254 THE EVOLUTION OF THE METAZOA 



preserved. It has already been show n that the last traces of 

 the hermaphroditic state can still be found in Anthozoa. It is 

 probable that Cnidaria branched off from their turbellarian 

 ancestors even before the same was done by Nemertinea and 

 by Gastrotricha. 



It has already been shown that all the differences that exist 

 between the anthopolyps of the Cnidaria and the Turhellaria 

 can be divided into two groups: the first group includes those 

 changes which had been brought about by the transition to 

 the sessile way of life usually characterized by some kind of 

 reduction, and the second group which, though connected 

 with the sessility, must be interpreted as a result of a prog- 

 ressive evolution (cnidae, tentacles, strong contractility, etc.). 

 All these properties can be found developed earlier than in 

 Cnidaria, even if then only to a lesser degree. 



In view of the fact J:hat there is now hardly a single zoologist 

 who could doubt that the Turbellaria represent the starting 

 point in the evolution of many other animal types, it may 

 be possible to accept at least as a possibility that Cnidaria, 

 too, had evolved from some turbellarian ancestors, provided 

 that the anthopolyps are the most primitive among the 

 free and solitary polyps of Cnidaria. There are now few 

 experts in Turbellaria who still support the interpretation which 

 sees in the acoelous Turbellaria as well as in the Turbellaria 

 as a whole, a result of a retrogressive evolution. The most 

 prominent among these scholars is Marcus, a well-known 

 expert in Turbellaria, who goes his own way in his inter- 

 pretations of the phylogeny of the animal world (E. Marcus, 

 1958:52, Fig. 1). It would take us too long to investigate his 

 opinions in detail here. He and I speak two different langu- 

 ages, and his line of thought remains unintelligible to me 

 (e.g. when Marcus considers the larvae of Anthozoa to repre- 

 sent a special animal group; or, when he refers, on one hand, 

 to a similarity between the form of cleavage in Ctenophora, and 

 on the other in the ctenostome and cheilostome Ectoprocta, 

 which he prefers to call Bryozoa). Marcus too, it seems. 



