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THE

RAY SOCIETY.

INSTITUTED MDCCCXLIV.

Thi# volume /.»• >**nt:<1 t<> tin: Riilmcribers to the BAY SOCIETY for

the Ywtr 1904.

LONDON:

MDCCCCV.

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THE

BRITISH TUNICATA

AN UNFINISHED MONOGRAPH

BY THE LATE

JOSHUA ALDER

AND THE LATE

ALBANY HAXCOCK, F.L.S.

EDITED BY

JOHN HOPKINSON, F.L.S. , F.G-.S., ETC.

Secretary of the Ray Society

WITH A HISTORY OF THE WORK BY THE

EEV. A. M. NORMAN, M.A., D.C.L., F.E.S., ETC.

Honorary Canon of Durham

VOLUME I

LONDON
PRINTED FOPt THE PtAY SOCIETY

1905

PRINTED BY ADLAKD AND SON
LONDON AND DORKING.

THE HISTORY OF THIS WORK.

AT a date between 1855 and 1860, Mr. Joshua Alder,
at the request of Dr. J. E. Gray, Keeper of the
Zoological Department of the British Museum, under-
took to prepare a ' Catalogue of British Tunicata.'
This Catalogue was to be published by the British
Museum as one of a series of works which included
Busk on the ' British Polyzoa,' Spence Bate on the
* Crustacea Amphipoda,' and George Johnston on
' British Nonparasitic Worms.' Alder at once gave
his whole time to the preparation of this volume. In
1863 the work was done, the whole of the descriptive
portion neatly written out and ready for the printer,
while the Plates, which gave coloured illustrations of
the then known species, together with drawings of
portions of the branchial sac of many of the forms,
were completely finished, and only required engraving.
When, however, Alder wrote to Dr. Gray to inform
him that this was the case, he received a letter in
reply which expressed the deepest regret that the
Trustees (or the Government r) had withdrawn the
grant for the publication of these Catalogues, and that
therefore, unfortunately, he was imable to avail him-
self of Alder's valuable work.*

The last of these Catalogues, that of Dr. Johnston, was not published
until 1865, but, as noted in the Preface, " the publication had been delayed
owing to the lamented death of Dr. Johnston," after which it was completed
by Dr. Baird.

VI THE HISTORY OF THIS WORK.

It now became necessary to consider what steps
should be taken to carry out the publication of Alder's
work ; and he naturally consulted his old friend and
colleague Mr. Albany Hancock. It was then agreed
between them that a more elaborate monograph should
be undertaken, in the carrying out of which Hancock
should join him and work out the Anatomy and
Physiology of the Class in a similar manner as he had
done in the joint great work on the ' Nudibranchiate
Mollusca,' and that the monograph should be offered
to the Ray Society. That Society was only too glad
to have the opportunity of procuring another work
from such authorities. Hancock, many years before,
had paid some attention to the subject, and in Alder's
" Catalogue of the Mollusca of Northumberland and
Durham ' the portion relating to the Tunicata was
under the names of Alder and Hancock.*

Hancock immediately put aside the investigations
he at that time was engaged in on the Anatomy of
the Cephalopoda, and devoted the rest of his life, so
far as health would permit, to unceasing labour on the
elucidation of the structure of the Tunicata. The
following extracts from the Minute Book of the Rav

o «/

Society, printed by permission of the Council, will
show how matters progressed, and how the extent of
the labour involved became increasingly evident.

luii/ Society — Council Meetings.

1863, Oct. 2. — Bead a letter from Mr. Alder offering a work
hy himself in conjunction with Mr. Albany Hancock on
the British Tunicata. Resolved to accept this offer.

1863, Nov. 6.— Bead a letter from Mr. Alder stating that for
the proposed work on the British Tunicata about twenty

* Joshua Alder, " A Catalogue of the Mollusca of Northumberland and
Durham " (1848), ' Trans. Tyneside Nat. Field Club,' vol. i, pp. 97-207.

THE HISTORY OF THIS WORK. Vll

plates would be required, two-thirds of which would
have to be coloured either wholly or in part, and that
the letterpress would not exceed one hundred pages
quarto.

1865, Sept, 1.— Read a letter from Mr. Alder stating that
Mr. Hancock expected to complete his investigations of
the Anatomy of the Tunicata at the end of this year,
and that they hoped that they should have the Mono-
graph ready for the press by the end of the year 1866.

1866, June 1. — Read a letter from Mr. Joshua Alder stating
that the progress of the work on the Tunicata had been
much impeded by the serious illness of Mr. Hancock,
and begging that it might not be announced as one of
the volumes for 1867.

1867, Feb. 1. — The Secretary reported the death of Mr.
Joshua Alder on the 21st of January. Resolved that
the Secretary communicate with Mr. Albany Hancock
to ascertain the degree of forwardness of the proposed
Avork on the British Tunicata.

1867, April 12. — Read a letter from Mr. Albany Hancock
stating that there yet remained very much work to be
done in connection with the proposed work on the
British Tunicata ; but that so soon as his health would
permit he should consider it a duty he owed to the
memory of his late friend to do his best to prevent the
labours of his latter years from being lost to science.

Sad for the survivor was the break in the lifelong
friendship of these two admirable naturalists, when
death called away Hancock's colleague, Joshua Alder,
on the 21st of January, 1807, in his seventy-fifth year.
Hancock was now more than ever anxious that the
monograph should be completed in the contemplated
manner, and he laboured at his investigations as
steadily as enfeebled health would permit. In the
following year lie published, as a first result of his
studies, a paper in the ' Journal of the Linnean
Society,' vol. ix, "On t/tr Anatomy and Physiology of

Vlll THE HISTORY OF THIS WORK.

the T'unicata" This paper makes known to us his
views up to that date. The proper introduction to
the present work was never written, and it is obvious
that it would have been the last thing done, so that it
might embrace the writer's final views subsequent to
the completion of his dissections of the entire class. In
the absence of such an introduction it has been deemed
advisable to reprint the paper from the Journ. Linn.
Soc. just referred to. In the autumn of 1873 Hancock
had " completed about two-thirds and a portion of the
remainder " of his work, and " was within two years of
the time when he expected to be able to bring it to a
conclusion."* But now his final sickness attacked
him, and dropsical symptoms supervening he died on
the 24th of October, 1873.

The question which the closest friends of the authors
asked themselves was, What was now to be done ?
After much consultation, but not until August, 187-5,
it was agreed that if Professor Huxley could be induced
to take up this matter, write an introduction, and
advise generally as to preparing the work for the pivss
all would be well. A meeting, therefore, was arranged.
Sir William (afterwards Lord) Armstrong invited Pro-
fessor Huxley to stay with him for two nights at
Cragside, Rothbury, and also the following naturalists
and friends of the authors to meet him : — Mr. John
Hancock (the Ornithologist, and brother of Albany),
Dr. Embleton (joint author with A. Hancock in some
of his anatomical work,t his medical adviser, and a very
close friend to the last), and the Rev. A. M. Norman.

* Dr. Embleton's " Life of Albany Hancock," ' Nat. Hist. Trans. North-
umberland and Durham/ vol. v (1874), p. 182.

t A. Hancock and Dennis Embleton, " On the Anatomy of Eolis," 'Ann.
and Mag. Nat. Hist.,' Vol. XV (1845), p. 1, pis. i-v; Ser. 2, Vol. I (1848),
p. 88, pis. iii, iv ; Ser. 2, Vol. Ill (1849), p. 183, pi. v ; and " On the Anatomy
of Doris," ' Philos. Trans.,' 1852, pp. 207-252, pis. xi— xviii.

THE HISTORY OP THIS WORK. IX

After the matter had been fully gone into, and the
MSS. and drawings had been examined, Professor
Huxley expressed his willingness to do what he could
in the matter, but said he should require some fresh
specimens of Ascidia mental// for dissection. These
Mr. Norman undertook to procure for him, and this
was done through the kind help of Mr. David Robert-
son, of Cumbrae, who went specially to Oban to obtain
the specimens, which he sent to Huxley.*

When a little more than four years had passed, the
letter here given was received from Professor Huxley
by Dr. Embleton.

" 4, MAKLBOROUGH PLACE,,

"LONDON, October 12th, 1879.

"My DEAR SIR,

" After my return from Newcastle, I forget how many
years ago, 1 examined Albany Hancock's MSS. and drawings
more carefully than I had before been able to do, and I con-
fess that the work of making a presentable volume out of
them did not appear to me to promise to be easy, but I was
quite prepared to do my best. However, shortly afterwards,
in talking over the matter with a Member of the Council of
the Ray Society, he assured me that there was not the least
chance of the Society undertaking the publication for two
years from that date, and from that and various other circum-
stances, I felt inclined to doubt whether a still longer time
might not elapse before the Society would be in a position to
undertake so expensive a work.

" Under these circumstances, 1 put the papers carefully on
one side and waited for events. But, of course, my other
occupations Avent on, and I am not at all sure that if the Ray
Society offered to publish the work at once I could give the
time (not so much for the editing and writing of the Intro-
duction, as for the supervision of the execution of the Plates)
that would be requisite.

* See ' The Naturalist of Cumbrae, being the Life of David Robertson '
(1891), by the Rev. T. E. R. Stebbiug, pp. 304-305.

X THE HISTORY OF THIS WORK.

' But it is a thousand pities that the work remains unpub-
lished,, and if anything- can be done, the MSS., so far as I am
concerned^ are absolutely at the disposal of Hancock's repre-
sentatives. I shall be obliged if you will kindly communicate
the substance of what I have said.

" With my regards to Mr. John Hancock,

" I am, yours very truly,

" T. H. HUXLEY/'

Shortly after this the MSS. and drawings were
returned. These, after the deaths of Mr. John Han-
cock and Dr. Embleton, were placed under the care of
the Committee of the Natural History Society of Efew-
castle-upon-Tyne, where they have remained until last
year, when, the work having again been accepted by
the Council of the Ray Society, they were at my
request sent for publication at last by this Society.

Though so many years have elapsed, the value of
the Monograph is great, since (1st) it contains full
descriptions with illustrations of the Tunicata of our
fauna as known up to the time of the death of the
authors ; (2nd) because many of the new species had
been only briefly diagnosed, and the fuller descrip-
tions and figures of these which are now given will
enable them to be better known and understood ; and
(3rd) it is especially desirable that the full account
of Hancock's investigations should be published
together with a portion of his beautiful drawings.

The chief difficulty from the first has been in relation
to these drawings, which are extremely numerous.
All Hancock's admirable work was effected with the
aid of such simple means as scalpels and needles.
Section-cutting and the use of chemical reagents were
in his day unknown. Our author's custom was to
gradually and most carefully dissect the animal, and to
continually make new drawings as each fresh mem-

THE HISTORY OF THIS WOEK. XI

brane or organ was removed, thus mastering every
detail, and then, aided by the numerous sketches before
him, the finished drawing was produced. Now among
the mass of drawings relating to the Tunicata, com-
paratively few have been finally perfected. These
have been here reproduced, together with such careful
selections from the rest of the drawings as seemed to
possess most value.

A large amount, of work has been undertaken by Mr.
John Hopkinson, the Secretary of the Society, in the
preparation of the Monograph for the press. With
much labour he has filled up the blanks which had
been left in the bibliographical history, and done a
great deal in the elaboration of references, and the
verification of various details. The result of some of
his work will be recognised by the circumstance that
all numbers, words, and passages which he has sup-
plied are enclosed in brackets in order to indicate that
they were not in the MSS. of the authors. In addition
to all this Mr. Hopkinson has arranged on the plates
and in the text all the drawings selected for publica-
tion, and when necessary deepened the outlines, etc.,
in order that they might come out more satisfactorily
in the photographs.

It maybe well, in conclusion, to make some remarks
on the MS. and the figures of the species. The MS.,
as received from Newcastle, was a transcript which
had been made by Mr. Joseph Wright, of the Museum
there, for more ready use by Professor Huxley. The
original MSS. would appear to have been since mislaid.
The transcript has been carefully made, and the por-
tions which had been in the handwritings of Alder and
Hancock respectively have been scrupulously indicated.
In the account of the species the diagnostic characters

Xll THE HISTORY OF THIS WORK.

with which the notice begins were in all cases up to
the time of his death written by Alder, as also for the
most part were the sentences which draw attention to
the chief distinguishing features, and affinities -with
allied species.

Most of the coloured figures of the species have been
taken from the Plates which Alder had prepared for
his Catalogue. Unfortunately there was no description
of these plates forthcoming, and the identification of a
few of the figures has been attended with some diffi-
culty. There were also later drawings by him of new
species discovered up to the time of his death ; and a
few additional illustrations of varieties have been given
from some of Alder's drawings in my possession.
These were found in the portfolios which contained all
his natural history drawings (except the Tunicata),
which were most kindly given to me by Miss Alder
after the death of her brother.

A. M. NORMAN.

BERKHAMSTED,

-J7//1 MurcJi, 1905.

NOTE ON THE ILLUSTRATIONS.

WITH the exception of figs. 5 and 6 in the text, which
have been re-drawn, all the illustrations in this volume are
photographic reproductions of original drawings by the
authors — the coloured plates and the illustrations in the text,
by the half-tone process ; the uncoloured plates (the frontis-
piece excepted), by collotype.

The Editor has ai-ranged the figures on the plates and in
the text, and has strengthened the outlines and more impor-
tant details which were too faint for the camera. In all other
respects the figures are exact reproductions of the authors'
drawings, a result only attainable by photography. Owing,
however, to the paper on which some of the figures in the
collotype plates were drawn having changed colour with age,
the ground is in some cases too dark, and in Plates XVII
and XVIII is not uniform in shade.

Plates I, y, VII, XI, XV, and XVI are from drawings by
Mr. Alder, and the figures are of the same size as drawn by
him. The rest, and all the text illustrations, are from
drawings by Mr. Hancock, and nearly all these are reduced
in size in various proportions.

JOHN HOPKINSON.

WEETWOOD, WATFORD,

27 th March, 1905.

LIST OF THE PLATES.

PLATE

Portrait of Mr. JOSHUA ALDER, from a photograph in
the possession of the Eev. Canon Norman

Frontispiece
I. — Ascidia mamillata.
II. — Ascidia mentula.

III. — „ details.

IV. — Figs. 1, 2. — Ascidia nibicnnda. Figs. 3, 4. — J..

Normani.

V. — Ascidia mollis.

VI. — Ascidia plana : blood-channels in mantle.
VII. — Figs. 1-4. — Ascidia rudis. Fig. 5. — A. renosa.
Figs. 6-8. — A. depressa. Figs. 9-11. — A. aculeata.
VIII. — Ascidia venosa : blood-channels in test.

X.— „ ,, branchial sac.

XI. — Figs. 1, 2. — Ascidia amoena. Figs. 3-5. — A.plebeia.
Figs. 6, 7. — A. sordida. Figs. 8, 9. — Probably a
variety of Corella parattelogramma. Fig. 10. —
Ascidia obliqiia.
XII. — Ascidia sordida.

XIII. — „ ,, reproduction.

XIV. — Ascidia Mon-i.

XV. — Figs. 1-7. — Asddia scalra. Figs. 8^ 9. — A affinis. .
XVI. — Figs. 1-3. — Ascidia pustulosa. Figs. 4-7. — A. ellip-

tica. Figs. 8, 9. — A. pellncidn.
XVII. — The branchial sac in Ascidia.
XVIIL-

XIX. — The mouth and oral lamina in Ascidia.
XX. — The branchial tubercle in Ascidia.

CONTENTS OF VOL. I.

PAGE

INTRODUCTION .

ANATOMY AND PHYSIOLOGY . 20

THE TUNICS . -0

THE DIGESTIVE SYSTEM

THE REPRODUCTIVE ORGANS . 28

THE BLOOD SYSTEM ....

THE BRANCHIAL TUBERCLE AND NERVOUS SYSTEM 49

SALPA AND ITS RELATIONSHIP WITH OTHER TUNICATA . 51

THE RELATIONSHIP OF THE TUNICATA WITH THE POLYZOA

AND LAMELLIBRANCHIATA . 58

CLASS TUNICATA . 63

ORDER 1. SACCOBRANCHIATA 63

TRIBE 1. SOLITARIES . 63

FAMILY 1. ASCIDIAD^; . . 64

GENUS 1. ASCIDIA . 64

INDEX OF SPECIES, ETC., DESCRIBED .

ILLUSTRATIONS IN THE TEXT.

FIGS. PAGE

1. — Ascidia scabra : test and mantle . . 22

'2. — A. xorilnla : hepatic tubes and globular vesicles 24

•3. — A. affinis : hepatic fubes . . .25

4. — A. renosa : blood-lacunas and muscular bands . 34

5, 6. — A. mentula : endostyle . 43

7. — A. Alder i : tentacles . 47

8. — Ciona fascicularis : tentacles . . 48

9. — Cynthia tcliiinita : tentacles . . .48

10,11. — Ascidia mentula : nerve-ganglion . . 50

12. — A. mentula: intestine, etc. . . .62

13. — A. mamiUata : branchial sac . . 74

14. — A. mentnlti . . . . .76

15. — A. robust a . . . .81

16. — J.. ruln-fitinrtn. . . . . .86

17. — A. crassa . . . . .89

18.— A. moll is 92

19. — A. plena .... 95

20.— A. Alderi 98

21.— A. producta . 106

22.— A. inornata 108

23. — A. Morel: branchial sac 127

24. — A. •inoUls 145

BRITISH TUNIC AT A,

INTRODUCTION.*

NOTWITHSTANDING the great amount of labour which
has been bestowed on the investigation of the Tunica t a
for many years past, these curious and interesting
creatures do not yet appear to have found their final
resting-place in the classification of the Animal King-
dom. Naturalists are still divided in opinion as to
whether the Tunicata, together with the Bryozoa,t
should fall into rank at the bottom of the great
Molluscan sub-kingdom, whether they form an ab-
normal group which should be placed in the sub-division
Molluscoidea of Milne- Ed wards, or whether it is desir-
able to unite the Brachiopoda with them.

Our recent researches, however, have forced upon us
the conclusion that the subjects of this monograph
are indeed true Mollusca closely related to the Lamelli-
branchiata — much more closely than they are to either
the Bryozoa or the Brachiopoda ; and that, whilst the
two latter groups may be kept apart in a sub-class or
subdivision by themselves, the Tunicata should be
placed with the Mollusca.

* Additions to the aiithors' MS. are placed within brackets in the usual
manner, except obviously editorial footnotes. A few verbal corrections have
been, made which are not so indicated. In the historical portion of the Intro-
duction the original spelling- of generic and specific names has been retained.

t This term is here retained in deference to the adoption of it by the
authors, although the right of priority rests with Polyzoa. On this point,
and also on the intimate relationship existing between the Tunicata and the
Polyzoa, see Allnian's ( Fresh-water Polyzoa ' (Ray Society, 1856), and the
papers referred to on pages 6 and 43 of that work.

1

Z BRITISH TUNICATA.

We shall, therefore, consider the Tunicata as the
lowest members of the Molluscan series, touching, on
the one hand, the Lamellibranchiata, on the other the
Bryozoa and the Brachiopoda. They are all marine,
shell-less, headless, footless mollnsks of a comparatively
low organisation, having an elastic external envelope,
test, or outer tunic, the homologue of the ordinary
molluscan shell, and an internal tunic or mantle ; they
are provided with a well-differentiated digestive appa-
ratus, usually with a sac-shaped gill placed in front
of the digestive organs, and leading to the mouth ;
with rather well-developed muscular organs, in which
the heart is tubular, forcing the blood for a while in
one direction, and then reversing its action and
forcing it in the opposite direction. They are all
androgynous, with very complete reproductive organs,
and all undergo a metamorphosis, while the greater
number of them increase by buds as well as by ova.

They are mostly attached, apathetic creatures, en-
joying locomotion only in their first, or larval, or
tadpole state, and being provided with an inhalent
and an exhalent tubular orifice, their food, which is
composed of microscopic organisms and sedimentary
matters, being drawn to the mouth by the respiratory
currents. The members of a large tribe, however,
are pelagic in their habits, being for ever in action
near the surface of the ocean, swimming b}^ the aid
of their respiratory currents, which in these instances
have the threefold office to perform of aiding in
respiration, in nutrition, and in locomotion.

And, finally, the Tunicata are either simple or com-
pound— simple when [each individual is] encased
in a separate external envelope, compound wdien the
test, or outer tunic, is fused or expanded so as to
include many individuals in one general envelope.

Though the Tunicata have had much attention
bestowed on them of late years by the thoughtful

*/ */ O

naturalist, they have generally been much neglected
by, and are but little known to, the casual observer,

INTBODUCTION. 3

partly on account of the unattractive appearance of
many of the species, but more so because of the im-
possibility of making them into pleasing objects for
the cabinet, as all colour leaves them when they are
placed in spirit. It would be erroneous, however, to
suppose that they are devoid of beauty, for many of
them must rank among the most charming objects
met with in our rock-pools, and some species from the
deeper waters rival, in the intensity and purity of
their colours, the rich hues of fruits and flowers.
Many are splendidly hyaline, others, again, are just
transparent enough to reveal the mellow tints of their
viscera, producing a rich, lucid appearance. But the
most attractive of all are perhaps the stellate Botrt/lli,
which spread over stones and fuci in large gelatinous
patches of brilliant green, orange, red, and yellow, the
colours being intensified in the individuals which are
immersed in, and studded over, their investing test in
radiating systems.

They are all possessed of the highest interest to
the philosophical inquirer on account of their physio-
logical and anatomical peculiarities, as well as for the
light which they throw on the structure of their
zoological relatives, leading as they do to a fuller com-
prehension of the organisation of the Lamellibranchiata
on the one side, and of the Bryozoa and the Brachio-
poda on the other.

The Tuuicata are the Tctlnjum of Aristotle.* They
were well known to the Father of Natural History, who
appears to have justly appreciated their true nature,
for he recognised their relationship to the ordinary
bivalve Mollusca, and was aware that the test was the
homologue of the shell of the higher mollusk.

After his time scarcely anything f is heard of these
animals until about the middle of the 16th century,

* ['Historia Aninmlium/ lib. iv, cap. 6; and ' De Part. Anim.,' lib. iv,
cap. 5. (Cir. B.C. 330.) ]

t " Nothing " in the authors' MS., biit see Pliny, ' Hist. Anim./ lib. xxxii,
cap. 30, 31, and Julian, ' De Nat. Anim.'

4 BRITISH TUXICATA.

when a few species were noticed by several naturalists
who confused the subject by placing them with the
Alrijumn-id. It was not until the 12th edition of the
' Systema Naturae' of Linnaeus appeared [i, 2 (1767)]
that the simple forms were drawn together under the
generic appellation of Ascidia, the name Tetlujs being
restricted by Linnaeus to the animal of the Bivalves.
The union of Trtlujum with the AsciJiirm, of Baster
[' Opusc. Subsec.,' i (1760)] had already been suggested
by Pallas [' Miscel. Zool.' (1766)], 'and both these
naturalists observed the resemblance of these animals
to the bivalve Mollusca, as indeed did Linnaeus.

Cuvier's first observations on the Tunicata were
made in 1797 [in ' Bull. Soc. Philom.']. Then followed,
in 1815 [in 'Mem. du Mus.,' ii ; see also 'Mem. des
Moll.' (1817)], his anatomical researches, which gave
a solid, sound foundation as a starting-point for
succeeding investigators. This profound anatomist,
whose observations were extended to the compound
forms, determined the high differentiation of the
organism, and proved the close relationship existing
between the Tunicata and the Mollusca. But it is
erroneous to assert, as some have done, that these
justly-celebrated investigations had been carried as
far as it was possible to carry them with specimens of
Tunicata preserved in spirit. All the organs can be
fully determined in simple Ascidians so preserved, not
excepting the heart and the vascular apparatus even
to its minutest ramifications. AYhat Cuvier did he
did well, and he achieved all that was demanded of
him by the requirements of science at that time.

Cuvier was also the first to recognise the affinity of
the simple and compound Ascidians, but Pallas seems
to have suggested this in the few preliminary remarks
to his description of the Botryllus steUntns of Graertner
[' Spic. Zool.,' fasc. x (1774)]. Cuvier advanced this
opinion in the report on Savigny's celebrated
" Memoires ' \_Sur les Asd^ics rni)i]_>o*<'<'S cf les A$rirUt->x
simples] read on the 8th of May folio wing the date of their

INTRODUCTION. O

presentation to the Institut de France. These memoirs
were read at the Institute respectively on the 6th of
February and the 1st of May, 1815, and were published
in the following year in Savigny's well-known work
entitled 'Memoires sur les Animaux sans Vertebres.'
Together with Cuvier's labours of about the same date,
they mark a great epoch in the study of the Tunicata.
Savigny's researches separated at once and for ever
the compound Ascidians and the Polypes, and enabled
Cuvier, from his previously-acquired information, to
suggest the. intimate relationship existing between the
compound and the simple forms, which hence became
an accomplished fact.

Lesueur and Desmarest's researches on the compound
Ascidians were communicated to the Institute of
France in the same year [1815, in ' Bull. Soc. Philom.'].

The ' Histoire naturelle des Animaux sans Vertebres '
of Lamarck was published in the years 1815 to 1822.
This philosophical naturalist, having availed himself
of the then recent labours of the above distinguished
observers, instituted the class Tunicata to embrace the
simple and compound Ascidians, the latter including
Salpa. From a mistaken apprehension of the structure
of these animals he separated this class from the
Mollusca and placed it between the Radiata and the
Vermes ; yet in a certain sense he appears to have
appreciated the connection which exists between the
Ascidians and the Lamellibranchs, for he says that
" the series of the inarticulate animals, commencing
with the infusoires, is continued by the p»1iji>cs, the
t tmiciers, the acalephes, and is terminated by the
molliistjiK's, of which the last orders are the cepJialopodes
and the heteropodes"

In 1819 Cliamisso [' De Anim. Verm.'] gave to the
world his startling observations on the reproduction of
Sol pa, in the " alternation of generations," as he at
the time termed the phenomenon.* The report of

* [For an account of Chamisso's observations see Steenstrup's ' Alterna-
tion of Generations/ translated by George Busk (Ray Society, 1845).]

6 BEITISH TUNICATA.

this curious mode of reproduction was received with
astonishment, as it was deemed to be unparalleled in the
history of animals, although it was well known to the
discoverer of Sotri/Uus that it was a compound animal
which increased by pullulation. Pallas announced
this fact on the authority of Gartner in his ' Spicelegia
Zoologica ' in 1774. Chamisso's observations were
confirmed by Krohn [in 1841].*

In 1821 H. Kuhl and van Hasselt discovered the
flux and reflux of the blood in Salpci ; that curious and
characteristic feature in the circulation of the Tunicata,
that ebb and flow in the current, first setting1 for some
time in one direction and then flowing in the opposite.
Since this peculiar action of the blood-current was
made known there has been no lack of subsequent
observers who have verified this extraordinary fact in
almost every genus in the entire class ; and, indeed,
there is no difficulty in witnessing the marvellous
sight, as no preparation is required ; all that has to
be done is to place under the microscope a young
individual of almost any species so as to secure the
necessary transparency, and the phenomenon may be
observed for any length of time.

The next important discovery was made by Audouin
and Milne-Edwards in 1828 ['Ann. Sci. JNTat.,' xv]
Avhile they sojourned at the lies Chausey. There these
two celebrated observers ascertained for the first time
that the compound Ascidians undergo a metamorphosis;
that these animals, so immovably fixed in their adult
state, are free during the first period of their existence
and swim freely about by the aid of a long, broad tail.
It is evident, however, that Savigny had previously
seen the first, or tadpole, state of Botri/llus, as in
Plate xxi of his ' Memoires ' he gives two figures of
it, but calls them, in the description of the plate, " two
side-views of an e^ef arrived at its mature state.'

~

* [Also in the same year by Sars, who said of the Salpse that " it is not
their larvae which are developed into the perfect animal, but the progeny of
the larvae." See Steenstrup, op. cit., p. 46. j

INTRODUCTION. 7

Lister made known, in 1834, his important observa-
tions on the circulation in a minute social Ascidian,
afterwards named by Wiegmann PeropJiora Listeri. His
remarks were published in the ' Philosophical Trans-
actions,' and prove that, as in Sertularia and Gam-
vannlaria (Hydroida), there is in this Ascidian a
circulation common to many individuals or to a whole
system of combined individuals. The author also gives,
in his admirable memoir, a more complete account of
the blood-circulation existing in the Tunicata than any
that had previously been published. The figures are
very good. The memoir is entitled " Some observations
on the Structure and Functions of Tubular and Cellular
Polypi and of AsciJice-"

Then followed, in 1830 [in ' Weigm., Archiv.'], Sars'
very curious observations on the metamorphosis of
Botryllus, showing that one larva enclosed several
young, united and already arranged in order ; that it
is in fact not a mere individual but a compound system
of individuals swimming* freely about in the external

• i •

form of the usual tadpole larva. This extraordinary
fact has been verified by the subsequent observations
of many other naturalists.

In 1842 Milne-Edwards' beautiful memoir entitled
" Observations sur les Ascidies Composees des cotes
de la Blanche ' was published. It was read before
the Academic des Sciences in 1839. In this memoir,
which will ever be looked upon as one of the most
admirable ever produced in this field of enquiry, the
anatomy and embryology of these animals are treated
at great length, and the author fully verifies the con-
clusions of Savigny. He supplies many points which
were left undetermined by that indefatigable observer
relative to the reproductive, vascular, and respiratory
organs. He also describes several new species, and
proposes to arrange the Ascidians in three divisions,
namely, the Simple, the Social, and the Compound.
The social Ascidians, however, pass by such a finely-
graduated series from the compound to the simple

BRITISH TUNICATA.

forms that it appears impossible to give to that group
any definite boundaries. Milne-Edwards' paper is
beautifully illustrated with coloured plates.

In the year 1845 Schmidt, in his work ' Zur verg-
leichenden Physiologic der wirbellosen Thiere,' made
known the startling discovery that cellulose was a
constituent of the test oiAsciilln or Phallusia mamillaris.
Lowig and Kolliker [in 'Ann. Sci. Xat.' (3), v] con-
firmed the statement of this distinguished naturalist, and
ascertained that this substance was present in the outer
envelope of different species of the genera Phallusia,
Ci/iifliin, Cl<rreUii/<f, Vin::<>ii<i, Aplidium, Didemnum,
Botnjllus, I'l/i'nxnnia, and Snlpa, so there can be no doubt
that cellulose is a constituent portion of the whole of
the Tunicata.

AYithin the last few years several other important
papers have appeared on the structure and develop-
ment of the various forms of these animals, amongst
which must be mentioned a memoir on the embryology,
anatomy, and physiology of the Simple Ascidians by
Van Beneden, published in the Memoirs of the Eoyal
Academy of Belgium [xx (1847)]. From 1846 to 1852
Krohn published several important papers on the re-
production and development of the Tunicata. Professor
Huxley's various contributions on the structure of the
Tunicata were also published at about this time. His
excellent memoirs " On the Anatomy and Physiology
of ftalpci and Pyi-osoma" and " On the Anatomy of
Appendicularia and DoUolini/," were printed in the
' Philosophical Transactions ' for 1851. In the former,
Chamisso's facts as to 8<ilpn are tested and confirmed,
and the results of Krohn's paper 011 the same subject
are verified. Papers of high merit on the Tunicata
have also been published by Cams (1816-21), Eleven
(1832-35), Eschricht (1839-43), Steenstrup (1842),
Sars (1846-47), and others.

Little was done in working out the species of the
Tunicata in early years ; a small number only being
described by a few distinguished naturalists, one of

INTRODUCTION. 9

whom, Baster [' Opusc. Subsec.' i (1760)], described
a single species, probably a Mol</nl<<, wliicli he named
Ascidium, and thus this name was introduced into the
nomenclature.

In the 12th edition of the ' Systema Naturae ' [vol. i,
pt. 2], which appeared in 1767, only six kinds of simple
Ascidians are included, three of which appear to have
been added by Linnasus himself. They are placed in
the class Vermes, under the generic denomination of
AsciJici , a modification of Baster's name. The com-
pound forms are contained in the genus Alcyonium,
but there are only three or four species introduced.

In the 'Zoologica Danica' [1788-1816] Otto Fred.
Miiller described and figured twenty species [of AsciiUtr
and one , Distoma], many of the figures being very
characteristic and the descriptions full and accurate,
as is usually the case in the works of this admirable

t/

observer. Otho Fabricius gave eight species in his
' Fauna Grcenlaiidica ' (1780).

After this time many distinguished naturalists
enriched the fauna with additional species. Amongst
them may be mentioned Peron (1804), Lesueur and
Desmarest (1804-17), Savigny (1816-22), Cuvier
(1817), Chamisso (1819), Macleay (1823), Quoy and
Gaimard (1825-35), Lesson (1830), and Delle Chiaje
(1841) ; and as a consequence of the combined efforts
of these and other naturalists there were 147 species
introduced in the second edition of Lamarck's ' Histoire
naturelle des Aiiimaux sans Vertebres ' [1835-43].
Since then many species have been added to the list,
but it is not necessary in this monograph, devoted as
it is to the British species only, to enter further into
this branch of the subject than to observe that large
as the number may be of the known Tunicata, there
can be no doubt that a great many foreign species yet
remain to be discovered. In fact [while the pelagic
forms have attracted much attention], little has been,
done, comparatively, in the sedentary species.

We shall now turn our attention to the British

10 BRITISH TUXICATA.

authors, and ascertain what progress has been made
in determining our indigenous species up to the present
time.*

[John Ray appears to have been the first English
naturalist who mentions a Tunicate. In his 'Historia
Plantarum ' (1(386), under the section " De plantis im-
perfectis," he describes as the Bursa marina of Bauhin.
the species now known as Aplidium ficus, but he does
not record it as British. It is, however, a British
species, and the first Tunicate recorded from our
seas, being described and figured by John Ellis, as
A/ci/oiiiiiiii pulmonis instar lobattnn, in his 'Natural
History of the Corallines' (1755), from specimens
found at Whitstable, on the Kentish coast.]

The next recordt of a British Tunicate is met with
in the ' Philosophical Transactions' for 1756; a
Botryllus [found near the Lizard Point] is there de-
scribed by Dr. Schlosser, and Ellis named it Alcyonimn
carnosum.

Borlase afterwards described the same species in his
' Natural History of Cornwall,' dated 1758, and it was
in 1766 named Al<-//<n/hnu Schlosseri by Pallas in his
' Elenchus Zoophytorum.' [Borlase also described and
figured an allied species which Turton, in 1807, named
Alrinnilirni BorlasiiJ]

In his 'Spicilegia Zoologica' [1774] Pallas describes
four species [from the Cornish coast] on the authority
of Graertner, three of which are compound Ascidians ;
they are named Asc'ulio mamillaris, Botryllus stellatus
[= B. Schlosseri], />. conglomerating, and Distomus
variolosus.

In Pennant's 'British Zoology,' 1777 edition, a
species is described and named Ascidia nixlirn ; this,

* The autlfors carried this history up to the year 1863, leaving many blanks
in their MS. which they evidently intended to fill in. The editor has
supplied the missing1 records and brought tip the history to 1870, that being
the year in which the last paper on the Tunicata by either of the authors
appeared. All such additions are within brackets.

f " The first record" in the authors' MS.

INTRODUCTION 1 1

however, is not a Tunicate ; it is Psolus phantopus [a
HolothurianJ, and is tolerably well figured.

[In the ' Natural History of Zoophytes ' of Ellis
and Solander (1786), the first two British Timicates
are described as Alct/oui/rni pulmonar-ia and A. ScMos-
seri ; and in 1803 Montagu, in his ' Testacea Britan-
nica,' incidentally recorded Ascidia mentula from the
coast of Devon.]

Turton gives two species in his ' British Fauna,'
which was published in 1807. [These are Ascidia
rustica, on the authority of Pennant, a record which we
have seen is not that of a Tunicate, and A. mamillaris.
He also enumerates, under the generic name Alcyonium,
five species previously recorded, as A. Schhsseri,
A. Boi'Iasii, A. Ficas (sic), A. conglomeratum., and
A. ascidioides (of Pallas = - .Itistvutttx rariolosus, Grsertn.);
to which may be added Ascidia mentula to complete
the British records to that date.]

In the course of the next eleven years the number
of British species had increased to twelve, that being
the extent of the list introduced in Fleming's ' British
Animals ' [1828]. They are named as follows :-
Pandocia conchilega, Clavellina lepadiformis, Pirena
prunum, Cionaintestinalis, Pltalliixia mentula, P. rustica,
Polyzona variolosa, Sydneum turbinatum, Alpidiumficus,
Botryllus Schlosseri, B.conglomeratus, and Salpa ni<>ni-
liformis, none of which appear to have been added to
our fauna by the personal exertions of the author.

[Seven of the species enumerated above were additions
to the British fauna since the publication of Turton' s
list in 1807. Three of these were recorded by Pro-
fessor Jameson from Leitli shore in 1811 ('Mem.
Wernerian Soc.,' i), and were referred by him to
Mailer's Axcidia- rustica, A. pr/u/uni, and A. conchilega ;
one, Giona intestinalis, was added by Pennant, from the
Menai Straits, as Ascidia rirescens, in the 1812 edition
of his ' British Zoology,' in which he changed the
name of his Psolus from Ascidia, rustica to A. ebora-
censis, recognising that it was not Midler's A. rustica ;

12 BEITISH TUXICATA.

two, Glavelina lepadiformis and Sidnifum
were described by Savigny in his ' Animaux sans
Vertebres ' (1816) from specimens sent to him from the
English coast by Dr. Leach; and one, tin! pa moiiili-
t'oniiis, was described by Dr. Macculloch in his
'Western Isles of Scotland' (1819). Fleming omits
Gartner's Ascu.lia, mamillaris and Turton's Alcyonmm
Btniasii.

