PROTRACTILE MOUTHS 



itself; if its captives were always alone with one another, 

 the strongest would soon destroy the weakest, after 

 which, since they themselves could find no more food, 

 they would perish in turn. So they must all be supplied 

 with food, and this usually consists of slices or mash of 

 the flesh, cut up or minced if necessary, of various 

 aquatic animals, fish, crustaceans, and little shell-fish. 

 In the large public institutions of this kind, feeding 

 takes place at regular hours, or under certain conditions. 

 As one might expect, it has its regular attendants, and 

 not without reason; the fish, excited by hunger, dash 

 about in all directions, and show, perhaps more clearly 

 than at any other time, of what they are capable. 



The aquarium, which is a faithful reproduction of 

 nature on a small scale, contains creatures of two kinds : 

 those which are free and, since they can move in any 

 direction, dash up to their food and snap it up directly, 

 and those which are attached to the bottom or to supports, 

 unable to move, and are thus compelled to wait until their 

 food sinks down to them. These eat only by accident. 

 Dependent upon chance, they are, for that very reason, 

 all the more interesting to watch. 



Among them we see various kinds of sponges. 

 Some, spread out over different objects, bits of rock or 

 fragments of shell, look like irregular incrustations, 

 brightly coloured, the reds and yellows predominating. 

 Others form inert balls, sometimes as large as one's 

 fist and brilliantly coloured like the others. Attached 

 to their rocky support, they remind us of the coloured 

 globes which are sometimes put on a pedestal and used 

 for ornament. Others stand up like little bushes, 

 with nothing but their trunks and thickish branches. 

 In spite of this diversity of appearance, the motionless 

 character which long gave rise to doubts of their being 

 animals at all, gives them a certain uniformity of be- 

 haviour and structure. Their surface is perforated 

 by a number of orifices of different sizes, in one place 

 so minute that they are hardly visible, in another wider 

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