The Descent of Man

Richtung der Haare,' etc., Muller's 'Archiv fur
Anat. und Phys.' 1837, s. 51.) that in our children
the limit between the hairy scalp and the
naked forehead is sometimes not well defined;
so that here we seem to have a trifling case of
reversion to a progenitor, in whom the forehead
had not as yet become quite naked.
It is well known that the hair on our arms tends
to converge from above and below to a point at
the elbow. This curious arrangement, so unlike
that in most of the lower mammals, is common
to the gorilla, chimpanzee, orang, some species
of Hylobates, and even to some few American
monkeys. But in Hylobates agilis the hair on
the fore-arm is directed downwards or towards
the wrist in the ordinary manner; and in H. lar
it is nearly erect, with only a very slight forward
inclination; so that in this latter species it
is in a transitional state. It can hardly be doubted
that with most mammals the thickness of
the hair on the back and its direction, is adap-