. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. Third and fourth cephalic rings of the Squilla : a, carapace; b, one of the posterior antennae j c, one of the mandibles. The eleven pairs of appendages which suc- ceed are variously apportioned between the functions of digestion and locomotion, to which last the five hindmost pairs are entirely dedi- cated in the Decapods. In other Crustacea, again, the first pair only is set apart in an especial manner for the office of mastication, all the others then serving for locomotion, and this pair is in consequence very genera
. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. Third and fourth cephalic rings of the Squilla : a, carapace; b, one of the posterior antennae j c, one of the mandibles. The eleven pairs of appendages which suc- ceed are variously apportioned between the functions of digestion and locomotion, to which last the five hindmost pairs are entirely dedi- cated in the Decapods. In other Crustacea, again, the first pair only is set apart in an especial manner for the office of mastication, all the others then serving for locomotion, and this pair is in consequence very generally de- scribed under the name of mandibles; very commonly one and even two other pairs are added to this first pair, and these are desig- nated jaws or maxilla. In the majority of instances, moreover, the three succeeding pairs assist the three preceding; and as they are frequently more especially apportioned to loco- motion, the two last in particular, whilst in some cases -they serve for the two functions at one and the same time, they have been de- signated by anatomists and naturalists the maxillary limbs (pieds-machoirs): these we shall describe when we come to speak of the apparatus of digestion. As to the five pairs which we have already mentioned as essentially ambulatory (see jig. 382), they present in the Brachyura no more than a simple stem, composed of six articulations; whilst in the Astacus and allied genera, we find a flabelliform appendage or whip, dedicated especially to the purposes of respiration, and in the Peneae the three sorts of appendages existing simultaneously. By- and-by, when speaking of respiration, we shall see how it happens that in a great number of these animals the whip of the thoracic extremities assumes a vesicular structure, and becomes the organ of this important function. The same peculiarity is observed in the appendages of the abdominal extremities of a great number of species; but among the members of the most elevated tribes, these
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