44 THE POPULAR SCIENCE MONTHLY 



of the JSTeodarwinians so far as natural selection goes. By far the most 

 important nexus between Darwin and Weismann, when it comes to the 

 deeper reaches of biological theory, is through Darwin's pangenesis 

 hypothesis and Weismann's germ-plasm-determinant doctrine. This I 

 treat at length elsewhere. It may be left to one side here because of its 

 relative unimportance as touching Darwin's work proper, though of 

 fundamental importance to an exhaustive discussion of the present 

 status of biological philosophy. 



Mr. Wallace's ungrudging recognition of Darwin's towering genius 

 as compared with his own is one of the particularly bright and inspirit- 

 ing examples of what personal relationship between men may be. And 

 to Mr. Wallace is the greater honor because his was the lesser intellec- 

 tual endowment and achievement. 



Turning from Mr. Wallace's beautifully deferential attitude toward 

 his friend, to the facts upon which he based this, what do we find ? 



We have already seen that Darwin had convinced himself of the 

 truth of descent with modification before he thought of natural selec- 

 tion, and that it was the essay of Malthus on population that gave him 

 the idea of struggle and survival. On December 22, 1857, he said in a 

 letter to Mr. Wallace: 



My work at which I have now been at work more or less for twenty years, 

 will not fix or settle anything ; but I hope it will aid by giving a large collec- 

 tion of facts, with one definite end. 8 (Italics mine.) 



It should be remembered that Malthus's essay was read in 1837. 



The circumstances under which Mr. Wallace became the co-pro- 

 pounder of evolution and co-discoverer of natural selection are told by 

 himself. He says: 



After writing the preceding paper (On the Law which has Regulated the 

 Introduction of New Species) the question of how changes in species could have 

 been brought about was rarely out of my mind, but no satisfactory conclusion 

 was reached till February, 1858. At that time I was suffering from a rather 

 severe attack of intermittent fever at Ternate in the Moluccas, and one day, 

 while lying on my bed during the cold fit, wrapped in blankets, though the 

 thermometer was 88° Fahrenheit, the problem again presented itself to me, and 

 something led me to think of the " positive checks " described by Malthus in 

 his " Essay on Population," a work I had read several years before, and which 

 had made a deep and permanent impression on my mind. These checks — war, 

 disease, famine and the like — must, it occurred to me, act on animals as well 

 as man. Then I thought of the enormously rapid multiplication of animals, 

 causing these checks to be much more effective in them than in the case of man ; 

 and while pondering vaguely upon this fact there suddenly flashed upon me 

 the idea of the survival of the fittest — that the individuals removed by these 

 checks must be on the whole inferior to those that survived. In the two hours 

 that elapsed before my ague fit was over, I had thought out almost the whole 

 of the theory, and the same evening I sketched the draft of my paper, and in 

 the two succeeding evenings wrote it out in full, and sent it by the next post 

 to Mr. Darwin. 



8 " Letters," I., p. 467. 



