294 EVOLUTION, OLD AND NEW. 



supposed that its surroundings directly effect any 

 modification whatever in the form and organization of 

 an animal.* Great changes in surroundings involve 

 great changes in the wants of animals, and these changes 

 in their wants involve corresponding changes in their 

 actions. If these new wants become permanent, 

 or of very long duration, the animals contract new 

 habits, which last as long as the wants which gave rise 

 to them.f A great change in surroundings, if it persist 

 for a long time, must plainly, therefore, involve the con- 

 traction of new habits. These new habits in their turn 

 involve a preference for the employment of such and 

 such an organ over such and such another organ, and in 

 certain cases the total disuse of an organ which is no 

 longer wanted. This is perfectly self-evident. % 



"On the one hand, new wants have rendered a 

 part necessary, which part has accordingly been created 

 by a succession of efforts : use has kept it in existence, 

 gradually strengthening and developing it till in the 

 end it attains a considerable degree of perfection. On 

 the other, new circumstances having in some cases 

 rendered such or such a part useless, disuse has led to 

 its gradually ceasing to receive the development which 

 the other parts attain to ; on this it becomes reduced, 

 and in time disappears. § 



" Plants have neither actions nor habits properly so 

 called, nevertheless they change in a changed environ- 

 ment as much as animals do. This is due to changes 

 in nutrition, absorption and transpiration, to degrees of 



* 'Phil. Zool.,' torn. i. p. 223. f Page 223. 

 X Page 224. § Page 225. 



