stances. Many have been called into existence, but few have been
chosen in the long course of animal evolution and selected as the
important means of repulsion or attraction.

There are odorous substances attached to many of the lower animals
which seem to have no significance, but just happen to be the result
of necessary chemical changes, not aimed (so to speak) at their
production. Of course, it is very difficult to form a certain and
definite conclusion as to their uselessness as odours. For instance,
nearly all the sponges when fresh and filled with living protoplasm
have a curious smell which reminds one of that given off by a stick of
phosphorus. Marine sponges have it and so has the beautiful green or
flesh-coloured liver sponge (common on the wood of rafts and weirs in
the Thames). A rather uncommon marine worm, called _Balanoglossus_ or
the acorn worm, has a very strong and unpleasant smell like that of
iodoform. In neither case is the nature of the odorous body known, nor
its use to the animal suggested. Smelts smell like cucumbers: the
green-bone fish and the mackerel smell alike. One of the common
earth-worms has a strong aromatic smell, and the common snail, as well
as the sea-hare and one of the cuttle-fishes (_Eledone_), smells like
musk. Musk itself is produced, as a scent attracting the opposite sex,
by several animals--musk-deer, musk-sheep, musk-rats. I am not now
attempting to enumerate the well-recognised odours of animals such as
are extracted from them by man in order to "opsonize" himself, but am
pointing to the more obscure cases. There is not a very great or
marked variety in the odours of fishes; but reptiles with their dry,
oily skins give off various aromatic smells, none of which are valued
by man. Toads have distinct odours, and one kind (_Pelobates fuscus_,
or the heel-clawed toad), common in Europe, but not British, is known
locally as the garlic toad on account of its smell. There are amongst
carnivorous mammals various smells allied to that of civet which are
not so agreeable to man as that substance; for instance, the odour of
the fox and of the badger, and yet more celebrated, the terrible,
awe-inspiring smell of the fluid emitted in self-defence by the skunk
from a sac in the hinder part of the body. Horses, cows, goats, sheep,
and the giraffe have their distinctive odours. Many of the herbivorous
animals secrete a colourless fluid from large glands opening on or
near the feet, and