. The chordates. Chordata. Via ilia: Visceral System 649. Y(Jlw) y a Fig. 491. Urinogenital organs of marsupials. (A) A young opossum {Didelphys dorsigera). (B) Phalangista vulpina. (b) Urinary bladder; (67) cloaca; (g) clitoris; (n) kidney; (Od) Fallopian tube; (0/ (Fim)) fimbriated abdominal opening of ovi- duct; (Ov) ovary; (r) rectum; (r1) anus; (Sp) septum; {Sug) urinogenital sinus; (Ur) ureter; (Ul) uterus; (Ut1) openings of uteri into vaginal cecum; (Vg) vagina; (Vg1) vaginal opening into urinogenital sinus; (VgB) vaginal cecum; (t) junction of uterus and vagina; (*) rectal gland. (Cour
. The chordates. Chordata. Via ilia: Visceral System 649. Y(Jlw) y a Fig. 491. Urinogenital organs of marsupials. (A) A young opossum {Didelphys dorsigera). (B) Phalangista vulpina. (b) Urinary bladder; (67) cloaca; (g) clitoris; (n) kidney; (Od) Fallopian tube; (0/ (Fim)) fimbriated abdominal opening of ovi- duct; (Ov) ovary; (r) rectum; (r1) anus; (Sp) septum; {Sug) urinogenital sinus; (Ur) ureter; (Ul) uterus; (Ut1) openings of uteri into vaginal cecum; (Vg) vagina; (Vg1) vaginal opening into urinogenital sinus; (VgB) vaginal cecum; (t) junction of uterus and vagina; (*) rectal gland. (Courtesy, Wiedersheim: "Grundriss der vergleicbenden Anatomie der Wirbeltiere," Jena, Gustav Fischer.) divides the vaginal chamber and its cecum. In some kangaroos the vaginal cecum grows backward and acquires a median opening into the urinogenital sinus, the extraordinary result being three vaginal passages extending between the urinogenital sinus and the two uteri. The deficiencies of the internal uterine arrangements in marsupials are compensated for by provision for continuation of maternal care and feeding after birth of the young. The minute and helpless newborn fetus is transferred to an external posteroventral pouch, the marsu- pium, formed by a fold of abdominal skin (Fig. 539). The pouch is supported by a pair of elongated epipubic or marsupial bones which project forward from the anterior bones, pubes, of the pelvic girdle. The epipubes, like the pubes, are cartilage-bones. The mammary glands are on the abdominal wall within the pouch. The marsupium is present only in the female. In most cases it opens forward. In the bandicoots (Perameles and Chaeropus) and the marsu- pial mole (Notoryctes) it opens backward. The reversal in the direction of the opening is a very fortunate adaptation to the burrowing habit. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of t
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