126 THE LESSON OF EVOLUTION 



of the other. A dry climate could not have pro- 

 duced the water-pouches in the stomach of a camel ; 

 neither could feeding on nectar have produced the 

 honey-bag of the bee. It would be absurd to sup- 

 pose that a projection from a tube could be caused 

 by sucking liquid through it. 



Again, Professor Bumpus, of Wool's Holl, Mass., 

 has noticed changes in the shells of the periwinkles 

 and in the eggs of the sparrows which have been 

 introduced from Europe, and he thinks that these 

 -changes are due to the new environment. But he 

 does not suggest any reasons why sparrow's eggs 

 -should be smaller and rounder, and why the shells 

 of periwinkles should be thinner and longer in 

 America than in Europe. Here we must remember 

 that as animals are frequently changing their en- 

 vironment, and at the same time are frequently 

 varying, the two must often occur together ; and w r e 

 cannot say that the change in character is due to 

 the change in environment, unless we can connect 

 one with the other, either by explaining why one 

 should affect the other, or by shewing experimen- 

 tally that such is the case. 



Darwin made an extensive examination of the 

 facts, known up to his time, relating to the direct 

 action of the environment on plants and animals ; 

 and came to the conclusion that the effect was slight. 

 But in later years he, to some extent, altered his 

 opinion. It is a well known fact that many species 

 -of animals and plants are almost cosmopolitan, living 

 under very various conditions ; and yet they shew no 

 change ; while variations often arise when the 



