132 BLASTOGENIC VARIATIONS. 



of medium children, and a very small number of short 

 children; medium parents have many medium children, 

 and moderate numbers of tall and short children; short 

 parents have many short children, a moderate number 

 of medium children, and a very small number of tall 

 children. 



As was first pointed out by Mr. Galton,* characters 

 such as stature and eye-colour offer a distinct contrast 

 in their hereditary behaviour, for whilst " Parents of 

 different statures usually transmit a blended heritage 

 to their children, parents of different Eye-colours 

 usually transmit an alternative heritage. . . If one 

 parent has a light Eye-colour and the other a dark Eye- 

 colour, some of the children will, as a rule, be light and 

 the rest dark: they will seldom be medium eye-col- 

 oured." Thus eye-colour is a case of more or less ex- 

 clusive inheritance, or inheritance by the offspring of 

 the whole of the character of one parent and none of 

 that of the other. Obviously, therefore, for such in- 

 heritance the law of ancestral heredity does not at first 

 sight appear to hold. Supposing the offspring are 

 equally likely to take after one parent or the other, 

 then the coefficient of regression between parent and 

 offspring will be .5, instead of .3, as in the case of 

 blended inheritance : between grandparent and offspring 

 it will be .25, instead of .15, and so on. Nevertheless 

 it is probable that the law of ancestral heredity is just 

 as true for one form of inheritance as for the other, 

 only from the mere fact of the inheritance being ex- 

 clusive, it does not reveal itself in the same way. Sup- 

 posing there is no alternative between, for instance, 

 * " Natural Inheritance," p. 139. 



