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Show 1868.] DR. J. S. BOWERBANK ON SPONGES. 121 of the whole of the numerous vague and extraordinary alterations in the existing systematic arrangements of the Spongiadse proposed by him with a degree of hasty inconsideration that has led him into errors of omission and commission too numerous to be mentioned in detail ; I will not, therefore, attempt a minute critical examination of his new system of arrangement, but content myself with pointing out the prominent errors and inconsistencies of his plan. Thus, in page 493, he writes :-"The division between the calcareous and siliceous sponges is very distinct and natural; the separation between the siliceous and keratose sponges, on the other hand, is very indistinct and separates nearly allied genera." But he does not state what are the nature of these alliances ; nor does he seem to consider that the alliance must really be closer between sponges having spicula with calcareous or siliceous bases than between either and those having no spicula at all. And he then enumerates a series of distinctive characters belonging to the Spongiadse that are, upon the showing of his own descriptions of them, amply sufficient to establish each as a separate order or genus; and having done this, he concludes the paragraph thus : - " I believe it better to unite the siliceous and keratose sponges of these zoologists into one group or order." He then discusses the skeleton-spicula in the same loose manner, thus: - " The spicula that form the main part of the skeleton of these siliceous sponges are of three shapes :- "Fusiform (acerate, Bowerb.), more or less cylindrical, and pointed at each end. Needle-shaped (acuate, Bowerb.), cylindrical, blunt at one and sharp at the other end. Pin shaped (spinulate, Bowerb.), cylindrical, with a more or less spherical head and a tapering point,"- totally omitting to mention the true cylindrical form, plate 1. fig. 12, ' Monograph of British Sponges,' and entirely ignoring the first three primary forms of acerate, acuate, and spinulate, neither of which are fusiform in their typical forms, the fusiformity and the attenuation being merely secondary characters, or variations of the typical forms, and applicable alike to the whole four of them. The author then describes the whole of the auxiliary spicula of sponges in the same loose and hasty style. He writes-" The stellate are usually scattered in the sarcode; and the three-pronged are what Dr. Bowerbank calls tension and defensive spicula." This is quite incorrect as regards the "three-pronged" spicula, as I have never designated them as tension spicula, but always as defensive ones. He then proceeds thus-"The forms of the spicules are characteristic of the different families, if they are not always peculiar to them. Thus the many-rayed stellate, with rays on all sides, and the three-pronged or three-hooked elongate spicules are characteristic of the Geodiadce and Tethyadee. The anchorate and birotulate spicules and other forms of the series are almost peculiar to the family Esperiadce." These assumptions of Dr. Gray are also, to a great extent, erroneous. In the first place, I totally deny that " the forms of the spicules are characteristic of the different families." On the contrary, the primary skeleton forms are common to all of them ; the spicula are not characteristic even to a genus; and in |
