TESTING THE CLEANNESS OF THE AIR.—Professor Dewar has recently devised a new method of testing the contamination of the air. A short time ago he exhibited before the Royal institution two samples of liquid air in glass tubes—one was made from air which had been washed to purify it from dust, soot, carbonic acid and other impurities. This, when condensed, was a pale blue liquid. The other sample was made by condensing the air of the lecture-room in which the audience was assembled, and was an opaque, blackish fluid, resembling soup in appearance.

THEIR WONDERFUL EYES.—When a fly comes from an egg, one of a family of thousands, it is soft, pulpy, white, eyeless, legless. When mature it affords the student one of the most marvelous fields in all nature, with its nerve clusters and brain, its feet like the hoofs of a rhinoceros, a thousand hollow hairs on each footpad, the wings, which make 15,000 vibrations a second, and the eyes. There are 8,000 of these, each a perfect lens.

A fly's eyes are hard, immovable and retain their form after death. As a fly cannot turn its head it has eyes in all directions. So small are these eyes that 1,000,000 would not cover the surface of a square inch. Each eye measures a thousandth part of an inch and the color is almost always red.

Each of these eyes is a lens and photographs have been taken through them. The lenses are of varying kinds—some suitable for looking off at a distance, others for things close at hand. Occasionally with his thousand eyes a fly is deceived. This is evidenced when a blue-bottle inside a room heads for the open country. He does not see the window glass and the thump with which he strikes and the angry buzz which shows his discomfiture show how mistaken he was.

To prove there is nothing extraordinary in a fly's having 8,000 eyes it is known that a certain beetle owns 50,016 eyes; a certain butterfly 34,710, a common dragonfly 25,088, and a silkworm moth 12,500.

NOTES ON ANIMALS.—The insect effects its breathing, not as men and animals do, by the lungs, but through openings in all sides of the body. It has an intricate system of tubes running through all parts of its person, through which the air is brought in contact with the legs, wings, and so on. These tubes are each protected by delicate membranes. In the fly there exist certain air pouches in addition to the tubes, which serve as reservoirs of air.

It is generally supposed that instinct unerringly teaches birds and insects the best way in which to build their homes or nests, and also to provide for their offspring. The following incident, recently under personal observation, will show that instinct is not always infallible, says the Scientific American: "A friend placed three small empty vials in an open box on a shelf, in an upright position in close contact, and they were uncorked. A short time afterward it was a matter of surprise to find that these had been appropriated by a female mud wasp. She had placed a goodly number of spiders in the center vial, doubtless intended to serve as food for her future brood, then proceeded to deposit her eggs in those on either side. She next closed tightly the mouths of all three receptacles with a hard lime cement. Having finished her work, she then doubtless went on her way, satisfied all had been done for her offspring that a thoughtful mother could do. But just think of the sensations of those little wasps when they come into existence, for, while starving in their sealed cages, they can plainly see, through the impenetrable glass walls, the bountiful supply of food which was provided for their use."

It has been supposed that the swallow is more rapid in its flight than almost any winged creature, but the dragonfly easily outwings it. An observer of insect life relates an account of a chase between a swallow and an immense dragonfly, in which the contest lasted a long time. The swallow evidently had hopes of catching the insect, but finally, after a long campaign, gave it up and let the fly escape. It has been claimed that the dragonfly was such a voracious devourer of mosquitoes that these small pests were thrown into a panic if a dragonfly approached them. It was declared that a fly confined in a room would speedily clear it of mosquitoes, but repeated experiments failed to substantiate this claim.

The dragonfly possesses the unique faculty among winged creatures, birds or insects, of flying backwards and forwards and sideways without turning its body. There are very few insects that the swallow, with its marvelous speed and dexterity, cannot catch, but the dragonfly is one them. The dragonfly without any apparent trouble, will keep a few feet ahead of a swallow for half an hour at a stretch, and no matter how swiftly the swallow flies, the dragonfly is never just there when it makes its swoop. This is because the swallow has to turn its body, while the dragonfly only reverses its wings.

