No t ices of New Books. 7591 



believes to be at work under a state of nature, the prime mover of 

 which is the struggle for existence treated of in Chapter III, on the 

 reproductive powers being in excess of the necessities for keeping up 

 animal and vegetable population, involving the destruction of a large 

 proportion of the individuals that are brought into existence. In 

 illustration of this Mr. Darwin says, at page 67 (third edition) : — 

 " There is no exception to the rule that every organic being naturally 

 increases at so high a rate that, if not destroyed, the earth would soon 

 be peopled by the progeny of a single pair. Even slow-breeding 

 man has doubled in twenty-five years, and at this rate in a few 

 thousand years there would literally not be standing room for his 

 progeny. Linneus has calculated that if an annual plant produced 

 only two seeds — and there is no plant so unproductive as this — and 

 their seedlings next year produced two seeds, and so on, in thirty 

 years there would be a million plants. The elephant is reckoned the 

 slowest breeder of all known animals, and I have taken some pains to 

 calculate its probable minimum rate of natural increase ; it would be 

 under the mark to assume that it breeds when thirty years old, and 

 goes on breeding till ninety years old, bringing forth three pairs of 

 young in this interval. If this be so at the end of the fifth century, 

 there would be alive fifteen millions of elephants, descended from the 

 first pair." Mr. Darwin asks, — Then who is to die and who is to live 

 of this excessive progeny ? Nature replies, — If they differ, the weakest 

 must give way. Mr. Darwin says, on the principle of " variation 

 under nature " they do differ ; some are a Httle worse and some a 

 little better than their parents ; and that the weakest must die, and 

 the strongest and best live and become the parents of the next gene- 

 ration, which inherits not only the advantageous quality, by which its 

 parents obtained the mastery, but an increased measure of that advan- 

 tage, for the descendants not only inherit thequality of the variation but 

 also the property of variability, and so on and on, till this particular 

 quality becomes intensified, and the property of a numerous race, who 

 as soon as they become too numerous for their particular sphere, again 

 split up on some little advantageous "variations, which in their turn 

 become the characteristic properties of each section of the divided 

 race. The first thoughts that this theory of the production of species 

 by these infinitely small steps of variation suggest are, — How is it 

 that we get any individuality in the character of species ? and how is 

 it that species do not merge into each other by almost insensible gra- 

 dations ? If this property of variability is an inherent principle, and 

 may be not merely an occasional accident, but the property, in 



