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Show 392 PROVISIONAL HYPOTHESIS CHAP. XXVII. like those on his neck, whilst the female has one of common feathers. In feather-footed pigeons and fowls, feathers like those on the wing arise from the outer side of the legs and toes. Even the elemental parts of the same feather may be transposed; for in the Sebastopol goose, barbules are developed on the divided filaments of the shaft. Analogous cases are of such frequent occurrence with plants that they do not strike us with sufficient surprise. Supernumerary petals, stamens, and pistils, are often produced. I have seen a leaflet low down in the compound leaf of Vicia sativa converted into a tendril, and a tendril possesses many peculiar properties, such as spontaneous movement and irritability. The calyx sometimes assumes, either wholly or by stripes, the colour and texture of the corolla. Stamens are so frequently converted, more or less completely, into petals; that such cases are passed over as not deserving notice ; but as petals have special functions to perform, namely, to protect the included organs, to attract insects, and in not a few cases to guide their entrance by well-adapted contrivances, we can hardly account for the conversion of stamens into petals merely by unnatural or superfluous nourishm~nt. Again, the edge of a petal may occasionally be found including one of the highest products of the plant, namely the pollen; for instance, I have seen in an Ophrys a pollen-mass with its curious structure of little packets, united together and to the eaudicle by elastic thTeads, formed between the edges of an upper petal. The segments of the calyx of the common pea have been observed partially converted into carpels, including ovules, and with their tips converted into stigmas. 4Numerous analogous facts could be given.50 I do not know how physiologists look at such facts as the foregoing. According to the doctrine of pangenesis, the free and superabundant gemmules of the transposed organs are <leveloped in the wrong place, from uniting with wrong cells or aggregates of cells during their nascent state; and this would follow from a slight modification in the elective affinity of such cells, or possibly of certain gemmules. Nor ought we to feel much surprise at the affinities of cells aml gemmules varying 50 1\'loquin-Tandon, 'Teratologie Veg.,' 1841, pp. 218, 220, 353. For the case of the pea, see' Gardener's Chron.,' 1866, p. 897. CHAP. XXVII. OF PANGENESIS. 393 under domestication, when we remember the many curious cases given, in the seventeenth chapter, of cultivated plants which absolutely refuse to be fertilised by their mvn pollen or by that of the same species, but are abundantly fertile with pollen of a distinct species; for this implies that their sexual elective affinities-and this is the term used by Gartner -have been modified. As the cells of adjoining or homologous parts will have nearly the same nature, they will be liable to acquire by variation each other's elective affinities; and we can thus to a certain ext ent understand such cases as a crowd of horns on the heads in certain sheep, of several spurs on the leg, and of hackles on the head of the fowl, and with the pigeon the occurrence of wing-feathers on their legs and of membrane between their toes ; for the leg is the homologue of the wing. As all the organs of plants are homologous and spring from a common axis, it is natural that they should be eminently liable to transposition. It ought to be observed that when any compound part, such as an additional limb or an antenna, springs from a false position, it is only necessary that the few first gemmules should be wrongly attached; for these whilst developing would attract others in due succession, as in the regrowth of an amputated limb. When parts which are homologous and similar in structure, as the vertebrre in snakes or the stamens in polyandrous flowers, &c., are repeated many times in the same organism, closely allied gemmules must be extremely numerous, as well as the points to which they ought to become united ; and, in accordance with the foregoing views, we can to a certain extent lmderstand Isid. Geoffroy St. Hilaire's law, namely, that parts, which are already multiple, are extremely liable to vary in number. The same general principles apply to the fusion of homologous parts ; and with respect to mere cohesion there is probably always some degree of fusion, at least near the surface. When two embryos during their early development come into close contact, as both include corresponding gemmules, which must be in all respects almost identical in nature, it is not surprising that some derived from one embryo and some from the other should unite at the point of contact with a single nascent cell or aggregate of cells, and thus give rise to a single part or organ. For instance, two embryos might thus come to have on their |