a period of seven hundred and sixty-eight
hours, when he found them with their vital
energies unsuspended. Some individuals of
other species, after six, fourteen, or twenty-
eight days, he has found exercising their
functions and spinning their lines, as if they were in
the air. Many individuals of other species,
however, have not survived even for a single hour.
But certain species of spiders, undoubtedly,
can live a long time under water without
being adapted for it by any known peculiarities
of organisation. How this is done, and whether
or no by a power of extracting respirable air
from water is one of the many puzzles which
still challenge the ingenuity and inquisitions of
naturalists.

The observer of the pools, while noticing how
the skaters scud along by successive pushes of
the legs with long beaks or long tongs to seize
their prey, will sometimes be startled by a flash
of polished silver just under the surface of the
water. Of course he fancies it is the silver
spider. But it is far more likely to be the boat
fly, the back-swimmer (Notonecta). This half-
wing (Hemiptera) has, like the water spider, the
faculty of covering his body with a silvery plating
of air. Lying upon his back, he breathes at
the extremity of his abdomen, which is
surrounded by a circular palisade of bristles resting
upon the surface of the water; and, watching
in the stream beneath him and air above him, he
is ready to dart in any direction to escape an
enemy or seize a victim, with a few strokes of
his oars. Notonecta and Argyroneta are two of
a trade, although they differ widely in their
organisation.

The eyes of the silver spider are disposed
crosswise on the fore part ot the head-chest, in
two rows, the intervening ones of the fore row
placed on a small prominence being smallest,
forming with those of the hind row an unequal
four-sided figure (trapezoid), whose shortest side
is in front; each side-pair being set obliquely on
a tubercle. The lower jaw is powerful, rounded
at the end, and inclined towards the lip. The
lip is long, triangular, dilated at the base, and
rounded at the apex. Legs robust; the first
pair is the longest, then the fourth, the third
pair being the shortest.

Length of the female, nine-twentieths of an
inch; length of the head-chest, one-fifth; breadth,
three-twentieths; breadth of the abdomen, one-
fifth; length of a fore-leg, three-fifths; length
of a leg of the third pair, nine-twentieths.

Each side pair of eyes is set obliquely on a
tubercle, but are not near. The head-chest is glossy,
compressed before, bombed at the fore part,
somewhat depressed on the sides, which are marked
with furrows converging towards the middle,
and slightly hairy: the pincers or fangs are
powerful, conical, vertical, divergent at the
extremity, and armed with three teeth on the fore,
and two on the hind side of the space which
receives the fang when in a state of repose; the
lower jaws are strong and slightly inclined
towards the lip, which is triangular, and rounded
at the top; the breast is heart-shaped and
densely covered with long hair; the legs are
amply supplied with hairs, those on the third
and fourth pairs being the longest and most
abundant; each foot  is terminated by three
claws; the two superior ones are curved and
deeply coombed  (pectenated), and the inferior
one is bent near its base; the feelers are slender
and have a curved pectenated claw at their
extremity. These parts are of a dark-brown colour,
faintly tinged with red; the fangs, lower jaw, lip,
and breast, being the darkest. The body is egg-
shaped, broader at the fore than at the hind
end, bombed above, projecting over the base of
the head-chest; it is densely covered with hairs,
those on the under part being much the longest
and is of an olive-brown colour: four minute
circular depressions of a darker hue situated on
the upper part describe a quadrilateral figure
whose foremost side is the shortest.

The sexes resemble each other, but the male
is decidedly the larger. Argyroneta aquatica
lives most of its life in the water. Looking
like an egg of living silver, it darts and flashes
about from the bottom to the surface, and from
the surface to the bottom in pursuit of its prey.
"It constructs beneath the surface of the
water," says Mr. Blackwell, " a dome-shaped
cell, in which is placed its cocoon of white silk,
of a compact texture and lenticular form [a lens-
like or doubly-bombed form] containing from
eighty to a hundred spherical eggs, of a yellow
colour, not agglutinated together. This cell is
supported in a vertical position, the open part
being directed downwards, by lines of silk
connecting it with aquatic plants, and as it
comprises a considerable quantity of atmospheric
air, the spider can at all times occupy it without
experiencing the least inconvenience. In
swimming and diving Argyroneta aquatica
assumes an inverted position, and is more or less
enveloped in air confined by the circumambient
water among the hairs with which it is clothed,
the supply being always more abundant on the
under than on the upper part, in consequence of
the greater length and density of the hairs
distributed over its surface.

This species is found in pools and ditches in
various parts of England. It is of frequent
occurrence in the fens of Cambridgeshire, from
which locality a pair was transported to Crumpsall
Hall, near Manchester, in the summer of
1833. Each individual was enclosed in a small
tin box, and neither of them appeared to suffer
materially from the confinement. After a lapse
of ten days, during which period they were without
water, they speedily formed a dome-shaped
cell beneath the surface attaching it to the side
of the glass, by means of numerous silken lines,
and being well supplied with insects, it lived in
this state of captivity till the commencement of
winter, when, on the temperature of the room
in which it was kept becoming much more
reduced, it entered the cell, and remained there
in a state of torpidity, with its head downwards.
A gentleman on a visit at the house, whose
curiosity to examine the spider minutely in its
hybernaculum was greater than his prudence,