Darwin-Wallace Celebration. 95 



perfect adaptation, must generally gain the victory in their 

 contests. This kind of selection, however, is less rigorous 

 than the other ; it does not require the death of the less 

 successful, but gives to them fewer descendants. The struggle 

 falls, moreover, at a time of year when food is generally 

 abundant, and perhaps the effect chiefly produced would be 

 the modification of the secondary sexual characters, which are 

 not related to the power of obtaining food, or to defence from 

 enemies, but to fighting with or rivalling other males. The 

 result of this struggle amongst the males may be compared 

 in some respects to that produced by those agriculturists who 

 pay less attention to the careful selection of all their young- 

 animals, and more to the occasional use of a choice mate. 



II. Abstract of a Letter from C. DARWIN, Esq., to Prof. ASA. 

 GRAY, Boston, U.S., dated Down, September 5th, 1857. 



1. It is wonderful what the principle of selection by man, 

 that is the picking out of individuals with any desired quality, 

 and breeding from them, and again picking out, can do- 

 Even breeders have been astounded at their own results. 

 They can act on differences inappreciable to an uneducated 

 eye. Selection has been methodically followed in Europe for 

 only the last half century ; but it was occasionally, and even 

 in some degree methodically, followed in the most ancient 

 times. There must have been also a kind of unconscious 

 selection from a remote period, namely in the preservation of 

 the individual animals (without any thought of their offspring) 

 most useful to each race of man in his particular circum- 

 stances. The " roguing," as nurserymen call the destroying 

 of varieties which depart from their type, is a kind of 

 selection. I am convinced that intentional and occasional 

 selection has been the main agent in the production of our 

 domestic races ; but however this may be, its great power of 

 modification has been indisputably shown in later times- 

 Selection acts only by the accumulation of slight or greater 

 variations, caused by external conditions, or by the mere fact 

 that in generation the child is not absolutely similar to its 

 parent. Man, by this power of accumulating variations, 

 adapts living beings to his wants may be said to make th 

 wool of one sheep good for carpets, of another for cloth, &c. 



