30 TUNICATA. 



Localities, &c. The Botrylli and some other 

 of the encrusting genera are found on stones, and 

 on the surface of the rocks, but more commonly 

 on the broad fronds of Fuci, and other sea- weeds, 

 and more abundantly near low-water mark than 

 in deep water. Others of the compound races, as 

 Amceroecium, chiefly affect the sides of perpen- 

 dicular or overhanging ledges, the sides of caverns, 

 and similar dark situations. The Clavelinada 

 generally occur in little pools. ThQAscidite usually 

 adhere to stones and old shells, as do the Cynthia, 

 &c. ; but some of the smaller kinds adhere to sea- 

 weeds. When the Ascidiae are found within tide- 

 marks, they generally adhere to the under-side of 

 stones. The Salpa occur only at the surface of 

 the sea in summer, and when the weather is 

 tranquil. 



Identification. The condition of existence, whe- 

 ther solitary, social (budding in groups from one 

 root), or compound (many individuals being orga- 

 nically united into one or more systems) ; the con- 

 nexion of the mantle with the test, whether they 

 are united throughout, or only at the orifices ; the 

 texture of the test; the freedom or fixity of the 

 individual ; if fixed, the point and extent of its 

 attachment ; the relative situation of the orifices ; 

 the number of their rays when expanded; the 

 presence and number of eyes ; are important points 

 to be noticed in the discrimination of species in 

 this Class. The relative value of the characters 

 may be in some measure inferred from the order 

 in which they are here mentioned. 



organ" "The whole process differs from that common to 

 animals in general in nothing but the independence and appa- 

 rent individuality of the generative organ." (Phil. Trans. 1851, 

 Part II. p. 578.) 



