. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. B Polype of a Flustra in its cell. he here, as in other cases, denies the existence zoophyte (fig. 293, A, B) has a creeping stem of cilia. b. Marine Polypi.—The polypi of marine Fig. 293. Zoophytes, on which observations relating to the present subject have been made, may for our purpose be conveniently arranged under three principal forms. The first form of polype (fig. 292) is found in Flustrae and cellular polypi generally; it ex- ists also in some spe- cies which have been classed among the Ser- tularias, and probab
. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. B Polype of a Flustra in its cell. he here, as in other cases, denies the existence zoophyte (fig. 293, A, B) has a creeping stem of cilia. b. Marine Polypi.—The polypi of marine Fig. 293. Zoophytes, on which observations relating to the present subject have been made, may for our purpose be conveniently arranged under three principal forms. The first form of polype (fig. 292) is found in Flustrae and cellular polypi generally; it ex- ists also in some spe- cies which have been classed among the Ser- tularias, and probably prevails very extensively in different tribes of Zoophytes. The body (a, b, c), which is gene- rally contained in a cell, is bent on itself, some- what like the letter Y or V; the one branch (a) being the mouth and throat, the other (b) the rectum opening by an anus, and the middle part (c),which is of a dark and often of a brown co- lour, being the stomach probably with some accessory organ. The mouth is surrounded with a variable number of long straight ten- tacula or arms, fringed on both of their lateral margins with cilia. When the arms are ex- panded, the cilia are thrown into rapid motion, which has the appearance of undulations pro- ceeding along the fringes, upwards on one side of the arm or from its root to the point, and downwards on the other. While the cilia are thus moved, they produce currents in the water, as described in the Fresh-water Polype, and here also the currents in all probability serve for respiration and the prehension of food. Besides these motions in the water in the neighbourhood of the tentacula, a revolving motion of particles is observed within the body : small particles of extraneous matter which enter the throat are moved round within it; and the contents of the stomach and rectum undergo a very singular revolving motion round the axis of the cavity. These internal motions, Dr. Grant conjectured, might be owing to internal cilia; and I
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