Detlefsen and Holbrook: Skunk Breeding 



253 



priori, that this view of the relation 

 between the mutant genes was the 

 more logical because the color gene in 

 experimental rodents has shown a 

 greater mutability than any other gene. 

 If, on the other hand, they represent 

 mutations in different genes, either 

 linked or independent, then a mating 

 between two different mutations would 

 give the wild type, exactly like the 

 case of the pink-eyed yellow rat mated 

 to the dark red-eyed yellow rat. We 

 had hoped to mate (fg (pure albino) 

 with 9 c, (almost complete albino) or 

 at least to mate these two types of 

 mutant together as they appeared in 

 subsequent segregating generations, in 

 order to settle this question, but the 

 opportunity was lacking. However, we 

 found it possible to make two matings 

 which, while not ideal, threw some 

 light on the problem. Females 4 and 

 5 were mated to male mutant g, each 

 female giving one litter in the spring 

 of 1918. Now ?4 and $5 were Fi 

 offspring from a cross between 9 c 

 (white with pink eyes and a small rim 

 of pigment around the inner and outer 

 margins of the iris) and a wild type 

 male. If this mutation is a condition 

 of the wild color factor C, then we may 

 represent it by C\ and 9 94 and 5 

 would have the genetic constitution 

 CCk It follows that if cfg (pure 

 albinic type) is also a member of the 

 triple allelomorphic series, we may 

 assign to him the formula cc, where c 

 stands for either a complete loss of the 

 color factor C, or at least a lower grade 

 or level of this factor than Ck A 

 mating of mutant cfg to either 9 4 or 

 9 5 would then be in Mendelian ter- 

 minology as follows : 

 94 X d'g = CO X cc 



C + C' = gametes of 94 

 c+c = " " o^g 



Cc -fC'c = zygotes of hy- 

 brids 

 Our previous matings (animals No. 37 

 to No. 48 on p. 252) have shown that Cc 

 is wild type. Oc would be an individual 

 heterozygous for complete albinism, c, 

 and the very low grade of color, O; and 

 it should be in all probability albinotic 



All of these young 



were 



wild type, i.e., black 



with short stripes 



like O, (white with little pigment in 

 the iris). These two forms should occur 

 in equal numbers. However our ex- 

 perimental results, as far as they go 

 are not in accord with such a hypo- 

 thesis, for the matings of cfg to 9 94 

 and 5 gave nine wild black young as 

 follows : 

 d'gx 94 cf21] ■ 



9 22'> 



9 23 

 d'gx 95 924' 



925 



9 26 



9 27 



6^28 



929J 



In other words, we observed nine wild 

 type when our hypothesis calls for 

 equal numbers of the wild type and the 

 albinotic. Such an event is not abso- 

 lutely impossible even if our hypothesis 

 is correct, but it is decidedly improb- 

 able. It should occur only once in 

 every 512 litters of nine. Stated 

 differently, we should expect at least 

 one albinotic individual in a litter of 

 nine, in 511 out of every 512 such 

 litters, or in 99.8% of such cases 

 (obviously the first n — r+\ terms of 

 {p-\-qY where ^ = 5 = 3^, « = size 

 of litter=9, and r=\ or the single 

 albinotic individual which is necessary 

 to prove, and which by its very occur- 

 rence would prove the correctness of 

 our hypothesis). All that we can say 

 under these conditions is that this 

 hypothesis may be correct, but the 

 evidence does not point that way. 

 Therefore these two types may be 

 mutations in different genes. 



Two other albinos were in our pos- 

 session for some time, but gave no 

 progeny. Female mutant d, a pure 

 typical albino with pink eyes, was kept 

 with a vigorous male during at least 

 two breeding seasons but failed to give 

 young. Male mutant, m, also a pure 

 albino with pink eyes but belonging to 

 the larger species M. hudsonica was 

 kept with several females of the species 

 M. pudita during one breeding season. 

 Although the animals of these two 

 species lived together peacefully, no 

 young were produced. We are not 



