FEEDLNG OF MARINE ANIMALS 



205 



is just as steadily replaced, new material being added to the 

 hind end of the ribbon continuously. It varies very much 

 in different animals depending on their particular type of 

 food, thus in the animals we have been discussing it is broad, 

 the better for scraping over wide surfaces, while in the 

 carnivorous snails, which we shall discuss later, it is much 

 narrower. 



Preying Animals 



Great numbers of animals in the sea prey upon other 

 animals either living or dead. All the anemones and 

 jellyfish, in spite of 

 their delicacy and great 

 beauty, are really vor- 

 acious carnivores. They 

 seize their prey, which 

 may be anything from 

 worms to small fish, by 

 means of their tentacles, 

 which are armed with 

 batteries of minute 

 " nettle cells," each of 

 which consists of a tiny 

 bag filled with fluid 



and drawn out into a fine whip-like process which lies coiled 

 within the bag. When they are touched by any animal 

 these nettle cells explode and the thread, which is usually 

 barbed, is shot violently out and into the body of the prey. 

 The fluid in which the thread has been bathed is poisonous 

 and some of this enters the wound causing paralysis. The 

 prey is then pushed into the mouth and taken into the 

 stomach, where it is digested with remarkable speed 

 (Fig. 45). Many jellyfish will seize and swallow animals 

 larger than themselves, seizing young fish with their delicate 



Fig. 44, — Diagram of Radula. G., gullet ; 

 J., jaws ; M., uiouth ; R., radula, which can 

 be pushed forward through mouth-opeaing. 



