very plentiful in the little muddy streamlets that intersect the sugar marshes, so that the habits of the. fish can be easily watched. The parent fish is very jealous of the eggs, and waits near them until they are hatched, and the young family committed to the water. The natives are well aware of this habit, and catch the fish readily by insinuating a net or even a basket under the water near a nest, and then raising it quickly, when the parent fish is mostly found in the net.

Perhaps the most curious part of the economy of this fish is the fact that the nest is not placed in the water, but in a muddy hole just above the surface. This habit, however, accords with the qualities of the fish, which is remarkably independent of water, and can travel over land from one pond to another, led by some mysterious instinct, which we of higher powers cannot comprehend. During the dry season the Hassar is in the habit of burrowing into the mud, and there residing until the welcome rain sets it free. Those who know the customs of the fish are therefore able to procure it at almost any period of the year, digging for it in the dry season, and fishing for it in the wet months.

CHAPTER XX.

INVERTEBRATES.

A Pool and its wonders-The WATER SPIDER-Its sub-aquatic nest-Conveyance of air to the nest-The diving-bell anticipated-Character of the air in the nest-Mr. Bell's experiments upon the Spider-Life of the Water Spider-The HYDRACHNA-The CADDIS FLIES and their characteristics-Sub-aquatic homes of the Larva-Singular varieties of form and material-Life of a Caddis-Description of nests in my own collection-Fixed cases, and modification of Larva -Singular materials for nest-building-CORALS and their general history—The Coral of commerce-Development and extension of the Coral-How fresh colonies are founded-Various Corals and their growth-Submarine tubemakers-The SERPULE and their general habits — The Operculum of the Serpula-The TEREBELLE and their submarine houses-The CADDIS SHRIMP— Remarkable analogy.

WHEN I was a very little boy, I was accustomed to spend much time on the banks of the Cherwell, and used to amuse myself by watching the various inhabitants of the water. Animal life is very abundant in that pleasant little river, and there was one favourite nook where a branch of a weeping-willow projected horizontally, and afforded a seat over the dark deep pool, one side of which was abrupt and the other sloping.

Here the merry gyrini ran their ceaseless rounds, and the waterboatmen rowed themselves in fitful jerks, or lay resting in a contemplative manner on their oars. Now and then an unlucky insect would fall from the tree into the water, and then uprose from the dark depth a pair of dull eyes and a gaping mouth, and then, with a glitter as of polished silver, the dace would disappear with its prey. In the shelving part of the pool the caddis-worms moved slowly along, while the great dyticus beetle would rise at intervals to the surface, jerk the end of his tail into the air, and then dive below to the muddy bottom. This spot was much favoured by the nursemaid, for she had no trouble in watching me, as long as I could sit on the branch and look into

the water. True, I might have fallen into the river, but I never did; and even had that accident occurred, it would have wrought no harm, except wet clothes, for I could swim nearly as well as the water-insects themselves.

Close under the bank lived some creatures which always interested me greatly. Spiders they certainly were, but they

appeared to have the habits of the water-beetle-coming slowly to the surface of the water, giving a kind of flirt in the air, and then disappearing into the depths, looking like balls of shining silver as they sank down. I had been familiar with these creatures for years before I met with them in some book, and

learned that they were known under the name of WATER SPIDER (Argyronetra aquatica).

This Spider is a most curious and interesting creature, because it affords an example of an animal which breathes atmospheric air constructing a home beneath the water, and filling it with the air needful for respiration.

The sub-aquatic cell of the Water Spider may be found in many rivers and ditches, where the water does not run very swiftly. It is made of silk, as is the case with all spiders' nests, and is generally egg-shaped, having an opening below. This cell is filled with air; and if the Spider be kept in a glass vessel, it may be seen reposing in the cell, with its head downwards, after the manner of its tribe. The precise analogy between this nest and the diving-bell of the present day is too obvious to need a detailed account. How the air is introduced into the cell is a problem that was for some time unsolved. The reader is probably aware that the bubbles of air which are to be seen on sub-aquatic plants are almost entirely composed of oxygen gas, which is exuded from the plant, and which is so important an agent in purifying the water. Some zoologists thought that the air which is found in the cell of the Water Spider was nothing but oxygen that had been exuded from the plant upon which the nest was fixed, and that it had been intercepted in its passage to the surface. In order to set the question at rest, Mr. Bell, the well-known naturalist, instituted a series of experiments upon the Spider, and communicated the results to the Linnean Society. The experiments were made in 1856, and Mr. Bell's remarks are as follows:

"No. 1. Placed in an upright cylindrical vessel of water, in which was a rootless plant of Stratiotes, on the afternoon of November 14. By the morning it had constructed a very perfect oval cell, filled with air, about the size of an acorn. has remained stationary up to the present time.

In this it

"No. 2. Nov. 15. In another vessel, also furnished with Stratiotes, I placed six Argyronetræ. The one now referred to began to weave its beautiful web about five o'clock in the afternoon. After much preliminary preparation, it ascended to the surface, and obtained a bubble of air, with which it immediately and quickly descended, and the bubble was disengaged from the body, and left in connexion with the web. As the nest was,

Onl one side, in contact with the glass, inclosed in an angle formed by two leaves of the Stratiotes, I could easily observe all its movements. Presently it ascended again and brought down another bubble, which was similarly deposited.

"In this way, no less than fourteen journeys were performed, sometimes two or three very quickly one after another; at other times with a considerable interval between them, during which time the little animal was employed in extending and giving shape to the beautiful transparent bell, getting into it, pushing it out at one place, and amending it at another, and strengthening its attachments to the supports. At length it seemed to be satisfied with its dimensions, when it crept into it and settled itself to rest with the head downwards. The cell was now the size and nearly the form of half an acorn cut transversely, the smaller and rounded part being uppermost.

"No. 3. The only difference between the movements of this and the former was, that it was rather quicker in forming its cell. In neither vessel was there a single bubble of oxygen evolved by the plant.

"The manner in which the animal possesses itself of the bubble of air is very curious, and as far as I know, has never been exactly described. It ascends to the surface slowly, assisted by a thread attached to the leaf or other support below and to the surface of the water. As soon as it comes near the surface, it turns with the extremity of the abdomen upwards, and exposes a portion of the body to the air for an instant, then with a jerk it snatches, as it were, a bubble of air, which is not only attached to the hairs which cover the abdomen, but is held on by the two hinder legs, which are crossed at an acute angle near their extremity, this crossing of the legs taking place at the instant the bubble is seized. The little creature then descends more rapidly and regains its cell, always by the same route, turns the abdomen within it, and disengages the bubble.

"No. 4. Several of them, when I received them, had the hair on the abdomen wetted, and I placed them on some blottingpaper until they were dry. On returning them to the water, two remained underneath a floating piece of cork, and the hair, being now dry, retained the pellicle of air which is ordinarily observed. One of the two came out of the water, attached the cork to the glass, and wove a web against the latter, against