ANTIQUITY OF THE FANCY MOUSE 



17 



The essential feature of this law is the fact that the charac- 

 teristics which differentiate domestic varieties are inherited 

 as units, capable of being combined in all possible ways 

 through the agency of hybridization. Up to the present time 

 about two dozen such unit-characters have been recorded 

 for the house mouse. The more important of these appear 

 to have been first recorded at dates approximately as follows : 



Character 



Date 



Authority 



B.C. 



Dominant spotting c.1100 



Albinism 300 



Waltzing 80 



A.D. 



Pink-eye dilution 1640 



Black 1640 



Recessive spotting (piebald) 1766 



Chocolate 1843 



Naked (dominant hairless) 1850 



Chinchilla c.1890 



Extreme dilution c.1890 



Yellow 1902 



Blue 1903 



Short ears 1921 



Rodless 1924 



Recessive hairless 1926 



Shaker 1926 



Hyperglycemia 1926 



Dwarf 1929 



Eh Yah 



Aristotle 



Annals of Han Dynasty 



Johnson 



Johnson 



Pallas 



Gray 



Gordon 



Blake 



"An old fancier" 



Cuenot 



Bateson 



Lynch 



Keeler 



Brooke 



Lord and Gates 



Cammidge and Howard 



Snell 



In accordance with our present ideas, each unit-character 

 made its appearance as a sudden, discontinuous physical or 

 chemical change in the germinal substance, which forms the 

 basis of heredity. We call such changes mutations, and the 

 material bodies in which these changes occur are called 

 genes. We can demonstrate the existence of a gene only 

 when, as a consequence of mutation, it occurs in two differ- 

 ent alternative forms in different individuals of the same 

 species. By crossing individuals which bear different allelo- 

 morphs of the same gene, we can show that transmission of 

 the contrasted characters conforms with Mendel's Law. 



