Natural Science^ 



A Monthly Review of Scientific Progress 



November 1899 



NOTES AND COMMENTS. 



Disturbing the Balance of Nature. 



No one who has appreciated the reality of the struggle for existence is 

 likely to be in haste to disturb the balance of nature either by 

 eliminating old-established inhabitants from an area in which they have 

 settled, or by artificially introducing new-comers. But where the 

 scientific man would try at least to act warily, the practical man is 

 impetuous, and many illustrations of nemesis, e.g. the rabbits in 

 Australia, are well-known. Nor has the scientific man always restrained 

 himself from eliminating and introducing, and though the results have 

 sometimes been beneficial, it has not always been so. 



Apart from its practical importance, man's agency as an eliminator 

 and distributor is of much theoretical interest, for the results serve to 

 vivify our realisation of the struggle for existence, and often to impress 

 us with the plasticity of adaptation which even highly specialised forms 

 have still in reserve. It may be profitable, therefore, to bring together 

 a few illustrations. 



In 1850 the first house sparrows of Europe were introduced into 

 America, and from that time to 1870, according to Merriam and 

 Barrows (U.S. Department of Agriculture, Division of Economic 

 Ornithology and Mammalogy, Bulletin I. 1889), upwards of 1500 are 

 said to have been imported. They found themselves in conditions 

 where the operation of natural selection was, in great measure, 

 suspended as far as they were concerned. Commenting on this, Prof. 

 Hermon C. Bumpus says {Biol. Lectures Woods Soil, Boston, 1898, 

 pp. 1-15): — " They have found abundant food, convenient and safe 

 nesting-places, practically no natural enemies, and unrivalled means of 

 dispersal. Aside from an early and brief period of fostering care, 

 they have been left to shift for themselves ; natural agencies have 

 since been at work, and in the relatively short space of forty years a 

 continent has been not merely invaded, but inundated by an animal 

 which, in its native habitat, has been fairly subservient to the regula- 

 tions imposed by competing life." They may here and there recognise 



21 NAT. SC. VOL. XV. NO. 93. 309 





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