334 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



the general tendency is to an increase of intensity of colors, 

 as compared with the region west of it, with a development 

 of rufous and fulvous tints. The humidity here is less than 

 that in either of the other regions named, the rain-fall being- 

 only from twenty-four to thirty inches. 



The fourth area Mr. Allen calls the Campestrian Region, 

 and includes the arid plains and deserts of the continent, 

 containing not only the "great plains," so called, but the 

 plains of Utah, Nevada, Western Colorado, New Mexico, Ari- 

 zona, and southwest to Lower California. Here the rain-fall 

 ranges from three inches to twenty, being below fifteen gen- 

 erally. Here a general paleness of color is the distinctive 

 feature., 



The fifth region, called the Columbian Region, begins on 

 the Pacific coast at about the fortieth parallel, and embraces 

 a comparatively narrow belt to Sitka. Its peculiarities are 

 most strongly developed west of the Cascade Range north 

 of 45, and prevail eastward nearly to the main chain of the 

 Rocky Mountains. The average rain-fall is from fifty-five to 

 sixty- five inches. The prevalent tendency in color is to 

 dusky and fuscous rather than rufous tints. 



Other subdivisions of a similar character Mr. Allen thinks 

 may be desirable, and may need to be made hereafter, espe- 

 cially for the southern half of Florida, which is characterized 

 by excessive humidity and a subtropical intensity of color; 

 and it may be necessary to recognize as a distinct district 

 the almost rainless portions of the Campestrian Region. 



Mr. Allen in this communication refers again to the rela- 

 tion between color and humidity previously enunciated by 

 him, remarking that the best mode of expressing it is to say 

 that a decrease of humidity is accompanied by the decrease of 

 intensity of color, this evidently resulting from exposure to 

 the bleaching effect of intense sunlight and a dry, often in- 

 tensely heated, atmosphere. He refers to the condition of 

 melanism as a race characteristic in mammals, and confirms 

 the generalization of Professor Baird that but few mammals 

 possess this in a specific form, and that where it occurs in 

 such groups as the squirrels, the wolves, cats, etc., the indi- 

 vidual must be considered as a melanistic form of some race 

 the normal color of which is different, generally fulvous or 

 rufous. 



