But what is the use of speculating? Here is the ’possum in our woods; that we know; and yonder in Australasia are his thirteen sets of cousins, and there they seem always to have been, for of these thirteen sets of cousins, four sets have so long since ceased to live that they are now among the fossils, slowly turning, every one of them, to stone! A queer history he has, surely! But queerer than his history, is his body, and the way he grows from babyhood to twenty-pound ’possumhood. For besides having a tail that can be used for a hand, and a paw with a thumb like the human thumb, the female ’possum has a pocket or pouch on her abdomen, just as the kangaroo has, in which she carries her young. Now that is peculiar, so very peculiar when you study deeply into it, that the ’possum becomes to the scientist quite the most interesting mammal in North America. Returning from a Christmas vacation one year, while a student in college, I brought back with me twenty-six live ’possums so that the professor of zoölogy could study the peculiar anatomy of the ’possum for several of its many meanings. This pouch, for instance, and the peculiar bones of the ’possum, show that it is a very primitive mammal, one of the very oldest mammals, so close to the beginning of the mammalian line that there are only two other living “animals” (we can hardly call them mammals) older and more primitive--the porcupine ant-eater, and, oldest of all, the duck-bill, not “older” at all perhaps, but only more primitive. For the duck-bill, though classed as a mammal, not only has the bill of the duck, but also lays eggs like the birds. The porcupine ant-eater likewise lays eggs, and so seems almost as much bird or reptile as mammal. And as the birds and reptiles lived upon the earth before the age of mammals, and are a lower and more primitive order of creatures, so the duck-bill, the porcupine ant-eater, and the ’possum, because in their anatomy they are like the birds and the reptiles in some respects, are perhaps the lowest and the oldest of all the mammals. The ’possum, therefore, is one of the most primitive of mammals, and dates as far back as the reptilian age, when only traces of mammalian life are to be found, the ’possum’s fossil ancestors being among the notable of these early remains. The mammals at that time, as I have just said, were only partly mammal, for they were partly bird or reptile, as the duck-bill and ant-eater still are. Now the ’possum does not lay eggs as these other two do, for its young are born, not hatched; yet so tiny and undeveloped are they when born, that they must be put into their mother’s pouch and nursed, as eggs are put into a nest and brooded until they are hatched--really born a second time. For here in their mother’s pouch they are like chicks in the shell, and quite as helpless. It is five weeks before they can stick their heads out and take a look at the world.