422 THE EVOLUTION OF THE METAZOA 



and the Deuterostomia (also when treated under other names 

 which we have already mentioned) I wish only to point here 

 to the suggestion made by palaeozoologist Miiller (1958). 

 Here we can find a combination of the scheme as it was pro- 

 posed by Cuenot— which Miiller obviously considers as the 

 best among the now available schemes— and of my diagram. 

 The uncertainty Miiller feels regarding the point where the left 

 branch (the Deuterostomia) should begin, according to the 

 interpretation proposed by Cuenot and by a number of other 

 zoologists, is characteristic. A small operation only is needed 

 here to reach a well-founded conclusion. The left branch which 

 is hanging loose in the scheme proposed by Miiller can be 

 extended so much that it reaches the right branch at a point 

 above that spot where the Mollusca branch off, and below the 

 point where the Annelida branch off. In this way the two main 

 branches are changed into a stem, and the Annelida-Arthro- 

 poda are represented as one of the main branches. It is true 

 that in this way we expose ourselves to the accusation that we 

 try to revive the old, long obliterated idea of an 'Techelle 

 animale^' or even of a general stage-like sequence, I consider 

 such an accusation as unjust because in my attempt there is 

 neither a simple gradation, nor only one uniformly progressive 

 line of evolution. My construction represents a true genealo- 

 gical tree, and not a ladder, with the only difference that this 

 tree has a real trunk (as this is normal in all the trees) and only 

 one main top. The new element which can be found in my 

 attempt, however, is the fact that in my interpretation of 

 natural facts I have come to the conclusion that there has 

 been a long era of a retrogressive evolution. I have ende- 

 avoured to make this suggestion as feasible as possible. 



During the transition from the phylum Ameria to the phylum 

 Polymeria, as well as from the phylum Oligomeria to the phy- 

 lum Chordoma, evolution always began at a somewhat lower 

 level of the earlier type, yet it immediately continued in a 

 progressive direction. This evolution led to the emergence 

 of a new type whose organization reached another higher 



