240 THE MICROSCOPE. 



to the objects upon which it grows, and of a celliferous portion or 

 branches, upon which the polyps 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 disk, which thence exhibits something of the aspect of the body of 

 an ophiura. The radical tubes or branches springing from the margin 

 of the disk are usually live or six in number, and they are given off at 

 pretty regular distances apart j but besides these radical tubes, one or 

 more celliferous branches are not unfrequently seen to arise immedi- 

 ately from the upper surface of the discoid portion. 



The central disk, and the radical tubes arising from it, exhibit 

 a similar structure, and are formed of a thick, firm, apparently horny 

 envelope, containing a course granular matter, of a yellowish- white 

 colour, and which in some portions of the tubes assumes the form of 

 distinct irregularly-globular masses, of nearly uniform size. The cen- 

 tral disk is subdivided into distinct compartments by septa of consider- 

 able 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 the tube from which it springs. 

 This compartment is formed, like those of the central disk, by a thick 

 septum, which shuts off the origin of the secondary branch from the 

 main cavity of the primary one." 



The larger, or polypiferous cells, Mr. Busk proposes to term cells, 

 and the smaller tobacco-pipe-shaped organs cups; the latter being usually 

 above the former throughout the polypidom, " excepting immediately 

 below each fork, where the cup is invariably absent above one of the 

 cells of the pair from between which the fork springs. 



The polyp-cells are several times larger than the cups, and their 

 walls are much thinner ; in fact, sufficiently transparent to allow of 

 the contents of the cell being pretty well seen, without any prepara- 

 tion, even during the life of the animal. In shape they are inversely 

 conical, and the outer and upper angle is usually produced into a 

 prominent, sharp point. From the internal and upper angle arises 

 the tubular prolongation going to form the next cell or cup, as the case 

 may be, in succession. They are entirely closed at the top, contrary 

 to what is stated in all previous notices ; and, as has been shown, there 

 is no connection whatever between the cell and the cup placed imme- 

 diately above and behind it. The aperture of the cell is on the anterior 



