CNIDARIA AS THE ONLY COELENTERATA 



63 



Fig. 11. Some cases of polymerization and oligomerization of 

 tentacles of hydroid polyps; A, Clava sp. (after Hyman). B, 

 Syncoryne sp. (from Dogiel). C, Pennaria cavolinii, (from Broch). D, 

 Cladonema sp. (from Hincks). E, Cladocoryne floccosa (orig.). F, L<7r- 

 sabellari{m{iiom Dogiel). G, Monobrachium parasiticus {itom. Dogiel). 

 H, Halocoryne epit^oica (after Hadzi). 



of oligomerization. As a rule, this will not be difficult when we 

 make detailed comparisons. We meet in our study of the 

 animal world, at every turn, with the phenomena of polymeri- 

 zation and oligomerization. In this connection some regulari- 

 ties have been observed; above all the fact that in case of 

 oligomerization a fixed number of multiplied, and thus homo- 

 logous and homodynamoas, parts is found preserved (e.g. in 

 Cnidaria four, six, eight, and their products; eight in Ctenop- 

 hora; five in Echinodermata; etc.). 



