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Show ~'304 SEXUAL SELEC'riON: 1\IAl\'Il\iALS. l' .\1~'1' Jl. number, thm:tgh very variable in distinctness. From this condition there is but a very small step to the complete absence of spots at all seasons in the adults; and lastly, to their al>sence at all ages, as occurs with certain species. From the existence of this perfect .series, and more especially from the fawns of so many species being spotted, we may conclude that the now living members of the deer family are the descendants of so~e ancient species which, like the Axis deer, was spotted at all ages and seasons. A still more ancient progenitor probably resembled to a certain extent the llyomoschus aquaticus-for this animal is spotted, and the hornless males have large exsertecl canine teeth, of which some few true deer still retain rudiments. It offers, also, one of those interesting case of a form linking together two groups, as it is intermediate in certain osteological characters between the pachyderms and ruminants, which were formerly thought to be quite distinct.41 A curious difficulty here arises. If we admit tba~ coloured spots and stripes have been acquired as ornaments, how comes it that so many existing deer, the descendants of an aboriginally spotted animal, and .n.ll the species of pigs and tapirs, the descendants of ttn aboriginally striped animal: have lost in their adult ~tate their former ornaments? I cannot satisfactorily answer this question. vVe may feel nearly sure that the spots and stripes disappeared in the progenitors of our existing species at or near maturity, so that they were retained by the youug and, owing to the law of inheritance at corresponding ages, by the young of all succeeding generations. It may have l>een a great advantflge to 11 Fulconcr and Cautlcy, 'Proc. Geolog. Soc.' 18:13; and Falconer's 'ral. Memoir.·,' vol. i. p. lDG. C.:IIAI'. XVIII. SI'OTS AND STRIPES. 305 the lion and puma from the open nature of the localities which they commonly haunt, to have lost their stripes, and to have _been thus rendered less conspicuous to their prey ; and .If the successive variations, by which this end was gamed, _occurre~ rat~er late in life, the young woulJ have rctamed theu str1pcs, as we know to be the case. In regard to deer, pigs, and tapirs, Fritz Muller has suggested t0 me that these animals by the removal through natmal se~ection of their spots or stripes would have been less ea~1ly seen by their enemies; and they would have. espec~ally required this protection, as soon as t~~ c~rmvorn.. mcreased in size and number during t~e le.rtia~·y _perwds. This may be the true explanatwn, but 1t 1s rather strange that the young should not have been equally well protected, and still more stra~ge that .with some species the adults should have !'et~med the1r spots, either partially or completely, dunn? part of the year. vVe know, though we cannot cxplam the cause, that when the domestic ass varies and becomes reddish-brown, grey or black, the stripes on the should~rs and even on the spine frequently disappear. V e:y few horses, except dun-coloured kinds, exhibit stl'lpes on a~y part of their bodies, yet we have good reason to beheve that the aboriginal horse was striped on the legs and spine, and probably on the shoulders 4z Hence t~e ~isappeara~ce of the spots and stripes in o~r adult e~Jstmg deer, plgs, and tapirs, may be due to a ch.ange m the general colour of their coats; but whether th1s. change was effected through sexual or natural select~ on, or was due to the direct action of the con<iitions of life,. or some other unknown cause, it is impossible ~0 decide. A~ observation made by Mr. Sclater well 1llustrates our Ignorance of the laws which 1·egulate the 42 ''l'ho Variation of Animals and Plants under D 1868, vol. i. p. Gl-Gl. omcstication,' VOL. 11. X |