rsued. When
the masked form was almost within reach of its victim, the mask
dropped down and shot straight out, working on a sort of elbow-shaped
lever, and at the same time revealed at its extremity a pair of
powerful mandibles. These mandibles snapped firm hold of the victim at
the base of its wriggling tail. The elbow-shaped lever drew back, till
the squirming prize was held close against its captor's face. Then
with swift jets from the turbine arrangement of its abdominal gills,
the strange monster darted back to a retreat among the weed stems,
where it could devour its prey in seclusion.

Under those inexorable jaws the tadpole soon disappeared and for a few
minutes the monster rested, working its mandibles to and fro and
rubbing them with its front legs before folding back that inscrutable
mask over its savage face. Presently a plump minnow, more than an inch
long, with a black stripe along its bronze and silver sides, swam down
close by the arrow-weed stems. The big eyes of the monster never
moved. But, suddenly, out shot the mask once more, revealing the face
of doom behind it; and those hooked mandibles fixed themselves in the
belly of the minnow. Inexorable as was the grip, it nevertheless for
the moment left unimpeded the swimming powers of the victim; and he
was a strong swimmer. With lashing tail and beating fins, he dragged
his captor out from among the weed stems. For a few seconds there was
a vehement struggle. Then the minnow was borne down upon the mud, out
in the broad sheen where, a little before, the tadpole had been
basking. Clutching ferociously with its six long legs, the conqueror
crawled over the prey and bit its backbone in two.

Swift, strong, insatiably ravenous, immeasurably fierce, the larva of
the dragon-fly (for such the little monster was) had fair title to be
called the wolf of the pool. Its appearance alone was enough to daunt
all rivals. Even the great black carnivorous water-beetle, with all
its strength and fighting equipment, was careful to give wide berth to
that dreadful, quick-darting mask. Had these little wolves been as
numerous as they were rapacious, there would soon have been left no
life at all in the pool but theirs and that of the frogs. Between
these there would have been a long and doubtful struggle, the frogs
hunting the larvae among the weed stems, and the larvae devouring the
tadpoles on their basking-grounds.

It chanced that the particular larva whose proceedi