In the ' Edinburgh Philosophical Journal ' for 1830
Dr. Coldstream recorded four species from Scotland,
describing two, Synoicum riibririu from Lamlash Bay,
Arran, and A^ciilin m<jox« from East Loch, Tarbet, as
new. The others are SiJuyu-in. tnrl>ln<itinn and As<'i<lli
I'trniium, neither being a new British record.]

Dr. Lister described two new species in the ' Philo-
sophical Transactions ' for 1834. One of these was,
in the following year, named r<'>-<>i>li»r<i Lister i by
Weigmann ; the other, which was merely designated
Polyclinum by its discoverer, was afterwards named
Leptodinum Listerianum by Milne-Edwards,

[In the same year (before the publication of Lister's
paper) George Johnston (' Mag. Nat. Hist.,' vii) de-
scribed two new species of Aplidium from the Berwick
coast, A. fiJlax and A. imfin/s ; and Robert Templeton,
under the initials " C. M." (luc. rit.), described and
figured as new British species Ax<-'nl]« '? t/ni/i/m and
A. ': anceps, the latter from Belfast Lough.* In 1839
Sir John Dalyell (' Edin. new Philos. Journ., xxvi)
described the development through the tadpole state
(termed " spinula " l)y him) of a simple and a compound
Tunicate from the coast of Scotland which he named
respectively A.^-iilln ^ipilla and Aplblinnt cen-ticoxintt.
In the ' Report of the British Association ' for the same
year Forbes and Goodsir recorded Awlilin intestinalis
from the Orkney and Shetland Islands, naming as new
species, but not describing, A. rcltiitntu, A.-ruyosn (both
pre-occupied names), and A. rnltrnx ; and in the 'Report'

: The locality for Ascidia gemina is not given, but in 1840 William
Thompson ('Ann. Nat. Hist.,' v) recorded it from Strangford Lovigh.

INTRODUCTION. 13

for the following year they described a new genus,
Pelonnui, with two new species from the Scottish seas,
P. ron-in/iitti and P.yl<tbr<i. This year (1840) witnessed
a considerable addition to our list, eighteen species
being recorded by Thompson (' Ann. Nat. Hist.,' v)
from the Irish coast, of which the following ten were
new to our fauna : — the Ascul'm r<-liinrtt<i of Linnaeus,
Mailer's Ascidia renosn, A.aspersa, A. scabrn, A. y«r<il-
leloiji-t'iniiiw, and A. orbictilni-i*, and Savigny's Ct/ntltin
d«iidi<-«ns, Distoma rnbr-nui, Botnjllus Leachii, and B.
polycyclusJ]

Macgillivray, in his ' History of the Molluscous Ani-
mals of Aberdeen, Kincardine, and Banff,' published in
1843, describes only four species [as Cynthia tuleroxn,
Ascidia jn-iinuni, A. opuUun, and A. intestinalis~\, the first-
two of which were new to our shores. One of the four
was wrongly identified with Midler's AschUn prinnint,
[being the species since named A. sordida], and another,
A. opalinci, is the A. "parallelogramma of Miiller.

[In the following year William Thompson, in his
" Additions to the Fauna of Ireland ' (Ami. Nat.
Hist.,' xiii) recorded eleven species of which the fol-
lowing eight were new to our shores : — Asei<li« canwa,
Amaroucium proliferum, Leptoclinum gelatinosum., L.
ii/<ii-nliihiiii, L. iixjteruin, L. J/ii'inii (as aureuni), Botri/Hiis
(/I'li/Hiens, and B. bivittatus ; and in 1846 (op. fit.,
xviii) he added Botri/Uits albirnns and B. rotifera-.~\

Sir John Gr. Dalyell's ' Rare and Remarkable Animals
of Scotland ' was published in 1847-48. In it upwards
of twenty species of Tunicata are figured and de-
scribed ; but in most instances the figures and descrip-
tions are not sufficient to enable us to determine the
species. It is, therefore, quite impossible to say
whether the list contains anything new or not. Many
of the species are not named, and indeed several of
those which are named are erroneously identified with
previously-known species. The figures, though elabor-
ately got up, are of but little use. Sir John unfortu-
nately adopted the erroneous principles that a naturalist

14 BRITISH TUN1CATA.

should not illustrate his own works and that the figures
should not he larger than life. A natural-history
draughtsman's work will he complete in proportion to
his knowledge of his subject, and who can be so well
acquainted with his subject as the naturalist who has
determined the species ? An object ought to be drawn
of such size as is necessary for the accurate rendering

it

of form and character. In. minute and complicated
objects this can only be done by enlarging the repre-
sentation. So far as we are able to ascertain not a
single new Tunicate has been added to the British fauna
by Sir John Dalyell's labours.

The ' History of British Mollusca ' by Forbes and
Hanley [in 4 volumes] bears the date of 1853, though
its publication commenced in 1847.* Seventy-three
species are described in this work, [sixty in the first
volume,] seven of which were entirely new to science,
namely Leptoclinum punctatum, Molgida oculata, Cynthia
quadrangularis, C. infoi'iut*, 0. tes^Uatn, C. limacina,
and G. morns ; and thirteen were for the first time
recorded as British [,namely Polyclinum aurantinm,
Amouroucium Nordmanni, A. argus, Botryllus violaceus,
B. smaragdus, Botrylloides rubrum, Ascidia arachnoidea
( = ^4. mamillata), A. ritrea, Molgula tubulosa, Cynthia
microcosmiis, C. grossularia, C. ampulla, and G. nggre-
gat<i~\. In this work, also, there is found the first
record of a well-authenticated Snlpa in our seas, 8.
runcinata. Dr. Macculloch was the first to notice the
presence of this interesting genus in the British seas,
but his description and figure are not sufficient for the
determination of the species.

There is something more than a mere record of
species in the ' British Mollusca ' ; it contains an excel-
lent resume of the then state of knowledge of this

! Pp. 1-477 of the first volume came out in twelve monthly parts, dated
1848, but the first part, for Jantiary, pp. 1-40, in which are nearly all the
Tunicata, may have been issued before the end of the year 1847. Alder and
Hancock's date is therefore allowed to remain here, but in the synonymy
the date given for the first part is that which appeared on its cover, 1848.

INTBODUCTIOX. 15

interesting though somewhat neglected branch of mala-
cology, and the genera and species are all well and
fully described.

In the ' Catalogue of the Mollusca of Northumberland
and Durham ' published in the ' Transactions of the
Tyneside Naturalists' Field Club ' in 1848, the authors
of this Monograph enumerated thirty-one species of
Tunicata; of these sixteen are simple Ascidians, one is
a social Ascidian, and fourteen are compound Ascidians.
In all thirteen were for the first time described and
named, as follows : — Gi/uthiti corinren, Molgula nrenosa,
M. citrina, Ascidin xurdida, A. nlbiild, A. <lrjn-rxx<t, A.
elliptica, A. pellucida, Botryllus rulxins, B. r//v'.sw//x, B.
castnneus, Botri/lloides radiatn, and B. ranudo^i.

[In 1850 Mr. Joshua Alder added to these, in his
"Additions to the Mollusca," etc., in the same publica-
tion, a new species, Molgula siphonata; and in 1851
Forbes and Goodsir (' Trans. Roy. Soc. Edinb.,' xx)
described a new species, Sy-utetliys hebridicus,from the
Hebrides. In this year, also, the " Zoology of the
Scilly Isles ': by Victor Cams, appeared (' Proc.
Ashmolian Soc.,' Oxford, vol. ii). In it Cams records
fourteen Tunicates and founds a new genus, TIn/l«rinm,
describing as new species TJu/lcn-lmn NV//V//// and
Amareucium edentulum, and also adding to our fauna
Didemnum candidum and I), gelatmosum.

In the second volume of Forbes and Stanley's
' British Mollusca ' (1849), twelve of Alder and
Hancock's species of 1848 are introduced, including
Molijula arenosa substituted for J/. tu.l>id<jx<i of their
first volume, M. citrina being omitted ; and in the
fourth volume (1852) Syutetlujs hebridicus is added.
In this volume, also, there is the first notice of the
occurrence of Appendicula/ria in our seas, as having
been found "off the north coast of Scotland in 1845,"
but the name of the species is not given. It was
probably A. ftacjellnm, Cham., which was recorded from
Tenby (as A. flabellum) by Professor Huxley in 1856
(' Quart. Journ. Micr. Sci.,' iv). The number of species

16 BRITISH TUNIOATA.

admitted into this work (including Appendic'idaria,sp.
hid.) was thus raised from 60 to 73.]

In his ' Natural History of Ireland ' [iv (1856)] Mr.
Thompson enumerates 42 species, of which two are
new. [Amoroucium albiran* is one of these ; the other
appears to be that named Ascidia mamillaris, Delle
Chiaje, which is not Miiller's A. mamillaris, previously
recorded, and probably not Delle Chiaje's species.

In this year (1856) Philip Henry Grosse brought out
his ' Manual of Marine Zoology for the British Isles/
in which he enumerates 66 Tunicates. These are the
60 in Forbes and Haiiley's first volume, Aplidium verru-
cosum, AmoBToeciurn alln'can*, Syntethys hebridicus, Cla-
velliua producta, C. pumilio ?, and Appendicularia
llaijcUum ?, the two species of Clavellina appearing to
be first records. Gosse omits Alder's fourteen records
of 1848 and 1 850, and the four records of Cams (1851).]

The Rev. A. M. Norman published [in J 857] a list of
the " Mollusca of the Firth of Clyde " [' Zoologist,' xv]
in which are enumerated sixteen species of Tunicates
as denizens of that district, but not one of them was
new to the British fauna.

[In 1860 Mr. John Stanger recorded in the ' Trans-
actions of the Tyneside Naturalists' Field Club ' (iv),
from Craster, Northumberland, Cynthia vestita, a new
species named and then only briefly described by Mr.
Alder. In the same year Mrs. Merrifield, in her
1 Natural History of Brighton,' recorded eight species,
seven of which appear to be new to Brighton, but not
one new to Britain.

The "List of the British Marine Invertebrate Fauna,"
drawn up for the Dredging Committee of the British
Association by Mr. Robert McAiiclrew ('Rep. Brit.
Assoc.' for 1860), enumerates 73 species of Tunicata, in-
cluding Appendic ul 'aria, sp. hid., but this list was solely
compiled from Forbes and Hanley's ' British Mollusca,'
and therefore omits all the species added to our fauna,
except Sifnfctln/s Jiebridicus, from 1848 to the date of its
publication in 1861.]

INTRODUCTION. 17

In 1863 Mr. Joshua Alder published, in the ' Annals
of Natural History ' [ser. 3, xi], " Observations on the
British Tunicata," in which the following twenty-two
new species are described: — Ascidia pustulosa, A.
obliqiKt, A. i-iidis, A. plebeia, A. ctGuleata, A. pulchella,
dx sorialis, Cyittltin sguamulosa, G. rosea, G. sul-
, C. granulata, G. opalina, G. violacea, G. glomerata,
Thylacium Xornuuii, T. variegatum, PolycUnum suc-
c'uieum, P. cerebriforme, Amaroecium papillosum, P<ir«*-
cidia flabellata, Botrt/lloides sparsa, and B.pusilla; and
two other species [Amar'oecium pomum and Distoma
rifrenm of Sars] are for the first time recorded as
British. [The name Cijntltin <-<>ni<it« is also newly pro-
posed for the G. ampulln of Forbes, not of Bruguiere ;
and for two species, considered to have been referred
in error to Savigny's Sidnyum turbinatum, the names
S. Flemingii and S. Forbesii are proposed.] Remarks
are made on seven other species and on several genera,
and the spiral arrangement of the minute vessels of
the branchial sac in Ascidia [Gorella] pafallelogramma
and Molgulu arenosa is described and figured.

From the above summary, exhibiting the sequence
of the discovery of the British Tunicata, it appears
that up to 1863 one hundred and six* species stand
recorded. Since that date several more have occurred,
chiefly by the exertions of our friends, and more par-
ticularly by the never-ceasing research of the Rev. A.
M. Norman and Mr. J. Gwyn Jeffreys. The researches
of Mr. Norman have not only added new species to the
list, but have also very materially increased our know-
ledge of their distribution in the British seas. We are
indebted to many other eminent naturalists for similar
services, amongst whom we have pleasure in mention-
ing our friends Dr. J. S. Bowerbank, Prof. Allman, the

* " Ninety-nine " in the authors' MS., biit to the 73 in Forbes and
Hanley's ' British Mollusca ' must be added Molgula citrina (1848), M .
siphonata (1850), Thylacium Sylvani, Didemnum candidum, D. gelatinosum,
and Amaroucium edentulum (1851), Clavelina producta and Amaroucium
albicans (1856), Cynthia vestita (1860), and the 24 records of Alder (1863).
All these additional species are included in this Monograph.

2

18 BRITISH TUN 1C ATA.

Rev. Thomas Hincks, Dr. Gr. S. Brady, Mr. George
Hodge, Mr. A. J. More, and Mr. C. W. Peach.

[Between 1863 and 1870 several valuable papers on
the British Tunicata and their distribution appeared.
It will suffice to mention the more important contri-
butions of Dr. W. C. Mclntosh, the Rev. A. M.Norman,
and the authors of this Monograph.

In 1865 Mr. Alder reported on the Mollnsca found
in deep-sea dredging on the coasts of Northumberland
and Durham in 1862 to 1864 ('Nat, Hist. Trans.
Nortlmmb. and Durh.,' i), giving a list of ten species
collected along the coast and on the Dogger Bank, but
not adding any new British record. In the same year
Scdpa spinosa was added to our fauna by Dr. Mclntosh
from the Hebrides, and the Rev. A. M. Norman from
(luernsey, but Mr. Norman's paper communicating his
discovery to the British Association was not published.
Dr. Mclntosh's paper was read before the Royal Society
of Edinburgh and published in the following year
(' Proc.,' v). In it he gives a list of twelve species from
North Uist, Outer Hebrides, including this titdpa and a
new species of Cynthia which he named C. ii'istise.
This list was considerably extended in 1867 by Mr.
Alder, who enumerated nineteen species in a report on
dredging among the Hebrides in July, 1866 (' Rep.
Brit. Assoc.' for 1866), but without making any addi-
tion to the British fauna. In the " Shetland Final
Dredging Report ' of the British Association (' Rep.
Brit. Assoc.' for 1868) the Rev. A. M. Norman enu-
merated twenty-seven species determined by Mr.
Alder, adding considerably to our knowledge of the
distribution of the Tunicata in the Scottish seas, but
not giving any new British record, for although he
gives Ascidia obliqua, A. rudis, A. plebeia, and Poli/cli-
n inn siiccineum as " species added to the British fauna
during the recent dredging'1 (i.e. 1861-67), these
species had been sent by him to Mr. Alder, who
described them in 1863.

The last paper to be mentioned is one by Mr.

INTRODUCTION. 19

Hancock, published in 1870, " On the Larval State of
Nitlijulii ; with Descriptions of several new Species of
Simple Ascidians " (' Ann. Nat. Hist.,' ser. 4, vi), in
which he comes to the conclusion, from his own re-
searches and those of Van Beneden and Lacaze-
Duthiers, that there are two distinct modes of develop-
ment in closely-allied genera of the Tunicata, the
tadpole-condition being non-essential, a discovery which
he said might have some effect on the theory of the
relationship of this group with the Vertebrata. He
describes two new genera, Corella and Einji/rn, and the
following nineteen new species: — Ast-i/lin ^l<ntn, A.
, A. nibro-tincta, A. ruJtirinnJn, A. rolnsta, A.
lx, A. cfitxxn, A. iitoi-nntit, A. /n-iuJnrta, A. elonr/atti,
A. <inin it, A. Xoi'uif/i/i, Cin-i'Uit larvdeformis, C. ofntn,
Oiona fascicularis, Molgula svmj_il<',i^ M. inconspicua, M.
complanata, and Eu</i/r« <jl<>l><>xa.

These species, with those previously described by
the authors, are for the first time figured in the present
Monograph.]

Having now gone over the history of the discovery
of the Tunicata, both structural and zoological, we
shall give in detail a full account of the organization of
the entire class.*

* As Albany Hancock died before the conclusion of his investigation
of the Tunicata, and had not written that portion of the introduction to
this work which would have embraced his latest views of their anatomy and
physiology, a paper which he contributed to the Linnean Society of London
in 1867 is here reprinted from the Journal of the Society by permission of
the Council. The only alterations which have been made in this paper are
the substitution for Ascidia of the generic names Ciona and Corella, and for
Molgula of the new generic name Eugyra, for certain species subsequently
referred to these genera by the author, and of Styela for Stycla, as Savigny's
genus erroneously appears in the paper ; also the insertion of the names of a
few species which wei-e then iindescribed, of sxib-headiugs, and of illustrations
from the author's drawings. Some portions of the paper which treat specially
of the anatomy and physiology of Ascidia and of a few other genera are
repeated, with or without modification, in the descriptions of those genera.

'20 BRITISH TUNICATA.

ON THE ANATOMY AND PHYSIOLOGY OF THE

TUNICATA.

By ALBANY HANCOCK, F.L.S.

[From ' Journ. Linn. Sue.,' Zool., vol. ix, pp. 309-336.]

HAVING employed myself recently in the investigation of the
Timicata (their anatomical structure and physiology) with a
view to a monograph of the British species, which my late
lamented friend Mr. Alder and I had undertaken to prepare
for the Ray Society, some very interesting anatomical facts
have come to light ; and I now propose to give a succinct
account of the more important of these, believing that they
cannot fail to be acceptable to those naturalists who may have
studied these low but not by any means unattractive mollusks.
I reserve, however, for some future occasion a more complete
and detailed description.

When I took up this subject, I had little expectation of
meeting with much that was new ; for perhaps in no other
group of the Molluscan subkingdom has the anatomy been so
frequently and so ably investigated as it has been in the
Tunicaries ; and, indeed, in them, all the leading points appear
to have been fully determined ; but experience proves, never-
theless, that much of interest has been left unobserved, quite
sufficient to reward the labour of re-examination, and seem-
ingly ample enough to modify some of the more important
morphological determinations.

This unexpected result may, in part, be owing to the fact
that, while my researches have been chiefly confined to the
simple Ascidians, it is apparently to the compound, social, and
pelagic forms that the greatest attention has been hitherto
given. Thus it happens that numerous details have remained
until now unnoticed in the former group.

THE TUNICS.

There is something fresh to record in nearly all the visceral
organs, but in none so much perhaps as in the vascular and
respiratory systems. Before entering, however, 011 such new
matter, it will be well to say a few words respecting1 the tunics,
so characteristic of these animals. In all the various forms
that have been examined there is no great difficulty in deter-

ANATOMY AND PHYSIOLOGY. 21

mining the presence of three tunics, or envelopes — namely,
the test or outer tunic, the mantle or inner tunic, and the
lining- membrane or inner tunic of Prof. Huxley.* The lining-
membrane and mantle are always, to a greater or less extent,
adherent to each other, and have, except where there is an
abdomen developed, all the viscera and the lac unary portion
of the blood-system placed between them. On the other hand,
the mantle and test in A*ei<lia and Molyula are always free,
except at the distal extremity of the respiratory tubes, where
they are united ; there is also an attachment at the point
where the vascular trunks enter the test. But in the genus
Styela (Savigny's third tribe of Cynthia) the test is always
more or less firmly attached to the mantle throughout, though
at the respiratory orifices the adhesion is greatest. In all the
species, however, that have been examined, with the exception
of one (a small undescribed species [$. humilift, sp. nov.]),
these two envelopes maybe separated without much difficulty
in specimens preserved in spirit. In the exceptional case
alluded to the mantle is exceedingly delicate; and hence prob-
ably arises the difficulty of separating it from the test. In
this genus, as well as in Axcnlia and Molyula, blood-vessels
pass from the body to the test. It is therefore likely that
vessels will be found ramifying in the outer tunic in all the
simple Ascidians. In Pelonaia the adhesion of the mantle
and test is not by any means so remarkable as was originally
supposed ; and, indeed, in this form they are as easily divided
as they usually are in Styela. Also in Clavelina these two
tunics are slightly adherent throughout, while in Salpn they
appear to be as free as they are in Ascidia.-^

It should be mentioned that, in a living state, unless the
mantle be violently contracted, there is no actual vacant space,
<>r space filled with fluid, as has been asserted, between it and
the test ; even in those species which have these tunics com-
paratively free the two siirfaces lie in close contact. When
the animal is dead, however, and preserved in spirit, the body
enclosed in the mantle does not by any means occupy the
entire space within the test, but lies somewhat shrivelled, and
frequently quite free (fig. 1, p. 22), just as commonly happens
with the animal of the Lamellibranchs within its shell under
similar circumstances.

This tunic was first pointed out by M. Milne-Edwards, in his work on
the ' Ascidies Composees/ p. 54.

t I have examined only one species of Salpa, namely 8. spinosa, and the
specimens were preserved in alcohol.

99

BKIT1SH TUNTCATA.

The chief function of the test, like that of the shell in the
higher mollusks, is no doubt to protect the comparatively soft
and delicate portions of the animal that lie within it. But it
will also act, by its resiliency, as a counterpoise to the muscular
contractility of the mantle, which lines it as it were. In those
species, such as Styela tulerosa, in which the mantle and test
are adherent throughout, this action is readily understood ; it
is not,, however, quite so obvious in the species which have
these two tunics comparatively free, as they are universally in
Ascidia and Molgula. But we have just seen that, in such

Distal or anterior.

br.f. Ir.m.

aa.t.

Ventral.

Dorsal.

Proximal or posterior.

FIG. 1. — Ascidia scabra. Left side. t. Test (outer tunic). m. Mantle
(inner tunic), br.t. Branchial aperture of test. Ir.m. Branchial aper-
ture of mantle, aa.t. Atrial aperture of test. aa.m. At rial aperture of
mantle. Three times natural size. From a specimen preserved in
spirit, with the mantle shrunk.

instances, the inner surface of the test, and the outer surface
of the mantle, lie in close contact with each other. Now, as
under all ordinary circumstances the pressure of the water
inside the mantle must be as great as that of the water rest-
ing against the outer surface of the test, and as no water can
possibly enter between these two tunics, it is clear enough
that they will be held together with no inconsiderable force.
Thus, when the muscles of the mantle contract, diminishing
the bulk of that organ, the test will be drawn in after it ; and
so soon as the muscles of the former relax, the latter, through
the elasticity of its walls, will expand, and the mantle will be
constrained to do so likewise.

ANATOMY AND PHYSIOLOGY. 23

THE DIGESTIVE SYSTEM.

The most interesting matter that I have to communicate re-
specting the digestive system relates to the biliary apparatus.
A remark or two, however, may be made, in the first place,
upon the alimentary canal, which, in all the species tha-t have
come under my inspection, makes its first bend towards the
dorsal region, assuming that to be the dorsal aspect where the
endostyle is placed. The intestine then usually ascends and
crosses over (in a more or less nndulatory course, sometimes
forming one or two loops) to the opposite or ventral side,
where it again ascends to reach the cloaca, into which, in the
Ascidians, it invariably opens. The walls, from one end of
the organ to the other, are particularly firm, and do not col-
lapse even in preserved specimens. The lower portion of the
intestine is the most delicate ; but even here the wall rarely
shrinks. The stomach is well marked, though it is never very
bulky, and is usually lined with a stout mucous membrane,
which is frequently plaited or wrinkled, sometimes in a sym-
metrical iiianner, the plaits extending into the oesophagus on
the one hand, and into the intestine on the other. In the
latter organ this membrane is thrown up so as to form a very
conspicuous groove which extends from the stomach to that
portion of the intestine which may be termed the rectum. In
Xtt/ela t'uberosa, and some other species, however, this groove
extends the whole length of the intestine.

The food of the Tunicaries is extracted from sedimentary
matters ; there is no power of selection in the first instance ;
those particles which can be, are digested ; the others, chiefly
composed of sand and mud, are rejected in the usual manner.
The sedimentary aliment is sifted from the water in the respi-
ratory sac by the aid of the branchial network, and is then
carried across the organ by the action of cilia; but no definite
arrangement of the particles takes place until they arrive at
the oral or ventral lamina, where they are formed into a cord
of some tenacity, apparently through the agency of mucus, and
are carried thus moulded along this lamina to the oral orifice,
and so swallowed. This alimentary cord is conducted through
the digestive tube, and is rejected in the same form by the
anus and excurrent tube. The cord-like fasces may frequently
be seen through the wall in the lower portion of the intestine,
having very much the appearance of a convoluted tube lying
within the canal. In some of the lower forms, however, it is
broken up into elongated pellets.

-!4 BRITISH TTJNICATA.

All this is very similar to what takes place in connexion
with the alimentation in the Lamellibranchs ; but in them the
lateral currents of particles are as well defined as the main or
central ones.

Molfjula, and Savigny's first and second tribes of his genus
Cynthia, appear to be the only forms among the simple Tuni-
cates that have hitherto been described as possessing a well-
developed liver. This organ is always sufficiently distinct in
these groups, and usually presents a laminated structure, but
is occasionally composed of tubular tufts or lobes, the colour

FIG. 2. — Hepatic tubes and globular vesicles in Ascidia sordida. Highly
magnified (£ in. object-glass).

being generally of a dark olive-green. I find, however, a true
hepatic organ in all the other genera examined (namely Ascidia,
Xft/ela, Pelonaia, Clavelina, and Perophora), quite distinct from
that gland-like substance coating the alimentary tube in the
first of these forms, and which has occasionally been con-
sidered to subserve the hepatic function.

This substance is of a very peculiar character, and it is diffi-
cult to say what its office really is. In all the Ascidix it forms a
pretty thick coating over the stomach and intestine, and is
composed of comparatively large globular vesicles with thin
reticulated Avails, each having a large, opaque, simple or com-
pound nucleus on one side (fig. 2). These vesicles have no

ANATOMY AND PHYSIOLOGY. 2-)

communication with each other, though they lie in contact and
are cemented together ; nor are they connected with any duct,
or in any way open into the alimentary tube. Blood-channels
are hollowed out, as it were, amidst the vesicles; and the
reproductive organs ramify throughout the agglomerated mass
which overlies, for the most part, the true hepatic organ.
These vesicles will therefore act as a sort of packing to the
parts of these organs, and will give support and protection to
them, whatever higher function they may have to perform.
They may likewise assist the heart in the performance of its
work by their resiliency when the mass is gorged with blood ;
for it is evident that, when the interstices or blood-channels

FIG. 3. — Hepatic taibes in Ascidia affinis. The branches terminate in blind
sacs, and are rounded and enlarged a little. Highly magnified (1 in.
object-glass).

are filled, the vesicles will be more or less collapsed in pro-
portion to the pressure of the blood-current ; and when the
latter changes its direction the reaction will be assisted by
their expansion. In our present state of knowledge, however,
nothing positive can be said of the uses of this very curious
structure.

The true hepatic organ, as already intimated, lies beneath
this vesicular mass, and forms a thin coating on the surface
of the intestine. In all the examples observed it is composed
of delicate tubes, which divide dichotomously, but frequently
without much regularity. At the points where the branches
are given off, the tubes are usually enlarged, and the twigs
terminate in rounded extremities more or less inflated (fig. 3).

26 BRITISH TUNICATA.

The ultimate divisions of the organ are so minute that they
can only be observed by the aid of the microscope after a
portion of the intestinal tube has been removed,, laid open,
aud deprived of the mucous membrane, so as to render the
tissue as transparent as possible.

In Axf-iil/ft nientula the dichotomous division of the tube is
very obvious, and the enlargements or ampullae at the junc-
tion of the branches are greater than usual, and the}' assume
a triangular form ; also oval enlargements frequently occur
along the branches, which latter uniting- go to form two long
slender ducts that pass backwards within the loop of the
intestine buried amidst the vesicular substance already de-
scribed, and at length open through the left wall of the
stomach about midway between the cardia and pylorus,
towards the anterior margin. These two ducts come from
the middle portion of the intestine; another duct, passing
from the lower part of the intestinal tube, unites with one of
those first mentioned just before it sinks into the wall of the
stomach. All the three ducts are exceedingly slender; and
for their detection it is necessary to dissect carefully the
vesicular matter within which they lie buried : when thus
exposed their white walls can easily be traced, with the aid
of a good lens, running amidst the comparatively dark sur-
rounding tissue.

In Ascidia sordida and A. scalra the arrangement of the
parts of the hepatic organ is similar to that in the above
species; but in Corella parallelogramma the minute structure
is considerably modified. In this species there is a minute
network of anastomosing tubes spread over the intestine, the
tubes being divided into systems by the interruption of the
anastomoses along certain Hues where the twigs end in blind
sacs, which are occasionally a little enlarged and rounded.
The main branches leading from the network exhibit a ten-
dency to divide dichotomously, and unite to form two slender
ducts which pass at once from the intestine to the left side
and close to the posterior margin of the stomach, into which they
pour the biliary secretion a little in advance of the pylorus.

In Pelonain there is only one hepatic duct, which is very
slender, and passes in a fold of the lining membrane or
" inner tunic " of Huxley that extends from the intestine to
the right side of the stomach, a little way in advance of the
pylorus. Before terminating, it receives a twig- or two from
the surface of the stomach ; so that in this genus the liver is
apparently not confined to the intestine, but is also spread
over a portion of the stomach. The ultimate twigs divide

AXATOMY AND rHYSIOLOGY. '27

dichotomously with considerable regularity and terminate in
round or ovate vesicles, which are very numerous and form a
distinct, opaque, yellowish layer.

The liver in Styela is not more conspicuous than it is in
Avidia. It is well developed, nevertheless, and is provided
with its secreting vesicles and ducts. In S. tulierosa, and,
indeed, in all the members of this genus that have come under
my observation, there is a fold of the lining membrane
within the loop of the alimentary tube, which passes between
the stomach and intestine. This fold is united to the pyloric
end of the stomach, where there is a caecal prolongation of
that organ. The hepatic ducts lie within this fold ; and before
they reach the stomach, in this species, they unite to form
a simple, slender duct, which opens into the left side of the
caecum. The branches of the ducts ramify dk-hotomously
over the lower portion of the intestine, and communicate with
comparatively large rounded vesicles arranged like those in
Pelonaia.

In Chii-rliita there is only one hepatic duct, which passes
from the middle portion of the intestine and opens into the
alimentary tube immediately below the rounded stomach.
The branches of the duct ramify over the intestine, dividing
dichotomously, and ending in comparatively large, oval
vesicles. Exactly the same form of organ is observed in
1't'i-njiJiom • but in this genus the duct opens through the
right wall of the stomach, near the pylorus. The hepatic
organ in this interesting form was undoubtedly noticed by
Dr. Lister; for he figures and describes, in his well-known
memoir in the ' Philosophical Transactions/* " transparent
vessels" ramifying over the intestine; but he does not appear
to have observed the terminal vesicles, and the termination of
the duct in the stomach, or he scarcely could have supposed,
as he did, that the vessels he described were lacteals.

With this exception, this peculiar form of the hepatic-
organ seems entirely to have escaped notice until A. Krohn
gave a very good description of a similar structure in a paper
"On the Development of the Ascidians," published in Midler's
' Archiv,' 1852-53t. The species examined by this naturalist

* " Some Observations on the Structure and Functions of Tubular and
Cellular Polypi and of Ascidia?/' ' Phil. Trans./ 1834, p. 380.

f See ' Scientific Memoirs,' edited by Henfrey and Huxley, p. 328. Before
I was aware of the discovery by Krohn, I had worked out the details of the
hepatic organ in the genera mentioned in the text; it was therefore highly
satisfactory to find his description of this organ in A. mamillata agree so
closely with my observations, particularly in A. mentula.

28 MKITISH TUNICATA.

\vas Ascidia mamillata ; and although he appears to have
traced with great accuracy the development of the organ, he
seems to have failed in detecting the duct in the adult animal.
From the general characters, however, obtained by his exami-
nation of the young and adult combined, he is disposed to
conclude that the " secretion prepared in the ca3ca must be
accessory to digestion ; but whether or not the watery secre-
tion is bile, and the gland therefore a liver," he concludes,
"must for the present be left undecided." Nevertheless, after
the above description of the numerous modifications of the
organ, and particularly when the position of the duct in re-
lation to the alimentary tube is taken into account, few
physiologists will be inclined to doubt that this organ is a
true liver, though low and rudimentary in structure.

THE ^REPRODUCTIVE ORGANS.

The reproductive organs are well developed in the Tuni-
cates ; and in all of them the two sexes are combined in the
same individual, though the male and female elements are
always secreted by distinct organs, which,, however, frequently
compose one or more compound masses that have the parts so
intimately united that careful examination is required to detect
them; hence in several of the Cynfhiada? the testis has been
entirely overlooked .- the oviduct and ras deferens are likewise
constantly distinct.

In Axi'-idia xordida the ovary is composed of numerous
tubular branches which ramify in a radiating manner over
the left side of the looped portion of the intestine (PI. XIII).
The oviduct passes through the loop, and, following the
curvature of the intestine, opens by the side of the anus
into the cloaca. The vas deferen* terminates near to the
same point, and is adherent to the oviduct throughout its
course [as in A. mcntnla, see fig. 1"2, p. 62]. In the vicinity
of the ovary it receives several much attenuated branches
from either side of the intestine; these divide dichotomously,
the ultimate twigs terminating in elongated and irregularly-
lobulated vesicles which are spread over the intestinal tube,
and which also exhibit a tendency to dichotomous division:
these vesicles secrete the male element.

In A. xcalira, A. affini*, A. mentula, and A. venoxa the same
arrangement of the reproductive organs is apparent ; but the
ovary in A. mentnla is a lobulated organ, and, lying within
the loop of the intestine, is seen at both sides of the ali-
mentary tube, and consequently has the appearance of being

ANATOMY AND PHYSIOLOGY. 2<>

double; and in A. venosa the male vesicles are exceedingly
minute and are very numerous. In Corella parallelogramma
the geiiitalia have much the same disposition; the ovary,
however, which is branched and tabulated, is spread out >n\
both sides of the alimentary tube — as is likewise the male
organ, the secerning vesicles of which are clustered into
dendritic systems.

These organs, however, are modified to a much greater
extent in the Cijntldad& — in many of which it is not easy to
determine the parts, on account of their intimate union ; and
very careful examination is requisite in these cases. In Styela
tul>eruKa the so-called ovaries are very numerous, and are
studded over the inner surface of the mantle on both the
right and left side of the body, causing the lining membrane
to bulge out. When fully developed they form protuberant,
ovate, orange-coloured masses, each having at the attenuated
extremity a projecting nipple-like papilla. This is the oviduct,
leading out of the ovarian mass or ovigerous sac ; for each
mass is really a sac in the walls of which the ova are de-
veloped. And firmly attached around the base of these sacs
is a series of pale oval vesicles which are sunk in. the sub-
stance of the mantle, and which form for each sac a sort of
cup within which it rests. These vesicles are the male se-
creting organs, and their ducts, extremely delicate tubes,
pass upwards over the surface of the sac, and go to join, on
the median line, a slender vas r/r/'m -//.v, which, passing
forward, terminates at the extremity of the short nipple-
like oviduct above described. Thus it is seen that the
so-called ovarian mass is a compound organ, combining both
the male and female parts, each with its proper secreting
organ and duct. There are therefore as many oviducts and
outlets for the male secretion as there are compound repro-
ductive masses ; and the eggs must be shed everywhere into the
space between the branchial sac and the wall of the respiratory
chamber, and afterwards carried by the atrial currents to the
cloaca, and so pass out, as usual, by the excurrent tube.

These reproductive masses should not be confounded with
other very similarly-formed bodies that everywhere stud the
mantle, and fill up, to a considerable extent, the spaces between
the former. These latter bodies are most frequently pedun-
culate, and are sometimes as large as the reproductive masses,
from which they chiefly differ in colour, being pale, somewhat
pellucid, and almost homogeneous in structure. They do not
seem to have any high functional import, their office apparently
being to form, along with the generative bodies, a sort of pad

30 BRITISH Tl'NICATA.

or level surface for the support of the branchial sac, which
otherwise might suffer from the inequality produced by the
genitalia. These peculiar organs are found in all the ( ']/nth iadtf
that have been examined, including Pelonaia ; and in all the
reproductive organs project boldly from the surface of the
mantle.

This arrangement of the reproductive organs also occurs in
Sti/da nianilllarls, and in two undescribed species ofthe genus,
recently obtained by the Rev. A. M. Norman at Guernsey.

In Thylachint («j</r<'i/ntnm the same disposition of these parts
is also found to exist.

In Cynthia orata, an undescribed species allied to C. *<iuamn-
lo*a, we have a very remarkable modification of these organs.
Here there are only two generative masses — one placed im-
mediately above the alimentary tube, the other within the
intestinal loop. They are elongated and fusiform, each being
composed of a double parallel series of squarish nodules in
which both ovary and testis are combined. Each mass has
its own proper oviduct and i-as deferens, which pass forward,
united, between the series of nodules, and, extending a little
way in advance of the organ, open into the cloaca near to the
anal orifice.

But perhaps the most interesting variety of this apparatus
occurs in Pelonaia, in which there are two elongated tubular
ovaries, each being bent so as to form a wide loop ; they are
attached throughout to the mantle, and bulge out the lining
membrane; one is on the right, the other on the left of the
branchial sac in front of the greater portion of the alimentary
tube. The oviducts advance a short way beyond the ovaries,
and open into the cloaca, one on each side of the intestine, but
considerably in advance of the anal orifice. The testis is coin-
posed of numerous elongated, simple or lobed vesicles, which
are placed with one end in contact with the sides of the ovaries,
and are arranged in parallel order at right angles to them,
fringing both sides of these organs from end to end. From
the proximate extremities of the vesicles extremely delicate
ducts pass across the surface of the ovary, to which they are
attached, and go to join the vas deferent that extends along the
middle line from end to end of each ovigerous organ, and,
advancing along the oviduct, terminates at the extremity of
tli at tube.

