. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. Figure 5. Large pericardia! space and heart in primitive molluscs. (A) Aplacophoran, Chaetaderma nitidulum, sagittal section. Gametes pass from the gonads through the pericardium with its large, paired, lateral extensions ("horns") and thence into gametoducts leading to the mantle cavity (from Scheltema. 1973, fig. 2, and Scheltema, 1988, fig. 13). (B) Polyplacophoran, Chiton sine/am, cross section (after Wissel, 1904, pi. 24, fig. 49). (C) Monoplacophoran. Neopilina galathea. dorsal view, with paired pericardia! s
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. Figure 5. Large pericardia! space and heart in primitive molluscs. (A) Aplacophoran, Chaetaderma nitidulum, sagittal section. Gametes pass from the gonads through the pericardium with its large, paired, lateral extensions ("horns") and thence into gametoducts leading to the mantle cavity (from Scheltema. 1973, fig. 2, and Scheltema, 1988, fig. 13). (B) Polyplacophoran, Chiton sine/am, cross section (after Wissel, 1904, pi. 24, fig. 49). (C) Monoplacophoran. Neopilina galathea. dorsal view, with paired pericardia! sacs, paired ventricles, and two pairs of auricles (after Lemche and Wingstrand, 1959, from Scheltema, 1988, fig. 13). (D) Polyplacophoran, Acanlhopleiira echinata, dorsal view, with two pairs of openings between auricles and ventricle (after Plate, 1898. from Scheltema, 1988. fig. 13). 1 pericardium, 2 ventricle, 3 auricle, 4 opening between auricle and ventricle, 5 auriculoventricular valve, 6 aortal bulb, 7 gonopericardial duct, 8 lateral extension of pericardium, 9 gametoduct. Development ofmesoderm The interpretation that the coelom is reduced in Mol- lusca assumes that the molluscan pericardium is homol- ogous to the coelom in other spiralian coelomates, namely Annelida and Sipuncula. In all three, the coelom is formed from mesoderm that originates from embryonic cell 4d. This cell gives rise to a pair of mesodermal teloblasts, which migrate inward to a ventrolateral position, one on each side of the midline (Verdonk and van den Biggelaar, 1983; Anderson, 1973; Rice, 1975) and proliferate forward into two lateral mesodermal bands. Mesodermal bands. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Marine Biological Laboratory (Woods Hole, Mass. ); Marine Biological Laboratory (Woods Hole, Mass. ). Annual
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
