320 INTRODUCTION TO EVOLUTION 



easy "there would be no fun in science," as one biologist remarked to the 

 author. Clearly the study of species is in no immediate danger of being 

 shorn of "fun." 



For discussion of forces and factors operative in species formation see 

 Chapter 21. 



SUBSPECIES OR GEOGRAPHIC RACES 



We have referred several times to a division of the spe- 

 cies called the subspecies. This smallest unit of classification corresponds to 

 a "race" or "variety." We noted earlier that human races correspond to 

 this category in classification (pp. 250-255). 



FIG. 14.3. Distribution of Peromyscus maniculafus gracilis, with portions of the ranges 

 of neighboring subspecies (geographic races). Dots indicate areas of intergradation. 

 (After Osgood, 1909.) 



Increasingly the practice is followed of adding the name of the subspecies 

 to the scientific name of an animal, thereby converting the name from a 

 binomial to a trinomial. The name applied to the deer mouse inhabiting the 

 mountains of Vermont then becomes Peromyscus mcmiciilatus gracilis. From 

 Fig. 14.3 we note that this subspecies ranges west to the Great Lakes. South 



