LITTLE BEASTS OF FIELD AND WOOD 



motion as in summer, barely swaying the water- 

 weed and cresses as it slips between them. He 

 is capable of holding his breath for a surprisingly 

 long time, and when compelled to renew it, has 

 only to come up and breathe it out beneath the 

 ice, where it soon becomes oxygenated by the 

 water. There are always bubbles of varying size 

 just under the ice, but whether they contain 

 oxygen, or only hydrogen gas generated by the 

 decomposing vegetable matter at the bottom, I 

 am unable to say ; if the former, they must add 

 materially to the muskrat's air-supply, and, theo- 

 retically, contact with freezing water should 

 render them fit to breathe. But there is gen- 

 erally plenty of air to be had close up under 

 the edge of the bank, where the water has re- 

 ceded ; and when the muskrat has captured a 

 clam, or succeeded in digging up the root he 

 wants, he swims with it to his cabin, or to his 

 hole in the bank, to devour it at his leisure. 

 Occasionally a foot or more of ice will form 



i66 



