however, that the adoption of such
a view as this would lead us into a maze of difficulties, from
which there appears to be no escape, if our theories concern-
ing the Polychete nephridium are to be at all consistent with
well-established conclusions concerning the structure of allied
groups.! Take the case of the Phyllodocids, for instance.
It would have to be supposed that in these worms the ori-
ginal funnel became separated off, that the truncated ne-
phridial canal acquired a highly complex, closed, branching
extremity, and that the funnel became again grafted on at
maturity to reassume something of its original relations and
function. For all this there is, of course, not a scrap of
evidence. Moreover, it is directly opposed to such evidence
as we have from the study of development, that the further
we go back, the earlier the stage investigated, the less close
is the connection between the nephridium and the genital
funnel (Part II, p. 454, Part III, p. 702).

Far more natural is it to compare the closed, generally
branched, nephridia of Phyllodoce, Nephthys, and Glycera,
with the branched organs ending in flame-cells found in the
Platyhelminths, Rotifers, and Nemertines (see p. 738 below).
The solenocytes, indeed, appear to be comparable only to
flame-cells. Such, at all events, must be the conclusion
until a knowledge of their development warrants another
opinion.

This view is further supported by the knowledge that
many nephridia, which in the adult condition open into the
ccelom, pass through a ‘ protonephridial” stage with closed

funnel, and acting as a genital duct. Now this is just what is not the case in
Polygordius. Here the genital products escape by rupture of the body-wall,
and the nephridia have only small nephrostomes (p. 715).

Moreover, there really appears to be nothing in what we know of the
structure of these worms which warrants any other view but that they are
a specialised offshoot from the Polychate stem. And it may be pointed out
that some of those very authors who would consider them as primitive
Archiannelids, associate them wrecklessly with forms like Dinophilus and
Saccocirrus, where the genital ducts acquire an unusual complexity,

1 See also p. 730, and my general paper (10),

736 EDWIN S. GOODRICH.

internal end.!. The nephridium of the first segment, the so-
called “ head kidney,” in the majority of Polychztes never
passes beyond that stage. The discovery of solenocytes in
the “head kidney” of Polygordius is of some importance in
this connection (see p. 717).

As for the second type of nephridium, it appears to have
been developed within the Polychete group by the opening
of the true nephridium into the celom. This is actually
what happens in the development of Nereis (Meyer, 22).
Such an opinion may, perhaps, commit us to the conclusion
that the nephridium has acquired an opening into the
ccelom independently in the Oligochzetes and the Polycheetes.
This would be an objection, no doubt, but, whatever may
be thought of this difficulty, it is clearly much less than the
many difficulties to be met by the opposite view.

The third type of organ has been already dealt with (p.
728) and explained as the result of the fusion of the genital
funnel with the nephridium.

The strictly provisional conclusion we have arrived at,
therefore, is that, although the third type of excretory organ
may conceivably have been derived from the second, the first
type must represent a survival, possibly highly specialised, of
the protonephridial ancestral form without communication
with the ccelom.

The Solenocytes.—Lastly, let us discuss those peculiar
structures which I have termed solenocytes. ‘Typically they
consist of a cell-body, containing a deeply staining rounded
or oval nucleus, attached by a sort of neck to the extremity
of a thin tube which opens at its opposite end into the lumen
of the nephridial canal. The tube may be long, narrow, and
of almost even diameter, as in most Phyllodocids (figs. 3
and 9) ; or comparatively short, conical, and compressed with
fluted sides, as in Glycera (Part I, figs. 9 and 14). It
appears to be formed of a dense cuticular substance, and
may project far into the lumen of the nephridium (figs. 2
and 9). Working inside the tube and attached at its distal

1 Tn Oligochetes and Hirudinea, as well as Polychetes.

THE NEPHRIDIA OF THE POLYCHATA. 137

end is a single long flagellum, which passes far down the
nephridial canal; the movements of the flagellum are such
as to propel liquid down the tube towards the external pore.

In the majority of cases the cell-body hangs freely in the
coelom, supported at the tip of the tube (figs. 11 and 14).
The solenocytes then generally become grouped together for
mutual support (Part II, fig. 14) ; or the cell-bodies may even
be fused into large masses, as in the Alciopids, the individual
cell-outlines being lost (figs. 2 and 9). In other cases the
cell-body is bent round so as to rest on the surface of the
nephridium, an elongated neck connecting it with the distal
end of its tube (Part I, fig. 26; Part Il, fig. 9; and this
Part, fig. 13). Such cells are usually joined together in
pairs, more or less fused.

The protoplasm of the solenocytes is generally finely
granular, occasionally with refringent globules (Phyllo-
doce paretti, fig. 14); but, as a rule, singularly free from
concretions or granules of excretory matter. Indeed, ex-
periments seem to show that they are not concerned with the
excretion of such waste substances (Part II, p. 452). Often
fine, irregular, probably amceboid processes are given off from
the cell-body (Part II, fig. 4), or from its neck (Part I, fig. 26).

The distribution of the solenocytes varies considerably.
In Vanadis (fig. 1), where the nephridium is unbranched,
they are placed in bunches along the anterior third of its
course. In Alciope cantrainii (fig. 3), and Phyllodoce
paretti (fig. 14) they are grouped only at, or near the tips
of the branches of the nephridial canal. Nephthys (Part I,
fig. 26), and most Phyllodocids in which the nephridium is
branched, have the solenocytes ranged in regular rows
facing each other, so to speak, along the whole length of the
branches, On the contrary, in Glycera, where the nephri-
dium spreads out in a flattened mass, they are iregularly
scattered in small groups over its coelomic surface (Part II,
figs. 14, and 29). Intermediate forms between these ex-
tremes are also found.

Sometimes cilia are developed in the Phyllodocide close to

738 EDWIN S. GOODRICH.

the solenocytes, on the surface of the nephridium, by the
action of which the surrounding liquid is kept in motion. In
Alciope cantrainii these cilia work regularly between the
tubes, placed in short transverse rows to facilitate this move-
ment (figs. 3 and 4). The proximity of the solenocytes to
the ciliated persistent genital funnels, in Nephthys and
Glycera, and the general circulation of the ccelomic fluid in
the latter genus, probably render the development of external
cilia unnecessary in these forms.

With our present lack of knowledge of the development of
the solenocytes, we can do little more than make a rough
guess at their homology. As has been shown above, p. 735,
there seems to be little doubt that the nephridia of the
Phyliodocids, Nephthyids, and Glycerids are primitive in
being closed internally, that they have never been otherwise
than closed, and must, therefore, be compared with the
“ protonephridia” of the Platyhelminths, Rotifers, and
Nemertines. Anyhow the solenocytes themselves can be
more readily likened to flame-cells than to any other struc-
tures described in the excretory organs of the Annelids, or
their allies. Indeed, if we carefully compare these cells with
the flame-cells described by Biirger (1 a) in the Nemertines,
the resemblance is seen to be more than superficial. In both
cases there is the same tendency to the grouping of the cells
in bunches, the same shape and position assumed by the cell-
body at the extremity of a narrow canal in which the cilia
work ; and the processes drawn by Birger as arising from

these cells, may perhaps be compared with those seen in
Nephthys.?

