. On mammalian descent. Being nine lectures delivered in the theatre of the Royal College of Surgeons during February, 1884. Mammals. Xect. III.] EMBRYO OF OPOSSUM. 61 Marsupials that source of supply exists for a very short time, and then the mammary glands furnish the table. So also do they in the high types of mammals, but not until after a very long interval. In these the food- yolk is extremely smaU in quantity, yet the embryo is not supplied with milk when that ceases, but receives its nourishment through the instrumentality of an -enormous allantois, united with the highly vascular wall
. On mammalian descent. Being nine lectures delivered in the theatre of the Royal College of Surgeons during February, 1884. Mammals. Xect. III.] EMBRYO OF OPOSSUM. 61 Marsupials that source of supply exists for a very short time, and then the mammary glands furnish the table. So also do they in the high types of mammals, but not until after a very long interval. In these the food- yolk is extremely smaU in quantity, yet the embryo is not supplied with milk when that ceases, but receives its nourishment through the instrumentality of an -enormous allantois, united with the highly vascular walls of the dilated oviduct. But even in the Eutheria there is a great variation. Fig. 7.—Uterine embryo of Virginian Opossum (Didelphys virrjiniana), magnified 6 diameters. lis to the time at which this last and newest mode of feeding an embryo comes into play, some kinds having tender, and others precocious, young. The observations of Professor Chapman of America show that these bags are aU present in the Kangaroo, but that they are all small and arrested, so that neither the allantois, as in the higher mammals, nor the yolk-. 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 Parker, William Kitchen, 1823-1890. London, Griffin
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectmammals, bookyear1885
