Geography of Life. 161 



very limited areas; that the ranges of very dissimilar species are 

 often geographically coincident; and that, as a rule, animals in- 

 habiting contiguous areas are more neai-ly related than those in- 

 habiting remote areas. The recognition of these facts early led 

 to the attempt to divide the surface of the earth, according to its 

 animal life, into ' f aunal ' districts. By the term fauna is meant 

 the sum of the animal life of a region. 



A comparatively meagre supply of information is sufficient to in- 

 dicate the principal faunal subdivisions of a country, but for 

 mapping the exact boundaries of such ai'eas a vastly greater 

 and more precise fund of knowledge is necessary. The way in 

 which such maps are prepared is by collecting all available 

 authentic records of localities where the particular species has been 

 found. This is done by compiling published records, by examin- 

 ing labels of specimens in various museums and private collec- 

 tions, and by work in the field. The data thus brought together 

 are arranged on cards under authors and regions, and are tabula- 

 ted under species. The localities are then indicated by colored 

 spots on an outline map,. the space surrounded by the spots being 

 washed in with a paler tint of the same color. A separate map 

 is devoted to each species. 



Faunal maps are made by combining a large number of species 

 maps. In making such combinations it is found, as a rule, that 

 a considerable percentage of the species maps fall into certain 

 well defined categories whose color patches are essentially coin- 

 cident. The composite resulting from the coordination of these 

 maps may be held to represent the natural faunal areas of a 

 country. Several such areas may be characterized by the com- 

 mon possession of species not found elsewhere, and may be com- 

 bined to constitute a faunal province; several provinces, a region; 

 and several r.egions a realm or primary zoo-geographical division 

 of the earth's surface. 



Having ascertained the actual extent and limitations of the 

 natural faunal districts, it remains to correlate the facts of distri- 

 bution with the facts of physiography. 



My own convictions are that the work of this Society in Geo- 

 graphic Distribution should be restricted to the generalization of 

 results: that we should deal with philosophic deduction rather 

 than with detailed observations and the tedious steps and labori- 

 ous methods by which they are made available. Our aim should 

 be to correlate the distribution of animals and plants with the 



