AM HALS A^D THEIR ESVIEONMEJS T TS. 



231 



ANIMALS AND THEIR ENVIRONMENTS. 



By ANDREW WILSON. 



THERE are few studies in natural history of 

 greater interest and of more captivating na- 

 ture than that of investigating the relations which 

 exist between living beings and their surround- 

 ings. 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 suf- 

 fice to show the wide and sweeping 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 liv- 

 ing 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 summarize the 

 tendency of biological thought in the past with 

 reference to the relationship existing between 

 animals and plants, and the outward conditions of 

 their life. Nor need we look far a-field to dis- 

 cover the reasons which induced naturalists to 

 credit the living part of Nature with a fixity 

 which nowhere held sway in the inorganic world. 

 The tendency of biological opinion in the past 

 was to regard the forms of animal and plant life 

 as fixed quantities, which varied now and then, 

 no doubt, but which on the whole preserved, as 

 far as observation could detect, a perfect and 

 stable uniformity of form and function. With 

 the extreme prevalence of the idea of the fixity 

 of animal and plant species, the doctrine of " spe- 

 cial creation" had, unquestionably, much to do. 

 A glance at a natural history text-book of some 

 twenty years back or so will serve to show clearly 

 and unmistakably that the former idea of a " spe- 

 cies " of animals or plants was based on the con- 

 tinued and unvarying likeness of a number of 



living beings to each other. Buffon's definition 

 of a " species," for example, shows that he re- 

 garded it as " a constant succession of individu- 

 als similar to and capable of reproducing each 

 other." And another authority, Miiller, defines 

 species to be " a living form, represented by in- 

 dividual beings, which reappears in the product 

 of generation with certain invariable characters, 

 and is constantly reproduced by the generative 

 act of similar individuals." Thus the various 

 species of animals and plants were regarded as 

 essentially immutable in their nature, and as con- 

 tinuing permanently in the likeness which they 

 had inherited from the creative fiat in the begin- 

 ning of this world's order. 



But, meanwhile, ideas of a widely different 

 nature regarding the nature of living beings had 

 been slowly asserting themselves, and had their 

 part outcome in the work of Lamarck, who clear- 

 ly recognized the effects of use and disuse and of 

 habit on the frames of animals, in producing modi- 

 fications of their form and structure. Similar or 

 analogous thoughts were beginning to influence 

 the sister science of geology. The writings of 

 geologists who, like Hutton, Playfair, and Lyell, 

 advocated the doctrine of Uniformity in opposi- 

 tion to that of an ill-defined Catastrophism, had 

 a powerful effect in suggesting that the order of 

 Nature, both in its living and non-living aspects, 

 might be different from the old ideas founded on 

 the stability and unalterable nature of the uni- 

 verse — ideas these, which, like many other 

 thoughts even of modern kind, had come to be 

 regarded with respect from the fact of their ven- 

 erable age, if from no other or more satisfactory 

 cause. From Goethe himself, as a master-mind, 

 came abundant suggestions tending to enforce 

 the opinion that living beings were to a large 

 extent amenable to outward causes, and influ- 

 enced by external agencies. In his "Metamor- 

 phosis of Animals," the poet-philosopher, with 

 that imaginative force so characteristic of his 

 whole nature, thus enunciates the opinion that 

 the outer world, the animal constitution and the 

 manner of it3 life, together influence in a most 

 decided fashion the whole existence of the living 

 being: 



"All members develop themselves according to eter- 

 nal laws, 



