NEW INTERPRETATION OF CNIDARIA 257 



protected with a cuticle which serves as a means of defence 

 and support. 



In all probability the Temnocephala have preserved their 

 free mobility because of their epizoic way of life, and in this 

 they differ greatly from Cnidaria. The recent researches that 

 have been made by Matjasic (1959) have shown that this 

 free mobility can even be very active. It is due to their free 

 mobility that Temnocephala have also preserved their ability 

 to pair; this is the reason why we can still find in Temno- 

 cephala the typical complex turbellarian hermaphroditic genital 

 apparatus, while the same has been lost in Cnidaria which 

 have evolved into purely sessile animals. 



I believe that I am not wrong when I conclude, on the 

 basis of well-known facts, that phylogenetically (and also 

 geologically) the Temnocephala must be younger than the 

 Cnidaria. The Temnocephala can still be considered as Tuibel- 

 laria; they had branched off from their rhabdocoelan ancestors 

 and have finally developed into a new subtype, into a new 

 order. They are therefore not related to Cnidaria in a direct 

 line ; they rather represent a parallel development to the 

 evolution of the latter, a development which can nevertheless 

 prove helpful in our attempts to understand the way the 

 Cnidaria had evolved from their turbellarian ancestors. 



The case of Temnocephala can thus serve us as a kind of 

 pattern. In spite of objections made by several zoologists, 

 and above all by Beklemischev and by Reisinger, we will 

 suggest that like a temnocephalian the primitive anthopolyp 

 had raised, first for a briefer period, and later permanently, 

 its posterior end w^hich is now its aboral end. The oral orifice 

 which was originally placed on the ventral side, even if in 

 the anterior part of the body, has been transferred to a purely 

 terminal position when the animal began to be attached to 

 the ground. The Temnocephala had thus repeated the first stage 

 in the older evolution of Cnidaria; yet here they have stopped, 

 or rather they have evolved further in their own direction 

 as epizoic, or let us better say, as ectoparasitic animals. They 



