leaves of Myriophyllum are pretty sure to be more or less studded with the erect tubes, which are quite visible to the naked eye.

On being brought under the microscope with a power of 100 or 150 diameters, you can see a tall chimney of a yellowish-brown hue, standing on a leaf, slightly widening from the bottom upwards, and terminating in an irregular edge. Presently, a pellucid body peeps from the summit, like a sweep out of the chimney-top (pardon the similitude), and, rising higher and higher, suddenly unfurls a disk of four expansive petals, not altogether unlike those of a Heart's-ease, but made of crystalline material, and set round the margins with a row of those beauteous cilia, whose dark waves chase each other in ceaseless play, up and down, round and round, in the most charming manner.

Behind the disk, which by a bend of the upper part of the body is brought to assume a vertical position, there is a little hemispherical cavity on the surface, which is lined with cilia, and this is connected by a series of cilia with the sinus of the two great upper petals of the disk.

The ciliary wave, after making the circuit of the disk, passes off behind in a great current through the sinus just alluded to, carrying with it all the floating particles that are not fit for food, or that have not been carried into the mouth. These particles are hurled along until they reach the little hemispherical cavity, in which they are caught and whirled round and round with great rapidity. Here, too, they are probably mixed with some glutinous secretion, and the effect of the gyration is the consolidation of the particles into a little globular pellet. No sooner is this ready, than the animal quickly bends forward its

body till the cavity touches the edge of its case, where the globule is deposited. The erect position is now assumed again, materials for a new globule begin to accumulate, and in a minute or two this is ready, and is deposited beside its predecessor; and thus the case is swiftly built up, brick by brick.

CHAPTER XXII.

CRUSTACEA (Crabs and Shrimps).

THE dark, mysterious world of waters hides many a "moving creature that hath life;" and the solitary pacer along the black line of sea-weed that bounds the domains of earth and sea, or the curious Paul Pry that is ever and anon peering into nooks and holes and crannies in the surge-worn rocks, is continually surprised by some strange being, some minim of existence it may be, uncouth and slow, or lithe and elegant, and rapid as lightning; dull and sombre as suits its obscure retreat, or bright and gailytinted from the solar ray; some new combination or modification of organs; some novel exhibition of instinct, habit, or function; that awakens his admiration, and, if he be accustomed to turn from the creature to the Creator, elicits the tribute of praise to Him who made all things for His own glory.

The CRUSTACEA pre-eminently make the waters their home; they are the aquatic division of that mighty host of living things, that range under the title of ARTICULATA. The Insects, Spiders, and Mites, counting their armies, as they do, by hundreds of thousands, leave, with scarcely an exception, the sea untouched; and though a goodly number of these are found in the fresh waters of river, lake,

and pool, they are few compared with the vast body. The solid earth and free air constitute their sphere of existence. The CRUSTACEA, on the other hand, though represented by a few species that crawl on the land, and more efficiently in fresh waters, mostly range the sea, dwelling, according to the diversity of their structure and instinct, from the sunny surface to the unilluminated depths; from the shallows of the shore to the boundless solitudes of the ocean; from the genial waves of the Equator to the icefields of the Pole, to "Arctos and eternal frost."

Nor let this last assertion be considered as a sounding platitude with which to sweep the sentence round gracefully; for it is literally true: as far into the dreary regions of the Pole as our bold explorers, or still hardier whalefishers have penetrated, they report the Arctic Sea to swarm with small CRUSTACEA. One little species, in particular, found in immense numbers beneath the ice, was turned to account in the temporary sojourn of the discovery expeditions in winter quarters. The men had often noticed the shrinking of their salt meat which had been put to soak, and a goose that had been frozen, on being immersed to thaw, was, in the lapse of forty-eight hours, reduced to a perfect skeleton. The officers aftewards availed themselves of the services of these industrious little anatomists, to obtain clean skeletons of such small animals as they procured, merely taking the precaution of tying the specimen in a loose bag of gauze or netting, for the preservation of any of the smaller bones that might be separated by the consumption of the ligaments.

In most respects, CRUSTACEA are so much like Insects, that the older naturalists, and the illustrious Linnæus

among the number, arranged them under the great class INSECTA. They have, however, a greater number of limbs ; the full provision being five pairs of true feet, and three pairs of organs, which (because of a certain ambiguity in their function, like that useful piece of furniture of which we read

"Contrived a double debt to pay,

A bed by night, a chest of drawers by day,")—

are called foot-jaws. Besides these, a great number of the species have five or six pairs of jointed limbs attached to the under-side of the abdomen, which are generally used for progression, and are called false-feet Their mouth is furnished with three pairs of jaws and two pairs of antennæ. It must be borne in mind, however, that the total complement of these members is not found present in every species, some of them being wanting in certain extensive groups.

The researches of a naturalist who has paid much atten

Prawn.

tion to this class, Mr Spence Bate, have shed a flood of