nerets. A pale purple is faintly diffused over the sides.

[Footnote 6: Cf. _The Life of the Spider_: chaps. ii., vii., xi. and
xiii.--_Translator's Note_.]

Examined from the outside with the lens, the black parts reveal
nothing out of the common. The black is homogeneous and everywhere of
equal depth. On the other hand, in the coloured portions, we see
little polygonal, granular masses, forming a close-meshed network. By
cutting round the circumference of the abdomen with a pair of
scissors, the horny integument of the dorsal surface may readily be
removed in one piece, without any shreds of the organs which it
protected. This large strip of skin is transparent in the zones that
correspond with the white bands in the natural state; it is black or
yellow on the black or yellow bands. These last indeed owe their
colouring to a layer of pigment which the point of a paintbrush will
easily loosen and remove.

As for the white bands, their origin is this: once the skin has been
removed, the dorsal surface of the abdomen, whose graceful mosaic is
not in any way disturbed, reveals a layer of polygonal white spots,
distributed in belts, here densely and there less so. The denser belts
correspond with the white bands. It is their magnificent opaque white
granulations which, seen through the transparent skin, form the
snow-white stripes in the live Spider.

Treated with nitric acid on the microscopic slide, they do not
dissolve nor produce effervescence. Uric acid then is not present in
this case; and the substance must be guanine, an alkaloid known to be
the urinary product of the Spiders. The same is true of the yellow,
black, purple or orange pigment that forms a coating under the skin.
In short, by utilizing, in a different chemical combination, the waste
products of animal oxidization, the magnificent Spider rivals the
magnificent caterpillar; she beautifies herself with guanine as the
other does with its uric acid.

Let us abridge this dry subject; let us be content with these few
data, which could if necessary be corroborated by many others. What
does the little that we have learnt teach us? It tells us that the
materials rejected by the organism, guanine, uric acid and other dross
from life's refinery, play an important part in the coloration of the
insect.

Two cases are distinguishable, according as the colour is dyed or
simply painted. The skin, itself colourless and transparent, is in
places illumined by a co