290 BEHAVIOR OF THE LOWER ORGANISMS 



of carmine grains (or in any other way), this produces immediately a 

 certain physiological state (corresponding to that accompanying a sensa- 

 tion in ourselves) ; this state we may call A. This state at first produces 

 no reaction. As the carmine continues or is repeated, this state A passes 

 to a second state B, producing a bending to one side. (The two may 

 differ only slightly, but a difference must exist, otherwise B would not 

 produce a reaction while A does not.) After several repetitions of the 

 stimulus, the condition B passes to the condition C, producing a reversal 

 of the cilia, and this finally passes to D, resulting in a contraction of the 

 body. The course of the changes in physiological states may then be 

 represented as follows : — 



A—^B-^C^D 



Now we find that after many repetitions of the stimulation the or- 

 ganism contracts at once as soon as the carmine comes in contact with 

 it. In other words, the first condition A passes at once to the condition 

 D, and this results in immediate contraction. 



A-^D 



It seems probable that the same series occurs as before, save that con- 

 ditions B and C are now passed rapidly and in a modified way, so that 

 they do not result in a reaction, but are resolved directly into D. The 

 process would then be represented as follows : — 



A^B'—^C'^D 



But whatever the intermediate conditions, it is clear that after the 

 state A has become resolved, through pressure of external conditions, 

 into state D, this resolution takes place more readily, occurring at once 

 after the state A is reached. 



The same law is illustrated in the experiments of Yerkes and Spauld- 

 ing on much higher organisms. In the experiments of Spaulding 

 with the hermit crabs (Chapter XII), the introduction of the screen and 

 the diffusion of the juices of the fish cause the animals to move about. 

 In so doing they reach the dark screen, which induces, let us say, the 

 physiological condition A. This leads to no special reaction. But 

 this is followed regularly by contact with food, inducing the physiological 

 condition B, which is concomitant with a positive reaction. The physio- 

 logical condition A is thus regularly resolved into the condition B. 

 In the course of time this resolution becomes automatic, so that as soon 

 as the condition A is reached it passes at once to B. The positive reac- 

 tion concomitant with B is therefore given even though the original cause 

 of B is absent. 



