248 THE EVOLUTION OF THE META20A 



well as the oldest Metazoa as a whole had been bilaterally 

 symmetric animals we can think Steinbock, too, considers the 

 Anthozoa as the most primitive Cnidaria. I think that I am 

 justified to include Sir Gavin de Beer among those prominent 

 zoologists to have repeatedly evaluated positively my sugges- 

 tions regarding the evolution of the Cnidaria (1948, 1951, 1958). 



The Probable Origin of Cnidaria 



We come now to the question of what the origin of Cnidaria 

 could be if w^e declare the Anthozoa as the most primitive 

 Cnidaria? Is it impossible to change the now prevalent opinion 

 according to w^hich the Cnidaria evolved as the lowest Eume- 

 tazoa from some colonies (cormi) of Flagellata by way of the 

 three stages moraea-blastea-gastraeaPThis second question also 

 remains if we take into consideration other initial forms, e.g. 

 a placula, a parenchymella, a parenchymula, a planea, a planula, 

 a phagocytella, etc., instead of a gastraea; all these forms are 

 in reality variants only, which do not differ in principle from 

 the classical form even if they are held in high esteem by a 

 number of scholars. 



At first, one feels inclined to say that a reversion of the 

 line ot evolution ot the three subgroups of Cnidaria is incom- 

 patible with the traditional derivation of Cnidaria from an 

 ancestral form similar to a gastraea. The difference between 

 such a form and an anthopolyp seems to be too great and a 

 more extensive change of the old interpretation seems to be 

 a necessity. So tar there have been, to my knowledge, two 

 attempts only to overcome these difficulties. The first such 

 attempt was made by Remane (1920), and the second by 

 Jagersten (1955). The motives for such attempts lay in 

 both these cases outside the sphere of the comparative 

 morphology of Cnidaria; both were closely connected with 

 the problem of the formation of the coelom. Remane 

 adheres in his interpretation closer to the old concept. He 



