NEW INTERPRETATION OF CNIDARIA 281 



jugation— all the remaining Protozoa reproduce by means of 

 syngamy— have been considered as basically different from 

 other animals and that a derivation of Eumetazoa, where 

 syngamy regularly occurs, from Ciliata was looked upon as an 

 unacceptable principle. In various manuals and text books 

 conjugation is usually defined in the same way as it appears 

 in the book by Hyman (1:75). "... conjugation or temporary 

 contact of tw^o protozoans with nuclear change." Almost the 

 same words are used by Kudo (1946 : 154) in his Proto- 

 t(oologj, and by numerous other authors when they characterize 

 this phenomenon . The emphasis in this sentence is on the "nuclear 

 change." A Uttle later Hyman (I : 173) gives quite a rational 

 interpretation of this "nuclear change" when she writes, "The 

 micronuclei, which play the important role in conjugation all 

 divide twice, and these divisions probably correspond to the 

 maturation divisions of metazoan germ cells, involving a 

 reduction of chromosomes." Even better is the statement 

 made by Hall (1953 : 80) who writes, "Typical conjungation 

 involves the change of haploid pronuclei (gametic nuclei) 

 between two paired organisms, the formation of a syncaryon 

 in each, and then nuclear reorganization." 



I will now endeavour to show (Hadzi, 1950) of this con- 

 jugation, a true peculiarity of Ciliata, that its individual ele- 

 ments had been inherited by Eumetazoa via Turbellaria^ 

 Acoela. Conjugation does not represent an obstacle to such 

 a derivation, provided that we place the point of separation 

 of Ciliata and Turbellaria, and thus of Eumetazoa, farther back 

 to a time before the Ciliata have become specialized and 

 before they have evolved the conjugation which is now 

 typical of them. Numerous peculiarities of sexual conditions 

 that can be observed in the lowest Eumetazoa, in the Acoela, 

 can be better understood if viewed from our standpoint. 



There certainly was a time when, sexuality had not yet 

 been developed by the living organism— only the Protista 

 existed. This sexuality, however, had already appeared when, 

 the Protista still wielded an unHmited authority. Why and how 