I have not met with this peculiar arrangement of the
genitalia in any other species, though, after all, it is but as it
were an amplification of that which we have seen to exist in
the compound genital masses in Sfijeln, title rosa and its imme-

ANATOMY AND PHYSIOLOGY. 31

cliate allies. If one of these masses were greatly elongated,
so as to become tubular, and if the male vesicles were increased
in number, their lower extremities pulled from beneath the
ovigerous sac and stretched out on the mantle, we should have
something very similar to that which subsists in Pelonaia.

Another modification of these organs occurs in Styela varln-
bilis, an undescribed species related to Cynthia canopn*,
Savigny. In this the ovaries assume the form of distinct,
wide, slightly undulated tubes, of which there are two on the
right and two 011 the left side of the mantle, each having its
own short nipple-like oviduct which opens into the cloaca,
there being two on each side of the anus. The testis is com-
posed of numerous irregularly-lobulated vesicles scattered
over the lower portion of the mantle in the vicinity of the
posterior extremities of the ovaries, but with which they have
no connexion, each separate vesicle having its own short
nipple-like duct or vas deferetis.

The reproductive organs do not exhibit any great diversity
in the genus Molgula, the ovary and its testis being always
combined, and forming one or two elongated masses, in which,
however, the two component elements can always be detected
by the aid of their colour and structure. The testis is com-
posed of a vast number of branched vesicles or cascal tubules,
crowded together and sometimes assuming a dendritic appear-
ance, while the ovary seems to be a lobulated sac, usually well
filled with eggs.

In M. concliilega there are two such masses, placed trans-
versely, which are generally irregular in form, but sometimes
are broadly fusiform and a little arched. That 011 the right
side of the mantle lies upon the upper border of the intestine ;
the other occupies the centre of the left side of this tunic.
The oviducts are two short tubes ; they pass out of the ventral
or anterior extremitity of the mass, and open into the cloaca
on each side of the intestine. There are four or five long
nipple-like sperm-outlets, situated at a little distance from
each other along the body of the organ. These open directly
into the atrial space on either side of the branchial sac.

A similar arrangement of the genitalia, with numerous short
deferent canals, has been described by Van Beneden, in his
Ascidia ampulloides*, which is, there can be little doubt, a
Molgula. There are two similar genital masses in M. simpler ;
but they are comparatively slender, and are pretty-regularly

* " Eecherches sur 1'Enibryogenie, 1'Anatomie, et la Physiologie des
Ascidies Simples." ' Memoires de FAcademie Eoyale de Belgique/ xx (1847).

32 BRITISH TUNICATA.

fusiform : they are situated exactly in the same way as those
in the former species, but that on the right side is overlapped
liy the looped portion of the intestine.

In an midescribed species [Molgula complanata, A. and H.]
obtained by the Eev. A. M. Norman in Guernsey, the genital
masses are ovate, and are placed as usual, but differ from
those of all other species in having' the oviducts passing from
their dorsal extremities, and consequently turned towards the
endostyle instead of being directed to the cloaca. The pro-
ducts of these organs are consequently thrown into the dorsal
portion of the atrium, far from the cloaca.

There is only one reproductive mass in Euyijra nrenosa; it is
larger than usual, is of irregular form, and belongs to the
right side of the mantle, but overlies to a considerable extent
the alimentary tube. The oviduct, as usual, opens into the
cloaca ; but the rr/.s- deferens has not yet been observed, though
the male secreting-organ is distinctly visible, forming a con-
siderable part of the mass.

In Clarelina lepadiformis, one of the Social Ascidiaus, the
genitalia are placed in the loop of the intestine near to the
lower extremity of the abdomen, the ovary lying on the right
of the alimentary tube, and the testis being spread over both
sides of it. The former resembles a bunch of grapes in which
the berries are of various sizes ; and the oviduct, like the stem
of the fruit, is seen in the midst of the ova ; and I believe I
have traced it passing up the abdomen in the direction of the
cloaca, but I did not succeed in determining' its outlet. M.
Milne-Edwards, in his well-known work on the ' Ascidies com-
posees,'* states that he could not discover how the eggs
passed from the ovary to the neighbourhood of the branchial
sac, and suggests the possibility of the vas deferens acting also
in the capacity of an oviduct. This, however, is exceedingly
improbable ; and, from what I have seen, there can be little
doubt of the presence of a true oviduct, although I do not
consider my observation a sufficient demonstration of the fact.
But there can be no mistake as to the existence of a /v/.s-
difcrens; this tube is sufficiently conspicuous; passing- up by
the side of the alimentary canal, it penetrates the lower
wall of the cloaca, and terminates by the side of the
anal outlet. The testis is a much-branched organ ; the
branches are extremely fine, and, dividing dichotomously,
terminate in numerous elongated fusiform vesicles, which are
united in pairs ; or, in other words, the ultimate twigs may be

* ' Observations sur les Ascidies composees des cotes de la Mauclie/ p. 22.

ANATOMY AND PHYSIOLOGY. 33

said to bifurcate, each branch being immediately enlarged, so
as to form an elongated caecal vesicle.

THE BLOOD-SYSTEM.

The blood-system in the Tunicata is perhaps the most diffi-
cult branch in the anatomy to invest'gate ; for these animals
are generally too minute and delicate to be successfully in-
jected, and it is not easy to obtain living specimens sufficiently
transparent to permit of the blood-current being traced
through the tissues. Nevertheless much good service has
been done in this way by M. Milne-Edwards and others ; but
perhaps no one has done more by this method than Dr. Lister,
who had the good fortune to meet with a species in every
respect suited to the purpose. So far as I have been able to
ascertain, the blood-system has been as fully, if not more
fully, determined in Perophora than in any other Tunicate.
It is therefore satisfactory to find that my results perfectly
agree with those obtained by Dr. Lister,* so far as they go.
This is particularly gratifying, as the mode of investigation
adopted by me is very different from that followed by this
distinguished anatomist ; and, moreover, Perophora is one of
the Social, while the species used by me are all simple Asci-
dians.

I have relied almost entirely on dissection, aided by the ac-
cumulation of blood-corpuscles in the various parts of the
system. In this way the minutest ramifications can be traced
with the greatest precision. A vast number of specimens,
however, are required ; for many individuals may be cut up
before one is met with in a proper state. Large specimens,
too, are necessary ; and they must have the tissues sufficiently
transparent, and the blood-globules opaque or coloured ; in
such only can the blood-channels be distinctly traced. And
when the specimens are even in the best condition, many may
be opened before the blood-globules are found lodged in the
part of the system requiring elucidation. This method is
consequently very laborious ; but the results are satisfactory ;
for in such natural injections there is very little danger of
being deceived by the blood being extravasated from its natural
channels.

A«rt'tli« iiinitida and A. cenoxa (fig. 4) are good species for
this purpose ; but the one that appears the best-adapted to
this mode of investigation is an undescribed species \_A. plan a
Hanc.] closely allied to the former. In this the blood-globules

* Philosophical Transactions/ 1834, p. 375.

3

BRITISH TUNIC ATA.

are of a brownish colour and very numerous ; so that it some-
times happens that in this animal large portions of the blood-
system can be traced in a single individual. Most of the
information on this portion of the anatomy has been obtained
from these three species ; but nevertheless several important
points have been verified in the living animal.

The blood-system in the simple Tunicates may be looked
upon as closed, however limited the true vascular portion
of it may be. The blood-channels throughout the organism

FKI. 4. — Blood, lacunae (curved) and muscular bands (straight) between the
mantle and lining- membrane of Ascidia venosa. Highly magnified.
«. Blood globules, much more highly magnified, of a reddish-yellow
colour and containing a few granules.

are well denned ; but whether or not they are provided with
proper walls, and, if so, to what extent, is not easy to determine.
The trunk channels leading to and from the heart have cer-
tainly all the appearance of being true vessels ; and the
branchial network lias likewise the character of being truly
vascular. The blood-channels in the test have also distinct
walls ; but in this case they are apparently composed of a
prolongation of the mantle or inner tunic. Traces, however,
of an inner vessel may be observed in the main trunks ; but
this apparent vessel may be nothing more than a continuation

ANATOMY AND PHYSIOLOGY. 35

of the lining membrane or " inner tunic " of Huxley. In fact,
the so-called vascular ramifications of the test, however minute
and divided, ought perhaps to be regarded as prolongations of
the pallial cavity, although it is quite possible that they carry
true vessels ; and, indeed, from the way they are connected
with the heart, this would seem almost probable.

The heart (Plate III, fig. 4) is tubular, and is of consider-
able leno-th. In Ascidia it is attached to the lower border of

O

the stomach, one end extending some way up the dorsal region
towards the intestinal tube ; this may be called the dorsal
extremity ; the other, the ventral end, points in the direction
of the oesophagus. It lies between the mantle and the lining*
membrane, within a distinct chamber or pericardium, along
one side of which it is attached from end to end. The chamber
seems as if formed by a fold of the lining membrane ; and the
heart is probably coated with it in the manner of a peritoneum,
and is so attached to the wall of the chamber.

A large trunk vessel passes from the dorsal extremity of the
heart, and immediately divides into three branches, one of
which advances between the mantle and the lining membrane
along the dorsal region at the back of the endostyle ; another
passes in the opposite direction down the dorsal margin to the
bottom of the branchial sac. These two form the great dorsal
branchial channel, and are equivalent to the ventral or thoracic
sinus of Milne-Edwards ; and they both communicate with
the dorsal extremities of the transverse channels of the bran-
chial sac. The third branch turns off at right angles to this
great dorsal channel, close to the point where it is united to
the heart, and, in company with another vessel, to be shortly
described, penetrates the mantle and goes to ramify in the
test.

From the other or ventral extremity of the heart there are
two large trunk vessels given off, one to each side of the
stomach. These ramify over the digestive organs and supply
a minute network spread over both sides of the visceral mass ;
this network may be termed the visceral plexus. It is in direct
communication with a similar plexus of blood-channels or
sinuses that lies between the mantle and the lining membrane
of the right side ; and this latter is continuous with another
plexus similarly situated in the left side of the mantle ; these
together form what we shall call the pallial plexus. The trunk
branch that supplies the left side of the stomach and the
portion of the visceral plexus there situated divides into two
large stems, one of which inclines towards the intestine, the
other towards the oesophagus ; the former passes for some

36 BRITISH TUNICATA.

little distance along the intestinal tube, and then, leaving- it,
penetrates the mantle in the dorsal region, and goes associated
with the third branch from the dorsal extremity of the heart,
already described, to ramify in the test. Thus originates the
double vessel that carries the nourishing fluid to and from
that envelope or tunic. The stem that goes towards the
oesophagus passes along by the side of the lower extremity of
the intestine, and, just before reaching the anus, turns aside
to join a large vessel that extends along the ventral margin
from one end to the other of the branchial sac (PI. Ill, figs.
2 and 3). This, which is the great ventral branchial channel,
is the dorsal sinus of Milne-Edwards. It communicates with
the ventral extremities of the transverse branchial channels ;
and its lower extremity bifurcates, a branch passing on each
side of the mantle.

The two great branchial channels, the dorsal and ventral,
communicate with each other, as we have already seen, by
the numerous transverse channels of the branchial sac ; they
likewise intercommunicate above through a sufficiently obvious
channel that encircles the entrance of the sac, immediately
above the vascular network, and just below the anterior cord,
afterwards described ; the lower extremities also appear to
communicate with each other by a much-constricted channel.
Thus the circle of the blood-apparatus would seem at first
sight to be complete; and as the opposite ends of the heart
operate upon the two great branchial channels respectively,
and as the blood oscillates first in one direction and then in
the other, we might look upon the mechanism as sufficiently
perfect for all the purposes of the circulation.

But something is still wanting, as is evident when we refer
to the fact that the influence of the heart is chiefly confined
to the branchial organ, the visceral plexus, and the vascular
system of the test. The pallial plexus of the right side is
certainly in connexion, as we have seen, with the visceral
plexus of that side; but, so far as our examination extends,
the plexus of the left side of the mantle is connected with the
general system through the minute network of the pallial
plexus only. It is obvious that the blood-current would be
feeble in these parts, if the whole of the mechanism is now
before us. And, moreover, it would be most languid in the
left pallial plexus — in that very portion of the mantle, in
fact, that is most amply supplied with muscular fibres, and
which, being comparatively free, has undoubtedly the greatest
mobility. Indeed, unless some additional means exist to aid
the circulation, engorgement of the blood-channels must in-

ANATOMY AND PHYSIOLOGY. 37

evitably take place in the pallia! plexus when the heart pul-
sates in the direction of the viscera ; and when its action is
reversed, exhaustion would ensue in this portion of the system.

Now, though the branchial sac is attached to the walls of
the pallia! chamber in front and behind and along by the
dorsal margin, it is necessary that the lateral or reticulated
portions of the organ should be suspended, and in such a
manner as to leave a considerable space between the sac and
the pallia! walls. Consequently a number of suspenders are
provided, which,, while they retain the branchial sac in its
proper position, allow the required space. These suspenders
are in the form of cylindrical bands or ties, and are con-
tractile ; they pass from the transverse branchial channels
and from the great ventral channel to the walls of the pallia!
or respiratory chamber ; they are hollow or tubular, and are
the means of communication between these blood-channels
and the pallial plexus of both sides, and also Avith the visceral
plexus of the left side. Thus the blood-currents in every
part of the organism are brought under the influence of the
heart. One of the suspenders,, larger than the rest, connected
with the ventral branchial channel,, opens into a considerable
channel or sinus in the mantle in which the nervous ganglion
is placed; and the vessel which carries the blood from
the heart to the great branchial channel has also much
the character of a suspender.

There can be no doubt whatever of the fact that the
branchial suspenders are tubular, and that they carry the
blood, as above stated, from the branchial network to the vis-
ceral and pallial plexuses. I have seen in several instances
the channels in the suspenders gorged with blood-corpuscles,
as well as the channels connected with them in the pallial
and visceral plexuses, and the transverse channels of the gill-
sac ; and thus by such natural injections the fact has been
demonstrated over and over again. And, moreover, I have
witnessed blood-corpuscles pass through the channels in the
suspenders in young living individuals of Ascidia sordida.

When the heart acts in the direction of the dorsal ex-
tremity, the blood will at once be thrown into the dorsal
branchial channel, and will pass by the dorsal trunk of the
compound vessel into the test; all the transverse channels of
the branchial sac will be filled; and through the agency of
the suspending tubules or vessels the pallial plexuses of both
sides of the mantle, as well as the visceral plexus of the left
side, will be supplied in all directions ; while that portion of
the blood-current which is retained in the vascular reticu-

38 BRITISH TUNICATA.

lation of the branchia will be hurried into the great ventral
channel, and by this to the ventral extremity of the heart.
But before it reaches so far it will be joined by the streams
derived from the visceral plexuses of both sides of the body,
and in this way with that from the pallial plexus, chiefly, of
the right side. The greater portion of the blood from the
left side of the mantle will reach the heart by the ventral
branchial channel, having been brought hither by the sus-
penders. The blood thus returned will likewise have com-
mingled with it that which is drained from the vascular
system of the test by the ventral trunk of that system. It is
thus apparent that the blood which arrives at the heart in
this direction is only a partially aerated current.

When the action of the heart is turned in the opposite
direction, just the reverse of all this takes place. The blood-
current will now fill, in the first instance, the visceral plexuses
of both sides, then the right pallial plexus; at the same time
it will reach the great ventral channel of the branchial sac,
and through it the transverse branchial channels ; while
simultaneously the blood will be pushed into the left pallia]
plexus through the suspenders placed along the ventral
channel. The blood that now enters the vessels of the
branchial sac will be joined by numerous streamlets issuing
from the suspenders, and brought by them out of the visceral
and pallial plexuses, and will ultimately arrive in the great
dorsal channel, and so to the dorsal extremity of the heart, at
which point it will be mingled with the current from the test
brought by the dorsal branch of the compound vessel ramify-
ing in that tunic — the trunk, in fact, which in the first
instance carried the blood to the test. Here, then, as well as
in the former case, the current returned to the heart is only
in part aerated ; but the aeration is undoubtedly more com-
plete when the stream sets in this direction than in the other ;
for now the only uiiaerated portion is that from the test,
while in the first case the blood from the visceral and pallial
plexuses is likewise in a partially aerated condition.

The pulsations of the heart appear to vary considerably in
number even in the same individual; and the numbers of the
oscillations in the same direction seem never exactly to agree ;
neither is there any constancy as to whether the dorsal or the
ventral oscillation has the greater number. In a young indi-
vidual of Ascidia sordida, in which the movements of the
heart were carefully observed, the pulsations were counted
four times in each direction, and the following was the result.
On the first occasion there were 73 beats in the ventral direc-

ANATOMY AND PHYSIOLOGY. 39

ticm, 70 in the dorsal ; on the second, 64 ventral, 68 dorsal ;
on the third, 74 ventral, 88 dorsal ; and on the fourth, 63 ven-
tral, and 64 dorsal. It required 2£ minutes to accomplish the
beats during a single oscillation. In another individual of
the same species, considerably larger than the former, but
still quite immature, there were 138 pulsations in one direc-
tion, and 120 in the other. Two or three of the concluding
beats of each oscillation were not so vigorous as the rest ; and
when the action was about to change, a dead pause ensued of
about two seconds.

In Polyclinum aurantium the pulsations were found to be
112 in one direction and 115 in the other ; and on starting,
the beats were slow. They afterwards became rather rapid,
and before ceasing were again retarded : the action then
stopped for a second or two before recommencing in the oppo-
site direction. The pulsations in BotrijUoide* radiata are
nearly as numerous as they are in the last species. In one in-
dividual 102 beats were counted in the one direction, and 115
in the other.

The above account of the circulation will be found to agree
with Dr. Lister's description of it in Perophora, so far as it
was determined in that form ; but that excellent observer did
not detect the flow of the blood through the suspenders, al-
though " filaments " attaching the branchial sac to the mantle
are described and figured by him. Their function as blood-
carriers seems equally to have escaped detection by Van
Beneden, though he must have been aware of their existence
as bands or ties; for they were figured by Snvigny, who de-
scribed them as ligaments attaching the braiichia to the inner
tunic,* and they are well known to anatomists generally.
Van Beneden, however, discovered the necessity of a passage
for the blood-current from the " periintestinal cavity " to the
branchia to prevent engorgement when the pulsations of the
heart were continued for any length of time in one direction.
He therefore believed that the required communication was
effected through the agency of the " respiratory tentacles "t.

It will now, however, be of no avail to discuss the improba-
bility of such an opinion, since ample communications have
been demonstrated. But it may be remarked that these ten-
tacles are undoubtedly hollow, and that in each there is a
double channel, that the blood will assuredly pass up one of
them and down the other, and that it will oscillate in unison
* ' Memoires sur les Animaiix sans Vertebres/ pt. ii [p. 97, pi. vi, f. -i ; pi.
vii, f. 2].

t Op. cit. [on p. 31], p. 113.

40 BRITISH TUNICATA.

with the movements of the heart. In fact, Van Beneden states
that he has seen it do so. I have observed nothing to warrant
the belief that either of the channels is in immediate commu-
nication with the vascular network of the branchial sac. On
the contrary, they both seem to me to open into the pallial
plexus, which of course is continued into the wall of the in-
halant tube.

The blood-system does not appear to vary much in the
Tunicata ; though certainly I have not traced it in the other
genera so completely as in Ascidia, yet enough has been seen
to warrant the above assertion. The heart is very similar
throughout all the various forms examined ; but its position is
not by any means constant. In Corrlla paraUelogramma it is
placed on the anterior margin of the stomach, and in con-
nexion with the left side of the mantle or inner tunic, follow-
ing the removal, in this instance, of the visceral mass from
the right to the left side. In Ciona intestinal! s, in which
there is developed an abdominal chamber, it is doubled upon
itself, and lies in this chamber towards the dorsal margin and
between the stomach and the bottom of the branchial sac.
The heart in Styela is very long1, and narrower than usual ; in
this form it lies between the inner tunic and lining membrane
on the left, and a little way from the posterior extremity of
the mantle, following the curvature of, but at some little dis-
tance from, the alimentary tube. The posterior extremity
opens into the dorsal branchial channel a considerable way up
the endostyle ; the ventral extremity is attached to the
stomach, to either side of which it gives a branch in the usual
manner. In Pelonaia the heart is likewise in connexion with
the left side of the mantle, and in other respects resembles
the arrangement in Styela. And in Molgula it holds much
the same situation — but is placed between the reproductive
mass which is above it, and a hollow cylindrical body with
hard walls, the nature of which is not understood.

The branchial sac is usually more complicated than is gener-
ally supposed. Hitherto its mechanism has been spoken of in
this communication only so far as was necessary to the full
comprehension of the blood-system ; it is now time to say
something respecting its more minute structure. In all the
Tunicates there must- of necessity be present the two great
branchial or thoracic channels (the dorsal in connexion with
the endostyle, and the ventral at the opposite side of the
thorax), even when the branchial sac is only partially or not
at all developed ; and in every instance where a true gill is
present the transverse channels or primary vessels must also

ANATOMY AND PHYSIOLOGY. 41

exist. These latter may be considered the essential or ele-
mentary parts of the respiratory organ ; the minute details,
consisting1 of secondary vessels, are variable, even in very
closely allied species, and are not always present.

The simplest form of the organ that occurs in the genus
Ascidia is found in A. venosa (PI. X). In this species the
transverse or primary vessels, or channels, are placed at regu-
lar intervals, and scarcely vary at all in size ; and between
and opening into them at right angles are numerous small,
longitudinal, secondary vessels divided by elongated spaces
or stigmata ; so that the whole forms a reticulation of vessels
in which the transverse channels are large and distant, the
longitudinal ones small and numerous and divided only by
narrow open spaces. Or the structure may be described, for
convenience, as it frequently is, as a vascular membrane with
large transverse channels and minute longitudinal ones con-
necting the former, and divided by narrow elongated stigmata.
This is the true aerating surface of the gill; and were there
no additional appendages, the organ would appear to be com-
posed of numerous transverse series of short longitudinal ves-
sels and narrow openings divided by large transverse channels
or vessels ; it would appear to be, in fact, what it essentially is.
But on first inspection, with the aid of a low magnifying-
power, it seems to be formed of a comparatively coarse reticu-
lation of longitudinal and transverse vessels of nearly equal
size, crossing each other at right angles, and having four or
five narrow longitudinal openings or stigmata in each square
mesh, dividing as many minute vessels.

This appearance is produced by the existence of a number
of stout so-called longitudinal vessels or bars that extend from
one end to the other of the branchial sac, and project con-
siderably from the inner surface of the organ, to which thev
are attached only at the points where they cross the trans-
verse channels. Here they are supported upon short wide
pedicles through which they receive their supply of blood
from these channels; they are thus lifted some little distance
above the general surface of the gill. At these points the
longitudinal bars are a little enlarged, and have on their
upper margin a stout elongated papilla with the extremity
rounded. There is thus a papilla at the angles of each mesh ;
and they are all inclined towards the ventral side of the res-
piratory sac, and have on the upper surface, and in front, an
elongated disk which is apparently ciliated.

The walls of the longitudinal bars are comparatively thick ;
and hence these organs have a certain degree of rigidity. It

42 BRITISH TUNICATA.

is not very easy to determine of what use they are; but per-
haps their chief function is to protect the more delicate tissue
of the true aerating vascular surface ; Avhile the papillae will
conduce to the same end, and by the aid of their cilia prob-
ably sweep the sedimentary matters towards the oral lamina,
the water being- beat through the stigmata by the cilia that
fringe their borders. From the stiffness of the bars them-
selves it may be inferred that they will also give support to,
and keep stretched out, the vascular network of the sac.
They seem ill calculated, on account of the thickness of their
walls, to give much assistance in aerating the blood, and are
certainly unnecessary as part of the circulatory mechanism.

The blood, as we have already seen, is brought to and taken
from the aerating reticulation by the dorsal and ventral bran-
chial channels, and by numerous suspenders connecting it
with the visceral and pallial plexuses. We have also traced
the blood through the principal channels of the organ from
one side of it to the other. All, therefore, that remains to be
done is to follow the flow of the stream through the minute
portions of the structure.

The extremities of the heart, we have seen, do not open
into the ends of the two great branchial channels, but a con-
siderable way above their lower terminations. It is conse-
quently evident that the blood will move upwards in these
channels above the point where it enters, and downwards
below it; and when we consider the action of the current so
brought to the transverse channels, it is clear that the flow
will be in contrary directions in the small longitudinal or
secondary vessels above and below this point. Now, it has
been already stated that on the reversal of the action of the
heart there is a pause of a second or two, so that for this
period the currents cease to move and the fluid becomes
perfectly stagnant. On resuming its function, the first act
of the heart is to dilate ; consequently, the blood is drawn
towards it from the respiratory organ; and it follows, as a
matter of course, that the fluid in the secondary vessels above
the point just alluded to in the great branchial channels must
flow downwards, and in those below this point upwards. This
will be the case whether the blood is brought to the branchial
sac by the dorsal or the ventral channel. Such downward
and upward set of the blood-current in the secondary vessels
has actually been observed in Perophora by Dr. Lister, who
states that " the horizontal vessels were connected abo by
the smaller or vertical channels between the spiracles — the
set of the current in the latter being upwards for the two

ANATOMY AND PHYSIOLOGY.

43

lower rows, and downwards for the two upper rows/' If tin-
heart in the first instance threw the blood into, instead of
drawing it from, the gill, the reversal of this motion would
take place; namely, the flow in the secondary vessels above the
point indicated would be upwards, and downwards below it.

Such are the characters of the branchial sac as seen to
exist in A. venosn. The minute network, however, is not
continuous throughout the whole organ, but is interrupted in
such a manner as to show that it is composed of two lateral
lobes or lamina?. It is divided along the dorsal line by two
parallel folds of the lining membrane, which are separated
by a deep groove; the tissue at the base of each fold is
stiffened by a flattened rod of a somewhat rigid, opaque,
yellowish substance, which together form the endostyle, that
lies, as it were, in the bottom of the groove, along which the

FIG. 5.

FIG. 6.

FIGS. 5 AND 6. — Transverse sections of the endostyle of Ascidia mentula,
highly magnified. The shaded portion represents the dorsal blood-sinus,
the thick black line the endoderm. Fig. 5, before separation of the lips.
Fig. (3, after separation.

rods appear to be united (see PL III, fig. 5, and figs. 5 and 6
in text). The upper extremities of these folds diverge right
and left, and become continuous with the lower member of
what may be termed the anterior cord or collar — two narrow
folds also of the lining membrane that encircle the base of
the respiratory tube, a little above the anterior margin of the
branchial sac, and having the circular blood-channel, pre-
viously mentioned, immediately below them. The ventral
margin of the sac is furnished with a wide, longitudinal,
delicate, membranous fold, which apparently also orginates
in the lining membrane, and which interrupts the continuity
of the minute network in this direction. This is the ventral
or oral lamina (PI. XIX) ; it extends from end to end of the
branchial sac, and is ribbed transversely; the margin is entire.
The mouth opens close by its left side, about one-third from
the lower extremity : the upper extremity for some little way
downwards is divided longitudinally, showing that the lamina

44 BRITISH TUNICATA.

is really composed of two lateral membranes; and each
division is united to the lower member of the anterior collar,
much in the same manner as the latter is attached to the
dorsal folds connected with the endostyle. The upper
member of this collar is divided from the lower by a narrow
groove, and is uninterrupted by either the oral lamina or the
dorsal folds. The oral lamina is connected below by another
narrow cord to the posterior extremity of the dorsal folds :
this is the posterior cord.

In this way are traced the boundaries of the two lateral
laminae composing the branchial sac. They are attached by
their upper borders to the walls of the pallial or respiratory
chamber a little below the anterior collar or cord ; the dorsal
margins are attached along the sides of the endostyle, and
the lower margins along the line of the posterior cord. In
all other parts the two lobes are free, except at the points
where the suspenders bind them to the walls of the chamber,
and where the extremity of the oesophagus penetrates the
branchial sac ; and here, of course, the latter is attached to
the alimentary tube. The supposed function of the endostyle
has been already indicated; the folds of the lining membrane
to which it is adherent are no part of the gill : neither can
the oral lamina be considered a portion of the breathing-
organ: it is certainly highly vascular; that is, minutely rami-
fying blood-channels can be traced in it : but similar vessels
(or channels) are seen in all the membranes of the organism,
and also occur in the dorsal folds in connexion with the endo-
style. The office of the oral lamina is to conduct the food to
the mouth. And it has already been stated that the sedi-
mentary matters are there accumulated and formed into a
cord, and so carried to the oral aperture along the lamina.
The anterior cord may perhaps also aid in collecting sedi-
mentary aliment, if it be ciliated, as its homologue in Sal pa
is stated by Professor Huxley* to be.

The simple form of gill above described is not by any means
constant in Ascidia ; in fact, it seems but rarely to occur in
this genus. The same simplicity of structure, however, is
found in Pelonaia, with only some unimportant changes. In
Clarelina and PeropJiom the vascular network is not more
complicated ; and in the former, at least, the longitudinal bars
have entirely disappeared. And in it there are numerous
transverse laminae which are adherent throughout to the Avails
of the transverse channels; they are united to the filaments of
* " Observations \ipon the Anatomy and Physiology of Salpa and Pyro-
soma," ' Phil. Trans.,' 1851, pt. 2, p. 567.

ANATOMY AND PHYSIOLOGY. 45

the oral lamina, and perhaps are mainly instrumental in carry-
ing1 the food in that direction. The structure of the gill is
equally simple in the compound Tunicates ; and in them the
longitudinal bars seem to be occasionally present.

In Ascidia mentula and A. sordida the branchial network is
fundamentally the same as in A. venosa ; but in the two for-
mer, and in some others [J. scabm and A. affin!*, &c.], it is
minutely folded longitudinally, so that, on making' a trans-
verse section of it, the edge presents a deeply undulated line.
The surface is not altogether unlike corduroy ; it is, in fact,
finely plaited (or crimped, as the laundress might say) ; but
the flutes or grooves between the ridges or plaits are inter-
rupted wherever the transverse vessels cross them, the vessels
at these points filling up the hollows. Thus there are
numerous septa formed, turning the grooves into series of
minute recesses or pouches.

The longitudinal bars are strong and raised considerably
above the inner surface in A. mentula; and there are smaller
intermediate papillae, as well as larger ones at the points
where the bars cross the transverse vessels.. All the papilla?
bear ciliated disks : and a wide membrane stretches from the
back of the larger papillas for a considerable way along the
transverse vessels. In A. sordida the bars are likewise
strong ; but the papillte are rather small, and there are no
intermediate ones. Between the longitudinal bars there are
two oval ciliated disks, one on either side of the middle line
of the transverse vessels.

The oral lamina in A. sordida is a wide plain membrane;
but in A. mentnla it is strongly ribbed transversely, and the
ribs, passing beyond the margin as fine points, give to it a
pectinated appearance.

In Sfyela tuberosa and its immediate allies we have another
modification of the branchial network. In them it is provided
with eight simple longitudinal folds or lammas — four on each
side of the oral lamina; these stretch from one end of the sac
to the other, and terminate below by the sides of the oral ori-
fice. The network is, in other respects, as simple as it is in
A. venosa, there being no minute plaiting such as is seen to exist
in A. mentnla. The folds, however, give to it a vei-y interest-
ing character, inasmuch as we observe in them a very ready
and efficient mode of increasing the aerating surface, as, indeed,
the same end is gained by the minute plaits in the vascular
network in A. meufubi and A. sordida. In Sti/da the folds
are formed in exactly the saine way as those minute plaits;
that is, they are each composed of a fold of the branchial sac,

46 BRITISH TUNICATA.

and the space within is divided into pouches by septa situated
at nearly equidistant points. In this genus the transverse
vessels vary considerably in size, there being- usually one or
two smaller between the larger ones ; and the septa are placed
wherever the latter cross the structure. Thus a series of
pouches of nearly equal size occupy the interior of the folds,
and open at the outer surface of the branchial sac into every
part of the atrium. In fact, we see here an arrangement very
similar to that observed in the interbranchial water-channels
in the Laniellibranchs ; and in this case, as in them, the pur-
pose is to allow the water, after permeating the walls of the
fold or lamina, to escape externally.

The longitudinal bars in Btyela assume the form of delicate
ribbon-like membranes attached by one edge to the principal
transverse vessels; they are numerous, and are found on the
folds as well as on every other part of the organ. The oral
lamina is a wide simple membrane.

The branchial sac in Mongula conchilega and its allies is
characterized by longitudinal folds or laminae, formed much
in the same way as those in Stt/ela. In the former there are
six such folds on each side of the sac. The vascular network,
however, is very different, having the secondary vessels, or
those which are usually arranged at right angles to the trans-
verse channels, disposed in imperfect spiral coils or convolu-
tions, the vessels themselves frequently intercommunicating ;
consequently the stigmata or open spaces separating them are
broken into various lengths. There are also a few delicate
radiating vessels which pass from the centre of the coils to
the circumference, but mostly in the direction of the trans-
verse channels that convey the blood to and from the coils.
The chief purpose of these radiating vessels is apparently to
prevent engorgement of the coil, and to aid the reflux of the
stream by conveying the blood in the most direct manner to
and from the centre of the coil. When the spiral arrange-
ment is more imperfectly developed than usual, the radiating
vessels are very irregularly dispersed ; but even in such cases
there can be little doubt that their function is as above stated.
The longitudinal bars have the ribbon-like character of those
in fttyela, and are principally confined to the folds.

Corella parallelogr&mma has also the secondary vessels
spirally arranged, as originally pointed out by Mr. Alder* ;
and here the coils, which form slight conical eminences,t are

* "Observations on the British Tiinicata," 'Ann. Nat. Hist.,' ser. 3, xi,
p. 158.

f [Op. cit., pi. vii.]

ANATOMY AND PHYSIOLOGV. 47

disposed in regular traiisverse series between the transverse
channels. The coiled vessels do not so frequently intercom-
municate as they do \nMolgida; consequently the stigmata
are much longer, being less interrupted. The radiating
vessels are not numerous, and they pass from the centre of.
the coil to the transverse channels. The longitudinal bars are
more rigid and cord-like than usual ; they project considerably
from the surface of the gill ; and the papillfe which are at-
tached to them are not elevated, but inclining backwards are
united throughout their length, and give support to wide
membranes that extend from the surface of the transverse
vessels. In this species the oral lamina is replaced by a series
of well-developed filamentous processes.

The most perfect, however, of the spiral type of gill is found
in Molgula areiiosa. In this interesting species the interior of
the branchial sac is furnished 011 each side with six or seven
wide, longitudinal, ribbon-like bands, which are attached by

FIG. 7. — Tentacles of Ascidia Alderi. Highly magnified.

one edge to the ti-ansverse vessels at the points where they
cross them. These bands, how like soever in general appear-
ance, are not to be confounded with the branchial folds in
Stye-la and Molrjula ; they are the homologues of the longitu-
dinal bars so constantly present, and with the transverse
vessels give to the surface a coarse reticulation, the square
meshes of which are each occupied by a conical eminence. On
account of the prominence of the longitudinal bands these
eminences, which look like so many miniature beehives, seem
to be arranged in six or seven longitudinal series. Each cone
is formed of a double spiral coil of secondary vessels united at
the apex ; the coils are .perfect, and the stigmata, which are
coextensive with them, appear to be scarcely, if at all, inter-
rupted by intervascular communications. Radiating vessels,
however, which are sufficiently numerous to prevent engorge-
ment, pass from the apex of each cone to the transverse
vessels, and are the principal interruptions to the con-
tinuity of the spiral stigmata. The oral lamina in this, as in all
the members of the genus, is a plain simple membranous band.

48

BRITISH TUN1CATA.

All the simple Ascidians that have come under my notice,
not even excepting Pelonaia, have a collar of tentacular fila-
ments situated at the base of the incurrent tube, some distance
above the entrance of the branchial sac (PI. Ill, and figs. 7-9
in text) ; indeed the distance in some species is considerable,

FIG. 8. — Tentacles of dona fascicularis. Highly magnified.

and no instance has occurred in which they could be said to
be connected with the gill. They are usually linear or slightly
conical, and are rather numerous, except in Pelonn.ia, which
has not more than twelve or fourteen ; but in Mniynla and in
some of the other Cynthiadse they are branched or pinnate,

A

•- ' • '

. 9. — A tentacle of Cynthia echinafa. Highly magnified.

and are not very abundant. They, however, all agree in
being soft, delicate, hollow organs; and the simple ones, at
least, have the interior divided by a septum into two
longitudinal channels, so that the blood will circulate freely
through them [as seen in fig. 7] . They appear to be an out-
growth of the lining membrane, and are supplied with blood

ANATOMY AND PHYSIOLOGY. 49

from that \vhich flows between it and the mantle or inner
tunic .

THE BRANCHIAL TUBERCLE AND NERVOUS SYSTKM.

