2 go NATURAL SCIENCE. Oct., 



unite Africa with India as the " Indo- African Realm," while he would 

 actually split up South America between two different regions. In 

 these proposals, at least, very little consideration is shown to the 

 much-lauded principle of the equivalence in value of the realms or 

 regions. 



While, however, we insist upon the propriety of retaining the 

 Nearctic Region as a whole, and as one of the primary zoo- 

 geographical divisions of the earth's surface, we are quite disposed to 

 attend to the views of Messrs. Merriam and Allen as to the best mode 

 of subdividing the large area, and to admire the maps and tables in 

 which they have set it forth. Take, for example, Air. Allen's first map 

 of his so-called "Realms" of North America (Bull. A. M. N. H., 

 vol., iv., pi. v.). Here we find a threefold division of the contiment 

 proposed into " Arctic," "Temperate," and "Tropical" Realms. The 

 " Arctic Realm," which consists merely of the land bordering the 

 Polar Ocean and Hudson's Bay and the great peninsula of Greenland, 

 and is "beyond the limit of arboreal vegetation," Mr. Allen unites to 

 the similar arctic portion of the Old World, stating, no doubt quite 

 correctly, that it is really apart of a "homogeneous hyperborean 

 fauna of circumpolar distribution." But looking to the extreme 

 proverty of life in these inclement latitudes, as Mr. Allen well puts it, 

 we think it quite unnecessary to elevate this wretched fraction of the 

 earth's surface to one of its principal constituent life-regions, and 

 must prefer the plan adopted by Sclater and Wallace, of regarding it 

 as a borderland between the Nearctic and Palaearctic Regions. 



We now come to Mr. Allen's " North American Region," 

 which is regarded by the author as a subdivision of the " North 

 Temperate Realm," corresponding in value to what is usually called 

 the " Palaearctic Region " of the Old World, but what Mr. Allen 

 prefers to denominate by the horrible compound term " Eurasia." 

 Mr. Allen's " North American Region" embraces, as will be seen by 

 a glance at the map already referred to, by far the largest portion of 

 that continent. In fact, it embraces the whole, except the extreme 

 arctic portion already referred to, and what Mr. Allen terms "Tropical 

 North America," which consists of the southern end of the peninsula 

 of Florida and a narrow strip of the coast of Mexico on both sides, 

 extending on the Atlantic side up to the Rio Grande and on the Pacific 

 side up to Mazatlan. This " Tropical North America " of Mr. Allen, 

 however, is, in fact, merely the borderland between the Nearctic and 

 Neotropical Regions of Sclater and Wallace, and may be left out of 

 account when a general view of the great life-regions of the world is 

 being taken. We thus see that Mr. Allen's " North American 

 Region " is, for all practical purposes, identical with the Nearctic 

 Region of Sclater and Wallace. Let us now see how Mr. Allen 

 proposes to divide it — according to its Mammal-life. 



" The North American Region," Mr. Allen tells us (op. cit., p. 221), 

 "falls into two sub-regions, namely (1) a 'Cold-Temperate Sub- 



