Thus, as it seems to me, the leading facts in embryology, which are second
to none in importance, are explained on the principle of variations in the
many descendants from some one ancient progenitor, having appeared at a not
very early period of life, and having been inherited at a corresponding
period. Embryology rises greatly in interest, when we look at the embryo
as a picture, more or less obscured, of the progenitor, either in its adult
or larval state, of all the members of the same great class.
RUDIMENTARY, ATROPHIED, AND ABORTED ORGANS.
Organs or parts in this strange condition, bearing the plain stamp of
inutility, are extremely common, or even general, throughout nature. It
would be impossible to name one of the higher animals in which some part or
other is not in a rudimentary condition. In the mammalia, for instance,
the males possess rudimentary mammae; in snakes one lobe of the lungs is
rudimentary; in birds the "bastard-wing" may safely be considered as a
rudimentary digit, and in some species the whole wing is so far rudimentary
that it cannot be used for flight. What can be more curious than the
presence of teeth in foetal whales, which when grown up have not a tooth in
their heads; or the teeth, which never cut through the gums, in the upper
jaws of unborn calves?
Rudimentary organs plainly declare their origin and meaning in various
ways. There are beetles belonging to closely allied species, or even to
the same identical species, which have either full-sized and perfect wings,
or mere rudiments of membrane, which not rarely lie under wing-covers
firmly soldered together; and in these cases it is impossible to doubt,
that the rudiments represent wings.
Pages:
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731