408 THE EVOLUTION OF THE METAZOA 



in a place where we would actually expect an anal orifice. 

 Something similar has also been observed in one species of 

 the Ameria, in Gordins (Svabenik, 1925). 



These differences are certainly conspicuous and need an 

 interpretation. First it should be stated that all our Ameria and 

 Polymeria are usually considered as Protostomia, and all our 

 Oligomeria and Chordoma as Deuterostomia. There is, how- 

 ever, an uncertainty among the adherents of the dichotomy 

 Protostomia : Deuterostomia (also if these taxons appear un- 

 der other names) on how they should classify the so-called 

 Tentaculata (a part of our Oligomeria). Hatschek and Grobben 

 placed them resolutely among the Protostomia (i. e. Ectero- 

 coelia, according to Hatschek); the same was done by 

 Hyman (as a part of the Schizocoela), Beklemischew (as Po- 

 daxonia w^hich, however, include also the Brachiopoda!), etc. 

 Frequently, the Tentaculata are also considered as an inter- 

 mediata or transitional group between the Protostomia and the 

 Deuterostomia (e. g. by Cori) because on the one hand they 

 have a definitive mouth which develops from the primitive 

 mouth (yet in the same place if the primitive mouth growls 

 together in due time), and on the other hand because their 

 perigastrocoele develops partly in the enterocoeUc way which 

 is quite an inconvenient fact for those who believe in the 

 dichotomy discussed here. 



After everything we have said about the evalution of the 

 ontogenetic facts and their exploitation in a natural system of 

 animals it becomes clear that we must proceed very carefully 

 when we wish to use these facts for some taxonomic purposes. 

 We must therefore assume not only a critical but also a negative 

 attitude towards a division of the Eumetazoa as the Coelomata 

 into the Protostomia and the Deuterostomia. We must take 

 this stand not only towards those attempts which seek to 

 represent the various types of oral and anal openings that can 

 be observed during the ontogenies as if they were recapitula- 

 tions of some adult states (cf. the desperate attempts made by 

 Boettger (1952) and Steiner (1956) who tried to explain these 



