At length, about an hour and a half after the first appearance of the constriction, the new animal threw out its clear neck to a great length, writhing it about with rapid agility, and forming the most elegant curves, like those of a serpent, often completely encircling its own body with it. It still remained, however, in contact with its parent, which after a time also protruded its neck in the same manner. Both then retracted and remained still for a while; and again, almost simultaneously threw out their long necks and then retired to sluggish repose.

Among the sediment, the grains of which are driven hither and thither by their spasmodic, jerking movements, you see several individuals of another sort of creature,— the Chrysalis Animalcule (Paramcecium aurelia). This is a "Triton among minnows"; for it is greatly larger than any of those we have yet observed, and is just visible to the naked eye, when we hold up the live-box obliquely against the light ; for then the animals appear as the smallest possible white specks.

Bringing them again under the microscope, each presents a pellucid appearance, and an oblong figure, of which the fore part is somewhat narrowed. The back rises in a rounded elevation, and the mouth is situated as far back as the middle of the body upon the under surface, where its position is marked by a sort of long fold, the sides of which are fringed with long cilia, whose vibrations are very marked. The whole surface, on both sides, is covered with minute cilia, arranged in longitudinal rows, of which, according to the great Prussian professor, there are from thirty to sixty on each surface, each row bearing sixty or seventy cilia. This must be considered as an approximation ; for we may well doubt the accuracy of the counting, when the objects are so very evanescent as these vibrating cilia.

The vacuoles, and the temporary stomachs, more or less completely tilled with the brown and green food, which the animals are collecting from the decayed vegetable matters, are sufficiently numerous and conspicuous ; but they may be rendered still more so by the device of mixing a little carmine with the water. The ciliary currents are thus instantaneously rendered strikingly visible. The crimson atoms are attracted from all quarters towards the tail of the animal, whence they are urged in a rapid stream along one side towards the head, around which they are hurled, and then down the other side to the tail, pouring off in a dense cloud in a direction contrary to that in which they originally approached.

But now the gathered currents have produced their expected result ; for many of the globular vacuoles are already become of a beautiful rosy hue, from the minute particles of the pigment which have been whirled to the mouth, and swallowed.

The feature of greatest interest, however, in this animal is the contractile bladder. Two of these organs are usually seen co-existent in each individual, placed, the one on the front, the other in the rear of the mouth, but near the opposite,—i.e., the dorsal,—surface of the body; for as the creature slowly revolves on its longitudinal axis, the line of the vesicles alternately approaches and recedes from that of the mouth. They are remarkable for their structure. Far from the simplicity in which the organ is usually presented to us in the animals of this class, the contractile bladders are here very complex. Each when distended is globular; and it is surrounded by a number of others of much smaller dimensions, and of a drop-like form, so set as to radiate around the principal vesicle as a centre, the rounded portion of each in apparent contact with the vesicle, and the slender extremity running off as an attenuated point till lost to sight in the sarcode. The main vesicles alternately become distended, and suddenly contract to a point ; while the radiating cells are continually varying in size, though in a less degree. It is customary to describe the secondary vesicles as coming into view at the instant of the contraction of the primary

PARAMECIUM.

one, and to suppose that the emptying of the one is the filling of the other, but I have not been able to observe this mutual relation satisfactorily made out. The smaller as well as the larger vesicles are conspicuous from their colourless transparency ; for the general sarcode of the body, though pellucid, is only so in the same degree as glass, slightly smoked; besides that its clearness is often impaired by crowds of granules and minute globules.

You ask what is that comparatively large oval body attached by its side to one of the leaves of the plant. It is the egg of some considerable Rotifer, probably JSuchlanis, which is always glued to some filament or stem of a waterplant. It may interest you to watch the progress of the contained embryo, which you can readily do, since the eggshell is as transparent as glass, and the infant animal already displays the movements of independent life.

Meanwhile I will tell you the tragical and lamentable history of just such an embryo as this, that, was eaten up before it was born, under my own eye. One of the depredators was a very amusing animalcule, which is sufficiently scarce to make its occurrence a thing of interest, especially to a young microscopist, as I was at the time.

