Vi PREFACE 



the regulatory aspect of behavior special attention is paid in the 

 following pages. 



The modifiability of the characteristics of organisms has always 

 been a subject of the greatest importance in biological science. In 

 most fields the study of this matter is beset with great difficulties, for 

 the modifications require long periods and their progress is not easily 

 detectible. In the processes of behavior we have characteristics that 

 are modifiable with absolute ease. In the ordinary course of be- 

 havior variations of action are continually occurring, as a result of 

 many internal and external causes. We see quickly and in the gross 

 the changes produced by the environment, so that we have the best 

 possible opportunity for the study of the principles according to 

 which such changes occur. Permanent modifications of the methods 

 of action are easily produced in the behavior of many organisms. 

 When we limit ourselves to the subjective aspect of these, thinking 

 only of memory, or the like, we tend to obscure the general problem 

 involved. This problem is : What lasting changes are producible in 

 organisms by the environment or otherwise, and what are the princi- 

 ples governing such modifications ? Perhaps in no other field do we 

 have so favorable an opportunity for the study of this problem, 

 fundamental for all biology, as in behavior. There seems to be no 

 a priori reason for supposing the laws of modification to be different 

 in this field from those found elsewhere. The matter needs to be 

 dealt with from an objective standpoint, keeping the general problem 

 in mind. 



A study of behavior from the objective standpoint will help us 

 to realize that the activities with which we deal in other fields of 

 physiology are occurring in a substance that is capable of all the 

 processes of behavior, including thought and reason. This may aid 

 us to be on our guard against superficial explanations of physiological 

 processes. 



But the chief interest of the subject of the behavior of animals 

 undoubtedly lies, for most, in its relation to the development of 

 psychic behavior, as shown by man. The behavior of the lowest 

 organisms must form a fundamental part of comparative psychology. 



In the special field of the behavior of the lowest organisms the 

 foundations of our knowledge were laid by Verworn, in 1889, in his 

 " Psycho-physiologische Protistenstudien." Binet, in his "Psychic 

 Life of Micro-organisms" (1889), gave a most readable essay on the 

 subject, presenting it frankly from the psychical standpoint. Lukas, 

 in his "Psychologic der niedersten Tiere " (1905), has recently again 

 dealt with the questions of consciousness in lower animals, the treat- 

 ment of objective processes being subsidiary to this matter. 



The present work was designed primarily as an objective descrip- 



