PREVIOUS INTERPRETATIONS OF CNIDARIA 153 



connection with the sessile way of hfe, another process takes 

 place which, however, follows a progressive line of evolution. 

 This process does not affect the gonads themselves but rather 

 their bearers and the immediate surroundings in the cormus. 

 Events have been created by these gonads which have led 

 to far-reaching morphogenetic processes typical of Cnidaria 

 but which, however, can also be found in a similar form in 

 many other animal types. Due to polymorphism, special 

 individuals had evolved which have later developed into 

 specific bearers of gonads. This has finally led evolution to the 

 complex gonosomes besides the medusoid generation (Fig. 

 31). 



The Alternation of Generations in Cnidaria 



It is in agreement with our thesis of the origin of Cnidaria 

 that we find in the Anthozoa the most primitive conditions 

 that can be observed in connection with the alternation of 

 generations. The primarily solitary species of Anthozoa deve- 

 lop into sexually ripe individuals directly from larvae. 

 In some species as, in Gonactinia prolifera^ we can observe 

 that an asexual reproduction by way of transverse division 

 takes place before the animal becomes sexually mature; 

 this is also the case in numerous Turbellaria. The transverse 

 division is followed by sexual maturation and the only 

 difference that exists between the two generations is that 

 one had been reproduced sexually and the other asexually. 

 In this case we can already speak of an alternation of 

 generations if we attach greater importance to the type of 

 reproduction than to the morphological or eventually ecological 

 differences. It is my firm conviction that it is senseless to 

 declare a form to be a larva when it is produced sexually 

 and when itself reproduces asexually. Only a form which had 

 been produced sexually can further develop through a pelagic 

 larva. Finally in the solitary species all individuals become, 

 in all probability, sexually ripe regardless of the way that 



