Ascidia. MOLLUSCA. Boteyllid^. 383 
is extremely accurate. On the coasts of the Mediter- 
ranean and in China (where species of Ascidite occur), 
several of them are esteemed as articles of food. Van 
Beneden informs us that at Cette Ascidise are taken 
regularly to market, and that a particular species 
{Cynthia microcosmus), “ although so repulsive exter- 
nally, furnishes a very delicate morsel, much sought 
after hy some.” 
Genus Ascidia or Sea Squirt. — This genus is 
known hy its sessile body beingcovered with a coriaceous 
or gelatinous tunic; the branchial- orifice being eight- 
lobed, and furnished inside with a circle of simple ten- 
tacular filaments ; the anal orifice is six-lobed, and the 
branchial sac is not plaited. The species vary in 
length from one to five or six inches, and range from 
low water to twenty fatlioms. In some of the Ascidice 
the external tunic is pale and semitransparent, and the 
inner coat is orange or crimson, or sometimes marbled 
with orange and white. Most of them, however, as 
Sir John Dalyell says, “ are coarse, unsightly, deformed- 
looking animals, utterly void of that external symmetry 
and beauty rendering many of the tenants of the waters 
so interesting. Nor is it in this only that they should 
fail to attract the spectator’s notice. They testify 
neither instinct, action, nor motion, nor even the symp- 
toms of life, farther than slight enlargement and reduc- 
tion of size, together with contraction and expansion 
of the two tubular orifices of the body. No sensible 
attraction follows abstinence or repletion ; the external 
form undergoes scarcely any modification from health 
or disease ; even the lapse of time, that universal con- 
sumer, seems hardly to make any impression on the 
shapeless mass, which is rooted immovably from the 
first moment on the same spot to vegetate, live, or 
die.” 
Genus Cynthia. — This genus is sessile as well as 
Ascidia, and its test or tunic is coriaceous ; both bran- 
chial and anal orifices are four-lobed, and the branchial 
sac is plaited longitudinally ai.d surmounted by a circle 
of tentacular filaments. About fourteen species are 
described as inhabiting the coasts of Great Britain, and 
theyare found ranging from lowwater to thirty fathoms. 
Individuals are often seen unattached as well as fixed, 
though, as Mr. Rupert Jones observes, these animals 
“ cannot be said to have an entirely free existence, their 
tests being usually more or less imbedded in sand or 
mud, and frequently held to their anchorage by the 
agglutination of the surrounding sand-grains to their 
outer surface. But from such a position they are easily 
disturbed.” The species of Cynthia are also frequently 
found associated in groups of numerous individuals, 
forming large bunches in consequence of the interlacing 
of their root-fibres. The genus is represented by two 
species, C. momus and G. Canopus (Plate 9, figs. 
7 and 9). 
Genus Boltenia. — This genus instead of being ses- 
sile, as in the two preceding genera, has its coriaceous 
body fixed by a peduncle to stones, often in deep water. 
Sometimes young Bolteniae fix themselves on to the 
stem of their jiarent. In this genus the orifices are 
lateral, and both of them are cleft into four lobes or 
rays; the branchial sac is longitudinally plaited and 
surmounted by a circle of compound tentacles. 
Two other genera belong to this family, Molgula. 
and Chelysoma — the one (Molgula) having a mem- 
braneous tunic or test, but usually invested with sand 
or other extraneous matters; the other having its 
coriaceous test resembling the carapace of a tortoise. 
Family II. — CLAVELLINIDiE {Social Ascidians). 
The “ Social Ascidians” are very small animals found 
on stones, shells, and sea-weed, adhering by numerous 
root-like projections of their outer tunic. As their 
name indicates, these animals occur in groups of several 
individuals, each having its own heart, respiration, and 
system of nutrition, but fixed on peduncles or stalks 
that branch from a common stem, through which the 
blood circulates in opposite directions. They are such 
transparent and colourless animals, that their internal 
structure can be seen without dissecting them. Repro- 
duction takes place in these Social Ascidians by gem- 
mation or by the process of budding, as well as by 
eggs. The new individuals so formed may contitiue 
united to the parent, or may become completely free 
by the rupture of the connecting tube. 
Genus Clavellina. — In this genus the individuals 
composing the compound body are connected by creep- 
ing tubular prolongations of their common tunic. They 
are elongate, erect, more or less pedunculated; the 
outer tunic is smooth and Ransparent, and the thoracic 
portion of the body is usually marked with coloured 
lines. The branchial and anal orifices are both simple, 
without lobes or rays. The species which have been 
observed are found in the northern seas and in the- 
Mediterranean. This genus is represented by C. borealis 
in Plate 9, figs. 5 and 6. 
Genus Perophora. — This genus differs from the 
preceding in the individuals being suborbicular and 
compressed, and the thoracic portion of the body being- 
destitute of coloured lines. There is only one species 
known. It is beautifully transparent, according to 
Professor Forbes, who has dredged it adhering to sea- 
weed on the coast of Anglesea, and appears like little 
specks of jelly dotted with orange and brown. When 
dried, these bodies appear like the minute ova of some 
mollusk. 
Family III. — BOTRYLLIDiE {Compound 
Ascidians). 
The Botryllidcp- are compound animals, and fixed. 
The animals are associated with each other, their tests 
being fused together so as to form a common mass in 
which they are imbedded in one or more groups. Each 
individual, however, has a distinct branchial and anal 
orifice, and they are not connected with one another by 
any internal union, “If, when walking on the sea- 
shore about low water mark, we turn over large stones, 
or look under projecting eaves of rock, we are almost 
sure to see translucent jelly-like masses of various hues 
of orange, purple, yellow, blue, grey, and green, some- 
times nearly uniform in tint, sometimes beautifully 
variegated, and very frequently pencilled as if with 
stars of gorgeous device ; now encrusting the surface 
of the rock, now depending from it in icicle-like pro- 
