incisors, two canines, and four molars in each jaw.  Since Huxley wrote, a large bulk of additional work upon teeth has been published, and we now know that man and the anthropoid apes display the same kind of degenerative specialisation in their jaws.  Simpler and older forms of mammals had a much larger number of teeth, and these differed among themselves more than the teeth of the higher forms.  In the Anthropoids and Man, the jaws are proportionately shorter and less heavy than in simpler forms, and, in correspondence with this, the number of the teeth has become reduced, while the teeth themselves tend to form a more even row.  The canine or eye-teeth are relatively smaller in the gorilla than in primitive mammals; they are still smaller in the lower races of man; while in ordinary civilised man they do not project above the others.  The shortening of the jaw is still proceeding, and, although in lower races of man the last molar or wisdom tooth is almost as large as the molars in front of it, in the higher races the wisdom tooth is much smaller and frequently does not develop at all, or begins to decay very soon after its appearance.  If the process of extinction of lower races were to proceed much further, so that civilised white races became the only human inhabitants of the earth, then the gap between the Anthropoids and Man would be wider than it now is; man would be characterised by the presence of one tooth less than the anthropoids, just as the anthropoids and some lower monkeys are characterised by having one tooth less than monkeys still lower.

In all, the nostrils have a narrow partition and look downwards as in man.  The arms are always longer than the legs, the difference being greatest in the orang and least in the chimpanzee.  We know now that in the lower races of man, the arms are proportionately longer than in higher races, and it has recently been shewn that, although there is a general proportion between the length of the long bones and the height of the whole body in man, so that the height may be calculated with an average error from these bones, yet the probable error is greater when the calculation is made from the arms than when it is made from the legs.  In fact, the length of arm as compared to the length of leg and to whole height is a more variable feature in man than the length of leg.

In all the anthropoids, the forelimbs end in hands with longer or shorter thumbs, and the great toe, always smaller than in man, is far more movable and can be opposed like a thumb to the other toes.  Since Huxley wrote, a considerable amount of evidence has been collected shewing that partial opposability of the toe in man is not uncommon, and that there is evidence as to a tendency to increase of length of the great toe within historical times.  None of the great apes have tails, and none of them have the cheek pouches common among lower monkeys.

Huxley then gives an account of the natural history of these animals, an account which still remains the best in literature.  He sums up the habits of the Asiatic forms as follows: