ON ARTIFICIAL PARTHENOGENESIS IN FROGS 381 



According to Kuschakewitsch these intermediates may develop 

 into either males or females, and there are indications in the 

 sections of the parthenogenetic frog that this transformation may 

 have been under way. In the anterior part of the left gonad of 

 the parthenogenetic frog the sections show all the appearances 

 which Kuschakewitsch _ (p. 145) considers characteristic for the 

 early stages of the transformation of the intermediate form into 

 males. The endothelial lining of the secondary genital spaces is 

 thicker than usual, more convoluted, and mitotic figures may be 

 seen in places. In some regions considerable masses of undifferen- 

 tiated embryonic tissue have been formed which are continuous 

 with the endothelium of the secondary genital spaces and occupy 

 almost the whole cross section of the gonad except for a few patches 

 of germinative endothelium. If we may rely upon the statements 

 of Kuschakewitsch, our frog would have developed into a male 

 if it had survived. 



The gonads of the parthenogenetic tadpole were so poorly fixed 

 that nothing could be made out about them except that they 

 contained many more large oocytes than those of the frog. It, 

 could not be determined whether this individual was a female or 

 belonged to the intermediate form. 



The frog which had originated from a fertilized egg of the same 

 female from which the parthenogenetic tadpole and frog were 

 obtained, was killed ^bout four months after metamorphosis. It 

 had grown rapidly. The gonads were evidently those of a male. 

 The spermatic follicles contained cells in all stages of spermato- 

 genesis from spermatogonia to spermatids with greatly elongated 

 nuclei. In addition almost every section showed follicles which 

 were nearly filled with a large oocyte in the early growth period. 

 Thus it appears that this male may ha\'e developed from a her- 

 maphrodite or intermediate, if Kuschakewitsch 's statements are 

 correct. 



In the European species, R. esculenta, the formation of sperma- 

 tozoa does not take place for several years after metamorphosis 

 while in the control frog this process was well under way about four 



