146 DARWINISM AND HUMAN LIFE 



similar pure-bred organisms to other cases, we note, 

 as a frequent occurrence, that the offspring is a 

 combination of the paternal and maternal charac- 

 teristics in such a thoroughgoing way that the 

 result may be described as an intimate blend. In a 

 cross between the long-eared lop-rabbit and a short- 

 eared breed, Castle found that forms with ears of 

 intermediate length are produced, and that these 

 intermediates breed true. The colour of the skin 

 in mankind seems to blend when white and black 

 races are crossed. Many plant hybrids are precisely 

 intermediate between the two parents. 



(3) Particulate Inheritance. The offspring often 

 show what may be called a coarse-grained or 

 non-blended combination of the paternal and 

 maternal characteristics, the former appearing in 

 one part of the body, the latter in another part, as 

 when a light-coloured horse and a dark-coloured 

 mare have a piebald foal, or when a sheep-dog has 

 an eye like its father on one side and an eye like its 

 mother on the other side. This is often described 

 as particulate inheritance. 



(4) Exclusive Inheritance. It often happens 

 that the offspring takes wholly after one of its 

 parents, or wholly as regards particular organs, 

 and extreme forms of this are spoken of as exclusive 

 inheritance. The inheritance of eye-colour in 

 mankind belongs to this type. Although the 

 inheritance is dual, it seems as if only one set of 

 the heritable characters found expression at least 

 as regards particular organs. The more pure-bred 

 parent is the more likely to be prepotent in the 

 inheritance. This exclusive inheritance may be 

 the first step in a clear Mendelian case, which we 

 shall consider later. 



