84 DARWINISM STATED BY DARWIN HIMSELF. 



a struggle at some period of its life ; that heavy destruc- 

 tion inevitably falls either on the young or old during 

 each generation or at recurrent intervals. Lighten any 

 check, mitigate the destruction ever so little, and the 

 number of the species will almost instantaneously increase 

 to any amount. 



"inexplicable on the theory of creation." 



Origin of -^ s eac ^ s P e °i es tends by its geometrical 



Species, rate of reproduction to increase inordinately 

 page *i.o. - n numDerj an d as the modified descendants 

 of each species will be enabled to increase by as much as 

 they become more diversified in habits and structure, so 

 as to be able to seize on many and widely different places 

 in the economy of nature, there will be a constant tend- 

 ency in natural selection to preserve the most divergent 

 offspring of any one species. Hence, during a long-con- 

 tinued course of modification, the slight differences charac- 

 teristic of varieties of the same species tend to be aug- 

 mented into the greater differences characteristic of the 

 species of the same genus. New and improved varie- 

 ties will inevitably supplant and exterminate the older, 

 less improved, and intermediate varieties ; and thus spe- 

 cies are rendered to a large extent defined and distinct 

 objects. Dominant species belonging to the larger groups 

 within each class tend to give birth to new and dominant 

 forms ; so that each large group tends to become still 

 larger, and at the same time more divergent in character. 

 But, as all groups can not thus go on increasing in size, 

 for the world would not hold them, the more dominant 

 groups beat the less dominant. This tendency in the 

 large groups to go on increasing in size and diverging in 

 character, together with the inevitable contingency of 



I 



