INDIRECT EQUILIBRATION. 539 



spines. And it would be an assumption still more straining 

 our powers of belief, that along with heavier horns there 

 should spontaneously take place the required strengthenings 

 in the bones, muscles, arteries, and nerves of the scapular 

 and the fore-legs. 



Besides the multiplicity of directly-cooperative organs, the 

 multiplicity of organs which do not cooperate, save in the 

 degree implied by their combination in the same organism, 

 seems to me a further hindrance to the development of 

 special structures by natural selection alone. Where the life 

 is simple, or where circumstances render some one function 

 supremely important, survival of the fittest may readily 

 bring about the appropriate structural change, without aid 

 from the transmission of functionally-caused modifications. 

 But in proportion as the life grows complex in proportion 

 as a healthy existence cannot be secured by a large endow 

 ment of some one power, but demands many powers; in the 

 same proportion do there arise obstacles to the increase of 

 any particular power by &quot; the preservation of favoured races 

 in the struggle for life.&quot; As fast as the faculties are multi 

 plied, so fast does it become possible for the several members 

 of a species to have various kinds of superiorities over one 

 another. While one saves its life by higher speed, another 

 does the like by clearer vision, another by keener scent, 

 another by quicker hearing, another by greater strength, 

 another by unusual power of enduring cold or hunger, 

 another by special sagacity, another by special timidity, 

 another by special courage; and others by other bodily and 

 mental attributes. Conditions being alike, each of these life- 

 saving attributes is likely to be transmitted to posterity. But 

 we may not assume that it will be increased in subse 

 quent generations by natural selection. Increase of it can 

 result only if individuals possessing average endowments of 

 it are more frequently killed off than individuals highly 

 endowed with it ; and this can happen only when the attri 

 bute is one of greater importance, for the time being, than 



