COAT-COLOR IN HYBRIDS OF PEROMYSCUS EREMICUS. 45 



Of the banded hairs, class A includes those which are slender 

 throughout (they are also relatively short), while class B includes 

 those which broaden out through the region of the subterminal 

 band. Class C comprises hairs which are intermediate between 

 B and D, and for which the creation of a separate class has 

 seemed justifiable. 



In the lower section of Table III. will be found the "total 

 length." to^ftlicT with the lengths of the two distal subdivisions 

 of the hair, all of these values being based upon micrometer meas- 

 urements. The first of these figures represents the length of the 

 longest hairs in each sample, the two last are means derived from 

 the measurement of ten " A " hairs in each sample. 



It will be noted that the proportion of D (all-black) hairs is 

 ; eater in the darker race (fratercuhis) than in the paler 

 rare (ereniicus) , but that the chief difference between the two lies 

 in the greater proportion of B (broad " agouti ") hairs in eremi- 

 cus. This is doubtless partly responsible for the paler and more 

 highly colored pelage of the latter subspecies. As regards the 

 ^lrn<lrr. banded hairs of the A class, the relations are reversed, 

 the darker race (fratcrculus) having proportionately more than 

 the paler race. Owing to the relative shortness and slight width 

 of t' irs. they contribute, however, much less to general color 



effect of the pelage. 



F.> .< appears to have slightly longer hairs than fratcrculus, 



luit the fact of chief interest revealed by the linear measurements 

 is the . rably greater mean length of the " agouti " band in 



this race. The figures here given are based upon hairs of the 

 "A " class, but similar relations would have held in the case of 

 the ' hairs, 1 and this difference in the length of the yellow 



subterminal band is without doubt another of the important fac- 

 tors which are responsible for the color differences between these 

 two races. 



Further scrutiny of the table reveals the fact that in the case of 

 six out of seven of these " characters," the mean values of both 

 hybrid generations are intermediate between the values for the 

 pan-in races. The single exception relates to the percentage of D 



i It was less practicable to employ these in the present measurements. 



