88 THE ORIGIN OF SPECIES 



We can clearly discern this in the case of animals with simple 

 habits. Take the case of a carnivorous quadruped, of which the 

 number that can be supported in any country has long ago arrived 

 at its full average. If its natural power of increase be allowed to 

 act, it can succeed in increasing (the country not undergoing any 

 change in 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 

 diversified in habits and structure the descendants of our carniv- 

 orous animals become, the more places they will 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 selec- 

 tion can effect nothing. So it will be with plants. It has been ex- 

 perimentally 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 be raised in the latter than the former case. 

 The same has been found to hold good when one variety and sev- 

 eral 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 the varieties were continually selected which differed from 

 each other in the same manner, though in a very slight degree, as 

 do the distinct species and genera of grasses, a greater number of 

 individual plants of this species, including its modified descend- 

 ants, would succeed in living on the same piece of ground. And we 

 know that each species and each variety of grass in annually sow- 

 ing almost countless seeds ; and is thus striving, as it may be said, 

 to the utmost to increase in number. Consequently, in the course 

 of many thousand generations, the most distinct varieties of any 

 one species of grass would have the best chance of succeeding and 

 of increasing in numbers, and thus of supplanting the less distinct 

 varieties; and varieties, when rendered very distinct from each 

 other, take the rank of species. 



The truth of the principle that the greatest amount of life can 

 be supported by great diversification of structure, is seen under 

 many natural circumstances. In an extremely small area, especially 

 if freely open to immigration, and where the contest between indi- 

 vidual and individual must be very severe, we always find great 

 diversity in its inhabitants. For instance, I found that a piece of 

 turf, three feet by four in size, which had been exposed for many 

 years to exactly the same conditions, supported twenty species of 



