330 Genetics of a Daphnia Hybrid during Parthenogenesis 



Summary. 



A hybrid clone, derived from the cross Daphnia obtusa x D. pulex 

 was bred for ten generations. Throughout this period the hybrid clone 

 was characterized by excessive production of males and sexual eggs, 

 complete sterility of the males, partial sterility of the parthenogenetic 

 eggs, and probably normal fertility of the sexual eggs. 



The ten -parthenogenetic generations of this clone furnished no evi- 

 dence of the occurrence of segregation. 



This experiment is complementary to my former experiments on in- 

 heritance in parthenogenesis in the Cladoceran Siniocephalus, and indicate 

 that during the parthenogenetic reproduction of these forms, which is 

 not accompanied by reduction of chromosomes, Mendelian segregation 

 does not take place, nor does genetic diversity between parent and off- 

 spring normally arise. 



REFERENCES TO LITERATURE. 



Agar, W. E. Phil. Trans. Roy. Soc. London^ Series B, Vol. com. 1913. 



Phil. Trans. Roy. Soc. London, Series B, Vol. ccv. 1914. 



Chambers, R. Biological Bulletin, Vol. xxv. 1913. 

 Detlefsen, J. A. Carnegie Institute Publication, No. 205, 1914. 

 Fryer, J. C. F. Journal of Genetics, Vol. ni. 1913. 

 Kdhn, a. Arehiv fur Zellforschung, Vol. i. 1908. 

 Nabours, R. K. Journal of Oenetics, Vol. vii. 1917- 

 Taylor, M. Zoologischer Anzeiger, Vol. xlv. 1915. 



