Page:Popular Science Monthly Volume 3.djvu/549

Rh Suppose we should take a skein of smooth, compactly-spun, glossy-white silk, about twenty-four inches in length, and, cutting the ends off evenly at one extremity, should give it a loose twist along the entire length, except some six inches at the bottom, which we leave, so to speak, frayed, or shaken out. Then around the other end of this silken cord or coil we affix a cup-like tuft of buff-colored zephyr worsted-work, having the end of the skein projecting a little higher than the rim, and covered with the same material. Now, from just below the base of the cup-like tuft, let us encase the white coil tightly down to where its threads fray out; let this cylindrical case be of a dark-brown color, and leathery aspect, and ornamented with little starry knobs or warts, like raised embroidery—and then, so far as form is concerned, you have the Hyalonema, or glass-sponge of Japan.

It thus appears from the above that the structure has three parts—the buff-colored mass at one end, the long shaft of white threads, and the star-embossed case which envelops the axis or shaft. Now, what



is the material nature of each part? There is no difficulty about the buff-colored mass, in form like a cup. It has the spicules, and the sarcode, which characterize the sponge-flesh. The axis or coil is of pure translucent silex, like white threads of glass. The surrounding sheath, with the starry prominences, is of a horny or keratose material, much like the stems of the sea-fans, and it is a curious fact that