Wright: Color Inheritance in Mammals 



375 



has been combined with others in such 

 a way as to demonstrate its place as an 

 independent set. The second piebald 

 factor does not appear to have been 

 combined with the brown and dilution 

 series, but will no doubt be found inde- 

 pendent when so combined. The agouti 

 series of four allelomorphs was dis- 

 covered by Cuenot^ and thoroughly 

 confirmed by Sturtevant,^ Morgan,'^ 

 and Little.^ 



There remains to be considered the 

 possibility of linkage between the differ- 

 ent series of allelomorphs. The linkage 

 relations of the piebald factors do not 

 seem to have been thoroughly investi- 

 gated except that Little^ has shown 

 them to be nearly or quite independent 

 of each other, and the first one is 

 known to be independent of albinism 

 (Cuenot,^ Allen," and Durham. ^'^) Dilu- 

 tion, non-agouti, brown eye and pink eye 

 were shown to be without appreciable 

 linkage in a four-factor cross involving 

 very large numbers made by Little 

 and Phillips. ^^ These results are also in 

 harmony with those obtained by Cuenot 

 and Miss Durham. The relation of 

 albinis'm to the others has not been 

 worked out very thoroughly, but one 

 case of partial linkage here is very 

 probable. Darbishire^^ crossed pink- 

 eyed colored mice with albinos from 

 dark-eyed strains (CCpp x ccPP). Fi 

 were all dark-eyed. In F2 there were 

 137 albinos, 284 dark-eyed and 134 

 pink-eyed colored. Darbishire recog- 

 nized the closeness to a 1:2:1 ratio. 

 This is to be expected on complete 

 linkage, but not on independence, in 

 which case the ratio should be 4 : 9 : 3. 

 Cuenot/'' in the same cross, obtained 

 21 albinos, 46 dark-eyed and 25 pink- 



eyed colored, in close agreement. Com- 

 bining, the ratio of dark-eyed to pink- 

 eyed is 330:159 with a deviation of 5.7 

 times the probable error from the ex- 

 pected 3 :1 ratio. Tests of F2 individuals 

 bear out the theory of linkage, but also 

 show that linkage is far from perfect. 



PIEBALD MICE 



Some very interesting work has been 

 done on piebald mice. The pattern is 

 variable in extent, and apt to be mark- 

 edly asymmetrical. All variations exist 

 between self and black-eyed white. 

 Cuenot^* showed that the pied character 

 behaves in general as a Mendelian 

 recessive to self and is inherited inde- 

 pendently of albinism or the quality of 

 color of the mouse. These results 

 have been confirmed by all later workers. 

 Cuenot recognized that much of the 

 variation is merely developmental, being 

 unrepresented in the germ plasm. He 

 suggested, however, that a series of 

 multiple allelomorphs such as he had 

 found in the yellows and agoutis was 

 responsible for the gradations. That 

 such allelomorphs may exist is very 

 probable in view of conditions found in 

 rats, but it has never been critically 

 demonstrated. On the other hand, 

 another piebald factor has been dis- 

 covered which has been shown by 

 Durham, i'^ Little,^" and Detlefsen^^ to 

 be independent in inheritance, but to 

 cooperate with the first in development. 

 The case has been most thoroughly 

 worked out by Little who found that the 

 second piebald factor could not be 

 obtained in a homozygous condition, 

 thus resembling the well known case of 

 the yellow mice. The situation as he 

 found it was as follows: 



« Cuenot L. 1904. Arch. Zool. Exp. et Gen. (4), 2, Notes et revue 45-56. 

 ^Sturtevant, A. H. 1912. ^wer iV«/., 46:368-371. 

 5 Morgan, T. H. 1914. Amer. Nat., 48:449-458. 

 «Little, C. C. 1914. Amer. Nat., 48. 

 'Little, C. C. 1915. Amer. Nat., 49:727-740. 



8 Cuenot, L. 1904. Loc. cit. 



9 Allen, G. M. 1904. Proc. Amer. Acad. Arts and Set., 40:61-163. 



10 Durham, F. M. 1908. Rept. Evol. Com. Roy. Sac, 4:41. 



11 Little, C. C. and Phillips, T- C. 1913. Amer. Nat., 47 : 760. 



12 Darbishire, A. D. 1903, 1904. Biom., 2:101-104, 163-173, 282-285; 3:1-51. 

 " Cuenot, L. 1907. Arch. Zool. Exp. et Gen., (4), 5. Notes et revue, p. 1. 



" Cuenot, L. 1904. Loc. cit. 



15 Durham, F. M. 1908. Loc. cit. 



16 Little, C. C. 1915. Loc. cit. 



1' Detlcisen, J. A. 1916. Amer. Nat., 50:46-49. 



