120 PROF. OWEN ON A NEW SPECIES OF EUPLECTELLA. 



uot with strict regiilai'ity, but iu a sufficiently marked manner, and forming a rough 

 pattern of those wicker-baskets in AvMch the cross fibres are interwoven among the lon- 

 oitudinal ribs. Lastly, the transverse fibres lie below these, and are, on that account, 

 the least easily distinguished. Then the same series of longitudinal, oblique and trans- 

 verse lines is repeated, but more irregularly, until the walls of the cylinder acquire a 

 depth of 2'" at their thickest part, which occurs at about f ths of the entire length of 

 the specimen from its operculated end." — (A. F.) 



The average diameter of the longitudinal fibres of the cylindroid in Uuplectella 

 Cucumer is one-thirtieth of an inch : that of the transverse fibres is about one-fortieth 

 of an inch : these oblique fibres present much smaller and more varying diameters. All 

 these fibres consist of much finer fibrils, and these are composed of a delicate siliceous 

 sheath enclosing still more minute fibrillules. The component fibrils of Uuplectella 

 Cucumer, as in Uuplectella Aspergillum, are of two kinds ; one smooth, the other barbed 

 at pretty regular distances like the hair of certain caterpillars (PI. XXI. fig. 6) : and 

 some fibrils show both characters, and the gradual transition of the barbed to the smooth 

 part (fig. 7). In some of the barbed fibrils, which most abound in the resolved tuft of 

 attachment. Dr. A. Earre discovered a terminal convex disk, with a border divided into 

 four or five retroverted spines, simulating a small anchor : one of these is represented in 

 fig. 6. The same experienced microscopist found that he coidd frequently detach, with a 

 fine pair of forceps, from the exterior of the point of decussation of the oblique fibres, iu 

 the body of the cylindroid, minute multnadiate aciculi, like the one represented at fig. 5, — 

 one ray representing the axis, from which four other rays would diverge at right angles 

 and equal distances on the same plane. These " multiradiate spicula invariably consist 

 of six rays, viz. a perpendicular spine, which projects above the surface of the cylinder, a 

 small spiculum opposite to it which lies buried ia the mass, for the purpose apparently of 

 fixing the upper spiculum, and four basal rays (one very generally longer than the rest), 

 which take a direction always exactly correspondiag \^ith the lines of intersection of the 

 oblique fibres, with which they become blended." — (A. P.) These detached bodies may 

 have been the commencement of the new-forming oblique fibres in the gelatinous sub- 

 stance of the living Uuplectella. 



On applying the test of fire, by subjecting the fibrils of the Uuplectella Cucumer to the 

 flame of a candle, they generally splintered, and minute iridescent portions flew off in aU 

 directions. Some of these particles, being caught on slides of glass, showed under the 

 microscope that they were parts of a delicate sheath of silex : their iridescent hue seemed 

 to be due to the partially disintegrated constituent layers of siliceous matter entering 

 into the constitution of the sheath. Portions of fibrils, submitted in a test-tube to the 

 flame of a candle, were observed to splinter, sometimes with a slight bend ; and, on being 

 submitted to a half-inch objective in the compound microscope, showed the siliceous 

 sheath variously cracked or spHntered, enclosing a bundle of very minute fibrillules, witli 

 here and there a trace of charred gluten or organic matter. Submitted to the action of 

 dilute muriatic, or nitric, acid, the fibrUs underwent no other change than that of becoming 

 rather more clear or less opake ; and this without the extrication of bubbles, as from car- 

 bonate of lime, and witla not more evidence of any liberated gas than might be accounted 



