NATURAL SELECTION CRITICISED. 271 



conditions are elements " in causing mere variability ; " 

 but (p. 122) he equates with external conditions as such 

 cause " the mere fact that in generation the child is not 

 absolutely similar to its parent." He doubts (iii. 158) 

 whether species are much more variable at one period 

 than another, " except through the agency of changed 

 conditions." His latest statement, however (July 19, 

 1881), is somewhat slack even as to this efficacy of 

 external conditions : " I still must believe that changed 

 conditions give the impulse to variability, but that they 

 act in most cases in a very indirect manner." 



"We have quite similar expressions when it is the term 

 variation that is used. A variation is to him even the 

 most slight and trifling difference. It is by " slight 

 differences selected " that a race or species is at last 

 formed (p. 87): "I believe most beings vary at all 

 times enough for selection to act on" (p. 123); Lowell 

 " overlooks the importance of the accumulation of mere 

 individual differences" (p. 319); "selection regulates, in 

 a state of nature, most trifling differences" (p. 320); 

 " very slight differences are continually found to be 

 important" (iii. 161); "the more I work, the more I 

 feel convinced that it is by the accumulation of such 

 extremely slight variations that new species arise" 

 (p. 33). The special slight variation he is speaking of 

 here is that of " a bird born with a beak jon^h of an j 

 inch longer than usual." Similar instances also men- ) 

 tioned are (ii. 339) "seals beginning to feed on the / 

 shore ;" bats (p. 336) " taking to feed on the ground, or / 

 anyhow, and anywhere, except in the air ; " (p. 3 1 8) " a ) 

 British insect feeding on an exotic plant ; " variation of j 

 " direction " in the tusks of an elephant ; (Origin, p. 141) j 

 "the black bear swimming, with widely open mouth, / 

 catching insects in the water." Mr. Darwin admits / 

 (iL 336), " I know of no fact allowing any the least 



