90 LIFE IN THE SEA [CH. 



is withdrawn into the shell the food particles are 

 scraped off by other appendages and are then 

 swallowed. Some microscopic infusorians, such as 

 the Vorticellids, which are attached to fixed objects, 

 cause a current of water to flow towards the oral 

 funnel or mouth of the creature, and this current 

 carries with it planktonic food organisms or food in 

 some other form. Other marine animals have more 

 complex methods of capturing their food, but these 

 examples will illustrate the variety of means em- 

 ployed. 



The majority of the larger marine animals take 

 the food into their alimentary canals and digest 

 it in essentially the same way as does the warm- 

 blooded mammal. Many fishes crush the shells of the 

 molluscs or Crustacea which they use as food between 

 the hard roof of the mouth and the bones which form 

 the skeleton of the gills ; Crustacea, as a rule, hold 

 the food animal in their pincers and then pull it to 

 pieces by means of the masticatory appendages ; 

 squids and cuttle-fishes crush the food in their 

 tentacles and then disintegrate it by the horny beaks ; 

 and many molluscs scrape away the food by their 

 rough tongues or radulae. The teeth and jaws of the 

 fishes are organs for the prehension of the food 

 rather than for its trituration, and these animals, as 

 a rule, 'bolt' their food. Starfishes ingest and 

 digest their food outside their bodies, for they can 



