. Outlines of zoology. Zoology. 682 MAMMALIA. embryos of some Placentals also. In Oi-nithorhynclms, the ischia form a long ventral symphysis; in Echidna, the acetabulmn socket for the femur is incompletely ossified as in Birds; the pubes bear epipubic bones, as in Marsupials. On the side of the tarsus, in the duckmole, there is a spur perforated by the duct of a gland. This spur persists in the males, is rudimentary in the females. The male Echidna has a similar but smaller spur. The brain is smooth, the cerebellum is not covered by the cerebrum, there is a large anterior commissure and the co
. Outlines of zoology. Zoology. 682 MAMMALIA. embryos of some Placentals also. In Oi-nithorhynclms, the ischia form a long ventral symphysis; in Echidna, the acetabulmn socket for the femur is incompletely ossified as in Birds; the pubes bear epipubic bones, as in Marsupials. On the side of the tarsus, in the duckmole, there is a spur perforated by the duct of a gland. This spur persists in the males, is rudimentary in the females. The male Echidna has a similar but smaller spur. The brain is smooth, the cerebellum is not covered by the cerebrum, there is a large anterior commissure and the corpus callosum is rudimentary, or, according to Symington, absent. The food canal ends in a cloaca. The right auriculo-ventricular valve in Ornithorhynchus is partly muscular as in Birds, while in other Mammals it is membranous and is worked by papillary muscles attached to it by tendon-like cords (chorda tendinea;). The temperature of the body is said to be about 25-28° C. The ureters open, not into the bladder, but into the urinogenital canal. The testes remain in the abdo- men. The left ovary is larger than the right, as in Birds. The vasa deferentia open separately into the urinogenital canal. So in the female do the oviducts, and these have no fringed fimbriated apertures nor distinct uterine region. The penis is attached to the ventral wall of the cloaca, and its canal is not continuous with the urinogenital canal. The ova are large, with abundant yolk, and undergo meroblastic segmentation. The Prototheria are oviparous. The duckmole, duck-billed platypus, or mole, lives beside lakes and rivers. It swims by means of its fore limbs, which are webbed as well as clawed ; it grubs for aquatic insects, crustaceans, and \sorms in the mud at the bottom of the water. It collects small animals in' its cheelc pouches, and chows them at leisure with its eight horny jaw. idna. 244.—Pelvis of Ech- (From Edinburgh Museum of Science and Art.) .^, sacrum ; Ep, epipubic bones ; A
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectzoology, bookyear1895