1 There is a strange resemblance between the solenocytes and the peculiar
cells described by Boveri as surrounding the openings of the excretory tubules
in Amphioxus. Some years ago, I examined these tubules in fresh specimens,
and came to the conclusion that the resemblance is only superficial. In
Amphioxus, the straight processes converging towards the ccelomic openings
appear to be solid protoplasmic rods (perhaps modified cilia), not tubular
structures opening into the lumen of the kidney-tube, as in the case of
solenocytes.

* In this general discussion I have made no mention of the solenocytes in

THE NEPHRIDIA OF THE POLYCHATA. 739

It may, therefore, be concluded that, so far as our present
knowledge allows us to judge, the closed nephridia and
solenocytes of the Polychewtes are probably homo-
logous with the protonephridia and flame-cells of
the Nemertines.

The Importance of the Nephridium in Classifi-
cation.—Hitherto the classification of the Polycheta has
been based chiefly on external resemblances, and the struc-
ture of the alimentary canal. That the nephridium and
genital funnel must also be taken into account, will, I think,
be owned by anyone who has read the description of these
organs given above. A superficial glance at the variations
occurring in their structure amongst the Polycheta, might
perhaps lead one to suppose that the genital funnels and
nephridia are too variable to afford reliable material to the
systematist. The extraordinary plasticity of the nephridium
in the Lumbricidz, made known to us through the researches
of Perrier, Beddard, and Benham, might encourage this
view ; but it must be remembered that, even in the Lum-
bricidz, although the nephridia vary immensely in the
relative development of their parts, and in the number and
position of their openings, yet they throughout maintain a
definite Lumbricid character, a family resemblance. More-
over, in each of the other families of the Oligocheta, the
nephridium assumes a more or less characteristic type of
structure, so that a worm could as surely be identified as
belonging to the Enchytreide, for instance, by the exami-
nation of its nephridium, as by that of any other part of its
body (see Vejdovsky [26] and myself [9]).

In the same way, amongst the Polycheta, although im-
portant differences in the relative development of the parts
of the nephridium undoubtedly occur, yet the type of struc-
ture remains very constant within the families themselves.
For example, in the Lycoridea (Nereidz), the nephridium is

the “head kidney ’’ of Polygordius (p. 716), since I have been unable to
ascertain for certain the exact detailed structure of these very aberrant
organs.

740 EDWIN S. GOODRICH,

always, so far as I have been able to ascertain, formed of a
bulky mass enclosing a coiled canal opening into the ccelom
by means of a small funnel, the edges of which are provided
with ciliated processes. The shape, disposition, and number
of these processes, and of their cilia, differ in the various
genera (or sub-genera) and species; but each is charac-
teristic of the species to which it belongs, and again the
general structure of the nephrostome is characteristic of the
family Lycoridea. For purposes of comparison, I have given
the nephrostomes of the Nereids Lipephile cultrifera, Gr.
(figs. 44, 45), Praxithea irrorata, Mgr. (fig. 41), Eu-
nereis longissima, Johnst. (figs. 42, 43). That of Alitta
virens, Sars, has already been figured by Cunningham (4),
and of Nereis diversicolor, O.F.M., and Nercilepas
fucata, Sav., by myself (8). Similarly in all the Phyllo-
docidze examined, the nephridium was found to be of
essentially the same structure; and the same may be said of
the genital funnel. It is evident that these organs cannot be
neglected in classification.

Tabular Statement of the Relation of the Nephri-
dium to the Celom, and to the Genital Funnel
in the Polycheta.

closed into nephridial canal may be ac- | Glyceride.
internally. quired at maturity. Nephthyide.

Genital funnel with independent ex- | See

Nephridium Genital funnel distinct, but ‘ele |e

t ; ? Nereide (Lyco-
ernal opening. idea)
ridea).

Hesionide (all ?).

Nephridium Syllidee.
open Genital funnel becomes connected Aphroditide.
internally. with the nephrostome, and loses } Bunicide.
its primitive opening to the exte- | Spionide.
rior. Terebellide.
Sabellide.

Ete. etc.

THE NEPHRIDIA OF THE POLYCHATA. 741

From this table it will be seen that the Polycheeta fall into
two main groups: the first having closed ‘“ protonephridia,”
the second provided with nephridia opening into the ccelom.
This last may further be subdivided into those in which the
genital funnel retains its independent opening to the ex-
terior, and those in which this opening has been lost. The
latter may again be classed according to the extent of the
fusion between the funnel and the nephridium, which gra-
dually entirely loses its own nephrostome.

I should not, of course, propose to base a new classification
on our present knowledge of these organs, and the table
must not be taken to represent an attempt at a phylogenetic
classification. Yet it is clear that these results must be
taken into consideration in reforming the classification of the
Polycheeta.

In conclusion it may be pointed out that, whereas in most
Annelids, and so far as we know in all other Coelomata, the
genital funnels remain distinct from the nephridia even
when they replace them in function (Mollusca) ; in the Poly-
cheeta alone they become variously connected with each
other, and in the majority of cases the genital funnel be-
comes so intimately fused with the nephridium to form a
compound excretory and genital duct, that a study of the
adult anatomy alone of these worms would probably never
suggest that the organ is formed by the grafting of the one
on to the other.

The Polychete segment, then, is provided with two organs,
the one a genital duct, the other an excretory nephridium.
In some cases these organs remain separate, but in most
Polycheetes a connection is established between them, a fusion
takes place, and the resulting organ may fulfil either or both
of their primitive functions.

Propos—ED NOMENCLATURE.

The excretory and genital ducts of the Polychaeta have
proved to be of so complicated a structure that it becomes
necessary to revise the nomenclature to avoid confusion, and

742 EDWIN 8S. GOODRICH.

to enable us to compare these organs with their homologues
in other Ccelomata.

To the genital duct of ccelomic origin in general the name
ccelomoduct! may be applied. For its special funnel-like
opening, which I have variously designated by the descrip-
tive terms “ciliated organ,” “ genital funnel,” and “ peri-
toneal funnel” (8, 10,11, and 12), I propose the name ceelo-
mostome.

When, as in the Annelids, the ceelomostome still fulfils its
primitive genital function, it may be termed, more particu-
larly, the Gonostome.

For the primitive excretory organ, such as is found in
Nereis or Capitella, the name Nephridium must of course
be retained, and its coelomic opening called the nephri-
diostome; but, for its closed representative in the Neph-
thyide, Glyceride, and Phyllodocide, and for closed “ head-
kidneys,” the term Protonephridium might, perhaps, be
used with advantage. It is the name proposed by Hatschek
for the closed nephridia of the Platyhelminths. ‘lhe tube-
bearing cells have already been called Solenocytes (‘ Proc.
Int. Congress Zoology,’ 1898, pp. 196 and 12).

