and that they would have especially required this protection, as soon
as the carnivora increased in size and number during the tertiary
periods. This may be the true explanation, but it is rather strange
that the young should not have been thus protected, and still more so
that the adults of some species should have retained their spots,
either partially or completely, during part of the year. We know that,
when the domestic ass varies and becomes reddish-brown, grey, or black,
the stripes on the shoulders and even on the spine frequently
disappear, though we cannot explain the cause. Very few horses, except
dun-coloured kinds, have stripes on any part of their bodies, yet we
have good reason to believe that the aboriginal horse was striped on
the legs and spine, and probably on the shoulders. (43. The Variation
of Animals and Plants under Domestication, 1868, vol. i. pp. 61-64.)
Hence the disappearance of the spots and stripes in our adult existing
deer, pigs, and tapirs, may be due to a change in the general colour of
their coats; but whether this change was effected through sexual or
natural selection, or was due to the direct action of the conditions of
life, or to some other unknown cause, it is impossible to decide. An
observation made by Mr. Sclater well illustrates our ignorance of the
laws which regulate the appearance and disappearance of stripes; the
species of Asinus which inhabit the Asiatic continent are destitute of
stripes, not having even the cross shoulder-stripe, whilst those which
inhabit Africa are conspicuously striped, with the partial exception of
A. taeniopus, which has only the cross shoulder-stripe and generally
some faint bars on the legs; and this species inhabits the almost
intermediate region of Upper Egypt and Abyssinia. (44. Proc. Zool.
Soc. 1862, p. 164. See, also, Dr. Hartmann, Ann. d. Landw. Bd.
xliii. s. 222.)
QUADRUMANA.
[Fig. 72. Head of Semnopithecus rubicundus. This and the following
figures (from Prof. Gervais) are given to shew the odd arrangement and
development of the hair on the head.
Fig. 73. Head of Semnopithecus comatus.
Fig. 74. Head of Cebus capucinus.
Fig. 75. Head of Ateles marginatus.
573