r; they were carefully closed up with a plug of wood, so as to
exclude access of insects, and apparently were air-tight; when examined
at the end of a year, every one of the Toads was dead, and their bodies
were decayed.

"From the fatal result of the experiments made in the small cells cut in
the apple-tree and the block of compact sandstone, it seems to follow
that Toads cannot live a year excluded totally from atmospheric air;
and, from the experiments in the larger cells within the block of
oolitic limestone, it seems also probable that they cannot survive two
years entirely excluded from food; we may therefore conclude that there
is a want of sufficiently minute and accurate observation in those so
frequently recorded cases, where Toads are said to be found alive within
blocks of stone and wood, in cavities that had no communication whatever
with the external air. The fact of my two Toads having increased in
weight at the end of the year, notwithstanding the care that was taken
to inclose them perfectly by a luting of clay, shews how very small an
aperture will admit of insects sufficient to maintain life. In the cell
No. 5, where the glass was slightly cracked, the communication though
small was obvious, but in the cell No. 9, where the glass cover remained
entire, and where it appears certain, from the increased weight of the
inclosed animal, that insects must have found admission, we have an
example of these minute animals finding their way into a cell to which
great care had been taken to prevent any possibility of access.

"Admitting, then, that Toads are occasionally found in cavities of wood
and stone with which there is no communication sufficiently large to
allow the ingress and egress of the animal inclosed in them, we may, I
think, find a solution of such phenomena in the habits of these
reptiles, and of the insects which form their food. The first effort of
the young Toad, as soon as it has left its tadpole state and emerged
from the water, is to seek shelter in holes and crevices of rocks and
trees. An individual which, when young, may have thus entered a cavity
by some very narrow aperture, would find abundance of food by catching
insects, which, like itself, seek shelter within such cavities; and may
soon have increased so much in bulk as to render it impossible to get
out again through the narrow aperture at which it entered. A small hole
of this kind is very likely to be overlooked by common workme