DARWIN AS FIELD NATURALIST 231 



of the Beagle I had been deeply impressed by discovering in 

 the Pampean formation great fossil animals covered with 

 armour like that on the existing armadillos ; secondly, by the 

 manner in which closely allied animals replace one another in 

 proceeding southwards over the continent; and thirdly, by 

 the South American character of most of the productions 

 of the Galapagos archipelago, and more especially by the 

 manner in which they differ slightly on each island of the 

 group ; some of the islands appearing to be very ancient in a 

 geological sense. 



" It was evident that such facts as these, as well as many 

 others, could only be explained on the supposition that 

 species gradually become modified ; and the subject haunted 

 me. But it was equally evident that neither the action 

 of the surrounding conditions, nor the will of the organisms 

 (especially in the case of plants) could account for the, 

 innumerable cases in which organisms of every kind are 

 beautifully adapted to their habits of life for instance, 

 a woodpecker or a tree-frog to climb trees, or a seed for 

 dispersal by hooks or plumes. I had always been much 

 struck by such adaptations, and until these could be 

 explained it seemed to me almost useless to endeavour 

 to prove by indirect evidence that species have been 

 modified." x 



All Darwin's varied subsequent work revolved round 

 these, for him, essential problems How do species change, 

 and how do they become adapted to their environment? 

 He never ceased to be essentially a field naturalist, and his 

 theory of natural selection would have been an empty and 

 abstract thing if his vast knowledge and understanding of the 

 " web of life " had not given it colour and form. He never 

 lost touch with the living thing in its living, breathing reality 

 even plants he rightly regarded as active things, full of 

 tricks and contrivances for making their way in the world. 

 No one ever realised more vividly than he the delicacy and 

 complexity of the adaptations to environment which are the 

 necessary condition of success in the struggle for existence. 

 Almost his greatest service to biology was that he made 



1 Life and Letters of Charles Darwin, ed. F. Darwin, i., p. 82, 

 3rd ed., 1887. 



Q 



