88 THE WORLD OF THE SEA. 
bell-like form; hence the name. The species Campanularia dicho- 
toma is at once the most delicate and the most elegant of its kind. 
It has a brownish stem, thin as a thread of silk, and still firm and 
THE SILVER SERTULARIA, 
(Sertularia Argentea.) 
elastic. The polypes are very numerous; upon a stem eight or 
nine inches high there are several hundreds. 
The Sertularia are also hydra polypiers. These have a horny 
stem, sometimes simple, sometimes branching. They might readily 
