64 VIGNETTES FROM NATURE. 



the wood-pigeons always build their nest ; on 

 those to the west, I have never roused a 

 single bird. There are certain pools in the 

 little stream which rises on the castle where 

 a certain fixed number of smallish trout are 

 always found ; but in the branch that comes 

 down from the green-sand opposite only 

 stickleback and miller's-thumbs are to be 

 caught. In fact, every part of nature is 

 a constant equilibrium : there are certain 

 species fitted for certain places, and in those 

 places only they exist. 



This balance of life is very seldom inter- 

 fered with in any way. Now and then new 

 obtrusive species push their way in ; now and 

 then fresh varieties develop and slowly oust the 

 older forms ; but on the whole the intricate 

 interdependence of all parts on one another 

 is so great that very little change ever takes 

 place. As in the village below there is always 

 a baker, and a butcher, and a doctor, and a 

 parson, and a grave-digger, each fulfilling his 

 own function, and each dependent upon the 



