ed. The
friction of the water has been the means of removing the hair from many
aquatic mammals--the whales, porpoises, dugongs, and manatees are
examples.

As the back of man forms the specially hairless region of his body, we
must conclude that it is in all probability the first part which became
entirely denuded of hair. The gorilla, according to Professor Gervais,
is the only mammal which agrees with man in having the hair thinner on
the back, where it is partly rubbed off, than on the lower surface. Du
Chaillu states that he has "himself come upon fresh traces of a
gorilla's bed on several occasions, and could see that the male had
seated himself with his back against a tree-trunk." He also says: "In
both male and female the hair is found worn off the back; but this is
only found in very old females. This is occasioned, I suppose, by their
resting at night against trees, at whose base they sleep." The gorilla
has only very partially acquired the erect position, and probably sits
but little in the attitude common to man. In man the case is different;
in proportion as his progenitors grew more and more erect, he must have
lain less and less upon his stomach, and more and more upon his back or
sides, and this is seen in the savage man during his lazy hours--who
stretches himself on the ground in the sun, with his back propped, where
possible, by a slight mound or the wall of his hut. The continual
friction of the surface of the back would arrest the growth of hair; for
hair grows where there is normally less friction, and _vice versa_.

As man became more and more hairless, especially among savage and naked
races, we should conclude that such a modification would be considered a
beauty, and women would select such men in preference to more hairy
individuals. The New Zealand proverb is: "There is no woman for a hairy
man." Sexual selection, then, would play a very important part; and the
difficulty of understanding how man became divested of hair is readily
explained.

Haeckel says: "Even if we knew absolutely nothing of the other phenomena
of development, we should be obliged to believe in the truth of the
theory of descent, solely on the ground of the existence of rudimentary
organs."

REPRODUCTION BY MEANS OF EGGS.

It might be thought there existed a missing link between animals which
lay eggs and those which do not; this, however, is done away with in
many instances--one, for example, is found in our commo