THE NEW GENEALOGICAL TREE 443 



been discussed above all by Boveri (1892) and by Goodrich 

 (1902) and do not seem to disprove the interpretation that the 

 Chordoma did not developed directly from the ancestors of 

 the recent Annelida and that instead this evolution was 

 indirect, by way of the Oligomeria. This is how we can 

 explain the reactivation of certain elements in the Chordonia 

 while the same elements have been lost in the recent Oligo- 

 meria. 



We can divide all the hypotheses which derive the Chordo- 

 nia from the Oligomeria into two groups. According to one 

 group of these hypotheses the Chordonia evolved from the 

 larvae of the Oligomeria, thus by way of neoteny; the second 

 group of these interpretations derives the Chordonia from 

 the adult forms of the Oligomeria. It is by no means rare 

 to meet the former type of interpretation. It corresponds to 

 the widely accepted method of solving various phylogenetic 

 problems by means of larval forms. Personally, I am not 

 a priori opposed to use neoteny in various phylogenetic spe- 

 culations. I myself have used the phenomenon of neoteny 

 twice when I tried to explain the origin of new animal types. 

 First, in connection with the suggested derivation of the 

 Ctenophora from the planktonic larvae of the polyclad Tur- 

 bellaria, and secondly, in connection with the derivation or 

 the Chaetognatha from the planktonic larvae of the Brachio- 

 poda. I am also firmly convinced that in several other cases 

 new forms, which emerged during the phylogenetic processes, 

 evolved by way of a neotenization. This type of development 

 has to be taken into consideration in connection with the 

 evolution of the Larvacea or Appendiculata, among the Tuni- 

 cata, and with the Proteidae, among the Urodela, etc. 



Yet at the same time I think that we must not go too far 

 in this direction, and that we should use an explanation by 

 means of a neoteny in those cases where all the other types 

 of evolution appear as completely improbable. It has already 

 been mentioned how the numerous attempts that have been 

 made to interpret the origin of all possible groups by means 



