If we could search along the bank we should find, somewhere below the water’s edge, a hole, and again, a few feet back on the land, another among the grass and reeds; and both of these lead into a long passage, which ends in a snug underground nest--a dark hole lined with dry grass and weeds--where in the summer time (about December) we should find the mother platypus, with two or four tiny naked young ones, not two inches long, cuddled under her. How these little ones begin life we do not know. The natives talk about finding soft eggs like those of reptiles; but it seems more likely that these eggs break just as they are laid, like those of our common lizard (see p. 105), and the naked little ones come out alive into the nest. [Illustration: Fig. 50. A, Head of Ornithorhynchus, showing serrated bill; B, Hind foot with claw _a_, found on the males only; C, Webbed fore foot.] And how are they fed? Their mother has no teat, like the cow, to put into their mouth, for she is a very primitive creature; only in one spot amid her fur are a number of little holes, and from these she can force out milk for them to drink as they press against her with their soft flat bills. So here, in a dark underground nest, away from the world, because she cannot, like the higher animals, carry her little ones till they are perfect, the duck-billed platypus, which may well be called “paradoxical” (see Fig. 49), enables us to picture to ourselves how, in ages long gone by, mothers first began to feed their little ones with their own milk. And now, perhaps, you will be struck by this animal’s likeness to a bird, especially when you hear that the little baby water-moles have a soft horny knob on their nose, just where young birds have a hard knob for breaking through the shell; and you will ask if milk-giving animals came from birds. Not at all; young tortoises, too, have such a knob, and so have crocodiles; and, moreover, these duck-billed moles have many parts of their skeleton, especially the shoulder bone and the separate bones of the skull, very like our living reptiles, and still more like some which lived in ages long gone by.[111] And yet at the same time they differ essentially both from reptiles and birds in many points besides those we have been able to mention, and in one in particular, which we can understand now we have studied these groups, namely, that the platypus, like all milk-giving animals, _is without that curious quadrate bone_ (_q_, Figs. 23 and 33) _which we find in all reptiles and birds_.