THE NEW GEXE-\LOGICAL TREE 439 



ancestors which they had in common with the Enteropneusta. 

 Their evolution proceeded from this ancestral form towards 

 a tubicolous way of hfe and it had therefore been separate 

 from that of other tubicolous Oligomeria. 



A derivation of the freely moving Chordoma from such 

 tubicolous Ohgomeria as the Phoronida and the Pogonophora 

 seems to be rather improbable. These two subt}-pes are clearly 

 specialized, the Pogonophora even more so than the Phoron- 

 ida. A complete loss of the digestive system in a non-parasitic 

 animal type can certainly be considered as a unique case. It is 

 clear that nothing could ever have possibly evolved from 

 such speciaHsts; they represent blind side alleys of evolution 

 which are so numerous in the animal world. It is unnecessary 

 to argue and prove that no evolution in the direction towards 

 the Chordonia with the Brachiopoda and the Ectoprocta, two 

 completely sessile classes of the OHgomeria, as initial forms 

 had been possible. The situation as it appears from our stand- 

 point — which we consider as the best founded point of view — 

 is such that the Enteropneusta only can be taken into con- 

 sideration as a possible initial form for the evolution of the 

 Chordonia. Even if it is unnecessary, I nevertheless wish 

 to state exphcitly that quite naturally I do not see in the 

 recent Enteropneusta the ancestral forms of the Chordonia; 

 these ancestral forms were in reaUty at the same time ancestors 

 of the present-day Enteropneusta and Hved as such in the 

 remotest geological past. From these ancestors had evolved 

 divergingly (or I could also say in parallel) on the one hand 

 the burrowing Enteropneusta, and on the other hand the 

 Chordonia which had returned to a freely moving Hfe. From 

 these freely moving Chordonia a new subt^^pe (class) had 

 again evolved, in no way accidentally, of the sessile Chordonia 

 wliich are represented by the blindly ending side branch of 

 the Tunicata. 



When we try to derive the Chordonia from the primitive 

 Enteropneusta, among the OHgomeria, we meet with ap- 

 parently the greatest difhculty— besides some other problems 

 29* 



