THE ANNALS ANf) MAGAZINE OF NATURAL HISTORY, [SECOND SERIES.] No. 82. OCTOBER 1854. XXIIT. — On the Mechanism of Aquatic Respiration and on the Sti'ucture of the Organs of Breathing in Invertebrate Animals. By Thomas Williams, M.D. Lond., Licentiate of the Royal College of Physicians, formerly Demonstrator on Structural Anatomy at Guy^s Hospital, and now of Swansea. [With three Plates.] [Continued from p. b^J !] Structure of the Branchice in the Lamellibranchiate Mollusks. The mist upon this branch of natural history which has survived the brightening science of a bright century may indeed refuse to be dissipated even by the achromatic microscope — the potent wand of the modern observer. That which the calm eye dis-cerns with clearness, and the understanding interprets with confidence, though amplified many hundred diameters, is as likely to be an immutable objective truth as any " instance " within the sphere of the unassisted vision. Faith in the verity of microscopic facts is a fundamental article in the scientific creed of every living philosopher. The sphere of the naked vision is exhausted : another is opened by the micro-scope. Minute descriptions of subtle and complex structures, rendered possible only through its instrumentality, will prove of as great service in the hands of the future lawgivers of science, as the grosser narratives of the fathers of anatomy have already proved in the founding of the temple in which the high priests of natural theology now chant her service. The branchial structures of the Mollusca have never yet been unravelled. The problem, though not impracticable, still awaits solution. The system of the gills is a conspicuous element in the molluscan organism. In apparent size they are considerable. Ann. ^ Mag. N. Hist. Ser. 'Z. Vol. xiv. IG
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