34 



FIRST LESSONS IN ZOOLOGY. 



of the digestive canal. The bones, shells, or hard covering of the 

 animals which may be swallowed by the Actinia are rejected from 

 the mouth after the soft parts are digested. 



Sea-anemones have been found to have a slight sense of 

 smell. Nearly all sea-anemones, besides arising from eggs, 

 increase by budding, new individuals growing out at or near 

 the base of the large one. 



The coral polyps only differ from the sea-anemones in 



FIG. 32. Coral polyps, some expanded and others shut up within the hollow of 



the coral-stock. 



secreting a limestone support or "coral-stock/' Corals are 

 either cup-shaped and single, or are compound, forming 

 branching or rounded masses. The soft parts are supported 

 by limestone partitions secreted in the chambers of the 

 polyp. 



All polyps develop from eggs, and at first appear as little 

 oval, ciliated, free-swimming embryos (gastriilcs), which 

 eventually become attached to the bottom of the sea. 



