Geological Society. 481 larity. It seems the cultivated Schizophytes change and de-velop more slowly, and probably on that account are less vigo-rous in producing mischief; at any rate, an inoculation with cultivated Swine-plague Schizophytes, although effective in producing the disease, is always followed by a comparatively milder form of Swine-plague than an inoculation with material directly from the body of a diseased hog.j^ This, however, does not involve that every inoculation with cultivated Schizo-phytes produces under all circumstances a milder form of Swine-plague tlian any natural infection ; for such is not the case. The difference may be stated thus : — A natural infec-tion, or an inoculation with material directly from the body of a diseased hog, as a rule, produces a malignant and dange-rous attack, and as an exception a mild form of the disease — the frequency of the exception depending, it seems, to a great extent, upon the prevailing character of the plague ; while an inoculation with the cultivated Schizo]:iliyte is, as a rule, followed by a mild attack, and, as an exception, or in rare cases only, by Swine-plague in its severest form. Wherever Swine-plague is prevailing in its most malignant or fatal form, or, what is essentially the same, wherever for-mation of ulcerous tumours in the ceecum and colon is afrequent occurrence, where consequently an abundance of Swine-plague Schizophytes is discharged with the excrements of the dis-eased animals, there the spreading from animal to animal, and from herd to herd, is a rapid one ; and vice versa, wherever the spreading is rapid, there ulcerous tumours in the intestines are a frequent occurrence. In 1878 the same (the ulcerous tumours) could be found in about 75 per cent, of all cases that had a fatal termination, while at present (in Illinois) their occurrence is probably limited to about 5 per cent, of all cases. PROCEEDINGS OF LEARNED SOCIETIES. GEOLOGICAL SOCIETY. February 23, 1881.— Robert Etheridge, Esq., F.R.S., President, in the Cliair. The following communication was read : — " On Astroconia Granti, a new Lyssakiue Hexactinellid from the Silurian Formation of Canada." By Prof. W. J. SoUas, M.A., F.G.S. This paper contained a description of a new fossil HexactineUid sponge from the Niagara chert beds of Hamilton, Ontario. It is
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