42 THE PRINCIPLE OF Chap. I. 



believe, have occurred with many instincts; for al- 

 though some instincts have been developed simply 

 through long-continued and inherited habit, other 

 highly complex ones have been developed through the 

 preservation of variations of pre-existing instincts — that 

 is, through natural selection. 



I have discussed at some little length, though as I 

 am well aware, in a very imperfect manner, the acquire- 

 ment of reflex actions, because they are often brought 

 into play in connection with movements expressive of 

 our emotions; and it was necessary to show that at least 

 some of them might have been first acquired through 

 the will in order to satisfy a desire, or to relieve a dis- 

 agreeable sensation. 



Associated liabitual movements in the lower animals. 

 — I have already given in the case of Man several in- 

 stances of movements associated with various states 

 of the mind or body, which are now purposeless, but 

 which were originally of use, and are still of use under 

 certain circumstances. As this subject is very impor- 

 tant for us, I will here give a considerable number of 

 analogous facts, with reference to animals; although 

 many of them are of a very trifling nature. My ob- 

 ject is to show that certain movements were originally 

 performed for a definite end, and that, under nearly 

 the same circumstances, they are still pertinaciously per- 

 formed through habit when not of the least use. That 

 the tendency in most of the following cases is inherited, 

 we may infer from such actions being performed in the 

 same manner by all the individuals, young and old, of 

 the same species. We shall also see that they are excited 

 by the most diversified, often circuitous, and sometimes 

 mistaken associations. 



Dogs, when they wish to go to sleep on a carpet or 



