NEW INTERPRETATION OF CNIDARIA 333 



separate derivation of Spongiae from some cormi of Choano- 

 flagellata can be considered to be more acceptable than a com- 

 mon deduction of all the Metazoa from some colonies of 

 collar-less Zooflagellata. The former interpretation would 

 appear more plausible even if the case that there were no 

 Proterospongia were true, because no transitional form between 

 the Flagellata and the Eumetazoa has become known up till 

 now and in spite of this there are so many zoologists who 

 "believe" nevertheless in the latter type of derivation. In the 

 meantime another species of the Proterospongia has been disco- 

 vered (we have already mentioned this in our study) and there 

 can be no doubt about its nature. 



And what can be said of the argument or even "proof" of 

 the statement that the larvae of Spongiae possess ordinary 

 flagellated cells which are only subsequently, by way of 

 metamorphosis, developed into the choanocytes ? This should 

 prove, according to Marcus, that the Spongiae cannot be 

 deduced from the Choanoflagellata ! It seems as if the Spongiae 

 were the only animals which had no right to evolve special 

 early phases capable of swimming freely, and all zoologists 

 can see in them an example of recapitulation. The spongu- 

 lae are new forms like all the freely swimming larvae of the 

 Metazoa; the animal does not need any collars of cytoplasm in 

 order to be able to swim ; these collars can rather be consider- 

 ed as a hindrance. The spongulae do not feed independently. 



What can then be the value of the equation: germ layers 

 = the same origin? It is even less convincing than in the case 

 of flagella which have been just discussed. All the germ layers 

 are a product of a rationaUzed ontogeny. There are no, and 

 there never wxre any, germ layers in the Metazoa, not even 

 in their lowest forms. If, in spite of this, we wish to talk about 

 the germ layers (better, body layers) in analogy to the onto- 

 genetic conditions that can be observed in the higher Ver- 

 tebrata, we see that it is just at this point that there are radical 

 differences between the Spongiae and the Eumetazoa. These 

 differences cannot be simply dismissed with the nice phrase: 



