1 50 Hillside. 



hunted by beasts of prey on the African plains, have de- 

 veloped races characterised by speed and endurance. But 

 the races produced in this manner have taken much longer 

 to develop than if man had selected only those animals most 

 highly developed in the desired direction and bred from them 

 in each generation, as he has done with the race-horse, 

 because man would eliminate more rapidly those elements 

 which militated against the desired object. Man would pro- 

 duce more striking results in a short time ; but the work 

 performed by Nature is as perfect, although spread over a 

 longer period of time. 



Let us consider an instance of the production of a distinct 

 race in response to a change of environment which is actually 

 in progress around us. A few decades back coal was scarcely 

 used, except for manufacturing purposes, and comparatively 

 little even for those. Even to-day it is very little used in 

 country villages where wood can still be had abundantly. 

 Bat in our large cities and towns, and especially in the 

 manufacturing districts at the present time, vast masses of 

 smoke pour daily from multitudinous chimneys, and the 

 atmosphere there is in consequence polluted with particles 

 of carbon. When rain falls these particles are carried down 

 by it and deposited on the ground, on fences, on trees ; in 

 short, on everything around. When the water evaporates 

 the solid matter is left behind, and hence the fences and 

 trunks of trees in and near our large cities and manu- 

 facturing centres are black, instead of grey or brown, which 

 are their ordinary tints. A large number of moths rest on 

 fences, tree trunks, and similar places, with their wings 

 stretched out fiat on them. You remember the Carpet 

 moths on Ben Donicli, and how difficult it was to see them 



