62 THE ROTIFERA. 



reaches the level of the knobbed ends of the ciliary wreath (cw). Here this left branch 

 joins an offshoot of the right branch ; the point of junction being marked by a third 

 vibratile tag (vt 3 ). A fourth vibratile tag (vt 4 ) is attached to the right branch just where 

 it gives off the connecting offshoot, and a fifth (vt$) can be seen on the highest dorsal 

 portion of the lateral canal. Fig. 2 shows the same right and left canals, as seen from 

 the dorsal surface, with the same vibratile tags on either side. Each lateral canal winds 

 down the side of the trunk and ends at last on the surface of the contractile vesicle. 

 Leydig (loc. cit.) records his having distinctly seen this junction in young specimens, as 

 well as a duct leading from the contractile vesicle into the cloaca (cl). 



The Nervous System. What is probably the nervous ganglion is a peculiar organ 

 (figs. 2, 4, 5, gn) consisting of large clear cells, lying at the back of the vestibule 

 near the dorsal surface. Above it, and well under the dorsal surface, is a three-lobed, 

 granular, semiopaque body (figs. 2, 5, x) with which the nervous ganglion is possibly 

 connected. The nervous ganglion in many of the Rotifera, especially among the 

 Notommatadce, shows a marked cellular structure at the lower end which loses itself 

 in a granular, semiopaque upper portion ; but it must be admitted that if these peculiar 

 bodies (gn, x) constitute the nervous ganglion of Stephanoceros, it is rather their posi- 

 tion than their shape and structure that would lead us thus to interpret them. From 

 the spot where it adheres to the wall of the vestibule, a sort of protrusile tongue or 

 taster (fig. 4, tr) rises which can be pushed forward so as nearly to fill up the interval 

 between the knobbed ciliated ends of the ciliary wreath. This tongue may be seen 

 incessantly pressing backwards and forwards as the food passes into the vestibule, as 

 if discriminating between the passing atoms, just as the two tasters do in M. ring ens. 1 

 The eyes (fig. 2 e) lie on either side of the nervous ganglion ; they may be seen by dark- 

 field illumination, but as they are small, rather deep down under the surface, and often 

 obscured by other parts, it is not easy to get both into view at once. Mr. Cubitt 

 (loc. cit.} describes and figures them as clear globes resting on pigment spots, and 

 with nerve threads attaching them to the nervous ganglion : this is a very probable 

 structure, but I have failed to make it out. Two very short lateral antennae (Figs. 2, 

 5, a) can be seen when Stcplmnoccros is viewed dorsally : they are mere setigerous 

 pimples. 



The development of the young is shown in Mr. Gosse's figures (PL IV. figs. 8 to 15), 

 in which fig. 8 represents young Stephanoceros a few minutes after birth ; figs. 9 and 10, 

 a little later ; and figs. 11 to 14 represent successive stages of growth of a specimen 

 from three to eighteen hours old. Fig. 15 shows the perfectly developed young Steplia- 

 noceros, thirty-six hours old ; it exhibits the bands of seta?, the principal viscera, the 

 muscular collars, vestibule, crop, and jaws. Mr. Rosseter (loc. cit.) says that on one 

 occasion he watched the development of a young Stephanoceros and noticed that the 

 lobes of the corona " originate as buds and unroll like the fronds of ferns " (figs. 16, 17). 

 These buds began to appear about eleven hours after the animal was hatched, and when 

 they had risen to a small height gradually unfolded ; they remained in a drooping state 

 for two days, but on the third day took the arched form usual in the adult. Dr. 

 Mantell observed a young specimen in which the lobes even after eighty hours from 

 birth were mere rudimentary buds. Such discrepancies in the rate of development 

 noticed by these three observers are common in all the Rotifera, and are doubtless 

 partly due to the various degrees of development that the embryo attains in the ovum 

 before its extrusion. In Stephanoceros (as in a few other Rotifera) the young (as 

 Ehrenberg conjectured) is occasionally born alive. This has been seen by Mr. Rosseter 

 and Dr. English, 2 and indeed is almost shown in Dr. Leydig's figure (PL IV. fig. 7), 

 where the much advanced embryo (y~] lying close to the oviduct (ot) already exhibits the 

 eyes and frontal cilia. 



1 (PI. V. fig. 2 c, tr). - Sec Mr. Rosscter'y paper (loc. cit. p. 171). 



