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Show 130 DR. J. S. BOWERBANK ON SPONGES. [Feb. 13, Sicily by Mr. Topping and was presented to me by him. Now the question arises, which of these new genera and species are to stand ? are either or neither? Common sense would answer, the latter. One would naturally imagine that this facility in creating genera could not be carried to a more absurd extreme; but, strange as it may appear, under the ingenious manipulation of Dr. Gray, that is really the case, as in page 544, the genera and species, 14. Acarnus innominatus, and 15. Fonteia anomala are actually founded on one form of spiculum hitherto only found on one undescribed species of sponge. Acarnus innominatus is derived from fig. 292, pl. 18, 'Mon. Brit. Sponges,' representing a portion of the reticulated skeleton of the sponge with the radiating fasciculi of spinulo-quaternate internal defensive spicula in situ; while Fonteia anomala is based on the figures 73-76, pl. 3, of the same work, representing the various stages of development of the same spinulo-quaternate spicula as those represented in situ in pl. 18, and which various forms are described by me in page 239, ' Mon. Brit. Spongiadse,' as different stages of development of the perfect form represented by fig. 76, and the reader is referred to pl. 18. fig. 92, in the same description, for a view of them in situ. Comment on such a case as this is superfluous; and, strange though it be, the author, with their descriptions before his eyes, describes them as "spicules of four kinds." If the author should steadily pursue the course described in the last cases we may ultimately arrive at the unforeseen and rather extraordinary conclusion that not only may single species represent a genus, but an individual may really be composed of a group of genera and species. I will now endeavour to show the mischievous consequences, to closely allied and well-established genera, arising from Dr. Gray's mode of founding his new genera on peculiarities of form in the various auxiliary spicula of sponges, which are only present in certain species, and which vary more or less in form, combinations, and mode of disposition in almost every species in which they are found, instead of basing his generic characters on the more substantial and enduring characters afforded by the anatomical peculiarities of the skeleton. I will not comment on every instance in which his mode of proceeding has been highly detrimental to our power of discriminating species, but I will select a few only of the most illustrative ones. Thus in the genera Tethea and Geodia we have two of the most natural and most accordant groups of species among the whole of the Spongiadse, groups which all naturalists have hitherto concurred in preserving entire. Let us see how the author proposes to treat them. In the first place, Dr. Gray, in page 543 of his paper, misquotes both Dr. Johnston's ' History of British Sponges,' page 85 (or, more correctly, 83), and m y 'Monograph of British Spongiadse,'vol. ii. page 83, making us each to have adopted the term Tethya, whereas both have rejected that name and adopted Lamarck's name Tethea, for the very good reasons given by Dr. Johnston in page 83 of his work. Dr. Gray separates Johnston's two species T. cranium and T. lyncurium, leaving the former as the type of his Tethya, page 543, |