390 THE EVOLUTION OF THE METAZOA 



as regards coelom conditions from the Acoelomata. It is 

 even more erroneous to consider "the phylum Tardigrada" 

 as a member of the Pseudocoelomata. In connection with 

 this we could speak at the most of a myxocoele because 

 in their ontogenies we can observe pairs of coeloms that are 

 distributed metamerically like the enterocoeloms. The Tard- 

 igrada must therefore not be placed anywhere near the 

 Aschelminthes. They certainly stand closer to the primitive 

 Arthropoda.. 



The suggestion which was made by Colosi (1956:505) 

 should be mentioned here as an example of an extremely one- 

 sided systematization based on the conditions that can be 

 observed in the coelom cavities. Among the taxons which 

 are given various ranks we can find, in Colosi's suggestion, 

 the Deuterocoelomata (including Mollusca, MoUuscoida, 

 Annelida, and Onychophora); instead of their counterpart the 

 Protocoelomata or the Acoelomata we find the group ("stip- 

 ite") Protonephridia which includes all the Ameria. A part 

 of these (these are actually the Aschelminthes) can be found 

 under the name Pseudocoelomata. All this refers to the Proto- 

 stomia. The Deuterostomia are divided into the Archicoelo- 

 mata (they include the Chaetognatha only!), and the Meta- 

 coelomata (the Hydrocoelomata and the Chordata). The 

 Syncoelomata consist of the Tardigrada and the Arthropoda. 

 The name Parenchymatosa appears twice ; once it includes 

 the Nemertinea and the Endoprocta, and another time the 

 Gordiacea. I can hardly believe that any zoologist will 

 ever accept such a classification, it is a purely personal 

 affair. 



There is according to my interpretation a basic diflFerence 

 betw^een the various coeloms s.l. and the actual coelom s. str,, 

 the perigastrocoele. The coeloms s.l. can be found in wddely 

 different groups of the Eumetazoa and it seems that they had 

 evolved polyphyletically. They cannot be used as a sound basis 

 of a high taxonomy, except in a negative sense, i.e. that all 

 the Eumetazoa which do not possess primarily a perigastro- 



