CNIDARIA AS THE ONLY COELENTERATA 



11 



living prey. In those cases where there are no. tentacles it seems 

 more probable that their absence is a secondary phenomenon. 

 The fact is noteworthy that Ctenophora never form more than 

 one pair of tentacles, and that they show no leaning to 

 polymeri2ation which nevertheless can be observed to have 



Fip-. 2. An antho medusa species: Ctenaria ctenophora Haeckel. 

 (After Haeckel.) 



