The gizzard is three-lobed, and curiously grasped by forked expansions of the handles of the hammers. The tail, or tail-foot, can be withdrawn or thrust out at the will of the creature; and when in a good position for observation, a slight additional pressure will keep it so for examination. Delicate muscular longitudinal bands, forked towards the end of their course, supply the means of performing some of its motions, and one, or perhaps two, spiral threads extend through the upper half of its length, and either act as muscles, or as elastic springs for its extension. The intestines and other viscera are clearly exhibited, and a strong ciliary action conducts the food to the gizzard-mouth. To return to the tail. One spiral fibre is easily discovered; but I have often, and at an interval of months, seen the appearance of two, and am in some doubt whether this was a deception, arising from the compression employed, or was a genuine indication. [Illustration: A. Metopidia acuminata, as drawn by Mr. Gosse. B. Specimen as seen and described in text. _c._ Mouth or gizzard.] Where this Rotifer occurs I have usually found it plentiful, but unfortunately could obtain no constant supplies after I had determined to make a special study of the remarkable tail, which is much more complicated than I have described. The _Pterodina_ lived for some time in captivity, and for a week or two I could obtain them from my glass tank. They were likewise to be found for some weeks in the same part of the pond, but not all over it, until one day not a single specimen could be discovered, notwithstanding a persevering search nor was I afterwards able to get any from that pond during the remainder of the year. [Illustration: Trichodina pediculus.] Several other Rotifers, with and without carapaces, were among the same mass of confervæ, among them a _Metopidia_, with a firm shell, a forked jointed tail, and a projection in front which worked like a pickaxe among the decaying weed. There were likewise specimens of the long-necked animalcules (Trachelii), groups of Vorticella, some specimens of Volvox, and a small _Trichodina pediculus_, which, when magnified two hundred and sixty linear, was about the size of a sixpence and equally round. The edge was beautifully fringed with a circle of cilia; in an inner circle was a row of locomotive organs, and the centre exhibited vacuoles constantly opening and shutting. This creature, as before explained, is often found as a parasite upon the polyps. On one occasion a glimpse was caught of a Rotifer similar in shape to the common wheel animalcule, but with a yellow inside. Possibly it was the object so beautifully delineated by Mr. Gosse, in his "Tenby," and described as the "Yellow Philodine," but this must remain in doubt, as it managed to escape before it could be secured. [Illustration: A. Cothurnia imberbis--('Micrograph. Dict.') B and C. The specimens described in text. The figures give the _linear_ magnification.]