Chap. IV. DIVERGENCE OF CHAEACTEE. 113 



We can clearly see this in the case of animals with 

 simple habits. Take the case of a carnivorous quadru- 

 ped, of winch the number that can be supported in any 

 country has long ago arrived at its full average. If its 

 natural powers of increase be allowed to act, it can 

 succeed in increasing (the country not undergoing any 

 change in its conditions) only by its varying descendants 

 seizing on places at present occupied by other animals : 

 some of them, for instance, being enabled to feed on 

 new kinds of prey, either dead or alive ; some inhabiting 

 new stations, climbing trees, frequenting water, and some 

 perhaps becoming less carnivorous. The more diversi- 

 fied in habits and structure the descendants of our car- 

 nivorous animal became, the more places they would be 

 enabled to occupy. What applies to one animal will 

 apply throughout all time to all animals — that is, if they 

 vary — for otherwise natural selection can do nothing. 

 So it will be with plants. It has been experimentally 

 proved, that if a plot of ground be sown with one species 

 of grass, and a similar plot be sown with several distinct 

 genera of grasses, a greater number of plants and a 

 greater weight of dry herbage can thus be raised. The 

 same has been found to hold good when first one variety 

 and then several mixed varieties of wheat have been 

 sown on equal spaces of ground. Hence, if any one 

 species of grass were to go on varying, and those varie- 

 ties were continually selected which differed from each 

 other in at all the same manner as distinct species and 

 genera of grasses differ from each other, a greater 

 number of individual plants of this species of grass, in- 

 cluding its modified descendants, would succeed in living 

 on the same piece of ground. And we well know that 

 each species and each variety of grass is annually 

 sowing almost countless seeds ; and thus, as it may be 

 said, is striving its utmost to increase its numbers. Con- 



