ship. We can thus also understand
the apparent paradox, that the very same characters are analogical when
one group is compared with another, but give true affinities when the
members of the same group are compared together: thus the shape of the
body and fin-like limbs are only analogical when whales are compared
with fishes, being adaptations in both classes for swimming through
the water; but between the the several members of the whale family, the
shape of the body and the fin-like limbs offer characters exhibiting
true affinity; for as these parts are so nearly similar throughout
the whole family, we cannot doubt that they have been inherited from a
common ancestor. So it is with fishes.

Numerous cases could be given of striking resemblances in quite distinct
beings between single parts or organs, which have been adapted for the
same functions. A good instance is afforded by the close resemblance of
the jaws of the dog and Tasmanian wolf or Thylacinus--animals which are
widely sundered in the natural system. But this resemblance is confined
to general appearance, as in the prominence of the canines, and in the
cutting shape of the molar teeth. For the teeth really differ much: thus
the dog has on each side of the upper jaw four pre-molars and only two
molars; while the Thylacinus has three pre-molars and four molars.
The molars also differ much in the two animals in relative size and
structure. The adult dentition is preceded by a widely different milk
dentition. Any one may, of course, deny that the teeth in either case
have been adapted for tearing flesh, through the natural selection of
successive variations; but if this be admitted in the one case, it is
unintelligible to me that it should be denied in the other. I am glad to
find that so high an authority as Professor Flower has come to this same
conclusion.

The extraordinary cases given in a former chapter, of widely different
fishes possessing electric organs--of widely different insects
possessing luminous organs--and of orchids and asclepiads having
pollen-masses with viscid discs, come under this same head of analogical
resemblances. But these cases are so wonderful that they were introduced
as difficulties or objections to our theory. In all such cases some
fundamental difference in the growth or development of the parts, and
generally in their matured structure, can be detected. The end gained is
the same, but the means, though appearing superficiall