ALLEN. — THl'] IIKREDITY OF COAT COLOR IN MICE. 



69 



boxes in five tiers. Thus an economy of space was secured, while the 

 compactness of tlu; system made feeding and cleaning easier. The floors of 

 the cages are kept covered with clean sawdust, and wooden berry baskets, 

 one to each compartment, inverted and filled with cotton, serve for nests. 



As for food, bread and milk are used as a staple, care being taken 

 that the mixture should not contain more li(iuid than the bread will 

 absorb. Oats and bits of vegetable, as well as green grass, afford a 

 welcome variety. 



In work of this sort, where it often becomes necessary to test the same 



FiGUUE 2. 



mouse with various other individuals, some means of marking the animals 

 is needed, so that a given individual may be identified readily from among 

 similarly colored mice. To this end the writer has used the system 

 employed by Professor Castle in connection with guinea-pigs and rabbits, 

 namely, that of punching small holes in the ears. The left ear may be 

 used for tens, the right for units. A small circular hole at the anterior 

 base, tip, or posterior base, stands for 1, 2, or 3, respectively. A scallop 

 or notch iu the same places represents 4, 5, or 6, respectively ; while by 

 using two notches, combinations standing for 7 ,-S, or 9 are readily made. 

 An ear unpunched stands for 0. After the numbers from 1 to 99 have 



