in a spire. In
monstrous plants, we often get direct evidence of the possibility of one
organ being transformed into another; and we can actually see, during
the early or embryonic stages of development in flowers, as well as
in crustaceans and many other animals, that organs, which when mature
become extremely different are at first exactly alike.

How inexplicable are the cases of serial homologies on the ordinary view
of creation! Why should the brain be enclosed in a box composed of
such numerous and such extraordinarily shaped pieces of bone apparently
representing vertebrae? As Owen has remarked, the benefit derived
from the yielding of the separate pieces in the act of parturition by
mammals, will by no means explain the same construction in the skulls of
birds and reptiles. Why should similar bones have been created to
form the wing and the leg of a bat, used as they are for such
totally different purposes, namely flying and walking? Why should one
crustacean, which has an extremely complex mouth formed of many parts,
consequently always have fewer legs; or conversely, those with many
legs have simpler mouths? Why should the sepals, petals, stamens, and
pistils, in each flower, though fitted for such distinct purposes, be
all constructed on the same pattern?

On the theory of natural selection, we can, to a certain extent, answer
these questions. We need not here consider how the bodies of some
animals first became divided into a series of segments, or how they
became divided into right and left sides, with corresponding organs, for
such questions are almost beyond investigation. It is, however, probable
that some serial structures are the result of cells multiplying by
division, entailing the multiplication of the parts developed from
such cells. It must suffice for our purpose to bear in mind that
an indefinite repetition of the same part or organ is the common
characteristic, as Owen has remarked, of all low or little specialised
forms; therefore the unknown progenitor of the Vertebrata probably
possessed many vertebrae; the unknown progenitor of the Articulata, many
segments; and the unknown progenitor of flowering plants, many leaves
arranged in one or more spires. We have also formerly seen that parts
many times repeated are eminently liable to vary, not only in number,
but in form. Consequently such parts, being already present in
considerable numbers, and being highly variable, would naturally afford
t