148 THE INDUSTRIES OF ANIMALS. 



At first enclosed in the remains of a Trochus, he 

 changes into that of a Purpura; a little later he seeks 

 asylum in a Whelk. Beside the shelter which these 

 shells assure to the Crustacean, they serve to mask 

 bis ferocity, and the prey which approaches con- 

 fidently what it takes to be an inoffensive Mollusc, 

 becomes his victim. 



The Great Horned Owl likewise does not con- 

 struct a nest ; but takes possession of the dwellings 

 abandoned by others. These birds utilise for laying 

 their eggs sometimes the nest of a Crow or a Dove, 

 sometimes the lair which a Squirrel had considered 

 too dilapidated. The female, without tvoubling 

 about the bad state of these ruins, or taking pains 

 to repair them, lays her eggs here and sits on 

 them. 



Classification of artificial shelters. — It is time to 

 turn to animals who have more regard for comfort, 

 and who erect dwellings for themselves or their 

 offspring. These dwellings may be divided into three 

 groups: (i) Those which are hollowed in earth or in 

 wood ; (2) those which in the simplest form result 

 from the division of material of any kind; then, as a 

 complication, of materials bound together ; then, as 

 a last refinement, of delicate materials, such as blades 

 of grass or threads of wool woven together ; such are 

 the nests of certain birds and the tents of nomads ; 

 (3) those which are built of moist earth which 

 becomes hard on drying ; the perfection of this 

 method consists of piling up hard fragments, pieces 

 of wood or ashlar, the moist earth being only a 

 mortar which unites the hard parts together. Animals 

 exercise with varying success these different methods, 

 all of which Man still practises. 



