12 NATURAL INHERITANCE. [chap. 



illustration partly covers the analogous fact of diseases 

 and other inheritances skipping a generation, which by 

 the way I find to be by no means so usual an occurrence 

 as seems popularly to be imagined. 



Heritages that Blend and those that are Mutually 

 Exclusive. — As regards heritages that blend in the 

 offspring, let us take the case of human skin colour. 

 The children of the white and the negro are of a 

 blended tint ; they are neither wholly white nor 

 wholly black, neither are they piebald, but of a fairly 

 uniform mulatto brown. The quadroon child of the 

 mulatto and the white has a quarter tint ; some of 

 the children may be altogether darker or lighter than 

 the rest, but they are not piebald. Skin-colour is 

 therefore a good example of what I call blended in- 

 heritance. It need be none the less " particulate " 

 in its origin, but the result may be regarded as a fine 

 mosaic too minute for its elements to be distinguished 

 in a general view. 



Next as regards heritages that come altogether from 

 one progenitor to the exclusion of the rest. Eye-colour 

 is a fairly good illustration of this, the children of a 

 light- eyed and of a dark-eyed parent being much more 

 apt to take their eye-colours after the one or the other 

 than to have intermediate and blended tints. 



There are probably no heritages that perfectly blend 

 or that absolutely exclude one another, but all heritages 

 have a tendency in one or the other direction, and the 

 tendency is often a very strong one. This is paralleled 



