. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. 706 CONCHIFERA. branchiae are included. It is in this palleal sac that the animal establishes a current, of water, destined to minister to the function of respiration, and to carry towards the mouth the alimentary particles with which it is fed. The median parts of the lobes of the mantle are ex- tremely thin and transparent, and a great number of vessels (c, Jig. 362), and a few nervous filaments (7, 8,^.360) are perceived ramifying through their substance, and running towards the anterior and inferior edges. These edge
. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. 706 CONCHIFERA. branchiae are included. It is in this palleal sac that the animal establishes a current, of water, destined to minister to the function of respiration, and to carry towards the mouth the alimentary particles with which it is fed. The median parts of the lobes of the mantle are ex- tremely thin and transparent, and a great number of vessels (c, Jig. 362), and a few nervous filaments (7, 8,^.360) are perceived ramifying through their substance, and running towards the anterior and inferior edges. These edges, which extend as far as those of the shell, are thickened, and it is at the point where the thickening begins that the mantle adheres to the shell by means of a great number of minute muscles (/, /, Jig. 347; d,fig. 362), which leave a linear impression upon it. The thickening of the edges of the mantle is owing to the pre- sence of a great quantity of muscular fibres, fre- quently to several rows of contractile tentacular cilia (m,m, fig. 347; e, Jig. 361 & 362); and, lastly, to that of an organ, which is the secerning apparatus of the shell. The muscular fibres are Contractile cilia magnified. distributed some to the edges of the mantle, and others to the tentacula with which it is fringed. The whole of these parts are extremely retractile, and are endowed with such sensi- bility that the slightest contact is perceived, as is evinced by their instantaneous contraction. Zoologists have taken advantage of certain modifications in the lobes of the mantle to establish divisions in their methodical arrange- ments of the conchifera. This artificial means is sufficiently convenient, inasmuch as no anatomical inquiries are necessary in order to get at the distinguishing characters which these modifications supply. Latreille, in his ' Fa- milies du Regne Animal,' as well as other zoologists, have also made use of the conjunc- tion or disunion of the lobes of the mantl
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