IV 



PHYLUM CCELENTERATA 



119 



the tentacles and mesenteries are always eight in number, 

 and the tentacles are pinnate, i.e., each of them consists 

 of a main stem with two rows of lateral branchlets. 



Only the Sea-anemones (with a few exceptions) and a 

 few Madrepore Corals remain simple, the rest all giving 



FIG. 55. Alcyonium palmatum. A, entire colony ; B, spicuies. (After Cuvier.) 



rise to more or less extensive colonies, of a variety of differ- 

 ent forms, by continuous budding. The structure of the 

 zooids is similar to that of the Sea-anemone in all essential 

 respects. In many of the Alcyonaria two forms of zooids 

 are to be distinguished in each colony (dimorphism of the 



