(b.) Like instincts may be found associated with unlike organs.

Birds with and without feet adapted for climbing live in trees; so
also do monkeys with and without flexible tails, squirrels, sloths,
pumas, &c. Mole-crickets dig with a well-pronounced spade upon their
fore-feet, while the burying-beetle does the same thing though it has
no special apparatus whatever. The mole conveys its winter provender
in pockets, an inch wide, long and half an inch wide within its
cheeks; the field-mouse does so without the help of any such
contrivance. The migratory instinct displays itself with equal
strength in animals of widely different form, by whatever means they
may pursue their journey, whether by water, land, or air.

It is clear, therefore, that instinct is in great measure independent
of bodily organisation. Granted, indeed, that a certain amount of
bodily apparatus is a sine qua non for any power of execution at all-
-as, for example, that there would be no ingenious nest without
organs more or less adapted for its construction, no spinning of a
web without spinning glands--nevertheless, it is impossible to
maintain that instinct is a consequence of organisation. The mere
existence of the organ does not constitute even the smallest
incentive to any corresponding habitual activity. A sensation of
pleasure must at least accompany the use of the organ before its
existence can incite to its employment. And even so when a sensation
of pleasure has given the impulse which is to render it active, it is
only the fact of there being activity at all, and not the special
characteristics of the activity, that can be due to organisation.
The reason for the special mode of the activity is the very problem
that we have to solve. No one will call the action of the spider