NATURAL SELECTION 127 



to these birds and insects in preserving them from dan- 

 ger. Grouse, if not destroyed at some period of their 

 lives, would increase in countless numbers; they are 

 known to suffer largely from birds of prey; and hawks 

 are guided by eyesight to their prey — so much so, that 

 on parts of the Continent persons are warned not to keep 

 white pigeons, as being the most liable to destruction. 

 Hence natuiral,.s,eJac±ion .. mighJL.^,he_effec^^ giving the 



proper color to each kind of grouse, and in keeping that 

 color, when once acquired, true and constant. Nor ought 

 we to think that the occasional destruction of an animal y 



of any particular color would produce little effect: we " ^ 

 should remember how esvsential it is in a flock of white O 

 sheep to destroy a lamb with the faintest trace of black. 

 We have seen how the color of the hogs, which feed on 

 the "paint-root" in Yirginia, determines whether they 

 shall live or die. In plants, the down on the fruit and 

 the color of the flesh are considered by botanists as char- 

 acters of the most trifling importance: yet we hear from 

 an excellent horticulturist, Downing, that in the United 

 States smooth-skinned fruits suffer far more from a bee- 

 tle, a Curculio, than those with down; that purple plums 

 suffer far more from a certain disease than yellow plums; 

 whereas another disease attacks yellow-fleshed peaches far 

 more than those with other colored flesh. If, with all 

 the aids of art, these slight differences make a great dif- 

 ference in cultivating the several varieties, assuredly, in 

 a state of nature, where the trees would have to struggle 

 with other trees and with a host of enemies, such differ- 

 ences would effectually settle which variety, whether a 

 smooth or downy, a yellow or purple fleshed fruit, 

 should succeed. 



