. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. H/ytilus Edulis. F. Portion of a bar of the yill, with the cilia, highly magnified. in which also Purkinje and Valentin state that they observed it within the alimentary canal; and Gruithuisen* has described the phenomenon as seen on the branchiae of another fresh-water snail, which he names Valvata branchiata. He saw moving cilia, which caused an incessant agitation in the water; but he does not state whether the motion followed any constant direc- tion, although we may infer that this was the case. He rightly attribute
. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. H/ytilus Edulis. F. Portion of a bar of the yill, with the cilia, highly magnified. in which also Purkinje and Valentin state that they observed it within the alimentary canal; and Gruithuisen* has described the phenomenon as seen on the branchiae of another fresh-water snail, which he names Valvata branchiata. He saw moving cilia, which caused an incessant agitation in the water; but he does not state whether the motion followed any constant direc- tion, although we may infer that this was the case. He rightly attributed to these motions a respiratory function, but seems not to have observed that similar pheno- mena existed in other Mollusca. d. Pulmonifera. The ciliary motion is not confined to those Mollusca which breathe by gills, for it occurs also in the Lymnaea and Planorbis, which, though they live in water, breathe air by a pul- monary sac. In these instances the impulsion of the water takes place on the surface of the tentacula, which is covered with cilia. If these parts are to be regarded as organs of sensation alone, the ciliary motion observed upon them, as well as that which occurs on the tentacula of bran- chiferous species, must be considered as connected with the function of sensation; but the tentacula, which in the Lymnaea are broad vascular laminae, might be conceived also to perform the office of accessory organs of respiration, in which case the pulmoniferous Mollusca here mentioned would possess organs both of aerial and aquatic respiration. In the Lymnaea the motion has also been observed by Purkinje and Valentin within the alimentary canal. B. Conchiferous —The motion in question has been found in several bivalve Mollusca, both of salt and fresh water, and there can be little doubt that it exists in all. The common Sea-mussel (fig. ) will serve as an example of the class. It will be recollected that the gills of this animal (fig. A, r, c', d,) have th
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