Artificial Parthenogenesis 125 



the frog. The writer has tried it in vain on the eggs 

 of many other forms. He has at present seven par- 

 thenogenetic frogs over a year old, produced by merely 

 puncturing the eggs with a fine needle (Fig. 6). 

 These frogs have reached over half the size of the adult 

 frog. They can in no way be distinguished from the 

 frogs produced by fertilization with a spermatozoon. 

 This makes the proof conclusive that the methods of 

 artificial parthenogenesis can result in the production 

 of normal organisms which can reach the adult stage. 



Bancroft and the writer tried to determine the sex 

 of a parthenogenetic tadpole and of a frog just carried 

 through metamorphosis. Since in early life the sex 

 glands of both sexes in the frog contain eggs it is not 

 quite easy to determine the sex, except that in the male 

 the eggs gradually disappear and from this and other 

 criteria we came to the conclusion that both partheno- 

 genetic specimens, which were four months old, were 

 males. 



The writer has recently examined the gonads of a 

 ten months old parthenogenetic frog. Here no doubt 

 concerning the sex was possible since the gonads were 

 well-developed testicles containing a large number of 

 spermatozoa of normal appearance,and no eggs. ' (Figs. 

 7 and 8.) This would indicate that the frog belongs to 

 those animals in which the male is heterozygous for sex. 



« Since this was written, two more of the parthenogenetic frogs over 

 a year old died. Both were males. 



