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Show 1868.] DR. J. S. BOWERBANK ON SPONGES. 1 19 all adopted the system of division and subdivision of these numerous and protean animals by means of their chemical constituents and their external forms ; and the results of their attempts at classification by such means have universally been unsuccessful in leading students to a ready recognition, or, indeed, to scarcely any recognition at all, of the species described by the authors who have had recourse to such systems. The natural result has been that every naturalist who has attempted to recognize the species of his predecessors has found himself to so great an extent unsuccessful, through the vagueness and uncertainty of the system that was to have been his guide, that he has therefore naturally commenced his career of the study and record of species unknown to him by a new method of arrangement, which, although perhaps sufficient for his own limited circle of subjects, becomes, when applied to a fresh series of them, quite as inapplicable to a general and extended view of these singularly protean forms as those of his predecessors. This was precisely the condition in which I found myself at the commencement of m y own career of investigation; and I naturally asked myself the question, Is there no means of escape from these various and inefficient modes of registering the examination of these animals, through a natural division of them into classes, orders, and genera, by means of their internal and external organization, after the manner pursued in other departments of zoology, and especially in botany 1 Strongly impressed with this idea, I commenced an investigation of a large collection of British and foreign species in m y own possession ; and I soon found that sponges, like other organized beings, were always provided with a skeleton, and that, as in other branches of zoology, the materials and mode of its structure varied very considerably in different species, and that those peculiarities of its structure were remarkably uniform and persistent through a considerable number of species in which they occurred. Here, then, was a foundation for the primary division of these creatures, in perfect accordance with the rules of zoological science as established by Linnaeus, Cuvier, and other laborious and talented authors of modern times ; and I had the satisfaction of finding that the more widely I extended m y observations the more uniform and certainly available these primary parts of the organization became ; and in addition to their characters of uniformity and constancy, there was this strong recommendation of them as bases for the foundation of classes, orders, and genera, that, however imperfect in form or dilapidated by external injuries or partial decomposition, the most persistent and last surviving part of the animal was always the skeleton. In botany and some branches of zoology the principal difficulty that meets the student is the correct determination of the genera; but this is not the case to so great an extent in the study of the Spon-giadae when their characters are founded on their structure and organization. As far as the genera have been established on these principles, they are so well marked, both by the material and the peculiar modes of the arrangement of their component parts, that they |
