| OCR Text |
Show 1867.] DR. J. E. GRAY ON HYALONEMA LUSITANICUM. 123 the small end of the coral, which in the Japan species is sunk in the sponge, covered with polypes like the rest of its surface. Professor M a x Schultze, who regards the coil of the Japanese species as part of the sponge and the polypes as a parasitic species of Palythoa, considers the polype an undescribed species of that genus. But the observation of Professor Brandt shows that it differs from all the species of the genus Palythoa in having the inner layer of the basal portion, which forms the bark of the coil and the cells of the polypes, strengthened with siliceous spicula, similar to, but smaller and shorter than the spicula of the coil; so that the animal must form a genus by itself, which has the peculiarity of secreting small spicules of the same kind and form as those which the advocates of the parasitic theory will not admit the polype secretes of a larger size so as to form the coil. According to the observations of Professor Bocage, the polype of the Portuguese species differs from that of the Japan species in having a different number of tentacles ; but it agrees with the Japan species in the inner layer of the corium secreting siliceous spicules. So the Hyalonemata of the two localities have polypes agreeing in forming siliceous spicules in the corium, and yet may be referred to different genera. Yet we are to believe that each is only parasitic on a coil of spicules which only differs from the spicules of their flesh in being larger and formed into a central coil! This I must regard as a very illogical conclusion, as it is more natural to suppose they secrete the spicules of the bark and the coil. These two genera, according to the theory entertained by Valenciennes, Milne-Edwards, and Wyville Thompson, must belong to two very different groups of animals. These zoologists consider the "glass rope," because it grows out of a sponge* having somewhat similar siliceous spicula, to be only an extraordinary development, of the spicula of tbe sponge, which is covered with a parasitic Palythoa ! Therefore they regard it as a sponge. As the second genus does not grow out of a sponge, and therefore cannot be a development of the sponge-spicula, and therefore cannot be a sponge, I do not know to what group of animals they would refer it. I therefore think it much more reasonable to believe that both belong to a peculiar group of zoanthoid corals characterized by secreting an axis formed of siliceous thread-like spicules, consisting at present of two genera, one living free, and the other growing from a mass of sponge. Thus a coral with an axis formed of a coil of siliceous spicules, exactly similar to that of Hyalonema, is found without being in connexion with any sponge; so that the coil cannot be a special development of the spicules of a certain sponge. In the latter case the coil-like axis is evidently secreted by the polypes which cover it. Are we to believe that the sponge forms the axis in one case, and * Professor Brandt denies that the Japan Hyalonema lives in a sponge (Hyalonema, p. 14, note), and says he does not know how they are fixed (p. 14). Professor Max Schultze figures three specimens in sponges (t. 1, 2). W e have two examples in the British Museum in sponges; and I have seen more than a dozen other specimens all growing in sponges. |
