146 



ZOOLOGY 



SECT. 



Clathrozoon, an Australian genus, resembles it in having branched 

 and intertwined ccenosarcal tubes, the perisarc of which under- 

 goes fusion ; but the complex mass thus produced, instead of 

 forming an incrustation on a shell, is a large, abundantly branched, 

 tree-like structure, resembling some of the fan-corals or Gorgonacea 

 (vide infra). Ceratdla (Fig. 10G) has a similar fan-coral-like 

 appearance, with a branching axis composed of numerous inter- 



Fio. 106. — Ceratella fusca. About nat. size. (From Hickson, after Baldwin Spencer.) 



twining and anastomosing tubes ; but while Clathrozoon possesses 

 thecse, in Ceratella they are absent. 



A great simplification of the colony is produced in Myriothcla 

 (Fig. 105 2), in which the short coenosarc bears a single large 

 terminal hydranth, and gives off numerous slender branches which 

 bear the reproductive zooids (s). Even greater simplicity is found 

 in Corymorpha (3), in which the entire organism consists of a 

 single stalked polype, from the tentacular region of which the 

 medusae (m) arise. 



