Chapter 6 MAY.

Floscularia cornuta-Euchlanis triquetra-Melicerta ringens-its powers as brickmaker, architect, and mason-Mode of viewing the Melicerta-Use of glass-cell-Habits of Melicerta-Curious Attitudes-Leave their tubes at death-Carchesium-Epistylis-Their elegant tree forms-A Parasitic Epistylis like the "Old Man of the Sea"-Halteria and its Leaps-Aspidisca Lynceus.

AY, the first of summer months, and of old famous for floral games, which found their latest patrons in the chimney-sweeps of London, is a good time for the microscopist among the ponds, for the increase of warmth and heat favours both animal and vegetable life, and so we found as we carried home some tops of myriophyllum, and soon discovered a colony of tubicolor rotifers among the tiny branches. They proved to be Floscules, generally resembling the F. ornata, described in a previous page, but having a long slender proboscis hanging like a loose ringlet down one side. The cilia or hairs were not so long as in the Beautiful Floscules we had before obtained, nor was their manner of opening so elegant; but they were, nevertheless, objects of great interest, and were probably specimens of the Floscularia cornuta. A swimming rotifer in a carapace somewhat fiddle-shaped, with one eye in its forehead, and a two-pronged tail sticking out behind (the Euchlanis triquetra), also served to occupy attention; but a further search among the myriophyllum revealed more treasures of the tube-dwelling kind. These were specimens of that highly curious Rotifer, the Melicerta ringens, who, not content with dwelling, like the Floscules, in a gelatinous bottle, is at once brickmaker, mason, and architect, and fabricates as pretty a tower as it is easy to conceive. The creature itself stands upon a retractile foot-stalk, and thrusts out above its battlements a large head, with four leaf-like expansions surrounded by cilia. Between the lower lobes, or leaves, the gizzard is seen grinding away, and above it is an organ, not always displayed, and of which Mr. Gosse was fortunate enough to discover the use. This eminent naturalist likens it to the circular ventilator sometimes inserted in windows, and he found it was the machine for making the yellow ornamental bricks of which the tower is composed. Pellet by pellet, or brick by brick, does the Melicerta build her house, which widens gradually from the foundation to the summit, and every layer is placed with admirable regularity.

In order to obtain the materials for her brickmaking the Melicerta must have the power of modifying the direction of the ciliary currents, so as to throw a stream of small particles into the mould, which is a muscular organ, and capable of secreting a waterproof cement, by which they are fastened together. The result is, not to produce anything like the tubes made by the caddis-worms out of grains of sand, but entirely to change the appearance of the materials employed. All large particles are rejected, and only those retained which will form a homogeneous pulp with the viscid secretion; and when the process is complete the head of the creature is bent down, and the pellet deposited in its appropriate place. Each pellet appears originally to possess a more or less conical figure, but when they are squeezed together to make a compact wall they all tend to a hexagonal form, by which they are able to touch at all points, and any holes or interstices are avoided.

According to Professor Williamson the young Melicerta commences her house by secreting "a thin hyaline cylinder," and the first row of pellets are deposited, not at the base as would be expected, but in a ring about the middle of the tube. "At first new additions are made to both extremities of the enlarging ring; but the jerking constrictions of the animal at length force the caudal end of the cylinder down upon the leaf, to which it becomes securely cemented by the same viscous secretion as causes the little spheres to cohere."

Round the margins of the lobes or expansions may be seen delicate threads towards which others radiate; these are thought by Mr. Gosse to be portions of a nervous system, and two calcars or feelers serve as organs of relation. The young Melicertas are likewise furnished with a pair of eyes, which are probably rudimentary, and disappear as they grow up.

The Melicerta tubes, being large enough to be visible to the naked eye, are easily crushed in the live-box, and to avoid this, they are conveniently viewed in a shallow glass cell, covered up as before described. By occasionally changing the water one may be kept for days in the same cell, and will reward the pains by frequently exposing its flower-like head. Usually the horns or feelers come out first, and then a lump of flesh. After this, if all seems right, the wheels appear, and make a fine whirlpool, as may be readily seen by the use of a little indigo or carmine.

The Melicerta is, however, 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. When these creatures die they leave their tubes, which are often found empty in the ponds they frequent. The Melicertas are conveniently viewed with a power of from sixty to one hundred linear, and a colony of them may be kept alive for some weeks in a glass jar or tank.

Among the remainder of my tiny captives were two beautiful members of the Vorticella family, Epistylis and Carchesium. The reader will remember that in the Vorticella previously described, the bells stood upon stalks that were very flexible, and retractile by means of a muscle running down their length. The Epistylis is, as its name imports, the dweller on a pillar. The stem is stiff, or only slightly flexible, and has no apparatus by which it can be drawn down. The specimen mentioned stood like a palm-tree, and the large oval bells drooped elegantly on all sides, as its portrait will show. At times they nodded with a rapid jerk.

Epistylis.

The Carchesium differs from the common Vorticella, by branching like a tree, but the stems are all retractile, although the trunk seldom exercises the power. A group of these creatures presents a spectacle of extraordinary beauty-it looks like a tree from fairy-land, in which every leaf has a sentient life. In general structure the bells of the Epistylis and the Carchesium resemble the common Vorticella, and like them may be seen with a power of about one hundred linear for general effect, and with a higher one for the examination of special points. Pritchard notices three species of Carchesium, and eighteen of Epistylis;[13] some of which it is to be hoped will turn out to be only varieties.

[13] An interesting Epistylis, called Digitalis, from its bells resembling fox-glove flowers in shape, occurs as a parasite upon the Cyclops quadricornis, a very common entomostracan in fresh-water ponds. At this moment I have a beautiful specimen, branching like a bushy tree, and attached to the tail of a Cyclops, who can scarcely move under his burden, which is like Sinbad's "Old Man of the Sea." (See illustration above.)

Towards the end of this month rotifers abounded, and polyps were plentiful. Among the rotifers was one about a two-hundredth of an inch long, protected by a carapace, and having a tail terminating in a single style, hence called "Monostyle." There is perhaps no class of creatures that present so many curious and unexpected forms as the rotifers; and although we have noticed a good many, there are far more that remain to be found and described.

The water in which the preceding animals dwelt was enlivened by the jumps of the Halteria, a little globe surrounded by long fine cilia, with which its movements were effected; and its companion was the Aspidisca lynceus, an oval animalcule, having a distinct cilia or lorica, and furnished, in addition to cilia, with bristles, which enable it to walk and climb as well as swim.

There were also some eggs of rotifers attached to the water plants, in which motion could be descried at intervals, and a little red eye observed. These eggs are always large in proportion to the creatures that lay them, and if they escape being devoured by enemies, may be watched until their contents step forth.

In this, as in other months, omission is made of creatures that have already come under notice, or our list would assume larger dimensions.

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