88 NATUKAL SELECTION. Chap. IV. 



whole geological periods ! Can we wonder, then, that Nature's 

 productions should be far " truer " in character than man's pro- 

 ductions ; tliat they should be infinitely better adapted to the 

 most complex conditions of life, and should plainly bear the 

 stamp of far higher workmanship? 



It may metaphorically l)e said that natural selection ig daily 

 and hourly scrutinizing, throughout the world, the slightest vari- 

 ations ; rejecting those that are bad, preserving and adding up 

 all that are good ; silently and insensibly working, whenever 

 and wherever opportunity oft'ers, at the improvement of each 

 organic being in relation to its organic and inorganic conditions 

 of life. We see nothing of these slow changes in progress, 

 until the hand of time has marked tlie lapse of ages, and then 

 so imperfect is our view into long-past geological ages, that 

 we see only that the forms of life are now different from what 

 they formerly were. 



In order that any great amount of modification in any part 

 should be eflectcd, a variety when once formed must again, 

 perliaps after a long interval of time, vary or present individ- 

 ual difl"erences of the same favorable nature, and these must be 

 again preserved, and so onward step by step. Seeing that 

 individual differences of all kinds perpetually recur, this can 

 hardly be considered as an unwarrantable assumption. But 

 whether all this has actually taken place must be judged by 

 how far the h}q5othesis accords with and explains tlie general 

 phenomena of Nature. On the other liand, the ordinary belief 

 that the amount of possible variation is a strictly-limited quan- 

 tity is a simple assumption. 



Although natural selection can act only through and for the 

 good of each being, yet characters and structures, which we 

 'are apt to consider as of very trifling importance, may thus 

 be acted on. When we see leaf-eating insects green, and bark- 

 feeders mottled-gray ; the alpine ptarmigan white in winter, 

 the red-grouse the color of heather, avc must believe that these 

 tints are of service to these birds and insects in preserving them 

 from danger. Grouse, if not destroyed at some period of their 

 lives, would increase in countless numbers ; they are known to 

 suffer largely from bii'ds of prey ; and hawks are guided by eye- 

 sight 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 natural selection miglit be 

 most eflective in giving the proper color to each kind of grouse, 

 and in keeping that color, when once acquired, true and con 



