POLTZOA. 515 



the bracket of a shelf, broad at top and narrow at the 

 bottom : these are placed back to back in pairs, one above 

 another, on an extremely slender tube that seems to 

 run through the middle of the branches of the whole 

 coralline. The cells are open at top. Some of them have 

 black spots in them ; and from the top of many of them 

 a figure seems to issue out like a short tobacco-pipe, the 

 small end of which seems to be inserted in the tube that 

 passes through the middle of the whole. The cells in pairs 

 are thought by some to have the appearance of the small 

 I ods of the plant " Shepherd's Purse," by others the shape 

 ut the seed-vessel of the Veronica, Speedwell. 



' The polypidom of this bryozoon, like those of most of 

 ils congeners, may be said to consist of a radical portion, 

 by which it is affixed to the objects upon which it grows, 

 and of a celliferous portion or branches, upon which the 

 polypes themselves are lodged. The radical portion in the 

 present species consists of a central discoid body of a 

 nearly circular form, and of branches radiating from the 

 periphery of the disc, which thence exhibits something of 

 the aspect of the body of an ophiura. The radical tubes 

 or branches springing from the margin of the disc are 

 usually five or six in number, and they are given off at 

 pretty regular distances apart ; but besides these radical 

 tubes, one or more celliferous branches are not unfrequently 

 seen to arise immediately from the upper surface of the 

 discoid portion. 



" The central disc, and the radical tubes arising from it, 

 exhibit a similar structure, and are formed of a thick, firm, 

 apparently horny envelope, containing a coarse granular 

 matter, of a yellowish-white colour, and which in some 

 portions of the tubes assumes the form of distinct irregu- 

 larly-globular masses, of nearly uniform size. The central 

 disc is subdivided into distinct compartments by septa of 

 considerable thickness, and each radiating branch arises 

 from one of these distinct compartments; so that there 

 appears to be no communication between one radical 

 branch and another. The radical branches give off at 

 irregular distances secondary branches, which ultimately 

 become celliferous. Each of these secondary branches, 

 however, arises from a distinct compartment, as it were, of 



LL2 



