CASTLE AND ALLEN. — THE HEREDTTY OF ALBINISM. 607 



Mendelian hypothesis. In reality Darbishire's observations, when rightly 

 interpreted, afford strong evidence in favor of that hypothesis. It may 

 be well, therefore, to examine them with some care. But before doing 

 so one or two earlier observations should be noticed. 



Haacke ('95) crossed spotted blue-[black-]and-white Japanese dancing 

 mice with albino mice, and obtained offspring uniformly gray in color, 

 like the wild house-mouse, or uniformly black. Occasionally, however, 

 one of the gray or black offspring bore a fleck of white on forehead or 

 belly. 



Von Guaita ('98, :00) repeated the experiment, crossing spotted black- 

 and-white Japanese dancing mice with an inbred stock of albinos. He 

 obtained twenty-eight young, all uniformly gray like the house-mouse. 

 These gray mice bred inter se yielded in subsequent generations gray, 

 gray-white, black, black-white, and white offspring. 



Darbishire's experiment consisted in crossing albino mice with a 

 peculiar race of Japanese dancing mice which had pink eyes and were 

 uniformly white except for patches of pale fawn-color on the cheeks, 

 shoulders, and rump. The dancing mice had been tested and found to 

 breed true inter se. From the cross between these partial albinos and 

 true albinos forty-eight young were obtained, of which all except two 

 were marked more or less extensively with gray ; those two wevefaum- 

 color all over except on the belly, where — we infer from Darbishire's 

 likening them to certain of his gray mice — they were either of a lighter 

 fawn-color or else white. 



Of the forty-six young which were marked with gray, fifteen were 

 gray all over except on the belly and tail, where they are said to have 

 been " nearly white." What is meant by this expression we do not 

 know, unless it be a light shade of gray. If this is the author's meaning, 

 then the fifteen mice were really gray all over. The wild house-mouse 

 itself is often lighter colored on the belly and tail, and these fifteen 

 individuals must be regarded as substantially complete reversions to the 

 gray pigmented type of the wild house-mouse, a type radically different 

 from that of either parent. This result agrees with that obtained by 

 Haacke ('95), von Guaita ('98, :00), and ourselves, upon crossing 

 spotted with albino mice. In thirteen of the forty-six gray-marked mice 

 obtained by Darbishire, the gray covered much more of the body than 

 did the fawn in the Japanese parent ; while in eighteen others the gray 

 corresponded roughly in distribution with that of fawn in the Japanese 

 parent. In no case is the gray described as being less extensive than 

 the fawn in the Japanese parent, and no mention is made of any hybrid 



