DISTRIBUTION IN SPACE AND TIME 



CHAPTER LXXV 

 GEOGRAPHICAL DISTRIBUTION 



To consider, and so far as possible explain, the way in which 

 animals are now spread over the surface of the globe is the 

 province of Geographical Distribution, or, as it is sometimes 

 called. Zoogeography. Alfred Russel Wallace, more than any 

 other man, has been the means of placing this branch of Natural 

 History on a really scientific footing, and his invaluable works 

 The Geographical Distribution of Animals and Island Life will 

 long remain standard sources of information on the subject. 

 Smaller books by Heilprin and Beddard (^Geographical and Geo- 

 logical Distribution of Animals, and Zoogeography^ will also 

 be found extremely useful by the student. 



A good deal of information about the parts of the world to 

 which a number of animals belong has already been given in 

 the preceding sections of this work, but certain facts and principles 

 require special mention here, though only elementary treatment 

 is possible, or, it may be, desirable. 



Before the theory of evolution became dominant it was com- 

 monly believed that any particular kind of animal found within 

 a certain area was specially created there, and speculation was 

 deemed out of place, though it was assumed that one sort of 

 climate suited certain species, and another sort of climate other 

 species. But we are not now contented with the statement 

 "This is so", and always ask " Why is this so?" To which 

 question we sometimes get a fairly satisfactory answer. 



Areas of Distribution. — If we consider any kind or species of 

 animal, or any one of the larger groups, such as a genus, a family, 

 an order, or a class, we shall find that it may occupy a limited 



