r the sake of symmetry," or in order "to
complete the scheme of nature;" but this seems to me no explanation,
merely a restatement of the fact. Would it be thought sufficient to
say that because planets revolve in elliptic courses round the sun,
satellites follow the same course round the planets, for the sake of
symmetry, and to complete the scheme of nature? An eminent physiologist
accounts for the presence of rudimentary organs, by supposing that they
serve to excrete matter in excess, or injurious to the system; but can
we suppose that the minute papilla, which often represents the pistil
in male flowers, and which is formed merely of cellular tissue, can thus
act? Can we suppose that the formation of rudimentary teeth which are
subsequently absorbed, can be of any service to the rapidly growing
embryonic calf by the excretion of precious phosphate of lime? When a
man's fingers have been amputated, imperfect nails sometimes appear on
the stumps: I could as soon believe that these vestiges of nails have
appeared, not from unknown laws of growth, but in order to excrete horny
matter, as that the rudimentary nails on the fin of the manatee were
formed for this purpose.

On my view of descent with modification, the origin of rudimentary
organs is simple. We have plenty of cases of rudimentary organs in our
domestic productions,--as the stump of a tail in tailless breeds,--the
vestige of an ear in earless breeds,--the reappearance of minute
dangling horns in hornless breeds of cattle, more especially, according
to Youatt, in young animals,--and the state of the whole flower in the
cauliflower. We often see rudiments of various parts in monsters. But
I doubt whether any of these cases throw light on the origin of
rudimentary organs in a state of nature, further than by showing that
rudiments can be produced; for I doubt whether species under nature ever
undergo abrupt changes. I believe that disuse has been the main agency;
that it has led in successive generations to the gradual reduction of
various organs, until they have become rudimentary,--as in the case of
the eyes of animals inhabiting dark caverns, and of the wings of birds
inhabiting oceanic islands, which have seldom been forced to take
flight, and have ultimately lost the power of flying. Again, an organ
useful under certain conditions, might become injurious under others,
as with the wings of beetles living on small and exposed islands; and in
this case natura