FEEDING OF MARINE ANIMALS 207 



suckers and held away from the body of the attacker. The 

 mouth of the octopus and squid is in the centre of the 

 arms and possesses a pair of extremely powerful horny 

 jaws (Plate 78), shaped like the beak of a parrot, and also 

 a small radula. After the prey has been seized it is bitten 

 into by the jaws and a poison poured in which quickly kills 

 it. The flesh is then dissolved away by means of digestive 

 juices produced by special glands and the fluid sucked in 

 through the mouth. In this manner the shell of a crab is 

 entirely cleaned out and then discarded. 



The crab and lobster family are mainly scavengers, 

 feeding on whatever they can obtain, dead or alive, plant 

 or animal. They seize their food by means of their powerful 

 pincer-like claws in which it is first crushed and then pushed 

 towards the mouth which is guarded by a whole series of 

 jaws and other appendages by means of which the food 

 is torn up and shredded out until it can be easily swallowed. 

 The stomach of these animals is lined with a horny substance 

 and has also three teeth which are worked by muscles 

 attached to the shell and in such a way that all three come 

 together in the centre of the stomach breaking up the food 

 still further so that it can be digested by the animal. 



Feeding of Marine Vertebrates 



Broadly speaking, the fish may be divided into two classes, 

 those which feed on the plankton, and those which feed on 

 the larger swimming animals, or, more especially, the bottom- 

 living animals. Of the former, the herring and mackerel 

 are the best known and most important, both of them 

 swimming about freely in mid-water. They feed by strain- 

 ing great quantities of water over the gills where the 

 plankton, especially the small crustacean copepods, is 

 collected in a sieve consisting of a parallel series of slender 

 horny projections from the front side of each gill arch and 



