LECT. III.] FEEDING GROUNDS. 65 



" conquest of the Canaanites " is only the partial 

 working of a general law, in which Nature is always 

 doing for every great fauna what the farmer does who 

 seeks to improve the breed of his cattle. 



From year to year, as you may perhaps know, the 

 sheep are brought " under the hands of him that telleth 

 them," and he, guiding his hand wittingly, judges with 

 quick motion, which are fittest to be next year's mothers, 

 and which are to be appointed for slaughter. - 



His wisdom and intelligence are great, but how little, 

 as compared with what his great Earth-mother the 

 farmer of farmers has shown ever since the green earth 

 was first stocked ! Of this huge farm, with its great un- 

 enclosed tracts of pasturage, the forms least able to bear 

 changes of condition die out first. But there are various 

 ways in which such changes necessarily affect living 

 creatures, and one of these is caused by the frequent im- 

 migrations made by the herbivorous tribes as the pastures 

 become bare, and by the carnivorous tribes who follow 

 them for plunder. Change of feeding-ground means 

 also change of climate, more or less, to hotter or colder, 

 to wetter or drier. Instinct, as we all know, is only an 

 imperfect guide, and the animal tribes have to learn. 

 Their tact is not always inborn, or always accurate ; 

 as an instance, I will mention one familiar to me from 

 childhood. When our upland sheep used to close, 

 quick fences are removed to the fen-districts, where 

 the fields are enclosed by straight canals, there are 



