154 H.H. Newman 



The material from Experiment 2 showed the average condition 

 of the pure-bred eggs to be 5.26 + ; that of the hybrid, ^.39 + . 



The material from Experiment 4 showed the average condition 

 of the pure-bred eggs to be 4.72 + that of the hybrid 4.76 + . The 

 difference here is very slight, but in the same direction as in the 

 other cases. No doubt another random selection of eggs from the 

 material used in Experiment 4 would have shown a more marked 

 difference than that just recorded. 



Summary of Experimental Data and Conclusions 



The tabular summary, Table VII, of the first four experiments 

 will enable the reader to see at a glance that, no matter what 

 method of comparison is used, there is a developmental balance 

 in favor of the hybrid strain. 



The last two experiments, somewhat more searching in char- 

 acter, show that the hybrid strains develop more rapidlv than 

 the pure bred. 



In all cases the accelleration in developmental rhythm must 

 be due the introduction of the spermatozoon of the more rapidly 

 developing species. 



In Experiment 6 it is clear, in addition, that the form of cleavage 

 was affected by the foreign spermatozoon, in that there was a 

 strong tendency toward irregularity in cleavage even in the early 

 stages described. 



We conclude that the male germ cell begins to exercise its hered- 

 itary function at a far earlier period than is commonly supposed. 



II THE ROLE OF THE SPERMATOZOON IN EARLY DEVELOPMENT 



The question of the precise role of the male cell in early develop- 

 ment has received much attention ot late. It has come to be recog- 

 nized that the spermatozoon has two separate functions, that of 

 initiating development and that of imparting to the offspring the 

 characters of the male parent. There seems to be a strong tend- 

 ency today to regard the hereditary function as one that operates 

 only after a period of abeyance, during which the hereditary char- 

 acters of the young embryo are determined solely by the structure 



