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Show 502 DR. J. E. GRAY ON S P O N G E S . [May 9, having perfect faith in Mr. W. Lens Aldous's accuracy. I can speak of the accuracy of the plates of both these authors from the result of m y own observations ; and having full reliance on them, they seem to be as available for m y purpose as if I had myself repeated all their researches. The arrangement here proposed is to be regarded as an attempt to divide the sponges into groups and genera, so as to enable tbe student to discover the name and alliance of the species under his examination, which I have been repeatedly told the [preceding systems have failed to effect. It is only a prodromus, and a very imperfect one, requiring revision, correction, and extension. For example, the large reticulated horny sponges, which form the greater part of collections in museums, and the external forms of which have been figured in Esper's, Duchassaing and Michellotti's, and several other zoological works, require to be microscopically examined and systematically described. The British Museum have received from Dr. Oscar Schmidt typical specimens and preparations of the spicules of almost all the species he has described from the Adriatic Seas. The class is divisible into two subclasses, according to the chemical constituent of the skeletons; in one the spicules are calcareous, and iu the other when present siliceous, or more or less mixed with a horn-like animal material. Subclass 1. PORIPHORA SILICEA. The sponges provided with a siliceous or horny skeleton, or with a horny skeleton strengthened with siliceous spicules. Porifera keratosa et P.chalinida, "Grant, Tabular View, 1861;" Bowerbank, B. Sponges, i. p. 154. Porifera silicea etP. keratosa, Bowerbank, B. Sponges, i. pp. 155, 166. SYNOPSIS OF FAMILIES. Section I. MALACOSPOR.E (Soft-spored Sponges). Reproduction by ova contained in a thin membranaceous ovisac not strengthened by siliceous spicules or by gemmules, scattered in the substance of the sponge. Subsection 1. Netted Sponges (DICTYOSPONGILE). Skeleton formed of a continuous siliceous or horny network. Order I. CORALLIOSPONGIA. Sponges hard, coral-like, entirely formed of siliceous spicules anchylosed together by siliceous matter into a network. Mass covered with a thin coat of sarcode when alive. Fam. 1. DACTYLocALYCiDiE. Sponge massive, expanded or flabellate, reticulate, angular. |
