PREVIOUS INTERPRETATIONS OF CNIDARIA 219 



cialized remnant of the formation of stolons and in this con- 

 nection also of cormi. 



As in the case of budding, regeneration which is well de- 

 veloped in Anthozoa (just as in Turbellaria) regularly takes 

 place from out of the body wall. Tentacles which have been 

 cut off are unable to develop into a whole new animal appa- 

 rently because of the absence of mesohyl. The species Bolo- 

 ceroides however, represents according to Okada and Komori 

 (1932), an exception. This is a case of specialization. 



Even in the evolution of asexual reproduction the climax has 

 been reached in Hydrozoa, both as regards the frequency and 

 variety combined with specialization (the formation of poly- 

 morphic and individualized cormi), as well as in the sense of 

 the so-called atypical formation of buds without the partici- 

 pation of the intestinal epithelium. The transverse division 

 recedes completely into the background, and the individuals 

 (hydranths) more and more lose their ability to form buds and 

 to regenerate. The colony prefers to abandon a damaged polyp 

 and to renew it out of the un -differentiated "coenosarc" 

 (Hadzi, 1915) than to replace it bv means of renovation 

 (Fig. 39). 



In Hydrozoa, just as in the case of Scyphozoa, medusae are 

 developed (and they certainly had been developed during the 

 geological past) as special sexual individuals primarily by way 

 of asexual reproduction only, combined with alternation of 

 generations. It is certain that medusae had been evolved by the 

 two groups in two completely different ways, once by means 

 of a transverse division of the maternal polyp, and the second 

 time by way of budding either of the polyp or of the medusa. 

 On the other hand we find that in the two groups, species 

 which had evolved in the same way where the medusa 

 is developed directly from an tgg and where the benthonic 

 polyp generation has completely disappeared (the hypogenetic 

 species). 



It is in the Hydrozoa only that divisions of whole parts of 

 cormi can serve the purposes of reproduction and of spreading. 



