Elementary text-book of zoology (1884) Elementary text-book of zoology elementarytextbo0101clau Year: 1884 Gf i: FIG. 14a.—Acalepha larva (Ephyra). Jtk, marginal body ; Gf, gastric fila- ment. Re, radial-canal; O, mouth. FIG. 14b. — Ctenopheran seen from above. S, sagittal plane; T, trans verse plane ; R, vibratile plates ; Gf, gastric canals. In the bilateral arrangement, which is found also in each individual antimere of the Radiata, only one plane, the median plane, can be imagined, which passes through the chief axis and divides the body into two exactly similar parts (right and left). Th
Elementary text-book of zoology (1884) Elementary text-book of zoology elementarytextbo0101clau Year: 1884 Gf i: FIG. 14a.—Acalepha larva (Ephyra). Jtk, marginal body ; Gf, gastric fila- ment. Re, radial-canal; O, mouth. FIG. 14b. — Ctenopheran seen from above. S, sagittal plane; T, trans verse plane ; R, vibratile plates ; Gf, gastric canals. In the bilateral arrangement, which is found also in each individual antimere of the Radiata, only one plane, the median plane, can be imagined, which passes through the chief axis and divides the body into two exactly similar parts (right and left). These two halves, as opposed to antimeres, may be termed parameres. In bilateral animals we distinguish an anterior and posterior end, a right and a left side, and a dorsal and a ventral surface. The unpaired organs are placed in the middle line, on each side of which, in the two halves of the body, are placed the paired organs. The plane which is placed at right angles to the median plane (passing from right to left) and separates the unlike dorsal and ventral halves of the body, is known as the lateral plane. The anti- meres of the Radiata also consist of two parameres, and are therefore bilateral, in that the vertical plane passing through the radius like the median plane divides them into two similar parts. The same groups of organs or similar parts of the same organ may also be repeated in a longitu- FIG. is.—segmented dinal direction. This occurs especially frequently ''°™ (p°iychaete). . r • l P>>. pharynx; D, ali- in bilateral, less frequently in radiate animals mentary canal; c, (strobUa). The body thus obtains a segmentation, cirms; F' teutacle- and is divisible into successive sections, the segments or metameres
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