376 1HE GROWTH OF THE 'ORIGIN OF SPECIES.' 



to the influence of external conditions in producing variation, 

 and to the inheritance of acquired habits than in the 

 ' Origin.' " 



It is extremely interesting to find in the Sketch the first 

 mention of principles familiar to us in the * Origin of Species/ 

 Foremost among these may be mentioned the principle of 

 Sexual Selection, which is clearly enunciated. The important 

 form of selection known as " unconscious," is also given. Here 

 also occurs a statement of the law that peculiarities tend to 

 appear in the offspring at an age corresponding to that at 

 which they occurred in the parent. 



Professor Newton, who was so kind as to look through 

 the 1844 Sketch, tells me that my father's remarks on the 

 migration of birds, incidentally given in more than one 

 passage, show that he had anticipated the views of some later 

 writers. 



With regard to the general style of the Sketch, it is not to 

 be expected that it should have all the characteristics of the 

 ' Origin,' and we do not, in fact, find that balance and con- 

 trol, that concentration and grasp, which are so striking in 

 the work of 1859. 



In the Autobiography (p. 68, vol. i) my father has stated 

 what seemed to him the chief flaw of the 1844 Sketch ; he 

 had overlooked " one problem of great importance/' the 

 problem of the divergence of character. This point is dis- 

 cussed in the * Origin of Species,' but, as it may not be familiar 

 to all readers, I will give a short account of the difficulty and 

 its solution. The author begins by stating that varieties 

 differ from each other less than species, and then goes on : 

 " Nevertheless, according to my view, varieties are species in 

 process of formation How then does the lesser dif- 

 ference between varieties become augmented into the greater 

 difference between species ? " * He shows how an analogous 

 divergence takes place under domestication where an origin- 

 ally uniform stock of horses has been split up into race-horses, 



* 'Origin,' ist edit. p. in. 