That enigmatical organ the branchial tubercle (the anterior
tubercle of Savigny) (PI. XX) is situated in the space between
the tentacular filaments and the anterior margin of the bran-
chial sac, in contact with the upper membrane of the anterior
cord or collar, and immediately in front of the upper ex-
tremity of the oral or ventral lamina. It is formed of two
parallel folds of the lining membrane pressed close together
and united at the extremities ; they seem but as one fold, and
are bent into a loop Avith the ends turned towards the inhalant
orifice, and, inclining inwards, are a little convoluted. Thus
the organ assumes a rounded or oval form, rising above the
surface to which it is attached as a depressed compact tuber-
cular swelling. An opaque white line marks the separation
of the two folds, and follows the convolutions to the extremities.

This is the form that this curious tubercle assumes in Asclilin
scabm, A. affinis, a closely allied species, A. mentula, and
Pelanaia corruguta. In A. sordida one of the extremities
turns inward, the other outward, so that both are bent in the
same direction. But more striking modifications occur in
some other species. In one allied to A. mentula there are
three loops, crowded upon each other, and having their ex-
tremities only slightly incurved ; and in another closely related
form the organ is dense, large, and somewhat quadrangular,
with numerous irregular convolutions formed apparently of
several loops of the lining membrane. In Styela tulerosa and
$. mamillaris it is large, oval, and disk-like, with the ex-
tremities so indistinct as to be scarcely traceable. The reverse
of this is the case in Molgula conehilega, in which it is almost
crescent-formed, with the extremities very obvious and well
turned inwards. And in Ascidia venosa it is still more simpli-
fied, being a mere horseshoe-like loop, with the extremities
pointed and very slightly incurved.

It is not easy to assign a function to this peculiar organ—
though, from its position at the entrance to the branchial sac,
it may be inferred that it is of the nature of a special sense,
testing the quality of the inhaled water. Taste could be of
little use to an animal which has not the power of selecting
its food ; but it would seem necessary for the creature to be
warned of the approach of aught deleterious in the respira-
tory currents. The function of this organ is therefore prob-
ably more akin to that of smell than of taste. It is certainly

4

50

BRITISH TITNICATA.

of some importance in the economy of the animal; for it is
constantly pi*esent, and is usually closely associated with the
ganglion. In some species the tubercle rests upon the nervous
centre ; and when placed at a little distance from it, a nerve
may generally be traced running towards (and in some in-
stances having all the appearances of supplying) it.

The nervous system is in a very rudimentary condition in
the Tunicata. There is but one ganglion; and it is invariably
placed between the two respiratory tubes, in a blood-sinus
situated between the inner tunic and linine" membrane, which

O •*

FIG. 10. FIG. 11.

FIGS. 10 and 11. — The nerve-ganglion in Ascidia mentiila. Fig. 10, as seen
from the outside of the mantle. Fig. 11, as seen from the inside of the
mantle, a and 6 lead to incurrent tube, b sxibsequently dividing, and
one branch going to ventral side of txibe. c and d lead to mantle.
e, gland-like organ. Highly magnified.

sinus, communicating directly with the great ventral channel
of the branchial sac, will be well supplied with aerated blood.
The ganglion is fusiform, more or less elongated in the antero-
posterior direction, and usually a little constricted in the
middle, as if composed of two centres (figs. 10 and 11). In
A. mentula, and in several other species that have been ex-
amined, it is partially folded in a much folliculated gland-like
substance, and gives off from each extremity three or four
nerves, all of which go to the respiratory tubes and to the

ANATOMY AND PHYSIOLOGY. 51

adjacent portions of the inner tunic or mantle. A branch
from one of the principal nerves has been traced to the
branchial tubercle in one or two species. There is no varia-
tion of any consequence in the nervous element in any of the
forms examined.

SALPA AND ITS RELATIONSHIP WITH OTHER TONICATA.

The organisation of Salpa is highly instructive ; for in
this form we have a Tunicate in which development has
been arrested,, and which, to a certain extent, has an em-
bryonic character. In it the branchial sac is entirely absent,
and the circulatory system is in much the same condition as
it is in the young of Ascidia before the respiratory organ is
developed.

In Salpa the outer tunic or test appears to be quite free
from the inner tunic or mantle, except at the margins of the
anterior and posterior orifices, where they seem to be united.
The inner tunic and lining membrane, or that which forms
the inner wall of the respiratory cavity, are, on the contrary,
adherent throughout, spaces only being left for the passage
of the blood-currents ; for it is between this tunic and mem-
brane that the " sinus-system " is situated. The respiratory
cavity corresponds pretty accurately to the pallial chamber
of a simple Ascidian — were the branchial sac entirely re
moved, leaving only the endostyle with its two lateral folds,
the ventral or oral lamina, and the connecting cords.

On examining the great respiratory chamber or cavity in
Salpa spinosa, for instance, an endostyle with the two lateral
membranous folds, similar in all essentials to that organ in
the other Tunicata, is seen adhering to the dorsal wall of
the cavity; and the so-called "branchial band" or "gill'
is conspicuous on the opposite side, passing forward from the
nucleus in an inclined position, the posterior extremity being
attached in the vicinity of the mouth, the anterior to the
ventral wall of the cavity. The two folds in connexion with
the endostyle and the "branchial band" are connected in
front by a narrow band (the "ciliated band" of Huxley) that
encircles the anterior extremity of the respiratory cavity :
and another similar band, or pair of parallel bands, passes
from the posterior end of the dorsal folds and terminates
near to the posterior extremity of the " branchial band."
Thus we observe certain lines or bands which, together with
the endostyle, correspond to the boundary lines of attach-
ment of the branchial sac of a simple Ascidian; and if we

52 BRITISH TCJNICATA.

suppose a vascular network extended from either side of the
endostyle to the lateral margins of the "branchial band/'
and imagine it to be attached in front and behind along the
ciliated bands, we shall see how readily a Salpa may be made
to assume the most striking feature of an ordinary Ascidiaii.

Now the ciliated bands are the homologues of the pos-
terior cord and the lower member of the anterior cord or
collar of the branchial sac of the simple Ascidians ; and the
"branchial band" is the equivalent of the oral or ventral
lamina of the same group. The relation of the ciliated bands,
particularly the anterior, to the "branchial band," and the
characters of the latter, sufficiently prove this.

The so-called branchial band has the appearance of a cylin-
drical tube ; but it is easily seen that it is formed of two
laminas, the lower or ventral margins of which are a little
separated, while the upper or dorsal are brought together,
forming a ridge along this margin. A large blood-channel
runs along in connexion with, and immediately below, the
ventral margins ; this is the homologue of the ventral branchial
channel. The two lamina? rise, as it were, from the sides of
this channel, and inclining towards each other, are united along
the dorsal ridge as just stated; but towards the anterior ex-
tremity of the organ they separate, and become united to the
ends of the ciliated cord or band in exactly the same way as
the lateral divisions of the oral lamina join the anterior cord
or collar. In fact, in both Salpa and Ascidia the one organ
seems to be a continuation of the other, as they are, no doubt
in both, productions of the lining membrane, the blood-channel
itself being developed in connexion with the same membrane.
The "branchial band," we thus see, corresponds to the oral
lamina in being composed of two latninas, in its relation to the
anterior ciliated band or collar, and in its connexion with the
great ventral blood-channel. And, moreover, like the oral
lamina in several of the Ascidise, it is transversely ribbed. In
Sfil/ifi the ribs are stout and strongly ciliated ; and there can
be no doubt that they are also ciliated in Avidia.

In Salpa, then, the so-called branchial band cannot be
looked upon as a true gill; and homologically it does not
represent the branchial sac at all, but only that appendage of
it the oral lamina. And as the function of the latter seems to
be chiefly, if not exclusively, to carry the food to the mouth,
the same office is probably performed by the so-called gill in
Salpa. And, indeed, without some such help it is difficult to
see how such an animal would be able to take its food. There
can be little doubt that the walls of the respiratory cavity, as

ANATOMY AND PHYSIOLOGY. 53

has been suggested by Professor Huxley*, chiefly effect the
decarbonization of the blood ; while this so-called gill will aid
in this operation in proportion to its vascularity : as must,
indeed, all the tissues bathed by the respiratory currents.

The ganglion lies on the ventral side of the respiratory
cavity, between the lining membrane and inner tunic, a little
in advance of the ciliated band, and directly in front of the
anterior extremity of what we may now term the oral lamina
(the pseudo-gill). All the nei'ves are given to the walls of
the cavity — in other words, to the inner tunic or mantle. The
anterior extremity of the ganglion is produced a little, giving
an appearance to the organ as if composed of two centres.
On the anterior surface of the produced extremity there are
three or four imperfectly formed black pigment specks, having
the appearance of rudimentary eyes, which, however, Professor
Huxley considers to be auditory capsules.

The " languet," Avith its ciliated " fossa," is placed just in
front of the ganglion, consequently on the same middle ventral
line with it and the oral lamina; it is a long, tapering, conical
process, with a longitudinal groove which widens at the base
where it joins the fossa, over which it seems to straddle.
There can scarcely be any doubt that this is an organ of
special sense ; and it would appear probable that its office is
to ascertain the quality of the respiratory currents, and may
therefore be olfactory. Thus in function the " languet " would
seem to agree with the branchial tubercle so constant in the
other Tunicates [with the apparent exception of Ascidia
mamillata, in which it is inconspicuous] • but it is, moreover,
homologically speaking, the same organ, as appears demon-
strated by its position in relation to the ganglion, the ciliated
band, and the pseudo-gill. Like the tubercle, too, it is a pro-
duction of the lining membrane; and, as indicated by the
longitudinal groove, like it, also,, the "languet" is probably
formed of tAvo portions or folds of this membrane. It must,
therefore, not be confounded, as it frequently has been, Avith
the tentacular filaments of the oral lamina in Clavelina, Pyro-
soma, and se\reral other simple and compound Ascidians.

The homologies, however, do not stop here ; the clear anas-
tomosing vessels or tubes ramifying over the surface of the
intestine, described and figured by Prof. Huxley,t and sup-
posed to " represent a hepatic organ," or "a sort of rudimen-
tary lacteal system," are, there can be no doubt, the homologue
of the rudimentary liver before described in Ascidia and in

* "Anatomy and Physiology of Salpa and Pyrosoma/' 'Phil. Trans./
1851, pt, 2, p. 570. f Loc. cit.

54 BRITISH TUNICATA.

some of the Cynthiada? ; and, indeed, the structure appears to
resemble very closely thnt of the 'hepatic organ in Corella
parallelogramma. The "mass of clear cells," the " elseoblast"
of Krohn, according to Huxley, may perhaps prove to be the
same as the well-known cell-structure before described as
coating the alimentary tube in the Aftcidite ; but this is mere
conjecture.

Thus we see how close the relationship is between Salpa
and Ascidia ; with ClaveUna, however, the connexion is still
more intimate. This is undoubtedly a near ally ; it is only
necessary to look to immature specimens to be satisfied of
this. When the young ClaveUna is about one twentieth of an
inch long, and when the thoracic portion would scarcely be
half that length, the thorax is remarkably like the embryo of
Sal pa. In profile both have a sub triangular form, the anterior
opening* being placed at the angle in front, and the posterior
at an angle situated considerably backward, the young of
ClaveUna having the two orifices nenrly as far apart as they
are in the embryo of Sal pa. At this early period of growth
the endostyle is distinctly developed in both forms, and the
ganglion and the oral lamina are clearly indicated, also the
ciliated band or anterior collar. So far, everything is alike;
the general similarity of the respiratory cavity is obvious
enough; and were the nucleus in Sal pa produced a little more
than it is backwards, the resemblance of the two would be
almost complete. But in the young of ClaveUna there are, in
addition to what has already been described, the tentacular fila-
ments of the incurrent tube, which are now of considerable size ;
and the branchial sac has already commenced its development.

The latter organ, however, is in an exceedingly rudimentary
condition : only a single transverse channel or primary vessel
on each side of the great ventral channel has made its appear-
ance, and does not yet extend much more than halfway across
the thoracic or respiratory cavity, on its way (so to speak) to
the dorsal channel in connexion with the endostyle. On each
side of these growing primary vessels five or six secondary
vessels, at right angles to them, have commenced to sprout ;
and the distal extremities of all of them, as well as of the
primary vessels themselves, open through the lining membrane
of the thoracic cavity into the sinus-system between it and the
inner tunic. Thus is defined, on either side, the nascent
atrium, which is only an extension of the cloaca that had been
previously formed. Shortly another primary vessel makes its
appearance, extending from the ventral channel and connected
laterally with the extremities of the secondary vessels already

ANATOMY AND PHYSIOLOGY. 55

formed; and then another series of secondary vessels is
developed,, and afterwards another primary vessel, and so on,
gradually increasing the length of the two branchial leaflets
(if they may be so called), which at the same time grow in
breadth, passing further and further across the thoracic cavity
until at length they reach the sides of the endostyle ; all the
Avhile the primary and secondary vessels along the margins of
the growing organ, open into the pallial sinuses in the manner
already indicated ; so that the boundary of the water-space or
atrium is well defined, and is always coextensive with the
expanding gill. The oral processes, which in this animal
occupy the place of the lamina, are produced one by one, in
accordance with the appearance of the primary vessels ; and
the vascular suspenders likewise originate at the same time.

It is unnecessary on this occasion to trace the development
of the branchial sac further, or with more minute details ; it
should be observed, however, that the growth of the gill un-
doubtedly originates in the great ventral channel, which is itself
a production of the lining membrane, and that during the
development of the organ it is connected with this membrane,
and that this connexion is ever afterwards maintained by the
vascular suspenders. It may also be remarked that in no
stage of the growth is the gill ever connected, on the one
hand, with the margin of the oral orifice — or, on the other,
with the tentacular filaments of the incurrent tube, which are,
indeed, placed at a considerable distance from the upper mar-
gin of the gill ; and the lower margin is some way above the
oral orifice.

The above description of the development of the gill does
not exactly agree with that given by A. Krohn of the branchial
sac of Phallusia (Ascidia) mamillata*. According to this
author, there are at a very early stage of development two
excurrent orifices, one on each side of the middle line, — neces-
sitated by the fact that the gill commences to separate itself
from the walls of the cavity at two points simultaneously, thus
forming two separate water-spaces, one on each side of this
line, — the great ventral blood-channel apparently not being
yet detached from the inner tunic. It is not till the " branchial
sac is everywhere perforated " that these water-spaces, accord-
ing to this naturalist, are united by the formation of the
cloaca. I have certainly not seen the young of Clavetina in a
sufficiently early stage of development to warrant the asser-
tion that such does not take place in this form ; but assuredly

* "On the Development of the Ascidians," by A. Krohn, 'Scientific
Memoirs/ edited by Henfrey and Huxley, 1853, p. 324.

56 BRITISH TUNICATA.

in it, ai a very early period, the cloaca freely communicates
with the water-space or atrium on each side. At the same
time it must be allowed that it is more than probable that, at
the earliest stage of existence, in Clarelina and in other Tuni-
cates the great ventral channel is united throughout to the
wall of the pallial chamber; and hence the statement of
Krohn does not seem at all unlikely. And, moreover, we
thus learn that this great blood-channel is developed in con-
nexion with the lining membrane, with which it continues
ever afterwards more or less connected. We have already
seen that the transverse or primary vessels take their origin
in this same vessel, and that they in their turn give oft' the
secondary vessels : these are the essential parts of the bran-
chial tissue, and when we look to its anatomical structure as
well as to its mode of growth, we can scarcely doubt that the
network of the gill is truly vascular. Speaking, therefore, of
the branchial sac as a perforated membrane, as is frequently
done, gives an erroneous idea of its apparently true nature.

The longitudinal bars which have been so frequently
alluded to, and which lie in a plane a little above the inner
surface of the respiratory sac, are non-essential parts of the
organ, their function apparently being, as previously stated,
to protect the surface of the gill, and, by the aid of their
cilia, to sweep the alimentary matters towards the oral
lamina. They are not always developed ; they do not exist
in Clctveliiia- neither are they apparently present in P<-n>-
phora • and they seem to be absent in several of the com-
pound Ascidians; in DnUolum they have likewise disappeared.

It is stated above, that ChiveUna is nearly related to Salpa;
but Pyroso-iita and Doliolum come much nearer to it in their
general structure, as well as in the details of their organisa-
tion. Unfortunately I have never seen either of these two
interesting forms • but, judging from the able descriptions of
them by Prof. Huxley in the ' Philosophical Transactions/
they both present examples of imperfectly-developed gills.
In Pyrosoma the secondary vessels are entirely absent, and
the primary vessels of the two lateral laminas of the branchial
sac do not reach the endostyle, their development having been
arrested before they extended so far across the respiratory
cavity ; their distal extremities, however, will undoubtedly
open into the system of pallial sinuses ; in no other way can
the flow of the blood through the gill be explained : the cir-
culation is therefore to this extent embryonic. " The longi-
tudinal bars " of Huxley are the homologues of what have
been so designated throughout this communication, and are

ANATOMY AND PHYSIOLOGY. 57

therefore not to be confounded with the true vascular portion
of the gill. To turn . Pyrosoma into a Kalpa, little more
seems necessary than to arrest entirely the growth of the
primary branchial vessels, and to give to each individual a
separate test.

An arrest of development of these vessels is carried to a
much greater extent in Duliolum. In this form the secondary
vessels have not only disappeared, but the longitudinal bars
are also absent, and the primary vessels themselves only very
imperfectly developed. The two bands named by Huxley
respectively the " epipharyngeal " and " hypopharyngeal " in
this curious form, undoubtedly indicate the line of the great
ventral channel and oral lamina, bent up in accordance with
the peculiar development of the creature. In the Ascidl&
that have the branchial sac prolonged behind the mouth,
the ventral channel extends likewise behind the mouth, as
well as in front of it; and if we suppose the endostyle to
be shortened in these species, and the posterior portion of
the sac to be consequently drawn backward and upward, the
corresponding extremity of the ventral channel would pass
up the dorsal side of the pallia! or branchial chamber; and
thus this axis of the gill would at once take up the position
it occupies in Doliohtm : that is, part would be above or in
front, and part below or behind the mouth; part would form a
"hypopharyngeal" band, and part an "epipharyngeal" band.

Now the primary vessels or "tubular bars" originate in
the sides of these bands, and are, as already stated, very im-
perfectly developed, extending, as they do, only for a short
distance, and then terminating by opening through the lining
membrane of the respiratory cavity into the pallial sinuses,
just as we have supposed the similar vessels to do in Pi/ro-
fioma. The vessels or "bars/"' however, of the middle portion
of the gill, according to Prof. Huxley, do not so terminate,
but end in free loops. The branchial sac is, indeed, in such
a rudimentary condition that one step more in its degrada-
tion and it would entirely disappear, and Doliohtm would be
scarcely distinguishable from Salpa.

In Appe iidini lari a the gill is wholly absent; but the oral
lamina is represented by the " ciliated band/' which adheres
to the ventral surface of the respiratory cavity; and it is
interesting to find that the anterior extremity of this band
divides into two branches, which, passing towards the dorsal
region., encircle the cavity a little below the ganglion, just as
the anterior ciliated band does in Salpa, and as the anterior
band or collar does in Ascidia.

58 BRITISH TTJNICATA.

In this interesting form,, in which the embryonic characters
have become permanent, we see the oral lamina still adhering
to the wall of the respiratory cavity, as well as the eiidostyle
and anterior collar or ciliated band. All these parts, then,
appear to be equally developments of the lining membrane ;
and the gill, which in the higher forms has been described
to originate in the oral band, or rather in the great ventral
channel, which always accompanies it, must likewise be con-
sidered a production of this same membrane, with which, too,
we have seen that it is connected throughout its development.

THE RELATIONSHIP OF THE TUNICATA WITH THE POLYZOA AND

LAMELLIBRANCHIATA.

It is not my intention, on the present occasion, to enter at
any length on the relation that subsists between the Tunicata
and the Polyzoa on the one hand, and the Tunicata and the
Lamellibranchiata on the other. Nevertheless it seems de-
sirable to say a few words on this important branch of the
subject before concluding, with the view merely of indicating
what appears to be the result, in this respect, of my recent
investigations.

That the Polyzoa are very closely allied to the Tunicata is
now generally admitted ; opinion, however, is divided respect-
ing the homology of the tentacular crown — some naturalists
maintaining that it is represented by the branchial sac, while
others believe that it is homologous with the tentacles of the
respiratory tube, and that the branchial sac is really the
dilated pharynx of the polyzoon. These two views have been
ably advocated respectively by Prof. Allman and Prof.
Huxley.

In my paper on the " Freshwater Bryozoa/' before cited,
the opinion that the branchial sac is homologous with the ten-
tacular crown was maintained ; but my belief in this view has
been of late much shaken, and even Prof. Allman's ingenious
explanation of his theory seems to me 110 longer satisfactory.
The peculiar idea entertained by this able physiologist is, that
the lophophore of a Hippocrepian Polyzoon is the homologue
of the ventral branchial channel of the Ascidian, and that the
tentacles of the former correspond to the transverse or primary
vessels of the branchial sac. But the lophophore is an appen-
dage of the mouth, and is developed from the margin of the
oral orifice, and therefore can scarcely be considered to be
the true representative of the branchial channel, which does

ANATOMY AND PHYSIOLOGY. 59

not seem to be so related, but appears rather to be developed
in connexion with the lining membrane coating the pallial
cavity, and has all the appearance of a true vessel in direct
communication with the heart. And there are other difficul-
ties in the details of this view, to which it is unnecessary, at
this moment, to make further allusion.

The view so forcibly advocated by Prof. Huxley seems to
rest more upon a wide and philosophical generalization of
Molluscan organization than on anatomical and embryological
data, and is therefore difficult to discuss from a standpoint of
the details of such matters. It must, however, be stated that
the anatomical facts, so far as I have been able to examine
them, do not seem to contradict this hypothetical view ;
indeed, in many respects, they appear rather to support it.
The anatomical data, nevertheless, will, I think, bear another
interpretation, which, perhaps, it will be well to consider,
merely premising that I have no wish to support it further
than as a suggestion which has a few corroborative facts in its
favour : more information is still required before this matter
can be determined satisfactorily. The interpretation alluded
to is, that the branchial sac is a new and distinct develop-
ment, as the endostyle is, and as are the oral lamina, the
branchial tubercle, and the tentacular filaments of the inhalant
tube, — and that all these organs have equally their origin in
the lining membrane or inner tunic of Huxley, and have no
homological representatives in the Polyzoa.

And, further, this interpretation Of the facts leads to a belief
that the branchial sac is the rudiment of the Lamellibranchiate
gill, the structure of the two organs being essentially the
same. The principal blood-channels in the gills of the
Lamellibranch are simple transverse vessels ; and the most
persistent and essential parts in the structure of the branchial
sac of the Tunicates are the transverse or primary vessels.
Thus, fundamentally, these organs are similar. And when
the branchial sac is furnished with longitudinal folds, as
generally is the case in the Cynthiada?, the primary vessels as-
sume relatively the same position as their supposed homologues
do in the gill-plate. The folds, too, as the nature of the structure
implies, are formed of two laminte united at their distal mar-
gins, and have the space between them divided by septa into
transverse pouches, which only want to be elongated by the
further development of the fold to make them correspond in
every respect to the interbranchial water-tubes of the gill-
plate of the Lamellibranch. And already the pouches sub-
serve the function of water-tubes.

60 BRITISH TUNICATA.

Now we have seen that the branchial sac is composed of two
lateral lamina?, originating in the great ventral channel, and
extending to the endostyle ; and in Pyrusoma and Doliolum
we observe that these laminae are curtailed in their develop-
ment before they reach so far ; in the latter, in fact, they are
exceedingly limited. There is, therefore, no difficulty in sup-
posing that the branchial sac might be reduced to merely four
such folds as above alluded to, two being on each side of the
mouth and oral lamina. Were such the fact, there would be
four rows of orifices, corresponding to the pouches in the folds
on the outside of the gill, opening into the cloaca, exactly like
the four rows of openings of the interbranchial water-tubes
communicating with the anal chamber in the Lamellibranchs.
Thus, in all external characters, we should have here a very
complete representation of the four gill-plates of that group.
Each pair of the gill-plates, however, in the Lamellibranchiata
has its own proper efferent blood-vessel leading directly to the
heart; while our supposed transformed organ has only one
such trunk vessel. It would therefore seem probable that the
branchial sac can represent but a single gill of the Lamelli-
branch, and that one fold 011 each side of the ventral lamina
(or great ventral channel) may be assumed to be the homo-
logue of the left gill of the higher mollusk.

The branchial sac itself is not a perfectly symmetrical
organ; at least the oral lamina does not exactly divide it
into two equal lateral halves ; for it invariably passes to the
right of the oral aperture in all dextral species, and it never,
so far as my observations extend, abuts directly upon it. On
the other hand, the heart in the simple Ascidians usually
occupies a central position, being placed in the middle line of
the digestive organs; and the great vascular trunks, as they
leave its anterior or ventral extremity, exhibit a symmetrical
bilateral development, a trunk going to each side of the vis-
ceral mass, and there ramifying over these organs. That,
however, on the left side sends a large branch along by the
side of the intestine to the great ventral channel of the gill ;
while the corresponding branch of the right side dies out
before reaching the opposite margin of the visceral mass.
Here, then, ceases the bilateral symmetry of the vascular
organs; were it carried a little further, there would exist
two ventral branchial channels ; and thus a right pair of
gill-plates might be developed, one fold being 011 each side
of the channel ; and in this way the respiratory organ would
be exactly similar in all essential characters to that of a
Lainellibranch. And if the roots of the two lateral trunks

ANATOMY AND PHYSIOLOGY. 61

that proceed from the heart were dilated into auricles, the
rudiments of the Lamellibranchiate heart would also be
established. This idea of an arrest of a bilateral growth
is somewhat strengthened by Krohn's description, already
quoted, of the development of Ascidia mamillata, in which
the young at first has two distinct lateral atrial spaces and
two lateral excurrent orifices ; the spaces ultimately coalesce,
as do also the orifices, the tendency to bilateral development
terminating at a very early period.

If this view of the homologies of these organs be correct,
then the cloacal, or that which has been uniformly designated
throughout this communication the ventral surface, will cor-
respond to the dorsal region of the Lamellibranch ; and con-
sequently the opposite margin will be the ventral aspect, and
the so-called right and left sides will have to interchange
appellations. Thus the excurrent tube will become dorsal,
and the iiicurrent ventral, as they are in the Lamellibran-
chiata, and, without any great disturbance of the parts, all
the viscera will assume their proper positions.

Before the probability of this determination of the homo-
logical relations can be admitted, it is necessary to ascertain the
true nature of the ganglion, which, as we have seen, is placed
between the respiratory tubes. In the Polyzoa the ganglion
is placed on the rectal aspect of the oesophagus, immediately
below the mouth, and gives its nerves to the tentacles and to
the oesophagus in the direction of the mouth, but none to the
" endocyst " (mantle) or to any other organ. Therefore it can
scarcely be homologous with the ganglion in the Tunicata,
which distributes all its nerves to the walls of the respiratory
tubes (which are mere prolongations of the mantle) and to
the mantle itself. In the Lamellibranchs, however, there is a
ganglion (or a pair of ganglions), namely the branchial, the
most constant in these animals, situated upon the posterior
adductor muscle, which, besides supplying the gills, gives
nerves to the dorsal portions of the mantle and to the respira-
tory tubes, parts which are the undoubted homologues of
those which receive the nerves from the ganglion in the
Tunicata. It therefore seems impossible to avoid the con-
clusion that the ganglion in the latter is the true representa-
tive of the branchial ganglion in the Lamellibranchiata :
ganglia supplying homologous parts must likewise be homo-
logous.

This determination of the nature of the ganglion agrees
well with its position, which in relation to the respiratory
tubes is almost precisely similar to that of the branchial

62

B1JIT1SH TUNICATA.

gang-lion. And we thus find in the nervous element a cor-
roboration of the above suggestion as to the homological
relation of the branchial sac.

v.d.

FIG. 12. — Ascidia mentula. i. Intestine, v.d. Vas deferens. od. Oviduct.
ch. Blood-channel laid open. This channel lies immediately below the
reproductive channels and between them and the mantle.

(63)

CLASS TUNICATA.

ANIMAL acephalous, soft, or coriaceous, simple or
compound, without shelly covering or hard parts,
having two envelopes or tunics and two apertures, an
inhalent and an exhalent. Outer tunic or test varying
in form in the different families, from a simple sac in
the solitary or social to a common gelatinous envelope
in the compound species. Liner tunic or mantle always
soft and sac-shaped. Branchiae forming a large internal
cavity more or less reticulated. Circulation alternately
reversed at short intervals in opposite directions. Her-
maphrodite.

Order 1. SACCOBRANCHIATA.

Animal usually sessile and generally attached, more
or. less sac-shaped, simple or compound. Bra-ncliise
forming, an internal reticulated sac. Undergoing a
metamorphosis, the young in its first or larval state
being tadpole-shaped and swimming freely through
the water by means of a long vibratile tail.

Tribe 1. SOLITAELffl.

(Simple and Social Ascidians.)

ls single or united into groups at the base,
sac-shaped or occasionally elongated, with two tunics,
the outer (test) coriaceous .or membranous, the inner
(mantle) soft and muscular, enclosing the viscera.
Two tubular or papillose apertures (the branchial or
inhalent and the anal or exhalent), usually not far
apart, never at opposite ends. Branchial sac generally
occupying a large part of the interior of the body.
Branchial orifice with a circle of tentacular, tubercular
filaments.

64 BRITISH TUNICATA.

Family 1. ASCIDIAD.E.

A a I ut id simple, fixed, sac-shaped, coriaceous or
gelatinous. Test adhering to the mantle at the two
orifices only, except at the point where the blood-
vessels pass through. Branchial aperture eiglit-lobed,
anal aperture six-lobed, with ocelli between each lobe.
TriitariiJar filaments simple, linear. Bram-lilal
without folds.

Genus 1. ASCIDIA Linnaeus, 1767.

Ascidia (pars) LINNAEUS Syst. Nat. ed. 12, 1 [2, 1767], p. 1087;
MULLER Zool. Dan. Prod. (1776), p. 225, and Zool. Danica
(pawhii) [1788-181Q] ; FABRICIUS Fauna Groeiil. (1780),
p. 330 ; [BRUGUIERE Hist. Nat, Vers, I (1789), in Encycl.
Meth. p. 141] ; Bosc Hist. Nat. Vers, I (1802), p. 98;
LAMARCK Hist. Nat. Anim. sans. Vert., ed. 1, III (1816),
p. 115, and ed. 2, III [1840], p. 524; CUVIEE Regne
Animal, II (1817), p. 497; BLAINVILLE Man. Malac. et
Conch. [1825] , p. 583; [STARK Elem. Nat, Hist. II (1828),
p. 117;] FORBES and HANLEY Hist, Brit. Moll. I [1848],
p. 30 ; ALDER and HANCOCK Cat. Moll. Northmnb. and
Durh. in Trans. Tyneside N.F. Club, I [1848], p. 199;
GOSSE Man. Marine Zool. II [1856], p. 35; [THOMPSON
Nat, Hist. Ireland, IV (1856), p. 359].

Phallusia SAVIGNY Mem. Anim. sans. Vert., pt. 2 (1816),
p. 161 ; MILNE-EDWARDS [Obs. Ascid. Comp. in Mem.
Acad. Sci. XVIII (1841)].

Pirena and Phalluxia (pars) FLEMING Brit. Anim. (1828),
p. 468.

Axrt'diniii (of Baster) WOODWARD Man. Moll. [1856], p, 337;
H. and A. ADAMS Gen. Eecent Moll. II [1858], p. 589.

Animal ovate, coriaceous, semi-transparent, partially
contractile, sessile, and usually attached by the right
side. Branchial njiriiirre 8-lobed, anal aperture 0-lobed,
with the ocelli more or less conspicuous. Tentacular
jila in ruts linear. Brancliial sac large, generally ex-
tending to the bottom of the mantle ; the meshes recti-
linear, with papillae at the intersections. >s'/o, ,/,/<•// and

ASCIDIA. 65

c lateral. Reproductive <.>r</anx — ovaries usually
coufiued to the left side.

The Axriiliniii of Baster, there can scarcely be any
doubt, is a (.'yntJna. But the Linneeaii genus Am-uHa
undoubtedly comprised both true Axeidix and Ci/utlil;r.
There can, therefore, be no doubt as to the propriety
of giving precedence to the name Axridia over that of
Phallusia of Savigny, which has been pretty exten-
sively adopted by naturalists, though it was not used
until many years after the date of the twelfth edition

«/ «/

of the ' Systema Naturae ' ; and indeed were there any
doubt respecting the genera included in that work the
priority of Asn'tlio is sufficiently established by the
employment of that name by Miiller and Fabricius in
their respective works quoted in the above synonymy.
Much of the internal structure of the Ascidi& has
been worked out by Cuvier, Savigny, and others,
though not with that minuteness which science now
requires. Professor Huxley has also done much and
earnestly in this field of inquiry, but the detailed
results of the labours of this able anatomist have not
been given to the world. We have therefore thought
it necessary, in the following account of the anatomy
of the Ascidiae, to go pretty fully into the subject, and
more especially as the structure of these, the more
highly organised, Tunicates, will not infrequently be
used throughout this work as a standard of comparison
by which to estimate the structural differences of the

various groups.

The test of Ascidia is firm, thick, and elastic, and
more or less transparent ; it is usually smooth, though
not infrequently coarse, aculeated, or scabrous, and occa-
sionally covered with extraneous matter. It is some-
times delicately coloured, but is more frequently of a
watery tint. It is attached to the mantle only at the ex-
tremities of the respiratory tubes, and at the point where
it receives blood-vessels. The mantle in some species
is ornamented with vivid colours, and is well supplied
with muscular fibres which run in various directions.

5

66 BRITISH TUNICATA.

The moutli opens at the bottom of the branchial sac
towards the ventral margin. In some of the species,
however, as in A. mentnla, for example, the branchial
sac extends backwards some way behind the oral

e/

orifice. The oesophagus is short and constricted ; it
opens into the anterior or ventral extremity of a well-
marked stomach, which is usually a wide rounded
sac laterally compressed, lying diagonally across the
pallia! chamber between the right pallia! wall, to which
it is adherent, and the branchial sac. The intestine
is a wide even tnbe. It passes from the opposite or
dorsal extremity of the stomach, and ascends for some
distance, when it crosses over to the other or ventral
side in a more or less nndnlatory course, thus forming
one or two loops, and then ascends again to reach the
cloaca a little in advance of where the oesophagus joins
the branchial sac. Here it terminates in a wide anal
opening.

The whole alimentary tube is lined with a stout
mucous membrane which is frequently plaited or
wrinkled. This membrane forms in the intestine a
strongly denned groove which is extended into the
stomach.

In all the As<-i<li;i' the alimentary tube is coated
externally with a pretty thick layer of a gland-like
substance composed of comparatively large, globular
vesicles with thin reticulated walls, each having in its
wall a large, opaque, simple or compound nucleus
(fig. 2, p. 24). These vesicles have no communica-
tion with each other, they are not connected with any
duct, nor do they open in any way into the alimentary
tube. This gland-like substance cannot subserve the
function of a liver, though by some naturalists it has
been suggested that it does so.

The true hepatic organ lies beneath this vesicular
mass, and forms a thin coating on the surface of the

tj

intestine (fig. 3, p. 25). It is composed of delicate
tubes dividing dichotomously, but frequently without
much regularity. At the points where the branches

ASC1DIA. 67

are given off, the tubes are usually enlarged, and the
twigs terminate in rounded extremities which are more
or less inflated.

In A. riU(.'itfnla the dichotomous division of the tubes
is very obvious, and the enlargements or ampullae at
the junctions of the branches are greater than usual
and assume a triangular form. Oval enlargements also
frequently occur among the branches, which latter,
uniting, go to form two long slender ducts which pass
backward within the loop of the intestine, buried
amidst the vesicular substance already described, and
at length open through the left wall of the stomach
about midway between the cardia and pylorus, towards
the anterior margin. These two ducts come from the
middle portion of the intestine ; another duct, passing
from the lower portion, unites with one of those first
mentioned just before it sinks into the wall of the
stomach.

In A. sordid a and A. srolrit the arrangement of the
parts of the hepatic organ is similar to that in the
above species.

The reproductive organs are well developed in the
Ascidiae, and in all of them the sexes are combined, as
is usuallv the case in the whole class. The male and

t/

female elements are, however, always secreted by
distinct organs, which are provided with their respec-
tive ducts.

In A. sordida the ovary is composed of numerous
tubular branches which ramify in a radiating manner
over the left side of the looped portion of the intestine.
The oviduct passes through the loop, and, following
the curvature of the intestine, opens by the side of the
anus into the cloaca. The fas defer ens terminates
near the same point, and is adherent to the oviduct
throughout its course. In the vicinity of the ovary it
receives several much-attenuated branches from either
side of the intestine ; these divide dichotomously, the
ultimate twigs terminating in elongated and irregularly
lobulated vesicles, which are spread over the intestinal

68 BRITISH TUNICATA.

lobe, and which also exhibit a tendency to dichotomous
division ; these are the male secreting vesicles.

In A. scaLra, A. affinis, A. niri/tnlx, A. venosa, etc.,
the same arrangement of the reproductive organs
obtains, but the ovary in A. iiit.'iitiiJn is lobulated, and,
lying within the loop of the intestine, is seen at both
sides of the alimentary tube, and consequently has the
appearance of being double. In A. renosa the male
vesicles are exceedingly minute and very numerous.

The heart in Asciditi is tubular and is attached to
the lower or posterior border of the stomach, one end
extending some way up the dorsal region towards the
intestinal tube ; this is the dorsal extremity ; the other,
the ventral extremity, points in the direction of the
oesophagus. It lies between the mantle and the lining
membrane within a distinct chamber or pericardium,
along one side of which it is attached from end to end
(Plate III, fig. 4).

