466 THE EVOLUTION OF THE METAZOA 



the position of the MoUusca, etc.). If we represent the left- 

 hand main branch as a continuation of the right-hand main 

 branch— and this is actually the main change we have to 

 make— we must necessarily also make some other minor 

 changes in order to reach finally a clear separation of the 

 Ameria, Polymeria, and the OUgomeria. 



All these differences appear even slighter if we simplify 

 the diagram proposed by Hyman in the way this was done, 

 for example, by Guthrie and Anderson (1957:219, Fig. 73, 

 Fig. 62), and if we do something similar with my attempt 

 to construct a genealogical tree of the animal world. 



Thus it appears to me that in spite of the apparently great 

 differences of opinion which presently still exist regarding 

 the true course of the evolution of animals we will nevertheless 

 reach a general accord between all the zoologists in a not 

 very distant future. The spectrum has certainly become 

 now considerably narrowed. The main difference can be found 

 in the fact— which appears clearly in my discussion and in 

 my systematic survey— first, that I consider the Turbellaria as 

 the starting point of the whole evolution of the Eumetazoa, 

 and secondly, that I suggest that we must discontinue to use 

 in our taxonomic concepts the difference which is found at 

 the basis of the two groups, the Protostomia and the Deutero- 

 stomia; these two parallel lines of evolution must now be 

 abandoned. It will not be difficult to solve all the remaining 

 problems. 



