No. 580] ORIGIN OF SINGLE CHARACTERS 



19<) 



Presence and absence characters, 

 e. g., numbers of teeth, of cusps 

 on the teeth, of vertebrae, of 

 toes, of pads on the feet, of 

 mamma?. Meristic or segmental 



partly expressed in formulae. 



Changs of form in the length, 

 breadth and height of parts. 



parts. Such characters as may 

 partly be expressed in indices 



Proportional characters may through prolonged reduc- 

 tion lead into numerical characters. Thus the reduction 

 in length of one of the toes may precede the loss of the 

 toe, which is a numerical change. Yet we shall see that 

 somewhat different principles prevail in the origins of 

 certain numerical characters as contrasted with the 

 origins of proportional characters. 



1. Use of Numerical and Proportional "Characters" in 

 Classification of Mammals 

 In our attempt to analyze " characters" as they are re- 

 vealed to the systematic and field zoologist let us take as 

 two examples, first, " The Catalogue of the Mammals of 

 Western Europe" by Gerrit S. Miller, 9 and, second, the 

 "Revision of the Mice of the genus Peromyscus," by 

 Wilfred H. Osgood. It is of the utmost importance that 

 mammalogists, whether working among living or fossil 

 forms, should use similar methods of description and defi- 

 nition of characters, and we especially welcome in the 

 monumental work of Miller the fact that the definitions 

 and the keys are chiefly upon the hard parts which are 

 also available to the paleontologist. We select as typical 

 his treatment of the Order Carnivora and of the Family 

 and Genera of the wolves and foxes, which he distin- 



