180 



THE AMEBIC AX XA1TRALIST 



[Vol. LII 



II. The Distbibution of Subspecies 

 The term subspecies, as here employed, is nearly equiva- 

 lent to geographic race. These subdivisions of a species 

 occupy different, though often contiguous areas. When 

 contiguous, they are said to intergrade completely with 

 one another along the boundaries of their respective 

 territories; and in any case, their ranges of variation 

 overlap broadly. It is this fact, indeed, which leads to 

 their being ranked as subspecies, rather than as distinct 

 species, since the differences between some of the more 

 j widely separated among them would be quite sufficient 

 [to give them specific rank were there no connecting forms. 



In such reports as those of Osgood on Peromyscui 

 (1909), Nelson on the rabbits (1909), or Goldman on Neo- 

 toma, (1910), the geographic ranges of certain species are 

 seen to be divided up into what look like quite arbitrary 

 subdivisions, corresponding to the ranges of the compo- 

 nent subspecies. The boundaries between these subdi- 

 visions oftentimes follow certain natural barriers, but in 

 some instances this does not appear to be true. And, in 

 any case, it is doubtful whether any geographic barrier, 

 save a continuous body of water or a lofty and unbroken 

 range of mountains could prevent the free diffusion of such 

 rodents. These minor areas, furthermore, frequently com- 

 prise territory having a very wide diversity of physical 

 conditions. For example, Peromyscus maniculatus gam- 

 beli is represented as ranging from the foggy coastal area 

 of central and southern California across the hot, semi- 

 arid San Joaquin Valley to the snowy heights of the 

 Sierra Nevada. And in latitude, its range is said to ex- 

 tend roughly from the 31st to the 48th parallel. 

 According to Osgood, 



Specimens from Monterey, the type locality, are absolutely identical 

 with those from San Diego and the northeast coast of Lower California, 

 and the intervening region is inhabited by exactly the same form. 

 These, moreover, are like specimens from . . . the west slope of the 

 Sierra (p. 69). 



We might well be puzzled to discover any common ele- 



