3i6 BEHAVIOR OF THE LOWER ORGANISMS 



regularly resolved into an intense one, corresponding to a strong negative 

 reaction. Then after many repetitions of this process the indifferent 

 state resolves itself at once into the intense one, and the animal reacts 

 at the change in illumination, before the enemy has reached it. This, 

 tendency to react to "representative" factors, rather than to those 

 which are in themselves beneficial or injurious, is, of course, immensely 

 developed in higher animals. All positive or negative reactions to things 

 merely seen or heard, which are not directly beneficial or injurious save 

 when brought into direct contact with the organism, are, of course, reac- 

 tions to such representative stimuli. 



It is clear that neither the tendency to react to faint stimuli, nor that 

 to react to "representative" factors will be increased, save as this is 

 required by the environment. If th^ indifferent stimulus is not followed 

 with some regularity by the powerful one ; that is, if it does not really 

 introduce a powerful agent, then ttiere v^dll be no tendency for the or- 

 ganism to acquire a reaction to this indifferent stimulus, for there will 

 be no regular resolution of the first (faint) physiological change into the 

 second (intense) one. And of course it would be no advantage, but on the 

 contrary a positive disadvantage, for the organism to acquire this ten- 

 dency to react to all weak stimuli. If it reacted negatively to every slight 

 change in the environment, its movements would be seriously impeded ; 

 continued locomotion in any one direction would be almost impossible, 

 and its activity would be frittered away in useless and disconnected reac- 

 tions. The behavior becomes modified, in accordance with the prin- 

 ciples above set forth, only as it is to the advantage of the organism that 

 it should be so modified; that is, only as the modification favors the 

 normal current of life activities. 



(3) Progress takes place through increase in the complexity and 

 permanence of physiological states, and in the tendency to react to these 

 derived and complex states, instead of to the primitive and simple ones. 

 We may imagine an organism whose physiological state depends entirely 

 on the stimulus now acting upon it, the organism returning completely, 

 as soon as the stimulus ceases, to its original state. Such an organism 

 could react only with relation to the present stimulus, and its reaction to 

 the same stimulus would always be the same. We might even imagine an 

 organism that could change in only one way under the action of stimuli ; 

 its reactions to all stimuli would be the same. Such organisms would 

 represent a purely reflex type of behavior. An advance on this condi- 

 tion would be represented by cases where the physiological state induced 

 by a stimulus endures for a short time, influencing the immediately 

 succeeding reactions, and a further advance when the reaction performed 

 by the organism influences its physiological state, and therefore its later 



