Chap. IV. 
DIVEKGENCE OF CHAEACTER. 
113 
We can clearly see tliis in the case of animals with 
simple habits. Take the case of a carnivorous quadru¬ 
ped, of which 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- 
