1916] Dice: Land Vertebrates of SoutJuastcrn Washington 341 



Zones or belts of life may be recognized in many regions. How- 

 ever, it is very difficult to liomologize the zones of life which occur in 

 widely separated parts of North America. The division of the conti- 

 nent into a definite unniber of transcontinental life-zones seems to be 

 contrary to a number of the facts of distribution. 



The ecological method of stvidying distribution furnishes valualile 

 information about the relation between organisms and their environ- 

 ments. The use of this metliod in conjunction with the zoogeographi- 

 cal method shoidd lead to results of great value. 



LITERATURE CITED 



Ad.\ms. C. C. 



1908. The ecologieal siu-i-essioii of binls. Auk, 25, 109-1.5:1. 

 Al.LEX, .J. A. 



1892. The geographical ilistriliution of North Anieriran mammals. Bull. 

 Amer. Mus. Nat. Hist., 4, 199-2-14, 4 maps. 

 BiGELOW, F. H. 



1908. The daily normal temperature and the daily normal precipitation of 

 the United States. LI. S. Dept. Agr., Weather Bureau, Bull. R, 

 186 pp. 

 G.\DOW, H.\xs. 



191.3. The wanderings of animals (University Press, Cambridge), viii + 150 

 pp., 17 maps. 

 G.\TES, Fr.\nk C. 



1911. Summer bird life in the vicinity of Havana, Illinois, in its relation to 

 the prominent [dant associations. Wilson Bull., 23, 1-27. 

 Grixxell, .7. 



1902. Cheekdist of California birds. Cooper Ornith. Club, Pacific Coast 



Avifauna, 3, 98 pp., 2 col. pis. 

 1914. An account of the mammals and birds of the lower Colorado Valley 

 with especial reference to the distributional problems presented. 

 Univ. Calif. Publ. Zool., 12, .51-294, pis. .3-l.S, 9 figs. 



GRIXXELL. J., .\ND SW.4RTH. H. S. 



1913. An account of the birds and mammals of the San .Jacinto area of 



southern California, with remarks upon the behavior of geo- 

 graphic races on the margins of their habitats. Univ. Calif. Publ. 

 Zool., 10, 197-406, pis. 6-10, .3 figs. 

 JACK.SOX, H.\RTLEY H. T. 



1914. The land vertelirates of Ridgway Bog, Wisconsin: their ecological 



succession and source of ingression. Bull. Wise. Nat. Hist. Soc, 12, 

 4-54, 9 figs. 

 Kexxedy, C. L. 



1914. The effects of irrigation on bird life in the Yakima Valley, Wash- 

 ington. Condor, 16, 250-255. 

 Lydekker, R. 



1896. Geographical history of mammals. (University Press, Cambridge), 

 xii -I- 400 pp., 82 figs., 1 map. 



