THE NEW GENEALOGICAL TREE 409 



differences on a functional basis) but also towards those 

 zoologists who consider correctly that these are morpho- 

 genetic processes which are typical of the ontogenies only and 

 which are therefore not recapitulations of some adult ancestral 

 form. I have discussed this problem extensively in another 

 study (Hadzi, 1948). 



It should be mentioned here that this high division of the 

 Coelomata does not depend exlusively on the destiny of the 

 primitive mouth during the ontogenies. It is usually combined 

 with other pairs of opposite characteristics, above aU the type 

 of development of the perigastrocoele (the Ecterocoelia and 

 the Enterocoelia, according to Hatschek, which have already 

 been discussed), and the position of the cerebral process along 

 the body axis (Epineuria-Hyponeuria). Even if there are some 

 differences in special points between all these classifications we 

 must nevertheless admit that there really exist such groupings 

 of characteristics. The origin of these differences, however, can 

 also be interpreted with the same justification in another way 

 by means of which we can create an even more probable con- 

 struction ot the genealogical tree where the "function" of the 

 so-called Tentaculata can be seen even more clearly. Those 

 who accept the thesis of an evolution of the two main branches 

 of the Coelomata from a common root run into great difficul- 

 ties as soon as they try to explain why the protostomial state 

 on the one hand and the deuterostomial state on the other had 

 evolved with all the other differences which appear together 

 with them. They have therefore been obliged to take refuge in 

 a very hypothetical and therefore improbable construction as 

 has already been shown here. 



Both the facts as well as the working method show that it 

 is much more probable that the two taxonomic units which 

 are known under the names of Protostomia and the Deutero- 

 stomia had not developed side by side, i. e. parallel or diverg- 

 ing from a common root, but rather one after the other, so 

 that first the Polymeria evolved from the amerous Eucoelomata 

 (they are both grouped together as Protostomia), and the 



