FURTHER OBSERVATIONS ON ARTIFICIAL PARTHEN- 

 OGENESIS IN FROGS 



JACQUES LOEB and F. W. BANCROFT 



The Rockefeller Institute for Medical Research, New York 



1. We have repeated our efforts to raise parthenogenetic frogs 

 during the past season in order to be able to determine their sex, 

 but with less success than we had last year. None of the parthen- 

 ogenetic tadpoles which we produced this year lived as long 

 as those of the previous year. 



During the past two seasons we have punctured the eggs of 

 Rana sphenocephala, R. pipiens, R. silvatica, Chorophilus feri- 

 arum and of Bufo amerieanus. Only the eggs of the first two 

 species could be utilized for our purpose, inasmuch as it is possible 

 in them alone to obtain swimming parthenogenetic tadpoles from 

 the punctured eggs. If the eggs of the other species mentioned 

 are punctured they may begin to segment but they do not reach 

 the tadpole stage. The frogs were caught in the open while 

 copulating, the sexes separated and sent immediately to the 

 laboratory. Some of the frogs (R. pipiens) were obtained in Long 

 Island and some were sent from Chicago. The' results were in 

 both cases the same, in spite of the fact that the eggs of the frogs 

 sent from Chicago must have remained in the uterus several days. 

 From 600 to 1000 eggs of each female were punctured". The 

 results were similar to those described in our last paper, ^ except 

 that this spring all the swimming parthenogenetic tadpoles died 

 when they were from twenty to thirty days old. Some of the 

 eggs were smeared with blood before they were punctured. While 



•Jour. Exp. Zool., vol. 14, p. 275. 



379 



