Ill 



■ Beginnings of Co-operation 



WITH this chapter I begin the presentation of the 

 evidence for the assertion that there is a general prin- 

 ciple of automatic co-operation which is one of the 

 fundamental biological principles. The simplest ex- 

 pression of this is often found in the beneficial ef- 

 fects of numbers of animals present in a population. 

 Laboratory work of the last two decades still shows 

 that overcrowding is harmful, but it has also uncov- 

 ered a no less real, though somewhat slighter, set of 

 ill effects of undercrowding. 



To be sure, overcrowding always produces ill ef- 

 fects, and these can always be demonstrated at some 

 population density. On the other hand, the ill effects 

 of undercrowding cannot always be shown, though 

 frequently they can. In generalized curves the mat- 

 ter may be summarized thus: Under certain condi- 

 tions (g6) we find the curve running like the dia- 

 gram in Figure 2 A, when height above base line 

 gives the rate of the biological action being meas- 

 ured, and distance to the right shows a steadily in- 



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