A large trunk vessel passes from the dorsal extremity
of the heart and immediately divides into three branches,

u

one of which advances along the dorsal region at the
back of the endostyle ; another passes in the opposite
direction down the dorsal margin to the bottom of the
branchial sac. These two form the dorsal branchial
channel, and are equivalent to the ventral or thoracic
sinus of Milne-Edwards ; and they both communicate
with the dorsal extremities of the transverse channels
or primary vessels of the branchial sac. The third
branch turns off at right angles to this great dorsal
channel close to the point where it is united to the
heart, and, in company with another vessel to be
shortly described, penetrates the mantle, and goes to
ramify in the test.

From the other extremity of the heart there are two
lars'e trunk vessels siven off, one to each side of the

O o *

stomach. These ramify over the digestive organs and
supply the pallial plexus. The trunk branch of the
left side divides into two large stems, one of which
inclines towards the intestine, the other towards the

ASCIDIA. 69

oesophagus ; the former, penetrating the mantle in the
dorsal region, goes associated with the third branch
from the dorsal extremity of the heart to ramify in the
test. Tims originate the double vessels which carry
the nourishing fluid to and from the outer tunic. The
stem that goes towards the oesophagus turns aside to
join the great ventral branchial channel, the dorsal
sinus of Milne-Edwards, which communicates with the
ventral extremity of the transverse branchial channels
(Plate III, figs. 2 and 3). These latter channels, or
primary branchial channels, communicate also with the
visceral and pallia! plexuses through the agency of the
branchial suspenders. Thus every portion of the
organism is brought under the influence of the heart.

\\Hieii the heart pulsates in the direction of the
dorsal extremity the blood is at once thrust into the

e/

test and branchial organ; a portion of it will then find
its way by the suspenders into the pallia! plexuses of
both sides and into the visceral plexus, and thus to the
ventral end of the heart, before reaching which point,
however, it will mingle with that from the great
ventral branchial sinus and that returned from the
test. Thus the blood which reaches the heart is only
partially aerated, as neither that which circulates in
the test nor that which comes directly from the visceral
and pallia! plexuses can to any extent be aerated.
When the action of the heart is in the opposite or
ventral direction, the reverse of this will take place,
but then the only unaerated portion of the blood-
return is that which lias supplied the test.

The pulsations of the heart are not of equal number
in each oscillation ; there is usually a little variation
in this respect. In a young individual of A. sordid a
in which the pulsations were counted there were loS
in one direction and 120 in the other.

The minute structure of the branchial sac varies a
little in the different species of this genus. The
simplest form of the structure is found in A. -renosa.
In this species the transverse or primary vessels or

70 BRITISH TUXICATA.

channels are placed at regular intervals and scarcely
vary at all in size ; and between and opening into
them at right angles are numerous small longitudinal
secondary vessels divided by elongated spaces or
stomata, so that the whole forms a reticulation of
vessels, in which the transverse channels are lar°'e and

J o

distant, the longitudinal small and numerous, and
divided only by narrow open spaces (Plate X).

This simple structure of the aerating organ is not
usual in the Avcidiw, though it is fundamentally the
same in all. In A. mentida, A. sordida, A. scnbrn, A.
((ffiitis, and their allies, the simple reticulated branchial
web of A. reuoxa has, as it were, become minutely
folded or plaited longitudinally, so as to give to the
surface the appearance of corduroy, but the flutes or
grooves between the ridges or plaits are interrupted
wherever the transverse vessels cross them, turning
them into series of minute recesses or pouches.

The longitudinal bars which project from the true
aerating surface of the branchial sac extend the whole
length of the organ ; they are usually stout and rather
rigid, and are attached only at the points where they
cross the primary transverse vessels, and at this point,
too, they have projecting from their upper surface
elongated papilla? which usually bear ciliated discs,
and have a wide membrane stretched from the back
for a considerable way along the transverse vessels.

t/

In A. mentula and allied species there are small inter-
mediate papillae between those at the points of inter-
section. In A. sonliilii, A. xi-aLi-n, and A. « ft nix there
are no intermediate papilla? on the bars, but in all of
them the papillae at the points of attachment are in
connection with a wide membranous expansion, and
distinct ciliated discs are arranged in pairs on the
transverse vessels between the longitudinal liars. In
some species there is a ciliated disc on the liars
between the papillae. In A. venosa the bars are more
delicate than usual, and the membrane in connection
with the papillae is inconspicuous.

ASCIDIA. 71

The oral lamina is well developed in all the Aseidise.
It is usually a wide plane membrane extending along
the ventral margin of the branchial sac from one ex-
tremity to the other, passing on the right of the oral
orifice in those species in which the sac is prolonged
backwards ; in those with the sac not so prolonged it
terminates at the right side of the mouth. In many
of the species the oral lamina is transversely ribbed ;
the ribs are strongly developed in A. mentula, [J.
Alderi, A. aculeata, etc.,] and in these species they pass
beyond the margin as fine points, giving to the lamina
a pectinated appearance ; the function of this organ is
to convey the food to the mouth (Plate XIX).

The endostyle extends the whole length of the
branchial sac, and is in connection with two mem-
branous folds which form a longitudinal groove and

O O

within which it seems to be embedded. It is com-
posed of two flattened rods of a rigid, opaque, yellow
substance. The folds are in connection with the
anterior cord or collar, a narrow cord-like fold of the
lining membrane which encircles the entrance to
the branchial sac, and which is likewise in connection
with the oral lamina. Below, the folds of the endo-
style are also connected to the oral lamina by a similar
cord-like fold.

The circle of tentacular filaments within the base of
the incurrent tube is always situated a little above the
entrance to the branchial sac (Plate III, fig. 1). The
filaments vary in size and number in the different
species in the wThole of the genus, but are always
linear and pointed or slightly conical.

The branchial tubercle, that curious and enigmatical
organ situated immediately in front of the upper
extremity of the oral lamina, at the entrance of the
branchial sac, is composed of two folds of the lining
membrane pressed close together, and convoluted more
or less in the various species so that it usually assumes
the form of a rounded or oval, depressed, compact,
tubercular swelling (Plate XX).

72 BRITISH TUNICATA.

The single ganglion of the nervous system of
A*fi<Ua is, as usual, placed between the respiratory
tubes. It lies in a blood-sinus situated between the
inner tunic and lining membrane. It is fusiform,
varying little in character, and is partially folded in a
much folliculated gland-like substance, as determined
in A. merit/ill (figs. 10 and 11, p. 50) and in some other
species. Three or four nerves are given off from each
extremity, all of which go to the respiratory tubes ;ni<l
to the adjacent portions of the inner tunic or mantle.
A branch from one of the principal nerves has been
traced to the branchial tubercle.

1. Ascidia mamillata Cuvier.*

(PI. I, and fig. 13 in text.)

mamillata CUVIER [Mem. Ascidies in Mem. clu Mus.
II (1815), p. 30, pi. iii, and Mem. Asc. p. 22, pi. iii, in]
Mem. cles Moll. (1817) ; LAMARCK Hist. Nat. Anim. sans.
Vert. ed. 1, III (1816), p. 125 ; ed. 2, III [1840], p. 532.
Phalln.yin inn HI tUata &AVIGNY Mem. Anim. sans. Vert. pt. 2
(1816), p. 168.

FORBES in Brit. Moll. I [1848], p. :>2.

I >< n] H oblong-ovate, opaline, white or yellowish,
mamillated with unequal rounded eminences. Aper-
tures, branchial terminal, anal about one-third down,
generally terminating on the left side ; ocelli incon-
spicuous. Trxf thick, firm, and cartilaginous, smooth,
and of a porcelain-like lustre, more or less marked
with delicate branched or net-like lines. Man fir dark
blue. Tentacular filaments few and rather small.
Branchial sac with rather broad papillae. [Oral

: The habitat and first British record of each species have been added
when ascertainable ; if from the anthers' MS., without indication of inter-
polation ; if from other sources, inserted within brackets. As the localities
are not in any definite order in the MS., they have been rearranged through-
o\it, referred (with the exception of districts and well-known islands) to
their counties, and grouped under the different countries of the British
Isles. No addition has been made, cither to the synonymy or localities,
from information published more recently than 1870.

ASOIDIA MAMILLATA. 73

narrow, strongly pectinated or transversely
ribbed. Br<uir]/in/ tn/>rn-le. inconspicuous.]
Leiiijtlt from three to four or five inches.
Ha/>. — Adhering- to loose stones, etc.

ENGLAND. — Not uncommon on the south coast ; rare
or entirely absent in the north. Luhvorth Cove
(Jeffreys) and We y mouth (trow), Dorset. Salcombe
Bay (Hinclcs), Tor Bay (Aider), and Plymouth
(Stewart), Devon. [Falmouth, Cornwall (Cocks, I84Q).]
Isle of Man, rare (Alder).

SCOTLAND. — Lamlash Bay, Arran, rare (Alder).

First record. — Forbes, 1848, as A. arachnoidea.

This species (PL I) adheres diagonally by the base,
from which it often throws out ramifications of the
test to a considerable distance, running among loose
stones and binding them together into a compact mass.
On account of the bend of the mantle and branchial
sac upwards, the anal aperture is displaced from its
usual ventral position, and appears generally on the
left side, sometimes even assuming a sub-dorsal aspect.

The bending of the body upwards is a very striking
feature in the species, and does not merely alter the
situation of the excurrent tube as stated above, but
throws many of the organs out of their regular position.
The bend is to the right side, inclining towards the
ventral margin, and the lower extremity of the mantle
is brought nearly as far forward as the anterior border

t>

of the intestinal loops. The branchial sac, which
extends to the lower end of the body, is also bent
upwards, and consequently the endostyle forms a
very wide loop ; the heart is likewise bent in the
same direction, and the upper portion of the
endostyle is drawn somewhat towards the ventral

ts

margin. In fact, while the dorsal margin is in a
manner much elongated, the ventral margin is greatly
shortened, so that the oral band can be little more
than one third the length of the endostyle. The band
itself is narrow and strongly pectinated or ribbed
transversely, and is in front split into two lateral mem-

BRITISH TUXICATA.

branes much farther downwards than usual. The
collar of tentacular filaments at the base of the in-
halant tube is very near to the anterior margin of the

v . O

branchial sac ; and there are fifteen or sixteen rather
short filaments, with two or three minute ones between
them. But what is most peculiar in this species is the
deficiency of the branchial tubercle or any trace of it ;
we have examined three specimens and in not one of
them could we find this enigmatical organ so constant
in the Tunicata.

The branchial membrane (fig. 13) is rather stout
and is minutely plicated longitudinally ; the primary

—

-

-

' {\* ^ "*
ffli

FIG. 13. — Part of the branchial sac of Ascidla mamillata. Highly magnified.

vessels are numerous and fine, Avith a few larger ones
interspersed. The longitudinal bars are also numerous
and less robust than the primary vessels with which
they form square meshes ; there is a large conical
papilla with the apex rounded, at each intersection,
and as the meshes are small the papillae have a rather
crowded appearance, especially as there is a small
papilla on the longitudinal bars, between each pair of
large papillae, and the membrane in connection with
the latter is short. The meshes or stomata of the
secondary vessels are of the usual rectilinear form, but
are less elongated than in many species.

The reproductive organs are confined to the right
side of the body. The testicular caeca are spread over

ASCIDIA MAMILLATA. 75

Mini are partially buried amidst the cellular matter of
the intestine, but are mostly accumulated towards the

V

dorsal border. The minute twigs of the duct are
greatly enlarged in places, are irregularly tuberous
or nodose, and give off short caecal processes. There
is but one ovary, which lies concealed in the cellular
matter at the upper extremity of the intestinal loop ;
it is an elongated sac with the duct at first small, but
on passing through the loop of the intestine it is much
enlarged when it reaches the other side of the body.

There can be little doubt that the Ascidia aracli-
uoitJcd of Forbes is identical with tht A. mamillata of
Cuvier. The rich supply of blood-vessels ramifying
through the test in this species, and rising towards
the surface in the smaller ramuli, give it that delicately
reticulated appearance which suggested to Professor
Forbes the name of arachnoidea. That distinguished
naturalist dredged it in the ^Egean, whence it appears
to range to the south and west of England, disappear-
ing farther north.

2. Ascidia mentula Mailer.

(PI. II ; III ; XVII, fig. 1 ; PI. XX, fig. 1 ; and figs.
5, 6, 10, 1], 12, and 14, in text.)

Axc'idla meutnla MULLER Zool. Dan. Prod. [1776], p. 225,
no. 2724, and Zool. Danica, I [1788], p. 6, pi. viii, f. 1-4;
FABIUCIUS Fauna Groenl. [1780], p. 331 ; [MONTAGU Test.
Brit. II (1803), p. 532 ;] LAMARCK Anim. sans. Vert. ed. 1,
III [(1816), p. 125]; ed. 2, III [1840], p. 532; [STEWART
Elem. Nat. Hist, I (1817), p. 391 ; BRUGUIERE] Vers, 1
[1789], p. 145, pi. lxii,f. 2-4, in Encycl. Meth. ; [STARK
Elem. Nat, Hist. II (1828), p. 117;] DALYELL Eare Anim.
Scotland, II [1848], p. 146, pi. xxxvi, f. 6, and pi. xlvi ;
FORBES and HANLEY Brit. Moll. I [1848], p. 32, pi. C, f. 1 ;
[GAEUS Zool. Scilly Isles in Proc. Ashmol. Soc. II (1851),
p. 266; LANDSBOROUGH Excurs. Arraii (1852), p. 49;
THOMPSON Nat, Hist, Ireland, IV (1856), p. 359 ; NORMAN
in Zoologist, XV (1857), p. 5707: MERRIFIELD Nat. Hist,
Brighton (1860), p. 80 ; MC!NTOSH in 'Proc, E, Soc. Edinb.
V (1866), p. 605 ; ALDEEinRep.Brit.Assoc. 1866 (1867),
p. 207; NORMAN in Eep. Brit, Assoc, 1868 (1869), p. 302].

76 r.KITISH TUNK'ATA.

Ascidia monarclius CUVIEK Mem. Ascidies in Mem clu Mus.

II (1815), p. 32.
PhaUitsin monarchus SAYIGNY Mem. Anim. sans. Yert. pt. '2

[1816], p. 167, pi. x, f. 2,

[Pluillnxift inriitnla FLEMING Brit, Anim. I (1828), p. 468.
Ascidia mentula et commnui* (Forbes MS.) THOMPSON in

Ann. Nat. Hist. (1) XIII (1844), p. 434.
Ascidia cum munis FORBES (MS.) in Rep. Brit. Assoc. 1850

(1851), p. 242.]
AveifUnm incniareltu* WOODWARD Man. Moll. [1856], p. 337,

f. 224.
'Ascidium mmtula ADAMS Gen. Rec, Moll. (1858), pi. cxxxni,

f. 1.]

FIG. 1-i. — ^scich'if utentnla. One-half natural size.

Boilij oblong or irregularly ovate, and much pro-
duced 'towards the upper end; coarse, horn-coloured,
but varying from greenish white to very dark brown,
usually adhering more or less by one side. Apertures
distant, sessile, the branchial one terminal, the anal 011
a bulging of the side, about two-thirds down ; ocelli
yellow with a central red spot. Text thick, tough, and
cartilaginous, semitransparent ; occasionally roughly
furrowed, but not tuberculated ; often with irregular
swellings produced by imbedded mussels. Mantle red,
especially towards the apertures ; greenish, or inclined
to brown. Tentacular filainrnts rather numerous, of
equal length; mostly stout, Branchial sac with
moderate- sized papillae at the intersections of the
meshes, and intermediate smaller ones on the longi-
tudinal bands or bars. Oral lamina transversely
ribbed and strongly pectinated.

ASCIDIA MEXTVLA. 77

usually from four to six inches (occasionally
much longer).

Hal). — From within tide-marks to cleepish water
(adhering to rocks, &c.).

ENGLAND.— [Brighton, Sussex (MerrijieLJ, 1800).]
Lulworth Cove, Dorset (Jeffreys). [Torcross, Devon,
dredged, with ftulirlla pnnciUitx adhering to it (Mon-
tagu, 1803). Falmouth, Cornwall (Cocks, 1849).
Scilly Isles (Cams, 1850).] Isle of Man (Furl**).

WALES.— [Tenby (Woocliranl, 1856).]

SCOTLAND. — [Clyde (Forbes, 1S50). Corrigils, Arran
(Lands oo rough, 1852). Lamlash, Arran; and ('umbrae
(Norman, 1857). Hebrides (Forles, 1850). North
Uist (Melntosh, 1865).] Not uncommon on the North-
west coast (Forbes). Orkney Isles (Allman and Forbes).
Shetland Isles (Forbes and ./<•//>/•//*). [Middle Haaf,
Shetland (Norman, 1868).]

LRKLANK — North-west coast (Thompson). [Belfast
Bay, Antrim ; Clew Bay, Mayo ; and Roundstone
Bay, G-alway (Thompson, 1844). Bantry Bay, Cork
(Wright).]

First record.- {Montagu, 1803.]

Ascidia mentida (fig. 14) is attached by a small
portion of the side of the body towards the posterior
extremity, or diagonally by the base; never, or rarely,
by the whole side, as is the case with some of the allied
species. The test, which is rather opaque and fre-
quently thick, rough, and coarse, is well supplied with
vascular channels, which in specimens preserved in
spirits, being yellowish and somewhat opaque, can
usually be well observed ramifviner in the semitrans-

i/ *j <—>

parent substance of the test. They are much sub-
divided, and the twigs which approach the inner sur-
face are usually simple, or only occasionally a little
enlarged at the extremities ; those which are seen at
the external surface terminate in irregularly-rounded
enlargements.

The mantle is well supplied with interwoven mus-
cular bands, longitudinal, transverse, and diagonal ;

78 BRITISH TUNICATA.

the longitudinal ones are not very numerous and are
mostly confined to the anterior portion. The tubes
are very short, the anal being a little longer than the
branchial, the orifice of which is almost sessile.

The branchial sac (PI. II, and PL XVII, fig. 1) is
coextensive with the mantle ; both extend consider-
ably behind the visceral mass and are reflected a little
upwards on the right side as in A. mamttlata, there
being a slight internal ridge across the posterior
portion of the test. The branchial sac is prolonged
for some distance* below the mouth ; the walls are
minutely, but distinctly plicated ; the primary vessels
are numerous and vary in size, the larger having
several smaller ones between them. The stomata are
rather long and wide, with the extremities rounded,
sometimes a little pointed. The papillae are conical,
well developed, alternately large and small, and the
papillary membrane is unusually ample; the branchial
bars are stout, with a widish membrane extending
along the inferior margin. The oral lamina (PI. II)
is continued from one end of the branchial sac to the
other, diminishing a little in width after passing the
mouth ; it is wide, strongly ribbed on both sides, and
has the margin pectinated in advance of the mouth ;
behind it the margin is smooth, or nearly so. The
belt of tentacular filaments on the left of the mouth
reaches to the bottom of the branchial sac, and is
strongly developed ; the filaments are closely set and
numerous, there being sometimes as many as seventy ;
they are wide at the base and pointed above. The
endostyle (PL II, PL III, fig. 5, and figs. 5 and f> in
text) extends the full length of the gill. The branchial
tubercle (PL II, and PL XX, fig. 1) is usually irregu-
larly rounded, with the extremities turned a little
inwards; but the organ is subject to great variation
in this species, the extremities sometimes bending in
one direction, sometimes in another, and varying in
length and extent of convolution. The tentacular fila-
ments at the entrance of the branchial sac are arrang-ed

o

ASCEDIA MENTULA. 79

in a single row on a muscular ridge or collar
(Plate III, fig. 1) ; they vary considerably in size,
number upwards of forty, and are usually placed a
little apart, and not far above the margin of the
branchial sac.

The ovary is situated in the loop of the intestine
and is seen at both sides of that organ; it appears as
a lobulated, compact mass, and does not extend over
the walls of the alimentary tube. The male caeca are

e/

conspicuous on the right side of the intestine as white
dendritic tufts ramifying over the surface and partially
buried in the cellular matter, a thick layer of which is
spread over the whole of the digestive organs.

Professor Edward Forbes considers this to be the
commonest of our deep-water Ascidians ; but it has not
yet been met with on the north-east coast of England.
It appears to be frequently met with, though not very
common, on the south and west coasts. Sars states
that it extends along the whole of the Norwegian coast,
and also occurs in Greenland and North America. His
remark that the tentacular filaments are conspicuous
between the ocelli, in both orifices, must refer to the
internal folds of the apertures which terminate in
points above. The tentacular filaments are confined
to one aperture and do not appear outside.

Asriilia titntfiilti, is one of the largest and most
uncouth-looking of our native Ascidians, often being-
disfigured by extraneous substances and by swellings
caused by Modiola TIKI /•///»>/ •</ hi imbedded in the test.
Miiller says that it is pilose, but this is an error probably
occasioned by some small zoophytes covering the sur-
face. Professor Percival Wright informs us that he
has met with AxriJin uit-nt/ila, in Bantrv Bay, measur-
ing eleven and a half inches long and two and a half
broad. A remarkable monstrosity of this species was
sent to us from Lulworth Cove by our friend Mr.
Jeffreys. It consisted of two perfect Ascidians im-
bedded in one test, one of them rising perpendicularly
above, and the other lying diagonally across, the base.

80 BRITISH TUXICATA.

Externally the test was continuous without depression
or indication of any kind that it covered more than one
individual, excepting that it had four orifices instead
of two ; internally there was a ridge dividing it into
two cavities, which however were not closed, but com-
municated freely with each other.

3. Ascidia robusta Hancock.
(PL XX, figs. 2 and 3 ; and fig. 15 in text.)

[Ascidia ml) list a HANCOCK in Ann. Nat. Hist. (4), VI (1870),

p. 358.]

Body elongated, irregularly ovate, produced in front,
very coarse, with a tinge of red, particularly towards
the orifices ; adhering by the whole side, but sometimes
much distorted and with adherent, root-like prolonga-
tions. Apertures tubular, much produced, the branchial
one terminal, the anal more than half way down, and
inclined backwards ; ocelli red. Test extremely thick,

e

tough, hard, and cartilaginous, usually with root-like
prolongations, semi-transparent, very coarse and rough,
irregularly furrowed and pitted, and frequently much
overgrown with zoophytes. Mantle tinged with red,
intensified towards the orifices ; tubes long, the anal
one much produced and turned backwards. Tt>itf<iai/<i r
filament* rather slender, not crowded, with small ones
between the larger. Branchial xac extending a little
behind the visceral mass ; minutely plicated with well-
developed tubercles, alternately large and small. Oral
bimina ribbed transversely and. strongly pectinated
near the mouth.

Leiti'/tlt from four to five inches.

Huh. — Between the roots of Laminaria ditjitata.

CHANNEL ISLANDS. — [Herm,] Guernsey (Norman).
First record. — Hancock, 1870; coll. Norman [18(35].

This is not only one of the largest, but is perhaps
the coarsest, of the British Tunicata. The test (fig.
15) is usually more or less tinged with red, principally

ASCIDIA BOBUSTA. 81

in consequence of the red colouring of the vascular
channels. In young specimens, however, it is some-
times of a uniform rose-colour, and in this state it is
pretty regular in form, and is attached by the whole
side. When full grown the test is remarkably rough,
hard, and thick, and frequently much distorted. The
larger specimens, obtained at Guernsey by Mr. Norman,
were firmly inserted between the roots of Laminaria
digitata, and so hard were the tests and their prolonga-
tions that they were with difficulty cut free with a
knife. The blood-channels in the test are more or
less of a red colour, mostly rounded and enlarged at
the extremity, and rather crowded.

FIG. 15. — Ascidia robusta. One half natural size.

The mantle is more or less red in colour, sometimes
it is of a full rose-colour heightened towards the ori-
fices. The right or attached side is almost devoid of
muscular fibres, but on the other or free side they are
numerous, and as it were felted ; the tubes are long,
particularly the anal, which is turned backwards.

The branchial sac extends only a little way behind
the visceral mass ; it is minutely plicated. The papilla?
are conical, not very wide at the base, and their apices
are rather sharp ; they are alternately large and small,
though nearly of equal length. The endostyle reaches
to the bottom of the sac. The oral lamina is not very
wide ; it is strongly ribbed transversely 011 both sides,
and has the margin slightly pectinated in advance "of
the mouth where it suddenly narrows ; in the neighbour-
hood of the mouth the pectinations are unusually long ;

6

82 BRITISH TUNICATA.

below the month both the ribs and pectinations die
out, and the membrane becomes very narrow before it
reaches the bottom of the sac. The tentacular points
on the left side of the mouth are large and triangular
with the apices sharp ; sixteen or seventeen above and
at the side of the mouth are placed close together;
below, they are wide apart, usually few in number and
in some instances entirely wanting. The branchial
tubercle (PL XX, figs. 2 and 3) is oval in the antero-
posterior direction, with the extremities not convoluted,
but turned directly inwards and downwards. This
organ, however, appears to vary, and in two or three
instances it was somewhat lozenge-shaped, very large,
and composed of numerous irregular convolutions ; in
others again the loop is small and simple with the
extremities turned sometimes to one side, sometimes
to the other, and slightly convoluted. The tentacular
filaments at the base of the branchial tube are arranged
on a delicate muscular collar in a single line rather
close to the branchial margin; they vary in number
from thirty to forty-five, and are delicate, with smaller
ones interspersed.

The ovary is lobulated and placed in the intestinal
loop, appearing at the left side. Traces of the male
C£eca are observed on the right side of the intestine ;
they are usually, however, obscured by the cellular
matter which thickly covers the alimentary tube,
particularly the stomach ; the cells are smaller than
usual.

This species is closely related to A. mentida and A.
rulAcitndn ; the extreme hardness and thickness of the
test, however, and the great length of the respiratory
tubes, sufficiently distinguish it from both. From the
former it is likewise distinguished by its colour, and by
several other matters of detail.

ASI'IDIA RUBICUNDA. 83

4. Ascidia rubicunda Hancock.
(PI. IV, figs. 1 and 2 ; PI. XVII, fig. 2 ; PI. XX, fig. 4.)

[Ascidia rubicunda HANCOCK in Ann. Nat. Hist (4) VI (1870),
p. 357.]

Bodi/ much elongated, irregularly oval, depressed,
coarse, of an obscure flesh-colour, adhering by the
whole side, with imperfect marginal expansions.
Apertures only a little produced ; the branchial one
almost sessile, terminal ; the anal turned backwards
from a bulging at the side, more than half way down ;
ocelli crimson, small at both orifices. Text thick,
coarse, wrinkled, cartilaginous, semitransparent, of a
flesh-colour, most rosy towards the orifices, occasionally
overgrown with zoophytes. Mantle of a brilliant rose-
colour, much intensified at the tubes, the alimentary
tube of a greenish hue, evidently from the nature of
the contents. Tentacular filaments short and delicate,
varying in size. Branchial xac minutely plicated, with
large conical papillae, the intermediate ones nearly as
large as those at the intersections of the meshes. Oral
lamina ribbed transversely and finely pectinated from
end to end, and of equal breadth throughout.

Length upwards of four and a half inches.

Hub. — [Between tide-marks and at extreme low
tides, sometimes on the stems and roots of Halidrys
siliquosa.]

SCOTLAND. — Hebrides (Norman). [Tobermorey, Isle
of Mull, 1866 (Norman).]

IRELAND. — -[Portaferry, Strangford Lough, Down
(Norman). Birterbuy Bay, Connemara, Gralway
(More).]

First record. — Hancock, 1870; coll. Norman, 1866.

The test (PL IV, fig. 1) is semitransparent, and of
a yellowish flesh colour which is usually heightened to
a full rosy hue at the respiratory tubes ; it is firm,
thick, and cartilaginous. The vascular channels are

84 BRITISH TUXICATA.

numerous, with the terminal twigs red in the vicinity
of the orifices, and frequently red vessels are scattered
over various parts of the test. In some specimens
such coloured vessels are numerous everywhere, par-
ticularly in young individuals. The twigs at the
external surface are comparatively short, and are irregu-
larly enlarged and rounded at the extremities ; those
ramifying within the inner surface of the test are long

t/ o

and slender, usually swelling gradually towards the
ends and occasionally terminating in globular enlarge-
ments.

The mantle (PL IV, fig. 2) is remarkable for the
purity and brilliancy of its colour, the rosy tint be-
coming almost crimson at the tubes, which though
short are distinctly developed, and are of about equal
length. The muscular fibres on the left side are fine,
numerous, and interwoven, the transverse ones pre-
dominating.

The branchial sac (PI. XVII, fig. 2) extends the whole
length of the mantle, and consequently for some dis-
tance behind the visceral mass. It is minutely plicated,
the plicae being as numerous as the longitudinal bars.
The primary vessels are numerous, rather close to-
gether, pretty equal in size, with the exception of a
few large ones placed at widish intervals. The second-
ary vessels are shorthand not very regular, the stomata
varying a little in form, the ends being either pointed
or rounded. The longitudinal bars are stout; the
papillae are large and conical, rather crowded; those
at the intersection of the meshes are scarcely larger
than the intermediate ones ; the papillary membrane is
not much developed. The oral lamina is rather narrow
and of equal width throughout; it is closely ribbed
transversely, even to the bottom of the branchial sac,
the ribs being strongest on the right side, finely pectin-
ated from end to end, and having the tentacular points
on the left of the mouth forming a continuous series to
the bottom of the branchial sac ; they are closely set,
narrow, and pointed. The branchial tubercle (PL XX,

ASCIDIA RUB1CUNDA. 85

fig. 4) varies a little; it is occasionally transversely
wide, and sometimes wider in the opposite direction ;
the extremities are not much or regularly convoluted ;
they usually bend inwards ; but not infrequently the
ends turn, the one inwards, the other outwards. The
tentacular filaments are short and slender ; they vary
much in size, some being quite minute, and number
from thirty to forty.

The ovary is much lobulated, being most developed
at the left side ; occasionally it is not perceptible at
the right side. The male cajca are found at both sides
of the alimentary tube ; they are rather conspicuous,
usually bifid, cylindrical, with the distal extremities
obtuse. The cells coating the alimentary tube are
minute and do not form so thick a coat as usual.

Ascidia rubicunda is related to A. meniida on the one
hand, and to A. robust a on the other, but is dis-
tinguished from both by many characters. It is always
more extensively attached, and is more elongated and
depressed than the former, from which it also differs in
colour. From A. robusta it is likewise distinguished
by its great brilliancy of colour as well as by its general
form, its shorter tubes, and the less robust character of
the test. Many other minor points distinguish it from
both.

5. Ascidia rubrotincta Hancock.
(PI. XVII, fig. 3 ; PI. XIX, fig. 2 ; and fig. 1(3 in text.)

[Ascidia rnbro-tincta HANCOCK in Ann. Nat. Hist. (4) VI
(1870), p. 356.]

Bod 11 pretty regularly oval, smooth, or only very
slightly wrinkled, of a pale-reddish flesh-colour, adher-
ing by the middle portion of the side. Apertures dis-
tant, with the tubes not much produced ; the branchial
one terminal, the anal more than half Avay down the
side ; ocelli red. Test rather thin, cartilaginous, pellu-
cid, of a reddish flesh-colour, smooth or slightly

86 BEITISH TUNICATA.

wrinkled longitudinally ; tubes short, the anal inclin-
ing backwards. Mantle rather delicate, yellowish,
tinged in parts with a reddish flesh-colour. Tenta-
cular filaments numerous, delicate, unequal in size.
Branchial sac minutely plicated, with rather long,
conical papillae. Oral lamina rather narrow, strongly
ribbed transversely, with the margin pectinated.

Length about two and a half inches.

Hah. — Between tide-marks.

CHANNEL ISLANDS. — Guernsey (Norman).

First record. — Hancock, 1870; coll. Norman [1865].

FIG. 16. — Ascidia rubrotincta. Natural size.

The test of this species (fig. 16) is well supplied
with much-branched blood-channels ; the branches are
slender with the ends of the ultimate twigs much
enlarged, elliptical, or pyriform, appearing at the
surface as red points ; all the ramifications partake
largely of the same colour; the enlarged extremities,
however, and the septa dividing the tubes, are most
crowded with pigment-cells.

The muscular fibres of the mantle, which are fine,
interwoven, and numerous, have a glossy, silky appear-
ance.

The branchial sac (PI. XXVII, fig. 3) does not extend
far behind the visceral mass, and is minutely plicated.
The primary vessels are slender, with a few strong-
ones interspersed at irregular intervals. The secondary

ASOIDIA KUBROT1NCTA. 87

vessels are pretty regular, having the stomata recti-
linear, the ends being a little rounded. The papilla?
are large, long, and conical, and are situated on the
longitudinal bars at the intersections of the meshes,
and also on the bars between the intersections ; they
are of nearly equal size, the intermediate ones being
scarcely shorter than the others ; the papillary mem-
brane is strongly developed. The longitudinal bars
are delicate, with a membranous expansion along the
inner margin. The oral lamina (PI. XIX, fig. 2) is not
very wide, but maintains its width for some distance
behind the mouth ; it never becomes very narrow, but
ends rather abruptly at the bottom of the branchial
sac ; it is strongly ribbed transversely on the right
side, and the margin is pectinated throughout; the
tentacular points in front, and also at the left side of
the mouth, where they number twenty-one, are narrow
and united at the base by a membrane ; those in con-
tinuation of the series below the mouth have only their
points free, and of these there are between thirty and
forty. The tentacular filaments at the entrance of the
branchial sac are delicate and numerous, situated not
much in advance of the branchial margin ; they are
very unequal in size, some being excessively short,
others of considerable length. The branchial tubercle
is quite minute, and forms a simple loop with the left
extremity turned inwards.

e/

The ovary is seen at both sides of the intestinal
loop ; on the left it has a lobulated appearance, on the
rio'ht it assumes a branched, tubular form as it becomes

o

united to the extremity of the wide oviduct. The
short, wide, caecal extremities of the male organ are
observed on the right side by the margin of the
ovary.

A. rubrotincta is a near ally to A. 'iiienfula, from
which, however, it is distinguished not only by its
colour, but also by several points of detail. The test
is thinner and less coarse than it is in the latter species,
and the tubes are better marked, particularly the

88 BRITISH TUNIC ATA.

branchial ; the oral lamina likewise differs in some
particulars, as do also the reproductive organs.

AVe have seen only one individual of this species,
and, as the description \vas drawn up some time after it
had been in spirit, it is probable that its colour may
have been much brighter than is represented, and
indeed may have been somewhat different in kind as
well as in degree. It would seem, too, that the blood
was probably red ; for the blood-channels were in
many parts clogged with a reddish matter.

6. Ascidia crassa Hancock.

(PI. XVII, fig. 4; PL XIX, fig. 3 ; PI. XX, fig. 5; and

fig. 17 in text.)

[A*et(li(i cratxa HANCOCK in Ann. Nat. Hist. (4) VI (1870),
p. 359.]

Bfnli/ broadly oval, a little depressed, deeply and
irregularly wrinkled, of a pale flesh-colour, adhering
by various parts to seaweeds. Apertures distant, ses-
sile ; branchial sub-terminal ; anal about half-way
down the side. Text very thick, hard, cartilaginous,
pellucid, irregularly and strongly wrinkled, of a pale
flesh-colour. " Mantle rose-coloured, deeper towards
the margins and over the alimentary canal ; the tubes
of the apertures short, particularly the branchial one,
which is sub-terminal; the anal is a little produced
and doubled over towards the left side. Tentacular
filaments numerous, well-developed, unequal in size.
Braiirliial sac minutely plicated, with obtuse papillae
alternately large and small, the stomata very small
and elliptical. Oral lamina delicately ribbed trans-
versely, and minutely pectinated ; by the side of the
mouth the pectinations are increased in size and re-
place the lamina.

Li'iiijtli two inches and a quarter; breadth an inch

and a half.

. — Between tide-marks, attached to seaweeds.

ASCIDIA CEASSA.

89

CHANNEL ISLANDS. — Jersey (DoJJ), in the collection
of the Rev. A. M. Norman.

First record,— Hancock, 1870; coll Dodcl [1869].

We have seen three specimens of this well-marked
species ; they were all from the same locality but had
been some time in spirit before they were examined ;
none of them showed any large area of attachment;
on the contrary, they all seemed to have been adherent
by various parts of the body to seaweeds, the remains
of which, including a piece of the cuticle of Liuninnna
digitata, being impressed into the surface of one of the
specimens.

FIG. 17. — Ascidia crassa. Natural size.

The test (fig. 17) is unusually thick and hard, and
is irregularly and strongly wrinkled ; it is pellucid and
of a delicate flesh-colour. The blood -channels are
numerous and are frequently crimson, especially those
appearing at the external surface, which have their
extremities considerably enlarged and irregularly
rounded or pyriform ; those observed at the inner
surface have the ultimate twigs slightly swollen and
fusiform. The enlarged crimson ones at the exterior
are not very plentiful and are mostly confined to the
vicinity of the apertures.

The mantle is well supplied with thick interwoven
muscular fibres, and varies in colour from a pale rosy
hue to crimson, the colour being intensified towards

B1UTISH TUXICATA.

the dorsal and ventral margins, over the alimentary
canal, and at the margin of the orifices. In one speci-
men a broad belt of brilliant crimson extended along
the dorsal margin, commencing in the branchial tube
and reaching to the bottom of the mantle. The anal
tube in this specimen was also of a deep crimson.
The branchial aperture is sub-terminal, being placed a
little towards either the left or right side ; in one of
the specimens it was inclined to the right, in the other
two to the left side. The anal tube, which is a little
more than half-way down the side, is well produced,
but is somewhat constricted and turned over towards
the left side.

