GYMNOBLASTEA ANTHOMEDUSAE 



271 





Fam. Tubulariidae. This important and cosmopolitan family 

 is represented in the British seas by several common species. 

 The zooids of the hydrosome of Tubularia have two circlets of 

 numerous filiform tentacles. The gonophores are adelocodonic, 

 and are situated on long peduncles attached to the zooid on the 

 upper side of the aboral circlet of tentacles. The larva escapes 

 from the gonophore and acquires two tentacles, with which it 

 beats the water and, assisted by the cilia, keeps itself afloat for 

 some time. In this stage it is known as an " Actinula." 1 



Fam. Ceratellidae. The colony of Ceratella may be five 

 inches in height. The stem and main branches are substantial, 



Fig. 133. Ceratella fusca. Abcmt nat. size. (After Baldwin Spencer. 2 ) 



and consist of a network of branching anastomosing tubes 

 supported by a thick and fenestrated chitinous perisarc. The 



1 The aberrant genus Hypolytus (p. 262) may belong to this family. 

 2 Spencer, Trans. Roy. Soc. Vict. 1892, p. 8. 



