
Art. XXXVIII.—On Melicerta ringens and Plumatella repens
[Read before the Wellington Philosophical Society, 22nd November, 1879.]
Having recently (September, 1879) had occasion to gather a few specimens of Myriophyllum from a swamp in the Petane valley, near Napier, I came across several interesting organisms, which I propose bringing under your

notice, not only that another locality may be added to their geographical distribution, but also as objects which will well repay the trouble of collection and study.
The first is a tube-dwelling Rotifer, Melicerta ringens.
This very curious animal has been well described by Gosse.* He there describes the mode by which the tiny animal forms its tube, by drawing from the water, by means of its cilia, any particles of solid matter which might be held in suspension. These particles, he states, are deposited in the alimentary canal until there is sufficient to form a little ball, the particles of which become cemented together by some secretion of the animal. The ball is then lifted by the head of the animal and deposited in regular sequence on the rim of the tube. Having spent some time in examining a number of these organisms, I found the minute description given by Gosse to be generally correct, with the exception that the formation of the pellets was at a much slower rate than that stated by him. The tubes occur in great profusion on the finely-divided leaves of the Myriophyllum, and are easily discernible, some being 1/8 of an inch in length.
The next specimen is a very puzzling one. Probably it may be referred to Plumatella repens. It is a fine species, the polypidon of which adheres at the base, but it eventually becomes less aggregated, and ultimately free; coriaceous, of a dark brown almost black colour, irregularly branched, extending sometimes over 2 or 3 inches; branches composed apparently of tubular cells, with a cup-shaped enlargement and dilated orifices; sometimes in pairs; walls of orifice pellucid. Tentacles yellowish white. Statoblast observable in all.
The ramulus, when adherent, short, when free, elongated.
Statoblast elongated, oval; annulus variable, resembling the eggs of P. stricta, Allm., as figured by Van Beneden, or a drawing that I have of P. fruticosa, Allm.
The general habit of the Polyp agrees with the description of Allman's Plumatella repens, var. β.
I found the above growing plentifully on dead thistles in the swamp, and brought a few specimens home with me and placed them in water. The next morning I found that a number of the individuals had committed suicide by the extrusion of their eggs, which I observed were floating on the surface of the water. Some of the remaining individuals, however, unfolded their tentacles, and enabled me to ascertain that they are not so extremely sensitive to any disturbance as is usually stated in accounts of P. repens. Indeed the fact of their growing so freely in such an open situation in only a few inches of water would lead one to infer this.
[Footnote] * Trans. Micros. Soc., Vol. III., (1852) p. 58.

There are many other interesting animals living in this pond, but I must defer noticing them till another opportunity. I would, however, mention that Lepidurus (Apus) kirkii was very plentiful during August and the early part of September, but it has now disappeared, and a large reddish-brown Hydra has made its appearance and affords me much amusement in observing its curious method of increase.
