MORGAN, COAT COLORS IN MICE 105 



production of such forms, but also to show that, being aware of their 

 occurrence, I have been less liable to confuse the unusual colors that I 

 have described — such, for instance, as the black-chocolate that simulates 

 gray. 



The lighter races were made by crossing dilute chocolates with cinna- 

 mon agoutis and then extracting, or by crossing light black with cinna- 

 mon agoutis and extracting. In the former case, some of the F 2 mice 

 were extremely pale, and the chocolate band appeared to be dilute. In 

 the latter case, one might expect to obtain some mice in which both the 

 black band and the chocolate band were dilute. In fact, I have had sev- 

 eral kinds or at least colors of dilute mice with ticked hair, but I hesitate 

 to class them under these two groups without further and more careful 

 examination, because these dilute forms appear to be variable and the 

 color of the coat may change with every moult. One of these changing 

 coats is shown in Plate VIII, fig. 2, where the combination gives a re- 

 markable contrast. 



Crosses between Black and White Spotted Waltzers and Yellows 



In order to test in another way whether the yellow gametes of yellow 

 mice carry the factor for other colors than yellow, I crossed a yellow 

 with a black and white waltzer of known pedigree that carried only black. 

 Two yellow mice from this cross were inbred and produced a litter con- 

 taining yellows, blacks and chocolates. I concluded that the yellow 

 gametes may carry in addition to yellow the factor for chocolate. Cuenot 

 objected to this conclusion, on the ground that my original yellow con- 

 tained the diluting factor, which, according to his view, changes black to 

 chocolate. Cuenot's objection will not hold for two reasons. First, be- 

 cause chocolate is not due to the diluting factor for black, since Miss 

 Durham has shown that the dilute form of black is not chocolate, but 

 dilute black or blue. Second, because if the diluting factor were present, 

 the later generations of these mice should make evident its prsence, 

 which was not the case. Nevertheless, I now believe that Cuenot's objec- 

 tion holds good in principle. If, as I have attempted to show, black is a 

 higher development of chocolate, the black waltzer must have contained 

 in duplex this factor that changes chocolate to black, and his spermatozoa 

 must have contained this factor only in the simplex condition. The yel- 

 low mouse in question must not have contained this factor, hence the 

 yellow offspring (F x ) contained it only in simplex form. It will be 

 present or absent, therefore, in their gametes. Those containing it, and 

 the factor also for chocolate, will give black; those without it will give 



