188 ECOLOGY 



temporaneous with those of plant life, should invite the investigation 

 of the naturalist. Recently, in the subtle work of Kobelt, animals 

 have been divided into great groups according to their behavior 

 toward the northern winter, as well as according to the cause and 

 forms of their migrations. This immediately brings up questions 

 as to the climatic limits of their distribution, the southern boundary 

 of hibernation, and also of the parallel which separates the winter 

 and summer quarters of the northern eider-duck from those of the 

 Antarctic penguin which cannot fly. With these we may compare 

 the shorter migrations of reindeer and bison. 



The time may not be far distant when the geographical maps of 

 the animal kingdom will emphasize this point of view more strongly 

 than the fact of mere territorial distribution. For its part, botanical 

 geography is occupied in making clear in separate, experimental 

 works, the connection between landscape and formation, and, by 

 imitating geology in the publication of special maps, a long-felt need 

 is being satisfied. Such actual accomplishment counts much in a 

 field where our wish to make clear the cause so far outstrips our 

 ability to do so, for we must not forget that in all other special scien- 

 tific branches the final aim lies before us much more clearly than in 

 ecology, which must be regarded as a place of public assemblage, 

 and it would fare but poorly if it spoke of a final aim before suffi- 

 cient work had been accomplished in the investigation of all vital 

 phenomena. 



The difficulty of stating clearly the reasons for the changing garb 

 of this or that formation is shown by the circumspection used 

 in MacMillan's work upon the Lake of the Woods, where, for the first 

 time in America, this attempt has been made. We find another ex- 

 pression of this difficulty in the rows of figures enumerated in Jac- 

 card's comparison of analogous association in the mats of the Swiss 

 Alps. The vital question here is: Why, when fruits and seeds are so 

 widely disseminated, do the stations of the different species remain 

 so clearly defined within the areas of distribution? Even if we 

 could empirically determine the vital needs of a single species by 

 a consideration of its climatic requirements, area of distribution, 

 and nature of the station, we should still be unable to explain the 

 inherent differences caused by a greater or less degree of acclimat- 

 ization, or the changing association of species and their different 

 bearing in widely separated districts. 



(3) Thus we are led to a consideration of the essence of species, 

 in whose powers of adaptation and variation we find the key to the 

 important problems which weigh upon us when we regard the abund- 

 ant forms of life which take part in the world's work and live in peace 

 and harmony under the favorable and unfavorable influences to 



