rnxr. IV. DIVERGENCE or CHARACTER. HI 



Ibnnin;^ two sub-breeds; finally, after the lapse of centuries 

 the sub-breods would become converted into two ■well-estab- 

 lished and distinct breeds. As the dilVerenccs slowly became 

 ,e:reater, the inferior animals with intermediate characters, bein;i^ 

 neither very swift nor very strong, would have been neglected, 

 and will have disappeared. Here, then, we see in man's pro- 

 ductions the action of what may be called the principle of 

 divergence, causing differences, at first barely appreciable, 

 steadily to increase, and the breeds to diverge in character 

 both from eacli other and from their common pax-ent. 



But 1»()W, it may be asked, can any analogous principle 

 apply in Nature ? t believe it can and does apply most effi- 

 ciently (though it Avas a long time before I saw how), from tlie 

 simple circumstance that the more diversified the descendants 

 from any one species become in structure, constitution, and 

 habrts, by so much will they be better enabled to seize on many 

 and widely-diversified places in the polity of Nature, and so be 

 enabled to increase in numbers. 



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 an}?- 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 imdergoing 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 inhabit- 

 ing new stations, climbing trees, frequenting water, and some 

 [lerliaps becoming less carnivorous. The more diversified in 

 lialjits and structure the descendants of our carnivorous animal 

 lir'came, the more places they would bo enabled to occupy. 

 AViiat 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 witli j^lants. It has been 

 experimentally proved that, if a plot of ground be sown witli 

 one species of grass, and a similar plot be sown with several 

 distinct genera of grasses, a greater number of phmts and a 

 greater weight of dry herbage can be raised by the latter jjro- 

 ccss. Tlie same has been found to hold good when one va- 

 riety and several mixed varieties of wlieat liave been sown on 

 equal spaces of ground. Hence, if any one species of grass 

 were to go on varying, and those varieties were continually 

 selected which differed from each other in at all the same man- 



