512 



SCIENCE. 



[N. S. Vol. IX. No. 223. 



With modesty which some hold to do him 

 less than justice, Wallace believed that Darwin 

 so much surpassed him in strength and wisdom 

 and in acquaintance with nature that it became 

 his duty to devote his life to the assistance of 

 Darwin in his efforts to extend the province of 

 human knowledge into regions that had been 

 declared closed. The intellectual revolution 

 has come about, nor will the thoughtful permit 

 Wallace's part in bringing it about to be for- 

 gotten ; nor can we forget the generous devo- 

 tion which chose the advancement of truth 

 before the natural desire for recognition and dis- 

 tinction. No one can suspect that such a man as 

 Wallace has proved himself will ignore or de- 

 preciate the share of anyone in this great work, 

 and few chapters of his book on ' The Wonder- 

 ful Century ' are more interesting than the one 

 in which he touches, very gently and tenderly, 

 upon the part which the ' philosophers ' have 

 had in the progress of natural science. 



It is one thing to show that there is no logical 

 basis for belief that species are immutable, but 

 it is quite a different matter to show what 

 modifies species. It was by finding out, and not 

 by exposing the weakness in the logic of those 

 who asserted that we never can find out, that 

 Wallace and Darwin passed the bounds where 

 they had been told that natural knowledge 

 ends. 



Lamarck, and Chambers, and Herbert Spen- 

 cer, and many others, even Wallace himself, 

 had shown that there is no reason to doubt that 

 species are mutable ; but all had failed to show 

 how the changes take place ; and many eminent 

 men of science, as well as the general public, 

 refused to consider beliefs which were as yet 

 beliefs and nothing more. 



What educated public opinion was before the 

 publication of the ' Origin ' is shown, says 

 Wallace, by the fact that neither Lamarck nor 

 Herbert Spencer nor the author of the ' Ves- 

 tiges ' had been able to make any impression 

 upon it. The very idea of progressive develop- 

 ment of species from other species was held to 

 be a ' heresy ' by such great and liberal-minded 

 men as Sir John Herschel and Sir Charles 

 Lyell ; the latter writer declaring, in the earlier 

 editions of his great work, that the facts of 

 geology are ' fatal to the theory of progressive 



development. ' The whole literary and scientific 

 worlds were violently opposed to all such theo- 

 ries, and altogether disbelieved in the possibility 

 of establishing them. It had been so long the 

 custom to treat species as special creations, and 

 the mode of their creation as the ' mystery of 

 mysteries,' that it had come to be considered 

 not only presumptuous, but almost impious, for 

 any individual to profess to have lifted the veil 

 from what was held to be the greatest and most 

 mysterious of Nature's secrets. 



Wallace tells us, ' The Wonderful Century,' 

 p. 139, that after he had studied what had been 

 written, and even after he had himself written 

 about the mutability of species; "I had no 

 conception of how or why each new form had 

 come into existence with all its beautiful adap- 

 tations to its special mode of life ; and though 

 the subject was continually being pondered 

 over, no light came to me till three years 

 later (February, 1858), under somewhat peculiar 

 circumstances. I was then living at Ternate, 

 in the Moluccas, and was suffering from a 

 rather severe attack of intermittent fever, which 

 prostrated me for several hours every day dur- 

 ing the cold and succeeding hot fits. During 

 one of these fits, while again considering the 

 problem of the origin of species, something led 

 me to think of Malthus' Essay on Population 

 (which I had read about ten years before), and 

 the 'positive checks' — war, disease, famine, 

 accidents, etc. — which he adduced as keeping 

 all savage nations nearly stationary. It then 

 occurred to me that these checks must also act 

 upon animals, and keep down their numbers ; 

 and as they increase so much faster than man 

 does, while their numbers are always nearly 

 or quite stationary, it was clear that these 

 checks in their case must be far more powerful, 

 since a number equal to the whole increase 

 must be cut off by them each year. While 

 vaguely thinking how this would affect any 

 species, there suddenly flashed upon me the 

 idea of tlie survival of the fittest — that the indi- 

 viduals removed by these checks must be, on 

 the whole, inferior to those that survived. 

 Then, considering the variations continually oc- 

 curring in every fresh generation of animals or 

 plants, and the changes of climate, of food, of 

 enemies always in progress, the whole method 



