No. 615] INHERITANCE IN PEROMYSCUS 



193 



small clusters of white-tipped hairs near the anterior in- 

 sertions of the ears. But even this feature is not evident 

 in all individuals. 6 * 



Many species of Peromyscus, including the maniadatus 

 series, have what is known as a "bicolored" tail. The 

 hairs throughout a longitudinal stripe of varying width, 

 upon the dorsal surface of this member are dark brown or 

 black, while those of the ventral side are white. Now a 

 casual inspection serves to show that this caudal stripe 

 is broader and darker in the Eureka mice than in the 

 desert ones, while a more careful comparison shows that 

 the " gamheli" individuals are, on the whole, intermediate 

 between the other two. 



Fortunately, the breadth of this stripe is a character 

 which may be subjected to fairly accurate measurement. 

 It is my practice to slit the skin of the tail along the mid- 

 ventral line, strip it off, and press the inner, damp sur- 

 face firmly against a strip of black cardboard. The total 

 width of this skin (= circumference of tail) is then taken 

 at the mid-point of its length ; likewise the width of the 

 tail stripe. The ratio between the two readings is next 

 determined, the width of the dorsal stripe being expressed 

 as a percentage of the circumference of the tail. The fol- 

 lowing are the figures for the four races and the two 

 sexes, the figure in parenthesis representing the number 

 of animals measured: 7 



TABLE I 



rubidus, J (69) 42.51 ± 0.45 



rubidus, $ (50) 41.96 ± 0.53 



Berkeley gambeli, £ (24) 36.08 ± 0.80 



Berkeley gambeli, $ (28) 35.50 ± 0.56 



La Jolla gambeli, <$ (85) 32.08 ± 0.33 



