250 THE EVOLUTION OF THE METAZOA 



(1955:353) The final result of all this is that the intestinal 

 pockets become at one time an enterocoele (= perigastrocoele), 

 and another time a gonocoele (in a large number and without 

 any actual order in Nemertinea). This, ho\\ever, is not the 

 right place to make an analysis of the other statements that 

 have been made by Jagersten. 



A criticism of HaeckeFs concept of the origin of Cnidaria 

 must naturally be extended to the modifications of the 

 same concept as found in the works by Remane and by 

 Jagersten (together with Naef); they have both preserved 

 Haeckel's basic ideas. The situation becomes even worse, 

 because we find here, in addition to the old mistakes, a new 

 blunder also, i.e. the idea of a colonial origin of Eumetazoa 

 (Coelenterata); moreover, the old idea of enterocoely is 

 here found transferred to an earlier phyletic stage in order 

 to preserve the validity of Haeckel's so-called "fundamental 

 biogenetic law" and of the gastraea theory, while at the same 

 time not a single real argument is given by the author which 

 could support his suggestions. The only progress which can 

 be found in Jagersten's interpretation, if it is compared with 

 similar older combinations, lies in the fact that he believes 

 in an early transition of the "blastea" to a life on the sea 

 bottom and, in connection with this, in a transformation of 

 the form of its body in the sense of a bilateral symmetry 

 (this constructed primitive form has therefore been called by 

 the author a bilaterogastraea*). 



The main difference which exists between Jagersten's 

 standpoint and the interpretation proposed in the present 

 study is that we both come to the conclusion that it is neces- 

 sary to reverse the phylogenetic sequence of the subgroups 

 of Cnidaria while at the same time we have both begun 



* Prof. O. Steinbock has kindly called my attention to the fact that 

 as early as in 1874 Haeckel had suggested that some gastraea which had 

 sunk to the sea botton began to creep over the substratum and in this 

 way had developed bilateral symmetry; it was called by Haeckel a gastraea 

 bilateralis (repens). 



