ANIMALS AND THEIR ENVIRON- 

 MENTS. 



THERE are few studies in natural history of greater interest 

 and of more captivating nature than that of investigating 

 the relations which exist between living beings and their 

 surroundings. How are animals and plants affected by 

 their environments ? in what degree and in what fashion do 

 external influences modify habits ? and how do varying 

 surroundings alter the structure of living beings ? such are 

 the questions which the biologist of to-day proposes, and 

 such are a few of the problems to the solution of which the 

 energies of the modern naturalist are directed. A backward 

 glance of by no means very extended kind at the natural 

 history of the past, will suffice to show the wide and sweep- 

 ing changes in opinion which the lapse of a few years has 

 wrought regarding the relation between animals and plants 

 and the world they live in. Of old, naturalists paid little 

 heed to such a relationship, and to the effect which a change 

 in climate, food, or habitat induced in living organisms. 

 The living being, able no doubt in virtue of its vital powers 

 to override many of the outward and physical forces which 

 operate so powerfully on the non-living part of the universe, 

 was apt to be regarded as almost wholly independent of 

 external conditions. " In the world, but not of it," is an 

 expression which may be said to summarise the tendency of 

 biological thought in the past with reference to the relation- 

 ship existing between animals and plants, and the outward 



