. Elementary text-book of zoology, tr. and ed. by Adam Sedgwick, with the assistance of F. G. Heathcote. Gf possess an cesophageal tube and a gastro-vascnlar canal system. Two lateral tentacles, ichich can be retracted into pouches, are often present. The Ctenophora possess a shape which can in all cases be reduced to a sphere. They are radially symmetrical free-swim- ming Cadenterata of gelatinous consistence. The body is often bilaterally compressed, so that it is possible to distinguish two planes passing through the long axis at right angles to one an- FIB. 201.—Cydippe, seen from the apic
. Elementary text-book of zoology, tr. and ed. by Adam Sedgwick, with the assistance of F. G. Heathcote. Gf possess an cesophageal tube and a gastro-vascnlar canal system. Two lateral tentacles, ichich can be retracted into pouches, are often present. The Ctenophora possess a shape which can in all cases be reduced to a sphere. They are radially symmetrical free-swim- ming Cadenterata of gelatinous consistence. The body is often bilaterally compressed, so that it is possible to distinguish two planes passing through the long axis at right angles to one an- FIB. 201.—Cydippe, seen from the apical pole.' S, Sagittal plane; T, Other ; these transverse plane; R, swimtring ^Yethesaqit- platcs ; Gf, gastro-vascular system. tal plane and the transverse plane, and are analogous to the median (longitudinal vertical), and lateral (longitudinal horizontal) planes of bilaterally symmetrical animals (fig. 201). The arrangement of the internal organs bears a relation to these two planes. All parts of the body which occur in pairs, as the two tentacles, the gastric canals, the hepatic bands of the stomach, and the vessels which give origin to the eight lateral canals, all lie in the transverse plane, while the sagittal plane coincides with the longer axis of the ossophageal (gastric) tube (whence also called the gastric plane), the two so- called pol :r-fields, and the terminal vessels of the infundibulum. The infundibulum is so compressed that Flo. its longest diameter falls in the lateral plane, which on this account is sometimes called the infundibular plane. Since these two planes divide the body into halves, which correspond with one another, and since there is no division into dorsal and ventral surfaces, the arrangement of the body may be said to be bi-radially symmetrical, but cannot be called. - °-. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illust
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