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Show 316 LAWS OF VAlUATION. CHAP. XXIV. the bony protuberances which properly support the horns exist as mere rudiments. With cultivated plants it is far from rare to find the petal~, stamens, and pistils represented by rudiments, like th~se observed m natural species. So it is with the whole seed in many frmts; thus ~ear Astrakhan there is a grape with mere traces of seeds, "so small and lymg so near t~e " stalk that they are not perceived in eating the grape.'' 85 In certam varieties of the gourd, the tendrils, according to Naudm, are repres.ented by rudiments or by various monstrous growths. . In the broccoli ~nd cauliflower the greater number of the flowers are mcapable_ of expansiOn,. and include rudimentary organs. In the Feather hyacmth (111uscan comosum) the upper and central flowers are brigh_tly coloured but rudimentary; under cultivation the tendency to ~bortwn travels downwa1:ds and outwards and all the flowers become rudimentary; but tho abortive stamens and ~istils are not so small in the lower as in the upper flowers. In the Yibunwm opulus, on the other hand, the outer flowers naturally have their organs of fructification in a rudimentary state, and the corolla is of large size; under cultivation, the change spreads to the centre, and all the flowers become affected; thus the well-known Snow-ball bush is produced. In the Compositre, the so-called doubling of the flowers consists in the greater development of the corolla of the central florets, generally accompanied with some degree of sterility; and it has been observed 86 that the progressive doubling invariably spreads from the circumference to the centre,-that is, from the ray florets, which so often include rudimentary organs, to those of the disc. I may add, as bearing on this subject, that, with Asters, seeds taken from the florets of the circumference have been found to yield the greatest number of double flowers.ll7 In these several cases we have a natural tendency in certain parts to become rudimentary, and this under culture spreads either to, or from, the axis of the plant. It deserves notice, as showing how the same laws govern the changes which natural species and artificial varieties undergo, that in a series of species in the genus Carthamus, one of the Compositre, a tendency in the seeds to the abortion of tho pappus may be traced extending from the circumference to the centre of the disc: thus, according to A. de Jussieu,88 the abortion is only partial in C(tdlw:rnus cnticus, but more extended in C. lanatus; for in this species two or three alone of the central seeds are furnished with a pappus, the surrounding seeds being either quite naked or furnished with a few hairs; and lastly, in C. ti11cto?·ius, even the central seeds are destitute of pappus, and the abortion is complete. With animals and plants under domestication, when an organ dis-appears, leaving only a rudiment, the loss has generally been sudden, as with hornless and tailless breeds; and such cases may be ranked as inherited monstrosities. But in some few cases the loss has been gradual, and sa Pallas, 'Travels,' Eng. translat., vol. i. p. 243. 86 Mr. Beaton, in 'Journal of Horticulture,' May 21, 1861, p. 133. 87 Lecoq, ' De la Feeo:1datiun,' 1862, p. 233. ss ' Annalcs du Museum,' tom. vi. P· 31D. CHAP. XXIV. ARRESTED DEVELOPMENT AND .RUDIMENTS. 317 has been partly effected by selection, as with the rudimenta:y combs and wattles of certain fowls. We have also seen that the wmgs of some domesticated birds have been slightly reduced by disuse, and the great reduction of the wings in certain silk-moths, with more rudiments left, has probably been aided by disuse. With species in a state of nature, rudimentary organs are so extremely common that scarcely one can be named which is wholly free from a blemish of this nature. Snch organs are generally variable, as several naturalists have observed; for, being useless, they are not regulated by natural selection, and they are more or less liable to reversion. The same rule certainly holds good with parts which have become rudimentary under domestication. We do not know through what steps under nature rudimentary organs have passed in being reduced to their present conclition; but we so incessantly see in species of the same group the finest gradations between an organ in a rudimentary and perfect state, that we are led to believe that the passage must have been extremely gradual. It may be doubted whether a change of structure so abrupt as the sudden loss of an organ would ever be of service to a species in a state of nature; for tho conditions to which all organisms are closely adapted usually change very slowly. Even if an organ did suddenly disappear in some one individual by an arrest of development, intercrossing with the other individuals of the same species would cause it to reappear '.in a more or less perfect manner, so that its final reduction could only be effected by the slow process of continued disuse or natural selection. It is much more probable that, from changed habits of life, organs first become of less and less use, and ultimately superfluous; or their place may be supplied by some other organ; and then disuse, acting on the offspring through inheritance at corresponding periods of life, would go on reducing the organ; but as most organs could be of no use at an early embryonic period, they would not be affected by disuse; consequently they would be preserved at this stage of growth, and would remain as rudiments. In addition to the effects of disuse, the principle of economy of growth, already alluded to in this chapter, would lead to the still further reduction of all supeTfluous parts. With respect to the final and total suppression or abortion of any organ, another and distinct principle, which will be discussed in the chapter on pangenesis, probably takes a share in the WOTk. With animals and plants reared by man there is no severe or recurrent struggle for existence, and the principle of economy will not come into action. So far, indeed, is this fTom being the case, that in some instances organs, which are naturally rudimentary in the parent-species, become partially redeveloped in the domesticated descendants. Thus cows, like most other ruminants, properly have four active and two rudimentary mammre; but in our domesticated animals, the latter occasionally become considerably developed and yield milk. The atrophied mammre, which, in male domesticated animals, including man, have in some rare cases grown to full size and secreted milk, perhaps offer an analogous case. The hind feet of dogs include rudiments of a fifth toe, and in certain large breeds these toes, though still rudimentary, become considerably developed |