The ordinary wide-mouthed segmental organs of the Poly-
cheeta, formed by the fusion of the nephridium with the
genital funnel, may be called Nephromixia.' Thus a
nephromixium = a nephridium + a ccelomostome.

List oF WORKS REFERRED TO.

1. Benuam, W. B.—‘The Post-larval Stage of Arenicola marina,’
‘ Journ. Marine Biol. Assoc.,’ vol. i, 1893.

la. Binerr, O.—‘ Die Nemertinen,”’ ‘Fauna und Flora des Golfes von
Neapel,’ vol. xxii, 1895.

2. Cuaparbpr, A. RK. E.—‘ Annélides Chétopodes du Golfe de Naples,’
Geneva, 1868, and supplement, 1870.

3. Cosmovici, L. E.—‘“ Glandes génitales et organes segmentaires des Anné-
lides Polychétes,” ‘Arch. Zool. Exp. et gén.,’ vol. viii, 1879—1880.

1 Kindly suggested to me by Professor EH, Ray Lankester.

THE NEPHRIDIA OF THE POLYOHATA. 743

4, Cunnineuam, J. T.—‘‘Some Points in the Anatomy of Polycheta,”
‘Quart. Journ. Micr. Sci.,’ vol. xxviii, 1887.
5. Eisic, H.—‘ Die Capitelliden des Golfes von Neapel,” ‘ Fauna und
Flora von Neapel,’ vol. xvi, 1887.
. Enters, E.—‘ Die Borstenwurmer,’ Leipzig, 1864—68.
. Fraivont, J.—‘ Le genre Polygordius,” ‘ Fauna und Flora des Golfes
von Neapel,’ vol. xxiv, 1887.
8. Goopricu, EH. 8.—** On a New Organ in the Lycoridea,” ‘ Quart. Journ.
Mier. Sci.,’ vol. xxxiv, 1893.
9. Goopricn, H. S.—* Notes on Oligochetes,” ‘ Quart. Journ. Mier. Sci.,’
vol. xxxix, 1896.
10. Goopricu, HE. §8.—‘On the Colom, Genital Ducts, and Nephridia,”
‘Quart. Journ. Micr. Sci.,’ vol. xxxvii, 1895.
11. Goopricu, H. $.—“ On the Nephridia of the Polycheta,” Part I, ‘ Quart.
Journ. Micr. Sci.,’ vol. xl, 1897.
12. Goopricu, H. 8.—‘On the Nephridia of the Polycheta,” Part II,
‘Quart. Journ. Micr. Sci.,’ vol. xli, 1898.
13. GravieR, Cu.—“ Recherches sur les Phyllodociens,” ‘ Bull. Sci. France
et Belgique,’ vol. xxix, 1896.
14. Greerr, R.—‘ Untersuchungen iiber die Alciopiden,”’ ‘Nova Acta d.
kais. Leop. Car. Ak.,’ vol. xxxix, 1877.
15. Greerr, R.—‘‘ Ueber die Pelagische Fauna an den Kiisten der Guinea-
Inseln,” ‘ Zeit. f. Wiss. Zool.,’ vol. xlii, 1885.
16. HarscueK, E.— Studien tber Entwickelungsgeschichte der Anneliden,”’
‘ Arb. Zool. Inst. Wien.,’ vol. i, 1878.
17. Hatscurex, B.—‘ Lehrbuch der Zoologie,’ Jena, 1888.
18. Herine, E.—“ De Alcioparum partibus genitalibus organisque excre-
toriis,” ‘Dis. inaug. Lips.,’ 1860.
19. Herine, H.—“< Zur Kenntniss der Alciopiden von Messina,”’ ‘ Sitz. Ak.
Wiss. Wien,’ 1892.
20. McIntosu, W. C.—“‘ Contribution to our Knowledge of the Annelida,”
‘Quart. Journ. Micr. Sci.,’ vol. 36, 1894.
21. Mataquin, A.—“ Recherches sur les Syllidiens,” ‘ Mém. Soc. Sci. et Arts
de Lille,’ 1893.
22. Meyer, Ep.—‘‘Studien tiber der Kérperbau der Anneliden,” ‘ Mitth.
Zool. Sta. Neapel,’ vol. vii, 1887.
23. Satnt JosrrH, Lz Baron pr.— Les Annélides Polychétes des Cotes
de Dinard,” ‘ Ann. Sci. natur. Zool.,’ 7€ série, vol. i, 1886.
24. Stewart, F. A—“On the Nephridium of Nephthys cxca, Fabr.,”
‘Ann. and Mag. Nat. Hist.,’ vol. v, 1900.

I

744, EDWIN 8S. GOODRICH.

25. Trautzscu, H.— Beitrag zur Kenntniss der Polynoiden,” ‘ Jen. Zeit. f.
Naturw.,’ vol. xxiv, 1889, 1890.

26. Vuspovsky, F.—‘ Monographie der Enchytreiden,’ Prag., 1879.

TABLE oF Contents oF Parts I, IJ, ann III.

PAGE
Part I, this Journal, vol. 40, n. s., April, 1897.

Hesione: The Ciliated Organ : : ‘ : . | 185
The Nephridium : : : : 3 . wer
Tyrrhena . : : : : : : «/ +188
Nephthys: The Ciliated Organ. : : . 188
The Nephridium ‘ : : é : . 190

Part II, this Journal, vol. 41, n. s., November, 1898.
Glycera: . : : : : : . 440
The INepiiriefnina : ; : : . . 441
The Ciliated Organ. é : . 3 . 445
The Nephridial Sac. 44.6

On the Functions of the Ciliated Organ Neplisidial See. aitd
Nephridium, and on the Celomic Fluid of the Glyceride 447

Goniada: The Nephridium : ; ‘ é . 452
The Ciliated Organ. : , ‘ ; . 453
Part III.
Phyllodocidee : : ; : : : « 699
Alciopine : The Nepean : - ‘ : . 700
The Genital Funnel . : : : : a f0L
Phyllodocine: The Nephridium . : - : ove
The Genital Funnel . : : 3 : a OF
Syllide . : s ; : : =. 708
Amphinomide : ‘ : - +- Wi8
Further Observations on the Hésionides ; ‘ : . 718
Further Observations on the Nephthyride : = le
Polygordiidee : ; : - : . 715
The Adult Neghriavam . : : < = 716
The Larval Nephridium : 716

Summary of the most Important Facts desorbed” in Parts 1 IL,
and III ; : : ; : : Seale

THE NEPHRIDIA OF THE POLYCHATA. 745

PAGE
General Conclusions :
The Genital Funnel. : 724
The Connection between the Nephridinin ad the Genital
Funnel . : ‘ ; F J dios
The Nephridium ‘ : ; ; : . 734
The Solenocytes 5 . . 736
The Importance of the Meohetdain { in (Claceifeation : . 739
Proposed Nomenclature, : : : A . 741

EXPLANATION OF PLATES 37—42,

Illustrating Mr. Hdwin 8. Goodrich’s paper on “The Nephri-
dia of the Polycheeta.”

PLATE 37.

