Although not exactly fruit, it is, no doubt, the means by which the Vorticellæ are propagated, for it is known that many fixed zoophytes, and even some plants, produce free swimming germs or spores, which afterwards become fixed, and grow up into forms like those which produced them. In some of the branching zoophytes (Coryne, Sertularia, &c.), the germs are exactly like little medusae, being small, gelatinous cups fringed with tentacula, by means of which they twitch themselves along with surprising agility. In this Vorticella, however, it is more like one of the ciliated Infusoria. The first one that I saw attached I conceived to be a remarkably large bell, with its mouth directed towards me, but the cilia with which it appeared to be fringed were unusually large and distinct. The movements of these appendages being comparatively slow, it was most interesting to watch them as they successively bent inwards and rose again, like the steady swell of a tidal wave, or an eccentric movement in some piece of machinery, making a revolution about twice in a second, and in the opposite direction to the hands of a clock. Suddenly the tree contracted, when, to my surprise, I observed the bell, which not an instant before appeared attached, now floating freely in the water, its ciliary movements not being in the least interrupted. Presently, however, they became brisker, the bell turned over on its side, and, ere the tree had again expanded, darted out of view, not, however, before I had remarked that it was not a bell, but a sphere flattened on one side, and having its circular ring of cilia on the flat side, with only a slight depression in the middle of it. There also appeared to be a small granular nucleus immediately above this depression, the rest of the body being perfectly transparent. I afterwards saw several others attached to the tree, each seated about the centre of a branch; but none of these were so fully developed. They were like little transparent button mushrooms, and had all more or less of a nucleus on the side by which they were attached. On only one of these did I detect any cilia.
Mr. Gosse, in his 'Tenby,' gives a picture of an animal exceedingly like what I have described; but from his account of it, there seems to be some doubt of their identity. He calls it 'Zoothamnium spirale,' because the insertions of the branches were placed spirally around the main stem, like those of a fir-tree. In my specimens the branches were set alternately on opposite sides of the main trunk, and the whole was curved like a drooping fern leaf or an ostrich feather, the bells being mostly set on the convex side.
In conclusion, let me mention that it is an error to suppose, as many persons do, that putrid water alone contains life. Infusoria occur, as before hinted, in the clear waters of the ocean, in the water that we drink daily, and also in the limpid burn that flows through our valleys, or trickles like a silver thread down the mountain side.[1]
'Where the pool
Stands mantled o'er with green, invisible,
Amid the floating verdure millions stray.
Each liquid too, whether it pierces, soothes,
Inflames, refreshes, or exalts the taste,
With various forms abounds. Nor is the stream
Of purest crystal, nor the lucid air,
Though one transparent vacancy it seems,
Void of their unseen people. These, concealed
By the kind art of forming Heaven, escape
The grosser eye of man.'
Let it be remembered, too, that Infusoria, when found in either do not themselves constitute the impurity of fresh or salt water; they merely act as 'nature's invisible scavengers,' whose duty it is to remove all nuisances that may spring up; and most unceasingly do these tiny creatures labour in the performance of their all-important mission of usefulness.