DOMESTIC RATS AND MICE 39 



It is in this fancy, too, that breeders, perhaps unwittingly, 

 make the greatest use of Mendelian principles. Crosses are 

 made, and brothers and sisters mated in expectation of the 

 appearance of desired colors, not visible in the first gen- 

 eration. Mouse fanciers do not prate of the evils of inbreed- 

 ing, but consistently practise this method of securing colors 

 not otherwise easily obtained. 



It is of interest to note that while rats and mice, par- 

 ticularly the latter, have been produced in many color 

 varieties, no changes of form or coat have appeared. The 

 Waltzing Mouse is the only breed which shows other than 

 color variation. Rats, perhaps because less extensively bred 

 than mice, are seen in fewer color phases. The recent de- 

 velopment of yellow and cream rats will be mentioned 

 later on. 



Fancy Mice 



Mice, because of their smaller size and gentler nature, are 

 more desirable as pets than rats. If at all accustomed to 

 handling, as they should be, they rarely attempt to bite, and 

 quickly become tame and confiding. 



In housing mice, it must be remembered that they are 

 sensitive to cold, draught and dampness, all of which must 

 be guarded against. It certainly is safest to keep mice in 

 heated quarters during cold weather. At any rate, some 

 warmth must be provided when the temperature drops to 

 the freezing-point. Draught is avoided by using cages open 

 on one side only. 



The casual keeper of a pair of pet mice will find most 

 suitable a wooden case, say 12" x 8" x 6". This should have 

 one side covered with one-quarter or one-eighth inch square- 

 meshed wire, which will keep the occupants in, and also 

 protect them from unwelcome relatives who may visit them. 

 This also permits easy inspection of the pets by their owner. 



