their tips converted into stigmas. Numerous analogous
facts could be given.[923]

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 developed 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 and gemmules varying {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 own 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
Gaertner--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
extent 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
vertebrae 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 understand 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; a