Edward Forbes.

A history of British star-fishes, and other animals of the class Echinodermata online

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composed of twenty white chalky triangular pieces ar-
ranged in pairs. The retractile muscles of this apparatus
are short, ovate, and attached posteriorly a little behind
the mouth. The canal surrounding the attachment of
the oesophagus bulges out between each of the ten plates.
To this circle or canal there is attached a sac of a cylin-



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226 PENTACTiB.

drical shape, slightly bulging at the extremity. The in-
testinal canal is of moderate length, and its coats are very
tender. The branchial tree is not very complex, and has
no sacs attached to its trunk. The generative tubes are
comparatively few, not exceeding fifty, and are short and
white. The skin is coriaceous, and the muscular tunic
thin.

When dredging on the west coa^ of Ireland with Mr.
W. Thompson, Mr. Ball, and Mr. Hyndman, in the sum-
mer of 1840, we took a great number of this handsome
species, many as large as four inches, and all presenting the
external characters described above. It appears to be
rather an apathetic species, and to have scarcely any power
of retracting its suckers ; but this may have been owing to
a circumstance which is of no small interest to both zoolo-
gist and geologist. The Lough of Killery, in which we
found it, is a narrow and long inlet of the sea. To-
wards the upper part of it, whilst the under-water is salt
and ftdl of truly marine animals, the surface-water is so
fresh that our boatmen were used to drink it. The con-
sequence was that in drawing the dredge through the layer
of fresh water the contained animals were paralysed, and
many observations which we had planned to make upon
them were thus unexpectedly defeated.



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TANGLE SEA-CUCUMBER. 22?

HOLOTHURIADM, PENTACTM.



TANGLE SEA-OUCUMBER.

Cucumaria fucicola. Forbes and Goodsir.

Spedjie Cfharacter, — ^Body ovate, rounded, purple, smooth; tentacula deep
brown, ovate, pinnate, shortly pedunculate ; suckers numerous in each avenue,
alternate.

Holoihuria/ticicola, Forbes and Goodsir, Athenaeum, No. 618.

This species is not uncommon in Bressay Somid, Shet-
land, where it is found in seven fathoms water, adhering
to the stems of Laminarise. It is about three inches in
length when ftdl grown, and is very smooth. When at
rest with its tentacula, which are short, and somewhat
clavate or sub-globose in form, exserted, it generally as-
sumes an ovate form. It is a sluggish species, and adheres
strongly by means of its suckers, which are closely ar-
ranged in five equidistant rows. Its internal structure
presents no peculiarities. There is but one oesophageal
sac ; the respiratory trees are moderately developed, and
the generative tubes rather numerous. The teeth are
somewhat triangular at their apices.

ci2



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228 PENTACTiB.

To this genus also belongs the following species of Dr.
Fleming (if, indeed, it be more than a variety oi Cucvmaria
pmtdctes).

" H. dissimilis. (Fleming, Brit. An. p. 483.)

"Body pentangular, tapering to both extremities;
suckers hard, conical ; tentacula of two kinds ; those which
are plumose are shorter than the five simple ones which
are opposed to them.

" A single specimen of this probably new species, about
two inches in length, was found by Dr. Coldstream on
Leith shore.'^

In the same valuable work is the following notice of a
species which seems to be distinct, but is very ambiguously
characterised.

" H. NeUlii. Tentacula ten, with ten subsidiary ones
surrounding the margin of the mouth. — Frith of Forth,
Mr. (now Dr.) NeiU.

" This species, in form and colouring, bears a near
resemblance to the preceding (Holo. Montagui), but it
differs in the exterior tentacula being more subdivided,
and in the number of the anterior ones. These last are
similar in form to the outer ones, though only one-fourth
of their size. This species was brought to Mr. Neill by a
Newhaven fisherman, 3d September 1818. Being in com-
pany with this intelligent observer of natiu*e at the time,
he kindly presentee^ it to me, and remarked that it was
different from the two species which Professor Jameson,
on his authority, had recorded (Wem. Mem. I. p. 658)
as natives of the Frith of Forth, circumstances which in-
dicated the propriety of its specific appellation. I have
since received a specimen from Cape Wrath through the
kindness of my friend Dr. Coldstream.**'



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BROWN SBA-OIRKIN. 229

HOLOTHURIADJE, PENTACTM,




Genus Ocnm. Forbes and Goodsir.

Qmuric Character, — Body regular, cylindrical, pentagonal, with five rows of
distant suckers on the angles; tentacula ten; dental apparatus very short (a
gizzard).

