INSTINCT 209 



other habits, with certain periods of time and states of the body. 

 When once acquired, they often remain constant throughout life. 

 Several other points of resemblance between instincts and habits 

 could be pointed out. As in repeating a well-known song, so in 

 instincts, one action follows another by a sort of rhythm; if a 

 person be interrupted in a song, or in repeating anything by rote, 

 he is generally forced to go back to recover the habitual train of 

 thought; so P. Huber found it was with a caterpillar, which makes 

 a very complicated hammock; for if he took a caterpillar which 

 had completed its hammock up to, say, the sixth stage of construc- 

 tion, and put it into a hammock completed up only to the third 

 stage, the caterpillar simply re-performed the fourth, fifth and 

 sixth stages of construction. If, however, a caterpillar were taken 

 out of a hammock made up, for instance, to the third stage, and 

 were put into one finished up to the sixth stage, so that much of 

 its work was already done for it, far from deriving any benefit from 

 this, it was much embarrassed, and in order to complete its ham- 

 mock, seemed forced to start from the third stage, where it had 

 left off, and thus tried to complete the already finished work. 



If we suppose any habitual action to become inherited — and it 

 can be shown that this does sometimes happen — then the resem- 

 blance between what originally was a habit and an instinct be- 

 comes so close as not to be distinguished. If Mozart, instead of 

 playing the piano-forte at three years old with wonderfully little 

 practice, had played a tune with no practice at all, he might truly 

 be said to have done so instinctively. But it would be a serious 

 error to suppose that the greater number of instincts have been 

 acquired by habit in one generation, and then transmitted by in- 

 heritance to succeeding generations. It can be clearly shown that 

 the most wonderful instincts with which we are acquainted, 

 namely, those of the hive-bee and of many ants, could not pos- 

 sibly have been acquired by habit. 



It will be universally admitted that instincts are as important as 

 corporeal structures for the welfare of each species, under its 

 present conditions of life. Under changed conditions of life, it is 

 at least possible that slight modifications of instinct might be 

 profitable to a species; and if it can be shown that instincts do 

 vary ever so little, then I can see no difficulty in natural selection 

 preserving and continually accumulating variations of instinct to 

 any extent that was profitable. It is thus, as I believe, that all the 

 most complex and wonderful instincts have originated. As modi- 

 fications of corporeal structure arise from, and are increased by, 

 use or habit, and are diminished or lost by disuse, so I do not 



