152 



H . H. Newman 



stages 4 and 5 is classed as 4^. The average condition can then be 

 readily obtained by assigning to each egg a value corresponding 

 to the figured group to which it belongs and dividing the total 

 of these values by the total number ot eggs. The result should 

 give a very accurate numerical statement of the relative rate of 

 cleavage in the two strains. The accompanying figures and table 

 give in abbreviated form the results of the experiment. 



The average stage of the pure-bred lot is 5. 11 +; that of the 

 hybrid lot, 5.57 4-, a difference of nearly half a stage. 



Another method of dealing with these data is to compare the 

 percentage of eggs assigned to the lower half and the upper halt of 

 the table, allowing the dividing line to fall below stage 5. 



This shows a predominance of the more advanced stages to be 

 more marked in the hybrid than in the pure-bred strain. 



The mode in both cases is stage 6, but there is greater skewness 

 of curve toward the 7 end of the curve in the hybrid than in the 

 pure-bred array. 



Another point worthy of note is that there is a much larger per- 

 centage of irregular cleavages in the hybrid lot than in the pure- 

 bred. This in itself might be used as evidence of the very early 

 formative influence of the spermatozoon. 



The proportion of 3-cell stages is very nearly equal in the two 



