Page:Evolution of Life (Henry Cadwalader Chapman, 1873).djvu/102

72 extinct Marsupials allied to the Thylacinus, This view has much in its favor, as the transition from the pouch-bearers to the ordinary mammals is very gradual, as, for example, the smaller Opossums lead up to the Insectivora (Hedgehog), the Wombat to the Beaver, etc. The fact of Australia, with few exceptions, containing only the reptile-bird-like and pouch-bearing mammals at the present day seems to confirm the view of the ordinary mammals coming from the pouch-bearers in some such way; for while we find in other parts of the world fossil remains of Marsupials, with the exception of the Opossums, the living pouch-bearers are found only in Australia and the adjacent islands, the fossil remains being Marsupials, but of a much larger size. Australia seems to offer us a living picture of what Europe once has been. Just as in Europe and other places, among the ordinary mammals, we have various kinds preying on each other, so we find the same thing among the existing pouch-bearers in Australia; and this relation existed also in past time. The Diprotodon (a gigantic Kangaroo) was warred upon by the Thylacoleo, a meat-eater of the size of a lion. Supposing this view of the origin of the ordinary Mammalia to be correct, the number of branches descending from the pouch-bearers will depend on the view taken by naturalists of the affinities of the different orders. Although there are twelve orders in the ordinary Mammalia, some of them seem directly or indirectly to be more nearly related than others. Thus, the order of odd-toed (Rhinoceros, Tapir, Horse) and that of even-toed (Pig, Hippopotamus, Sheep, Deer) are joined in one group, the Ungulata, or hoofed animals: they would represent one stem. The Half-Apes, the gnawing animals, with the Hyrax and Elephant, the insect-eaters, the bats, and true Apes, with man, would make a second stem. The meat-eaters (Lion, Fig. 81, Dog, Seal, etc.) may represent a third stem; while the Edentata, or animals without