40 ANIMAL COMPETITORS 



alone could have produced and preserved the 

 race of dancers." 



That it originated in a "freak" seems very 

 likely, since mere cultivation of the familiar 

 white mice (albinos), beloved of children, never 

 develops into a habit of whirling. A German 

 naturalist inbred albino mice for 28 generations 

 without producing any hint of such a pecul- 

 iarity. 



Prevalence of mice. House-mice are very 

 prolific. They will begin to produce young 

 when only three months old, and continue to 

 breed at intervals of two or three months all 

 the year round. It is not known whether any 

 proper pairing takes place probably not. 

 The period of gestation is 25 days, five to ten 

 young are produced at a birth minute, pink, 

 blind, hairless things and are weaned after 

 about two weeks. 



There are few houses or barns in which mice 

 do not make themselves at home, racing from 

 cellar to garret in the hollow walls and par- 

 titions, and gnawing passageways wherever 

 they think it worth while. Too often they 

 penetrate where food is kept, and besides what 



