. On the anatomy of vertebrates [electronic resource] . ptiles. Itsexternal coat is thick, smooth, highly refracting— a true zonapellucida : the germinal vesicle is ?^th of an inch in diameter :the larger proportion of vitelline matter, rich in granules andoil globules, is the chief distinctive character of the mono-trematous ovum as a Mammalian one. I found two ovisacswith such mature ova in the left ovary of a female Ornithorhyn-chus, killed in September. In a specimen killed on the 6thof October (Yas River, New South Wales), the left ovary pre-sented two discharged and altered ovisacs. The
. On the anatomy of vertebrates [electronic resource] . ptiles. Itsexternal coat is thick, smooth, highly refracting— a true zonapellucida : the germinal vesicle is ?^th of an inch in diameter :the larger proportion of vitelline matter, rich in granules andoil globules, is the chief distinctive character of the mono-trematous ovum as a Mammalian one. I found two ovisacswith such mature ova in the left ovary of a female Ornithorhyn-chus, killed in September. In a specimen killed on the 6thof October (Yas River, New South Wales), the left ovary pre-sented two discharged and altered ovisacs. The ova from thesewere situated at the upper part of the left uterus, and at thedistance of about a line from each other. Each was spherical,and measured two lines and a half in diameter; the germ-mass,originally pale, had deepened to a yellow colour in the preservingliquor. The outer tunic had received no adventitious covering,but retained its smooth and polished exterior, and had not con-tracted any adherence to the uterine parietes. Each ovum was 565. Ovum from uterine end of the oviduct, with theaddition of a layer of albumen, Rabbit; diam. cclxi. 716 ANATOMY OF VERTEBRATES. imbedded in the soft, thick, plicated, smooth-surfaced, and well-organised lining membrane of the uterus. In a second Ornitho-rhynchus, shot in the same locality, on the 7th of October, theova, fig. 566, c, c, from the two discharged ovisacs, ib. b, b, were situated a little belowthe middle of the leftuterus ; they were alsospherical, each threelines in diameter, of alighter colour than thepreceding, specially atthe upper part, fromthe subsidence of thecontained vitelline orgerminal mass: theywere smooth,androlledfreely out of the posi-tion where they werelodged. In a third Left uterus impregnated, Ornitliorhynclius. LXXVII. °. specimen, shot on theevening on which the first specimen was obtained, the uterine ovumhad the same spherical form, smooth exterior surface, and freedomfrom connexion wit
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