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comprising water fleas, fresh water shrimps, the water-louse, 
shrimps, prawns, &c., some breathe by flabelliform appendages 
attached to the feet, others by laminated plates in cavities at the 
sides of the thorax. Insects, many of them, especially flies, are 
in their larval state inhabitants of the water, and breathe through 
their tails, which they apply to the surface ; when metamorphosed 
into flies, they breathe through pores, situated on the sides on the 
body. The gnat, at its first metamorphosis, breathes with its tail ; 
in its second by two tubes attached to the head; in its last, when 
a flying insect, by pores or stigmata on the sides of its body ; the 
wings are also permeated with breathing tubes. Caterpillars have 
pores on the side of the body, frequently protected by a sieve-like 
membrane, which prevents the entrance of dust. Among spiders, 
which breathe by pores leading to air sacs or lungs within their 
bodies, is the water spider, and in proof that its habits are most 
interesting, Mr. Johnson said—I kept some of the water spiders 
in an aquarium for two months or more, and watched their pro- 
ceedings. The Argynoreta comes to the surface head foremost, 
assisted by a thread attached to a leaf or some other object by 
one end, aud to the surface of the water by the other; it turns up 
the point of its abdomen, and catches a bubble of air; this is 
retained amongst some hairs on the under part of the body, and 
produces a shining metallic appearance. With this bubble it dives, 
and leaves it attached to the plant at the end of the thread under 
water. The same operation is repeated frequently until the aerial 
home is large enough. Around this it spins a web to strengthen 
it, and, when finished, creeps in and there lies in wait for prey. I 
have seen the males build their dwellings side by side, and noticed 
the male visit the female, both living in one compartment. After 
a time my aquarinm was dotted over with little balls or cocoons 
like cotton, and not very long after a swarm of young ones made 
their appearance. Many of these crawled out of the water and 
perished ; the remainder soon disappeared, and disappointed me of 
the pleasure of rearing them. I believe they were eaten by their 
parents. How these spiders get into and out of their bubble 
homes, without allowing the air to escape is, to me, a mystery. 
Molluscous animals: Amongst these are the oyster, scallop, 
and mussel; these breathe by ciliated laminated plates (com- 
monly called the beards), producing a constant current of sea 
water in and out of their shells, thus obtaining the necessary 
oxygen for respiration. In the garden snail, an opening exists 
on the right side near the head, leading to a pulmonary air sac 
or lung. During hybernation the shell is closed by a natural 
cement, which is perforated for the admission of air. The aquatic 
water snails come to the surface to breathe; most of these propa- 
gate by eggs; one, as an exception, brings forth its young alive ; 
openings for the admission of air exist on the side of the head, 
