A HISTORY OF SCIENCE 



tire. He saw that in virtue of this tendency of each 

 race of beings to overpopulate the earth, the entire 

 organic world, animal and vegetable, must be in a 

 state of perpetual carnage and strife, individual against 

 individual, fighting for sustenance and life. 



That idea fully imagined, it becomes plain that a 

 selective influence is all the time at work in nature, 

 since only a few individuals, relatively, of each genera- 

 tion can come to maturity, and these few must, nat- 

 urally, be those best fitted to battle with the particular 

 circumstances in the midst of which they are placed. 

 In other words, the individuals best adapted to their 

 surroundings will, on the average, be those that grow 

 to maturity and produce offspring. To these offspring 

 will be transmitted the favorable peculiarities. Thus 

 these peculiarities will become permanent, and nature 

 will have accomplished precisely what the human 

 breeder is seen to accomplish. Grant that organisms 

 in a state of nature vary, however slightly, one from 

 another (which is indubitable), and that such varia- 

 tions will be transmitted by a parent to its offspring 

 (which no one then doubted) ; grant, further, that there 

 is incessant strife among the various organisms, so 

 that only a small proportion can come to maturity 

 grant these things, said Darwin, and we have an ex- 

 planation of the preservation of variations which leads 

 on to the transmutation of species themselves. 



This wonderful coign of vantage Darwin had reached 

 by 1839. Here was the full outline of his theory; here 

 were the ideas which afterwards came to be embalmed 

 in familiar speech in the phrases "spontaneous varia- 

 tion," and the "survival of the fittest," through "nat- 



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