30 



ZOOLOGY. 



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 arising at or near the 

 base of the large one. 



The coral polyps only differ from the sea-anemones in 

 secreting a limestone support or coral-stock. Corals are 

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



Fio. 31. — Coral polyp (Astroides calyctilaris) expanded. 



Zoology. 



From Lut ken's 



branching or rounded masses. The soft parts are supported 

 by limestone partitions secreted in the chambers of the 

 polyp. 



All Actinozoans develop from eggs, and at first appear 

 as little oval, ciliated, free-swimming embryos (gastrulce), 

 which eventually become attached to the bottom of the 

 sea. 



Before the embryo becomes fixed and the tentacles arise, 

 the lime destined to form the partitions begins to be de- 



