We pass on to notice in conclusion two or three of the fixed forms, of which a beautiful example is the _Melicerta ringens_ (Plate IX. Fig. 7), whose building operations have a never-ending charm. Particles of débris are accumulated in a curious little cavity in the chin, in which they are whirled round, and mixed with a secretion which binds them together, and when a brick is made the head is bent down and the brick applied to the desired spot with mathematical regularity. By supplying fine particles of innocuous colouring matters, the Melicerta may be made to build a variegated case. The most remarkable specimen known is the one figured in Hudson and Gosse’s work, which was found by the present writer in a specimen of water from which he had already obtained five-and-twenty species of various kinds of Rotifer; the water was collected by an inexperienced person, and there was only a pint of it. It had, moreover, been kept for three weeks, and the moral of that is, to preserve one’s gatherings, and keep an aquarium into which they may be poured when done with for the moment. New forms will often develop with startling rapidity, their eggs having been present in the original gathering. The young form of Melicerta, shown in Plate XIV. Fig. 20, is strangely unlike its mother, and much more nearly resembles its father. Another group of extreme beauty is the Flosculariæ (Fig. 19), several species of which are very common. They will be easily known by their appearance, which resembles a shaving brush when closed; whilst, when opening, the shaving brush resembles a cloud of delicate shimmering threads, which at last stand out straight, radiating all round the head of the creature, and forming the trap by means of which it catches its prey. Finally, there is the lovely _Stephanoceros_ (not, unfortunately, very common), with its five symmetrically placed and gracefully curved arms, perhaps the most lovely of all Rotifers, with its exquisitely transparent body, sparkling with masses of green and golden brown. He who finds this has a treasure indeed, and will be encouraged to prosecute his studies in this “Fairyland of Microscopy.”