DAk. IVIN1SM AND Of HE ft BRANCHES Of SCIENCE. 359 



Every little herring had to forage for himself, and to hide 

 from or elude his enemies as well as he could ; he had 

 no kind warning that the tide was falling and that he 

 would be left high and dry if he did not keep away from 

 the edge. I think we must admit that the few herrings 

 that survive out of a million eggs are above the average in 

 whatever qualities best adapt the herring for fighting his 

 battle of life. I will not say that they must be actually 

 the very best of the million, but I think we must admit 

 that they were among the best. 



What we have here attempted to illustrate takes place 

 in the whole realm of organized life. The organic beings, 

 animal and vegetable, tend to increase faster than the 

 limit to the supply of food or the presence of enemies will 

 permit. Many must therefore perish. No two of these 

 organisms are exactly identical. There will be trifling 

 differences (sometimes, indeed, the differences are by no 

 means trifling). It thus happens that in the struggle for 

 life one individual will have a slight advantage over 

 another. It therefore may be anticipated that the more 

 favoured individuals will be those which survive ; their 

 peculiarities will be more or less inherited by their descen- 

 dants. Thus the variations which are useful to the animal 

 will in successive generations be gradually added to, and 

 in course of time the widest changes in organization can 

 thus arise. 



It may at first seem hard to realise that so trifling a 

 change as that between one generation and the next can 

 ever by repetition amount up to so great a change as that 

 between one species of animal and another ; still less can 

 we imagine at first how animals so widely distinct as, for 