Fie. 1.—Enlarged view of the right side of a median segment of an imma-
ture female Vanadis formosa, showing the genital funuel and the nephiri-
dium by transparency. From the living.

Fic. 2.—Portion of a section through two branches of the nephridium of
Alciope cantrainil, showing the nuclei of the solenocytes. Cam. oil im.
qs) 0¢. 3.

Fic. 3.—Enlarged view of the extremity of the nephridium of Alciope
cantrainii. Only two branches are represented. From the living.

Fie. 4.—Arrangement of the tubes of the solenocytes in short rows, between
which the outer cilia can work.

Fic. 5.—Enlarged view of the terminal enlargement and external pore of
the nephridial canal of Alciope cantrainii. From the living.

Fie. 6.—Enlarged view of the inner end of the nephridium, and the rudi-
mentary genital funnel in a young Alciope krohnii; 11th segment.

Fic. 7.—Similar drawing of these structures in the 17th segment of the
same worm,

Fie. 8.—Longitudinal section of Alciope cantrainii, ripe male, showing
the genital funnels and nephridial canals filled with spermatozoa. Cam.

PLATE 38.

Fic. 9.—Enlarged view of a small portion of the nephridial canal, with its
solenocytes, drawn from a living Asterope candida. Cam. Oil. im.

eh
oc, 6.

746 EDWIN §S. GOODRICH.

Fies. 10, 11, and 12.—Three sections of the nephridium of Eteone
siphonodonta. Fig. 10 from a transverse section, and fig. 11 from a longi-
tudinal, show the subdivision of the lumen into primary and secondary canals.
Fig. 12, from a longitudinal section, shows the rudimentary genital funnel.
Cam. D, oc. 3.

Fie. 13.—Enlarged view of a portion of the inner end of the nephridium of
Phyllodoce laminosa.

Fie. 14.—Inner branched end of the nephridium of Phyllodoce
paretti. Cam. D, oc. 3.

Fies. 15, 16, and 17.—Three transverse sections, from behind forwards, of
the nephridial duct and genital funnel of an immature Eulalia punctifera,
Cam. D, oc. 3.

PLATE 39.

Fie. 18.—Longitudinal vertical (sagittal) section through three segments of
a ripe male, Hteone lactea, showing the genital funnels opening into the
nephridial ducts. Cam.

(In this and the next two figures the spermatozoa are not represented.)

Fic. 19.—Similar section through a ripe male Irma latifrons. Cam, A,
oc. 3.

Fie. 20.—Similar section through a ripe male Pionosyllis, sp. Cam. A, oe. 3.

Fig. 21.—Similar section through an immature Eunice sanguinea.

Fic. 22.—Longitudinal horizontal (frontal) section through Ophiodromus
flexuosus, immature female. The ova are shown in one segment only. Cam.
L. 4, oc. 3.

PLATE 40.

Fries. 23 and 24.—Longitudinal vertical sections through a ripe male
Eulalia punctifera; from sections lent by M. Gravier. Solenocytes are
seen in the second figure only. Cam. A, oc. 3.

Fies. 25 and 26.—Two longitudinal sections through the junction of the
same genital funnel with the nephridium in a segment of an immature female
Ophiodromus flexuosus. Cam. D, oe. 4c.

Fic. 27.—Half a transverse section of an immature male Eulalia
punctifera (cf. Figs. 23 and 24) showing the nephridia, and developing
genital funnel. The lower nephridium is cut through near its external
aperture, the upper one near its anterior blind extremity. Cam. AA, oc. 2.

Fic. 28.—Longitudinal section through the junction of the genital funnel
and the nephridial duct in an immature male Eulalia punctifera (the same
specimen is represented in Fig. 27). Unripe spermatozoa are seen in the

THE NEPHRIDIA OF THE POLYCHATA. 747

genital funnel. There is as yet no direct communication between the cavities
of the two organs. Cam. oil im. 54, oe. ¢.

Fic. 29.—Similar section through the junction of the nephridium and the
genital funnel in a ripe male Eteone lactea (from which specimen fig. 18
has already been given). The communication is established, and ripe
spermatozoa can be seen further down the nephridial duct. Cam. oil im. 34,
Oc. 4c.

Fie. 30.—Similar section through the junction of the genital funnel and
nephridium in Pionosyllis sp. (same series as Fig. 20). The actual opening
of the one into the other is not cut through. Cam. oil im. +4, oe. 3.

PLATE 41.

Fic. 31.—Two halves of transverse sections through a segment of Noto-
mastus latericeus, showing the genital funnels. An asterisk marks the
level of the genital pore. On the left hand side the backward prolongation
of the lip of the funnel is seen; but it does not reach the nephridium.

Fig. 32.—Similar sections farther back, showing the nephridium. The
level of the nephridiopore is marked by an asterisk.

Fie. 33.—Portion of a longitudinal vertical section of a Nephthys ceca,
into the ccelom of which some Indian ink has been injected. The nephridium
and genital funnel (ciliated organ) are cut through, and the latter is seen to
dip into a sac in which are accumulated numbers of amcebocytes loaded with
the insoluble black granules. Cam. D, oc. 2.

Fic. 34.—Optical section of the nephridium from an anterior segment of a
young Trypanosyllis. From the living. Oil im. +4, oc. 3.

Fic. 35.—Portion of a longitudinal section of a young Syllis vivipara
(median segment) passing through the nephridial funnel. Cam. Oil im. 34,
oc. 4 ¢.

Fic. 36.—Optical section of the nephridium of a posterior segment of a
mature Syllis vivipara. From the living. Oil im. 74, oc. 6 ¢.

Fie. 37.—Portion of a longitudinal section of a segment of the non-repro-
ductive region of Haplosyllis spongicola passing through the nephridial
funnel. Cam. Oil im. 54, oc. 4c.

Fic. 38.—Transverse section (somewhat oblique) through a median segment
of a ripe male, Pionosyllis sp. As in fig. 20, the spermatozoa are omitted. The
genital funnel shows on the left, and the nephridial duct on the right. Cam.
A, oc. 3.

Fic. 39.— Portion of a transverse section of a non-productive segment of
Haplosyllis spongicola, showing the lower lip of the nephrostome, and
the upper lip (= rudimentary genital funnel ?), Cam, Oil im. 74, oc. 4e.

748 EDWIN 8. GOODRICH.

PLATE 42.

Fic. 40.—Portion of a longitudinal vertical section through a median
segment of Kuphrosyne foliosa, showing the nephridium, partly indicated
by dotted lines. Cam. D, oe. 2.

Fie. 41.—Enlarged view of the nephrostome of Praxithea (Nereis)
irrorata. From the living.

Fie. 42.—Enlarged view of the nephrostome of Nereis longissima,
From the living.

Fre. 43.—Some of the ciliated processes of the same nephrostome.

Fie. 44.—Enlarged view of the nephrostome of Lipephile (Nereis)
cultrifera. From the living.

Fie. 45.—Some of the ciliated lobes of the same nephrostome, with the
nuclei stained.

Fie. 46.—Enlarged view of the anterior portion of the nephridium of a
female Polygordius neapolitanus, in optical section.

