Heredity lu FituJiihis Hybrids 



149 



in the hybrid lot, 50.83 + per cent of strict 4's, 11.49+ per cent of 

 strict 2's and ^4.19 + per cent of intermediates. 



The percentage of 3-cell and of 2-minLis conditions is somewhat 

 smaller in the hybrid than in the pure-bred strain. 



There were 442 uncleaved eggs in the pure-bred lot and 222 in 

 the hybrid lot. It often happens that there is a larger percentage 

 of heterogenic than of homogenic fertilizations. At present the 

 factors governing this condition are not sufficiently understood 

 to warrant a discussion. 



Experiment j 



Eggs of a considerable number of females and milt of two choice 

 males of each species used. Killed four hours and forty minutes 

 after fertilization. 



TABLE III 



There were 397 uncleaved eggs in the pure-bred lot and 146 in 

 the hybrid lot. 



Method I. Comparison of the average number of blastomeres. 

 The average in the pure-bred lot is 3.19 + ; that in the hybrid lot 



3-44 + • 



Method II. Comparison of all 4's and all 2's. In the pure- 

 bred lot there are 65.08 + per cent of 4's and 29.15 + per cent of 

 2's; in the hybrid lot 78.77 + per cent of 4's and 15. 1 1 + per cent 

 of 2's. The percentage of 3-cell stages is about equal in the two 

 strams. 



THE JOURNAL OF EXPERIMENTAL ZOOLOGY. VOL. 8, NO. 2. 



