610 



THE AMEBIC AX NATURALIST 



[Vol. XLIX 



example, by Plate 2 and Semon 3 are not likely to fall into 

 the shallow dogmatism which dismisses the whole "ac- 

 quired characters" question as once for all settled. And 

 those who have taken the trouble to carefully examine a 

 few trays of specimens, representing the subspecies of 

 some widely ranging bird or mammal, will not so readily 

 resort to a subjective interpretation of the phenomenon 

 of geographic variation. 



I shall give chief attention to-day to the case of a single 

 species of white-footed mouse, or deer-mouse of the genus 

 Peromyscus. According to Osgood, 4 the chief monog- 

 rapher of this genus, the species mcuiieuhrfus comprises 

 about 40 distinguishable geographic races, many of which 

 are so unlike that they would be given full specific rank 

 but for the fact that they intergrade insensibly with one 

 another. 



My own special studies have had to do chiefly with 

 those subspecies of Peromyscus maniculatus which fall 

 within the limits of the state of California. The first 

 investigations have naturally been directed toward a 

 careful examination of mice representing each of these 

 local races, together with a determination, so far as pos- 

 sible, of the meteorological conditions to which they are 

 subjected in nature. A search for correlations of any 

 sort between structural and environmental differences 

 was, of course, early undertaken. 



Mice were collected at four points within the state: 

 Eureka, Berkeley, La Jolla, and in the Mojave Desert 

 near Victorville. At Eureka, Berkeley and Victorville, 

 self-recording instruments (thermographs and hygro- 

 graphs) have been left in charge of assistants for nine 

 to fifteen months, and recording instruments will be in- 

 stalled at La Jolla this summer. It is planned to con- 

 tinue these records for at least two years. The instru- 



2"Selektionsprinzip," vierte Auflage, Engelmann, 1913. 

 1912. g g 



^ 4 "Revision of the Mice of the American Genus Peromyscus," U. S. De- 



