uggle
for life, we must confess, baffles our conjectures on the subject; for that
any very appreciable gain to the individual can have resulted from the
slightly lessened degree of required nourishment thence resulting (_i.e._
from the suppression), seems to us to be an almost absurd proposition."[99]

[Illustration: HAND OF THE POTTO (PERODICTICUS), FROM LIFE.]

Again, to anticipate somewhat, the great group of whales (Cetacea) was
fully developed at the deposition of the Eocene strata. On the other hand,
we may pretty safely conclude that these animals were absent as late as the
latest secondary rocks, so that their development could not have been so
very slow, unless geological time is (although we shall presently see there
are grounds to believe it is not) practically infinite. It is quite true
that it is, in general, very unsafe to infer the absence of any animal
forms during a certain geological period, because no remains of them {106}
have as yet been found in the strata then deposited: but in the case of the
Cetacea it is safe to do so; for, as Sir Charles Lyell remarks,[100] they
are animals, the remains of which are singularly likely to have been
preserved had they existed, in the same way that the remains were preserved
of the Ichthyosauri and Plesiosauri, which appear to have represented the
Cetacea during the secondary geological period.

[Illustration: SKELETON OF A PLESIOSAURUS.]

As another example, let us take the origin of wings, such as exist in
birds. Here we find an arm, the bones of the hand of which are atrophied
and reduced in number, as compared with those of most other Vertebrates.
Now, if the wing arose from a terrestrial or subaerial organ, this abortion
of the bones could hardly have been serviceable--hardly have preserved
individuals in the struggle for life. If it arose from an aquatic organ,
like the wing of the penguin, we have then a singular divergence from the
ordinary vertebrate fin-limb. In the ichthyosaurus, in the plesiosaurus, in
the whales, in the porpoises, in the seals, and in others, we have
shortening of the bones, but no reduction in the number either of the
fingers or of their joints, which are, on the contrary, multiplied in
Cetacea and the ichthyosaurus. And even in the turtles we have eight carpal
bones and five digits, while no finger has less than two phalanges. It{107}
is difficult, then, to believe that the Avian limb was developed in any
other way than by a comp