. Elementary text-book of zoology. Zoology. CTENOPHORA. 263 bilaterally symmetrical, although each half possesses this property. The body is divided by these two perpendicular planes into four similar quadrants. Locomotion is principally effected by the regular vibration of the hyaline swimming plates, which are disposed over the surface of the body in eight meridional rows, in such a way that each quadrant possesses two rows of plates, a transverse and a sagittal (fig. 202). Locomotion is also assisted by the contractility of the muscle fibre* of the gelatinous tissue; this contractility in t
. Elementary text-book of zoology. Zoology. CTENOPHORA. 263 bilaterally symmetrical, although each half possesses this property. The body is divided by these two perpendicular planes into four similar quadrants. Locomotion is principally effected by the regular vibration of the hyaline swimming plates, which are disposed over the surface of the body in eight meridional rows, in such a way that each quadrant possesses two rows of plates, a transverse and a sagittal (fig. 202). Locomotion is also assisted by the contractility of the muscle fibre* of the gelatinous tissue; this contractility in the band-shaped Cestidce causes an undulating motion of the whole body. The mouth, which is sometimes surrounded by umbrella-shaped lobed processes of the gelatinous tissue, leads into a wide (Beroe) or narrow oesophageal tube, which in the latter case soon becomes flattened and broad. The cesophageal tube is furnished with two hepatic bands, and com- municates posteriorly, by an opening capa- ble of being closed by muscles, with the gastric cavity, or, as it is com- monly called, the in- fundibulum. The long cesophageal tube projects and opens freely into the infundibulum, and is completely surrounded by the gelatinous sub- stance, as far as the level of the two longitudinal vessels which accompany the two lateral surface-; in the transverse plane. The infundibulum, which is in all cases compressed in a direction at right angles to the oesophageal tube, gives oft' eight vessels to the swimming-plates. These vessels have a bi-radial symmetry. It also gives off two vessels, which are dilated into two terminal sacs; the latter surround the sense-organ at the aboral pole, which is known as vesicle, and each of them opens to the exterior by an orifice which is placed in a diagonal plane and is capable of being closed. Two tentacular vessels may arise from the bottom of the infundibulum. The internal surface both of the resophageal tube and of the infundibulum and its ves
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectzoology, bookyear1884
