1638 THE STORY OF THE UNIVERSE 



partitions: one vertical, the other horizontal, sepa- 

 rating off a small chamber. The vertical partition 

 begins at one of the edges of the door, so that the air 

 from without can not penetrate directly into the 

 dwelling, which is thus protected against extreme 

 variations of temperature. It is in the compartment 

 thus formed that the female lays her eggs and 

 broods, after having taken care to carpet it with a 

 thick layer of small herbs. 



The musk-rats of Canada live in colonies on the 

 banks of streams or deep lakes, and construct dwell- 

 ings which are very well arranged. In their methods 

 we find combined the woven shelter with the house 

 of built earth. Their cabins are established over the 

 highest level of the water and look like little domes. 

 In building them the animals begin by placing reeds 

 in the earth; these they interlace and weave so as to 

 form a sort of vertical mat. They plaster it externally 

 with a layer of mud, which is mixed by means of the 

 paws and smoothed by the tail. At the upper part of 

 the hut the reeds are not pressed together or covered 

 with earth, so that the air may be renewed in the in- 

 terior. A dwelling of this kind, intended to house six 

 or eight individuals who have combined to build it, 

 may measure up to sixty-five centimetres in diameter. 

 There is no door directly opening on to the ground. 

 A subterranean gallery starts from the floor and 

 opens out beneath the water. It presents secondary 

 branches, some horizontal, through which the ani- 

 mal goes in search of roots for food, while others 

 'descend vertically to pits specially reserved for the 

 disposal of ordure. 



