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Next anterior in age are the mammalia of the Lower Oolite of Stonesfield, of which four species are known, also very small and probably marsupial, with one exception, the Stereognathus ooliticus, which, according to Professor Owen's conjecture, may have been a hoofed quadruped and placental, though, as we have only half of the lower jaw with teeth, and the molars are unlike any living type, such an opinion is of course hazarded with due caution.

Even if we entirely ignore it, all that we have learned from the zoological facts of comparative anatomy and ontogeny as to the placental character of man remains untouched. These prove beyond all doubt the common descent of man and all the rest of the mammals.

A similarly increasing ratio should be granted for the successive developments of the difference between the Lemuroid and the higher forms of primates; for those between the original primate and other root-forms of placental mammals; for those between primary placental and implacental mammals, and perhaps also for the divergence of the most ancient stock of these and of the monotremes, for in all these cases modifications of structure appear to increase in complexity in at least that ratio.

They did not go forward, and the survivors are but an infinitesimal fraction of those which perished. Let us take an illustration where palæontology can help us. The earth was at one time covered with marsupial mammals. Some advanced into placental forms. The great mass remained behind. And outside of Australia the opossums are the only survivors of them all.

It may perhaps be accounted for by the power acquired by the placental mammalia, when they became dominant, a power before which the class of vertebrata next below them, as coming most directly in competition with them, may more than any other have given way.

II. The placenta is a pulmonary organ like the gills of fish. Oxygenation of the blood from air, from water, by lungs, by gills, by the placenta; necessity of this oxygenation to quadrupeds, to fish, to the foetus in utero. Placental vessels inserted into the arteries of the mother. Use of cotyledons in cows. Why quadrupeds have not sanguiferous lochia.

For the numerous circumstances in which vegetable buds are analogous to animals, the reader is referred to the additional notes at the end of the Botanic Garden, Part I. It is there shewn, that the roots of vegetables resemble the lacteal system of animals; the sap-vessels in the early spring, before their leaves expand, are analogous to the placental vessels of the foetus; that the leaves of land-plants resemble lungs, and those of aquatic plants the gills of fish; that there are other systems of vessels resembling the vena portarum of quadrupeds, or the aorta of fish; that the digestive power of vegetables is similar to that of animals converting the fluids, which they absorb, into sugar; that their seeds resemble the eggs of animals, and their buds and bulbs their viviparous offspring.

In the place of a mere assertion of our ignorance as to the way these phenomena have been produced, he brings forward, as their explanation, a cause which it is contended in this work is demonstrably insufficient. Chances against concordant variations. Examples of discordant ones. Concordant variations not unlikely on a non-Darwinian evolutionary hypothesis. Placental and implacental mammals.

"The Finchley girl's still down with whatever it is she has, and it's something I haven't been able to diagnose yet. And I've been checking on bacteria cultures, and in what spare time I have, I've been dissecting specimens for Bill Chandler. Bill's finally found a mammal. Looks like a lizard, and it's only four inches long, but it's a real warm-blooded, gamogenetic, placental, viviparous mammal.

In the next stage, if we adopt the modern view that Marsupials are descended from Placental Mammals, the eggs would be retained for increasing periods in the uteri, and would be born in a well-developed condition, since lactation would demand active sucking effort on the part of the young.