LECTURE XII, 203 



t 

 and shall begin with a genus of the smaller corals 



called Sertularia. The genus Sertularia is re- 

 markable for its vegetable appearance, and is po- 

 pularly considered as a kind of sea-moss. It is a 

 genus which contains a vast number of species, 

 some natives of our own coasts, and others exotic. 

 Most of the species are, when dried, of a pale, se- 

 mitransparent, yellowish-brown colour, and di- 

 vided into very numerous ramifications. In the liv- 

 ing or fresh state, the animal or Polype part may 

 be observed to fill the whole, both of the stem and 

 branches, and to send forth ahead, with several 

 arms, from every individual termination of the 

 numerous branches. The whole therefore may be 

 considered as a very compound or branched po- 

 lype, defended by an elastic, horny covering. In 

 the dried zoophyte the animal part shrinks up 

 and becomes obliterated ; the cortical part or case 

 alone remaining. One of the most elegant spe- 

 cies of Sertularia, and at the same time one of the 

 most simple in its structure, is the S. pinnata or 

 pinnated Sertularia, which is a native of our own 

 coasts, and is found adhering to rocks, and often 

 to oysters and other shell-fish : it seldom exceeds 

 the height of about two inches ; and its appear- 



