90 ANNALS NEW YORK ACADEMY OF SCIENCES 



maintained for three years. They have produced but few young, behaving 

 in this respect like the ordinary house mouse when confined in a small 

 cage. The males have, however, crossed freely with domesticated races 

 and this happens also in the case of the house mouse. In most cases, my 

 sports were bred to gray and produced white-bellied and gray-bellied 

 young. In a few cases, the white-bellied forms when bred to each other 

 produced white-bellied and gray-bellied offspring. On the other hand, 

 two gray-bellied mice of this strain produce only gray-bellied young. 

 These facts show that the white belly is dominant to the gray belly. 



CROSSES BETWEEN THE SPORT AND DOMESTICATED RACES WITH UNIFORM 



COAT 



The sports have been crossed with all of the ordinary varieties of 

 domesticated mouse. The results in the first generation are shown in the 

 following table, in a generalized statement. 



Gray white-bellied by yellow = yellow, and gray with white belly. 



" gray with gray belly = gray with white belly. 

 " black = gray with white belly. 

 " " chocolate = gray with white belly. 

 " " " " white = gray with white belly. 



Like the wild gray mouse, the sport is dominant to all other colors 

 except yellow. The sport, moreover, transmits its entire coat pattern 

 when it dominates, and even when it becomes recessive in the yellow cross, 

 the coat pattern reappears in the next generation. 



We may now proceed to examine in detail the crosses summarized in 

 the above table. 



Crosses between the Sport and Yellow Mice 



Six litters were obtained from male grays with white belly and yellow 

 females, consisting of fourteen yellows and eleven grays. Of the grays six 

 were recorded with white bellies, one with a gray belly, four nnt recorded 

 for ventral color. Assuming that half of the yellow gametes bear yellow 

 and half any other color, or colors, the results accord with theory. This 

 cross was of particular interest because by it I wished to test whether 

 yellow is allelomorphic to the other colors — gray, black and chocolate. If 

 the yellow-bearing gametes bear only yellow, then all the F x yellows from 

 a cross with gray should produce, when inbred, only yellows and grays as 

 three to one (or two to one). If, on the other hand, yellow stands alone 

 and is allelomorphic to its absence, then the offspring of the F x yellows 



