4 TUNICATA. 703 
A. Compound Ascidians. Common body gelatinous, or gela- 
tinoso-coriaceous, polymorphous, often expanded, incrusting the 
surface to which it adheres. 
Botryllus GERTNER. Body of the animalcules not distinguished 
into thorax and abdomen; branchial aperture circular without rays. 
Several clusters of animals, each of them mostly stellate. 
Sp. Botryllus Schlosseri Sav., Aleyonium Schlosseri L., Botryllus stellatus 
Ga#rRtn., Pauy. Spic. Zool. x. Tab. 1v. figs. 1—5, Savieny 1. 1. Tab. xx. 
fig. 5 ;—Botryllus polycyclus Saviany 1. 1. Tab. tv. fig. 5, Tab. xxt. (re- 
peated in Guiérin Jconogr., Mollusqg. Pl. 35, fig. 1). In this and other 
species every group has a common central cavity, into which the posterior 
aperture of each several animalcule opens. In other species the several 
animalcules are not placed circularly round such a cavity, and the two 
openings of the body are closer together. The common mass is penetrated 
by canals. Here belong the species which Savieny refers to his first divi- 
sion of Botryllus; M1itNE Epwarps forms of them, with the addition of 
some new species first described by him, a separate genus under the name — 
of Botrylloides. 
Didemnum Say. (and EHucelium eyusd.) Common body sessile, 
incrusting, without central cavity. Animalcules divided into two 
separate parts, with branchial sac separated like a thorax from the 
abdomen. Anal orifice without rays. Many groups of animals 
collected in a common body. 
a. Branchial orifice rotundate, destitute of rays. 
Eucelium Sav. 
6. Branchial orifice with six equal rays or lobes. 
Didemnum Sav., Didemnum and Leptoclinum Minne Epw. 
Sp. Didemnum candidum Sav. 1.1. Pl. tv. fig. 3, Pl. xx. fig. 1, Cuv. R. 
Ani., Moll. Pl. 129, fig. 3, &e. 
Polyclinum Sav. (and Aplidium ejusd.) Common body sessile, 
polymorphous, often incrusting. Many groups of animalcules col- 
lected together in a common body. Animalcules divided into three 
separate parts, with ovary and heart behind abdomen contained in 
the last part. Branchial orifice sexradiate; anal orifice without rays. 
Sp. Polyclinum constellatum Sav. 1. 1. Pl. rv. fig. 2, Pl. xvut. fig. 1, GUERIN 
Iconogr., Moll. Pl. 35, fig. 4; on the coasts of the island Mauritius ;— 
Aplidium ficus Sav., Alcyonium ficus L., Evtis Corallines, Pl, xvii. fig. 
b. B, &e, 
