eap a delightful harvest; but the difficulties are
great, it seems, so much so that science cannot yet tell us the why
and the wherefore of the humblest costume. The answer will come in a
remote future, if indeed it ever comes completely, for life's
laboratory may well contain secrets denied to our retorts. For the
moment, I shall perhaps be contributing a grain of sand to the future
palace if I describe the little that I have seen.

My basic observation dates a long way back. I was at that time busy
with the Hunting Wasps, following their larval development from the
egg to the cocoon. Let us take an instance from my notes, which cover
nearly all the game-hunters of my district. I will choose the larva of
the Yellow-winged Sphex,[4] which, with its convenient size, will
furnish an easy object-lesson.

[Footnote 4: Cf. _The Hunting Wasps_: chap. iv.--_Translator's Note_.]

Under the transparent skin of the larva, which has been recently
hatched and is consuming its first Cricket, we soon perceive some fine
white spots, which rapidly increase in size and number and eventually
cover the whole body, except the first two or three segments. On
dissecting the grub, we find that these spots have to do with the
adipose layer, of which they form a considerable part, for, far from
being scattered only on the surface, they run through its whole
thickness and are present in such numbers that the forceps cannot
seize the least fragment of this tissue without picking up a few of
them.

Though perfectly visible without the help of a lens, these puzzling
spots call for the microscope if we wish to study them in detail. We
then find that the adipose tissue is made up of two kinds of vesicles:
some, bright yellow and transparent, are filled with oily drops; the
rest, opaque and starch-white, are distended with a very fine powder,
which spreads in a cloudy trail when the vesicle containing it is
broken on the object-slide. Intermingled without apparent order, the
two kinds of bags are of the same shape and the same size. The first
go to make up the nutritive reserves, the fatty tissue properly
so-called; the second form the white dots which we will study for a
moment.

An inspection under the microscope tells us that the contents of the
white cells are composed of very fine, opaque grains, insoluble in
water and of greater density. The use of chemical reagents on the
object-slide proves that nitric acid dissolves these grains, with