62 THE MICROSCOPE AND ITS REVELATIONS. 



tion between them as exists in the Ophrydium ( 440) ; and the uniting 

 substance seems to be nothing else than the clear slimy secretion which 

 probably all Rotifera exude from the surface of their bodies. It is into 

 this that the eggs are extruded; and as they are hatched in it, the young 

 produced from them remain to form part of the cluster; but, as its num- 

 bers increase, the cluster breaks up into two or more, which in their turn 

 enlarge and then subdivide, so that a pond to whose bottom the ( winter 

 eggs ' of the year before have subsided, becomes alive with them in the 

 early summer of the following year. ' The Lacinularia socialis, in like 

 manner, forms transparent gelatinous-looking globular clusters, about 

 l-5th of an inch in diameter, which attach themselves to the leaves of 

 aquatic plants. 



II. The next of M. Dujardin's primary groups (ranged by him, how- 

 ever, as the third) consists of the ordinary Rotifer and its allies, which 

 pass their lives in a state of alternation between the conditions of those 

 attached by a pedicle, of those which habitually swim freely through the 

 water, and of those wh ich creep or crawl over hard surfaces. As these 

 have already been fully described, it is not requisite to dwell longer upon 

 them. 



in. The next group consists of those Eotifera which seldom or never 

 attach themselves by the foot, but habitually swim freely through the 

 water; and putting aside the peculiar aberrent form Albertia which has 

 only been found as a parasite in the intestines of Worms, it may be 

 divided into families, the Brachionians and the Furcularians. The for- 

 mer are for the most part distinguished by the short, broad, and flattened 

 form of the body (Figs. 309, 313); which is, moreover, inclosed in a sort 

 of cuirass formed by the consolidation of the external integument. This 

 cuirass is often very beautifully marked on its surface, and may be pro- 

 longed into extensions of various forms, which are sometimes of very 

 considerable length. The latter (corresponding almost exactly with the 

 Hydatinece of Prof. Ehrenberg) derived their name from the bifurcation 

 of the foot into a sort of two-bladed forceps; their bodies are ovoidal or 

 cylindrical, and are inclosed in a flexible integument, which is often seen 

 to wrinkle itself into longitudinal and transverse folds at equidistant 

 lines. To this family belongs the Hydatina senta, one of the largest of 

 the Rotifera, which was employed by Prof. Ehrenberg as the chief sub- 

 ject of his examination of the internal structure of this group; as does 

 also the Asplanchna, the curious condition of whose digestive apparatus 

 has been already noticed ( 448). 



iv. The fourth of M. Dujardin's primary orders consists of the very 

 curious tribe, first carefully investigated by M. Doyere, to which the 

 name of Tardigrada has been given, on account of the slowness of their 

 creeping movement. It seems now clear, however, that they have no 

 near relationship to the true Rotifera; corresponding to them only in 

 their minute size and simple structure. They are found in the same lo- 

 calities with the Rotifers, and, like them, can be revivified after desicca- 

 tion ( 452): but they have a vermiform body, divided transversely into 

 five segments, of which one constitutes the head, whilst each of the others 

 bears a pair of little fleshy protuberances, furnished with four curved 

 hooks, and much resembling the pro-legs of a caterpillar. The head is 

 entirely unpossessed of ciliated lobes; and the" mouth, situated at the end 

 of a sort of beak furnished with two longitudinal stylets, leads, through 



1 See Davis in " Monthly Microsc. Journ.," Vol. xvi. (1876), p. 1. 



