THE OCEAN WORLD. 



rocks and other marine bodies, and generally at a fixed depth. Asddia 

 microcosmus, a Mediterranean species, represented in Fig. 123, may 

 be given as an example of this division of Tunicates. The name of 

 microcosmus, or the little world, is probably given to the species from 



its being inhabited by quite 

 an animated colony of algae 

 and corals, which dwell 

 upon its surface, and give 

 it a very peculiar, but not 

 very attractive, appearance. 

 The flavour of these mollus- 

 coids is very strong, which 

 does not, however, hinder 

 the poorer dwellers on the 

 sea-shore from eating them. 

 Phalhisia is another genus 

 of the group. Phalhisia 

 grossularia is of a reddish 

 colour, and about the size 

 of a currant-berry : it usually 

 lodges itself in the oysters 

 of certain localities. At 

 Ostend another species, 

 Phallusia ampulloides, is 

 found in prodigious quan- 

 tities in the oyster parks, 

 and is parasitic on living 

 lobsters. 



Social Tunicates em- 

 brace such forms as are 

 connected together by a 

 common stoloniferous pro- 

 longation, but remain free 



and unconnected in all 

 other respects. Asddia 

 pedunculata (Fig. 124) may 

 be given as an example. 



Fig. 124. Ascidia pedunculata (Milne-Edwards). 



The Composite Tunicates are still more intimately associated 

 together ; a great number of these little beings living together in a 

 single mass. Such are the many species of such genera as Botryllus 

 and Pyrosoma. 



Botryllus is a genus perhaps the most interesting of all those under 



