1 84 Instinct, 



prey, as the common dogs have, but he is able to 

 follow his prey when they are baffled, only by a 

 more delicate function of one special sense. In- 

 stinct leads the common dog to hunt for his mas- 

 ter's track ; but it is function that enables him to 

 find it. 



All the reciprocal influences of structure, fu-nc- 

 tion and Instinct on the being, under the varied 

 conditions to which our domestic animals are sub- 

 jected, W'iH never be understood until they have 

 been studied long, with great care. It is in this 

 field of observation, that we look for the most in- 

 teresting results, in determining the limits ofvaria- 

 tion in the whole structure and nature of the ani- 

 mal. Conceding the great changes that have taken 

 place in the modifying of forms and Instincts, we 

 see nothing yet that indicates the production of a 

 new Instinct ; and we can never be sure that an in- 

 stinct is lost simply because it does not act. An 

 instinct may lie dormant for generations because 

 there is no occasion for its activity ; but sheep warn 

 their fellows of danger, and cows hide their calves 

 when the occasion comes for calling the old instincts 

 into play. And the calf, stupid as he is, knows his 

 part of the performance in hiding, as well as though 

 trained in the best schools ! 



We have thus seen the wide application of these 

 spontaneous activities. They increase in number 

 and complexity according to the nature of the be- 

 ings in which they appear. They appear when 

 they are needed, and they pass away when there is 

 no longer use for them. They save the individual 



