Vol. xli.] 42 



conditions (/. e., wliere species have evolved together) the 

 preyer would never exterminate his prey, but it" we introduce 

 an alien preyer the case mioht conceivably be different 

 and that while the balance ot" Nature is being readjusted, 

 the undesirable species might be exterminated. In theory 

 this is possible, in practice we have never known it to 

 happen. Either the introduced species will oust entirely 

 or partially the natural enemies of the noxious species so that 

 the next result is unaltered, or he will be unable to adapt 

 himself to his new surroundings, and so die out, or he 

 will find some prey easier to capture than the species we 

 wish exterminated and turn his attention to them, leaving 

 our noxious species untouched. Hence the introduction of 

 an alien species is most strongly to be deprecated, and I have 

 not known o£ a single successful introduction, while the 

 lesson of the Sparrow in America, the Mongoose in the 

 West Indies, and the Rabbit in Australia are surely sufficient 

 in themselves to condemn the practice. 



The balance of Nature is extremely complex, and in intro- 

 ducing alien species we can never tell what effect it will have, 

 and if the results should be disastrous it will then probably 

 be too late to remedy the evil. Man is by means omnipotent 

 over Nature, he is powerless to exterminate directly any 

 species — witness the abundance of many species of Sparrows, 

 Rats, Mice, Wasps, Fleas, and many other insects which 

 increase and multiply even though in close contact with us 

 in our daily life. 



Protection Laws are, however, necessary to prevent the 

 absolute local extermination of species that in thickly 

 populated countries have become extremely rare through 

 other causes only indirectly due to man — the Goldfinch, for 

 instance, is much scarcer than it used to be, owing to the 

 better cultivation of the land and the fewer areas of waste 

 land containing its favourite food. It may be argued that 

 since stricter watch has been kept on bird-catchers it has 

 increased, and that may be so, but the days when one bird- 

 catcher used to catch as many as 1154 dozens in a year had 



