THE NEW GENEALOGICAL TREE 413 



Tardigrada, Pentastomida, Onychophora, Arthropoda. Such 

 a classification can be well defended as well as a classification 

 into three subphyla. In this classification we place an inter- 

 mediate group which has stumps only as extremities (Tardi- 

 grada, Onychophora, Pentastomida) between the Annelida 

 which have no extremities at all, and the Arthropoda which 

 are equipped with the articulated extremities. The question 

 remains open w^hether we can consider these forms as a primary 

 element or whether they had emerged as a result of a secondary 

 development. We think that it is sufficient to divide the Poly- 

 meria into two subphyla, the Annelida and the Arthropoda 

 (this is true at least for the recent Polymeria) because we find 

 that the stump limbed Polymeria do not only show closer 

 relationship connections with the Arthropoda but also because 

 they do possess extremities even if these extremities are very 

 simple or if they are remains only of such extremities (Penta- 

 stomidea). 



The dichotomy corresponds well, as this has already been 

 mentioned, to the two main Unes of the evolution of the 

 Annelida which have remained more primitive animals. From 

 these we derive the Oligomeria, i.e. the next higher phylum 

 which is as such the third phylum of the Eumetazoa. The 

 situation of the Annelida resembles that of the Turbellaria, 

 among the Ameria. In these the polymerization had reached 

 its highest development. On the other hand, we can soon 

 observe a trend to a sessile way of life and its necessary con- 

 sequences, a shortening of the body length and a reduction 

 of the polymerous state. The Arthropoda on the other hand, 

 the second main branch which had a much more exuberant 

 evolution, played a role similar to that of the Mollusca among 

 the Ameria. At the same time they far surpassed the Mollusca 

 because they solved much better, not only in water but above 

 all in the sea also (Crustacea), the problem of transition to a 

 Ufe on dry land by developing a tracheal system. Just as in the 

 case of the MoUusca, among the Ameria, we find that the 

 Arthropoda have still remained within the sphere of the type 



