apes appears to be completely bridged over.' [4] See note, p. 80. [5] _Perfect_, in the sense of highest stage of evolution, may seem a _petitio principii_. Leaving aside the consideration that no living creature is absolutely perfect, in the sense that its organization cannot become more efficient or proficient, we have here to deal with relative perfection of the whole organization. A fish or a snake is in its way more specialized than a mammal; but specialization does not necessarily mean height of development: it generally means life in a comparatively narrow groove. The acts of giving birth and nourishing the young with the mother's milk is a much higher stage than the act of laying eggs and letting them run their chance. The development of a hairy coat goes along with heightened temperature of the blood, subsequent greater independence of the surrounding temperature, and increased steady activity of the brain and other nerve-centres. The brain of the Mammalia, in its minute structure, is much more complex. This rule applies to some of the principal sense organs, chiefly the nose and the ear. The skeleton, not so much as a whole as in the various bones and joints, is more neatly finished, and built up more in conformity with 'scientific principles,' than is the case even with birds, in spite of their marvellous specialization. The same is the case with the vascular system, notably the heart and the veins, and with the excretory organs. In all of these many imperfections, still to be found in the other classes, have been corrected in Mammalia. The Primates take an easy first by their hands, and among them the apes and man himself by their brains. [6] 'Die menschenähnlichen Affen und ihre Organisation im Vergleich zur menschlichen.' 1883. There are, for example, the muscles of the ear. In most people the majority, or even all of them, are no longer movable at will, while in the apes they are still in use. The important point, however, is that these muscles are still present in man, although often in a reduced condition. They are the following: (1) Musculus auricularis anterior or attrahens auris, which is frequently much reduced and no longer reaches the ear at all, being then absolutely useless; (2) Musculus auricularis superior or attollens auris, more constant than the former; (3) Musculus auricularis posterior or retrahens auris, likewise often functional. Occasionally smaller slips differentiated from these three muscles are present, and as so-called intrinsic muscles are restricted to the ear itself; their function is, or was, that of curling up or opening the external ear. [Illustration: OUTLINES OF THE LEFT EAR OF--