196 THE FOUNDATIONS OF ZOOLOGY 



We must not think of natural selection, after the analogy of 

 artificial selection, as a competitive examination in one subject, 

 where failure to pass means loss of all future chances. Rather 

 must we think of it as a long but indefinite series of examina- 

 tions, each in innumerable subjects, some of which count for 

 much, others for little, some for very little, but all for something. 

 We must, furthermore, suppose that all candidates who do not 

 fail utterly may try again and again, but that each partial failure 

 may, if some other candidate does better, diminish, in so far, the 

 chance for success in future trials. 



" Many different checks, acting at different periods of life, 

 and during different seasons or years, probably come into play ; 

 but all will concur in determining the result. When we look at 

 the plants and bushes clothing an entangled bank, we are tempted 

 to attribute the proportional numbers and kinds to what we call 

 chance. But how false a view is this ! Every one has heard 

 that when an American forest is cut down, a very different vege- 

 tation springs up ; but it has been observed that ancient Indian 

 ruins in the southern United States, which must formerly have 

 been cleared of trees, now display the same beautiful diversity 

 and proportion of kinds as in the surrounding virgin forest. 

 What a struggle must have gone on during long centuries be- 

 tween the several kinds of trees, each annually scattering its 

 seeds by the thousand; what a war between insect and insect, 

 between insects, snails, and other animals, with birds and beasts 

 of prey, all striving to increase, all feeding on each other, or 

 on the trees, their seeds and seedlings, or on the other plants 

 which first clothed the ground, and thus checked the growth of 

 the trees ! Throw up a handful of feathers, and all fall to the 

 ground according to definite laws; but how simple is the problem 

 where each shall fall, compared to the action and reaction of the 

 innumerable plants and animals which have determined, in the 

 course of centuries, the proportional numbers and kinds of trees 

 now growing on the old Indian ruins ! " l 



While the breeder cannot consciously and deliberately select 

 any peculiarity which has not enough selective value to attract 

 his notice, I do not see how any one who is familiar with Dar- 



1 " Origin," p. 58. 