BROWN SEA-GIRKIN.

Ocnm hrunmm, Forbes.

I^pedfic Character. — Colour brown ; tentacula long, pedided, pinnate,

Hi]l(Ahuria hnmneay Forbbs, MS. Thompson, Annab of Natural History,
No. 29. April 1840. 5

The animals to which we have appUed the name of
Sea-Girkins, differ from the CucwmaruB^ externally, in the
very few suckers which crown their angles, and, internally,
in having a strong muscular gizzard. In their motions
they differ also very considerably, not constricting them-
selves, and blowing themselves up as the Sea-Cucumbers
do, but elongating themselves like worms, to which ani-
mals they approximate in their movements. Their suckers
are exceedingly strong, and always exserted, few in num-
ber, and appearing as if ranged in a single line. Two
species, both of which seem to have escaped the observ-
ations of British naturalists till lately, are found in our



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230 PENTACT^.

seas. The first, that before us, appears to be among the
most abmidant and extensively distributed of all the
British HoloihuriadtR. The Ocni are sluggish creatures.

The Brown Sea-Girkin is about three-fourths of an inch
in length, and sometimes longer. It is regularly pen-
tangular, obtuse posteriorly, and truncate anteriorly.
There are about nine large suckers on each of the angles.
The tentacula are very long, and digitate or simply pin-
nate towards their extremities. They are white, as also
the suckers ; but the body is pinkish-brown, with darker
specks, and quite smooth. It lives on shell-banks at
various depths, both on the east and west coasts. At the
mouth of the Frith it frequently comes up on the haddock-
fishers^ lines. In the Frith of Clyde it is commoii. It
also occurs on the shores of the Isle of Man. Mr. W.
Thompson states that it is the most common species taken
by dredging in the loughs of Strangford and Belfast.

The vignette represents a Bunic or Buddhist cross near
Ramsey Bay, Isle of Man.



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MILK-WHITE SEA-GIRKIN. 231

HOLOTHURIADM. PENT ACT M,




MILK-WHITE SEA-GIRKIN.

Ocnui lactem. Forbes and Goodsir.

SpedJUi C%arocfer.— Colour milk-white j tentacula short, triangular, pinnate.
Holothuria laetea, Forbes and Goodsir, Athenaeum, No. 618.

A SECOND species of Sea-Girkin was found by Mr.
Goodsir and myself in the Sound of Bressay, Shetland,
at the same time with the various Sea-Cucumbers which
we hare described from that quarter. The one before us
is a very pretty species. It is small, the largest examples
being not more than three-fourths of an inch in length.
The body is of nearly the same thickness throughout,
cylindrical, and five-angled. On each angle there is a row
of prominent non-retractile suckers. The rows appear
single in consequence of the distances between the alter-
nating suckers, which are from seven to nine in each.
The posterior and anterior extremities seem as if trun-
cated ; the latter bears the tentacula, ten in number, short,
pyramidal, and pinnate. The entire animal is of a white
colour.

Mr. Goodsir and I opened all our specimens of this
animal, save two, without finding any traces of respiratory
organs, and but few of genital. In two specimens, how-



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232 PENTACT-fi.

ever, the former were seen in the usual position and of the
usual form, but not so much branched as the respiratory
trees in other Sea-Cucumbers. There was but one sac
attached to the oesophagus. The teeth or dental plates
were short, and formed as in the last described. The in-
testine enlarged into a gizzard-like globose stomach just
below the mouth, and was not so complicated in its
roUed-up length and numerous twists, as in the Cucumaria,
The interior of the muscular coat was much smoother, and
the muscles apparently weaker.

The specimens alluded to above were dredged adhering
to muscles. Mr. Goodsir has since found many of them,
brought up on fishermen'*s lines off the Fife coast and in
the German Ocean. It has been added to the Fauna of
Ireland, by my friend Mr. W. Thompson of Belfast, who
obtained it on the north-east coast.

Sir John G. Dalyell, who has also found this species,
observes regarding it and other Holothuriadse that when
in confinement the tentacula are usually expanded towards
night. " When evening comes,'' he says, " a tuft pro-
truding from the larger extremity unfolds into a capacious
frmnel, composed of eight, or ten, or twenty beautiftJ
branches implanted on a shelly cylinder, in the centre of
which is the mouth. Each branch now begins to sweep
the water in succession, and descends almost to the root
within the mouth in a contracted state, whence it arises to
enlarge anew. These evolutions are protracted until the
latest hour ; but as morning dawns the whole apparatus is
withdrawn, the skin becomes close and compact as before,
and a fountain begins to play from the opposite extremity."
(See Athenaeum, No. 675.)



