. The physiology of reproduction. Reproduction. Jb'(ETAL NUTRITION: THE PLACENTA 385 It is not yet determined whether the yolli-sac placenta is functional till birth. According to Hill the wall probably breaks up before the end of pregnancy. The allantoic placenta, on the other hand, remains active, and at the time of birth some amn coe vase, til omph- Fig. 80.—Diagram showing arrangement of foetal membranes in Perameles. (From Hill, " The Placentation of Perameha," Qtuir. Jour. Micr. Sci., vol. xl., 1897.) amn, amnion ; , allantoic cavity ; , allanto-ohorio
. The physiology of reproduction. Reproduction. Jb'(ETAL NUTRITION: THE PLACENTA 385 It is not yet determined whether the yolli-sac placenta is functional till birth. According to Hill the wall probably breaks up before the end of pregnancy. The allantoic placenta, on the other hand, remains active, and at the time of birth some amn coe vase, til omph- Fig. 80.—Diagram showing arrangement of foetal membranes in Perameles. (From Hill, " The Placentation of Perameha," Qtuir. Jour. Micr. Sci., vol. xl., 1897.) amn, amnion ; , allantoic cavity ; , allanto-ohorionic mesenchyme ; , allantoic stalk; Ml omph, bilaminar omphalopleur; ch., marginal zone of true chorion around the allanto-chorionic area; coe, extra- embryonic ccelom ; , inner or chorionic wall of allantois; , persistent remnant of proamnion; st, sinus terminalis; , vascular omphalopleur; , yolk-sac cavity ; , invaginated yolk- sac splanchnopleur; ectoderm represented by thin line, mesoderm by dotted line, entoderm by thick line. maternal tissue is shed, while part of the fcetal tissue is left behind. The gestation period is about eight days. The aUantois in Perameles is of greater importance than in the opossum or Dasyurus ; but, relatively to the yolk-sac, it plays a smaU part in the nutrition of the embryo, as evidenced 2b. 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 Marshall, F. H. A. (Francis Hugh Adam), 1878-1949; Cramer, William, 1878-1945; Lochhead, James. London, New York, Longmans, Green
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectreproduction, bookyea
