IV 



UNIT-CHARACTERS (GENE MUTATIONS) 

 OF THE HOUSE MOUSE 



The Japanese, as already stated, must be given credit for 

 the development of a number of varieties of domestic mice. 

 An ivory netsuke or sash pendant in the Louvre {155) carved 

 about 1790 by the Japanese artist Masateru depicts a family 

 of fancy mice in natural color among which one may dis- 

 tinguish the unit-characters pink-eye, piebald, non-agouti, 

 albinism, and waltzing (see Fig. 5). Similar netsukes were 

 popular during the nineteenth century. 



Fig. 5. The mouse aetsukl by the Japanese artist, Masateru. 

 (After a photograph hy Schluruberger.) 



We have reason to believe that each unit-character arose 

 by mutation or physical change in a particular gene located 

 in a particular chromosome of a germ cell, and that this con- 

 dition was transmitted to subsequent generations through 

 heredity, the character manifesting itself in those individuals 

 which carried certain hereditary combinations. 



We may also be confident that identical sports have arisen 

 in the wild at different times in remote parts of the world. 

 Among the stuffed skins of the house mouse in the British 

 Museum collections in 1926 were found pink-eyed dilutes 

 from the Isle of Wight off the coast of England and from 

 Zanzibar (the same variety was recently taken in the wild in 

 Germany). Albinos had been collected from numerous locali- 



