l8 BULLETIN OF THE LABORATORIES 



thus the danger of freezing solid is obviated. The earth is used in 

 plastering the outside of the hut, though this is not systematically 

 done. A curious habit we. have occasionally observed is the thatching 

 of the hut with the large water-lily leaves so overlapping and cement- 

 ed with mud as to form an impervious roof. By this time the ice is 

 beginning to form and the hut has settled as much as it will, being 

 buoyed up by the ice. The rats now burrow into the house from near 

 the bottom forming a passage in the form of a letter U inverted, the 

 uppermost part being above the water level and here a small chamber 

 is excavated. Run-ways are excavated beneath the ice to various 

 parts of the pond. In the long excursions undertaken beneath the ice 

 the rats are said to ascend to the ice and exhaust the lungs, permitting 

 the expired air to absorb oxygen and then reinspire it. This we have 

 never been able to observe. The roots of Nuphar are built into the 

 house or are stored conveniently near for winter use. The great mass 

 of vegetable matter soon begins to "heat" generating warmth enough 

 not only to add to the comfort of the occupants of this curious home 

 but to cause new sprouts to spring from the roots. The chamber is 

 enlarged during the winter and the part removed serves to supply food 

 in case of outside famine. The outer layer of mud freezes solid and 

 forms an adequate defense against the wolves which might otherwise 

 wage a war of extermination. There seems to be a certain reciprocity 

 between the occupants of adjacent lodges, although the rats are jeal- 

 ous by nature and have not the communistic characters of the beaver, 

 though no whit inferior to them as architects. 



As to the statement commonly believed by woodcraftsmen in the 

 West that the muskrat prearranges his hut in view of the length and 

 severity of the coming winter we can offer nothing definitely. There 

 is, however, a wide variation in respect to the size and structure of 

 the huts and a general correspondence though by no means a univer- 

 sal one, between the huts built during a given season. An average 

 hut is 6xio feet in diameter at the water's edge and the size of the 

 chamber varies from 18 inches to two feet. 



The Pocket Gopher or Pouched Rat, Geoviys bursartus, al- 

 though abundant west of the Mississippi, is probably unfamiliar to 

 most non-professional observers. This animal is nevertheless the rep- 

 resentative of one of the most interesting and distinctive of North 

 American mammals. 



