Alfred Russel Wallace 



rest each day, owing to the exhausting hot and cold fits 

 which rapidly succeeded one another. 



The little bungalow at Ternafe had now come to be re- 

 garded as ^^ home,'^ for it was here that he stored all his 

 treasured collections, besides making it the goal of all his 

 wanderings in the Archipelago. One can understand, there- 

 fore, that, in spite of the fever, there was a sense of satis- 

 faction in the feeling that he was surrounded with the 

 trophies of his arduous labours as a naturalist, and this 

 passion for species and their descriptions being an ever- 

 present speculation in his mind, his very surroundings 

 would unconsciously conduce towards the line of thought 

 which brought to memory the argument of " positive 

 checks " set forth by Malthus in his *^ Principles of Popu- 

 lation " (read twelve years earlier) as applied to savage 

 and civilised races. *^ It then,'' he says, ^* occurred to me 

 that these causes or their equivalents are continually act- 

 ing in the case of animals also; and as animals usually 

 breed much more rapidly than does mankind, the destruc- 

 tion every year from these causes must be enormous in 

 order to keep down the numbers of each species, since they 

 evidently do not increase regularly from year to year, as 

 otherwise the world would have been densely crowded with 

 those that breed most quickly. ... Then it suddenly flashed 

 upon me that this self-acting process would necessarily im- 

 prove the race, because in every generation the inferior would 

 inevitably be killed off and the superior would remain — that 

 is, the fittest would survive. Then at once I seemed to see 

 the whole effect of this, that when changes of land and sea, 

 or of climate, or of food- supply, or of enemies occurred — 

 and we know that such changes have always been taking 

 place — and considering the amount of indivicjual variation 

 that my experience as a collector had shown me to exist, 

 then it followed that all the changes necessary for the 



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