. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. The same, without the external or posterior max- illipedes. The branchiae contained in the two cavities, one on either side, whose conformation we have now described, are disposed along the vaults of the flancs. They are shaped like a quadran- gular pyramid, the base being fixed by means of a peduncle to the inferior part of tins vault or to the membrane which extends from its in- ferior edge to the basilar articulation of the corresponding limb; some of them are even inserted into this articulation. Each of these organs
. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. The same, without the external or posterior max- illipedes. The branchiae contained in the two cavities, one on either side, whose conformation we have now described, are disposed along the vaults of the flancs. They are shaped like a quadran- gular pyramid, the base being fixed by means of a peduncle to the inferior part of tins vault or to the membrane which extends from its in- ferior edge to the basilar articulation of the corresponding limb; some of them are even inserted into this articulation. Each of these organs consists of two large longitudinal vessels situated on the opposite edges of a transverse septum, which extends from the base to the apex of the branchia, and presents on each side a great number of lamel- lar or cylindrical pro- longations. Of these two principal vessels the external is the affe- rent one, of which men- tion has already been made in treating of the circulation and its organs; the internal again is the efferent vessel; the capillaries by which these two communicate run in the substance of the branchial lamellre, situated on either side of the median septum. In the whole of the Decapoda brachyura and anomoura, and in the greater number ofthema- croura, the folds of the tegumentary membrane which constitutes each branchia, are in the form of very thin lamellae, directed perpendi- cularly to the axis of the pyramid, and lying one over another like the leaves of a book. But in Crawfish, the Lobster, the Nethrops, the Palinuri, the Scyllari, and the Gebiae, these lamellae are replaced by a multitude of small cylinders, attached by their base, and closely packed side by side, like the bristles of a brush. The number of branchial pyramids varies greatly, especially in the Macroura; at the most it is twenty-two, as is the case in the Astacus and the most nearly allied species; in other macroura the number is eighteen, as in the Palinuri, Scyllari, Peneae; fifteen, as
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