HEREDITY 



CHAPTER I 



INTRODUCTORY 



Heredity is a general term which expresses the fact 

 that the individuals of all animal and veo^etable 

 species tend to beget f heir like ; " as is very natural," 

 we feel inclined to add. This comment expresses, in 

 popular language, the conviction that heredity is a 

 "law of Nature," that it results from the action of 

 constant causes which may be capable of analysis. 

 We expect to find the child like his father, partly 

 because we have frequent experience of this like- 

 ness ; but we also feel that, had we had no experi- 

 ence of it, we would have predicted its occurrence. 

 It "stands to reason" that a child must resemble his 

 father in greater or less degree; and it will be our 

 business in the following pages to inquire into the 

 manner of a sequence so reasonable. 



But, on the other hand, the child, when he grows 

 up, is not found to be his father's "double." In 

 some measure, however slight, he differs. This dif- 

 ference might be attributed, in all cases of sexual 

 reproduction, to the fact that the child is his 

 mother's child as well as his father's. But even 



