THE NEW GENEALOGICAL TREE 391 



code can be grouped together because they show a closer 

 relationship also in other respects. They could therefore be 

 called the Acoelomata ; } et this name can be misleading because 

 in all the subgroups of the Acoelomata we can find some kind 

 of a coelom cavity. It will be therefore better to make the 

 classification on the basis of the coelom conditions while at 

 the same time another very important property is also taken 

 into consideration (this in combination with many others!); 

 this is the fact whether the metamerized perigastrocoelic sacks 

 are primarily absent or present. In this way we can get the 

 two groups, the Ameria and the Polymeria. We can see that 

 the special coelom which surrounds the intestinal canal 

 emerges, as it seems suddenly (this at least is the impression 

 we can get now!), and from the very beginning in a metamer- 

 ized or polymere form. In this way we meet here with an 

 important gap which must be taken into consideration by the 

 systematists and by the taxonomists. Later we will discuss this 

 problem more in detail. Let us now first turn to the notion 

 and to the taxon Ameria. 



The First Phylum of the 'Eumeta^^oa : the Ameria 



The Turbellaria are according to our interpretation the 

 earliest Eumetazoa and as such they represent a starting point 

 of an evolution that radiated into several directions. There 

 are not less than fifteen distinct subtypes— we believe that it 

 is sufficient if we give them the taxon of classes— which evolv- 

 ed from these Turbellaria, and these classes again evolved 

 into numerous subgroups (ordines). We can notice some dif- 

 ferences in the levels reached in the organization of all these 

 classes of the Ameria which are due to the various ways of 

 life the species belonging to these groups had to adopt. Here 

 wx can find forms which Hve in various environments as 

 freely living animals, as parasites, animals which burrow in 

 the sea bottom, semi-sessile and fully sessile (evolved even 

 several times!) species. The extent of this difference can be 



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