COLOR MUTATIONS IN MICE OF PEROMYSCUS 311 



to inadequate numbers. Other types of matings give no grounds 

 for expecting the number of albinos to be deficient here. 



The really important tests, as stated in another paper, have 

 been made, 1) by mating 'extracted' albinos of the F2 generation 

 with 'pure' pallids (i.e., those known to be free from the factor 

 for albinism) ; 2) by mating extracted pallids with pure albinos, 

 and, 3) by mating extracted albinos with extracted pallids. 

 There were likewise a number of matings in which the pedigrees 

 were somewhat less simple than here indicated. 



Eighteen F2 mice were involved in these tests. The total 

 number of their offspring was 135, the number per pair rang- 

 ing from three to twenty-six. Not all of these parents, taken 

 singly, have thus far given birth to a sufficient number of young 

 to prove their genetic composition with any certainty. But the 

 cumulative testimony of all of these matings is overwhelming. 

 Not a single pallid mouse and only two albinos have appeared 

 among the 135 young which have thus far been born. Had there 

 been a normal proportion of 'carriers' among the parents, these 

 matings should have jdelded fifty-five of the recessive types. 

 That all of the offspring with two exceptions (these being sibs) 

 were of the wild type is evidence of a high degree of linkage (in 

 this case 'repulsion') between the albino and the pallid factors. 



SUMMARY AND CONCLUSIONS 



1. Three distinct color 'mutations' have been described, which 

 first appeared in captive stock of the commonest species of 

 California deer-mouse, Peromyscus maniculatus. 



2. Two of these, the 'yellow' and albino varieties appeared in 

 cultures of P. m. gambeli, originally trapped in the vicinity of 

 La Jolla. The third, or 'pallid' variety, first appeared in the F2 

 generation of a cross between the subspecies rubidus and 

 sonoriensis. 



3. The albino and pallid varieties arose but a single time each 

 in our cultures. Of the 'yellows' there were six independent 

 outcroppings. 



4. At least two of these independent yellow strains differed 

 from one another in the mean color tone displayed, and this 



