10 



ZOOLOGY 



SECT 



a common case or investment. Both occur in the sea at various 

 depths. 



Cephalodiscus has an investment (Fig. 720) in the form of a 

 branching gelatinous structure, which is in some species beset with 



FIG. 721. Cephalodiscus dodecalop bus. Entire zooicl. (After Mclntosh.) 



numerous short filiform processes, and contains a number of tubular 

 cavities with external openings, occupied by zooids. The latter 

 (Fig. 721) are not in organic continuity, so that, though enclosed in a 

 common investment, they do not form a colony in the sense in which 

 the word is used of the Polyzoa or the Hydroid Zoophytes. They 



