ROTIFERA. 



401 



4 Rotifers without vibratile cilia, but which 

 are supplied with nails, by means of which 

 they walk. Examples : Hydatina, Notom- 

 mata, Furcularia, $c. 



Dujardin, in his work, also objects to the 

 characters on which Ehrenberg has consti- 

 tuted the various genera belonging to his 

 eight families, these genera being principally 

 determined by the presence or absence of 

 little red spots, which Ehrenberg designates 

 as eyes. (Fig. 292. a ; fig. 303. a ; fig. 296. 

 a - y jig. 294. a ; fig. 298. a ; fg. 299. b.) 



The following is a description of the families 

 adopted by Ehrenberg : 



Family 1. ICTHYDINA. Character. 

 Naked Rotifers, with a single continuous 

 rotatory organ, not lobed at the margin. 



In the genera Ptygura and G/enop/iora, the 

 rotatory organ is circular, and serves as a 

 means of locomotion. In Chcstonotus and Icthy- 

 dlum it is elongated, elliptical, band-like, and 

 seated on the ventral surface. Chcstonotus 

 and Icthydium possess a furcated foot, Pty- 

 gura and Glenophora a simple one. Icthydium 

 and Chcstonotus have a simple conical intes- 

 tine, with a long thin oesophagus without 

 teeth (?) Glenophora, a short oesophagus 

 with two teeth; Ptygura,^ constricted stomach 

 with three teeth (J^g.288.). Pancreatic glands 

 are only seen in Chcstonotus and Ptygura. 

 Caecum, gall-ducts, and male sexual organs 

 not observed. In two genera, the female 

 sexual system consists of an ovarium with a 

 few large ova. The evidence of the existence 

 of a nervous system is seen in the two large 

 red frontal eyes of Glenophora. Chaetonotus 

 has a hairy back. 



Analysis of the genera : 



ff A single foot. Ptygura. 

 Xo hair, j A furcated ; 

 "sent. L foot. 



[Hairy. 



Two 1 

 eves. J 



These genera embrace six species, some of 

 which have been known to microscopic ob- 

 servers under various names, from a very 

 early period. Icthydium podura was described 

 by Joblot, as poisson a la tete treflee, in 1718. 

 The Chcstonotus larus was described by 

 Miiller in 1776 as Trichoda acarus. 



This family embraces some of the simplest 

 forms of the Rotifera. It may perhaps be 

 doubted as to whether this class at all is the 

 place for the genus Chcstonotus. They have 

 no distinct rotatory organ, and their bodies 

 covered with cilia, place them in very close 

 alliance with some forms of the Polygastria, 

 especially the Euplota, from which they are 

 distinguished by their symmetry, and distinctly 

 furcated tail. Dujardin places Chcstonotus 

 amongst his symmetrical Infusoria, which do 

 not include the Rotifera or Systolides. 



Family 2. (EciSTiNA. Character. Ro- 

 tiferous animals, with a single rotatory organ 

 entire at the margin, enclosed in a shield. 



The organs of motion consist of internal 

 muscles and an entire foot or tail. The or- 

 gans of nutrition are an apparatus with rows 



VOL. IV. 



Fig, 288. 



Icthydium. 

 Chcetonotus. 

 Glenopfiora. 



Ptygura melicerta. (After Ehrenberg.") 

 1, partially expanded ; 2, completely expanded, 

 the cilia in action causing currents indicated by the 

 arrows ; 3, contracted. 

 a, a, a, contractile vesicle ; b, situation of the anal 



orifice. 



of teeth for chewing (Jig. 289. , ), two pan- 

 creatic glands. Ova and ovaria have been 

 Fig. 289. 



Conochilus volvox. (After Ehrenberg.) 

 a, a, jaws and teeth ; b, b, papillae ; c, c, c, c, glands ; 



d, d, ovarium. 



observed in the two forms of which the family 

 consists. Vessels, two filiform tremulous or- 

 gans (called by Ehrenberg "gills"); nervous 



D D 



