204- OYSTERS, AND ALL ABOUT THEM. 



How then is this ? A mucous, or slimy substance, not 

 easily described, has been provided, in which the surface 

 of a living being is constantly bathed, so that it may suffer 

 no injury from the macerating or decomposing influence 

 which the water, whether salt or fresh, would otherwise 

 exert. As water very speedily decomposes the greater 

 number of organised substances after they are dead, so, 

 apart from the defence, destruction would await the living. 

 Even the most compact of the porcelain shells are invested 

 during life with a kind of membrane, often of extreme 

 tenuity, which possesses the same quality. Most curious, 

 then, is the relation of the sea to a substance which can be 

 wetted by its waters, and to one which cannot be wetted. 

 The wetable substance finds its way to the shore by an 

 obscure but very certain and constant kind of attraction ; 

 while the substance which the water of the sea cannot 

 wet has no such tendency to come on shore, but remains 

 to perform its function in the water. 



Of no consequence is it whether it is a marine plant 

 or animal, or aquatic bird, which frequents the waters 

 without habitually living in them ; for, if it is fitted by the 

 Creator to live in the sea, there is no surface-action so 

 long as it thus exists, and it has consequently no tendency 

 towards the shore. But when either the plant or the 

 animal dies, and ceases to employ its powers, including 

 among the rest the production of the water-repelling 

 mucus, it is immediately subjected to the action of the 

 waters as a dead thing ; the action of the sea casting it on 

 the shore, as having no longer any connection with that 

 economy of life which has there its range. 



Such is the cause of the vast accumulation of shells 

 with which we meet on various spots, and on some of the 



