Manchester Memoirs, Vol. Ixvi. (1921) 11 



subsist upon them. What is the result? The numbers are 

 raised above the normal, and when the normal food supply 

 returns, famine follows as surely as when the supply w^as 

 short ; there are too many mouths to be filled. Thus taking 

 an average of years the necessary average is maintained, and 

 this is Nature's Balance. 



It is fair to say that there cannot be in any civilised, indeed 

 in any country populated by man, a real natural balance ; Man 

 is the great disturber of Nature. But in a country like 

 Britain, where civilisation has been working for the ends of 

 Man for ages, there is what we may call a human or artificial 

 natural balance ; a point at which, under the present artificial 

 system, the inter-relation of plants and animals, cultivated 

 and domestic as well as wild, remains more or less constant. 

 It is our duty to maintain that present day balance so far as 

 we can consistently with our actual requirements, for if we 

 fail mankind as well as the lower animals will suffer. It is 

 with this end that economic zoology and botany should be 

 studied. 



The increase beyond the normal proportions of any species 

 of bird, due to protection which has not taken into considera- 

 tion consequences, may be a tragedy. It may, probably will, 

 affect our life interests ; it certainly will have influence upon 

 the relative numbers of other forms. Need I mention as 

 problems of the day the extraordinary increase since 1880 of 

 the black-headed gull and the starling, two species wholly 

 -^'rJuable in their proper proportions, but threatening other 

 forms, actively or passively, now that they have become so 

 numerous. 



May I here mention that it was after I had thought out 

 and actually written most of this paper that I read Dr. 

 Ritchie's fascinating study in faunal evolution, '' The Influ- 

 ence of Man on Animal Life in Scotland." My line of 

 thought is practically the same as his, and, though we had 

 arrived at the same conclusions independently, I am indebted 

 to him for several useful suggestions. I know of no better 

 exposition of the need for sensible and well considered protec- 

 tion than is supplied by this book. 



Dr. Ritchie divides his subject into two parts — deliberate 

 and indirect interference with animal life. In the first he 

 groups domestication, intentional destruction of animals for 

 various reasons, protection of animals for other reasons, and 

 the introduction of new forms. In the second he deals with 

 changes in natural environment and the influence on animals, 

 cultivation, civilisation, and the accidental or unintentional 



