452 H. H. NEWMAN 



species, F. majalis; the depth of pigmentation of young F. heter- 

 ocHtus egg hybrids as pronounced or more so than the darker 

 species, F. heterochtus. These cases in which the hybrids seemed 

 to show an exaggeration of dominance exemphfy the phenome- 

 non of 'hyperdominance.' In view of the fact that at the time 

 when this paper was written the new MendeHsm was sweeping 

 all before it, I took pains to emphasize especially all types of 

 inheritance which appeared to me to be essentially non-Mende- 

 lian. This stand was taken advisedly in the hope of checking 

 the growing impression that all inheritance was on analysis 

 Mendelian, and that cases of apparent blending, even in the Fi 

 generation of hybrids, was the result of incomplete analysis of 

 the factors involved. 



Chief stress was laid upon the importance of studying heredity 

 as a process, of observing the genesis of characters rather than 

 limiting observation to the definitive conditions as they appear 

 in adults. In this connection it was noted that maternal and 

 paternal influences showed alternating periods of predominance, 

 so that a character might appear as a dominant at one time 

 only to be superseded by the character that had apparently been 

 recessive. The definitive condition represents only the end re- 

 sult of a struggle between opposed parental tendencies whose 

 ups and downs may be observed from day to day in developing 

 hybrid embryos. 



The question as to whether the foreign sperm exercises any 

 influence upon the rate and character of early cleavage was in 

 this paper answered in the negative for the reason that in all 

 early experiments the differences were very small and not always 

 in the same direction. 



This paper was followed nearly two years later by another 

 dealing with the same species of fish (Newman '10), in which the 

 question as to the influence of the spermatozoon on early devel- 

 opment was reexamined. Very searching statistical methods 

 were applied to the relative rates of early cleavage in pure and 

 hybrid F. majalis eggs. It was found as the result of five experi- 

 ments involving very large numbers of eggs, that there was a 

 slight but constant acceleration of cleavage as the result of the 