Fic. 47.—Portion of transverse section of an immature Polygordius
neapolitanus, showing the nephridium. Cam. D, oc. 3.

Fic. 48.—Semidiagrammatic reconstruction of the extremity of one of the
branches of the ‘ head-kidney”’ of a larval Polygordius sp., showing the
solenocytes. The exact relative position of the tubes and the web is still
uncertain (see page 716).

Fre. 49.—Enlarged view of the nephrostome of a larval Arenicola (page 729).

Fic. 50.—Reconstruction of the fused genital funnel and nephridial duct in
a mature Irma latifrons, seen from in front.

Fic. 51.—Reconstruction of the fused genital funnel and nephridium of a
mature Aleiope cantrainii, seen from the side.

NOUVELLES OBSERVATIONS SUR LES PERIPATUS. 749

Nouvelles Observations sur les Peripatus de la
Collection du Musée Britannique.

Par

E. L. Bouvier,
Professeur au Muséum d’Histoire Naturelle de Paris.

M. te Proresseur Ray LanKester ayant eu l’aimable obli-
geance de me communiquer ce qui restait d’?Onychophores au
British Museum aprés son premier envoi, j’ai pensé qu'il
serait utile de faire connaitre les observations que ces ma-
tériaux complémentaires m’ont permis d’effectuer.

La présente note est donc la suite naturelle du court
travail que j’ai publié, il y a quelques mois, sur la premiére
partie de la collection de Péripates andicoles.

Dans le deuxiéme envoi, les Péripates andicoles étaient
représentés par un second exemplaire femelle de Peripatus
Lankesteri Bouv.. Ce spécimen différe du premier par
ses appendices ambulatoires plus nombreux (38 paires au lieu
de 37), et surtout par sa taille remarquablement grande: la
femelle type mesurait 35 mill. sur 5, tandis que celle qui
nous occupe n’a pas moins de 82 mill. de longueur sur 9 de
largeur maximum. Malgré tout, les caractéres de cette
femelle sont exactement ceux qui appartiennent au type, les
seules différences appréciables étant la coloration uniformé-
ment noirdtre de toutes les papilles, la présence de deux
petites dents a la base des griffes maxillaires, et le développe-
ment de papilles accessoires qui viennent, surtout dans les
grands plis, s’intercaler trés régulicérement parmi les papilles
principales.

Cet exemplaire m’a permis de constater que la taille des

1H. L. Bouvier, “ Observations sur les Onychophores de la collection du
Musée Britannique,”’ ‘Quart. Journ. Mier. Sci.,’ vol. xliii, p. 367, 1900,

you. 43, PART 4,—NEW SERIES. FERRE

750 E. Le BOUVIER.

jeunes augmente avec les dimensions de la femelle qui les
porte. Dans la branche utérine droite se trouvait, en effet,
un embryon mir qui avait 32 mill. de longueur et 3 mill. de
largeur maximum; ainsi cet embryon était presque aussi
grand que la femelle adulte du premier envoi, d’ou Pon peut
conclure que cette derniére donnait sirement des jeunes bien
plus petits.

Dans cet embryon les petits plis tégumentaires sont rela-
tivement plus réduits que ceux de ladulte et dépourvus de
grandes papilles principales, les papilles accessoires ne sont
pas encore apparentes, mais les papilles principales sont déja
nettement différenciées en deux sortes, les grandes et les
petites. Sur le bord postérieur de Vorifice buccal s’observe
trés nettement la plaque cornée et cordiforme qu’on observe,
en cet endroit, dans tous les embryons avancés du groupe.

On sait que les Onychophores présentent, bien avant la
naissance, le nombre complet de leurs appendices. L’em-
bryon qui nous occupe avait 35 paires de pattes et présen-
tait des papilles sexuelles sur les deux paires prégénitales au
moins; c’était, par conséquent, un male, et nous voila dés lors
fixés sur les caractéres essentiels que présentent les deux
sexes dans cette intéressante espéce.

J’ajoute, pour terminer, que la seconde femelle avait été
capturée, comme la premiére, par M. Rosenberg, a Pa-
ramba, c’est-a-dire 4 70 milles environ au N. de Quito.

Péripates caraibes.—Pour la commodité de cette étude,
je diviserai les Péripates caraibes en trois groupes; ceux qui
ont pour type le P. jamaicensis Gr. et Cook, ceux qui se
groupent naturellement autour du P. juliformis Guild,
enfin les espéces fort nombreuses qui se rattachent plus ou
moins directement au P. Edwardsi Blanch..

1. Groupe du P. jamaicensis.—Ce groupe est carac-
térisé par de trés nombreuses paires de pattes (40 environ),
par Virrégularité des plis tégumentaires, et par luniformité
des papilles, qui sont petites et trés serrées. I] ne comprend
qu’une seule espéce dont je renvoie l'étude 4 la fin de cette
note.

NOUVELLES OBSERVATIONS SUR LES PERIPATUS. dol

2. Groupe du P. juliformis.—bLes femelles de ce
groupe ont presque toujours de 30 a 34 paires de pattes, et
les males des papilles sexuelles sur les trois paires prégéni-
tales pour le moins; on en trouve parfois sur les 8 paires
prégénitales dans le P. Sedgwicki Bouv., il y en a tou-
jours moins dans le P. juliformis et dans une autre espéce
qui appartient au méme groupe, le P. Brolemanni Bouv..
Toutes ces espéces sont caractérisées par des papilles prin-
cipales de deux sortes, des petites et des grandes, les pre-
miéres s’intercalant entre les secondes, et étant accom-
pagnées de papilles accessoires qui comblent, trés impar-
faitement, Vespece compris entre deux grandes papilles
principales consécutives.

Dans le matériel que m’a communiqué le Musée Britannique,
ce groupe n’est représenté que par le P. juliformis et par
ses variétés; toutes ces formes ont pour caractére commun
une différentiation trés nette des papilles principales grandes
et petites et une réduction extréme des papilles accessoires.

Dans les exemplaires qui appartiennent a lespeéce typique
(P. juliformis Guild.) les petites papilles principales sont
médiocres et accompagnées de papilles accessoires fort éviden-
tes; dans ceux qui représentent des variétés de lespéce, les
petites papilles principales sont relativement grandes, tandis
que les papilles accessoires sont, presque partout, rudimentaires.
Je range dans la variété danicus Bouv. ceux dont les grandes
papilles principales sont peu nombreuses et irréguliérement
disposées, et je propose le nom de var. Gossei pour ceux
dont les grandes papilles principales sont peu abondantes et
assez nettement disposées en lignes longitudinales ondulées.

L’espéce typique se trouve a 8. ‘Thomas (Mus. de Copen-
hague) et aS. Vincent; ses exemplaires femelles ont de 32
a 34 paires de pattes; les males en ont 29 ou 30, et présentent
une paire de tubercules sexuels sur trois ou quatre paires
de pattes prégénitales.

