se-organs
conceive it. It must perceive effluvia of another order as well;
entirely mysterious to us, and therefore not utilised. Light has its
dark rays--rays without effect upon our retinas, but not apparently on
all. Why should not the domain of smell have its secret emanations,
unknown to our senses and perceptible to a different sense-organ?

If the scent of the dog leaves us perplexed in the sense that we cannot
possibly say precisely, cannot even suspect what it is that the dog
perceives, at least it is clear that it would be erroneous to refer
everything to human standards. The world of sensations is far larger
than the limits of our own sensibility. What numbers of facts relating
to the interplay of natural forces must escape us for want of
sufficiently sensitive organs!

The unknown--that inexhaustible field in which the men of the future
will try their strength--has harvests in store for us beside which our
present knowledge would show as no more than a wretched gleaning. Under
the sickle of science will one day fall the sheaves whose grain would
appear to-day as senseless paradoxes. Scientific dreams? No, if you
please, but undeniable positive realities, affirmed by the brute
creation, which in certain respects has so great an advantage over us.

Despite his long practice of his calling, despite the scent of the
object he was seeking, the _rabassier_ could not divine the presence of
the truffle, which ripens in winter under the soil, at a depth of a foot
or two; he must have the help of a dog or a pig, whose scent is able to
discover the secrets of the soil. These secrets are known to various
insects even better than to our two auxiliaries. They have in
exceptional perfection the power of discovering the tubers on which
their larvae are nourished.

From truffles dug up in a spoiled condition, peopled with vermin, and
placed in that condition, with a bed of fresh sand, in a glass jar, I
have in the past obtained a small red beetle, known as the
truffle-beetle (_Anisotoma cinnamomea_, Panz.), and various Diptera,
among which is a Sapromyzon which, by its sluggish flight and its
fragile form, recalls the _Scatophaga scybalaria_, the yellow velvety
fly which is found in human excrement in the autumn. The latter finds
its refuge on the surface of the soil, at the foot of a wall or hedge or
under a bush; but how does the former know just where the truffle lies
under the soil, or at what depth? To penetrate to