10 
bubble of air, and appears like a globe of quick- 
silver; with this she enters her cocoon, and 
displacing an equal mass of water, again 
ascends fora second lading, till she has suffi- 
ciently filled her house with it, so as to expel 
all the water. The males construct similar 
habitations by the same maneuvres. How 
these little animals can envelope their abdomen 
with an air-bubble, and retain it till they enter 
their cells, is still one of Nature’s mysteries 
that have not been’ explained.” 
We need say nothing of the habitations 
formed by solitary animals of the higher tribes, 
chiefly by burrowing under ground, for their 
own protection and comfort; but the most curi- 
ous of such solitary habitations on the earth’s 
surface are also furnished by the tribe of 
spiders. 
“ Some species of spiders, M. Audouin re- 
marks, are gifted with a particular talent for 
building: they hollow out dens; they bore 
galleries ; they elevate vaults ; they build, as it 
were, subterranean bridges ; they construct also 
entrances to their habitations, and adapt doors 
to them, which want nothing but bolts, for 
without any exaggeration, they work upon 
a_ hinge saa are fitted to a frame. The 
interior of these habitations is not less 
remarkable for the extreme neatness which 
reigns there; whatever be the humidity of the 
soil in which they are constructed, water never 
penetrates them ; the walls are nicely covered 
with a tapestry of silk, having usually the lustre 
of satin, and almost always of a dazzling white- 
ness. 
“ The habitations of the species in question 
are found in an argillaceous kind of red earth, 
in which they bore tubes about three inches in 
depth and ten lines in width. The walls of 
these tubes are not left just as they are bored, 
but are covered with a kind of mortar, suffi- 
ciently solid to be easily separated from the 
mass that surrounds it.” “ The door that closes 
the apartment is still more remarkable in its 
structure. If the well were always open, the 
spider would sometimes be subject to the intru- 
sion of dangerous guests. Providence has there- 
fore instructed her to fabricate a very secure 
trap-door which closes the mouth of it. To 
judge of this door by its outward appearance, 
te pada to be formed of a mass of earth 
coarsely worked, and covered internally by a 
solid web, which would be sufficiently wonder- 
ful for an animal that seems to have no special 
organ for constructing it; but when divided 
vertically, it is found to be a much more com- 
plicated fabric than its outward ap ce in- 
dicates, it being formed of more than thirty 
alternate layers of earth and web emboxed, as 
it were, in each other, like a set of weights for 
small scales. 
“ If these layers of web are examined, it will 
be seen that they all terminate in the hinge, so 
that the greater the volume of the door the more 
powerful is the hinge. The frame in which the 
tube terminates above, and to which the door 
is adapted, is thick, arising from the number 
of layers of which it consists, and which seem 
to correspond with those of the door; hence 
INSTINCT. 
the formation of the door, the hinge, and the © 
frame, seem to be a simultaneous operation ;— 
except that in fabricating the first, the animal 
has to knead the earth as well as to spin the 
layers of web. By this admirable arrange 
these always co! d with each 
and the strength of the hinge and the thi 
of the frame will always be proportioned 
weight of the door. : 
“* The interior surface of the cover to the 
and remarkable for a series of minute or ‘ 
placed in the side opposite the hi r 
ranged in a semicircle; there are 
of these orifices, the object of which, M. Au- 
douin conjectures, is to enable the animal to 
hold her door down in any case of emergency — 
against external force, by the insertion of her 
claws into some of them.” * , 
But the most extraordinary habitations formed — 
by the instincts of animals are those which are 
the joint result of the labours of communities; 
and here we observe the same difference as has” 
been already noticed, between the inhabitants 
of the air and of the ocean. Many of the ani+ 
mals that inhabit the latter are formed by na- 
ture, as Mr. Kirby expresses it, (and evi 
with a view to the rude shocks to which they _ 
consisting | 
are exposed,) “ into a body politic, : 
of many individuals, and distinct as 
inhabiting different cells, but still ing a 
body in common, and many of them receiving 
benefit from the systole and diastole of a com- _ 
mon organ ; thus by a natural union is sy 
lized what in terrestrial animal communities re- 
sults from numerous wills uniting to effect a_ 
eon object. The vane as far as I recol- 
ect, exhibits no instance 0 PE aye l, 
nor the ocean of one which, like the beaver, — 
lemming, bee, wasp, &c. forms associations to 
build and inhabit a common house.” + | 
And there is a curious family, named Salpa, 
in which the individuals are attached to each 
other almost like bees in their cells at birth, 
and are afterwards separated when they have 
acquired strength; thus forming the link be- 
tween the aggregated sea animals (such as Co- 
rals, Madrepores, Sertularia, Fluswa, &c.) and 
the associated land animals. | 
The habitations that are formed by animals 
} 
of the latter description, although in very diffe- | 
rent parts of the scale of beings, afford Al 
curious evidence of skill and contrivance, and | 
of the wills of numerous individuals, bound _ 
together by a common instinct, as surely as the 
materials of which the aggregate animals are 
& 
composed. Take, for example, the houses of — 
| 
A 
beavers. 
« Beavers set about building some timer | 
the month of August: those that erect their — 
habitations in small rivers or creeks in which 
the water is liable to be drained off, with won- 
derful sagacity provide against that evil by 
* Kirby, vol. ii. p. 287, et seq. 
t Kirby, vol. i. p. 222, f 
