244 THE EVOLUTION OF THE METAZOA 



simplified. This has not only a scientific value but also a value 

 in teaching (Hadzi, 1952 a). We must discourage the use 

 of the group phylum Coelenterata (Leuckart 1848 after 

 A. S. Pearson) instead of Cnidaria, regardless of prioritv 

 which is anyhow not internationally binding in connection 

 with the names of the highest categories. I have already 

 emphasized that the notion, and thus also the category, 

 of Coelenterata— and correspondingly the opposite notion 

 of Coelomata— have now become completely superfluous 

 because they do not find support in the natural facts. They 

 must now take their place in the archives. If we have to dis- 

 miss the group Coelenterata then we must also necessarily 

 abandon the group which represents the opposite to Cnidaria 

 and which has been given the name of Acnidaria. These are in 

 reality Ctenophora that constitute a class of Ameria, which has 

 the same rank as Cnidaria because they had evolved from 

 Turbellaria parallel to, and independently from, Cnidaria. 



The Cnidaria, together with Turbellaria, Ctenophora, Trema- 

 toda and Cestoda seem to be somewhat more closely connected 

 because of one important common property, and that is that 

 they all are aproctous animals, i.e. their digestive tract does 

 not possess a primary anal orifice. In spite of this it is unneces- 

 sary to establish a special category which would include all of 

 them and to give it a special name. In practice the usual pair 

 Aprocta-Euprocta can be well enough used in comparative 

 morphology. 



It is unfortunate that, even recently, attempts have been 

 made to use for systematic purposes such an antiquated notion 

 as that of Radialia (or some similar ones) even if it appears 

 with a somewhat changed scope (e.g. without Echinodermata). 

 This attempt has been made, by Beklemischev (1958) who 

 classifies Ctenophora as Acnidaria among RadiaUa. In both 

 cases the radial symmetry, which is usually partial only, had 

 evolved, as has been already shown, secondarily from the 

 bilateral symmetry. Moreover, the structure of Ctenophora 

 is in realitv bisvmmetric and not radiallv symmetric. Parallel to 



