150 



H. H. New? nan 



Method III. Comparison of strict 4's, strict 2's and interme- 

 diates. 



In the pure-bred lot there are 21.42+ per cent of strict 4's, 

 18.40 + per cent of strict 2's and 60.17 + per cent of intermediates; 

 in the hybrid lot 34.53 + per cent of strict 4's, 9.16 + per cent of 

 strict 2's and 56.14 + per cent of intermediates. 



Development has been allowed to proceed too far to show many 

 stages below the 2-cell condition. The hybrid strain shows two 

 eggs in the 2-minus condition and thus exhibits a wider range of 

 variability even at so early a period as this. 



Experiment ^ 

 Eggs of several females divided and fertilized with the milt of 

 three selected males of each species. Killed three hours and fifty 

 minutes after fertilization. 



TABLE IV 



On account of comparatively low temperature cleavage pro- 

 ceeded somewhat more slowly in this than in preceding experi- 

 ments; hence the much smaller proportion ot the more advanced 

 stages. 



There were 253 uncleaved eggs in the pure-bred lot and 236 in 

 the hybrid lot. 



Method I. Comparison of the average number of blastomeres. 

 The average in the pure-bred lot is 2.46 + ; that in the hvbrid lot 

 2.58+. 



