72 BULLETIN 56, UNITED STATES NATIONAL MUSEUM. 



For an early account of the life zones or belts of plant and animal 

 life in the mountainous portion of Arizona between the Gila and 

 Colorado rivers, including San Francisco Mountain, attention is 

 called to the writer's essay " on the ornithology of the alpine portions 

 of the area under consideration, based on field work extending from 

 1884 to 1888, in which 100 species of birds, excluding intruders from 

 the upper Austral Zone, are given as representing the avifauna of 

 the Transition and Boreal zones. 



It will be observed, on perusal of the literature relating to life 

 areas, cited above, that, accepting Dr. C. Hart Merriam's latest conclu- 

 sions, which practically differ from those of Allen and other natural- 

 ists only in nomenclature, that we have returned to the teaching of 

 our early physical geographies; that there are but three primary 

 biologic and climatic regions the world around. Tropical, Arctic (or 

 Antarctic), and Austral (or Temperate) — hot, cold, and interme- 

 diate — and that these are based entirely on temperature. 



Doctor Merriam's latest work, in extending the long-recognized 

 eastern life zones across the continent to the Pacific, is theoretically 

 logical for three reasons: (1) Because these six subdivisions of the 

 Austral and Boreal regions are based on practical work in the East, 

 where they were originally established by the older naturalists — 

 Allen, Verrill, and many others — for convenience of classification 

 of associated groups of animals and plants, and in the West they 

 could be utilized as convenient, even if not natural, subdivisions of 

 the primary regions; (2) because practical field work in the West, 

 largely conducted under the guidance of Doctor Merriam himself, 

 has proved that these zones are just as natural and just as conven- 

 ient in the West as they are in the East; arid (3) that the same 

 zones exist on all sides of the earth and on both sides of the eqiiator, 

 and might as well have been continued at once around the Old World 

 and the New, in which case appropriate names could have been ap- 

 plied to each. While there is nothing new in the theory of " life 

 areas " and " temperature control," their general systematic appli- 

 cation to the problems dealing with the natural distribution of plants 

 and animals on the earth, and with their artificial introduction into 

 new areas for the uses of man is a natter of importance. Doctor 

 Merriam has defined with admirable clearness a sufficient number of 

 sections of circumpolar life zones, covering the North American 

 continent, for present use; and it is desirable that his system of 

 nomenclature be generally adopted in dealing with them, on account 

 of its popularity and of the large amount of work already based 

 upon it. The correlation of the life zones of the Old World to those 

 of the New has already been taken up by field naturalists employed 

 by the United States National Museum. 



a Auk, VII, Jamiary to July, 1890, pp. 45-55 and 251-264. 



