. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. MONOTREMATA. 401 to be granted to it in order to direct its move- ments. The privation of this sense, on the contrary, implies a confinement to the nest, and a reception on land of the mammary secretion of the parent. The auditory orifices (fig. 196, d) are situated about a line behind the eyes. The general form of the body and the carti- laginous condition of the bones of the extre- mities equally militate against the young Orni- thorhynchus possessing, at this period of its existence, active powers of swimming or creep
. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. MONOTREMATA. 401 to be granted to it in order to direct its move- ments. The privation of this sense, on the contrary, implies a confinement to the nest, and a reception on land of the mammary secretion of the parent. The auditory orifices (fig. 196, d) are situated about a line behind the eyes. The general form of the body and the carti- laginous condition of the bones of the extre- mities equally militate against the young Orni- thorhynchus possessing, at this period of its existence, active powers of swimming or creep- ing. The head and tail are closely approxi- mated on the ventral aspect, requiring force to pull the body out into a straight line ; and the relative quantity of integument on the back and belly shows that the position necessary for the due progressive motions is unnatural at this stage of growth. The toes on each of the four feet were com- pletely formed, and terminated by curved, co- nical, horny claws ; but the natatory fold of membrane of the fore foot had not the same proportional extent as in the adult, and the spur of the hind foot did not project beyond its socket in either specimen. In the smaller one, which was a male, it presented the form of an obtuse papilla; while in the larger specimen, although a female,it was more plainly developed and more pointed (fig. 197,f). This circum- Fig. Hind-foot and spur, young female Ornithorhynchus, magnified. ( Owen, Zonl. Trans.) stance is inexact accordance with the known laws of the development of sexual distinctions, espe- cially of those of secondary importance, such as beards, manes, plumes, horns, tusks, spurs, &c., which do not avail in distinguishing the sexes till towards the period of puberty. As the spur is the only obvious distinction of the sexes in the full-grown Ornithorhynchus, I was compelled to refer to the internal essential organs, in order to determine the sex of the specimens here described. The
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