42 LIFE OF 



relations as variation of climate and food, or intro- 

 duction of enemies, or the increased numbers of other 

 species, as the cause of the succession of races." But 

 he does not yet go farther. He ends his reflections by 

 observing : " All that at present can be said with certainty 

 is that, as with the individual, so with the species, the 

 hour of life has run its course, and is spent." 



In the second edition of the Journal the philosopher 

 showed signs of considerable advance (pp. 1 74-5). The 

 effect of changed conditions is further developed. The 

 checks to indefinite multiplication are insisted on, while 

 the tendency of every species to increase geometrically 

 is clearly pointed out. In the place of the former con- 

 cluding sentence we find the following : " To admit that 

 species generally become rare before they become 

 extinct to feel no surprise at the comparative rarity of 

 one species with another, and yet to call in some extra- 

 ordinary agent and to marvel greatly when a species 

 ceases to exist, appears to me much the same as to admit 

 that sickness in the individual is the prelude to death 

 to feel no surprise at sickness but when the sick man 

 dies, to wonder, and to believe that he died through 

 violence." 



The continental regions of South America did not 

 supply the sole food for the reflections of the young 

 naturalist during this period. An intervening visit had 

 been paid, in December, 1832, and January, 1833, to 

 Tierra del Fuego, and the natives were most carefully 

 observed. He was greatly struck by their low condition ; 

 " one can hardly make oneself believe they are fellow 

 creatures, and inhabitants of the same world." Yet 



