DARWIN'S DISCOVERIES 19 



a single pair, on the average, survive, a necessary selection 

 of those which are to survive and breed, accompanied by 

 a rejection and destruction of the rest This " natural 

 selection " or survival of favoured varieties, he was 

 able to show, must operate like the selection made by 

 breeders, fanciers, and horticulturists, and has in all 

 probability (for in a history extending over hundreds 

 of thousands of years we must necessarily deal with 

 " probabilities," and not with direct demonstration) pro- 

 duced new forms, new kinds, better adapted to their 

 surroundings than the parental forms from which they are 

 derived. 



It was necessary, in order that Darwin should persuade 

 other naturalists that his views were correct, that he 

 should show by putting examples " on the table " that 

 variations occur naturally and in great diversity ; further, 

 that there is great pressure in the conditions of life, and 

 a consequent survival of the best-suited varieties ; further, 

 that there is in reproduction a transmission of the peculiar 

 favouring character or quality which enables a variety to 

 survive, and thus a tendency to perpetuate the new 

 quality. It was not enough for Darwin to "imagine" 

 that these things might be so, or to make the notion 

 that they are so plausible by arguments drawn from 

 existing knowledge. He had to do that: but also he 

 had to make new inquiries and discover new things about 

 animals and plants which fitted in with his theory and 

 would not fit in either with the notion that all plants 

 and animals were created as the poet Milton supposed 

 out of lumps of earth and muddy water, suddenly, 

 in the likeness of their present-day descendants, nor 

 with some other notions, such as that of the able and 

 gifted French naturalist Lamarck. And he spent the 

 later twenty years of his life in doing so, just as he had 

 spent the previous twenty years in collecting a first series 



