44 H- G. Kribs 



movements, for the most part at least, is set free by the rearrange- 

 ment of certain chemical aggregates within the animal itself. 

 These internal changes which find expression in external move- 

 ment are a fundamental part of the animal economy. They tend 

 to restore or maintain a certain physiological equilibrium which 

 is essential to its well being. 



On the other hand, the ultimate source of the energy which 

 gives rise to these movements comes to the animal through ex- 

 ternal media. As the animal moves about it is constantly com- 

 ing in contact with other supplies of energy which have their 

 play in its environment, and there immediately results a mutual 

 reaction between the animal economy and the external supply of 

 energy or "stimulus" thus encountered. The form of the 

 reaction that may be exhibited upon such a contact depends both 

 upon the morphological and physiological organization of the 

 animal, and also upon the sort of stuff that may house the exter- 

 nal energy. If this energy be in the form of food particles, for 

 instance, it may be readily appropriated through the various 

 channels of ingestion and assimilation. If it be such as to dis- 

 turb the internal processes, other and varied movements may 

 result. The sum totalof all themovementsexhibitedby i^iolosoma 

 in a given time, in response to a changing environment, we desig- 

 nate as its behavior. 



The problem of behavior from this point of view naturally 

 hinges upon the interpretation of the relations which exist be- 

 tween the external stimulus and the concomitant reaction of the 

 animal. 



As an introduction to this subject we will first consider themorph- 

 ological basis of the behavior of .T-olosoma; its movements and 

 reactions in a state of nature; and finally physiological effects 

 produced through physical changes in its environment. We will 

 then investigate the movements and reactions of x^olosoma under 

 the control of definite chemical stimulations associated with 

 certain changes in its environments as suggested by these obser- 

 vations on its natural history. 



I wish to express my deep obligation to Prof. H. S. Jennings, 

 who suggested this problem to me, and for his kind assistance in 



