Country Walks of a Naturalist with His Children

by W. Houghton

WALK IV.

MAY.

"PAPA," said Willy, "you once told me of a very beautiful little creature, almost too small to be seen by the naked eye, that lives in water, and builds its house out of the small particles of clay or mud that float therein. The bricks are not of the shape of house bricks, but quite round. Do you not think we can find some of these animals in the course of to-day's walk? I forget the name of the creature." I know what you mean; you are speaking of a microscopic animal called Melicerta. "Oh, yes, that is its name, now I remember." I have no doubt we shall be able to obtain specimens from the canal; so we will walk along the bank for a short distance and then get into the fields again. We must take with us a clear wide-mouthed bottle, and we shall soon see whether we have captured any specimens. These exquisite little creatures attach themselves to the leaves and stems of water-plants; they are most readily seen on the finely cut leaves of the water-buttercup or spiked milfoil. The way to proceed is to place a tuft of this plant in the bottle and to hold it up to the light, and we shall soon see whether any Melicertæ are there.

MELICERTA ON WEED.

Here is plenty of water-buttercup—a very interesting plant by-the-bye, and one which is subject to much variation; for when it grows in swiftly flowing water all the leaves are very long and hair-like, but in still water there are flattened leaves as well, and the hair-like leaves are not nearly so long. You see it is now in flower; a beautiful white mass it forms in small still ponds. "Well, but, papa," said May, "the flowers are white, and I thought all buttercups were yellow." Nearly all the buttercups have yellow flowers, but there are two British species which have white blossoms, namely, this one and the little ivy-leaved buttercup, or crowfoot, as it is often called, which is found either in the water or near the water's edge. Though the ivy-leaved crowfoot is generally regarded as a species, I think it is only a variety of the one we are now looking at. Now I fish a plant out with my stick and nip off a tuft of hair-like leaves and pop it into the bottle. Have I anything here? No doubt the microscope would show countless numbers of minute animalcules, but I detect no Melicertæ. Let us try again. I nip off another tuft. There! do you see one, two, three, four little things sticking almost at right angles to some of the leaves? No, you see nothing? Well, perhaps not, for your eyes are not so accustomed to these things as mine are, but I will take out my pocket lens; there, surely you see that one close to the side of the bottle, do you not? Oh yes, you see what I mean; well, that is the case or house of a Melicerta, which animal I will describe to you, and when we get home we will look at it under the microscope. The case is about the twelfth part of an inch long and about the thickness of a horsehair, and of a reddish colour generally, though the colour depends on the nature of the material out of which the case is made. Let us sit down and put the bottle on this large stone, and I dare say some of the creatures will soon show their heads at the top of the tubes, for they are all indoors now; the disturbance caused in breaking off the bit of weed and putting it in the bottle has alarmed the Melicertæ, and very quickly they sunk within their houses of clay.

MELICERTA, ON WEED, MAGNIFIED.

Now I see one fellow slowly appearing at the top, after the manner of a chimney-sweeper, but certainly in a much more elegant form. There! it has unfolded four flower-like expansions, of which the uppermost are much the largest. The animal shows only the upper part of its body, and I can see with my pocket lens that it is somewhat transparent and whitish. But my lens has not sufficient magnifying power to reveal more, so I must tell you what I have seen of Melicerta under my compound microscope. Each of these four leaf-like lobes or expansions is surrounded with very minute hairs, which can move with great rapidity in all directions; these you will remember are called "cilia," from the resemblance to eyelashes, for which cilia is the Latin word. The motion caused by these numerous cilia lashing the water brings currents containing particles of food for the Melicerta, and materials for his house. Mr. Melicerta "is at once brick-maker, mason, and architect, and fabricates as pretty a tower as it is easy to conceive." The mouth is situated between the two large leaflets, and leads to a narrow throat, in which are the curious jaws and teeth of the animal. Below the jaws are the stomach and intestine; so you see the Melicerta, though so minute a creature, has a complex structure. "You said, papa," remarked May, "that the little creature makes its own tube; how does it do that?" Upon the upper part of the head there is a small hollow cup, which is lined with cilia, and probably also secretes some sticky fluid to make the pellets of clay adhere together; the particles of clay and mud, having been brought to the space between the leaflets by the action of the cilia, are conveyed to this little cup-shaped cavity, and are then worked about by the cilia within, till a round pellet is formed which completely fits the cavity. The little creature then bends itself down upon the tube and deposits the pellet upon it, then it raises itself up again and proceeds to form another brick, its jaws working all the time. "I wonder," said Jack, "how the little creature manages to set apart and put in its proper place the particles required for food and those required for brick-making; it would be funny if it sometimes made a mistake and put the clay in its stomach and the food in the brick machine!" It is curious, indeed, to know how the materials are put in the proper place; I suppose the Melicerta has the power to change the direction of the currents and thus to place the particles in their proper place. By rubbing a little paint, such as carmine or indigo, in some water and placing a drop upon the glass slide with the Melicerta, these currents may be readily seen; and I have more than once seen rows of coloured bricks, red or blue, which the animal moulded and then deposited on the tube! We will take the bottle home, and if you have patience I doubt not I shall be able to show you a good deal of what I have been describing; but you must have patience, for, as an excellent naturalist has said, "The Melicerta is an awkward object to undertake to show to our friends, for, as they knock at the door, she is apt to turn sulky, and when once in this mood it is impossible to say when her fair form will reappear. At times the head is wagged about in all directions with considerable vehemence, playing singular antics, and distorting her lobes so as to exhibit a Punch and Judy profile."[B]

Hark! what is that bird singing so sweetly and with such animation in the hedge? Do you hear? It is the dear little sedge-warbler; often, indeed, heard, but not so often seen, for it is fond of hiding itself in bushes or sedges. The sedge-warbler, like the migratory warblers generally, comes to us in April and leaves us in September. How often have I listened with delight to its music when returning home quite late at night in summer months! If the bird stops its music for a few moments, you have only to throw a stone among the bushes and the singing commences again. I am not clever in describing musical sounds, and I cannot describe that of the sedge-warbler, nor can I always distinguish it from the song of its near relative the reed-warbler. Both imitate the songs of other birds, and their incessant warblings and babblings at night cause them to be often mistaken for nightingales. I have generally found the nest of the sedge-warbler on the ground, on a tuft of coarse grass or sedge; the nest of the reed-warbler is supported on four or five tall reeds, and is made of the seed-branches of the reeds and long grass wound round and round; it is made deep, so that the little eggs are not tossed out when the reeds are shaken by the high winds.