The branchial sac (PL XVII, fig. 4) does not extend
backwards beyond the visceral mass; it is minutely
plicated ; the primary vessels are numerous and regu-
larly disposed, and are placed closer together than
usual. The branchial ties are large, with very stout
walls. The secondary vessels are short and wide
-the stomata being extremely short, wide, and ellip-
tical— many of them not extending the whole space
between the primary vessels. The longitudinal bars
are stout, with the branchial papilla? rather closely
set; the larger ones, at the intersections of the meshes,
are rather short and thick with the extremities obtuse ;
those placed between them are considerably smaller,
and are somewhat clavate, their extremities being a
little enlarged and rounded. The papillary membrane
is ample. The oral lamina (PL XIX, fig. 3) is not very
wide ; the anterior cleft extends further down than
usual and is delicately ribbed transversely, the ribs
being scarcely visible on the left side ; the margin is
minutely denticulated. In front of the mouth the la-
mina dies out, and is replaced for some short distance by
;i series of delicate tentacular points ; below the mouth
the lamina is verv narrow and indistinctly ribbed and

tj •'

pectinated. The tentacular points on the left side of
the mouth are narrow and minute, and arranged in a
closely set series ; they diminish in size backwards

ASCIDIA CEASSA. <>1

and terminate before the bottom of the sac is reached;
they are largest in the vicinity of the mouth. The
tentacular filaments at the base of the branchial tube
are about fifty, arranged in a single line on the pos-
terior surface of a muscular ridge or collar ; they are
rather closely set, moderately long and stout, but vary
in size. The branchial tubercle (PL XX, fig. 5) is
loop-formed, with the extremities turned first inwards,
then upwards.

The ovary is placed in the intestinal loop, and
appears at the left side as a congeries of lobules. The
male caeca were not observed; the vas deferent, how-
ever, was followed into the loop of the intestine, and
the minute branches were traced amidst the cellular
matter which coats the alimentary canal, but the caeca,
probably from their minute size, escaped detection.
Both sides of the visceral mass are densely covered
with cellular matter ; the cells are minute and do not
exhibit the usual dark nucleus when viewed with a
doublet.

Ascidia cmssa cannot very well be confounded with
any other known species ; the broadly oval form, the
sessile orifices, and hard, thick, cartilaginous test are
very characteristic ; but the branchial sac presents
probably the most distinctive feature. The walls of
this organ have a very peculiar appearance, on account
of the grooves of the minute plications being formed
into series of well-defined minute pouches by the
closely-set primary vessels, thus rendering it very
difficult to observe the secondarv vessels and the mi-

f

usually diminutive, elliptic stomata, And this diffi-
culty is increased by the excessive development of the
external vessels in connexion with the primary system
of blood-channels and the branchial ties, forming, as
they do, a complete network at the outside of the
branchial sac. It is only through the contracted
meshes of this network, or through the narrow
pouches on the inner surface, that the secondary
vessels and the stomata can be seen.

92 BRITISH TUNICATA.

7. Ascidia mollis Alder and Hancock.

(PL V, figs. 1-6 ; PL XVII, fig. 5 ; PL XIX, fig. 4 ;
and fio-s. 18 and 24- in text.)

o /

\_A.ycidta mollix ALDER and HANCOCK in Ann. Xat. Hist. (4)
VI (1870), p. 358.]

Bot.li/ ovate, tabulated, nearly black, attached by a
small portion of the side at the lower half. Apertures,
branchial terminal, anal from half to two-thirds down,
rather inconspicuous. Test thick, smooth, and soft to
the touch, rather shining, obtusely lobed, of a bluish or

Fi«. 18. — Ascidia mollis. Natural size.

brownish black colour, showing some reddish veinings
near the apertures. Mantle dark blue, with the apertures
red. Teiitin:nlfri' fila incuts numerous, rather slender,
varying in size, short, distant. Branchial sac with
stoutish papillae at the intersections of the meshes, and
comparatively slender intermediate ones on the longi-
tudinal bars. Oral lamina very narrow, strongly ribbed,
and pectinated at the margin.

Li'Htjth an inch and three quarters.

Halt. — [Below tide-marks ?]

IRELAND. — Birterbuy Bay, dredged (Brail;/), [and
Kilkieran Bay (More), 1869,] Connemara, Galway.

First record.— Hancock, 1870; coll. Brady [18(35].

Ascidia mollis is irregularly ovate, and is attached by
a small portion of the side so that the extremities are
free. The orifices are rather small and are slightly

ASCIDIA MOLLIS. 93

protuberant or tubular ; the branchial one is terminal
and the anal more than half-way down the body, and
at some distance from the ventral margin.

The test (Plate V, figs. 1-3, and figs. 18 and 24 in
text) is of a blackish colour more or less tinged
with brown or blue, it is thick, transparent, smooth,
glossy, and soft to the touch, and is somewhat irregu-
larly and obtusely lobed. The blood-channels (PL V,
fig. 4) are numerous, the twigs being rather slender
with the extremities much and suddenly enlarged,
rounded, and of a crimson colour, dotting the surface
all over with brilliant points, which are conspicuous
towards the apertures ; the twigs are pale crimson, the
stems yellowish.

The mantle (PI. V, figs. 5 and 6) is rather delicate and
has numerous, fine, muscular fibres running in various
directions, the transverse ones prevailing. The tubes
are short, but distinctly developed, with the aperture
red or crimson ; the branchial one is exactly terminal,
the anal is more than half way down the side, and is
turned towards the dorsal margin.

The branchial sac (PI. XVII, fig. 5) extends a little
way behind the visceral mass and is minutely plicated ;
the primary vessels are rather distant and are pretty-
regularly dispersed ; the secondary vessels are long, and
the stomata rectilinear with the extremities rounded.
The longitudinal bars are stout ; the papillae at the
intersections of the meshes are large and conical, the
intermediate ones being more slender, but of nearly
equal length ; the papillary membrane is rather incon-
spicuous. The external vessels in connexion with the
branchial ties and primary channels are well developed
and form a reticulation at the outside of the sac or sill,

O

and are studded all over with stoutish conical papilla?.
The oral lamina (PI. XIX, fig. 4) is much narrower
than usual and is strongly ribbed on the right side ; the
left side is almost smooth ; the maro-in is strono-ly

O O tj

pectinated. Below the mouth the lamina is so
narrow that it is difficult to determine whether it is

94 1',1,'ITISH TUNICATA.

pectinated or not, though the transverse ribs are con-
spicuous enough. The tentacular filaments of the
branchial tube are nearly equal in size, rather short,
and are widely separated from each other ; only twelve
were counted; but the specimen was probably im-
perfect in this respect.

The ovary is placed in the intestinal loop, and
appears at the left side as a lobulated structure ; a
few lobules are also seen at the right side. The male
cfeca are probably quite minute, they are not observed
at the surface, apparently being buried amidst the
cellular matter, a thin coating of which is spread over
the alimentary canal.

Var. carnosa var. nov. (PI. V, figs. 7-11.)

A rosy flesh coloured variety of this species occurred,
which may perhaps be specifically distinct ; but if so
colour alone will have to characterise it ; for we cannot
find any other feature of importance to distinguish it.
The tentacular filaments, however, are more numerous,
there being in the flesh-coloured variety about forty ;
while we have seen that the dark specimen examined
has only twelve ; but it is quite possible that, in this
instance, some of them may have been removed, or that
the specimen itself in respect to the tentacular filaments
is abnormal.

IRELAND. — Birterbuy Bay, Connemara (Brai

8. Ascidia plana Hancock.

(PL VI; PI. XVII, fig. 6; PL XIX, fig. 5; PL XX,
fig. 6 ; and fig. 10 in text.)

[A*ci<U« j ilana HANCOCK in Ann. Nat. Hist. (4) VI (1870),
p. 355.]

Both/ ovate, pellucid, yellowish horn-coloured, smooth,
except at the orifices, which are tuberculated ; attached
by the lower half. Apertures not much produced ; the
branchial subterminal, the anal about half-way down.
Test firm, rather thick, cartilaginous, smooth, hyaline,

ASCIDIA PLANA.

95

with numerous blood-channels. Mantle rather deli-
cate, with the apertures not much produced. Tenta-
cular filaments closely set, numerous, rather stout and
long. Branchial sac not quite so wide as the visceral
mass, with short rounded papillae at the intersections
of the meshes, and small intermediate ones on the
longitudinal bars. Oral lamina rather wide, ribbed,
and pectinated.

Length upwards of two inches.

Hal>. — [Below tide-marks ?]

FIG. 19. — Ascidia plana. Natural size.

ENGLAND. — Hastings, Sussex [, dredged] (Pn

CHANNEL ISLANDS. — Guernsey (Alder).

First record. — Hancock, 1870 ; coll. Bowerbank

[18(35].

The test of this very distinct species (fig. 19), which
has probably been confounded hitherto with A. inrntnl<t,
is thick, smooth, and firm, and the blood-channels (PI.
VI) can be distinctly observed in its hyaline, cartila-
ginous substance ; they are of a yellowish flesh-colour,
as seen in specimens in spirits, and are much sub-
divided, the terminal twigs being long and smaller so
as to be fusiform ; they are usually turned backwards ;
the extremities are rounded or only slightly pointed.

The mantle is rather delicate, and in preserved speci-
mens exhibits in a remarkable manner the vascular
reticulations filled with dark brown blood-corpuscles.

96 KEITISH TUXICATA.

The branchial sac (PL XVII, fig. 6) extends a little
below, and is rather narrower than, the visceral mass,
which passes beyond its boundary in the dorsal region ;
it is minutely plicated. The primary vessels are rather
distant and regular, and the stomata of the secondary
vessels rather wide, somewhat irregular and short, with
the extremities usually pointed. The longitudinal bars
are rather stout, with the papillae unusually short,
broad, and rounded ; they are alternately large and
small, the latter being 011 the bars between those at the
intersections of the meshes ; and all have a hispid
appearance, probably caused by the remains of cilia.
The papillary membrane is distinct but limited in
extent. The oral lamina (PL XIX, fig. 5) is well
developed, and is strongly and closely ribbed on the
right side, less strongly on the left; the margin is
minutely pectinated, there being usually three or four
small points on the membrane between those of the
ribs which are larger and stronger than the rest. The
lamina is smooth and little developed below the mouth.
On the left side of the oral orifice the row of tentacular
points is well defined ; it consists of about thirty large,
triangular, sharp-pointed, leaf-like processes. The
branchial tubercle (PL XX, fig. 6) is small, and is a
simple loop open in front. The tentacular filaments
of the incurrent tube are about forty in number ; they
are of moderate length and rather slender, closely
arranged in a single row and attached by the base for
some little distance upwards. As a few of the smaller
ones are more slightly attached than the rest, there is
somewhat the appearance of an interrupted second or
upper row of short filaments.

The ovary is a rather slender, branched organ,
ramifying over 'the upper portion of the left side of the
intestinal loop. The oviduct is seen as usual on the
right side following the sinuosities of the intestine ; it
is a wide tube, the rounded proximal extremity of
which, penetrating the intestinal loop, is seen at the
left side where it becomes connected with the ovary.

ASCIDIA PLAXA. 97

In the same region small caeca have been observed, but
they are very inconspicuous.

This species is evidently closely related to A. Alderi.
The loop of the intestine, as in it, is placed crosswise,
and the viscera are attached to the test by a mem-
branous process which passes into the intestinal loop,
just as a similar process does in that species. A.plana,
liOAvever, is sufficiently distinguished by the number
and arrangement of the tentacular filaments, the form
of the branchial papillae, and the character of the vas-
cular ramifications of the test.

We have seen only two individuals of this species,
and they had both been some time in spirit before
they were examined; so with respect to colour little is
known. But in consequence of the blood-corpuscles,
which are very numerous, remaining of a dark brown
colour, this is one of the best, if not the very best,
species for the determination of the vascular system.
The blood-channels can be traced on almost any part
of the organism, even to their minutest ramifications.

9. Ascidia Alderi Hancock.

(PI. XVII, fig. 7; PL XIX, fig. 6; and figs. 7 and 20

in text.)

[Ascidia Alderi HANCOCK in Ann. Nat, Hist. (4) VI (1870),
p. 356.]

Bod if irregularly ovate or pyriform, produced
towards the upper end, of a yellowish horn-colour
inclining to flesh- tint, with a few small, scattered
tubercles ; attached diagonally by the base and about
half way up the side. Apertures produced, distant,
with longitudinal tuberculated ridges ; the branchial
aperture terminal, the anal about two thirds down
the body, and inclined towards the left side ; ocelli
red. Test moderately thick, firm, transparent, with
the terminal twigs of the blood-channels appearing

7

98

BRITISH TUNK'ATA.

at the surface of a crimson colour; much enlarged
and widely fusiform. Mantle rather delicate, with
the apertures tubular, well produced. Tentacular
filaments slender, distant, not numerous. Brandt ia I
sac narrower than the visceral mass, with papilla? at
the intersections of the meshes and smaller ones on
the bars between them, all having on each side a
tubercular swelling. Oral lamina transversely ribbed
and pectinated.

Length upwards of two inches.

Halt. — Between tide-marks.

2S -f

FIG. 20. — Ascidia Alderi. Natural size.

CHANNEL ISLANDS. — Herm, Guernsey (Norman).
First record. — Hancock, 1870; coll. Norman [1865].

We have had the opportunity of examining but one
individual of this species, and as it had been for some
time in spirit little can be said respecting its colour.
All the other characters however were determinable ;
and they are sufficient to distinguish it from all known
species.

The test (fig. 20) was a little affected with parasitic
zoophytes; but the greater part of the surface w;is
quite free, and exhibited with great distinctness the
short, thick, deep crimson-coloured extremities of the
blood-channels, which are very numerous and much
subdivided ; the terminal twigs are considerably en-
larged and are pretty-regularly fusiform with the
extremity mucronated. The larger branches are gener-
ally of a pale yellowish red.

ASCIDIA ALDERI. 99

The mantle is rather delicate, with the muscular
fibres fine, and chiefly arranged transversely.

The branchial sac (PI. XVII, fig. 7) extends a little
below the visceral mass ; it is minutely plicated ; the
primary vessels are pretty regular, and the stomata
of the secondary vessels are rather long, with rounded
extremities. The longitudinal bars are as numerous
as the plications, and the papillas are of moderate size,
with the points rounded and produced some way in
advance of the lateral tubercular projections, which
give to them a shouldered appearance ; thence the
papilla? widen to the base ; the small intermediate
ones are formed exactly like the larger papillae. The
papillary membrane is distinctly developed. The oral
lamina (PI. XIX, fig. 6) is wide, and is divided in front
much further down than usual ; it is ribbed .011 the
right side, and the margin is strongly pectinated, the
points being much elongated immediately in front of
the mouth, and increased in number, as here the pecti-
nations, which are usually the produced extremities of
the ribs, have others between them that originate in
the membrane of the lamina itself. The tentacular
points, of which there are about twenty-seven, on the
left of the mouth, are large, wide, triangular, leaf-like
processes. The branchial tubercle is small, and in the
form of a simple loop open in front. The tentacular
filaments (fig. 7) at the entrance of the branchial sac,
are arranged in a single line, not on the usual muscular
band, but apparently on a delicate fold of the lining-
membrane ; there are about twenty slender, not very
long filaments placed considerably apart, with
occasional short intermediate ones making in all

o

about fifty.

The ovary is confined entirely to the left side of the
intestinal loop ; though the extremities of three or four
of the branches pass so far round the upper margin
of the intestine as to appear at the right side. The
organ is composed of numerous, irregularly-contorted
branches, some of which stray downwards as far as

100 BRITISH TUXK'ATA.

the stomach. The oviduct passes through the loop of
the intestine, and its rounded extremity is seen on re-
moving the lining-membrane ; here it becomes united
to the main branches of the ovary. The male caeca,
which are minute, numerous, and branched, appear at
the surface of the right side of the intestine ; a few

are also observed on removing the lining membrane

~

on the left side.

This interesting species is closely related to A. pi an a
as is proved by the transverse position of the intestinal
loop, which is arranged exactly as it is in that species ;
and moreover the visceral mass is attached to the right
side of the test by a membranous band which passes
through the loop of the intestine in the same manner
as it does in A. plan a. ; the band being adherent to the
lining-membrane at the left side of the intestine. It is
nevertheless readily distinguished from that species by
the arrangement of the tentacular filaments; bv the

ft/

form of the branchial papillae ; by the colour and pecu-
liar character of the blood-channels of the test; and by
several other minor features.

10. Ascidia rudis Alder.
(PI. VII, figs. 1-4; PL XVII, fig. 8.)

Axcidia rnilis ALDER in Ami. Nat. Hist. (3) XI (1863), p. 155
[; NORMAN in Eep. Brit. Assoc. 1867 (1868), p. 439, and
op. cit. 1868 (1869), p. 302].

Bod [i oblong or ovate, rather irregular, depressed,
greenish, attached largely by the side. Apertures dis-
tinct, the branchial terminal, the anal generally about
half way down; ocelli red, uniform. Text thick, coria-
ceous, coarse, wrinkled, and very slightly tubereulated,
sometimes nearly smooth. Mantle bluish-green, with a
yellowish tinge towards the upper part, the apertures
distinctly tubercular, the anal tube often much
extended, and entering into a kind of sheath in the
substance of the test. Tentacular "filaments few and

ASC'IDIA RUDIS. 101

slender. Branchial wte green, with stout papillae at
the intersections of the meshes, and frequently with
intermediate ones on the longitudinal bars. Oral lamina
transversely ribbed.

L<'it(/t/t about two inches and a half.

Hal. — Between tide-marks [and at low-water mark].

ENGLAND. — Hastings, Sussex (Blackett and Boirer-
banJc).

SCOTLAND. — Near the Whalsey Lighthouse, Out Sker-
ries, Shetland [, 18(51, the type specimens] (Norman).
[Between the Islands of Whalsey and Balta (Norman,
18(37).]

IRKLAND. — Belfast Bay, Antrim (Thompson}.

First record— Alder, 1863 ; coll. Norman [1861].

The test (PI. VII, fig. 1) is richly supplied with vas-
cular ramifications, the ultimate twio-s being1 verv

o o «/

numerous and minute ; and the mantle (PI. VII, fig. 2)
is delicate, with few and irregularly-disposed muscular
til >res

The branchial sac (PL VII, fig. 3, and PI. XVII,
fig. 8) is minutely plicated, and the longitudinal bars
correspond in number and direction to the plications,
which are distinctly defined. The papillae are large,
obtuse, and somewhat arched, with w ell-developed
intermediate small ones ; the larger are placed at the
angles of the meshes formed by the bars crossing the
primary vessels, and, as the meshes are rather small,
the papilla? appear crowded, especially as the inter-
mediate ones are of considerable size. The primary
vessels are pretty regular in size, but there are a few
larger at irregular intervals ; and on the outside of the
sac, they and other vessels which proceed from them,
chiefly at right angles, are strongly papillose. The
oral lamina is moderately developed and has the right
side ribbed, and the tentacular points, extending from
the left side of the mouth dowrnwards to the bottom of
the sac, are much larger than usual, and are, for the
greater portion of their length, free. The tubercle is

102 BRITISH TUXICATA.

a simple loop, the convexity downwards, and with the
right point a little prolonged, and there are about
twenty slender tentacular filaments at the base of the,
incurrent tube, pretty-regularly large and small alter-
nately. The nervous ganglion is nearly half way down
the mantle and is almost concealed by the gland in
connexion with it.

The ovary is a much branched and dendritic organ

J o

spread over the left side of the intestinal loop ; and the
male caeca are apparently confined to the same side,
but are for the most part buried amidst the coating of
cellular matter.

AscicUa nidi* bears a great resemblance to A. mentulu
in many of its characters, and may have been passed
over as a variety of that species. It differs, however,
in size and colour, in bearing small distant tubercles,
and in being much more largely attached. The anal
orifice, too, is, in the mantle, placed at the end of a
longish tube which enters into an internal sheath formed
by a thickening of the test, and is very little produced
outside ; the external opening varying in position
according to the length of the tube. In a variety from

o O */

Hastings which we owre to the kindness of Mrs. Blackett,
the tube is very much elongated within the test, and
opens externally at a short distance from the branchial
aperture. Usually, however, it is situated about half-
way down the test, pretty near to the position that it
occupies in the mantle. Some varieties of this species
approach, in appearance, large specimens of Axrhlui
depressa.

11. Ascidia venosa Midler.
(PI. VII, fig. 5 ; PI. VIII, IX, X; and fig. 4 in text.)

Ascidia venosa MULLER Zool. Dan. Prod. [1776], p. 225,
no. 2736, and Zool. Danica, I [1788], p. 25, pi. xxv,
f. 1—3; [LAMARCK Anim. sans Vert. ed. 1, III (1816),
p. 125; ed. 2, III (1840), p. 532; BRUGUIERE] Vers, I
[1789], p. 154, pi. Ixv, f. 4-6, in Encycl. Meth. ;
[THOMPSON in Ann. Nat. Hist. (1) V (1840), p. 93;]

ASCIDIA VENOSA. 103

FORBES and HANLEY Brit. Moll. I [1848], p. 31; THOMP-
SON Nat. Hist. Ireland, IV [1856], p. 359; [ALDER in
Rep. Brit. Assoc. 1866 (1867), p. 207 ; NORMAN in Sep.
Brit. Assoc, 1868 (1869), p. 302].

.Hutli/ elongated, sub-cylindrical, rather compressed.
attached by the base. Aperture*, branchial terminal,
anal a short way down the side. Test cartilaginous,
semi-transparent, smooth, thickly veined with red so
as to appear uniformly of that colour. Mantle crimson,
veined. Tentacular filaments stout and longish. Bran-
chial sac with rather obtuse primary papilla? at the
junction of the bars, and without secondary papilla?.
[Oral lamina wide and closely ribbed.]

Length an inch to an inch and a half.

Hab. — Below tide-marks; 40-50 fathoms in the
Shetlands.

ENGLAND. — Hastings, Sussex (Blackett and Bower-

SCOTLAND. — Hebrides (Forbes & Me. Andrew [ ; Alder,
I860] ). Isle of Sky and Shetland (Norman & Jeffreys).
[Middle Haaf off Out Skerries, and Haroldswick Bay,
Shetland Islands (Norman, 18(38).]

IRELAND. — Strangford Lough, Down, and Belfast
Lough, Antrim, dredged (Thompson}. Killery Bay,
Connemara, Galway (Thompson, Hall, and Forbes
[1840] ).

First record. — [" First distinguished as an Irish
species by Dr. J. L. Drummond ' (Thompson, 1840) ;
evidently the first British record.]

This beautiful species appears to be pretty-generally
diffused. It has not yet been met with, however, on
the east coast of England.

The soft pellucid rosy hue of the smooth test (PI.
VII, fig. 5) is very characteristic, and the deeper tone
of the blood-channels when looked at with a hand-lens
heightens the effect. These channels (PI. VIII) are
exceedingly numerous, and divide and subdivide until
their extremities become quite microscopic. A flat

104 Lh'ITISH TUXICATA.

wedge-shaped process projects from the inner surface
of the right side, and, penetrating into the loop of the
intestine, holds the visceral mass firmly in its position.
This process does not merely enter the loop, but is
attached to the walls of the alimentary tube throuo-h

v O

the agency of the mantle (PL IX, fig. 1), which is a
delicate membrane but sparingly supplied with mus-
cular fibres.

The branchial sac (PI. X) is more delicate than
usual and is minutely plicated ; the plica? however in
some of the specimens from Shetland are rather
obscure and difficult to observe. The primary vessels
are regularly arranged and pretty equal in size, a few
only being a little larger than the rest ; the secondary
vessels are rather longer than usual and the stomata
are widish, with the extremities somewhat pointed.
The papillae at the intersections of the longitudinal
bars are stout, conical, and obtuse, with occasionally a
few scattered, small, intermediate ones ; the papillary
membrane is strongly developed. The oral lamina (PL
IX, fig. 2) is wide, with the right side rather closely
ribbed ; it reaches to the bottom of the sac and retains
its width considerably below the mouth ; a narrow
lamina with denticulated margin extends from a little
above the mouth on the left side to the lower ex-
tremity of the sac. The branchial tubercle (PL IX,
fig. 2) is very minute and horse-shoe-like with the arch
downwards. The tentacular filaments, of which there
are between sixty and seventy, are arranged in a
single line ; they are long and slender, but vary con-
siderably in length.

The ovary (PL IX, fig. 4) is a branched tubular
organ ramifying over the left side of the intestinal loop,
covering the whole of this portion of the alimentary
tube with an open network of thickish contorted
branches. The testis (PL IX, fig. 4) is largely de-
veloped, and is spread over the entire left side of the
stomach and part of the intestine, covering a consider-
able portion of the other side of the alimentary tube

ASCIDIA VKNOSA. 105

(PL IX, fig. 3) ; it is composed of a vast multitude of
minute, obtuse, ramified caeca, crowded and packed
together in much confusion.

12. Ascidia producta Hancock.
(PI. XVII, fig. 9 ; PI. XIX, fig. 7 ; and fig. 21 in text.)

[Ascidia producta HANCOCK in Ann. Nat. Hist. (4) VI
(1870), p. 360.]

Body much elongated, pyriform, depressed, attached
by its entire length, of a pale green colour. Apertures
tubular, the branchial a little produced and turned
towards the ventral margin, the anal three-fourths
down near the ventral margin : ocelli red. Test rather
thick, pellucid, cartilaginous, covered with minute,
distant, conical papillae. M<nttl<>- of a full dark green
colour, delicate, with the branchial tube considerably
produced and terminal ; the anal short and turned
backwards. Tentacular filaments numerous, slender.
Branchial xa<- minutely plicated, with moderate-sized
papillae at the intersections of the meshes ; secondary
papilla? altogether wanting or rarely developed here
and there. Oral lamina narrow, pectinated, ribbed,
and tuber ciliated on the left side.

Lt a (~/flt two inches and a half.

Hal. — At extreme low water and below tide-marks.

SCOTLAND. — Hebrides [, dredged in the Minch]
(Norman).

IKELAND. — [Strangford Lough (Norman, 1869).]
First record. — Hancock, 1870 ; coll. Norman [186(5].

The body of this species is wide behind, much elon-
gated, and curved towards the ventral margin, narrow,
tapering in front. It is attached throughout its entire
length, and there is a thin, interrupted, marginal
expansion, widening the area of attachment. The
branchial tube is terminal, and unites imperceptibly
with the tapering extremity of the body ; it is turned

10G

BRITISH TUXICATA.

towards the ventral margin. The anal tube is three-
fourths down, a little within the ventral margin ; it is
turned backwards and is so short that in the contracted
state it appears merely as an eminence.

The test (fig. 21) is pellucid, thick, firm, and car-
tilao-inous, of a yellowish horn-colour and sparsely

^^ *•

covered with minute, sharply-defined, soft, conical
papillae, most conspicuous in young specimens. The
blood-channels are not very much subdivided, and they
terminate in rounded but not enlarged extremities.

The mantle is well supplied with delicate muscular
fibres, tapers gradually and is very narrow in front,
subsiding imperceptibly into the well-produced bran-
chial tube. The anal tube is more than three-fourths

FIG. 21. — Ascidia producta. Natural size.

down the ventral margin, and is short and turned
backwards.

The branchial sac (PI. XVII, fig. 9) is long and
narrow, tapering upwards, and extends very little
backwards beyond the visceral mass ; it is minutely
and somewhat obscurely plicated. The primary vessels
are rather closely set and variable in size, with a few
much larger than the rest at distant intervals. The
stomata are short and rectilinear, with the extremities
obtuse. The longitudinal bars are stout, with papillae
only at the intersections of the meshes; the papilla
are rather long and slightly shouldered, with the apices
pointed and a little produced. The papillary mem-
brane is obsolete. The oral lamina (PI. XIX, fig. 7) is
rather narrow, dies out a little below the mouth, and
is succeeded by a few minute transverse ridges which

ASCIDfA PRODUCTA. 107

are continued to the bottom of the branchial sac. It is
ribbed pretty-closely on the right side, and has the
margin strongly pectinated ; the points vary in size,
the larger ones are in continuation of the ribs, the
smaller, of which there are one or two between the
larger, originate in the membrane itself : the left side
is covered with large, curved, pointed papilla?, arranged
for the most part in transverse rows : the tentacular
points on the left side of the mouth are minute ; they
form a continuous series from a little above the mouth
to the bottom of the branchial sac. The branchial
tubercle is loop-formed with both extremities turned
to the left side. The tentacular filaments are numerous,
slender, and of moderate length ; they do not vary
in size and are rather closely set.

The ovary is branched and tubular ; a few of the
terminal branches appear at the end of the intestinal
loop on the right side, but the greater portion of the
organ ramifies over the inner margin of the loop on
the left side, where the branches become united to the
extremity of the wide oviduct, which, penetrating the
loop, appears at this side. The male casca are long,
sometimes a little branched, and usually bifid; they
are spread over the right side of the intestine, but are
somewhat obscured by the cellular matter which coats
the alimentary tube. There are a few casca also at the
other side of the intestine.

AschU'i in-nilndn evidently belongs to that group of
which A. iuoriinta and tl^ressa are typical; but has
many characters to distinguish it from all others.
Three or four mature individuals were procured ; but,
as they had all been for some time in spirit before
being examined, their colour could not be determined
satisfactorily. A few young specimens, however, which
had been preserved in a weaker spirit, retained their
original colour. In these the test was of a fine, pale
green, and the mantle and viscera of a full, dark green.
Mr. Norman thinks that the mature specimens, when
taken, were also of a green colour.

108

BRITISH TUXK'ATA.

13. Ascidia inornata Hancock.
(PL XVII, fig. 10; and fig. 22 in text.)

[Ascidia inornata, HANCOCK in Ann. Nat. Hist. (4) VI
(1870), p. 359.]

Ikxlij elongated, oval, depressed, attached by the
whole side, of a watery horn-colour. Ap^rfures a little
produced, with longitudinal ridges or folds; the l>rau-
cliial sub-terminal, the anal about half way down.
Test rather thin, cartilaginous, transparent, with a
few minute papillae and some scattered agglutinated
particles of sand and shells, chiefly towards the border

FIG. 22. — Ascidia inornata. Natural size.

of attachment. Mantle well supplied with interwoven
muscular fibres. Tentacular filaments numerous and
rather stout. Brandiial sac narrow, with large papilla?
at the intersections of the meshes, and small inter-
mediate ones on the longitudinal bars. Oral lamina
wide, strongly ribbed ; margin pectinated and bordered
on the left side with a band of tubercles.

Length nearly two inches.

Hob.—?

EXGLAND. — Hastings, Sussex (Bowerbank).
First record. — Hancock, 1870 ; coll. Bowerbank.

We have seen only a single individual of this species,
and, as it had been some time in spirit before it was
examined, not much is known respecting its colour.

The test (fig. 22) is thin, firm, and elastic, and of a
transparent watery horn-colour,, with a few very minute,
scattered papilla?, and here and there, spread over the

ASCIDIA IXdlfXATA. 1U9

surface, are some adherent particles of sand and shells,
which become accumulated towards the border of the
attachment. It is somewhat depressed, is attached by
the entire side, and there is an irregular, thin, marginal
expansion. The apertures are slightly tubular, with
smooth longitudinal folds or plaits ; the branchial,
being turned towards the free or upper side, is sub-
terminal : the anal is a little more than half way down
the ventral side. The blood-channels are of a pale
yellow colour, much branched and pretty-evenly dis-
tributed over both the external and internal surface of
the test. The main branches are large, and the ex-
tremities of the terminal twigs are rounded but not
enlarged.

The mantle is narrower than the visceral mass and
projects very little backwards beyond it. The mus-
cular fibres are well developed, and are interwoven;
the longitudinal and diagonal ones are inconspicuous,
but the transverse are the most numerous and are
closely netted. The tubes are short, but rather wide ;
the anal, projecting from the ventral margin a little
more than half way down, is turned forward ; the
branchial is turned a little upwards or towards the
left side.

The branchial sac (PL XVII, fig. 10), which, like the
mantle, is not so wide as the visceral mass, at least as
it appears in the contracted state, extends backwards
very little beyond the stomach. It is minutely plicated;
the primary vessels are rather distinct, nearly equal in
size, and regularly disposed; the stomata are rather
long, rectilinear, with the extremities usually a little
pointed. The papilla? of the intersections are large
and unusually long, with the sides almost parallel;
but are shouldered near the summit and have their
apices rounded. There are intermediate tubercles on
the longitudinal bars, which, though very much smaller,
are of the same peculiar form as the primary. The
papillary membrane is moderately developed. The oral
lamina is wide and strongly ribbed on the right side,

110 BRITISH TUNICATA.

and less strongly on the left ; the margin is strongly
pectinated, with one or more points on the membrane
between those of the ribs which are large and stouter
than the rest. The margin on the left side is bordered
with a rather wide band of large, curved, pointed,
papillae ; they are mostly irregularly disposed, but the
largest, which are the lowest down, are arranged with
considerable order in a doable row. Near the month
they are much crowded. The belt of tentacular points
on the left side of the mouth is advanced for some
little distance in a straight line upwards ; in all there
are about twenty rather large points. Below the mouth
the oral lamina gradually dies out and is succeeded by
a few minute diagonal plaits or folds. The branchial
tubercle is looped-formed, with the left extremity
turned outwards. The collar of tentacular filaments
is placed very little in advance of the branchial margin ;
they are numerous, closely-set, rather stout and long,
with their bases adherent to the mantle for some dis-
tance upwards ; a few smaller ones are interspersed,
which, bending forward in front of the others, give
somewhat the appearance of an anterior or second
row.

The ovary is confined to the left side of the alimen-
tary tube ; it is composed of ramified tubes which are
spread over the inner margin of the intestinal loop,
forming there a small patch of involved branches.
The male casca are wide and obtuse, frequently irregu-
larly lobed, but usually bifid ; they coat the greater
portion of the right side of the alimentary tube, but
do not extend to the posterior extremity of the stomach.
The cells spread over the visceral mass are large, with
a dark conspicuous nucleus in each.

A. inornata is allied to A. ^lel>eia, but differs from it
in many respects, and may at once be distinguished by
the narrowness of the mantle and branchial sac, and
likewise by the characters of the branchial papillae and
oral lamina.

ASCIDIA DEPRESSA. Ill

14. Ascidia depressa Alder and Hancock.
(PL VII, figs. 6-8 ; PI. XVII, fig, 11 ; PI. XIX, fig. 8.)

Ascidia depressa ALDER and HANCOCK in Trans. Tyneside
Nat, Field Club, I [1848], p. 201; FORBES and HANLEY
Brit. Moll. II [1849], p. 273 [; ALDER in Rep. Brit.
Assoc. 1866 (1867), p. 208; NORMAN in Rep. Brit, Assoc.
1868 (1869), p. 302].

Bod [i oblong-ovate, very much depressed, pale green,
attached laterally throughout its entire length by a
distinct expansion or disc surrounding the whole.
Apertures distant with small red ocelli ; the branchial
aperture terminal, the anal on a slight bulging about
two thirds down, rather inconspicuous. Text trans-
parent, granular or minutely tuberculated on the upper
surface, and thickened towards the disc ; under or
attached side smooth and very thin. Mantle yellowish
green ; of a deeper colour inclining to orange on the
lower part. Tentacular filaments numerous, in more
than one row. l!r« m'Jiidl xae with obtuse papillae.
[Oral lamina wide, ribbed on the right side.]

Length about an inch.

Hal). — Attached to the under-side of stones between
tide-marks (and sometimes extending to deep water ?) .

ENGLAND. — Common on the north-eastern coast.
[Falmouth, Cornwall (Cnrl-x, 1849).] Isle of Man
(Aider).

SCOTLAND.- -Hebrides (Alder, 180(3). [Island of
Housay, Out Skerries, Shetland, at low water (X<>'rin<n/,
1868).]

IRELAND. — C onnemara, G-alway (Brady) .

First record. — Alder and Hancock, 1848.

The test of this species (PL VII, fig. (3) exhibits
numerous blood-channels, the ultimate twigs of which
are minute, and have their extremities rounded, but
not enlarged. In old specimens the tubercles some-
times become nearly obliterated and the surface is
strongly wrinkled.

112 BRITISH TUXICATA.

The mantle (PI. VII, figs. 7 and 8) is thin and deli-
cate, with the muscular fibres fine and for the most part
transverse and diagonal.

The branchial sac (PL XVII, fig. 11) extends the
whole length of the body, and is minutely plicated,
and the secondary vessels are rectilinear, with the
extremities of the vessels obtuse ; the primary vessels
are pretty equal in size, and the longitudinal bars
somewhat more numerous than the plications. The
papillae are alternately large and small; with rounded
extremities, and the membrane in connexion with the
larger ones or those at the intersections is moderately
developed. The oral lamina (PI. XIX, fig. 8), which is
rather wide, is ribbed on the right side, and the smooth
or left side has a row of minute papillae just within
the free margin, extending from one end to the other ;
sometimes the papillae are double. The tentacular
points on the left side of the mouth are rather large.
The tubercle in front of the lamina is horse-shoe
formed, with the limbs turned forwards. The tenta-
cular filaments are very numerous, long, and much
crowded ; they are arranged in a broadish belt, having
the smaller in front, the larger behind, so that there
seem to be two or three rows of them.

The ovary appears on both sides of the intestinal
loop, but is most extensively developed on the left
side, where it assumes the form of a complicated en-
tanglement of small and contorted branches. The
cells covering the stomach are large.

15. Ascidia elongata Alder & Hancock.
(PI. XVII, fig. 12.)

[A*c i di a I'lonyata, ALDER & HANCOCK in Ann. Xat. Hist. (4)
VI (1870), p. 360.]