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COMMON THYONK. 233

HOLOTHURIADM, THYONES.



Genus Thyone. Oken.

Generic Character, — Body nearly regular, covered with scattered papillote
tuckers ; tentacula ten ; teeth of the dental apparatus long and filiform.



COMMON THYONE,
Thyme papillosa, Muller.

Specijie Character, — Body elongate-ovate, brownish white ; tentacula much
pinnate.

Holoihuria papulosa, Mullbr, Zool Dan. tab. cviii. fig. 3. Jaeoer, de Holuth.

Encyc. M^th. pL Izxxvi figs. 5, 6. Blainvillb, Man,

d*Actin. p. 193, pi. ziii. fig. 2.
MitUeria papulosa, Johnston, Mag. Nat Hist vol. VII. p. 684, fig. 66,
Thi/one papillosa, Oken. Aoassiz, Prod.

The genus Thyme was constituted by the distinguished
G^nnan naturalist and philosopher, Oken, for the reception
of such HolothuruE as have the suckers dispersed over the
whole surface of the body, as in the species before us.
But though the suckers are so scattered, the pentagonal
form and radiated appearance of the animal is not so much
lost as in Psolus ; indeed, in many specimens certain of



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234 THTONBS.

the suckers may be seen arranged regularly as in Cucrnnr
aria^ while m the latter genus we occasionally find ex-
amples of a similar yariation in the way of suckers, scat^
tered here and there between the avenues, thus indicating
an approach to Thyone. Some time after Oken had so
named these animals. Dr. Fleming, unaware of the cir-
cumstance, and equally perceiving the necessity of their
generic separation (which was indeed suggested by Ouvier),
constituted the genus under the name of Mulleria, which
name has been since applied by Jaeger to another section
of the tribe.

The species before us was first observed by Muller, who
obtained it from the Faroe Islands. As a native of Bri-
tain it was first noted by Dr. Johnston, who published an
excellent description and figure of this species in the
seventh volume of the Magazine of Natural History. He
found it in Berwick Bay ; it is, however, by no means an
uncommon species on our shores. A few winters past
great numbers were thrown ashore after a violent storm at
Anstruther in Fifeshire, where they were observed by my
friend Mr. Goodsir. I dredged up a small one on the
Scallop-banks off the Isle of Man in 1838; and it has
been taken on the Irish coast by Mr. W. Thompson, in
Belfast Bay and Strangford Loch. In Ireland it also
occurs on the west coast in Killery, and Mr. W. M'Oalla
pointed it out at Roundstone, Cunnemara, living in great
numbers buried in gravelly sand at low water, which cir-
cumstance accounts for the quantity of gravel usually
adhering to it.

The Common Thyone measures from one to nearly three
inches, and is of a brownish-white colour, more or less
dusky, and of an ovate or pear-shape when at rest, though
it can lengthen itself considerably. When the tentacula



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COMMON THYONE. 235

are withdrawn it usually appears more bulging on one
side than on the other. The skin is rather tough, and
covered all over with non-retractile suckers, which give it
a papillose appearance. The tentacula are ten in number,
large, and not always equal ; sometimes two of them are
much smaller than the rest, and when such is the case it
is in the habit of moving these two alternately towards
the mouth, while the others are at rest* Many Holothvr
riada exhibit this custom. The tentacula are large,
generally whitish, and broadly pinnate. In Dr. John-
ston'*s specimens they were brown, with darker dots. The
hinder part of the body tapers, and the vent is stellate.

On opening a number of specimens,
many of them were empty, the animal
having ejected its intestines. A perfect
one presented a well-developed intestine,
moderately branched respiratory trees, one
(esophageal sac, and numerous generative
tubes ftdl of eggs, being then yellow and
much dilated, the eggs of a yellow colour, and not
arranged in any peculiar manner. This specimen was
taken in January ; but as several others taken at the same
time presented no appearance of eggs, no inference can be
drawn as to the animal^s breeding season. The teeth were
singular and very peculiar, being much elongated and
filiform, and separated from each other by rows of pen-
tagonal plates. There was but one oesophageal sac. Dr.
Johnston'^s had five. One specimen dissected had ejected
all its internal organs, saving the generative tubes ; and in
another there were no traces even of them.

