340 BEHAVIOR OF THE LOWER ORGANISMS 



of as behavior by "trial and error." In connection with this method of 

 behavior, three questions arise, which are fundamental for the theory 

 of regulation. The first is as follows : How is it determined what shall 

 cause the changes in behavior resulting in new conditions? Why does 

 the organism change its behavior under certain conditions, not under 

 others? Second, how does it happen that such movements are pro- 

 duced as result in more favorable conditions? Third, how is the more 

 favorable condition selected? What it this selection and what does it 

 imply? 



Our first and third questions may indeed be condensed into one, 

 which involves the essence of regulation. Why does the organism 

 choose certain conditions and reject others? This selection of the fa- 

 vorable conditions and rejection of the unfavorable ones presented by 

 the movements is perhaps the fundamental point in regulation. 



It is often maintained that this selection is precisely personal or con- 

 scious choice, and that the behavior cannot be explained without this 

 factor. Personal choice it evidently is, and in man it is often conscious 

 choice ; whether it is conscious in other animals we do not know. But 

 in any case this does not remove it from the necessity for analysis. 

 Whether conscious or unconscious, choice must be determined in some 

 way, and it is the province of science to inquire as to how this determina- 

 tion occurs. To say that rejection is due to pain, acceptance to pleasure 

 or to other conscious states, does not help us, for we are then forced to 

 inquire why pain occurs under certain circumstances, pleasure under 

 others. Surely this is not a mere haphazard matter. There must be 

 some difference in the conditions to induce these differences in the con- 

 scious states (if they exist), and at the same time to determine the 

 differences in behavior. We are therefore thrown back upon the objec- 

 tive processes occurring. Why are certain conditions accepted, others 

 rejected ? 



Let us examine one or two of the simplest cases of such regulatory 

 selection. The green infusorian Paramecium bursaria requires oxygen 

 for its metabolic processes. While swimming about it comes to a region 

 where oxygen is lacking. Thereupon it changes its behavior, turns away, 

 and goes in some other direction. The white Paramecium caudatum 

 does the same, and so also do many bacteria ; they likewise require oxy- 

 gen for their metabolic processes. All reject a region without oxygen. 

 The green Paramecium bursaria comes to a dark region. The water 

 contains plenty of oxygen, hence the metabolic processes are proceeding 

 uninterruptedly, and passing into darkness does not interfere with them. 

 The animal does not change its behavior, but enters the dark region 

 without hesitation. Later the oxygen in the water has become nearly 