H»ilij elongated, slender, transparent, nearly colour-
less, attached slightly at the side of the base ; the
bnnn-li.inl aperture terminal, the <n/<if about two-thirds
down. Test hyaline, minutely tuberculated, the tuber-

ASCIDIA ELONGATA. 113

cles rather distant and pointed. Tentacular filaments
numerous, lon°'. and slender. Branchial sac with

O J

obtuse primary but no secondary papillae, the stomata
elliptical. Oral lamina smooth, ribbed, rather narrow.

Length about two inches ; breadth about half an
inch.

Hab. — Deep water ?

ENGLAND. — Sealiam Harbour (Hodge).
First record. — Hancock, 1870 ; coll. Hodge.

The test of this species is extremely hyaline, and
contains numerous blood-channels, which are minutely
subdivided, the ultimate twigs terminating in rounded
extremities.

The mantle is well supplied with delicate muscular
fibres, transverse, longitudinal; and diagonal ; but they
are not arranged with much order.

The branchial sac (PI. XVII, fig. 12) is long and
narrow, extending the whole length of the body ; it is
minutely plicated ; the plica3 are, however, so shallow
and obscure that they might easily lie overlooked, but,
on examining the outside of the sac, they are obvious
enough. The primary vessels are pretty regular ; but
the secondary vary considerably, some being very wide,
others comparatively narrow, arising from the irregu-
larity of the stomata which not only vary in size but

«/ «./ i/

also in form. They are usually wide and short, fre-
quently sharply pointed at the ends, and sometimes
with one end pointed and the other rounded, so as to
have an elongated ovate form ; some extend almost
the whole breadth of the space between the primary
vessels, others not half that space ; their width, form,
and irregularity being very characteristic. The papillae
on the longitudinal bars where they intersect the
primary vessels resemble those of A. aculeata ; but they
are shorter, thicker, more obtuse, and the lateral
tubercles are less prominent ; the papillary membrane,
also, is more extensively developed, and there are no
intermediate small papillae. The oral lamina is rather

8

114 BRITISH TUNICATA.

narrow, and is ribbed on the right side : the tubercle
is minute , and in the form of a loop open in front ; the
extremities are pointed. The tentacular filaments are
very slender, long, and numerous ; they do not vary
much in length and are closely set in a single line,
but have in front a few quite short filaments. The
oral lamina has the fringe of tubercular points on the
left of the mouth well developed, the free points being
rather large.

The ovary is situated on both sides of the intestine,
but chiefly on the left side towards the upper extremity
of the loop ; it is a rather delicately-branched organ,
so arranged as to have the appearance of an open
reticulation. The male casca are very minute, and are
placed on the left side of the intestine and stomach ;
but it must be observed that in the specimen examined
the reproductive organs were not fully developed.
The cells coating the stomach are large.

This species is evidently related to A. aculeata, but it
is distinguished by many characters. Besides the very
elongated form, the attachment is different and the
test only slightly tuberculated. The tentacular fila-
ments are differently arranged, and the minute struc-
ture of the branchial sac is quite peculiar and alone
sufficient for specific distinction.

16. Ascidia aculeata Alder.

(PL VII, figs. 9-11 ; PI. XVIII, fig. 1 ; PL XIX,

fig. 9.)

Ascidia acuhata ALDER in Ann. Nat. Hist. (3) XI [1863],
p. 156.

Body ovate, depressed, greenish, attached more or
less by the side to sea-weeds or zoophytes. Apertures
nearly sessile, aculeated, the branchial terminal, the
anal one-third down the side. Test thin, transparent,
greenish or nearly colourless, covered with aculeated
tubercles most prominent on the upper or left side,
greenish, transparent, showing the reticula-

ASCIDIA AfTLEATA. 115

tions of the branchial sac and sigmoid intestine. Ten-
tacular filaments numerous, long, and slender. Bran-
dial sac with large primary and also secondary papillae,
the stomata long and rectilinear. [Oral lamina ribbed
on the left side.]

LeiKjtIt an inch to an inch and a half.

flab. — From between tide-marks to deep water.

ENGLAND.- -Tor Bay, Devon (Alder).

SCOTLAND. — Lamlash Bay, Arran (Carpenter}.

IRELAND. — Strangford Lough, Down (Thompson).
Connemara, Gal way (Brady). Ban try Bay, Cork
(Norman).

CHANNEL ISLANDS. — Guernsey (Norman).

First record. — Alder, 1S03 ["; coll. "many years

"i
ago ].

The test (PI. VII, fig. 9), which is thin, firm, and
transparent, is richly supplied Avith vascular rami-
fications, the minute terminal twigs having their
extremities simply rounded.

The muscular fibres of the mantle (PL VII, fig. 10)
are not very numerous and are irregularly disposed.

The walls of the branchial sac (PI. VII, fig. 11, and
PI. XVIII, fig. 1) are minutely plicated, and the
secondary vessels are rather long, the stomata being
elongated and rectilinear with rounded extremities ;
the primary vessels are comparatively delicate, and
placed further apart than usual. The longitudinal
bars are rather more numerous than the plications, and
they support at the intersections large, conical papillae,
generally with small ones between them ; towards the
apex of each papilla, which is rounded, there is at either
side a prominent tubercle, below which the papillae
widen downwards to the base. The extremities of the
papilla?, moreover, are curved downwards or involuted,
and thus the profile is fiddle-head-shaped ; the papillary
membrane is not largely developed. The oral lamina
(PL XIX, fig. 9) is wide with the right side ribbed, and
the margin of the left or smooth side is minutely and

116 1UMTLSH TUXICATA.

irregularly tuberculated. The tubercle in front of the
oral lamina is small and horse-shoe-like, with the
extremities rounded and turned upwards. ,The ten-
tacular points at the left side of the mouth, and those
in continuation of the oral lamina downwards on the
other side, are few and very large. The tentacular
filaments are arranged in a widish, crowded collar, in
which they are small in front, and lono- and slender

t/ o

behind.

The principal portion of the ovary is spread over
the left side of the intestine ; there are a few branches,
however, at the upper part of the loop on the right
side. It is composed of numerous, irregular, and
somewhat confused ramifications of no great size.
Male caeca appear on both sides of the alimentary tube,
but are most numerous at the right side, where they
extend to the stomach, over which there is a coating
of large cells.

This species comes nearest to A. depressa, but is less
depressed, less loosely attached, and without the mar-
ginal disc dividing the upper from the under surface.
The test is more uniformly thin, and has stronger and
more sharply-pointed tubercles. The apertures are
also less distant. The tubercles are frequently com-
pound, bearing several aculeations. This is probably
the " Ascidia mamillaris, Delle Chiaje," of Thompson's
' Natural History of Ireland,' but we think not of
Delle Chiaje, judging from his figure.

17. Ascidia amoena .sy>. nor.

(PI. XI, figs. 1 and 2 ; PL XVIII, fig. 2.)

Bod n oval, semitransparent, greenish, largely at-
tached by the right side ; the upper slightly gibbous.
Branchial aperture a little way down the side, tubular;
anal about two thirds down, not very prominent.
7V*f transparent, nearly colourless, thickly covered
with stout, conical tubercles, generally with one, some-
times with two, small papilla? at the apex. Tentacles

ASCIDIA AMiEXA. 117

numerous, long, and slender, Branchial *<«> minutely
laminated, with broad, stout, conical papillae at the
intersections of the meshes, and smaller intermediate
papillae. Oral lamina with the right side ribbed, and
lobed or widened over the mouth.

Length about an inch.

Hali. — Deep water.

ENGLAND. — Sealiam Harbour, Durham (Bodge).
CHANNEL ISLANDS. — [Guernsey] (Nornuni).
First record. — Hancock [; coll. Gorman, 1870].

We have seen only two individuals of this rather
critical species (PI. XI, figs. 1 and 2) ; it is undoubtedly
closely allied to A. aculeata, from which it is chiefly
distinguished by the more simple character of the ex-
ternal tubercles (PL XVIII, fig. 2), which occasionally
support two papillae or spines, but usually only one,
while in A. aculeata. they bear several aculeations.
The branchial papillae, also, differ considerably in the
two species ; they are more pointed in A. amcena than
in A. aculeata; and in the former there is on either
side near the base a tubercular swelling ; but similar
swellings in the allied species are close to the apex ;
in the former, too, the profile view of the papillae is
more squat and not so decidedly fiddle-head-shaped as
it is in A. aculeata. The ovary is very similar in both
species.

18. Ascidia plebeia Alder.
(PI. XI, figs. 3-5 ; PI. XVIII, fig. 3.)

Ascidia plrlria ALDEK in Ann. Nat. Hist. (3) XI [1863],
p. 155 [, and Rep. Brit. Assoc. 1866 (1867), p. 207 ;
NORMAN in Rep. Brit, Assoc. 1868 (1869), p. 302].

Body oblong, slightly scabrous, attached for nearly
the whole length, greenish. Apertures, branchial ter-
minal, produced, conical ; anal about two-thirds down,
slightly raised; ocelli small, red. Test thin, trans-
parent, roughish, with small papillae and sparsely

118 BRITISH TTXK'ATA.

covered with fragments of shells and sand, especially
towards the attached part. Mantle yellowish green.
Tentacular filaments numerous and stont. Branchial
sac with papillae at the intersections of the meshes,
and occasionally small intermediate ones on the longi-
tudinal bands or bars. Oral lamina plicated on the
right side.

Lengtli. — An inch and a half to two inches.

Hub. — Deep water.

ENGLAND. — Mr. Alder has met with one or two
Asc.idiK from the coasts of Northumberland and Dur-
ham which we are inclined to refer to this species.

SCOTLAND. — [Hebrides (Alder, 1865).] Outer Haaf,
Shetland, dredged (Norman & Jeffreys). [Forty miles
east of Whalsey Lighthouse, 1861, the type specimens
(Norman, 1868).]

First 'rrford. — Alder, 1868 [: coll. Norman & Jeffreys,
1861].

The test of A. j_>l<jn-ia (PI. XI, fig. 3), which is rather
thin, soft, and transparent, is amply supplied with
blood-channels, the terminations of the small branches
being slightly enlarged and rounded. The mantle is
delicate and is but scantily provided with muscular
fibres which are scattered and irregularly disposed.

The primary vessels of the branchial sac (PL XI, fig.
4, and PL XVIII, fig. 3) are pretty regular in size and
arrangement, and the secondary have the stigmatic
meshes rather large. The minute plications of the
vascular web are wide and shallow, and there is
usually a longitudinal bar corresponding to each pli-
cation. The reticulation formed by the liars and the
primary vessels is rather coarse and nearly equilateral,
and the papilla? which are at the intersections are con-
sequently somewhat distant ; they are large, conical,
and obtuse ; there are also here and there minute
papillae on the bars between the large ones, and the
membrane in connexion with the latter is rather limited
in extent. The oral lamina is widish, and the ribs,

AS01DIA PLEBEIA. 119

which are not numerous, are confined to the right
side ; it dies out rather abruptly immediately behind
the mouth ; the margin is entire. The tubercle is re-
markably minute and forms a simple loop with the
convexity turned downwards, but the left extremity is
occasionally bent inwards. The tentacular filaments,
which are long, stout, and pretty equal in size, are
very numerous and crowded, and are arranged in a
single series forming a regular collar.

The ovary is a rather delicate, dendritic organ, and
ramifies over both sides of the intestinal loop, but the
greater portion is at the left side, and though the rami-
fications are spreading they do not reach so far down-
wards as the stomach. The minute caaca of the male
organ appear to be confined to the right side of the
alimentary tube ; at least, none were observed on the
other side. The species is also remarkable for the
large size of the cells coating the stomach, as similar
cells do in all the members of the genus.

This species has affinities with A. aculeata and A.
depressa. From the first it may be known by its more
elongated form and more prominent apertures, and
by the papillae of the test being smaller, fewer, and
not echinated ; from the latter by its thinner test and
smaller area of attachment, as well as by the absence
of the thickened margin or disc which divides the
upper from the lower surface in that species ; and
from both it may be distinguished by the fragments of
shells with which it is usually more or less covered.

19. Ascidia sordida Alder and Hancock.

(PL XI, fio-s. 6 and 7 ; PI. XII ; XIII ; XVIII, fig. 4 ;
PL XX, fig. 7 ; and fig. 2 in text.)

Ascidia prnuum MACGILLIVRAY, Moll. Aberdeen [1843], p.

312.
Ascidia rustica DALYELL Rare Anim. Scotland, II [1848],

p. 143, pi. xxxiv, fig. 6 ; pi. xxxv (young ? ).
[Non Ascidia prnniim MULL, nee A. rustica MULL. ZooL

Danica (1788).]

120 BRITISH ITXK'ATA.

Ascidia sordida ALDER and HANCOCK in Trans. Tyneside Nat.
Field Club, I [1848], p. 199; FORBES and HANLEY Brit.
Moll. II [1849], p. 372; [ALDER in Nat. Hist. Trans.
Northumb. and Durham, I (1865) p. 11 ; NOEMAN in Eep.
Brit, Assoc. 1868 (1869), p. 302].

Bud)/ longitudinally ovate, of a semi-transparent
yellowish white, generally blotched with red, nearly
smooth, but with an uneven surface, and rather rugose
towards the apertures; attached by a narrow base.
Apertures terminal and not far apart, slightly tubular,
more or less echinated or tuberculated ; ocelli small
and inconspicuous. Test (PL XI, fig. 6) transparent,
vitreous and colourless, with a few longitudinal wrin-
kles, rather tough, and very slightly contractile.
Mantle yellowish, usually blotched and spotted with
crimson on the upper part. Tentacular filaments
slender [, alternately large and small]. Branchial sue
with rather small papillre. Oral lamina smooth.

Lenntli an inch and a half to two inches.

Hfil>. — In the Coralline zone, N.E. England, usually
attached to zoophytes [ ; in deep water, on dead shells,
N.E. Scotland; on sandy ground, Shetland].

ENULAXD. — On the north-east coast. Cullercoats,
Northumb., plentiful. [Falmouth, Cornwall (CV/,-.s,
1849).]

SCOTLAND.— On the north-east coast. Firth of Forth
(Dah/ell). Aberdeen (Macgillivray). AYick, Caithness
(Peacli). Shetland (Norman & Jeffreys [; Me Andrew
& Forbes] ). [East of the Isle of 'Balta, Shetland
(Normiin, 18(58).]

First record. -- Alder and Hancock, 1848 (Mac-
gillivray, 1843, as Ascidia prunum).

The mantle (PI. XI, fig. 7, and PI. XII, fig. 1) of A.
sordida is rather stout and is of a pale transparent
yellow colour, usually with scattered circular spots or
blotches of crimson towards the upper part ; and
freckled with opaque white, sometimes thickly accu-
mulated so as almost to obscure the alimentary tube,

ASCIDTA SOBDIDA. 121

and there is generally a large oval white spot between
the tubes concealing the ganglia. The tubes are short
and conical ; the branchial one is exactly terminal, the
anal is placed near to it a little way down the ventral
margin. The muscular fibres are interwoven on the left
side ; on the right side a few fibres pass inwards from
the margins, particularly from the bases of the tubes.

The branchial sac (PI. XII, fig. 2, and PI. XVIII,
fig. 4) is co-extensive with the mantle, both terminating
near to the posterior margin of the visceral mass. It
is minutely plicated ; the primary vessels are numerous,
regularly disposed, and a little variable in size ; the
stomata are somewhat elliptical, with the extremities
pointed. The longitudinal bars are stout, with rather
small obtuse papillae at the intersections ; there are no
small intermediate ones. The papillary membrane is
distinctly developed, though not conspicuously so.
The oral lamina (PI. XII, fig. 2) is wide and smooth,
and terminates at the right side of the mouth, which is
situated near the bottom of the branchial sac, usually
in the midst of a large irregular red blotch which
extends to the extremity of the lamina : there are no
tentacular points on the left of the mouth. There are
between fifty and sixty tentacular filaments arranged
in a single line. The branchial tubercle (PI. XII, figs.
'2 and 3, and PI. XX, fig. 7) is oval, placed lengthwise
with the extremities of the loop usually turned towards
the endostyle, though sometimes they are both in-
curved.

The ovary (PL XII, fig. 3, and PI. XIII, fig. 1) is
situated at the left side of the visceral mass ; it is
branched in a radiating manner from the centre of the
intestinal loop, the branches extending over the whole
of this portion of the alimentary tube. The male ca3ca
(PL XII, figs. 1 and 4; and PL XIII, fig. 9) are large,
numerous, irregularly lobulated or branched, and fre-
quently bifid, with the extremities obtuse. They are
distributed over both sides of the looped portion of the
intestine, but on the right (PL XII, fig. 1) are most

122 B1UTISH TUXICATA.

conspicuous, and have a beautiful dendritic appearance,
their white colour contrasting* well with the brown tint
of the cellular matter which is spread over the greater
portion of the alimentary tube : the cells of this
matter are moderately laro'e.

e/ o

This is the most common species on the north-east
coast of England, where it is brought in abundantly on
the fishermen's lines, frequently in groups of several
together. They are usually attached to Gemellaria
lorwulata or some other zoophyte, and in the young
state frequently cover it like a cluster of grapes. A
group of this kind is represented by Sir John G.
Dalyell in Plate xxxv of his ' Rare and Remarkable
Animals of Scotland.' When young they are hyaline
and almost colourless. From the narrowness of the
base of attachment the individuals have not always
room to expand ; in this case the lower part of the test
is lengthened with a flat pedicle sometimes as long as,
or even longer than, the body of the animal. Modio-
lui'in, marmorata is often found imbedded in the test.

Mr. Norman informs us that when dredging in 73
fathoms water off North Uist in Shetland, a large
dredge came up filled with Ascidia soi'<li<ln, in such
quantities that some hundredweights of them had to
be thrown back into the sea.

20. Ascidia canina Miiller.
(PL XVIII, fig. 5; PL XX, fig. 8.)

Ascidia canina MULLER Zool. Dan. Prod. [1776], p. 225, no.
2734, and Zool. Danica, II [1788], p. 19, pi. Iv, f. 1-3;
[BRDGUIERE] Vers, I [1789], p. 152, pi. Ixiv, f. 1-3, in
Encycl. Meth ; [THOMPSON in Ann. Nat. Hist. (1) XIII
(1844), p. 434;] FORBES and HANLEY Brit, Moll. I [1848],
p. 31 ; THOMPSON Xat. Hist, Ireland, IV [1856], p. 360 ;
[MclNTOSH in Proc. R. Soc. Edinb. V (1866) p. 605].

Pliallnxta canina SAVJGNY Mem. Anim. sans Vert,, pt. 2
[1816], p. 171.

Body elongated, subcylindrical, rather soft, adhering
at the base by fibrous prolongations of the test.

ASCID1A CAXIXA. 123

Apertures reel, tuber'culated or echinated longitudinally,
the branchial terminal, the anal on a short tube at a
little distance below. Ocelli inconspicuous. Text thin,
sub-pellucid, yellowish white or horn-coloured, with a
tinge of red, finely hispid, minutely but irregularly
tuberculated and a little aculeated at the upper part.
Mantle red above and yellowish below, the intestine,
shining through, of a greenish colour. Tentacular
filament* short. Branchial sac with small papillae.
Oral lamina with a strong smooth plait.

Leiif/tJ/ three or four inches.

Hah.- ?

EXULAXD. — Solent Channel, Hants (Jain ex and
Forbes). [Falmouth, Cornwall (Codes, 1841)).]

SCOTLAND. — North Uist, Outer Hebrides (McLitosh).
Kirkwall Bay, Orkney (Forbes and Goodxir).

IKELAXD. — Strangford Lough, Down (Thompson).
Clew Bay, Mayo (Thompson, Ball, and Forbes).

First record— Thompson [1844].

The blood-channels enter the test near to its base,
and are confined to the lower portion, where there
are a few large trunks which give off a limited number
of slender branches, but none of them reach halfway
up the test, and the alternate twigs end in slightly-
enlarged elliptical casca.

The mantle is very delicate, transparent, and but
feebly supplied with muscular fibres, which are irregu-
larly disposed.

The branchial sac (PI. XVIII, fig. 5) is long and
extends to the bottom of the mantle, and has the
alimentary tube on the right side. The loop of the
intestine is considerably elongated in the upward or
antero-posterior direction, and the rectal portion is
rather long and wide. The branchial membrane is
rather delicate and minutely plicated ; the primary
vessels do not vary much in size, and are pretty
regularly disposed. The longitudinal bars stand well
up from the surface and are rather far apart, there

124 BBITISH TUNIOATA.

being usually a bar corresponding to every second fold
of the respiratory membrane. The meshes formed by
the bars crossing the primary vessels are much wider
than long ; the papillae at the intersections are short
and obtuse and the papillary membrane is narrow.
The rectilinear stigmata of the secondary vessels are
rather long. The oral band is well developed, and is
for the most part smooth, but is imperfectly ribbed in
the vicinity of the mouth. The branchial tubercle
(PI. XX, f. 8) is rather large and strongly involuted,
and there are seventeen or eighteen moderately long,
equal, delicate, tentacular filaments a little above the
entrance of the branchial sac.

The reproductive organs are placed on both sides of
the alimentary tube, but the ovary, which is a large,
dendritic and folliculate organ, is arranged round the
margin of the intestinal loop and sends ramifications
to both sides of it. The testicular caeca are of the
usual form, but are extremelv minute; thev are distri-

e/ *-

buted over each side of the intestine. The ras deferens
and oviduct are seen on the right side following the
contortions of the intestine, and both terminate close
to the anal orifice.

-1. Ascidia obliqua Alder.

(PI. XI, fig. 10; PL XVIII, fig. (3.)

Axciilia olliqua ALDER in Ann. Nat. Hist. (3) XI [1863] , p. Io4.

Body broadly ovate, light horn-coloured, rather
rugose when old, but not tuberculated, nearly smooth
when young, attached diagonally at the base and par-
tially at the side, leaning over towards the dorsal
aspect. Apertures not far apart, tubes conical, with
longitudinal grooves corresponding to the angles of
the lobes ; the branchial not quite terminal, the anal
median. Ocelli inconspicuous. 2W rather thin, trans-
parent, sometimes a good deal covered with zoophytes.
TentiirvJitr jilirnients slender. Bwncltiul sac with large,
subclavate, papillae. 0/v// linni/a transversely ribbed

ASCIDIA OBLIQ.UA. 125

Length about two inches.
Ual>. — Deep water.

SCOTLAND.- — Outer Haaf, Shetland [the type speci-
mens], dredged in from 40 to 50 fathoms [; between
the islands of Whalsey and Balta, Shetland, in about
the same depth of water] (Norman}.

First record.— Alder, 1863 ; coll. Norman [18(51].

Three examples of this species were obtained by
Mr. Norman in different stages of growth, the largest
measuring a little above two inches in length. A
somewhat larger specimen was sent to us from Sweden
by Professor Loven, with the name of Ascidia mentida
attached. A. obliqua has probably hitherto been over-
looked as a variety of that species, but it is perfectly
distinct ; the form is more ovate, the test very much
thinner and attached obliquely at the base, the aper-
tures are more distinctly grooved, and the branchial
sac has not the intermediate papillae, nor is it reflected
upwards at the base, as in A. mentula. It appears to
be a northern species.

The test (PI. XI, fig. 10) does not appear to be well
supplied with blood-channels, as is the case in
A. me'iitidn, and the branchial sac (PI. XVIII, fig. 6) is
minutely and obscurely plicated longitudinally, the
plicae being wide and shallow ; there seem to be two
or three longitudinal bars to each plait. The papilla?,
which are large, with the extremity rounded and a
little enlarged, are not numerous, the reticulations
formed by the bars crossing the primary vessels being
rather coarse, and the papillary membrane not nearly
so extensively developed as is usual. There are about
seventeen slender, distant, tentacular filaments, with
a few small intermediate ones. The oral lamina is
broad, with the right side delicately ribbed, the ribs
being rather distant; and the branchial tubercle is
broad and loop-formed, with the concavity turned
upwards. The right hand extremity is a little bent
outwards.

126 BRITISH TUNICATA.

22. [Ascidia Morei sp. iwv.*']
(PL XIV, and fig. 23 in text.)

[Hod t/ ovate, of a pellucid yellow colour blotched with
red, attached by a rather broad base. Apertures sessile
or slightly tubular, near together, turned a little to the
left side, the branchial nearly terminal, the anal a little
way down towards the ventral margin. Test rather
thick, firm, cartilaginous, transparent, colourless,
wrinkled delicately lengthwise and minutely punctate.
Mantle rather stout, semi-transparent, speckled with
opaque white powder, the tubes and the upper ex-
tremity suffused with carmine. Tentacular filament*
numerous, long and slender, of nearly equal size, dotted
with opaque white. Branchial sac with strong rods,
the papillary membrane rather contracted, the upper
border, at its junction with the rod, abruptly enlarged.
Oral la ni'ui K wide, margin entire, ribbed at the base of
the right side.

Length about three quarters of an inch.

Hall. — Deep water ?

IRELAND. — North Wall, Dublin, cast ashore (Mow).
First record. — Hancock ; coll. More, 1870.

The minute punctations of the test (PL XIV, figs-
1 and 2) give to the outer surface of this species a
granular appearance, seen only with a powerful lens.
The blood-channels are few, and are principally confined
to the lower extremity.

The red spots on the mantle (PL XIV, figs. 4 and 5)
are occasionally confluent, forming a brilliant carmine
blotch extending over the greater portion of the pallia!
lobe. On both sides there is a delicate powder of

* This is the last species which Mr. Hancock examined. It is not de-
scribed in the MS., having- been collected after he had ceased to work at that.
The description is drawn tip from the pencil notes by the side and at the
back of his drawings, where he has recorded the date of collection, i^ird
October, 1870, and the date of his microscopical examination of the speci-
mens, 27th April, 1871.

ASCIDIA MOREL

±(

opaque white. The muscles are strongly developed and
glisten amidst the spots of colour. The oral lamina
(PL XIV, fig. 6) has the cleft in front short; it is widened
a little at the mouth and terminates rather abruptly
immediately below it. Above the mouth, on the left-
side, there are three or four oblique plaits ; there is no
denticulation at the side. It is usually more or less
coloured with brilliant carmine, particularly at the base
and in the vicinity of the mouth ; the sides are paler,
the pale tint being continued to the margin. The ten-
tacular filaments are about forty in number ; they are

Position

of
oral lamina.

Position

of
endostyle.

FIG. 23. — Part of the branchial sac of Ascidia Morei, highly magnified.

closely set, colourless, hyaline, and are dotted with
opaque white. The branchial tubercle (PI. XIV,
fig. 3) is well developed, angular at the sides, lozenge-
shaped, and the convolutions are rather peculiar.

The primary blood-vessels of the branchial sac are
very regularly disposed and do not vary much in size.
The secondary blood-channels are peculiar ; they are
exceedingly wide and irregular, the stomata being
short, elliptical, and irregular in size. They rarely
reach the whole width of the space between the
primary vessels, and are not infrequently quite
minute; the result is that the whole of the tissue
has the appearance of a perforated membrane which is

128 BRITISH TUXICATA.

minutely and rather deeply plicated. The rods are
strong, with the papillary membrane rather contracted,
but having the upper border, at its junction with the
rod, abruptly enlarged so as to assume the appearance
of an obtuse tubercle.

The greater portion of the alimentary canal is
covered with vesicular matter, obscuring the organ ;
consequently the male vesicles could not be observed.
The ovary (PI. XV, fig. 7), as well as the oviduct, con-
tained white eggs.

This species is named after its discoverer, Mr. A. Gr.
More, of Dublin. Its nearest allies are Ascidia scabm
and A. '

23. Ascidia scabra Miiller.

(PI. XV, figs. 1-7 ; PI. XVIII, fig. 7 ; PI. XIX, fig. 10 ;

and fig. 1 in text.)

Ascidia scabra and aspersa MULLEE Zool. Dan. Prod. [1776],
p. 225, no. 2726, 2728, and Zool. Danica, II [1788], p. 33,
pi. IXY, f. 2, 3; [THOMPSON in Ann. Nat. Hist. (1) V
(1840), p. 94;] FORBES and HANLEY Brit. Moll. I [1818],
pp. 33, 35; THOMPSON Nat, Hist. Ireland, IV [1856],
p. 360; [MclNTOSH Proc. B. Soc. Edinh. V (1866), p.
605] .

Ascidia scabra FORBES and HANLEY Brit. Moll. I [1848],
p. 33, pi. C, f. 3; [NOKMAN Rep. Brit. Assoc. 1868 (1869),
p. 302].

[Ascidia scabra ? FORBES Rep. Brit. Assoc. 1850 (1851), p.
242.

Ascidia aspersa CARUS in Proc. Ashmol. Soc. I (1851), p.
266; ? ALDER Rep. Brit, Assoc, 1866 (1867), p. 207.]

Body suborbicular or ovate, a little compressed,
generally adhering largely by the side ; but rather
irregular in outline and area of attachment, Apeiimr^
sublateral, not far apart, forming short, broad, echi-
nated, reddish tubes. Test tough, transparent, colour-
less, more or less tuberculated, especially towards the
apertures; sometimes nearly smooth. Mmtfl? semi-

ASCIDIA SCABBA. 129

transparent, yellowish white, more or less blotched
with red and with minute opaque white spots ; a large
white spot between the apertures on the ganglionic
region. Tentacular filaments numerous, long, variable
in size, devoid of opaque white. Branchial sac spotted
with red, minutely plicated, with the stomata elliptical ;
the papillary membranes ample, with the thickened
margin narrow and projecting very slightly from the
front of the longitudinal rods. Oral lamina well de-
veloped, ribbed ; the left oral appendages, four or five
simple, diagonal, narrow ridges.

Lemjtli from three-quarters of an inch to an inch
and a quarter.

Hal). — On the under-side of stones, on shells and
fuci, in shallowish water, sometimes between tide-
marks.

ENGLAND. — Not uncommon on the south and west
coasts. Lulworth Cove, Dorset (Jeffreys], Plymouth,
Devon (Bate). [Scilly Isles (Cants, 1850).] ' Isle of
Man (Alder).

WALES. --Tenby, Pembroke; and Menai Straits,
Carnarvon (Aider).

SCOTLAND. — West coast (Furies). [Hebrides (Alder,
186(3). North Uist, Outer Hebrides (Melntosli, 18G5).
Island of Housay, Out Skerries, West Voe, Shetland
(Nonwni, 18(58).]

IRELAND. — [Irish Sea, not rare (Forbes).~\ Strang-
ford Lough, Down (Thompson [and Norman].) [Belfast
Lough, Antrim (Thompson, 1840). Clew Bay, Mayo
(Thompson, 185(3).] Killery Bay, Galway, on the
fronds of Laminaria. (Thompson, Bull, and Forbes).

First record. — [Thompson, 1840.]

A. scalra is considerably depressed and the test
(PI. XV, f. 1) is rather thick- and firm, and is generally
attached by the whole side, though somewhat variable
in this respect. It varies greatly in the degree of
tuberciilation, some individuals being strongly tuber-
cular or aculeated over the entire surface, while in

9

130 BRITISH ITXK'ATA.

others the tubercles are almost wholly confined to the

e/

tubes, where they are always most numerous, and fre-

V ti>

quently compound.

The mantle (PL XV, fig. 2) is delicate and is usually
tinged with yellow, sometimes with a rosy hue, and
is blotched with red on both sides ; the blotches, which
are rounded, become confluent on the tubes. The
freckling of opaque white is sometimes confined to the
track of the alimentary tube, and is accumulated in a
large spot in the ganglionic region ; in some specimens
nearly the whole mantle is suffused with red.

The branchial sac (PI. XVIII, fig. 7) extends to the
bottom of the test, and has the minute plications well
defined ; the primary vessels are regularly disposed ;
the stomata are elliptical, shorter than usual, and fre-
quently do not extend the whole width of the space
between the primary vessels, and they are occasionally
irregularly disposed; the papillary membranes are
ample, with the thickened free margin narrow, and
scarcely if at all projecting beyond the longitudinal
bar. The longitudinal bars are delicate, with the sus-
pended membrane rather wide. The oral lamina (PI.
XIX, fig. 10) is broad, with the right side strongly
ribbed and the margin entire ; it terminates at the
bottom of the branchial sac immediately below the

t/

mouth, where it is produced into an inconspicuous lobe
that appears to overhang the oral orifice. On the left
side of the mouth there are four or five, simple,
obscure, diagonal, ridges — the left oral appendages.
The tentacular filaments are numerous, varying from
36 to nearly 50 ; they are variable in size, are long
and slender, and devoid of opaque white. The bran-
chial tubercle is a simple loop, open in front, and occa-
sionally with the extremities turned a little inwards.

The ovary is a beautifully-branched, tubular organ,
ramifying over the left side of the intestinal loop :
the male organ is inconspicuous. The loop of the
alimentary tube forms a regular oval mass which lies
towards the dorsal region and extends from the bottom

ASCIDIA SCABRA. 131

of the pallial sac to nearly half way up ; the rectal
portion diverges to the base of the excurrent tube,
where it terminates in a wide anal orifice, with a
smooth reflected margin. The left side of the stomach
is thickly covered with vesicular matter which is

i/

extended over the intestinal loop, and this, as well as
the stomach and oesophagus, is yellowish, blotched,
and marked with red ; the rectum is hyaline.

We have followed the opinion of Professor Sars in
considering the AsciJni. ttsprrx<t of Miiller to be the
young of this species, which is extremely variable
both in form and colour. Specimens with the mantle
blotched with red are much more common than those
which have it all of that colour.

Axcidia x<:«/ti-« in some of its forms bears a great
resemblance to A. sordida, whose place it seems to
take 011 the south-west of Great Britain, though
generally found in shallower water, and sometimes
between tide-marks. It is smaller, more largely
attached, and more tuberculated than A. sor<UJ</, and
has the orifices situated rather more to one side ;
and moreover, while the latter belongs to the division
with the branchial sac papillose, A. scaltra has it iion-
papillose. Its closest allies, however, are [JL Morei,~]
A. <y /#»/*, and A. Nonunni; but from each of these it
has many distinguishing features.

[Var. albida Nobis.] (PI. XV, figs. 3 and 4.)

[Avidia albida ALDER and HANCOCK in Trans. Tyneside
X. F. Club, I (1848), p. 200.]

A colourless variety not infrequently occurs, entirely
devoid of blotches and spots, except those of opaque
white. This pretty variety might easily be taken to
be a distinct species ; but it agrees in all essential
characters with A. scalni.

ENGLAND. — Cullercoats, Northumberland (Alder
Htntcock). [Falmouth, Cornwall (Cocks, 1849).]

132 BRITISH TUNICATA.

[Var. echinata rar. not'.'] (PL XV, figs. 5-7.)

Strongly echiiiated, mucli depressed, and adhering
for its whole length ; the sides of the test spreading in
a flat disc.

Lenr/th half an inch.

SCOTLAND. - - Lamlash Bay, Arran (Stevenson &
Carpenter).

[Var. laevis car. nov.~\

Orbicular, adhering largely by the side. Test
smooth or wrinkled, with the apertures very large and
stroii 2'ly echiiiated.

a «/

Length three quarters of an inch.
CHANNEL ISLANDS. — Guernsey (Al<:l'r).

24. Ascidia Normani Alder and Hancock.

(PL IV, figs. 3 and 4; PL XVIII, fig. 8; PL XIX,
fig. 11; PL XX, fig. 9.)

[Ascidia Normani ALDEE and HANCOCK in Ann. Nat. Hist.
(4) VI (1870), p. 361.]

Body elongated, pretty-regularly oval, white, deli-
cately tinged with rosy flesh-colour, attached by the
side of the base, transparent, strongly echiiiated, par-
ticularly towards the base and apertures, where the
spines are usually compound. Apertures of a rose-
colour, wide, produced, strongly ribbed and echiiiated
longitudinally; the branchial being terminal, the anal
about a third down the ventral margin ; ocelli small,
inconspicuous. Test thin, transparent, white, or only
slightly tinged with pale flesh-colour, covered with
simple and compound spines, strongest towards the
apertures and base. Ma it tie delicate, of a pale buff
flesh-colour, or almost colourless, the tubes well pro-
duced, and of a rosy colour. Tentacular filaments
rather long, white, wide at the base, distant, alternately
large and small, not very numerous. Branchial sac
minutely plicated ; stomata long ; thickened margin of

ASCIDIA XOEMANI. 133

tlie papillary membranes delicate, very slightly pro-
duced. Oral lamina' well developed, ribbed, margin
entire; the left oral appendages five or six, denticu-
lated, leaf -like, placed diagonally.

Length sometimes nearly three inches but usually
under two inches.

Hal. — Between tide-marks.

SCOTLAND. — Firth of Clyde
IRELAND. — Strangford Lough, Down (Norman). Bir-
terbuy Bay, Connemara, Galway, dredged (More].
First record.— Hancock, 1870; coll. Norman [I860].

This is a very beautiful species, the test (PI. IV,
fig. 3) being of a clear white, delicately tinged with
rosy flesh-colour, and when strongly echinated, as it
most frequently is, it has a fretted or frosted appear-
ance. It is usually attached to Fuel for a small space
by the side of the base. The external spines are to a
great extent compound.

The mantle (PL IV, fig. 4) is delicate and trans-
parent with a blush, of yellow flesh-colour, and the
muscular fibres are slender, and sparsely distributed ;
there is no opaque white on either side, except in the
region of the stomach which in some specimens is
covered with a minute freckling of white or yellow
matter. The tubes are wide, and of a rosy hue, par-
ticularly at the margin which is occasionally encircled
with rose-colour : the excurrent tube is quite one-
third down the side ; the branchial is terminal.

