HISTORY AND NATURAL HISTORY 31 



preceding and following 1920 we, who in Aus- 

 tralia, (107) in France (26) and in the United 

 States (2) were engaged in these studies, continued 

 unaware of each other's work. Relatively soon, how- 

 ever, since biological world literature is today widely 

 and promptly circulated, all such work, even that 

 in Russia, (53) became generally known. It is these 

 general experiments on population growth, on mass 

 physiology and on animal aggregations, that are now 

 the important aspect of the field of animal co- 

 operation. 



I have briefly traced here the history of the idea 

 of innate co-operation. One reason for the slowness 

 of accepting that idea is the obvious fact that co- 

 operation is not always plain to the eye, and that 

 competition in its most non-co-operative form, in 

 which no social values are apparent, can readily be 

 observed. With certain exceptions to be nientioned 

 soon, it has seemed that, social species aside, crowd- 

 ing, the simplest start toward social life which is 

 easily apparent and a condition of nearly all society, 

 was harmful alike to the individual and to the race. 

 It has been known from experimental evidence 

 since 1854 (62) that crowded animals may not grow 

 at all, or, at any rate, gi-ow less rapidly than their 

 uncrowded brothers and sisters. And under many 

 conditions crowded animals not only do not grow. 



