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Show 280 DEFINITE ACTION OF TilE CllAP. XXIII. Erman s<J states that this occurs with the Kirgisian sheep when brought to Orenburgh. . . It is well known that hemp-seed causes bullfinches and certam other buds to become black. Mr. Wallace has communicated to me some much more remarkable facts of the same nature. The natives of the Amazonian region feed the common green parrot (Ohrysotisfestivct, Linn.) with t~c fat of large Siluroid fishes, and the birds thus treated become bea~tlfully variegated with rod and yellow feathers. In tho Malayan archipelago, the natives of Gilolo alter in an analogous manner the colours of another parrot, namely, the Lorius gan·ulus, Linn., and thus produce the Lor·i ray'ah or King-Lory. These parrots in the Malay Islands and South America, when fed by the natives on natural vegetable food, such as rice and plantains, retain their proper colours. Mr. Wallace has, also, recorded 4o a still more singular fact. "'l'he Indians (of S. America) have " a curious art by which they change the colours of the feathers of many " birds. They pluck out those from the part they wish to paint, and "inoculate tho fTesh wotmd with the milky secretion fTom the skin of a "small toad. The feathers grow of a brilliant yellow colour, and on being " plucked out, it is said, grow again of the same colour without any fresh r: operation." Bechstein 41 does not entertain any doubt that seclusion from light affects, at least temporarily, the colours of cage-birds. It is well known that the shells of land-mollusca are affected by the abundance of lime in different districts. Isidore Geoffroy St. H:ilaire42 gives the case of Ilelix lactea, which has recently been calTied from Spain to the South of France and to the Rio Plata, and in both these countries now presents a distinct appearance, but whether this has resulted from food. or climate is not known. With respect to the common oyster, 1\fr. F. Buckland informs me that he can generally distinguish the shells from different districts; young oysters brought from Wales and laid down in beds where "natives" are indigenous, in the short space of two months begin to assume the "native" cha,racter. M. Costa 43 has recorded a much more remarkable case of the same nature, namely, that young shells taken from the shores of England and placed in the Mediterranean, at once altered their manner of growth and formed prominent diverging rays, like those on the shells of the proper Mediterranean oyster. The same individual shell, showing both forms of growth, was exhibited before a society in Paris. Lastly, it is well known that caterpillars fed on different food sometimes either themselves acquire a different colour or produce moths different in colour.44 39 'Travels in Siberia,' Eng. translat., vol. i. p. 228. 40 A. R. Wallace, 'Travels on the Amazon aml Rio Negro,' p. 294. 41 'Nalurgcschicltte der Stubenvugcl,' 1840, s. 2G2, 308. 4~ 'Hist. Nat. Gen.,' tom. iii. p. 402. 43 'Bull. de Ia Soc. Imp. d'Acclimat.; tom. viii. p. 351. 44 See an account of Mr. Gregson's C>xperiments on the Abraxus grossulariet£( t, 'Proc. E utomolog. Sue.,' Jan. 6th, 1862 : these experiments have been confirmed Ly l\1r. Greening, in 'Proc. of the Northern Entomolog. Soc.,' July 28th, 1862. For the effects of food on caterpillars, see a curious account by M. Micbcly, in 'Bull. de la CIIAP. XXIII. CONDITIONS OF LIFE. 281 It would be travelling beyond my proper. limits ho.re to discuss how far organic beings in a state of nature are definitely modified by changed conditions. In my 'Origin of Species' I have given a brief abstract of the facts bearing on this point, and have shown the influence of light on the colours of birds, and of residence near the sea on the lurid tints of insects, and on the succuloncy of plants. Mr. Herbert Spencer 45 has recently discussed with much ability this whole subject on broad and general grounds. He argues, for instance, that with all animals the external and internal tissues are differently acted on by the surrounding conditions, and they invariably differ in intimate structure. So again the upper and lower surfaces of true leaves, as well as of stems and petioles, when these assume the function and occupy the position of leaves, are differently circumstanced with respect to light, &c., and apparently in consequence differ in structure. But, as Mr. Herbert Spencer admits, it is most difficult in all such cases to distinguish between the effects of the definite action of physical conditions and the accumulation through natural selection of inherited variations which are serviceable to the organism, and which have arisen independently of the definite action of these conditions. Although we are not here concerned with organic beings in a state of nature, yet I may call attention to one case. Mr. Meehan,46 in a remarkable paper, compares twenty-nine kinds of American trees, belonging to various orders, with their nearest European allies, all grown in close proximity in the same garden and under as nearly as possible the same conditions. lu the American species Mr. Meehan finds, with the rarest exceptions, that the leaves fall earlier in the season, and assume before falling a brighter tint; that they are less deeply toothed or serrated; that the buds are smaller ; that the trees are more diffuse in growth and have fewer branchlets; and, lastly, that the seeds are smaller-all in comparison with the corresponding European species. Now, considering that these trees belong to distinct orders, it is out of the question that the peculiarities just specified should have been inherited in the one continent from one progenitor, and in the other from another progenitor ; and considering that the trees inhabit widely different stations, these peculiarities can hardly be supposed to be of any special Soc. Imp. d'Acc]imat.,' tom. viii. p. 563. For analogous facts from Dublbom on Hymenoptera, see We:;twood's 'Modern Class. of lmects,' vol. ii. p. 98. See also Dr. L. Moller, 'Die Abbangigkeit der Insecten,' 1867, s. 70. 45 ''l'bc Principles of Biology,' vol. ii. 1866. The present clutptcrs were written before I had read Mr. Herbert Spencer's work, so that I have not been able to make so much use of it as I should otherwise probably have done. 46 'Proc. Acad. Nat. Soc. of Pb:ilo.- uelpltb,' Jun. 28th, 1862. |