The Worms and some of their Posterity 



The ordinary star-fish is carni- 

 vorous, and lives largely on 

 ordinary mussels, which it 

 bridges over with its arms, and 

 opens by a steady and long- 

 continued pulling, the soft 

 parts being then sucked up by 

 the partially protruded stom- 

 ach. A few types of Echino- 

 derms are shown in Figs. 46, 



47, 48. 



The group of the Mollusca 

 includes such common forms as 

 cuttle - fishes, whelks, slugs, 

 snails, mussels, and oysters. 

 These, it will be observed, com- 

 prise marine, freshwater, and 

 land forms. The molluscs, like 

 the next two groups with which 

 we have to deal, have made a 

 conquest of the land, though in 



FIG. 47. Feather Star. 

 Photo : Harold Bastin. 



67 



FlG. 46. Star-fishes. 



the present instance it cannot 

 be regarded as very com- 

 plete. The anatomy of the 

 group shows much variation, 

 and only a few of the leading 

 features can be alluded to. 

 The digestive system is 

 highly developed. The 

 mouth is provided with a 

 jaw or jaws, and with a 

 tongue-like ribbon, which is 

 covered with rows of teeth, 

 like a file, and by whose 

 action the food is torn and 

 disintegrated. A gullet leads 

 from the mouth to a stomach, 