La variété danicus parait jusqwici propre a 8. Thomas;
un male de la collection du Musée Britannique a 28 paires de
pattes, et présente une paire de tubercules sexuels sur cha-

752 EK. L. BOUVIER.

cune des quatre paires de pattes prégénitales ; une femelle
du Musée de Copenhague a 33 paires de pattes; une autre,
douteuse et en mauvais état, n’en a que 382.

La variété Gossei est représentée, dans la collection du
Musée Britannique, par deux exemplaires femelles qui ont 31
paires de pattes. Ces exemplaires avaient été considérés par
M. Pocock comme des P. jamaicensis; ils ont été recueillis
par Gosse, a la Jamaique.

3. Groupe du P. Hdwardsi.—Les nombreuses espéces
de ce groupe ont un nombre de pattes plus restreint (30 en
moyenne chez les femelles, et parfois sensiblement moins)
que les précédentes; les papilles principales y sont le plus
souvent subégales, mais beaucoup d’espéces en présentent
des grandes et des petites; quant aux papilles accessoires,
tantot elles sont trés nombreuses et bien développées, ce
qui est le cas le plus fréquent, tantdt elles sont trés réduites
ou manquent méme a peu pres complétement dans la région
médiane du dos (P. Ohausi Bouy.). Dans toutes les espéces
dont les males sont connus, on ne trouve de papilles
sexuelles que sur les deux paires de pattes prégénitales.

Pour le lot que j’étudie, les espéces de ce groupe sont le
P. dominice Pollard, le P. trinidadensis Sedgw., le P.
Simoni Bouy., et le P. brasiliensis Bouv..

Le P. dominice ressemble au P. juliformis par ses
papilles principales qui sont de deux sortes bien tranchées,
mais ses papilles accessoires sont fortes, nombreuses, et
remplissent complétement l’espace compris entre les papilles
plus grandes. Les males que j’ai eus entre les mains pro-
venaient d’Oxford, et avaient 25 paires des pattes; les
femelles en comptaient 29 ou 30 paires; dans une femelle du
Musée de Copenhague le nombre des pattes s’élevait a 31
paires. L’une des femelles du Musée Britannique est le
type de ’1Hunara Shawiana de Leach; l’étiquette, écrite
de la main de cet auteur, est libellée de la maniére suivante :
“Nereis pedata, Hunara Shawiana mihi.” Les
maxilles des embryons murs sont dépourvues de denticules
et de scie, mais il suffira d’une mue pour faire apparai-

NOUVELLES OBSERVATIONS SUR LES PERIPATUS. 750

tre ces formations, qui se voient déja sous la chitine
superficielle.

Le P. trinidadensis se fait remarquer par l’abondance
et la disposition irréguliére de ses papilles accessoires, qui
passent par tous les degrés aux papilles principales; ces
derniéres se différencient parfois, surtout chez les petits
exemplaires, en grandes papilles’ blanchatres et en petites
papilles de couleur plus foncée, mais la différence de taille
entre ces deux sortes de papilles est infiniment moins
tranchée que dans le P. dominicze. Cette espéce est propre
ala Trinité, tandis que la précédente n’est connue qu’a la
Dominique. Les nombreuses femelles de la collection du
Musée Britannique ont de 29 a 31 paires de pattes; les males
en ont 28.

Le P. Simoni ressemble au P. Edwardsi par ses papilles
principales subégales et par ses papilles accessoires assez
nombreuses, mais ses papilles principales sont basses et
franchement coniques, ses pattes sont tres largement séparées,
son corps est long et gréle, et sa coloration d’un rouge
brunatre uniforme. On ne connait pas les males de cette
espéce. Les trois femelles (du Musée Britannique) furent
capturées 4 Beeves, sur Amazone; tandis que les deux du
premier envoi avaient l’une 29, autre 31 paires de pattes,
celle du second n’en comptait pas plus de 28 paires.

Les P. brasiliensis compris dans le second envoi pro-
viennent de Santarem comme ceux du premier; ils sont
représentés par deux femelles munies de 31 paires de pattes,
par une autre femelle plus petite qui en a 32 paires, et par
un male adulte qui a 29 paires de pattes. Cet exemplaire
présente deux papilles sexuelles sur chacune des pattes des
deux paires prégénitales ; c’est, jusqu’ici, le seul male qui soit
connu dans cette espéce ; comme les femelles, il se distingue
par ’absence complete de toute bifurcation segmentaire dans
les plis dorsaux. C’est la, d’ailleurs, le caractére fonda-
mental de cette espéce, celui qui la distingue absolument de
toutes les autres espéces des genre Peripatus.

Observations sur les Péripates de la Jamaique.—

754 E. L. BOUVIER.

Les Péripates ont été découverts a la Jamaique par Gosse,
qui en captura trois exemplaires actuellement conservés dans
les collections de Musée Britannique. Hn 1892 (‘ Nature,
vol. xlvi, p. 514) d’autres individus furent signalés par MM.
Grabham et Cockerell, et briévement décrites sous le nom de
P. jamaicensis. Depuis M. Grabham (‘Journ. Inst.
Jamaica,’ vol. i, pp. 217—220, 1893) est revenu sur cette
espéce, qui aurait, d’aprés lui, de 29 a 43 paires de pattes ;
plus récemment (‘ Zool. Anz.,’ vol. xvi, pp. 341—3438, 1893)
M. Cockerell a signalé deux ‘‘mutations” du P. jamai-
censis, Vune de couleur homogéne noiratre (mutation
Swainsone), lautre avec des papilles blanches éparses et
le bout des antennes blanc (mutation Gossei); lun des in-
dividus de la mutation Swainson avait 29 paires de
pattes, et Pun de ceux de la mutation Gossei 36 paires.
En 1894 M. Pocock (‘Ann. of Nat. Hist.,’ t. xxiv, p. 524)
a décrit sous le nom de P. jamaicensis les exemplaires
capturés par Gosse, et comme deux de ces exemplaires sont
des femelles ayant 31 paires de pattes, tandis que l’autre est
un mile de 37 paires, il conclut que les males de P. jamai-
censis, contrairement a ce que l’on observe dans les autres
Péripates américains, ont plus de pattes que les femelles.

Toutes ces observations sont discordantes et peu en rapport
avec ce que Von sait de lorganisation des Peripatus; dans
aucune espéce du groupe, on ne voit le nombre des pattes
varier dans une aussi large mesure (de 29 a 43 paires), dans
aucune surtout on ne voit les males posséder plus de pattes
que les femelles. Aussi dois-je remercier bien vivement M. le
Professeur Ray Lankester qui, en me permettant d’étudier
les Péripates du British Museum, m’a donné la possibilité de
jeter quelque lumiére sur cette intéressante question.

Les exemplaires capturés par Gosse appartiennent en
réalité & deux espéces différentes; une qui a de nombreuses
paires de pattes et & laquelle je conserve le nom de P.
jamaicensis, l’autre qui a des pattes moins nombreuses et
que j’ai désignée plus haut sous le nom de P. juliformis
var. Gossel.

