No. 512] 



NOTES AND LITERATURE 



501 



the second generation snch black mice give approximately 



9 black, 3 blue, 3 chocolate, 1 silver fawn, 

 which is the Mendelian expectation. 



When blues are mated to silver fawns the offspring are all 

 blue. These inbred give three blues to 1 silver fawn. 



Miss Durham's hypothesis gives a consistent account of the 

 relation of the dense and dilute colors to each other. 



The dilute colors are modified to some extent, as Cuenot first 

 showed, by the condition of the eye color. .Most mice with 

 colored coats have black eyes. The black eye is due to black 

 pigment in most cases, but in chocolates and in some yellows 

 the dark eye is due to chocolate pigment, as Castle and Durham 

 have independently found. A silver fawn with pink eyes may 

 be of a different color from a silver fawn with dark eyes. How 

 this modification results is not yet known. In fact, this relation 

 of dilute colors to eye color offers a promising field for further 

 inquiry. 



An examination of the hair of dilute mice shows great differ- 

 ences in the amount of* pigment in each hair and the color of 

 the animal is modified by the average number of hairs of a given 

 kind. A considerable range of shades is evident. Whether 

 this is only a fluctuating character, or whether pure races of 

 different shades can be made that give Mendelian proportions, 



I think, that the pigment granules themselves are not only scat- 

 tered to varying degrees but may be even lighter or darker. 

 Whether this is due only to size or to another factor is not yet 



These dilute colors should combine with ticking to produce 

 different shades of gray in addition to cinnamon agouti. Some 

 of the grays that I have met with appear to fall under this 

 head. 4 Whether the diluting factor for black and chocolate 

 will act as a diluter for yellow is not known. Here we meet 