The branchial sac (PI. XVIII, fig. 8) has a few
scattered spots of opaque white which are mostly in
connection with the suspending vessels ; it is minutely
plicated ; the primary vessels are pretty-regularly
alternately large and small, but do not vary much in
size. The ciliated discs are large and oval ; they are
placed on the sides of the vessels and are in pairs
between the longitudinal bars ; the discs of each pair
are separated a little and diverge forward or towards
the oral lamina. The stomata are long, with the ex-

134 BRITISH TUNICATA.

tremities irregularly pointed or rounded. The longi-
tudinal bars are well elevated, rather delicate, but
rigid, with the suspended membrane wide ; the papil-
lary membranes are well developed, with the thickened
margin rather narrow and not projecting so as to form
a papillary point. The oral lamina (PL XIX, fig. 11)
is wide, strongly ribbed on the right side and with the
margin entire ; it tapers gradually as it approaches
the mouth, which is not quite at the bottom of the
branchial sac, and terminates in a fine point a little
below it. The left oral appendages are very character-
istic : they are from 6 to 9 in number and are in the

«/

form of pectinated, diagonal lamina? ; they vary some-
what in form, being either a little elongated and attenu-
ated at the ends, or short and more or less suddenly
produced ; and the number of the points varies from
one to four. The branchial tubercle (PI. XX, fig. 9)
is large and strongly involuted ; it is shield-shaped,
pointed below, wide and angulated at the sides above.
There are from 25 to 30 tentacular filaments ; they
are well developed, rather long and attenuated above,
with the base wide and blotched with opaque white,
and they are placed a little apart and are alternately
large and small.

The intestinal loop forms an irregular oval mass
placed near the posterior extremity of the body and
towards the dorsal margin ; it reaches about half way
up the mantle ; the rectum diverges slightly and
terminates at the atrium a little in advance of the
loop ; the anal margin is narrow, smooth, and reflected ;
the oesophagus rather long. The greater portion of
the alimentary tube is of a delicate buff colour, and
the right side of the stomach is usually covered with a
dense, minute freckling of opaque white or yellow
matter ; the coating of A'esicular matter is thin and
the vesicles are minute and inconspicuous.

The ovary is a tubular, branched organ confined to
the left side of the intestinal loop ; the extremities of
the branches, however, pass round the margins of the

ASCIDIA XORAHNI. 135

loop and are seen at the right side ; the ramifications
are disposed in an irregular radiating manner, and are
spread over the whole of the looped portion of the
intestine. The male ca3ca are small and appear at
both sides of the intestine, but are most conspicuously
displayed at the centre of the right side of the intes-
tinal loop.

The species is closely related to A. Miltm, but is
distinguished at first sight by its greater size, its
rougher and more spinous test, and by its peculiarly
delicate colouring ; the mode of attachment, too, is
different, and so are many of the minor points of
detail. But the best distinguishing feature is to be
found in the left oral appendages, which, in this
species, are large and denticulated, while in A. *<'<ilr«
they are simple and very narrow.

[Var. resplendens var. nou.~]

A brilliantly-coloured variety of this species occurs
at Polperro, Cornwall. This beautiful variety might
readily be mistaken for a distinct species did it not
agree in every essential character with the type form.
The mantle is of a clear yellowish colour, with the
centre portion of the left side irregularly blotched with
brilliant carmine. The blotches are usually more or
less blended and occasionally are entirely fused, so as
to produce a uniform patch of that colour. The tubes
are also streaked longitudinally with carmine, though
not always with much uniformity. The right side of
the mantle is paler in hue and is entirely devoid of
blotches or spots. The test is exceedingly rough
and spinous, and, though white, is sufficiently trans-
parent to exhibit the brilliant pallial colouring beneath.
Like the normal form it is attached to Fuel diagonally
by the side of the base, but sometimes rather exten-
sively.

We have much pleasure in dedicating this species to
our friend the Rev. A. M. Norman, to whom we are

136 BRITISH TUNICATA.

indebted for a great number of new forms of both the
simple and compound Tunicata.

25. Ascidia affinis Alder & Hancock.

(PI. XV, figs. 8 and 9 ; PL XVIII, fig. 9 ; PL XIX,
fig. 12 ; and fig. 3 in text.)

[Ascidia affinis ALDER & HANCOCK in Ann. Nat. Hist. (4),
VI (1870), p. 361.]

Sod]/ elongated, ovate, tapering upwards, semi-
transparent, dirty greenish white ; surface smooth or
only slightly wrinkled, echinated and somewhat rugose
towards the base and apertures. Ap<>riur<>* prominent,
large, tubular, longitudinally ridged, rugose or echi-
nated ; the branchial terminal, the anal a little way
down the ventral margin. Test semi-transparent,
thin, cartilaginous, of an obscure, pale, soiled greenish
white, smooth above and slightly roughened or echi-
nated towards the base and tubes. Mantle pale olive-
brown, almost colourless and transparent at the tubes,
which are well produced, wide, and strongly ribbed
longitudinally, both being directed upwards. Tfiitm-nlm-
Jiluiitfiifx numerous, moderately stout, alternately large
and small. Branchial *<><' minutely plicated, papillary
membrane with the free margin much thickened, but
very slightly produced. Orallamina wide, smooth, or
only slightly ribbed at the base, margin entire ; the
left oral appendages seven or eight, large, triangular,
denticulated, leaflets.

L(3ii<~/t]t upwards of two inches.

Halt. — Shallow water.

ENGLAND. — Roach river, Essex (Baird). Isle of
Wight, dredged in an oyster-bed (Jeffreys).

First record. — Hancock, 1870; coll. Baird [1805 or
earlier].

This species was obtained in great abundance by
Dr. Baird when examining the state of Roach River,
Essex, to report on its suitableness for the maintenance

ASCIDIA AFFINLS. Io7

of oyster fisheries. The specimens have usually a
soiled appearance, are much infested by parasitic
zoophytes, and are generally united at the base into
clusters, the base being considerably prolonged into
a sort of irregular, flat pedicle.

The test (PL XV, fig. 8) is rather thin and devoid
of the echinations common to the group to which the
species belongs, except towards the tubes which are
roughened and spinous.

The mantle is well supplied with interwoven
muscular fibres, the marginal and transverse ones
predominating, and is of a pale brownish colour when
preserved in spirit ; the tubes are wide, well produced,
and strongly folded longitudinally.

The branchial sac (PL XVII I, fig. 9) is minutely
plicated and considerably elongated, with the mouth
opening into it near to the bottom ; the primary vessels
are pretty -regularly disposed, and do not vary greatly
in size; and the ciliated discs which they bear are
large, ovate, and placed in pairs between the longi-
tudinal bars ; the latter are stout, not much elevated,
with the suspended membrane wide ; the papillary
membranes are moderately developed and have the
free margins much thickened and projecting very
slightly beyond the rods like short truncate papilla,
one at each primary vessel.

The oral lamina (PL XIX, fig. 12) is wide, and for
the greater part smooth, the ribs being confined to the
base, and it terminates rather abruptly at the right
side of the mouth ; the margin is entire. The left oral
appendages are 7 or 8 in number ; they are well-deve-
loped, pectinated, triangular leaflets placed diagonally
and each having from one to three points or teeth. The
branchial tubercle (PL XX, fig. 10) is large and trans-
versely oval ; it is much convoluted and has the inferior
margin indented. There are between 30 and -40 ten-
tacular filaments ; they are alternately large and small,
and are not cro \vded; their bases are a little widened
and marked with opaque white.

138 BRITISH 1TXICATA.

The alimentary tube is wide, and fills the lower two-
thirds of the pallial sac ; it is closely folded upon itself,
and the rectal portion rises up perpendicularly to the
atrium; the anal margin is smooth, narrow, and
reflected. The vesicular matter coating the tube is
inconspicuous, the nuclei, however, give to much of
the surface a minute freckling; the vesicles themselves
are quite small.

The ovary is composed of branched radiating tubes
spread over the right side of the upper portion of the
intestinal loop. A few of the extremities of the
branches pass round the margin of the loop and
appear at the left side. The male caeca are seen at
both sides of this portion of the digestive tube, but
are most conspicuous on the right side ; they are
small, clustered, and somewhat lobecl.

At first sight Axe! did offini* has considerable re-
semblance to A. xurdidii, and the mode of aggregation
into groups is very similar in both species; the colour,
however, is different, and the deficiency of branchial
papillae in the former shows that its alliance is with
A. scabra and its associates. And of these it seems
most nearly related to A. JYortnani ; it is distinguished,
however, from that species not only by its colour, and
comparative absence of echinations, which are almost
entirely confined to the tubes, but by numerous other
points of detail, amongst which may be mentioned the
form of the left oral appendages, and the great thick-
ness of the free margin of the papillary membranes.

26. Ascidia pustulosa Alder.
(PI. XVI, figs. 1-3 ; PI. XVIII, fig. 10.)

Ascidia pustulosa ALDER in Ann. Xat. Hist. (3) XI [1863],
p. 154.

Sod// ovate, rugose, horn-coloured, adhering towards
the base. Apertures sessile, strongly tuberculated or
echinated, reddish, the branchial terminal, the anal

ASC'IDIA PUSTULOSA. 139

nearly one-third down the side. Test rather thick,
semi-transparent, coriaceous, covered with irregular-
sized, warty, or pustulose tubercles, principally on the
upper or left side ; these generally bear lesser tubercles
or echinations on their surface ; the lower or recumbent
side is nearly smooth. Mantle yellowish, blotched with
red, especially towards the apertures, and sprinkled
with opaque white. Tentacular filament* few and
stout. Branchial sat' with rather small papillae. Oral
lamina wide, smooth, with the right side ribbed.

LctKjtii about three inches.

Hah. — Deep water?

ENGLAND. — Fowey Harbour, Cornwall, dredged
(Alder).

SCOTLAND. — Firth of Clyde [Lamlash Bay'r] (Ailnunt).
First ,-m»'d.— Alder, 18(33 [; coll. 1847].

This species is readily distinguished from J.. uin/fiila
by the pustulose tubercles of its test (PI. XVI, fig. 1)
as well as by its more ovate form ; in these respects it
approaches somewhat to A. amlrata, but it is of much
larger size, less echinated, and of a different colour.
It has only yet been found in the localities mentioned,
and appears to be rare.

The mantle (PI. XVI, fig. 2) is well supplied with
muscles which are not arranged with much regularity,
except at the margins from which they extend at right
angles in parallel order.

The branchial sac (PI. XVI, fig. 3, and PI. XVIII,
fig. 10) is minutely plicated, the plicae being deeper
than usual, and the meshes of the secondary vessels are
rather large. The primary vessels vary in size and
have a wide membrane along their sides, overlying
the undulations on the inner surface, so that a slight
longitudinal contraction of the respiratory web would
bring their margins together and prevent or regulate
the egress of the water contained in the branchial sac.
There are eleven or twelve well-developed tentacular
filaments, mostly with one or two smaller ones between

140 BRITISH TUXICATA.

them, and the branchial tubercle is large with the loop
placed transversely opening towards the ventral margin :
the extremities are turned forwards and backwards.
The oral lamina is wide, with distant ribs or pectina-
tions on the right side, the other side seems to be
smooth, though the pectinations shine through. The
longitudinal bars are rather delicate, and are much
elevated above the general surface ; the membrane
beneath is narrow, and there is one bar to each plication.
The papillary membrane is ample and has the free
margin much thickened and arched, and, projecting a
little in front of the bar, assumes the form of a short
obtuse papilla.

The ovary is a large dendritic organ spread over the
left side of the visceral mass, the branches being stout
and radiating : the testis is composed of a vast number
of minute casca which appear on both sides of the
alimentary tube.

27. Ascidia elliptica Alder & Hancock.
(PI. XVI, figs. 4-7; PI. XVIII, fig. 11.)

Asc'nlia i>rintnin [JAMESON in Mem. Wernerian Soc. I
(1811), p. 557: PENNANT Brit. Zool. IV (1812), p. 100;
STEWART El em. Nat. Hist. I (1817), p. 391; COLDSTREAM
in Edinb. new Philos. Jonrn. XIV (1830), p. -239: THOMP-
SON in Ann. Nat. Hist. (1) V (1840), p. 94;] FORBES and
HANLKY Brit. Moll. I [1848], p. 34; [NORMAN Zoologist,
£V (1857), p. 5708].

Pin- n « prunum FLEMING Brit. Aniin. [1828], p. 468.

i^Jqitlca ALDER and HANCOCK in Trans. Tyneside
N.F. Club, I [1848], p. 201; FORBES and HANLEY Brit.
Moll. II [1849], p. 374; [NOKMAX in Rep. Brit. Assoc.
1868 (1869), p. 302].

i prunum ''. THOMPSON Nat. Hist. Ireland, IV [1850],
p. 359.

[Noii A$ci<l/ri j >ni n inn MULLER Zool. Danica (1788).]

Body elliptical, a little convex on the upper side
and flat beneath, of a dull, sub-opaque brownish or
yellowish white in old specimens, more transparent

ASCIDIA ELLIPTICA. 141

when young, attached throughout its whole length.
Apertures, branchial terminal, papillose, very little
elevated, and divided into eight tubercular segments ;
anal situated a little below the branchial, rather promi-
nent, with six tubercles. Ocelli rather inconspicuous.
Tt'st tough, sub-opaque, transparent when young,
slightly tuberculated towards the apertures. Maiitlf
opaque, white or flesh-coloured, with a few red spots
between the apertures. Tentacular filaments rather
long. Branrliial sac with small primary, but no inter-
mediate papillae. Oral lamina strongly ribbed on the
right side.

Len</tli three quarters of an inch.

Hab. — On the under-side of stones at low water-
mark. Common on most parts of our coast (Furies).

ENGLAND. — [Bristol Channel (Forbes). ~\ Cullercoats,
Northumb. (All'i-). [Isle of Man (Furies).']

SCOTLAND. — [Bast and west coast (Forbes). Leith
shore, Firth of Forth (Jameson, 1811).] Firth of Clyde
(Norman). [Hebrides (Forbes, 1850). Allans, Cum-
brae (Norman, 1857).] Shetland (Forbes). [(Lerwick,
Shetland Isles, 1861 (Norman, 18(58).]

IRELAND. — [Strangford Lough, Down; and Belfast
Lough, Antrim, dredged (Thompson, 1840).]

First reconL — Alder and Hancock, 1848 [(Jameson,
1811, as Axt-'ul'ni prunum)~\.

The test (PI. XVI, fig. 4) appears to contain but
few blood-channels ; at least not many were observed.

The mantle (PI. XVI, fig. 5) is well supplied with
muscular fibres, which, in the centre, are loosely woven
in various directions ; but around the margin there is
a broad belt of parallel fibres which converge towards
the centre in pretty-regular order.

The branchial sac (PI. XVI, fig. 6 and 7 ; PL XVIII,
fig. 11) is rather delicate, and is minutely plicated as it
is in most species of the genus, only here the plicae are
wider than usual. The primary vessels are a little
variable in size, and the secondary rather long with

142 BRITISH TUX1CATA.

the stomata rather large. The longitudinal bars are
not very stout and are further apart than usual ; and
there is, pretty-regularly, one to every plait. The
papillary membrane is well-developed, and has the free
margin thickened and arched ; and, as the thickened
portion projects a little from the bar, the latter seems
to be provided with small, obtuse papillae at their
intersections with the primary vessels. This, however,
is only a modification or rudimentary condition of the
ordinary branchial papillae. The oral lamina has on
the right side strong distinct ribs ; and the branchial
tubercle (PI. XX, fig. 11), at its anterior extremity, is
small and loop-formed with the points placed upwards
and turned to each other. The tentacular filaments
are numerous, long, slender, and variable in length,
and are placed very near to the anterior margin of the
branchial sac.

The ovary is situated on the left side of the looped
portion of the intestine, and is composed of rather
delicate branches irregularly radiating from the centre;
occasionally a few ovarian branches appear at the
opposite side of the alimentary tube. The testicular
cceca are principally on the right side of the intestine.

Professor Forbes has referred this species to the A.
prunum of Miiller, but we think erroneously. The A.
prnmnti is described as lax, hyaline, and very pellucid,
free or only slightly attached, dwelling in mud. This
species has the test rather coriaceous, and is always
firmly attached to stones throughout its whole length.

28. Ascidia pellucida Alder & Hancock.
(PL XVI, figs. 8 and 9 ; PI. XVIII, fig. 12.)

A*<: it'll « jH-UiK-idu ALDER and HANCOCK in Trans. Tynesicle
N.F. Club, I [1848], p. 202; FORBES arid HANLEY Brit.
Moll. II [1849], p. 374.

Body irregularly ovate or subtriangular, hyaline,
very much depressed, and attached by a thin, broadly-

ASCIDIA PELLUC1DA. 143

extended disc. Bran-cliial tijx'rtnre terminal, wide and
tubular ; anal on a short tube a little way down the
side, curving upwards; ocelli conspicuous, red. 7Vx/
smooth, coriaceous, and perfectly transparent. M<tntl<j
small in proportion to the test, yellowish white, in-
clined to red on the lower parts.

LriKjth half an inch.

Hnl>. — Under stones within tide-marks.

ENGLAND. — Cullei^coats, Nor thumb., rare (Hancock).
[Falmouth, Cornwall (Codes, 1849).]
WALES. — Meiiai Straits (Alder).
IRELAND. — Killinny, Galway (Thompson).
l. — Alder and Hancock, 1848.

The vascular ramifications of the test (PL XVI, fig.
8) are not very conspicuous ; and the mantle is delicate
and only feebly supplied with muscular fibres.

The branchial sac (PL XVIII, fig. 12) is rather wide,
but does not reach to the lower border of the visceral
mass ; it is simple, not undulated or plicated ; the
primary vessels are pretty equal in size, and are placed
rather near to each other ; consequently the stomata
are shorter than usual, and have the extremities
rounded. The longitudinal bars do not bear papillae ;
but in their place, at the intersection, there is a stoutish
nodule or boss, which gives support to an almost
obsolete papillary membrane. The oral lamina, which
is not particularly wide, has the right side ribbed ; and
the branchial tubercle in front of it is a simple loop
open above. The tentacular filaments are numerous,
long, and slender, but vary in length ; they are placed
close together in a single line.

A. i>fll K ri<l ti is a very distinct species, and is readily
determined both by its external and internal characters.
The ovate or subtriangular form, the shortness of the
branchial sac, with the simple structure of the aerating
surface, and the deficiency of papillas on the longi-
tudinal bars, at once distinguish it.

144 BRITISH TUXICATA.

29. (?) Ascidia orbicularis Midler.

Ascidia orbicularis MULLER Zool. Danica, II [1788], p. 53,
pi. Ixxix, figs. I, '2; THOMSON in Ann. Nat. Hist. (1) V
[1840], p. 94; FORBES and HANLEY Brit. Moll. I [1848],
p. 34; THOMPSON Nat. Hist. Ireland, IV [1856], p. 360.

II oil i/ orbicular, depressed, whitish, adhering through-
out. Aperture* nearly terminal, approximated, sessile.
Text hyaline, transparent, spreading, having small,
unequal tubercles. Mantle opaque white or reddish
with yellow lines.

Diaritrfrr an inch.

Hal. — Shallow water, on sea-weeds.

IRELAND. -"—Strangf or d Lough, Down, on Zostem
mo riii a ( Tli o i i ipson) .

First record.- -Thompson [1840].

30. (?) Ascidia vitrea Van Beneden.

Ascidia i-itrca VAN BENEDEN Recli. Ascidies simples, in
Mem. Acad. Roy. Belg. XX [1847] , p. 61, pi. iv, figs. 1-5 ;
FORBES and HANLEY Brit. Moll. I [1848], p. 34; ALDER
and HANCOCK in Trans. Tyneside N. F. Club, I [1848], p.
200; [FORBES in Rep. Brit. Assoc. 1850 (1851), p. 242;
MERRIFIELD Nat. Hist, Brighton (1860), p. 81].

Body sub-globose or ovate, a little compressed.
Apertures terminal, placed a little apart, the branchial
largest and most produced, but both short ; ocelli red.
Test thin, transparent, membranous, and colourless.
Mantle white, with a yellow ring near the branchial
aperture.

Lentjth half an inch.

Hub. — Shallow water, on sea-weeds, &c.

ENGLAND. — Cullercoats, Northmnb., on small sea-
weeds (Aldi'-r). [Brighton, Sussex (Merrifield, 186')).
Falmouth, Cornwall (Cocks, 1849).]

IRELAND. — Killery Bay, Galway, on an Alcyonidium
(Ball, Thompson, and Forbes).

First record.— Forbes, 1848; coll. 1840.

ASCIDJA VITREA. 145

We have been unable satisfactorily to ascertain the
species which Professor Van Beneden describes under
the name of Ascidia vitrea, and therefore give it a
place here with diffidence. It is stated by Forbes in
' British Mollusca ' to have been met with in Killery
Bay, by Ball, Thompson, and himself, on Alcyonidium,
in 1840. Specimens of an Ascidian on Alcyonidium
gelatinosum in Mr. Thompson's collection are marked
with this locality and date ; but they appear to us to
be the young of A. sordida. The species met with at
Cullercoats and published under this name in Tyneside
Club Transactions requires ' also to be re-examined.
It is probably the young of Corella paraUelogramma.

EXCLUDED SPECIES,
mentioned in Introduction but not given in Synonymy.

•

Ascidia anceps TEMPLETON Mag. Nat. Hist, vii (1834), p.

131. IRELAND. — Carrickfergns, Belfast Lough, Antrim,

dredged, 1811 (Templeton,).
A. gemina TEMPLETON Mag. Nat. Hist, vii (1834), p. 129.

IRELAND. — Strangford Lough, Down (Thompson, 1840).
A. papilla DALYELL Edinb. new Philos. Journ. xxvi (1839),

p. 153. SCOTLAND (Dalyell).
A. rugosa COLDSTEEAM Edinb. New Pliilos. Journ. ix (1830),

p. 249. SCOTLAND. — East Lough, Tarbet, Argyllshire

(Cold stream).

(146)

INDEX

OF SPECIES, ETC., DESCRIBED IN VOL. I.
Synonyms in italics.

PAGE

Ascidia L. .64

aculeata Alder . .114

allida A. & H. . . 131

Alcleri Hanc. . 97

affinis A. & H. . 136

amcena sp. nov. . . 116

arachnoidea Forb. . 72

aspersa Miill. . 128

canina Jf«ZZ. . 122

communis Forb. . . 76

crassa Hcuic. . . 88

depressa A. & H. . .111

elliptica A. & H. . . 140

elongata.4. & H. . 112

inomata Hanc. . . 108

maraillata Cuv. . . 72

meiitula Miill. . 75

mollis A. & H. . 92

var. carnosa v. nov. . 94

monarchus Cuv. . . 76

Morei sp. nov. . . 126

Norniani A. & H.. . 132

var. resplendens v. nov. 135

obliqua Alder . 124

? orbicularis Midi. . 144

pellucida A. & H.. . 142

plana Hanc. . 94

plebeia Alder . 117

producta Hanc. . . 105

PAGE

Ascidia .prunu m (Miill.) Macg'. 119
prunum (Miill) Jameson,

&c. . 140

pustulosa Alder . . 138

robusta Hanc. . . 80

rubicunda Hanc. . . 83

rubrotincta Hanr. . 85

rudis Alder . 100

rustica (Miill.) Dalyl. . 119

scabra Miill . 128

var. albida A & H. . 131

var. ecliinata v. nov. . 132

i-ar. lajvis v. nov. . . 132

sordida A. & H. . . 119

veiiosa Mii.U. . 102

? vitrea Van B. . .144

Ascidiadse . . .64

Ascidium Bast. . . 64

ii/nitula (Miill.) Adams . 76

monarch us (Cuv.) Woodw . 76

Ph< ill it *i a Sav. . . 64

canina Sav. . 122

iitiitiitUata Sav. . 72

mentida (Miill.) Fleni. . 76

monarchus Sav . . . 76

Pirena Flem. . . 64

prunum (Miill.) Flem. . 140

Saccobraiicliiata . 63

Solitaria. 64

PRINTED BT ADLABD AND SON, LONDON AND DORKING.

EXPLANATIONS OF THE PLATES.

EXPLANATION OF THE LETTERING.

br. Branchial aperture.

l>r. s. Branchial sac.

b. t. Branchial tubercle.

en. Endostyle.

i. Intestine.

m. Mantle.

mo. Month.

n.g. Nerve-ganglion.

ce. (Esophagus.

od. Oviduct.

o. /. Oral lamina.

t. Test,

t. c. Tentacular collar.

tn. Tentacles.

ts. Testis.

•v. Ovarv.

«/

v. t. Blood-vessels leading to test.

Hate 1

PLATE I.
Ascidia mamillata Cuv. (p. 72)

Test : natural size.

>v

Plate 2

PLATE II.

Ascidia mentula Mull. (p. 75)

Mantle laid open (see p. 78) : about one and a half times
natural size.

Plate H .

b.t

-;-•'- , i . '..---^ til

'"•-» •

Plate 3

PLATE III.

Ascidia mentula Miill. (p. 75)

FIG.

1. Aperture of branchial sac.

2. Central portion of ventral blood-channel, continued at x

in fig. 3. a, vessel leading from mantle and appearing
to open into lateral vessel at b (repeated above and
below), and perhaps into net-work of vessels in space c.
d (repeated below), vessel leading from mantle to
branchial vessel e, and apparently opening into it.

4. Heart, with blood-channel s leading from it.

5. Endostyle ; anterior end.

All the figures magnified.

PI. ATtl I! I

6.t-

5

2

6

Plate 4

PLATE IV.

Fi«s.

1 and" 2. Ascidia rnl/u-inida Hanc. (p. 83) 1. — Test : three-
fifths natural size. 2. — Mantle : four-fifths natural
size. The projecting tubes on the left are blood-
channels communicating with the test. The nerve-
ganglion is seen about midway between the two
apertures, and on the opposite side is the endostyle.
In the centre are the ovary, oviduct, and intestine,
seen through the transparent mantle.

3 and 4. Ascidia Normani A. & H. (p. 132) 3. — Test: one
and a half times natural size. 4. — Mantle : natural
size.

PLATE IV.

'

I

Plate 5

PLATE V.

FIGS.
1-6. Aaddia iiwllis A. & H. (p. 92) 1-3.— Views of test :

natural size. 4. — Blood-vessels in test : magnified.

5 and 6. — Views of mantle : natural size. (2 and 5,

right side; 1 and 6, left side.)
7-11. A. mollis var. carnosa var. nov. (p. 94) 7 and 8.—

Views of test : natural size. 9. — Blood-vessels in

test: magnified. 10. and 11. — Views of mantle:

slightly enlarged. (8 and 10, right side; 7 and 11,

left side.)

PLATE V.

' 7

4

%>

^

0

Plate 6

PLATE ATI.

Ascidia plana Haiic. (p. 94)
Mantle, showing blood-channels, &c.
Three times natural size.

"

en—

'•

- 'V7^'

jr^rvH. ' ' v

T.t

-c" --^$^--x>^-r

• ff]$
'

Plate 71

•±->:-

Plate 7

PLATE VII.

FIGS.

1-4. Ascidia rudis Alder, (p. 100) 1. — Test: natural size.
2. — Mantle : natural size. 3. — Part of branchial sac :
magnified. 4. — Ocelli : highly magnified.
5. Ascidia venosa Mull. (p. 102) Test : natural size.

6-8. Ascidia depressa A. & H. (p. Ill) 6.— Test: natural
size. 7 and 8. — Views of mantle : natural size (7,
right side ; 8, left side) .

9-11. Ascidia aculeata Alder, (p. 114) 9. — Test: natural
size. 10. — Mantle : natural size. 11. — Part of bran-
chial sac : magnified.

PLATE VII

5

.

4

2

10

7

,.
k '

6

Plate 8

PLATE VIII.

Asc-idia venosa Miill. (p. 102)
Showing blood-channels in test.

Five times natural si/e.

Plate "Vffl.

V. - '>..-'•'".' ';

.

-" rv^ ? '• :':.

.. •.- ^ -

J -r.~-

: i j C

: i j C

W -X- . j

.- 1- ' . , - .

'-••.. .'. *j j
•/- _ • • -;-.j--

<';7 -w- I-V'- • ' ' \ . ' ' . :

m$ \ . , 9

Mm •-, .- • -v • :

• n

: •

Plate 9

PLATE IX.

Ascidia renosa Miill. (p. 102)

FIG.

1. The mantle.

2. Test and mantle laid open. The tentacles, tentacular

collar, endostyle (on right), branchial tubercle, oral
lamina with gland under nerve-ganglion (opposite
br.s.), and mouth, &c., are shown.

3. Test laid open, showing apertures of mantle, intestine,

blood vessels leading to test, &c.

4. Mantle with most of branchial sac laid open. ? , opening

of female duct. c?, opening of male duct. (The
pointer from r.t. is carried in error across the
vessel.)

About two and a half times natural size.

PLATE IX.

>

.n.c,

/

5

^Xil

Plate 10

PLATE X.

Ascidia venosa Mull, (p. 102)
Portions of branchial sac (see pp. 41-43 and 104) : much

enlarged.

These figures are two-fifths the size of Mr. Hancock's
drawings, being the greatest reduction made in any.

Plate :

j:@ '• '

•

• • ;

' • \j • • ~^
-58 •(-•••• rw. r^\

•j

| Jj e ^

4 c- 4

V , . S^^**

Q ;„_/ C^.

r

-

5

''"!'• •! 'V"»

•

|c

"U

m

. '• \

iT

i

\

•1

.,-

<v .

Plate 11

PLATE XI.

FIGS.

1 and 2. Ascidia « infi-na sp. nov. (p. 116) 1. — Test, with
branchial aperture directed upwards : one and a
half times natural size. 2. — Test of another indi-
vidual, with branchial aperture directed downwards:
natural size.

3-5. Ascidia plebria Alder, (p. 117) 3. — Test: natural
size. 4. — Part of branchial sac : magnified. 5.—
Ocelli : highly magnified.

6 and 7. Ascidia xardida A. & H. (p. 119) 6. — Tests of two
individuals: natural size. 7. — Mantle of another
individual : natural size.

8 and 9. Probably a variety of Corolla parallelogramma.
Views of test : one half natural size (8, right side ;
9, left side).
10. Afield ia ohliqna Alder, (p. 124) Test : natural size.

PLATE XI

Plate 12

PLATE XII.
Ascidia sordida A. & H. (p. 119)

FlGr.

1. Mantle. The male caeca, above blood-channel leading to

test, are well shown.

2. Mantle laid open, exposing branchial sac, month, and

oral lamina, &c.
o. Mantle and branchial sac laid open. The ovary is well

shown, with the oviduct lying close to the intestine.
4. Mantle and branchial sac laid open. The nearly circular

markings are the male caeca.

Twice natural size.

•.

PLATE XII

-,,-

2

4

I

Plate 13

PLATE XIII.

Ascidia sordida A. & H. (p. 119)
KEPRODUCTION.

FIGS.

1 . Test and mantle laid open, showing reproductive organs

— ovary in centre, male caeca on either side, and
oviduct full of eggs mostly passing out in single
series : about twice natural size.

2. Anal aperture, oviduct, and vas deferens : magnified.

Cf. Plate XII, figs. 3 and 4.

3. Aperture of oviduct (a) and of ras deferens (b} : more

highly magnified.
4-6. Clusters of eggs : highly magnified.

7. A single ovum, showing glassy layer (a) and yolk (b) :

highly magnified.

8. Male casca : magnified.

PLATE SDH.

S-

:

Tl

Plate 14

PLATE XIV.

Ascidia Morei sp. nov. (p. 126)

FIGS.

1. A group of individuals: two-thirds natural size.

2. A single individual : enlarged one-third.

3. Branchial tubercle ; two forms : highly magnified. (The

colouring is not accurate.)

4. Left hand side of mantle, showing blood-vessel leading to

test : three times natural size.

5. Right hand side of mantle, showing blood-vessel leading

to test : three times natural size.

6. Mantle laid open, showing branchial sac, branchial

tubercle, oral lamina, mouth, and endostyle : about
three and a half times natural size.

7. Branchial sac laid open, showing intestine, oesophagus,

ovary, oviduct, etc. : about three and a half times
natural size.

PLATE XIV.

\

7

>•<

Plate 15

PLATE XV.

Fios.
1 and 2. Ancidia xcabra Mull, (p. 128) 1. — Test: natural

size. 2. — Mantle : slightly enlarged.
3 and 4. A. *calra var. albida A. & H. (p. 131) 3.— Test :

natural size. 4. — Mantle : slightly enlarged.
5-7. A. scabra var. echinata (p. 132) 5. — Test: slightly

enlarged. 6 and 7. — Views of mantle of another

individual : slightly enlarged.
8 and 9. A. affinis A. & H. (p. 136) 8.— Test : natural size.

9.—?.

PLATE XV.

2.

7

8

4

Plate 16

PLATE XVI.

FIGS.

1-3. AscidiapimtulosaA.lA.eT. (p. 138) 1. — Test : natural
size. 2. — Mantle : two-thirds natural size. 3.—
Part of branchial sac : magnified.

4-7. .4. elliptica A. & H. (p. 140). 4.— Test : twice
natural size. 5. — Mantle : twice natural size. 6.—
Part of branchial sac : magnified. 7. — Part of the
same ; side view : magnified.

8 and 9. A. pellucida A. & H. (p. 142) 8.— Test : twice
natural size. 9. — Branchial aperture showing seven
ocelli in place of the usual eight : magnified six
diameters.

PLATE XVI

4

6

8

i..'

2

7

6

5

Plate 17

PLATE XVII.
THE BRANCHIAL SAC.

1. Ascidia mentula Miill. (p. 78)

2. A', rubicunda Hanc. (p. 84)

3. A. rubrotincta Hanc. (p. 86)

4. A. crassa Hanc. (p. 90)

5. A. mollis A. & H. (p. 93)

6. A. plana Hanc. (p. 96)

7. A. Alderi Hanc. (p. 99)

8. A. rudis Alder (p. 101)

9. A. producta Hanc. (p. 106)

10. A. inornata Hanc. (p. 109)

11. A. depressa A. & H. (p. 112)

12. A. elongata A. & H. (p. 113)

All the figures much enlarged, but reduced in various pro-
portions from Mr. Hancock's drawings.

Plate XVH.

< ""

4

K^< '.«!.

a

[I ;

V 'c~ — * S», f

NlPi

v: r3

ijf

" <• i 3!

,:

fflllliillllili

Wuf III : . ' J ^ ' , > |

n

Plate 18

PLATE XVIII.

THE BRANCHIAL SAC.

FIG.

1. At«:iili<i iK-itleata Alder, (p. 115)

2. A. amoena sp. nov. (p. 117)

3. A. plebeia Alder (p. 118)

4. A. sordida A. & H. (p. 121)

5. A. canina Miill. (p. 123)

6. A. obliqua Alder (p. 125)

7. A. seabra Miill. (p. 130)

8. A. Normani A. & H. (p. 133)

9. A. affinis A. & H. (p. 137)

10. A. pustulosa Alder (p. 139)

11. A. elliptica A. & H. (p. 141)

12. A. pellucida A. & H. (p. 143)

All the figures much enlarged, but reduced in various pro-
portions from Mr. Hancock's drawings.

pia.i .

'V-^

;'

5
Pi

> _- . '

us

; ' '-, , i . . k r**

Hi I

r-^r' q )

4

•Hi
-

^' \ ~- '

•

•

1

. -* 1

ff

-

If

•

10

1

11

-I

i ?fe ==

"G

I

IF '

'
•

ftjyiw

ij

I

12

Plate 19

PLATE XIX.

THE MOUTH AND ORAL LAMINA.

FIG.

1. Ascidia rubicunda Hanc. (p. 84)

2. A. rubrotincta Hanc. (p. 87)

3. A. crassa Hanc. (p. 90)

4. A. mollis A. & H. (p. 93)

5. A. plana Hanc. (p. 96)

6. A. Alderi Hanc. (p. 99)

7. A. producta Hanc. (p. 106)

8. A. depressa A. & H. (p. 112)

9. A. aculeata Alder (p. 115)

10. A . scabra Mull. (p. 130)

11. A. Normani A. & H. (p. 134)

12. A. affinis A. & H. (p. 137)

All the figures much enlarged, but considerably reduced
from Mr. Hancock's drawings.

Piaxe ] K

1

6

.

'

12

Plate 20

PLATE XX.
THE BRANCHIAL TUBERCLE.

FIG.

1. Ascidia mentula Mull (p. 78)

2. A. robusta Hanc. (p. 82)

3. „ ,, another form.

4. A. rubicunda Hanc. (p. 84)

5. A. crassa Hanc. (p. 91)

6. A. plana Hanc. (p. 96)

7. A. sordida A. & H. (p. 121)

8. A. canina Mull. (p. 124)

9. A. Normani A. & H. (p. 134)

10. A. affinis A. & H. (p. 137)

11. A. elliptica A & H. (p. 142)

All the figures much enlarged, but considerably reduced
from Mr. Hancock's drawings.

Plate XX.

/

^

10

8

KAY SOCIETY

INSTITUTED 1844

FOR THE PUBLICATION OF WORKS ON
NATURAL HISTORY.

ANNUAL SUBSCRIPTION ONE GUINEA.

SUPPLEMENTARY
LIST OF THE SOCIETY

FOR THE YEAR 1904.

ADDITIONS FROM JUNE TO DECEMBER, 1904.

OFFICERS AND COUNCIL.

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FOR.SEC.R.A., F.R.S., F.L.S., ETC.

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F.R.S.E., Pres.L.S.
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being Additions to the List of June, 1904.

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/I