NOUVELLES OBSERVATIONS SUR LES PERIPATUS. 755

1. P. jamaicensis.—L’exemplaire 4 37 paires de pattes
recueilli par Gosse appartient a cette espéce ; comme Ll avait
observé M. Pocock, c’est un mile muni de papilles sexuelles
sur les deux paires de pattes prégénitales. Outre cet exem-
plaire, j’ai pu étudier une femelle 4 40 paires de pattes de la
collection du British Museum (femelle qui renfermait un
embryon mir 4 41 paires) et deux exemplaires de méme sexe
que m’a gracieusement donnés M. Sedgwick, de Cambridge.
Ces deux exemplaires provenaient directement de MM.
Grabham et Cockerell; ils avaient 39 ou 40 paires de pattes,
et ’un d’eux renfermait des embryons miirs ayant 40 paires
de pattes.

De ces observations il semble déja qu’il est possible de
conclure que les spécimens a pattes nombreuses forment une
espéce particuliére, et qwils n’ont aucune relation avec ceux
dont le nombre des pattes descend aux environs d’une tren-
taine. Hn fait, ces exemplaires présentent tous des caractéres
spéciaux et ne ressemblent 4 rien aux autres Peripatus
d’Amérique. Leurs plis sont couverts de petites papilles ordi-
nairement unisériées, et séparés par des plis plus réduits ot se
trouvent des papilles beaucoup plus petites. Les plis 4 grandes
papilles sont assez réguliers, sauf sur les flanes, ot ils ont une
tendance a se confondre; mais les plis a petites papilles
sont bien plus irréguliers et se fusionnent par intervalles
avec les principaux. J’ajouterai que, dans mes spécimens,
la papille urinaire anormale des pattes IV et V se continue en
dessus avec le 3°arceau des soles pédieuses, et que le nombre
des grands anneaux des antennes ne parait pas s’élever a
40, tandis qu’il est de 45 environ dans les autres espéces
américaines.

D’ailleurs, par leur coloration et la taille de leurs papilles,
ces exemplaires peuvent se rattacher & deux types: lun
dont la couleur foncée est absolument uniforme, jusqu’au
bout des antennes, et qui parait correspondre a4 la mutation
Swainsone de M. Cockerell; Vautre qui a des papilles
blanches éparses un peu plus grosses et le bout des antennes
blanc; ce dernier appartient certainement a la mutation

756 E. L. BOUVIER.

Gossei. L’embryon extrait de la femelle de ce type
ressemble absolument 4 la mére.

2. P. juliformis var. Gossei.—Les deux autres exem-
plaires recueillis par Gosse sont partout, méme au bout des
antennes, d’une teinte uniforme d’un brun jaunitre ; il est
maniteste d’ailleurs qu’ils ont subi une forte décoloration.
Dans un exemplaire de la méme variété recueilli par M.
Swainson, la couleur est d’un brun violacé avec une teinte
un peu plus claire a l’extrémité des antennes. Tous ces
exemplaires sont des femelles ; les deux premiers ont 31 paires
de pattes, le dernier en a 33 paires.

Par le nombre de leurs appendices, ces exemplaires rap-
pellent en conséquence le P. juliformis Guild.; ils se rap-
prochent également de cette espéce par la disposition de
leurs papilles principales, qui sont de deux sortes: les unes
grandes et de teinte plus claire, les autres plus réduites et
intercalées dans chaque pli entre les précédentes. D/ailleurs
les plis sont fort réguliers et ne sont pas séparés, comme
dans l’espéce précédente, par des rangées de petites papilles.
Tl est probable que les males de cette forme ont des papilles
sexuelles sur les quatre paires de pattes prégénitales, comme
les P. juliformis typiques.

La forme qui nous occupe se distingue d’ailleurs de ces
derniers par ses papilles principales intercalaires, qui sont
bien plus grandes, bien plus serrées, et qui sont rarement
accompagnées de papilles accessoires. Dans plusieurs ex-
emplaires les grandes papilles principales forment des lignes
longitudinales sinueuses, qui rappellent jusqu’a un certain
point la mutation Gossei du P.jamaicensis. Je propose
pour cette forme de la Jamaique le nom de P. juliformis
var. Gossel.

3. Conclusion.—De ce qui précéde on peut conclure:
(1) que les Péripates décrits jusqu’ici sous le nom de P.
jamaicensis appartiennent en réalité 4 deux espéces fort
différentes, une qui mérite de conserver le nom de P.
jamaicensis, l’autre qui est une variété du P. juli-
formis; (2) que la premiére de ces espéces a de 36 a 45

NOUVELLES OBSERVATIONS SUR LES PERIPATUS. 797

paires de pattes, et qu’elle se présente sous deux formes
différentes, ’une de teinte sombre uniforme (mut. Swain-
sone), Vautre piquetée de blanc et remarquable par la
teinte blanche que présente l’extrémité des antennes (mut.
Gossei) ; (3) que la seconde a des pattes moins nombreuses
(31 a 33 paires chez les femelles, moins certainement chez les
males), et qu’elle rappelle par la disposition de ses papilles le
P. juliformis.

Je suis persuadé que ’exemplaire a 29 paires de pattes,
attribué par M. Cockerell a la mutation Swainsone, est un
male de P. juliformis var. Gossei; et que l’exemplaire a
36 paires de pattes de la mutation Gossei est un male
ailleurs réguliérement dénommé. II serait a désirer que
Padministration de l'Institut de la Jamaique voulut bien me
communiquer les exemplaires types qu’elle posséde, afin de
régler définitivement ces diverses questions.

J’ajouterai que le spécimen de la Dominique remis au
British Museum par M. G. F. Angas est un P. dominice
des plus typiques, et non point, comme le croyait M. Pocock,
un P. jamaicensis.

VoL. 43, PART 4.—NEW SERIES. GiGaG

NED ee Os V Ole Are;

NEW SERIES.

Amphioxus, development of, by Mac-
Bride, 351

Apteryx, tapeworms of, by Benham,
83

Arenicolide, anatomy and classifica-
tion of, by Gamble and Ashworth,
4.19

Ashworth and Gamble on the anatomy

and classification of the Areni- |

colide, 419

Benham on two new tapeworms from
Apteryx, 83

Bernard, retina of frog, 23

Bouvier, quelques observations sur
les Onychophores (Peripatus), 367
and 749

Cerebratulus, early development of,
by C. B. Wilson, 97

Crotaline, sensory pit of, by G. 8.
West, 49

Daphnia magna, its reaction to en-
vironment, by Ernest Warren, 199

Diplochorda, on the, by Masterman,
375

Fielding-Ould and Ross on the para-
sites of malaria, 571

Frog, retina of, by H. M. Bernard, 238

Gamble and Ashworth on the anatomy
and classification of the Areni-
colide, 419

Gamble and Keeble on the colour-
changes of Hippolyte varians,
589

Goodrich on the nephridia of the
Polycheta, part ii, 699

Hemameebide, by H. Ray Lankester,
581

Harmer, revision of the genus Ste-
ganoporella, 225

Haswell on a new Histriobdellid, 299

Hill on embryology of Marsupialia, 1

Hippolyte varians,colour-changes
of, by Gamble and Keeble, 589

Histriobdellids, a new genus of, by
Haswell, 299

Jenkinson, early stages of mouse, 61
Keeble and Gamble on the colour-
changes of Hippolyte varians,

