[108]

Frank

Draw line at .29 from apex [sketch] — or parallel??

Fig 212.

[3 figures pasted on]

(Fac-similes. Please observe short horizontal line at base of each, which represents surface of soil from which they rise.)

Phalaris canariensis: 3 cotyledons exposed in a blackened box with one side open, during 8 hours, before a SW. window on a bright day. Curvature towards the light carefully traced on card.

[108v]

(68

Ch. 17 18 Mammals

young deer should not have been equally protected, & still more strange that the adults of certain species kinds of deer should have retained their sp spots, either partially or completely, during one season of the year. We know, though we cannot explain the cause, that where the domestic ass varies & becomes [illeg] reddish-brown or grey, the stripes on the shoulder & even on the spine often frequently disappear. Very few horses, excepts dun-coloured horses kinds, exhibit stripes on any part of their bodies, yet we know good reason to believe that the aboriginal horse was striped on its legs & spine, & perhaps on the its shoulders* 60 42 Hence the disappearance of the spots & stripes in most of our adult existing deer, pigs & tapirs may be due to the general colour of their bodies having been changed; but whether this change is has been due to sexual selection, or to the direct action of the conditions of life, or to some other unknown causes, it is impossible to decide. Our ignorance on this subject in which shown by an observation

[Descent 2: 305-6: "This may be the true explanation, but it is rather strange that the young should not have been equally well protected, and still more strange that with some species the adults should have retained their spots, either partially or completely, during part of the year. We know, though we cannot explain the cause, 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. Very few horses, except dun-coloured kinds, exhibit 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.42 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 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
42 'The Variation of Animals and Plants under Domestication,' 1868, vol. i. p. 61-64.
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. tæniopus, 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.43
43 'Proc. Zool. Soc.' 1862, p. 164. See, also, Dr. Hartmann, ' Ann. d. Landw.' Bd. xliii. s. 222."]