AGGREGATIONS OF HIGHER ANIMALS 107 



on the growth of individuals and the increase of 

 populations, we strike the problem of the optimal 

 size of a population in nature. This is an exceedingly 

 difficult question on which to obtain data. Suppose, 

 therefore, that we simplify it by asking what minimal 

 numbers are necessary if a species is to maintain itself 

 in nature? 



This inquiry is a direct attempt to find under nat- 

 ural conditions the application of the statement by 

 Professor Pearl that "this whole matter of influence 

 of density of population in all senses, upon biological 

 phenomena, deserves a great deal more attention 

 than it has had. The indications all are that it is the 

 most important and significant element in the bio- 

 logical, as distinguished from the physical, environ- 

 ment of organisms." 



Over and over again in the last half-dozen years 

 I have asked field naturalists, students of birds, wild- 

 life managers, anyone and everyone who might have 

 had experience in that direction, how few members 

 of a given species could maintain themselves in a 

 given situation. Always until this last summer I have 

 found that, stripped of extra verbiage behind which 

 they might hide their ignorance, the real answer was 

 that they did not know. 



And then I had two pieces of luck; I found a man 

 and a scientific paper. My friend. Professor Phillips 