589

Lankester, E. Ray, on the Hemame-
bide, 58]

760

MacBride on the development of
Amphioxus, 351

MacMunn on spongioporphyrin, the
pigment of Suberites Wilsoni,
337

Malaria, parasites of, by Ross and
Fielding-Ould, 571

Marsupialia, embryology of, by J. P.
Hill, 1

Masterman on the Diplochorda, the
anatomy and development
Phoronis Buskii, 375

Mouse, early stages of, by Jenkinson,
61

of

Nephridia of the Polycheta, by
Goodrich, part ui, 699

Peripatus, quelques observations sur
les Onychophores, par M. le Pro-
fesseur Bouvier, 367 and 749

Phoronis Buskii, development and
anatomy of, by Masterman, 375

PRINTED BY

i

ADLARD AND

INDEX.

Polycheta, the nephridia of, part iii,
by Goodrich, 699

Retina of frog, by H. M. Bernard, 23
Ross and Fielding-Ould on the para-
sites of malaria, 571

Spongioporphyrin, the pigment of
Suberites Wilsoni, by Mac-
Munn, 337

Steganoporella, revision of the genus,
by Harmer, 225

Suberites Wilsoni, the pigment
of, by MacMunn, 337

Tapeworms from Apteryx, by Ben-
ham, 83

Warren on the reaction of Daphnia
to its environment, 199

West on the sensory pit of the Cro-
talinee, 49

Wilson, C. B., on the early stages of
Cerebratulus, 97

SON,

BARTHOLOMEW CLOSE, E.C., AND 20 HANOVER SQUARE, W.

With Ten Plates, Royal 4to, 5s.
CONTRIBUTIONS TO THE KNOWLEDGE OF RHABDOPLEURA
AND AMPHIOXUS.
By E. RAY LANKESTER, M.A., LL.D., F.R.S
London: J. & A. CHURCHILL, 7, Great oY Sage ‘Streak,

Science.

The SUBSCRIPTION is £2 for the Volume of Four Numbers;
for this sum (prepaid) the JouRNAL is sent Post Free to any part
of the world.

BACK NUMBERS of the Journat, which remain in print, are
now sold at an uniform price of 10/-.

The issue of SuppLemMentT NUMBERS being found inconvenient,
and there being often in the Editor’s hands an accumulation of
valuable material, it has been decided to publish this Journal at
such intervals as may seem desirable, rather than delay the appear-
ance of Memoirs for a regular quarterly publication.

The title remains unaltered, though more than Four Numbers
may be published in the course of a year.

Each Number is sold at 10/-, and Four Numbers make up a
Volume.

London: : & A. CHURCHILL, 7 Great Marlborough Street.

TO CORRESPONDENTS.

Authors of original papers published in the Quarterly Journal
of Microscopical Science receive twenty-five copies of their
communication gratis.

All expenses of publication and illustration are paid by the
publishers.

As a rule lithographic plates, and not woodcuts, are used in
illustration.

Drawings for woodcuts should nor be inserted in the MS.,
but sent in a separate envelope to the Editor.

Contributors to this Journal requiring ewtra copies of their
communications at their own expense can have them by applying
to the Printers,

Messrs. ApLarD & Son, 224, Bartholomew Close, E.C., on
the following terms :

For every four pages or less—

25 copies 3 . . : d/-
aOF 55 ; : : : 6/-
1O0r 3 : 7/-

Plates, 2/- per 25 if uncoloured ; if coloured, at the same rate for
every colour.
Prepayment by P.O. Order is requested.
ALL CoMMUNICATIONS FOR THE EDITORS TO BE ADDRESSED TO THE CARE
or Messrs. J. & A. Cuurcuitt, 7, Great Mariporoueu Srresr,
Lonpon, W.

AG
fe

THE MARINE BIOLOGICAL ASSOCIATION

OF THE
UNITED KINGDOM.

Patron—H.R.H. the PRINCE OF WALES, K.G., F.R.S.
President—Prof. E. RAY LANKESTER, LL.D., F.R.S.

:0:

THE ASSOCIATION WAS FOUNDED “ TO ESTABLISH AND MAINTAIN LABORATORIES ON
THE COAST OF THE UNITED KINGDOM, WHERE ACCURATE RESEARCHES MAY BE CARRIED
ON, LEADING TO THE IMPROVEMENT OF ZOOLOGICAL AND BOTANICAL SCIENCE, AND TO
AN INCREASE OF OUR KNOWLEDGE AS REGARDS THE FOOD, LIFE CONDITIONS, AND HABITS
OF BRITISH FOOD-FISHES AND MOLLUSCS.”

The Laboratory at Plymouth

was opened in 1888. Since that time investigations, practical and scientific, have
been constantly pursued by naturalists appointed by the Association, as well as by
those from England and abroad who have carried on independent researches.

Naturalists desiring to work at the Laboratory

should communicate with the Director, who will supply all information as to
terms, &e.

Works published by the Association

include the following :—‘ A Treatise on the Common Sole,’ J. T. Cunningham, M.A.,
4to, 25/-. ‘The Natural History of the. Marketable Marine Fishes of the British
Islands,’ J. ‘I’. Cunningham, M.A., 7/6 net (published for the Association by
Messrs. Macmillan & Co.).

The Journal of the Marine Biological Association

is issued half-yearly, and is now in its fifth volume (price 3/6 each number).

In addition to these publications, the results of work done in the Laboratory
are recorded in the ‘ Quarterly Journal of Microscopical Science,’ and in other
scientific journals, British and foreign.

Specimens of Marine Animals and Plants,

both living and preserved, according to the best methods, are supplied to the
principal British Laboratories and Museums. Detailed price lists will be forwarded
on application.

TERMS OF MEMBERSHIP.

ANNUAL MEMBERS . : - . £1 1 Oper annum.

LiFe MEMBERS . ; ; : . 15 15 0 Composition Fee. y
FOUNDERS . 2 : ; : ~ 100.00 a be
Governors (Life Members of Council) 500 0 0 = 5

Members have the following rights and privileges:—They elect annually the
Officers and Council; they receive the Journal free by post; they are admitted to
view the Laboratory at any time, and may introduce friends with them; they have the
first claim to rent a table in the Laboratory for research, with use of tanks, boats, &c. ;
and have access to the Library at Plymouth. Special privileges ure granted to Governors,
Founders, and Life Members.

Persons desirous of becoming members, or of obtaining any information with
regard to the Association, should communicate with—

The DIRECTOR,
The Laboratory,
Plymouth.

Pa ae ' 1 ‘eau

r

a f+ :
' C4 moar, § wae) hoe
a a A eR ad.

re

CJ

ae ee ee a ee

————

| <r
_———

et) PO ACE LP at

<<

CR ian cate as

SS ee ee