TRANSMISSION OF MODIFICATIONS 387 



Thus the whole question is up again in this connection. Will 

 the habit of the individual be transmitted to its offspring ? Is 

 the habit of one generation the instinct of the next ? If so, then 

 we have a case of transmission of modifications (inheritance of 

 acquired characters) of the most direct and certain kind. 



The answer to the question is important for its own sake, but 

 more especially for the light it may throw upon the main ques- 

 tion now in hand. To arrive at a safe answer it is necessary to 

 give more than a passing notice to the nature of instinctive acts, 

 and to critically determine whether instinct is built upon habit 

 or habit upon instinct. 



Nature of instinctive acts. Most acts of intelligent beings 

 are performed for a particular purpose and for definite ends. 

 Most such acts are controlled by a greater or less degree of 

 purposeful adaptation of means to end that involves knowledge 

 of results, based on experience and merging naturally into habit. 

 Habit is then the customary use to which the individual puts the 

 parts with which it is endowed by nature, after they have reached 

 full development. Its chief interest to us at this point arises 

 from the fact that another individual might put the same parts 

 to a different use, while in instinctive acts use is a function of 

 structure, and but one set of actions is possible except under 

 greatly changed conditions. 



The term " instinctive " is applied to those acts which are per- 

 formed without previous experience and perhaps under circum- 

 stances that preclude all knowledge of what the result will be ; 

 so that, as far as the individual is concerned, there is, and can be, 

 no consciousness of purposeful action or of adaptation of means 

 to end, and yet the action, often complicated in the extreme, 

 may be eminently adaptive and exhibit every appearance of being 

 the act of a most intelligent being. Young mammals suck with 

 the lips ; young waterfowls swim and dive, but land birds do not ; 

 young squirrels hide objects, and even in a room go through the 

 motions of digging and burying ; young chicks have their own 

 peculiar cry, and peck at shining objects ; birds build their nests 

 without instruction or assistance from older or more experienced 

 individuals. These are instinctive acts of the simplest order ; 

 many others, however, are extremely complicated. For example, 



