THE NEW GENEALOGICAL TREE 369 



founders of the theory of Evolution, however, and above all 

 Ernst Haeckel, had the unfortunate idea of classifying them 

 as Coelenterata. A little later, before scholars succeeded in 

 identifying the completely aberrant ontogeny of Spongiae, 

 they were pronounced by Huxley (1875), Sollas (1884), and by 

 other zoologists to be a form which stands completely apart 

 from other poly cellular forms. And what had been the main 

 reason why the Spongiae with their special organisation and 

 way of life have continued to be considered as Coelenterata in 

 spite of the discovery made first by Metschnikoff of the special 

 character of their ontogenies ? It was again the fatal gastraea 

 theory as it was proposed by Haeckel! Spongiae occasionally 

 possess (as is also the case with the Eumetazoa) a freely swim- 

 ming larva which has on the w^hole the form of a blastula. 

 This form has therefore been considered as a recapitulation of 

 the blastaea. It is followed by a gastrula-like form which 

 again has been considered as a recapitulation of the gastraea. 

 Is there anything else that could be desired?! Haeckel, as a 

 master in this field, has also coined attractive names: Olynthus 

 and Ascon. In his scheme he placed them possibly close to the 

 Hydra and to the "typical" gastrula and the whole impression 

 reached in this way was quite convincing. This idyll was not 

 disturbed by an actually quite unpleasant fact that the "spon- 

 gian gastrula" becomes attached by means of its primitive 

 mouth, that it does not possess a digestive intestine, that it 

 subsequently develops a new opening at its "aboral" pole 

 whose function is rather that of an anal orifice than that of a 

 mouth (thus the Spongiae would therefore be a special type 

 of the Deuterostomata), and that the Spongiae show numerous 

 orifices (pores) in their body w^all where the sea water is 

 drawn by means of choanocytes (they substitute here the 

 digestive entodermal cells) into the internal system of canals 

 in order to be finally forced out through a larger opening (the 

 osculum) after it had gone through a special filtration system 

 and after its oxygen had been removed. As far as I know 

 there in not a single species of Spongiae which as such would 



