74 MR. W. BATESON ON COLOUR- HEREDITY [May 26, 



8. Cream. Diluted yellow. 



9. Black. Both black and brown present, without yellow. 

 The bases of the hairs are the darkest, and the black does not 

 extend to the tips of the large contour hairs, which are brown. 

 Hairs behind the ears or on belly are a still lighter brown. Com- 

 plication arises from the fact that at least two kinds of black 

 exist, known as "black" and "sable-bred black," viz. thrown by 

 sables. These two kinds probably differ in their heredity- 

 properties. Pied forms common. 



10. Blue. Diluted form of (9) ; both black and brown pigments 

 coexisting. Blues may be thrown by the "blacks" (not sable- 

 bred) and then breed true. Pied forms exist. 



11. Albino. iSTo pigment in any part. As albinos, however 

 produced, breed true to the albino character generally, if not uni- 

 versally, individuals of dissimilar origins are often mixed together. 

 One strain at least, that of Mr. Atlee, is I'ecognised in the fancy 

 as having special features of size and shape, and has been kept 

 distinct for many generations. 



12. Black-eyed white. Strains of this type have been indepen- 

 dently produced twice, perhaps oftener. The degree of pigmenta- 

 tion in the eye varies in at least one strain, some eyes being full 

 black, others looking blackish red. Whether the type ever breeds 

 quite true we cannot say. In our experience offspring with small 

 black mai'ks occur (compare phenomenon seen in albino Guinea-pig, 

 p. 76). 



13. Variegated. In these, irregulai- small spots of black or 

 chocolate occur on a white ground. Such forms are quite distinct 

 from the ordinary piebald and Dutch-marked (viz. like the Dutch 

 rabbit) combinations of coloui* with white. 



In comparing coloui'S care must be taken that specimens are of 

 similar age and in similar moult-stages. Differences of intensity 

 of colour are of course characteristic of different strains, and 

 pi-obably intermediates can be found ; but there is no doubt of 

 the practical distinctness of each of the forms enumerated. 

 "Brindling," viz. lighter or even white hairs distributed as 

 ticking, occurs in some of the coloured varieties, as in rabbits, but 

 we have not been able to examine specimens, 



As to the age and mode of origin of the several forms little is 

 known certainly. Several conditions are plainly due to resolution of 

 compound characters, such as often follows crossing in animals and 

 plants. The blue, the black-eyed white, and the variegated are 

 certainly productions of the last few years ; the rest (? sable) have 

 existed for a long time. 



The question how far M. sylvaticits has been used in the pro- 

 duction of the varieties is a very important one. The experiment 

 was suggested many years ago in ' Fancy Mice ' and has probably 

 been often tried. Mr. Atlee has given me a most circumstantial 

 account of a cross with this species made by him nine years ago 

 on black-and-white does, and I feel no reasonable doubt that it 



