I OUR GRAY SQUIRRELS 5 



the squirrels scampered, no less to their delight 

 than to ours, often leaping one over the other with 

 extraordinary agility and grace when two met on 

 this single-track, air-line road. 



One of these bridges led to a window-sill in each 

 residence, where food was often spread, and it was 

 amusing to see the circumspection with which, at 

 last, they crept toward it along the icy poles, dig- 

 ging their claws into the glazed surface, and often 

 slipping astride or almost off the bridge. 



In the tree-tops, where they rush and leap at 

 full speed, they are by no means safe from falling, 

 but usually manage to catch hold somewhere, often 

 by only a single toe, apparently, yet are able to lift 

 the body up, like gymnasts, to a firmer foothold. 

 Their strength is remarkable, especially in the re- 

 gion of the great hams, whose development ac- 

 counts for the really astonishing leaping powers 

 these animals possess. 



Should they fall clear to the ground, as some- 

 times happens, they alight right side up like a cat, 

 and seem none the worse for the accident. The 

 feet are wide-spread in such a case, and the loose 

 skin over the ribs is stretched and flattened out 

 very perceptibly. It would seem only a step from 

 that condition to the parachute with which the 

 flying-squirrel is provided ; but if the development 

 of this formation in the latter came about through 

 natural selection, it must have begun very long 

 ago, for Cope has found a fossil (A llomys), which 



