762 THE AMERICAN NATURALIST [Vol. XL VII 



This last excess, however, is not sufficient, in the opinion of 

 the writers, to support any theory of coupling, especially in the 

 absence of significant differences in the other classes. 



The excess of grays may better be explained on the basis of 

 selective elimination of the various recessive animals, for the F 2 

 young could not be graded satisfactorily until nearly four weeks 

 old, and no account was kept before this time. 



A minor error may have occurred in recording the pink-eyed 

 dilute brown yonng. as they resemble closely the intense pink- 

 eyed brown and no breeding test was undertaken. 



To summarize the results of this mating, it is obvious that we 

 are dealing with four clear-cut pairs of Mendelian characters as 

 described by Castle and Little in 1909, among which no coupling 

 or association can be detected. 



C. C. Little 

 J. C. Phillips 



