How Animals Work. 



tinct from the outer and from each other. This re- 

 duction of the inner space appears to be effected in 

 order to counteract the continued increment of the 

 shell, by the deposits of new material along its margin 

 from the border of the mantle, at a greater rate than 

 is required for the accommodation of the soft parts of 

 the animal. 



The Lima sometimes called the Sea-butterfly has 

 a shape somewhat resembling that of a mussel, but is 

 of a beautiful white colour. Here we have an interest- 

 ing example of a nest-building habit, the adult animal 

 spinning together grains of sand, coral fragments, and 

 shells, which are bound together by a mass of threads 

 formed from a natural secretion. Writing of this 

 curious habit, Mr, D. Landsborough states : " The 

 nest is curiously constructed, and remarkably well fitted 

 to be a safe residence for this beautiful animal. The 

 fragile shell does not nearly cover the Mollusc, the most 

 delicate part of it, a beautiful orange fringe-work, being 

 altogether outside the shell. Had it no extra pro- 

 tection, the half-exposed animal would be a tempting 

 mouthful quite a bonne bouche to some prowling had- 

 dock or whiting. It is not content with hiding itself 

 among the loose coral, for the first rude wave might 

 lay it naked and bare. It becomes a marine mason, 

 and builds a house or nest. It chooses to dwell in a 

 coral grotto ; but in constructing this grotto it shows 

 that it is not only a mason, but a rope spinner, and a 

 tapestry weaver, and a plasterer. Were it merely a 

 mason, it would be no easy matter 'to cause the poly- 

 morphus coral to cohere. Cordage, then, is necessary 

 to bind together the angular fragments of the coral 



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