300 EVOLUTION, OLD AND NEW. 



"Naturalists," he says, "have believed that the 

 possession of certain organs has led to their employ- 

 ment. This is not so : it is need and use which have 

 developed the organs, and even called them into 

 existence," [I have already sufficiently insisted that 

 it is impossible to dispense with either of these two 

 views. Demand and Supply have gone hand in hand, each 

 reacting upon the other.] " Otherwise a special act of 

 creation would be necessary for every different combi- 

 nation of conditions; and it would be also necessary 

 that the conditions should remain always constant. 



" If this were really so we should have no racehorses 

 like those of England, nor drayhorses so heavy in build 

 and so unlike the racehorse ; for there are no such 

 breeds in a wild state. For the same reason, we should 

 have no turnspit dogs with crooked legs, no grey- 

 hounds nor water-spaniels ; we should have no tailless 

 breed of fowls nor fantail pigeons, &c. Nor should we 

 be able to cultivate wild plants in our gardens, for 

 any length of time we please^ without fear of their 

 changing. 



" ' Habit,' says the proverb, ' is a second nature ' ; 

 what possible meaning can this proverb have, if descent 

 with modification is unfounded ?* 



"As regards the circumstances which give rise to 

 variation, the principal are climatic changes, different 

 temperatures of any of a creature's environments, 

 differences of abode, of habit, of the most frequent 

 actions; and lastly, of the means of obtaining food, 

 self-defence, reproduction, &c., &c." t 



• ' Phil. Zool.,' torn. i. p. 237. f Page 238. 



