“The copulatory apparatus of
the male dragonfly is one of the most remarkable
structures in the Animal Kingdom. The “papal
organ” on the pedipalp of the male spider,
and the hectoctylous arm of the Cephalopod
Mollusc, extraordinary as they are, do not defy all
explanation, since in each case they are modifications
of an appendage already present. But the
apparatus of the male dragonfly is not homologous
[similar] with any known organ in the Animal Kingdom; it
is not
derived from any pre-existing
organ: and its origin, therefore, is as complete a
mystery as it well could be.”
R. J. Tillyard, The
Biology of the Dragonfly, Cambridge University Press, Cambridge,
p. 215