NEW INTERPRETATION OF CNIDARIA 28S 



rated, is that it makes possible for us to understand the herm- 

 aphroditism not only of the Platyhelminthes, as the lowest 

 Eumetazoa, but also of the numerous groups of Ameria 

 (especially of the Mollusca), and of other larger or smaller 

 groups which have reached a higher level of evolution. It can 

 be stated quite generally that almost everywhere among the 

 Eumetazoa an active inclination towards hermaphroditism 

 can be observed. 



Even if among the recent Protozoa no transitional forms 

 can be found from the polymastigous and polykaryonic Zoo- 

 flagellata and the lower Euciliata, there can still be no doubt 

 that the Infusoria had evolved from just such Flagellata. The 

 circumstances have been the reason that the endoparasitic 

 poly- and hyper-mastigous species of Flagellata, which are 

 partly equipped with the polymerized nuclei, have only been 

 preserved till now, or that such species only have become 

 known. They are certainly strongly speciaHzed, and thus 

 greatly modified. The Opalinidae have been considered,, 

 wrongly, to be transitional forms; they were therefore placed 

 under the name "Protociliata" at the root of the Ciliata. The 

 Opalinidae are in reality strongly modified Zooflagellata and 

 they lead, moreover, an endoparasitic way of life. In spite of 

 this we find the Opalinidae to be very interesting here; 

 first, because they include species that are mutually closely re- 

 lated which contain two, it seems equivalent, nuclei only; the 

 completely round body is covered with cilia; and, secondly, be- 

 cause some of their species contain an increasing number of nuc- 

 lei, yet their sexual phase is in spite of all this only slightly atypi- 

 cal (Wessenberg, 1961)*. They form freely moving and externally 

 slightly differentiated (in their size) gametes which belong to 

 both sexes and which move by means of cilia. It is certain that 

 the syngamy takes place in the Opalinidae. Unfortunately, 



* Wessenberg who has recently (1961) made a study of the Opalinidae 

 proposes a special taxon for this group under the name Opalinata which, 

 should be placed between Flagellata ("flagellated Protozoa") and Ciliata 

 ("ciliated Protozoa"). 



