324 BEHAVIOR OF THE LOWER ORGANISMS 



of natural selection. Only such characteristics can be selected as are 

 in line with the efforts of the organism. A variation which might be of 

 inestimable advantage to an organism that reacts by swimming would 

 be entirely lost on one that burrows in the earth. The organism deter- 

 mines by its own actions the direction of its development under the 

 action of natural selection. When it adopts a certain line of behavior, 

 it decides to a large degree the future career of the race. Development 

 through the action of natural selection must then follow as definite a 

 trend as does the behavior of the individual and indeed the same trend, 

 for it is guided by this behavior. Individual selection guides natural 

 selection. 



Individual selection, with its production of definite adaptive reac- 

 tions, is due, of course, to selection from varied movements, later fixed 

 by the law of the readier resolution of physiological states. 1 With this 

 in mind, we may express what we have just brought out as follows: In- 

 dividual selection (intelligence) and natural selection are merely different 

 methods of selecting adaptive ways of reacting. The former selects 

 the adaptive response from among diverse reactions of the same indi- 

 vidual; while natural selection selects the adaptive response from among 

 diverse reactions of different individuals. 



This may be illustrated as follows: Let us suppose an organism 

 whose action system includes the different acts i, 2, 3, 4, 5, 6, 7, 8, 9. 

 When the physiological processes of this animal are interfered with by 

 external agents, it tends to run through these nine reactions, in the order 

 given above as Stentor runs through its four or five reactions. Sup- 

 pose that under a certain frequently recurring injurious condition the 

 reaction 7 is the adaptive one, relieving the interference with the physio- 

 logical processes. The organism runs through the series to 7, then stops 

 (since the cause for further reaction has ceased). It now retains this 

 reaction as the immediate response to the given condition, through the 

 law of the readier resolution of physiological states. Many of the indi- 

 viduals are killed before 7 is reached, but after this adaptive reaction has 

 become fixed, no others are killed. The young of these individuals 

 must, however, begin at the beginning of the series, so that many will 

 be destroyed. 



Let us suppose that in another group there are, among many different 

 individuals, congenital variations in the order in which the nine re- 

 sponses are given. Some respond by the series 2, 3, 7, i, 4, 5, 6, 8, 9. 

 These reach the adaptive reaction 7 sooner than do those following the 

 usual order, hence fewer are killed by the injurious condition. Others 

 react in the order 7, 4, 3, 5, i, 2, 6, 8, 9. The first reaction is here the 



1 This is the process known as intelligence, in higher animals. See Chapter XX. 



