inted, are mere rudiments, vestiges. They are hardly a
millimetre long. (.039 inch.--Translator's Note.) For this reason they
are of no use whatever for walking; they do not even bear upon the
supporting surface, being kept off it by the obesity of the chest. The
organs of locomotion are something altogether different. The grub of
the Capricorn moves at the same time on its back and belly; instead of
the useless legs of the thorax, it has a walking-apparatus almost
resembling feet, which appear, contrary to every rule, on the dorsal
surface.

The first seven segments of the abdomen have, both above and below, a
four-sided facet, bristling with rough protuberances. This the grub can
either expand or contract, making it stick out or lie flat at will. The
upper facets consist of two excrescences separated by the mid-dorsal
line; the lower ones have not this divided appearance. These are the
organs of locomotion, the ambulacra. When the larva wishes to move
forwards, it expands its hinder ambulacra, those on the back as well as
those on the belly, and contracts its front ones. Fixed to the side of
the narrow gallery by their ridges, the hind-pads give the grub a
purchase. The flattening of the fore-pads, by decreasing the diameter,
allows it to slip forward and to take half a step. To complete the step
the hind-quarters have to be brought up the same distance. With this
object, the front pads fill out and provide support, while those behind
shrink and leave free scope for their segments to contract.

With the double support of its back and belly, with alternate puffings
and shrinkings, the animal easily advances or retreats along its
gallery, a sort of mould which the contents fill without a gap. But if
the locomotory pads grip only on one side progress becomes impossible.
When placed on the smooth wood of my table, the animal wriggles slowly;
it lengthens and shortens without advancing by a hair's-breadth. Laid
on the surface of a piece of split oak, a rough, uneven surface, due to
the gash made by the wedge, it twists and writhes, moves the front part
of its body very slowly from left to right and right to left, lifts it
a little, lowers it and begins again. These are the most extensive
movements made. The vestigial legs remain inert and absolutely useless.
Then why are they there? It were better to lose them altogether, if it
be true that crawling inside the oak has deprived the animal of the
good legs with which it sta