64 



THE EVOLUTION OF THE META20A 



Fig. 12. Oligomerization and polymerization of tentacles in 

 hydromedusae, A, Podocoryne carnea (after Grobben), B, Stomotoca 

 sp. (from Hyman); C, Steenstrupia sp. (after Mayer); D, Bougain- 

 viLea sp. (after Broch); E, Aeqiiorea sp. (after Hyman); F, Obelia sp. 

 (after Colosi). 



The origin of the metamerization, one of the most important 

 problems of the comparative morphology of the metazoa, 

 is closely connected with that of the polymerization and of the 

 oligomerization. The question naturally arises; can we con- 

 sider that the all-important metamerization has been developed 

 out of the polymery, by way of a multiplication of whole 

 regions of the animal body; or, conversely, by way of an initial 

 polymerization of individual organs (this is usually called the 

 psetidomerit(ationP This is followed first by a "genuine meta- 

 merization," and afterwards either by a wholesale oligomeri- 

 zation with formation of regions, or, by a general oligomeri- 

 zation and a corresponding change of the way of life (the origin 

 of the large type of Oligomeria). We will later return to discuss 

 this problem. 



