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THE AMERICAN NATURALIST [Vol. XLIX 



mental and very ancient chief habits, chief adaptations in 

 the hard parts, chief brain features. 



Thus we see that two kinds of characters are employed 

 by Miller throughout, namely: first, characters of pro- 

 portion of form and of degree; second, numerical or 



presence and absence characters. We are struck by the 

 fact that changes in proportion embrace by far the larger 

 part, perhaps nine tenths, of the " characters" enumer- 

 ated by Miller in his systematic descriptions; this is be- 

 cause change of proportion is the chief and most universal 

 phenomenon in the adaptation of mammals to different 

 habits and habitats. Numerical change is hardly less im- 

 portant, bat is less universal and less frequent. 



Similar weight upon the value of characters of propor- 

 tion is seen in the contrast between Miller's definitions of 

 the three genera of dogs, namely: Cams, Alopex, and 

 Vulpes. Here again the vast majority are characters of 

 proportion and of form. 