Dr. Johnston gives the following interesting account of
its habits in confinement in the paper alluded to : — " The
surfaces of the body," he says, "were at first partially



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236



THYONES.



covered with fragments of shells and corallines,. which were
evidently retained by the suctorial property of the papillae,
and the animal, on being kept a day in sea-water, threw
them off. It had a slow progressive motion ; slower than the
shadow of the dial, which was effected by elongating the
papillse of one part, fixing them to the plate, and then
drawing itself forward by again contracting those elongated
parts ; but the papillae were oftener used for the purpose
of anchors than of feet, the creature being of an indolent
and immoveable character. When stationary, it was ever
slowly changing its outward form ; it was now shortened
and swollen in the centre ; then it would relax itself and be-
come cylindrical ; again one part would be blown out, and
another drawn in with a deep stricture, as if a thread had
been tied round; or again the contraction would begin
near the head, which is then made very narrow, and would
spread backward, the anterior portion recovering its ori-
ginal diameter as the wave of constriction passed away ;
and sometimes the constriction will spread in the opposite
direction. It often raised the posterior extremity a little
from the sur£Etce of the plate, and to one side ; but I never
saw any current flow from the aperture. To effect these
varied motions, we must suppose the existence of niuscular
bands or fibres on the coriaceous skin, both in a longi-
tudinal and circular direction ; and on opening the body
we find such to be the case : five strong, white, raised
bands run from one end to the other, radiating from the
circular apertures, and numerous fibres pass between them
transversely, among which minute pores open everywhere,
which are the inner orifices of the cuticular papillae.'*^ Dr.
Johnston adds the following account of the voluntary
ejection of its viscera : — " The worm having been kept in
sea- water, unchanged for two or three days, sickened, and.



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COMMON THYONE.



237



by the more frequent involutions and evolutions of its oral
end, evinced its uneasiness. Being left unobserved in this
state for an hour or so, I found on my return that it had
vomited up its tentacula, its oral apparatus, its intestinal
tube entire, and a large cluster of ovaries which lay about
the plate. The muscular convulsion must have been very
great that thus so completely embowelled the creature;
and yet life was not extinct, for the tentacula contracted
themselves on being touched, and the empty skin appeared
by its motions to have lost little of its irritability.'*''

Dr. Johnston conjectures the water is conducted into
the body through the tubes, and then floating round the
respiratory filaments is ultimately forced through the canal
that leads to the anus. In all of the species I have
examined, I do not think this possible, the feet resembling
in their structure internally and externally those of the
Starfish and Sea-Urchin. In some works it is stated that
the Echinodermata fill their bodies with water by swallow-
ing it, but the statement is based on no foundation. On
cutting open a distended Gucumaria frondosa, Mr. Goodsir
and I found the water entirely lodged between the sides
and the external coats of the intestinal canal. How it
enters is a problem yet to be solved.



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238 THYONES.

HOLOTHURIADJE, THYONES,



PORTLOCK^S THYONE.

Thyofm Partlockii. Forbes.

Specific Character, — Body cylindrical, corrugated, white ; suckers numerous,
large ; tentacula frondose, purple.

The Thyone Partlockii is a large species, measuring five
inches in length, and connects by its form and general
aspect the genus Thyone with Cucwmaria. The body is
white, and is covered with a strong smooth coriaceous in-
tegument, over which the strong white suckers are some*
what irregularly scattered. On the five angles they are
most numerous and rudely arranged in rows. The ten-
tacula are ten in number, large, frondose, and purple. The
internal structure of the animal presents a large and strong
dental apparatus, numerous genital and respiratory tubes,
and one pyriform sac. This handsome species was kindly
communicated to me by Captain Portlock, to whom I have
dedicated it, and by whom it was discovered in Belfast
Bay, in the course of the Ordnance investigations in the
North of Ireland.



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montagu'^s chibodota. 239

HOLOTHURIADjE. synaptje.




Crenus CUrodota. Eschscholtz.

Generic Character, — Body cylindric, Termiform, without suckers; tentacula
elongate, digitate at their extremities.

MONTAGU'S OHIRODOTA.

Chirodota digitata, Montagu.

Specific Character, — Body vermiform, white, with orange spots; tentacula
long, peduncled, digitate.

HcloOmria digitata^ Montagu, Lin. Tr. vol. xi. p. 22, t iv. fig. 6. Blainville,

Alan. d^Actin. p. 194.
Fistularia digitata, Lamarck, 1 Edit III. p. 76 ; 2 Edit III. p. 448.
MuUeria digitata, Flem. Brit Anim. p. 484.

