G4 PROCEEDINGS OP THE AMERICAN ACADEMY. 



(11) Albino, in wliich tliere is no pigment whatever. 



(12) Black-eyed white, of wliicli two strains are noted, the eyes in one 

 being a blackish-red. 



"■(13) Variegated, in which " irreguhir, small spots of black or chocolate 

 occur on a white ground." 



So far as regards pigment, therefore, the known types of fancy mice are 

 six, — namely, (1) cjray or " agouti,^^ including the ^^ sable, ^^ and blue-and- 

 tan breeds, in which all three pigments are present; (2) the '■'■golden 

 agouti,'^ in which brown and yellow are the only pigments present; (3) 

 b'ack, including " Wwe," in which there are only the black and chocolate 

 j)igments ; (4) chocolate, containing brown pigment only ; (5) yellow and 

 cream, in which only the yellow pigment is present ; (6) albino, lucking 

 pigment both in the skin and in the eye. 



The gray mouse may be looked upon as an individual in which are 

 present the three [)igment elements, — black, chocolate, and yellow. By 

 the elimination of one of these elements there are produced the hlack- 

 chocolate, or the chocolate-yellow combinations ; if two elements are elim- 

 inated, either chocolate or yellow individuals result. A pure black is to 

 be expected, for if the black pigment may be eliminated and so produce 

 the golden-agouti effect, it would seem that it sliould also be able to 

 appear alone. 



Pied forms of these various types occur, and are generally referred to 

 as spotted varieties. 



Among rats (^Mas norvegicus Erxl.) the gray coat bears a considerable 

 superficial resemblance to that of the mouse, although hitherto no ex- 

 amination of its pigments appears to have been made. Moreover, so 

 far as known, the pigment characters of the rat have undergone resolu- 

 tion only to the extent of producing black individuals. Pied and albino 

 varieties are also well known. 



The origin of the various breeds of fancy mice is to a considerable 

 extent obscure. In a wild state, melanistic individuals of the house 

 mouse are known to occur, and, according to Davatz ('93), are not un- 

 common in the valleys of Graul)iindcn, Switzerland. They were first 

 noticed there at about 18G0, and were described by Fatio ('69) as a 

 distinct species under the name oi 3Ius poschiarinus. They were cap- 

 tured in houses and factories, which they inhabiced in common with 

 mice of the usual gi'ay color, and they seemed to be about one-half 

 as numerous as the gray individuals. All)ino mice and rats are also not 

 of rare occurrence in a wild state. According to J. W. Loudon ("50) 

 albino mice were not unconunoii, particularly in Savoy and some parts 



