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University of Calif orma Publications in Zoology [Vol. 21 



appearance, as is the case with stephensi. From these facts it is 

 obvious that insularity alone can not be invoked as an explanation 

 of the development of the different forms. It should be noted in this 

 connection that while discontinuous distribution of a subspecies occurs 



CROSS-SECTIONAL PROFILES OF CALIFORNIA 



a. Cape ViicE 



ough Lassen Peak 



[j San Francisco through Mount Lyell 



C Monterey through Mount Whitne 



Q San Pedro through San Jacinto Peak 



Fig. G. Four cross-sectional profiles of California. The shaded areas indicate 

 the altitudinal distribution in summer of the subspecies of fox sparrow occurring 

 within the state at that season. 



a. Brevicauda on the Yolla Bolly Mountains; mariposae on Lassen Peak; 

 fulva on the Warner Mountains. 



h. Mariposae on the Sierra Nevada west of Mount Lyell; monoensis in the 

 Mono Lake region on the east slope of the Sierra Nevada; canesoens on the White 

 Mountains. 



c. Stephensi on Mount Piiios and on the Sierra Nevada west of Mount Whitney; 

 mariposae on the Sierra Nevada east of Mount Whitney. 



d. Stephensi on San Jacinto Peak. 



through the interpolation of unsuitable territory, it never takes place 

 through the interpolation of another race of fox sparrow. Regarding 

 each isolated colony as a separate race (as in a sense they are, of 

 course, though we can not always distinguish between them), and it 

 is evident that anv one line of variation extends continuously in a 



