BRYOZOA, OR SEA MOSSES. 127 



another class of these creatures, with an organization 

 quite different, though with an outward similarity in 

 the polypidom, namely, the Polyzoa, or, as they are as 

 commonly called, the Bryozoa, or Sea Mosses. In the 

 Anthozoa, the skeleton, whether horny or stony, has little 

 or no organic connection with the fleshy parts, to which 

 it acts as an internal support, or an external defence ; 

 for though secreted by the organs of the Zoophytes, 

 when it is once formed, it has no further capability of 

 development, and no circulation is maintained through 

 its substance. But in the Polyzoa, the polypidom con- 

 tinues to be, at all times, a living portion of the animal 

 which inhabits it. It is, in fact, a sort of hardened 

 skin, closely adhering to the Polype, and continuous 

 with its softer parts. None of the animals of this group 

 occur in a naked or separate form. They are all asso- 

 ciated in compound bodies, and lodged in cells, within 

 which, when at rest, the Polype lies concealed, doubled 

 up upon itself. They do not possess the remarkable 

 contractile powers of the Anthozoa, but when they re- 

 treat within their cells, they merely fold themselves 

 closely together. When expanded, the fore-part of the 

 body is protruded, exhibiting a mouth surrounded by a 

 circle of slender tentacula. The species of this class 

 are very numerous, but mostly of smaller size and less 

 beauty than those of the Anthozoa. A considerable 

 number are merely scaly crusts, adhering to the surface 

 of rocks and Algse. These, when carefully examined, 

 exhibit the beauty and regularity of structure insepa- 

 rable from the works of creation, but are commonly 

 passed over by the collectors of pretty things, as merely 



