NEW INTERPRETATION OF CNIDARIA 249 



finds the primitive form in an "Urcoelenterate" with four 

 gastral pockets and thus with a radial symmetry; yet at the 

 same time he admits the possibility that this "Ausgangsform 

 der Cnidaria vor ihrer Festsetzung einige bilaterale Ziige des 

 Baues schon besass." Jagersten, on the other hand, constructs 

 a completely new initial form which he calls a "bilatero- 

 gastraea" (Fig. 55). This, at first sight, original and 

 ingenious construction, however, has all the characteristics 

 of a so-called "suitcase theory" (Kofjertheorie). Jagersten places 

 into this constructions all those elements which he afterwards 

 needs in his subsequent derivations. This is clearly a combina- 

 tion of the gastraea theory as it had been proposed by Haeckel 

 (Jagersten [1955:333] himself admits that it is a "modification of 

 Haeckel's theory"), and of the enterocoele theory as it had been 

 proposed by Sedgwick, with the addition of an otherwise sound 

 idea which had already been supported by several other scholars 

 that the structure of the primitive form had after all been 

 bilaterally symmetrical, and that this form as such had crept 

 over the bottom of the sea. The construction as it has been 

 proposed by Jagersten show^s therefore numerous advantages 

 over the interpretation as given by Remane. Yet if we 

 look at Jagersten's bilaterogastraea from a somewhat dif- 

 ferent angle we find in it a similarity to the primitive Turbel- 

 laria, a similarity which Jagersten himself failed to notice. 

 Jagersten had to overcome both great and small difficulties 

 when he derived all other larger types of Eumetazoa, includ- 

 ing sponges, from this bilaterogastraea. These difficulties force 

 him to take refuge in a very large number of speculations 

 (it is quite true, however, that we cannot avoid speculating 

 to a certain extent). We miss among these large types (Cnidaria, 

 Ctenophora, Coelomata) a direct derivation of the actually 

 coelomless Coelomata which do not possess an anal orifice 

 (by a coelom we understand in reality a perigastrocoele and 

 not a gonocoele). Jagersten, however, mixes up these two 

 notions ; he believes the enterocoele theory to be changed 

 now into a gonocoele theory, as he states this himself 



