INHERITANCE OF WHITE-SPOTTING IN RABBITS. 



13 



To test this matter, crosses of tan have been made with each of the 

 other three, white, dark, and self. Tan was found to be allelomorphic 

 with self in the black-and-tan race where it appeared (table 12), but 

 self being a purely negative term (meaning as here used unspotted) 

 one could not be sure in advance that self, as the allelomorph of 

 different kinds of Dutch, would be one and the same thing in all 

 cases. This would require demonstration. It is necessary, then, to 

 ascertain first whether tan Dutch is an allelomorph of white and of 

 dark. 



Crosses of tan with white have given the results shown in tables 26, 

 28, and 29, and also graphically in text-figure 4. FI is intermediate. 

 F 2 is likewise interme- 

 diate, but varies to or 

 into the range of the 

 uncrossed races with 

 indications of segre- 

 gation of modified tan 

 and modified white 

 individuals. The ab- 

 sence of selfs in F 2 

 shows white Dutch 

 and tan Dutch to be 

 allelomorphs. The 

 back-cross with white 

 (FiXW) produces in- 

 dividuals varying (as 

 expected) all the way 

 from the F x to the un- 

 crossed white race, 

 but with an apparent 

 tendency to form &rada 

 modes on 10 and 15. 

 These, it seems, represent the mutually modified modal conditions of 

 the FI and the white race. The extracted whites have their mode low- 

 ered to 15, instead of on 16 or 17, as in the uncrossed white race; and 

 the extracted FI'S have their mode advanced from grade 7 (in the orig- 

 inal FI'S) to grade 10. 



The races dark and tan are similar to each other in grade (see text- 

 figure 5), but differ in the location of their unpigmented areas, as 

 already explained. Dark has a wider collar and a darker head; tan 

 has a narrower collar and a whiter head. FI is nearly or completely 

 self-colored, since dark tends to make the head pigmented and tan to 

 make the collar pigmented. Consequently there is little space left 

 unpigmented. F 2 is quite variable, some individuals being darker 

 than either uncrossed race, while others are whiter. The range is from 



13 14- 15 IS 17 



TEXT-FIGURE 4. 