A large egg of (as I believe) Eucltlanis dilatata had been laid during the night on a leaf of Nitella, in the live-box. When I observed it, the transparency of the shell allowed the inclosed animal to be seen with its viscera, which occasionally contracted and expanded ; the place of the mastax I could distinctly make out. The cilia were vibrating, not very rapidly, but constantly, on COLEPS AND CHIL01IONAS. the front, where there was a vacant space between the animal and the shell. From seven a.m. when I first saw it, I watched it for about eight hours, without perceiving any change ; but at that hour having withdrawn for a short time, I perceived on my return that a portion of the animal was outside the shell. The appearance was that of a small colourless bladder oozing out at an imperceptible aperture ; and this oval vesicle quickly but gradually increased, until it was half as large as the egg itself. A little earlier than this point, the cilia were seen on the front or lower side of the excluded portion, and these began to wave languidly in a hooked form. They thus seemed much longer and more substantial than when rotating in the perfect animal. When excluded to the extent just named, some little creatures that were flitting about found it, and began to assemble round it. These were far too rapid in their

movements to allow me to identify them before, or to perceive anything else than their swift motion and oval form ; but this attraction, causing them to become still, allowed me to perceive their singular and beautiful structure. Each consists of an oval vase open at the top, the margin of which is cut into a number of little points; the sides are marked by a series of ribs, which run down longitudinally, and are crossed by other transverse ones ; the rounded bottom is furnished with three short points, so that the whole reminded me of a barrel with its staves and hoops, set on a three-legged stool. Within the body, which is colourless, are seen small dark spots which are probably the stomach-vacuoles. Thus I identified these little barrels with Coleps hirtus of Ehrenberg, but I found no record of their carnivorous propensities. One after another whirled into the field, and after a few gyrations became stationary at the head of the half-born Euchlanis, just as I have seen vultures gather one by one to a carcass. Very soon there were a dozen or fifteen of them, some of which were ever shifting their places, and some were playing around, or revolving on their longitudinal axes. I found that their object really was to prey on the soft parts of the creature just excluded from the egg; for, by carefully watching one, I distinctly perceived particles of the flesh fly off, as it were, and* disappear in the body of the Coleps. The appearance was that of steel filings drawn to a magnet, for the mouth of the Coleps was not in actual contact with the flesh; and therefore, I suppose, the surface having been in some way ruptured (which I could see it was), the loose gelatinous atoms were sucked off by a strong ciliary current. They did not attack any other part, and after having continued their murderous occupation about ten minutes, they one by one departed. The ciliary motion of the Euchlanis ceased immediately after it was first attacked, and I suppose it was soon killed, for it did not increase in size in the least afterwards. When the Colepes left it, a great portion, perhaps a third, of the excluded parts was devoured.

As soon as the depredators were gone, or even before, others more diminutive, but more numerous, were ready to take their place. The drop of water under review had been found amazingly full of a small oval Jlonas, perfectly transparent, of an oval form, with some granules visible in the interior. They were about -joVo °^ an ^nc^ ^n length. They filled the whole field, gliding about very nimbly, but so close as but just to allow space for motion, and that in several strata. By the morning these were collected in masses, which to the naked eye looked like little undefined white clouds, but which under the microscope showed the Monads in incalculable multitudes, but for the most part in still repose. Some were seen moving to and fro, however, and, in the course of the day, most of them became again active. As soon as the Colepes had forsaken their prey, the Monads began to gather round it, cleaving to the same parts, and apparently imbibing the juices, for the extruded parts still slowly decreased, until at length these were reduced to about one-third of their original dimensions.

A close examination of these latter when they had settled to rest showed me that they were of the species Chilomonas iKiramozcium. There is an indentation on one side of the front where the mouth is situated: here there is a ciliary action ; the projecting part, called the lip, is said to be furnished with two slender flexible proboscides, but my power was not sufficient to discern any trace of these. A sort of a ridge, or keel, runs down the length of the body, perceptible by a slight line ; numbers of stomach-cells also are perceptible. The motion of these lip-monads was not very rapid when unexcited • it is performed by a sort of lateral half-roll, the two sides alternately being turned up, like a boat broadside to a swell, and the line of progression is undulating. 2 D And now, having pretty well exhausted the contents of this live-box, let us try a dip from this other phial from another locality, equally productive, if I am not mistaken. Yes; for, to begin, the stalks of Nitella here are fringed with populous colonies of the most attractive of all the Infusoria, the beautiful Vorticellce. The species is not the common bell-shaped one, but the smaller with pursed mouth, the little V. microstoma.

Look at this active group, consisting of a dozen or so of glassy vases, shaped something like pears, or elegant

YOETICELX^:.

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