The front and hinder extremities differ in different species. S. mucronata has a lorica furnished with four spines in front and three behind; S. ventralis has two in front only, and its lorica is spotted. On the back of the neck of {he former will be found a feeler, armed with a bristle. The body of a full-grown Salpina is about the 100th of an inch or more long. A young one has just the reeling side-to-side motion of its parent, but has a soft lorica, which becomes hard and firm with age. Our next example is one which occurred to me in a gathering from the small Arboretum pond before mentioned. Dinocharis pocillum has the basal portion of its tail-foot freely jointed, the joints having spinous processes. There are also two spines near the origin of this organ, and a minute bristle marks where the fork begins, The lorica is rather loose, and stippled all over with open dots. The actions of the animal are queerly angular and vigorous. One of the most beautiful of the loricated Rotifera is Stephanops lamellaris, in which the body-shield undergoes a peculiar expansion on its anterior margin, so as to form a very elegant crown over the animal's head. Behind the lorica is armed with three spines, and there are three bristles at the end of the tail-foot. On each side of the head is a little horn, and the neck has a collar-like thickening, The entire length of the lorica, including spines and hood, is about the 200th of an inch. A familiar friend to the microscopist is Squamella oblonga. Its favourite occupation is to climb about the stems or roots of water-plants, feeding as it goes like a minute species of cattle. It has four crimson eye-spots, and a lorica armed in front with four small spines.
One of the most interesting of all the frees swimming Rotifera is, undoubtedly, the little creature which has given its name to the order, and is known as Rotifer vulgaris. When the wheel-like apparatus is drawn in, the shape of the animal reminds one of a spindle, the forward extremity tapering, as it were, into a blunt-pointed snout. Its movements are then much like those of a leech, The body is alternately wrinkled up telescopic-fashion, and stretched out over the ground intended to be covered. The ciliary wreath is double, and serves both for swimming and feeding, On the back, near the head, is a small feeler. There are two eyes, placed much in advance of the masticatory organ, and, apparently near the tip of the snout, in the retracted state of the ciliary wreath. I was very much puzzled, some years ago, when, having caught a full-grown female specimen, I observed a young one, about halt her length, freely disporting itself in the interior of its parent. Omitting the parent's tail-foot, about two-thirds of her body was occupied by the young one, with eyes, and champing gizzard all complete. Even the ciliary wreath of the latter played at intervals. And all this must have taken place in the maternal ovary, which had been stretched to accommodate the offspring for sometime before actual birth. In fact the common Rotifer is occasionally ove-viviparous; that is to say, the young, though produced from eggs, may be retained within the ovary for a certain time after they are hatched,
In Brachionus urceolaris the lorica is closed at the sides and open at the ends like the shell of a tortoise. Into this the animal can entirely
