NEW INTERPRETATION OF CNIDARIA 255 



considers my interpretation as undiscussable, for he maintains 

 a complete silence about it; it is improbable that my inter- 

 pretation could have remained unknown to him since he must 

 have read at least my article which appeared in Systematic 

 Zoolog}!. 



When we have suceeded in suggesting that it was at least 

 probable that the Cnidaria, with Anthozoa as their first group, 

 had evolved from Turbellaria, we soon meet a new problem, 

 i.e. which subgroup of Turbellaria can be considered as the clo- 

 sest relation of the Cnidaria? In our attempts to solve problems 

 where the theoretical or logical conclusions cannot be avoided 

 (they can also be called speculations) we must be constantly 

 aware of the fact that the animals concerned had long ago 

 ceased to exist, that the information at our disposal covers 

 the recent animals only, that no transitional forms are avail- 

 able, and that nothing is known of a possible existence of 

 some other "side branches" which have now disappeared 

 without leaving any trace. We must be content with the 

 determination of the deg "ees of probability. 



Initially we were helped, by the fact that among the recent 

 animal groups we do not find progressive and specialized 

 species only, but also some more primitive forms. The 

 possibihty of arriving at a correct solution of such a problem 

 is therefore not quite so small. 



Scholars, in their earlier endeavours to make phylogenetic 

 deductions, have tried to go far back and to identify indif- 

 ferent initial forms or ancestors. The planula hypothesis can 

 be mentioned here as a typical example which is at the same 

 time closely connected with our problem itself. It was conclud- 

 ed, under the influence of the so-called "fundamental biogene- 

 tic law" that a polycellular organism had originally existed, 

 similar to a planula of Cnidaria; and that it had evolved from 

 an equally hypothetic gastraea which itself was considered 

 as a possible starting point for the evolution of three groups 

 of Coelenterata: Spongiaria-Cnidaria-Ctenophora. It was the 

 third group only which had formed the basis for further 



