HIGH SCHOOL ZOOLOGY. 277 



13. The preceding paragraphs have been devoted to the rela- 

 tions existing between different generations of organisms; no 

 less important are tlie relations of the individual or the species 

 to other organisms and to its inanimate surroundings. Ques- 

 tions of this character have been styled Mesological, as dealing 

 relation to the " envi onment," but it will be more convenient 

 to deal separately with the relations to the different elements of 

 the environment, discussing, in the first place, the distribution 

 of animals in space, which we shall find to be explained partly 

 by the past configuration of land and water, and partly by 

 climatic influences. These aspects of Biology are, therefore : 



(5) Gkographical and Climatic. 



We are apt to think of the present distribution of land and 

 water as something unalterable, and of climate as chiefly a nut- 

 ter of latitude and longitude, but a little consideration will show 

 that not only is the latter dependent on the formei', but that 

 both have been, again and again in the history of the earth, sub- 

 jected to change. In respect to the one point, we have merely 

 to compare the mild winbei'S of Britain with those of Labrador, 

 or our own with those of the Riviera. The differences are attri- 

 butable, in the one case, to ocean currents, in the other to our 

 situation in the heart of a great continent. In respect to the 

 other point we can find evidence of profound changes at our own 

 doors. Wherever we find sedimentary rocks there we realize 

 that the land in question has been submerged in the ocean, and 

 often that this has occurred, not only once, but repeatedly in the 

 course of geological time. Ontario, for example, is everywhere 

 undei-laid by sedimentary rocks; those which contain fossils were 

 evidently formed at the bottom of Cambrian or Silurian seas, but 

 the fact that we do not find any trace of the Upper Palaeozoic or 

 Mesozoic or Kainozoic strata covering them indicates that it has 

 been long exposed to the denuding effects of the atmosphere. 

 Again, the superficial deposits which cover these old formations, 



