VAN NAME: COMPOUND ASCIDIANS. 
367 
of the test might be taken to indicate that each zooid is independent. 
Many vascular processes from the zooids extend down into the pe- 
duncle of the colony. In the alcoholic specimens the test is whitish 
and suflficiently transparent in the heads to allow the zooids to be 
plainly seen; in the peduncles it is more opaque. There are no notes 
on the colors of the American specimens during life. The test sub- 
stance in the heads is of a rather gelatinous consistency, and is easily 
torn; that in the peduncles is firmer and tougher. The largest colony 
(of flattened club-shaped form) measures about 35 mm. long. 
The zooids are large, when Avell expanded from 3.4 mm. to 5 mm. 
Text-fig. 6. — Holozoa clavata (Sars). Three colonies. 
natural size. 
long, and have one or more vascular processes extending from the 
posterior end of the abdomen. The branchial aperture is six-lobed or 
sinuate; the atrial may or may not have its anterior border produced 
into a distinct languet. The oral tentacles are of two sizes placed 
alternately. 
The branchial sac has the usual four rows of stigmata with the inner 
transverse vessels crossing the stigmata, as described above. There 
are about 18 stigmata in a row on each side; the last two or three 
stigmata (those nearest the endostyle) become successively shorter 
as shown in text-fig. 7. There are three long dorsal languets. 
The stomach is ovate with thin walls bearing numerous narrow and 
not very conspicuous internal ridges, the prevailing course of which 
is generally longitudinal, but they always exhibit more or less irregu- 
larity in their arrangement, and in some individuals curve and anasto- 
mose to such an extent as to form merely an irregular network. The 
niunber as well as the prominence of the ridges is exceedingly variable. 
In some specimens they are conspicuous ; in others they are so low as 
easily to escape notice, or the stomach walls may be actually smooth. 
The brood pouch is a long curved tapering caecum-like sac, arising 
