CHAPTER II 



VARIATION 



WE have seen that the subjects of Heredity and 

 Variation are so closely connected that one cannot 

 be considered apart from the other, for without 

 variation all the offspring of the same parents would 

 be exactly alike, and the study of heredity would 

 resolve itself into an investigation of the cause of 

 this likeness. But the actual problem is much less 

 simple ; it includes the questions how and why the 

 members of a family may differ from one another, 

 and according to what rules and by what means 

 these differences are transmitted to later generations. 

 In practice therefore the study of heredity is the 

 study of the manner and cause of the inheritance of 

 variations, and hence the nature of variation must 

 be examined before enquiry into its transmission. 



Before the time of Darwin variations were fre- 

 quently regarded as abnormalities, inconvenient to 

 the systematist and of relatively small importance. 

 Every species was supposed to conform to the type 



