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The excerpt represents the core issue or deciding factor on which you must meditate, and is drawn from On the Origin of Species by Charles Darwin: have wholly disappeared--the slits on the sides of the neck and the
loop-like course of the arteries still marking in the embryo their former
position. But it is conceivable that the now utterly lost branchiae might
have been gradually worked in by natural selection for some quite distinct
purpose: in the same manner as, on the view entertained by some
naturalists that the branchiae and dorsal scales of Annelids are homologous
with the wings and wing-covers of insects, it is probable that organs which
at a very ancient period served for respiration have been actually
converted into organs of flight.
In considering transitions of organs, it is so important to bear in mind
the probability of conversion from one function to another, that I will
On the Origin of Species |
