230 ANIMALS UNDERGROUND 



more full of gaiety and buoyant spirits than a prairie- 

 dog, or even a sandhill-rabbit ; and we have only once 

 seen an animal grimy from attempted burrowing, and 

 that was an opossum which mistook a chimney for a 

 hole in a hollow tree. Some have coats so close and 

 fine that sand runs off them as water does from 

 feathers ; others have ' shivering muscles,' by which 

 they can shake their jackets without taking them off. 

 Rats, however, do object to some forms of dust, and 

 will not burrow in it. An old Suffolk rat-catcher 

 always laid ashes in the runs made by them beneath 

 brick floors. His theory on the subject was that the 

 ashes * fared to make them snuffle/ But even if earth, 

 dust, and clay do not adhere to the animals' coats when 

 burrowing, the danger, or at least the discomfort, to the 

 delicate surface of the eye would seem to afford an 

 almost constant source of uneasiness to creatures 

 burrowing in loose soil. And the eyes of most burrow- 

 ing creatures are by no means protected against such 

 damage. If the rat and the rabbit had a horn plate 

 over their eyes, as a snake has, or overhanging eye- 

 brows and deeply-sunk orbits, the modifications would 

 be at once explained by evolution ; but they exhibit 

 no such modification whatever. On the contrary, both 

 of them have prominent, rather staring eyes, without 

 protection, and no eyelashes to speak of. We believe 

 that, just as divers learn to keep their eyes open under 



