Glass Sponge, Or Glass Hope a silicious sponge of the genus hyalonema (Gray); the name may also be properly applied to other allied genera, and especially to the euplectella, which will be described under Venus's Flower-Basket. This sponge was first described and named by Dr. J. E. Gray, of the British museum, in 1835; he regarded it as a coral allied to the sea fans (gorgonia), an opinion to which he still adheres, against what seems to be an overwhelming mass of evidence. As usually seen, this sponge consists of a loosely twisted bundle of glassy threads, diverging at one end and converging at the other, which is more or less covered with a brown crust, studded with wart-like cylindrical elevations, terminating in radiating ridges. The threads are mainly composed of silex, and are shining, translucent, and very flexible; the fascicle varies from 12 to 20 in. in length, and is about half an inch thick, the threads ranging from the size of a bristle to that of a knitting needle. The wart-like elevations are generally regarded as polyps, of the genus palythoa, continuous throughout the crust, of which Dr. Gray considers the fascicle the central axis. The convergent end, in its natural state, is enveloped in a spongy mass, the fascicle on which Dr. Gray regarded as a parasite.
The opinions of scientific men since Gray have been various. Prof. Brandt of St. Petersburg considered the sponge a parasite attaching itself to the polyp mass and gradually destroying it. Dr. Bower-bank regards all the structures above named as parts of one sponge, the wart-like elevations being the oseula. Prof. Schultze of Bonn represents the fascicle and the sponge mass as belonging together, the warty crust being referred to the polyp palythoa. Ehrenberg regards the fascicle as an artificial product of Japanese industry, and all sponges as of vegetable nature. In 1807 Prof. Loven described a little, stalked, deep-sea sponge from the coast of Norway, the H. boreale, which led him and naturalists since to the belief that this sponge had been represented upside down; in fact, that the glassy threads were below, mooring the structure to the sand, mud, or weeds, the sponge mass forming the upper portion; an opinion which Dr. Leidy in 1870 modified by suggesting that this sponge may be suspended by its glassy cable, thinking it highly improbable that it should be attached by or rest upon the base where the large oseula are placed.
All agree that there is a sponge mass attached to this compound animal, as the microscopic structure of the threads is perfectly characteristic of sponge spicules; their silicious character shows that they are not formed by polyps; the sponge mass at the upper end consists of an elegant tissue of dense masses of very short silicious spicules, forming a kind of felt; the terminal sponge is more or less cup-shaped, with an open conical central cavity. All hut Dr. Bower-bank admit a parasite, the question being whether the polyp is a parasite on the sponge, or the sponge a parasite on the polyp. The characters of hyalonema will he best understood from the annexed figure. II. mira-bile or Sieboldi is found in the seas around Japan, near Yokohama; II. Lu-sitanicum was found by Prof. Bocage of Lisbon off the coast of Portugal; II. boreale, according to Wyville Thompson not belonging to this genus but to a corticate type, was found by Prof. Loven on the coast of Norway; and this or an allied species has lately been dredged on the northern part of our own coast.
Other glass sponges are Holtenia, figured in the "American Naturalist" for July, 1873, and pheronema and rossella, figured in the " Popular Science Monthly " for September, 1873. Where men like Gray, Bow-erbank, Brandt, and Schultze entertain such different opinions, after the examination of hundreds of specimens, during a period of nearly 40 years, it is certainly very difficult to decide whether hyalonema be wholly a sponge, or which, if either, the sponge or the polyp, is the parasite. Dr. Leidy, in the "American Naturalist" for March, 1870, alludes to a specimen, very much like one in the possession of the writer of this article, in which the fascicle appears to have been withdrawn from the sponge and lain for some time in the sea; a shark's egg is also attached near the top, and the tendrils of others are partially imbedded in the crust, which has no warty elevations; this seems to favor Dr. Bowerbank's opinion that the whole is a sponge, and that the crust is not made by a polyp.
Glass Sponge (Hyalonema Lusitauicum).