JAN 11 1900 
Natural Science 
A Monthly Review of Scientific Progress 
NovEMBER 1899 



Nee oe ab Ce) NNER NTS. 
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, eg. 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 Holl, 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—wnart. sc.—voL. xv. No. 93. 309 
