228 PAN 
are permanent from youth to the adult state, what, if any, are the 
distinctions in color between the sexes, (in some species we know there 
is no difference, but in others we are not so sure) ; what are the limits 
of the dispersion of those we gaily describe as distinct—do two or 
more species or races, call them what you will, dwell together in amity 
retaining their distinctive characteristics within limited areas; all these 
problems and more arise to greet us, and for the most of them we have 
no answer. 
The material gathered in most Museums is so small and unsatis- 
factory, that it is of no avail in deciding the facts we all seek. The 
best, and so far as I have found, the only considerable collection of © 
these animals extant to-day, is in the Berlin Museum, where about 
eighty skins and perhaps as many skulls have been brought together 
from different parts of Africa. But when we study these, we con- 
stantly meet with difficulties that not only perplex us, but prevent any 
satisfactory decision from being reached. It is easy enough to solve 
a difficulty by describing some troublesome specimens as new, and 
leaving the proof for some one else to discover, but that does not solve 
legitimate doubts, nor help overmuch to teach us the truth we desire 
to know. 
In seeking for characters upon which specific differences may be 
founded we naturally first examine the crania, and at once we are 
confronted with a fact that prevails among all the great Apes, that 
individual variations exist to such an extent, that no one character can 
be depended upon, for no two skulls are alike, and they differ from each 
other in a manner equally great as is observed among human skulls. I 
have already commented upon this fact when discussing the specific 
values of specimens of the Gorilla and Ourang-utan, where in the 
latter I was compelled to decline to recognize more than one species 
after most careful investigation of a very large series of crania; and 
to recognize only with great doubt certain forms of Gorilla as possible 
species, not on any cranial character, but simply on the color of the fur 
which eventually may prove, as our knowledge of these animals 
increases, to be merely phases of pelage attributable solely to age. Cer- 
tainly neither among Gorillas nor Ourang-utans can any specific differ- 
ence be safely based upon cranial characters, and in this respect the 
Chimpanzees are no exception. At present, therefore, we rely mainly 
for our specific characters of these animals upon the texture, length 
and color of the hair; the presence or absence of beard; color of the 
face; sometimes of the hands and feet; seldom on the teeth, (for 
characters among these are rarely found), the extent in which the face 
