2 VARIATION 



variation (Miiller's twins) 1 seems inevitable effect 

 of process of reproduction. But more important 

 is that simple (?) generation, especially under new 

 conditions [when no crossing] (causes) infinite varia- 

 tion and not direct effect of external conditions, 

 but only in as much as it affects the reproductive 

 functions 2 . There seems to be no part (beau ideal 

 of liver) 3 of body, internal or external, or mind or 

 habits, or instincts which does not vary in some 

 small degree and [often] some (?) to a great amount. 

 [All such] variations [being congenital] or those 

 very slowly acquired of all kinds [decidedly evince 

 a tendency to become hereditary], when not so 

 become simple variety, when it does a race. Each 4 

 parent transmits its peculiarities, therefore if varieties 

 allowed freely to cross, except by the chance of two 

 characterized by same peculiarity happening to 

 marry, such varieties will be constantly demolished 5 . 

 All bisexual animals must cross, hermaphrodite 

 plants do cross, it seems very possible that her- 



1 Cf. Origin, Ed. i. p. 10, vi. p. 9, "Young of the same litter, sometimes 

 differ considerably from each other, though both the young and the parents, 

 as Miiller has remarked, have apparently been exposed to exactly the same 

 conditions of life." 



2 This is paralleled by the conclusion in the Origin, Ed. i. p. 8, that "the 

 most frequent cause of variability may be attributed to the male and 

 female reproductive elements having been affected prior to the act of 

 conception." 



3 The meaning seems to be that there must be some variability in the 

 liver otherwise anatomists would not speak of the ' beau ideal ' of that 

 organ. 



4 The position of the following passage is uncertain. " If individuals 

 of two widely different varieties be allowed to cross, a third race 

 will be formed a most fertile source of the variation in domesticated 

 animals. (In the Origin, Ed. i. p. 20 the author says that " the possibility 

 of making distinct races by crossing has been greatly exaggerated.") If 

 freely allowed, the characters of pure parents will be lost, number of 

 races thus (illegible) but differences (?) besides the (illegible). But if 

 varieties differing in very slight respects be allowed to cross, such small 

 variation mil be destroyed, at least to our senses, a variation [clearly] 

 just to be distinguished by long legs will have offspring not to be so 

 distinguished. Free crossing great agent in producing uniformity in any 

 breed. Introduce tendency to revert to parent form." 



5 The swamping effect of intercrossing is referred to in the Origin, 

 Ed. i. p. 103., vi. p. 126. 



