. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. Head of the Maja Squinado. a, afferent opening of the branchial cavity ; b, carapace •, c, anterior extremities ; d, posterior maxillipedes. This canal runs forwards, passes to the out- side of the oral apparatus, and terminates in front of the mouth (g,fg- 428). In its interior there is a large valve, which is falling and rising continually, as if it moved upon a pivot, and which in this way occasions a rapid current. The same parts, the posterior maxillipedes and a por- tion of the carapace having been removed. a, affe
. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. Head of the Maja Squinado. a, afferent opening of the branchial cavity ; b, carapace •, c, anterior extremities ; d, posterior maxillipedes. This canal runs forwards, passes to the out- side of the oral apparatus, and terminates in front of the mouth (g,fg- 428). In its interior there is a large valve, which is falling and rising continually, as if it moved upon a pivot, and which in this way occasions a rapid current. The same parts, the posterior maxillipedes and a por- tion of the carapace having been removed. a, afferent opening; d, portion of the posterior maxillipedes ; e, commencement of the efferent canal (f)g, the termination of the efferent canal; h, the valve. from behind forwards in the water with which the cavity is filled. This valvular apparatus is neither more nor less than the flabelliform appendage of the second pair of maxillipedes which acquire dimensions in relation with the importance of the new function they have here to perform (h,fg. 428). In the long-tailed Decapoda, and in the greater number of Anomoura of the same family, the respiratory cavity is open along the whole extent of its inferior edge; the carapace is not applied accurately to the lower margin of the vault of the flanc, and it is by the empty space thus left above the base of all the extremities that the water makes its way to the branchiae. In the Brachyura the afferent orifice of the branchial cavity is more circumscribed, but varies in a still greater degree. In nearly all the Crustacea it exists almost immediately in front of the base of the first pair of ambulatory extremities, and con- sists of a kind of cleft, of considerable breadth, which in this place occurs between the edge of the carapace and the thorax (a, fg. 427), and which is occupied by a prolongation of the ba- silar joint of the external maxillary limb (d\ disposed in such a manner as to close it com- pletely or to open it at the des
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