better.] "The cuirass composed of one or two pieces often furnished with salient points, or appendages, either fixed or moveable, and which do not change their shape when contracted. The mouth, furnished with jaws, and preceded by a vestibule, the ciliated walls of which are more or less prolonged into lobes garnished with vibratile cilia presenting the aspect of toothed wheels in motion. Some tailless, others having simple or bifurcate tails."

We have to notice in this section the great variety of shape from the common Brachion, or pitcher rotifer, which may be roughly compared to a turtle in form, and which is furnished with a powerful tail, that it lashes about like a cat, to the elongated skeleton-like Dinocharis, or to Triarthra and Polyarthra, with their remarkable appendages. In the greater part of this group the cilia which give rise to the rotatory appearances are the chief instruments of locomotion ; but those furnished with limblike appendages use them as locomotive organs in addition to the cilia. Salpina is like a prismatic glass box; Pterodina like a soup-plate, with a head and tail projecting at opposite sides; and some of the others are very singular in aspect.

We are now engaged merely in getting a general idea of the whole group of rotifers, and pass from the Cuirassiers to the Furcularians, who constitute a distinct family of Dujardin's swimmers. He describes them as "animals with an ovoid or cylindrical body, very contractile and variable in form, covered with a flexible membranous tegument capable of making folds in regular longitudinal and horizontal lines, with a tail more or less long, and furnished with two fingers or styles." This family contains, amongst others, the Notommata aurita, or "eared" Notommata, so well described by Mr. Gosse, in the "Transactions of the Microscopical Society" (May, 1850), and which shows the water-vascular system and the muscular system in a very striking way. The term "tail" must not always be strictly understood, when speaking of rotifers. the case of the Notommata, for example, Mr. Gosse points out that the so-called tail is a retractile foot with two pointed toes. The chief conditions of belonging to Dujardin's Furcularian family are, being swimmers, not having a rigid carapace, and not being able to crawl as well as swim. The lowest form of this family is almost worm-like (Lindia torulosa). Dujardin concludes his second order with the Albertian family, comprehending the still more worm-like Albertia, in which the ciliary apparatus is feebly developed, and which is a parasite in the intestines of earth-worms and snails.

In

Dujardin's third order and sixth family include the swimmers and crawlers, and comprehend the common rotifer and other species which strongly resembles it. He describes