1622 THE STORY OF THE UNIVERSE 



the animal finds itself too smooth and too easy to 

 distinguish from surrounding objects; it therefore 

 takes up again fragments of algae and replaces them 

 where they do not delay to take root like cuttings 

 and to flourish anew. 



The sponge-crab (Dromia vulgaris) also prac- 

 tices this method of shelter. It seizes a large sponge 

 and maintains it firmly over its carapace with the help 

 of the posterior pair of limbs. The sponge continues 

 to prosper and to spread over the Crustacean who 

 has adopted it. The two beings do not seem to be 

 definitely fixed to each other; the contact of a sudden 

 wave will separate them. When the divorce is 

 effected, the Dromia immediately throws itself on its 

 cherished covering and replaces it. M. Kiinckel 

 d'Herculais tells of one of these curious Crustaceans 

 which delighted the workers in the laboratory of 

 Concarneau. The need for covering themselves ex- 

 perienced by these crabs is so strong that in aqua- 

 riums when their sponge is taken away they will 

 apply to the back a fragment of wrack or of anything 

 which comes to hand. A little white cloak with the 

 arms of Brittany was manufactured for one of these 

 captives, and it was very amusing to see him put on 

 his overcoat when he had nothing else wherewith 

 to cover himself. 



An Australian bird, the Catheturus Lathami, as 

 described by Gould, is still in the rudiments, and 

 limits itself to preparing an enormous pile of leaves. 

 It begins its work some weeks before laying its 

 eggs; with its claws it pushes behind it all the dead 

 leaves which fall on the earth and brings them into a 