This remarkable animal was discovered by Montagu
on the southern shores of Devonshire. Its discoverer



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240 STNAPTiE.

refers it to the ffolothuria inharens of Muller, with a
query ; but it is assuredly distinct from that animal, which
is a Cucwmaria^ nearly allied to our Cucumaria fmif<yirmis.
As I have never seen living examples of the Chirodota digir
tata^ I think it best to quote in frdl the description of it
given by the eminent and accurate observer who first
found it.

" Body long, cylindric, covered with minute papillae of
a yellowish white colour, marked with small spots of red
orange, closely disposed, and in many parts confluent ;
posterior end tinged with green ; tentacula twelve, short,
dividing at their tips into four obtuse branches of a pale
colour; length, when extended, between three and four
inches.

'^ This rare species is capable of great contraction, and
probably multiplies by natural division, as it separates
without violence into an indefinite number of pieces : this
is effected by muscular stricture, which forms ligatures
and separates portions into globular pieces; sometimes
two or three of these ligatures are formed together, and
as many separations ensue, provided the exterior one
first falls off; otherwise the part separated appears
to continue in that moniliform state. This, however,
may be a forced action from confinement in a glass of
sea-water, and one division at the extremity is the
order Nature most likely pursues. It must, however,
be admitted that our knowledge with respect to these
inhabitants of the deep is extremely limited, since they
can only be examined when taken from their natural
abode ; the form of these creatures is nearly all we may
expect to become acquainted with, for their oeconomy is
concealed from us by that insurmountable barrier which no
philosopher can pass.



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MONTAGUvft C5HIR0D0TA.



241



" The faculty which this animal possesses of separating
into so many parts renders it almost impossible to preserve
a perfect specimen entire.'^

It is evident from the above description that this animal
cannot be associated generically with any of the other
British Holothuriadse ; it may be questioned whether it is
not a member of the next order of Echinodermata, where
indeed all the Synaptse might be placed. So accurate an
observer as Montagu would scarcely have passed over the
suckers without mention had they been present. Its cha*
racters, as at present known, associate best with the genus
Ohirodota ; and until more specimens be procured, and an
anatomical examination instituted, it must be placed in
that genus, seeing that as yet there are not grounds enough
known for adopting it as a type of a separate genus.

Doubtless there yet remain many undiscovered species
of Holothuriadse in the British seas. Of Starfishes we
must not expect to find many more kinds, though Goni-
aster miliaris, and some few others which have been seen
on the Norwegian shores, may be looked for. Of Sea-
Urchins there are probably still fewer unnoticed ; but of
the Sea-Cucumbers many. Their comparatively unat-
tractive aspect, the difficulty of preserving them (they
must always be kept in spirits), their habitat in the sea,
and the little attention that has hitherto been paid to
them by native zoologists, all lead me to believe that
many species have been passed over. We have as yet no
representative of the typical Holothurise which have twenty
tentacula in the British Fauna. Several of these, such as
the Holothuria elegans, and Holothuria mollis, inhabitants
of the Scandinavian shores, will probably ere long prove
to be natives of our own.

Much yet remains to be done towards a full investiga-



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242 SYNAPT^.

tion of the anatomy of the Sea-Cucumbers, more especially
with a view to a comparison of the structure of the Mol-
luscan with the Annelidous forms of Holothuriadae. The
elaborate dissections of Chiagi require to be repeated
before we can put implicit confidence in their accuracy.

There is a point in the economy of these animals, and
also of the Sea-Urchins, to which I would direct attention.
In some specimens, not in all, nor in all the examples
of any one species, we find red globules, variable a« to
number and large as to size, floating in the fluid of the
aquiferous system.

The vignette is a view of St. Andrew'^s Castle and Bay,
a rich gleaning ground to the naturalist.



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243



SIPUNCULIDiE,

OB VERMIGRADE ECHINODERMATA.

In the animals of which we have now to treat, Radi-
isM sets and Annulism appears. In their external ap-
pearance they are worms, for the likeness they bear to
the Holothuriae depends on a correspondence with the ver-
miform, and not the radiated characters of those animals ;
but internally they afford evidence of belonging to the
same great class. They are, in fact, Annelidous Radiata,
the transition between the Radiated and Symmetrical
types of form. They have no rows of suckers ; their bodies
are not divided into a quinary arrangement of lobes or seg-
ments ; their mouths are either not surrounded by ten-
tacula, or their tentacula are no longer regulated by a
definite number. Their motions and habits are those of
worms. Instead of having their skins strengthened by
calcareous spines, such as have prickly appendages have


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Online LibraryEdward ForbesA history of British star-fishes, and other animals of the class Echinodermata → online text (page 15 of 17)