OCEAN GARDENS ; 



the water. But if any agitation of the water wet 

 this floating apparatus, or the animal withdraw it 

 voluntarily beneath the water for that purpose, the 

 creature immediately sinks to the bottom. 



The swimming power of this race of creatures 

 is equally curious. The Cephalopoda^ by the ejec- 

 tion of a jet of water, propel themselves rapidly in 

 the opposite direction, and by the repetition of the 

 jet at regular intervals, a beautiful power of mo- 

 tion is obtained, as regular, and with less labour 

 than that of ordinary swimming by means of the 

 action of fins or other oar-like limbs adapted 

 to the purpose.^ The Tteropoda^ however, in 

 their little shells, translucent as glass, swim by 

 the action of small fin-like paddles placed near the 

 head. 



The Bivalves do not make so clever a use of 

 their single foot as the Univalves. The foot in this 

 tribe appears to be furnished with a terminal 

 hook, which, when the foot is protruded, clings to 

 some substance, and the animal is drawn up to that 

 point, when the operation has to be repeated ; this 



^ Some species effect leaps by an analogous contriyance — col- 

 lecting water within the closed mouth, and then emitting it at a 

 gush from a small portion of the aperture, suddenly opened, which 

 propels the creature to a considerable distance, as it were, at a 

 single bound. 



70 



