Chap. XII. 



INHERITANCE. 



27 



anomalies have been transmitted. But the power of transmission 

 is extremely variable: in a number of individuals descended 

 from the same parents, and treated in the same manner, some 

 display this power in a perfect manner, and in some it is 

 quite deficient ; and for this difference no reason can be assigned. 

 In some cases the effects of injuries or mutilations apparently 

 are inherited ; and we shall see in a future chapter that the 

 effects of the long-continued use and disuse of parts are cer- 

 tainly inherited. Even those characters which are considered 

 the most fluctuating, such as colour, are with rare exceptions 

 transmitted much more forcibly than is generally supposed. The 

 wonder, indeed, in all cases is not that any character should 

 be transmitted, but that the power of inheritance should ever 

 fail. The checks to inheritance, as far as we know them, are, 

 firstly, circumstances hostile to the particular character in ques- 

 tion ; secondly, conditions of life incessantly inducing fresh 

 variability ; and lastly, the crossing of distinct varieties during 

 some previous generation, together with reversion or atavism— 

 that is, the tendency in the child to resemble its grand-parents 

 or more remote ancestors instead of its immediate parents. 

 This latter subject will be fully discussed in the following 

 chapter. 



