ause all these forms agree
in certain structural respects that place them apart from the other
mammalia, in the same way, for example, that the races of white men may be
recognized as a group distinct from the black and red races. But
comparative studies, prosecuted not only by those who have been forced to
adopt the evolutionary interpretation, but also by believers in special
creation like Linnaeus and Cuvier and other more modern opponents of
evolution, have shown that the peculiar qualities of this order are shared
by the human species. Indeed, the name of primates was given to this
section by Linnaeus himself, because the human body found a place in the
array which begins at the lower extreme with the lemurs and the monkeys
and ends with man at the other end. Again it is found that no separate
order of mammals exists to include only the genus _Homo_.

To one unacquainted with the facts of vertebrate comparative anatomy, the
distinguishing characteristics of the primates seem to be trivial in
nature. It is surprising to find how insignificant are the details to
which appeal must be made in order to draw a line between our own division
of mammalia and the others. It is well to review them as they are given in
the standard text-books of comparative anatomy. Primates are eutheria, or
true mammalia possessing a placental attachment of the young within the
parent. The first digits, namely, the "great toe" and the "thumb," are
freely movable and opposable to the others, so that the limbs are
prehensile and clasping structures; usually but not always the animals of
this order are tree-dwellers in correlation with the grasping powers of
the feet and hands. The permanent teeth succeed a shorter series of
so-called "milk teeth," and they are diverse in structure, being incisors,
canines, or "eye teeth," premolars, and molars; the particular numbers of
each kind are almost invariable throughout the order and markedly
different from those of other orders. The number of digits is always five,
and with few exceptions they bear nails instead of claws. The clavicles,
or "collar bones," are well developed in correlation with the prehensile
nature of the fore limbs; a bony ring surrounds the orbit or eye socket.
Finally there are two mammary glands by which the young are suckled. It is
because any other details of difference between man and other forms are
far less marked than the agreements in these respects, that the human
species m