eat-
rays coming from the outside and converted into movement by the organism.
This is nutrition of energy reduced to its simplest expression: the
motive heat, instead of being extracted from the food, is utilized
direct, as supplied by the sun, which is the seat of all life. Inert
matter has disconcerting secrets, as witness radium; living matter has
secrets of its own, which are more wonderful still. Nothing tells us
that science will not one day turn the suspicion suggested by the Spider
into an established truth and a fundamental theory of physiology.

APPENDIX: THE GEOMETRY OF THE EPEIRA'S WEB

I find myself confronted with a subject which is not only highly
interesting, but somewhat difficult: not that the subject is obscure; but
it presupposes in the reader a certain knowledge of geometry: a strong
meat too often neglected. I am not addressing geometricians, who are
generally indifferent to questions of instinct, nor entomological
collectors, who, as such, take no interest in mathematical theorems; I
write for any one with sufficient intelligence to enjoy the lessons which
the insect teaches.

What am I to do? To suppress this chapter were to leave out the most
remarkable instance of Spider industry; to treat it as it should be
treated, that is to say, with the whole armoury of scientific formulae,
would be out of place in these modest pages. Let us take a middle
course, avoiding both abstruse truths and complete ignorance.

Let us direct our attention to the nets of the Epeirae, preferably to
those of the Silky Epeira and the Banded Epeira, so plentiful in the
autumn, in my part of the country, and so remarkable for their bulk. We
shall first observe that the radii are equally spaced; the angles formed
by each consecutive pair are of perceptibly equal value; and this in
spite of their number, which in the case of the Silky Epeira exceeds two
score. We know by what strange means the Spider attains her ends and
divides the area wherein the web is to be warped into a large number of
equal sectors, a number which is almost invariable in the work of each
species. An operation without method, governed, one might imagine, by an
irresponsible whim, results in a beautiful rose-window worthy of our
compasses.

We shall also notice that, in each sector, the various chords, the
elements of the spiral windings, are parallel to one another and
gradually draw closer together as they near the centre. With