PREVIOUS INTERPRETATIONS OF CNIDARIA 145 



The Genital System 



Of all the differences that exist between the Turbellaria and 

 Cnidaria the differences that can be found between their genital 

 systems seem to be the greatest. As a matter of fact these diffe- 

 rences at the first glance seem to be so great that any attempt 

 to derive the Cnidaria from the Turbellaria appears as a comp- 

 letely hopeless venture. Yet if we study the conditions 

 that can be found in these two groups, and if we compare 

 them with those that can be found in other more closely 

 related groups of Ameria, we find the situation changed 

 so that it does not seem that such a deduction is hopeless. 

 It is certain that the Turbellaria, whose organisation shows 

 in all other respects a lower stage of development, possess 

 at the same time a genital system which has a complex 

 structure and such a variety of forms, that cannot be surpassed 

 by any other animal group, and we do not exclude even 

 the most highly developed Vertebrata. As is well known, 

 the Turbellaria are, with a few exceptions hermaphrodites. 

 I will return later to discuss the probable origin of this 

 hermaphroditism. Without any intention to go into details 

 that are well known to zoologists (frequently the Turbel- 

 laria are systematically grouped and identified on the basis 

 of their complicated genital systems), I wish only to mention 

 here that these complexities affect both the gonads themselves 

 (e.g. the division of female gonads into an germarium and a 

 vitellarium),as well as their gonoducts, various auxiliary glands, 

 and, finally, the organs of copulation. Due to their mobility 

 these animals not only search for their food but also seek out 

 their sexual partners. The advantage of the hermaphroditic 

 state consists in the fact that any meeting with a member of 

 the same species makes possible copulation and thus also 

 reproduction. 



It has been too little considered that though a herma- 

 phroditic genital apparatus with a complicated structure 

 can be found in a large majority of Turbellaria, there are 



