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Show 120 DR. J. S. BOWERBANK ON SPONGES. [Feb. 13, are certainly recognized by the aid of the microscope with greater decision and facility than those of many other branches of zoology or of botany. Having thus assigned the skeleton to the determination of genera, it became a question as to what parts of the organization were the most appropriate to the distinction of the species. Here, again, the lucid example of the great father of systematical botany, Linnaeus, naturally suggested the most advisable course of proceeding ; and the example that he set botanists in a rigid examination and a compendious nomenclature of those parts of the plant that were rather auxiliary and only occasional in their presence, and not absolutely necessary to the existence of a plant, naturally suggested the course to be pursued with regard to the determination of the species among the Spongiadse ; and first amidst these characters stood forth the spicula, the fit compeers of the leaves of plants in their great variety of form; and, like them, they are as widely distributed and as completely without reference to generic peculiarities. Other subsidiary organs in the sponges have also their value as specific characters, and have been thus applied accordingly ; but among these form and colour, the sheet anchors of the old modes of arrangement, are undoubtedly of the least value, from the perfectly protean character of the first, and the variable and evanescent peculiarities of the latter. M y first task, therefore, was to acquaint myself, as completely as I possibly could, with the various normal forms, and their varieties, of the spicula and their especial situations and peculiar offices in the animal economy. In aid of this object, I accumulated a vast number of specimens from various quarters of the world ; and as each peculiar form of spiculum became known to m e I had to record and distinguish it by a name, as I found no such thing as a systematic description or nomenclature of the organisms of the Spongiadse existing. H o w far I may have executed this task to the satisfaction of the scientific world I must leave time to decide, and, where necessary, to correct. In thus attempting to establish a nomenclature of parts hitherto undescribed, I have endeavoured to make these terms expressive of the forms and qualities of the organs in the same manner as the designations of leaves more or less describe their forms and the modes of their arrangement. But this one thing is certain, that without a definite nomenclature no descriptive science can hope to progress with any degree of precision or success. M y first application of the nomenclature thus formed was originally published in the ' Philosophical Transactions,' as I have before stated ; and it has been applied to the British species of sponges in my monograph of them published by the Ray Society. This work, Dr. Gray is of opinion, is not sufficiently distinct and definite in its descriptions to answer the required purpose ; and he seeks to remedy this defect by his proposed new mode of arrangement, which is based principally on the forms and peculiarities of the spicula, totally ignoring the skeleton as a means of arrangement into orders or genera. It would require almost a volume to discuss and expose the fallacy |