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Updated: May 23, 2025
"Horrible enough, but curious, and, what's more, peculiar to Australia. One might search for it in vain in any other part of the world." Naturally enough, the geographer wished to preserve this interesting specimen of monotremata, and wanted to stow it away in the luggage; but M. Olbinett resented the idea so indignantly, that the SAVANT was obliged to abandon his project.
In the class of mammals the steps are not difficult to conceive which led from the ancient Monotremata to the ancient Marsupials; and from these to the early progenitors of the placental mammals. We may thus ascend to the Lemuridae; and the interval is not very wide from these to the Simiadae.
The lowest of the mammalia the Monotremata in common with birds, have oviducts which towards their lower extremities are dilated into cavities severally performing in an imperfect way the function of a uterus. This part increases at the expense of the lateral 'cornua' in the higher Herbivora and Carnivora; but even in the lower Quadrumana, the uterus is somewhat cleft at its summit."
Now these are animals at the bottom of the mammiferous class, adjoining to that of birds, of whose character and organization the monotremata largely partake, the ornithorynchus presenting the bill and feet of a duck, producing its young in eggs, and having, like birds, a clavicle between the two shoulders.
Marsupials, development of the nictitating membrane in; uterus of; possession of nipples by; their origin from Monotremata; abdominal sacs of; relative size of the sexes of; colours of. Marsupium, rudimentary in male marsupials.
At the epoch of the Trias, therefore, the Marsupialia must have, already existed long enough to have become differentiated into carnivorous and herbivorous forms. But the Monotremata are lower forms than the Didelphia, which last are intercalary between the Ornithodelphia and the Monodelphia.
Monogamy, not primitive. Monogenists. Mononychus pseudacori, stridulation of. Monotremata, development of the nictitating membrane in; lactiferous glands of; connecting mammals with reptiles. Monstrosities, analogous, in man and lower animals; caused by arrest of development; correlation of; transmission of.
If we attribute, as in my opinion we must, the primary origin of the milk glands in evolution to the mechanical stimulus of sucking, we may attempt to reconstruct the stages of the evolution of the present relation of the glands to the other organs and processes of reproduction. In the earliest stage represented by the Monotremata or Prototheria, there was no intra-uterine development.
It is fairly well developed in the two lower divisions of the mammalian series, namely, in the monotremata and marsupials, and in some few of the higher mammals, as in the walrus. But in man, the quadrumana, and most other mammals, it exists, as is admitted by all anatomists, as a mere rudiment, called the semilunar fold. Muller's 'Elements of Physiology, Eng. translat. 1842, vol. ii. p. 1117.
The Monotremata are plainly allied to the Marsupials, forming a third and still lower division in the great mammalian series. They are represented at the present day solely by the Ornithorhynchus and Echidna; and these two forms may be safely considered as relics of a much larger group, representatives of which have been preserved in Australia through some favourable concurrence of circumstances.
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