NULLIPORES. 155 



character, whose outward coating and much of whose 

 interior fabric, are composed of carbonate of lime, se- 

 creted in their cells, and forming an organized portion 

 of their bodies. Vegetables of this class bear a striking 

 resemblance to the skeletons of some of the larger cal- 

 careous Zoophytes, especially to some of the Celleporse j 

 but they may always be known from true Zoophytes 

 by the absence of pores, or polype-cells, in the surface ; 

 and when their structure is carefully examined with a 

 microscope, their vegetable nature is still more obvious. 

 To examine one of the Nullipores, it is necessary that 

 a portion of the specimen intended for examination be 

 first macerated for some time in dilute muriatic acid. 

 This will dissolve the opake carbonate of lime which 

 fills the cells, and leave the tissue iu a state in which 

 minute portions of it may readily be dissected, and 

 placed under the microscope. It will then be found of 



NOLLIPORES 



a nature precisely similar to the cellular tissue of other 

 Algse. In their outer aspect the Nullipores are of very 

 various characters. Some of them resemble Lichens in 

 form, being thin as paper, expanding into leafy lobes, 

 and forming circular patches on the surface of rocks. 

 In others the leafy lobes stand erect, or are laid one 



