166 MANUAL OF NATURAL HISTORY. 



first shewed the true relations of the animal and 

 its position among the tunicated Mollusks. 



VI. CLASS. TUNICARIES (Tunicata). 



Animal acephalous, with a soft organized coria- 

 ceous or gelatinous test or shell provided with a 

 branchial and an anal orifice ; mantle forming an 

 interior coat ; gills attached wholly or partly to 

 inner surface of mantle ; mouth without labial ten- 

 tacles ; animals single or aggregate ; fixed or free. 

 Hermaphrodite. 



1. FAMILY. Ascidians (Ascidiidse). Body sacci- 



form, gelatinous or coriaceous, fixed at one 

 end, free at the other, with two more or less 

 prominent orifices ; isolated or gregarious, 

 not united by a common integument. 



2. FAMILY. Social-Ascidians (Clavellinidse). In- 



dividuals each having its own heart, respira- 

 tion, and system of nutrition ; but fixed on 

 peduncles that branch from a common creep- 

 ing stem, and all connected by a circulation 

 that extends throughout. 



3 FAMILY. Compound - Ascidians (Botryllidse). 

 Animals oval, adhering by their sides in a 

 greater or less number so as to resemble a 

 single complex animal ; each individual with 

 distinct branchial and anal orifices. 

 ]. Polydininm. Body divided into three 

 distinct portions, or a thorax, a superior- 

 abdomen, and a post-abdomen. 



