Abstracted by Francis B. Sumner and Henry H. Collins, authors 

 Scripps Institution for Biological Research, La Jolla, California. 



Further studies of color mutations in mice of the genus 



Peromyscus. 



Three recessive color mutations (already discussed in previous 

 papers) are more fully described and the behavior of these in 

 hybridization considered. The mutant races are characterized 

 as 'yellow,' 'pallid,' and true albino. The first and last of these 

 appeared in stock belonging to pure subspecies, while the other 

 appeared after a subspecific cross. The three depiend upon 

 changes in distinct genetic factors. Any two give the wild type 

 in the Fi generation, with the wild type and both mutants in 

 the F2. In respect to relative numbers, these last follow dihybrid 

 ratios, at least in some cases. As regards the yellows, however, 

 irregularities are found, both in respect to the proportions which 

 emerge from dihybrid crosses and the tendency of certain yellows 

 to produce offspring which intergrade with the wild type. The 

 causes of these irregularities have not yet been cleared up. Also, 

 at least two distinct strains of yellows have been encountered, 

 which differ from one another in respect to their mean color 

 values. The differences between these are hereditary and crosses 

 between the two give an intermediate condition. The pelage 

 of these various mutant races, as well as individuals of the wild 

 type, has been subjected to color analysis by means of the Hess- 

 Ives tint-photometer. This has rendered possible a fairly exact 

 quantitative expression of the various color differences concerned. 

 Three colored plates of skins are included. 



