THE NEW GENEALOGICAL TREE 431 



Finally we must not completely bypass the Graptolitha, an 

 extinct class of the Oligomeria, in spite of the fact that in the 

 present study we take into consideration the recent groups 

 only. There can be no doubt that these Graptolitha must be 

 classified among the Oligomeria and not among the so-called 

 Coelenterata. They obviously represent a case parallel to that 

 of the Siphonophora, among the Hydrozoa, i.e. a type w ith 

 polymorphic cormi (colonies). We will not further discuss 

 these Graptolitha because they represent a blindly ending side 

 branch of the Oligomeria, and because they are now complete- 

 ly extinct. 



The Problem of the Inclusion of the Sipunculida 

 Into the Phylum Oligomeria 



Following the interpretations suggested by many zoolo- 

 gists, and among them many specialists, I considered earlier 

 that the Sipunculida should be classified among the Polymeria 

 and that they should be looked upon as closely related to the 

 Echiuroidea and the Annelida. After a thorough and critical 

 revision of the actual facts, however, I have now come to the 

 conclusion that some older zoologists had suggested correctly 

 — among them especially Arnold Lang who was followed in 

 this respect by Haeckel — that the Sipunculida must be more 

 clearly separated from the Annelida and that they should be 

 classified among the Prosopygia. 



As regards the conditions of their perigastrocoele we can 

 find that the Sipunculida show even more oligomerous propert- 

 ies than all the remaining classes of the Oligomeria. They have 

 even lost last traces of an intestinal and of an external segmen- 

 tation; their perigastrocoele has become a completely uniform 

 organ. They show neither mesenteries nor dissepiments, a fact 

 which is clearly connected with a change in their intestinal 

 conditions. Their anal opening w^as transferred to the anterior 

 part of the animal body, and their intestinal tube is not only 

 U-shaped as in Phoronidea but it is also coiled. They live as 



