* 
120 PROF. OWEN ON A NEW SPECIES OF EUPLECTELLA. 
not with strict regularity, but in a sufficiently marked manner, and forming a rough 
pattern of those wicker-baskets in which the cross fibres are interwoven among the lon- 
gitudinal 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 $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 Æuplectella 
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 Zuplectella 
Cucumer, as in Euplectella Aspergillum, are of two kinds; one smooth, the other barbed 
at pretty regular distances like the hair of certain caterpillars (Pl. 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. Farre 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 could frequently detach, with a 
fine pair of forceps, from the exterior of the point of decussation of the oblique fibres, in 
the body of the cylindroid, minute multiradiate 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 spieulum opposite to it which lies buried in 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 corresponding with the lines of intersection of the 
oblique fibres, with which they become blended."—(A. F.) These detached bodies may 
have been the commencement of the new-forming oblique fibres in the gelatinous sub- 
stance of the living Euplectella. ; 
On applying the test of fire, by subjecting the fibrils of the Zuplectella Cucumer to the 
flame of a candle, they generally splintered, and minute iridescent portions flew off in all 
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 splintered, enclosing a bundle of very minute fibrillules, with 
here and there a trace of charred gluten or organic matter. Submitted to the action of 
dilute muriatic, or nitric, acid, the fibrils 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 with not more evidence of any liberated gas than might be accounted 
