HEREDITY 475 



cases. They differ only in the fact that with the female the 

 development is easily brought about, while in the male it is 

 difficult and in most cases impossible. 1 



Belated inheritance. It is well known that all characters do 

 not develop contemporaneously. Thus the sexual characters 

 become developed just before full stature is attained, and with 

 the failure of the primary sexual characters with advancing age 

 comes the development of many of the peculiarities of the other 

 sex. Then it is that the hen crows, the human female grows 

 more hair, and the voice of the male becomes effeminate. The 

 term " belated inheritance," though fixed in our literature, is 

 unfortunate. It is belated development that is meant. Inheritance 

 comes only at, or rather before, birth ; but development is con- 

 ditioned upon many factors, among which age and sex are 

 important, but not the principal, considerations. 



Blended and exclusive inheritance. Perhaps the first and 

 most noticeable fact is that some characters blend when brought 

 together by transmission, while others remain distinct, being 

 apparently, mutually exclusive. Thus skin color in man blends 

 readily, the cross between white and negro being nearly always 

 of some shade intermediate between those of the parents, 

 almost never spotted. 2 In Shorthorn cattle and in Jerseys the 

 colors frequently, if not generally, blend, while in the Holstein- 

 Friesian they always remain distinct. In horses the blend is 

 common, but in hogs it is practically unknown, so that in a 

 litter of pigs from a black and a white parent the colors will 

 remain distinct ; some may be black, some white, and others 

 spotted, but none will be roans or grays. 



The same distinction holds as to characters generally. Some- 

 times the offspring will be intermediate between the parents, 

 showing a blend ; and again it will resemble one or the other, 

 or else exhibit traces of both, each distinct and separate. 



For example, so far as the matter has been studied, the blend 

 is most perfect as to stature, 3 and probably as to size in general, 

 but eye color does not readily blend, 4 nor do "tempers" 5 or 



1 The student is reminded that milk secretion among males is not unknown. 



8 The spotted skin is not absolutely unknown among humans, however. 



3 Gallon, Natural Inheritance, p. 89. * Ibid. p. 145. 5 Ibid. p. 233. 



