xiv EDITOR'S INTRODUCTION 



appeared to me as I read through his manuscript, is an 

 illuminating and original book, the first in which the proper 

 point of view of animal ecology has yet been explicitly stated. 



I will take but one example, and that from Mr. Elton's 

 pet subject, the regulation of animal numbers. 



Men of science do not escape the usual human weakness 

 of regarding facts in a naive and superficial way until some 

 special stimulus to deeper analysis arises. I suppose that 

 most professional biologists think of the relation of carni- 

 vores to herbivores, preyer to preyed-upon, almost wholly 

 in the light of the familiar metaphor of enemies ; and of 

 the relation between the two as being in some real way like 

 a battle. The ecologist, however, speedily arrives at the 

 idea of an optimum density of numbers, which is the most 

 advantageous for the animal species to possess. He then 

 goes on to see by what means the actual density of popula- 

 tion is regulated towards the optimum ; and finds that in 

 the great majority of cases the existence of enemies is a 

 biological necessity to the species, which without them 

 would commit suicide by eating out its food-supply. To 

 have the right " enemies," though it can hardly be spoken 

 of as an adaptation, is at least seen to be a biological 

 advantage. 



Ecology is destined to a great future. The more advanced 

 governments of the world, among which, I am happy to say, our 

 own is coming to be reckoned, are waking up to the fact that the 

 future of plant and animal industry, especially in the tropics, 

 depends upon a proper application of scientific knowledge. 

 Tropical Research Stations, like those at Trinidad and Amani ; 

 special investigations, like that into the mineral salt require- 

 ments of cattle in equatorial Africa ; schemes for promoting 

 the free flow of experience and knowledge from problem to 

 problem and from one part of the world to another, such as 

 were outlined in the report of the Research Committee of the 

 Imperial Conference — all these and more will be needed if 

 man is to assert his predominance in those regions of the 

 globe whose climate gives such an initial advantage to his 

 cold-blooded rivals, the plant pest and, most of all, the insect. 