The investigations of Professor Weismann have done more to solve the problem, "How death came into the world" than those of any other living man. It is generally assumed that death is associated with all forms of life, but this is not really the case. The lower forms of life, for example, may be said to have a perpetual existence, and not to be subject to death; for in unicellular reproduction life is practically endless. In the case of higher forms of life death is universal, and for a very natural reason. The aim of nature is the perpetuation of the species, not of the individual, and when creatures have, as in the case of certain insects, reproduced themselves once for all, they have no further need of existence. Creatures that nurse their young, like mammals, and produce them slowly, have need of longer life, or the species would speedily be exterminated; but there is no reason why the individual, having performed its duty in relation to the species, should continue to exist, since its existence then becomes a superfluity. Between multicellular and unicellular existence there is, therefore, the marked difference that, whereas the former dies when it has reproduced itself and so perpetuated its species, the latter goes on perpetually reproducing itself—one cell growing out of another without cessation. To Weismann we owe the knowledge of how it is that death intervenes when multicellular existence develops from unicellular. The change is effected by the differentiation of the individual—or somatic—and the reproductive cells. The former have lost the power of multiplication and reproduction, and consequently died, while the latter have preserved it.

The most curious of all objects in New Zealand is that which the Maoris call "aweto." One is uncertain whether to call it an animal or a plant. In the first stages of its existence it is simply a caterpillar about three or four inches in length, and always found in connection with the rata tree, a kind of flowering myrtle. It appears that when it reaches full growth it buries itself two or three inches under ground, where, instead of undergoing the ordinary chrysalis process, it becomes gradually transformed into a plant, which exactly fills the body, and shoots up at the neck to a height of eight or ten inches. This plant resembles in appearance a diminutive bulrush; and the two, animal and plant, are always found inseparable. One is apt to relegate it to the domain of imagination, among dragons and mermaids; but then its existence and nature have been accepted by the late Frank Buckland. How it propagates its species is a mystery. One traveler, after describing its dual nature, calmly states that it is the grub of the night butterfly. If so, then the grub must also become a butterfly, or what becomes of the species? One would be ready to suppose that the grub does really so, and that some fungus finds the cast-off slough congenial quarters for its growth. But as far as present observation goes the grub never becomes a butterfly, but is changed in every case into a plant.

A TAME TARANTULA.—A half-breed boy of Mexican and Indian blood recently attracted much attention at Winslow, Ariz., by the performances of an educated tarantula he owns. He carries the big, formidable-looking insect in a large wooden box slung about his neck, which, when exhibiting his pet, he places on the ground as a sort of stage. At the command of its master the tarantula mounted a small ladder, rung a bell and performed on a miniature trapeze. Then to the thumping of a tambourine in the hands of the boy, it proceeded to revolve slowly about as if waltzing, and when it had finished saluted the crowd by lifting one leg three times.

After its performance was over, it crawled to its master's shoulder, where it sat, occasionally running round his neck or down into his bosom. The boy says he tamed the spider when it was young, first by feeding it every day until it grew accustomed to him, then gradually taught it the tricks it knows. He declares that it is much more intelligent than any dog, and very tractable, though uncompromising in its enmity to any one but himself. It is as large as a silver dollar when curled up, though its legs are two or three inches long.

The body is an ugly, dull brown, covered with short, coarse, black hair, which also covers the limbs, but is very sparse and bristly. The eyes are small and gleam like diamond points, while the mouth is furnished with slender, overlapping fangs. The power of spring in these creatures is said to be something incredible, a leap of ten feet being no tremendous exertion. The boy, who owns the only one which has ever made friends with any other living creature, is from the Magollon mountains.

A story is told by George W. Griffin, of Henderson county, of a shepherd dog owned by him, which certainly demonstrates the superior instinct of this little woolly creature over most species of the canine family. "One day," said that gentleman, "I was driving along the public highway, and the dog was following me. I stopped to talk to some friends that I met, and while conversing with them unknowingly dropped my watch from my vest pocket. The watch had a short piece of leather attached to it, which answered for a fob. As soon as the chat ended I got into my buggy, and drove on. I had driven half a mile or more, when, to my astonishment, I noticed the dog was trotting along close behind the vehicle with the watch hanging from his mouth by the leather strap, which he held firmly between his teeth. Of course, I made haste to stop, and get out of the buggy. As I did so the dog came up to me wagging his tail, seemingly conscious and proud of what he had done. This, though, is just one of the many intelligent acts to that little animal's credit."—Louisville Post.

When a dog barks at night in Japan the owner is arrested, and sentenced to work for a year for the neighbors whose slumbers may have been disturbed.