THE FIFTEEN-SPINED STICKLEBACK-THE HASSAR.

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THERE is a well-known marine species of this group, called the FIFTEEN-SPINED STICKLEBACK (Gasterosteus spinachia), a longbodied, long-snouted fish, with a slightly projecting lower jaw, and a row of fifteen short and sharp spines along the back. This creature makes its nest of the smaller algæ, such as the corallines, and the delicate green and purple seaweeds which fringe our coasts.

Sometimes, indeed, it becomes rather eccentric in its architecture, and builds in very curious situations. Mr. Couch, the well-known ichthyologist, mentions a case where a pair of Sticklebacks had made their nest "in the loose end of a rope, from which the separated strands hung out about a yard from the surface, over a depth of four or five fathoms, and to which the materials could only have been brought, of course in the mouth of the fish, from the distance of about thirty feet. They were formed of the usual aggregation of the finer sorts of green and red seaweed, but they were so matted together in the hollow formed by the untwisted strands of the rope, that the mass constituted an oblong ball of nearly the size of the fist, in which had been deposited the scattered assemblage of spawn, and which was bound into shape with a thread of animal substance, which was passed through and through in various directions, while the rope itself formed an outside covering to the whole."

THIS is not the only fish that is known to construct a nest. In the fresh waters of tropical America there is a genus of fish belonging to the Siluridae, and named Callichthys, from the beauty of the species. The fishes of this genus have four very long barbules hanging from the upper lip and pointing backwards, and are all mailed except part of the belly. Their general colour is green-brown, and they do not reach to any great size, eight inches being their usual length. They are generally very fat, and are much valued by the natives of Guiana, who live so much upon fish. The native name for this fish is HASSAR, and the European residents call it the HARDBACK, in allusion to its coat of shining mail.

To the naturalist, however, the chief point of interest in these fish is the fact that they are in the habit of constructing nests which are quite as well formed as those of the stickleback, and are made of grass-blades, straws, and leaves. These nests are

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 SHRIMPRemarkable 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