When the sun beats upon the glass pond, the work of the water weeds is a sight to behold. The green-carpeted reef is lit up with an infinity of scintillating points and assumes the appearance of a fairy lawn of velvet, studded with thousands of diamond pin's heads. From this exquisite jewelry pearls break loose continuously and are at once replaced by others in the generating casket; slowly they rise, like tiny globes of light. They spread on every side. It is a constant display of fireworks in the depths of the water.
Chemistry tells us that, thanks to its green matter and the stimulus of the sun's rays, the weeds decompose the carbonic acid gas wherewith the water is impregnated by the breathing of its inhabitants and the corruption of the organic refuse; it retains the carbon, which is wrought into fresh tissues; it exhales the oxygen in tiny bubbles. These partly dissolve in the water and partly reach the surface, where their froth supplies the atmosphere with an excess of breathable gas. The dissolved portion keeps the colonists of the pond alive and causes the unhealthy products to be oxidized and disappear.
Old hand though I be, I take an interest in this trite marvel of a bundle of weeds perpetuating hygienic principles in a stagnant pool; I look with a delighted eye upon the inexhaustible spray of spreading bubbles; I see in imagination the prehistoric times when seaweed, the first-born of plants, produced the first atmosphere for living things to breathe at the time when the silt of the continents was beginning to emerge. What I see before my eyes, between the glass panes of my trough, tells me the story of the planet surrounding itself with pure air.
CHAPTER VIII. THE CADDIS WORM
Whom shall I lodge in my glass trough, kept permanently wholesome by the action of the water weeds? I shall keep caddis worms, those expert dressers. Few of the self-clothing insects surpass them in ingenious attire. The ponds in my neighborhood supply me with five or six species, each possessing an art of its own. Today, but one of these shall receive historical honors.
I obtain it from the muddy bottomed, stagnant pools crammed with small reeds. As far as one can judge from the habitation merely, it should be, according to the specialists, Limnophilus flavicornis, whose work has earned for the whole corporation the pretty name of Phryganea, a Greek term meaning a bit of wood, a stick. In a no less expressive fashion, the Provencal peasant calls it lou portofais, lou porto-caneu. This is the little grub that carries through the still waters a faggot of tiny fragments fallen from the reeds.
Its sheath, a travelling house, is a composite and barbaric piece of work, a megalithic pile wherein art, retires in favor of amorphous strength. The materials are many and sundry, so much so that we might imagine that we had the work of dissimilar builders before our eyes, if frequent transitions did not tell us the contrary.
With the young ones, the novices, it starts with a sort of deep basket in rustic wicker-work. The twigs employed present nearly always the same characteristics and are none other than bits of small, stiff roots, long steeped and peeled under water. The grub that has made a find of these fibers saws them with its mandibles and cuts them into little straight sticks, which it fixes one by one to the edge of its basket, always crosswise, perpendicular to the axis of the work.
Picture a circle surrounded by a bristling mass of tangents, or rather a polygon with its sides extended in all directions. On this assemblage of straight lines we place repeated layers of others, without troubling about similarity of position, thus obtaining a sort of ragged fascine, whose sticks project on every side. Such is the bastion of the child grub, an excellent system of defense, with its continuous pile of spikes, but difficult to steer through the tangle of aquatic plants.