114 THE ORIGIN OF SPECIES 



tervention first of mice and then of bees, the frequency 

 of certain flowers iu that district! 



In the case of every species, many different checks, 

 acting at different periods of life, and during different 

 seasons or years, probably come into play; some one 

 check or some few being generally the most potent; bat 

 all will concur in determining the average number or 

 even the existence of the species. In some cases it can 

 be shown tliat widely-different checks act on the same 

 species in different districts. When we look at the plants 

 and bushes clothing an entangled bank, we are tempted 

 to attribute their 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 vegetation 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 centu- 

 ries between the several kinds of trees, each annually 

 scattering its seeds by the thousand; what war between 

 insect and insect — between insects, snails, and other ani- 

 mals 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 that of 

 the action and reaction of the innumerable plants and 

 animals which have determined, in the course of centu* 



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