THE NEW GENEALOGICAL TREE 447 



criticized such interpretations, adding at the same time a very 

 proper observation that we must search for the origin of the 

 Chordonia much farther back in the geological past than in the 

 now extinct carpoidal Echinodermata and in the equally 

 extinct Ostracodermi, i.e. much earlier than in the Lower 

 Silurian. In my opinion the Echinodermata cannot be taken 

 into consideration as ancestors of the Chordonia either in 

 their larval forms or as adult animals. The Echinodermata 

 represent the largest and the most ramified branch that evolved 

 from the stem of the Oligomeria. Yet this branch ends blind- 

 ly, it did not lead to the evolution of a new subtype, and above 

 all it did not lead to the emergence of a new type : the Chordata. 



The Probable Origin of the Chordonia 



It is most probable that the Chordonia evolved as the most 

 recent and highest animal type from the Oligomeria. The 

 recent subtypes of the OUgomeria, however, in which we 

 can observe a greater or smaller degree of specialization 

 cannot be taken into consideration as possible ancestors of 

 the Chordonia ; they had in the meantime too long a geological 

 period at their disposal for their own evolution. It must 

 nevertheless be admitted that the Oligomeria which evolved 

 during this period in several directions, reached various levels 

 of organization, while at the same time the Chordonia also 

 went through a rich evolution which finally reached its climax 

 in the human species. There still exist some forms of the 

 Oligomeria which are similar to this early form. Animals 

 with radial symmetry which adopted the sessile way of life 

 became strongly simpUfied and their evolutions have ended 

 blindly, even in those cases when they secondarily readopted 

 free mobility, e.g. several groups of the Echinodermata 

 and several other groups of the Oligomeria. We find then 

 that there remain few slowly moving groups only, and even 

 among these we must exclude the tubicolous forms, especially 



