158 THE PLAY OF ANIMALS. 



an approaching enemy can easily be descried. This in- 

 stinct for clearing the ground Hudson considers sufficient 

 to explain the collection of objects lying about. If Hud- 

 son is right, as seems probable, there is, of course, noth- 

 ing playful about it. Darwin, on the contrary, thought 

 this habit of the viscachas analogous to that of certain 

 birds which I will now describe. The Australian atlas 

 bird (Calodera maculata) builds an intricately woven 

 structure of twigs to play in, and collects near it shells, 

 bones, and feathers, especially those brightly coloured. 

 Mr. Gould says that when the natives lose any small, 

 hard objects they at once search these places, and he 

 knew of a pipe that was recovered in this way.* 



If Darwin regarded these as the only examples of 

 the kind, he must have overlooked some familiar in- 

 stances. One at least relating to mammals is cited 

 by James from Lindsay's Mind in Lower Animals. 

 Keferring to a nest of the Californian wood rat, which 

 he discovered in an unoccupied house: "I found the 

 outside to be composed entirely of spikes, all laid with 

 symmetry, so as to present the points of the nails out- 

 ward. In the centre of this mass was the nest, com- 

 posed of finely divided fibres of hemp packing. In- 

 terlaced with the spikes were the following: About two 

 dozen knives, forks, and spoons; all the butcher's knives 

 — three in number — a large carving knife, fork, and 

 steel; several large plugs of tobacco, ... an old purse, 

 containing some silver, matches, and tobacco; nearly 

 all the small tools from the tool closets, with several 

 large augers, ... all of which must have been trans- 

 ported some distance, as they were originally stored in 

 distant parts of the house. . . . The outside casing of 



* Darwin, loc. cit. 



