104 THE ROTIFEEA 



E. vulgaris, Schrank. 

 (PL X. fig. 2.) 



Rotifer vulgaris .... Ehrenberg, Die Infus. 1838, p. 484, Taf. Ix. fig. 4. 



„ .... Pritehard, Infusoria, 1861, p. 703, pi. xxxv. fig. 470-480. 



„ „ .... Claparede, Ann. Sci. Nat. Zool. 5 Ser. t. 8, 1867, p. 11, 



pi. iii. figs. 6, 7, pi. iv. fig. 1. 

 „ „ .... Cox, Mon. Micr. J. vol. xvii. 1877, p. 301. 



„ „ .... Eckstein, Sieb. u. Koll. Zeits. Bd. xxxix. 1883, p. 355, 



Taf. xxiii. figs. 6-12. 

 „ „ .... Zacharias, Ann. Nat. Hist. Ser. 5, vol. xv. 1885, p. 125, 



pi. v. figs. 1-8. 



SP. CH. Body white, smooth, gradually tapering to the foot ; spurs and dorsal an- 

 tenna of moderate length; eyes round, small ; teeth two. 1 



The nutritive system of this very common species differs in no way from that of 

 Philodina. The walls of the stomach are thick and absorbent, and become tinged at 

 once after the reception of coloured food. The foot gland and nucleated gastric glands 

 are obvious, and the latter, according to Dr. O. Zacharias (loc. cit.), are three-lobed on the 

 ventral surface, but confluent on the dorsal. The same observer gives the following account 

 of the vascular system. The contractile vesicle opens into the dorsally placed cloaca, and 

 a lateral canal with five vibratile tags can be traced, on each side, down to it from the head. 

 '' Each tag has the form of a cylindrical beaker seated by its tapering extremity on the 

 excretory vessel. The beaker is open above, and a broad cilium inserted at its bottom 

 projects a little beyond the aperture. . . Under a power of 1,500 diameters the oscillation 

 of the cilia was so violent that the beakers surrounding them were kept in constant 

 tremulous movement." Of the nervous system Dr. Zacharias says : " When examined 

 from the dorsal surface, the anterior portion of the body shows a triangular ganglion 

 placed immediately in front of the mastax. . . The anterior angle of the triangle emits two 

 hardly visible branches towards the eye-spots." Dr. Zacharias thinks that nerve-threads 

 also pass to the extremity of the frontal column and to the antenna ; the former of whicb 

 bears two long tactile seta} as well as a circlet of small cilia, and the latter a tuft of 

 seta?. 



In the same interesting paper, from which I have so freely quoted, there is an 

 account of an oval parasite, Tryjjanococcus rotiferorum, which Prof, von Stein dis- 

 covered, and which Dr. 0. Zacharias was at first inclined to consider as a peculiar kind 

 of ovum produced by germination from the inner surface of the cuticle. These parasites 

 were attached to the body- wall at either end of the Rotifer, Each was an oval hyaline 

 vesicle, at the free pole of which was a globular finely granulated structure capable of 

 amoeboid movements. Where the parasite was attached was a small aperture in the 

 body-wall ; and near this, inside the parasite, a clear ciliated cavity. From this cavity 

 an oesophagus is said by Prof, von Stein to go to the opening in the Rotifer's body-wall. 

 Dr. 0. Zacharias does not seem entirely satisfied that these egg-like structures were 

 specimens of Trypanococcus rotiferorum, but as he found them in abundance it is to be 

 hoped that before long the matter will be cleared up. 



The male of R. vulgaris, as of every other species, is unknown. 



Length. When extended, about ^ inch. Habitat. Most widely distributed in fresh 

 water : sea-water, Tay Estuary (P.H.G.) : very common. 



1 [Since the diagnosis of all the Bdelloids inter se is somewhat indistinct at best, every distinction is 

 valuable. And it may be added to that of this familiar species (R. vulg.) that it is so strongly, closely, 

 and evenly fluted, as to resemble the Callidince ; that its length and slenderness, in proportion to its 

 thickness, are peculiar; and that in crawling it often elongates the foot to such an extent as to recall 

 (without any exact resemblance) R. m-aerurus. — P.H.G.] 



