THE NEW GENEALOGICAL TREE 441 



evolution of their extremities. This had again been followed 

 by a (third) polymerization and by a more sinuous type of move- 

 ment which is typical of snakes. Among other changes and 

 innovations that can be found in the Chordoma we must 

 mention above all the formation of an internal axial skeleton, 

 with the chorda dors alls at the beginning. 



In the recent animals we unfortunately find a deep gap 

 between the Oligomeria and the Chordoma. This transition 

 had taken place in the remotest geological past. The transition 

 was made by animals whose soft consistency had little chance 

 of preservation as a fossilized form. The speed itself of the 

 evolution was also in all probabiUty increased. Finally, it also 

 seems that it w^as just this transitional stage which had lived 

 not in a pure sea but, at least partly, in a brackish or 

 fresh water and this again is an unfavourable circumstance 

 for the preservation and for the discovery of such fossilized 

 remains. We have therefore no other alternative but to take 

 refuge in the comparative morphology of the recent adult 

 forms and of the developing stages and at the same time 

 to use our imagination within proper limits. 



The Fourth and the Last Phylum of the Eumetazoa; 

 the Chordonia 



It is in no way surprising in view of the available material 

 to see how many different ideas, hypotheses, and theories have 

 been proposed so far in various treatises and even books 

 about the origin of the Chordata, and thus also of the Ver- 

 tebrata. Only little additional material has recently come to 

 light, such as the discovery of the fossiUzed remains of the 

 extraordinarily old chordate Jamojtius. It would transcend the 

 Limits of the present book if we discuss in detail this problem 

 here. It does not even belong to the sphere of my own 

 research. I will therefore limit myself to show only how this 

 problem could be solved if studied from our standpoint and 



