COAT-COLOR IX HYBRIDS OF PEROMYSCUS EREMICUS. 



43 



TABLE II. 



The.-e show that part of the individual variability in 



coat color --tic. The correlation is, however, rather low, the 



:i nf the 12 figures for " black," " white " and " color " being 

 only o.jX. This indicates that a large proportion of the variabil- 

 ity is due t non-genetic causes. 



Furthermore, these and previous data make it doubtful whether 

 individual differences in the R :G ratio are inherited at all, despite 

 i he f;ii-t that two races may differ rather widely from one another 

 in respect to this character. 



III. MICROSCOPIC HAIR CHARACTERS. 



The junior author has already published a brief account of his 

 lindings with respect to certain hair characters which he has been 

 able to determine quantitatively with the microscope. 1 



Table III. gives the mean values as well as the variability of 

 seven " diameters " in the two parent races and in the F, and F, 

 rat H ns of hybrids. It is evident that the four mean values 

 comprised in the first half of this table are not independently vari- 

 able, -iiu-e their sum is in every case 100. The classification of 

 hair types here included is somewhat arbitrary, as the various 

 cla>M"> intrrgrade completely with one another. The hairs of 

 th.-e animals may be distinguished as banded (classes A, B, C} or 

 as n..n-l,andcd (D). In the latter very dark ("sepia") pigment 

 i. present throughout the entire length of the hair. Tn the former, 

 this dark pigment is interrupted, toward the distal end, by a yellow 

 cross band of varying extent, giving rise to the condition known 

 to geneticists as "agouti." 



r. ' <id. Sci., Oct., ig-3- 



