OF THE ICHTHYDIXA. 



661 



and Chcetonotus from amongst the Eotatoria, believing them to be Polygastric 

 Infusoria, — a conclusion with which we are strongly disposed to agree. 



Genus PTYGURA. — Eyes and hair absent ; foot simjDle, truncated, cylin- 

 drical. Body camiDanulate, oblong. Eotary organ simple, and nearly circular. 

 Numerous tooth- like bodies, adhering to the bulb of the oesophagus, two 

 glands, a small narrow oesophagus, an elongated stomach, and a subgiobular 

 rectum constitute the apparatus of nutrition. An ovarium and a contractile 

 vesicle have been observed, but no visual organs. 



This genus is comprehended in the family Melicertiens of Dujardin, along 

 with Ladmdcu'ia, Tuhicolaria, and Melicerta, and is made to include the 

 species distributed by Ehrenberg in the several genera Ptygura, (Ecistes, and 

 Conochilus ; for Dujardin states that the individuals of these three genera 

 present no further difference than is seen in the gelatinous envelope, which 

 surrounds the two last, forming in (Ecistes a distinct tube for each individual, 

 whilst it inchides the individuals of Conochilus in a common globular mass, 

 and is absent in Ptygura. The same author would name (Ecistes crystallinus 

 " Ptygura crystaUina/' and the Volvox conockila " Ptygura Volvox." 



Ptygura Melicerta. — Transparent ; 

 body cylindrical, club-shaped, tm-gid an- 

 teriorly, with two little curved horns at 

 the mouth, and a single short tube at 

 the neck (?). The tail-like foot always 

 remains transversely folded (wrinkled), 

 as seen in xxv. 354, which represents 



the imder side. When swimming, a ring- 

 like simple vibratile organ is thrust out, 

 with a lateral notch. The two jaw-like 

 parts of the oesophageal bulb have nu- 

 merous teeth, as represented at xxv. 355. 

 1-140". 



Genus DASYDYTES (Gossc). — Eyes absent; body furnished with bristle - 

 hke hairs ; tail simple, truncate. 



This genus, according to Ehrenberg's description of Ichthydina, must follow 

 after Ptygura. 



Dasydytes goniothrix. — Hairs long, 

 each hair bent with an abrupt angle ; 

 neck constricted. 1-146". Found at 

 Leamington. 



D. antenniger. — Hair short, downy; a 



pencil of long hairs at each angle of the 

 posterior extremity of the body ; head 

 furnished with two club-shaped organs 

 resembling antennge. 1-170". 



Genus ICHTHYDIUM.— Tail cleft or forked, foot-like ; no eyes or hair ; 

 currents at the mouth and along the ventral side indicate the existence of a 

 \-ibratile organ, which not only serves for swimming but likewise for creeping. 

 A long oesophagus, a thick simple conical alimentary canal, and sometimes a 

 large single o\^im, comprise our knowledge of their organization. It is pro- 

 bable that a cylinder of little wand-Uke teeth exists (see Part I. p. 380). 



ICHTHYDIUM Poclura ( CercariaPodura, 

 M.). — Straight, oblong, often slightly 

 constricted anteriorly, where it is turgid, 

 and sometimes three-lobed. It is colour- 

 less or whitish, but during repletion 

 sometimes appears yellowish ; the ven- 

 tral surface is Hat and ciliated, the dorsal 



arched and smooth. The large dark 

 ovarium has been seen by Ehrenberg. 

 It seldom swims, but mostly creeps. 

 xxv. 356 exhibits a fidl-grown animal- 

 cule (ventral side). Among Confervas 

 and OsciUatorige. 1-440" to 1-140". 



Genus CH^TONOTUS.— Dorsal surface covered with hairs ; tail forked ; 

 eyes absent. Locomotion is performed by means of a double row of ciha upon 

 the ventral surface, forming a band-like rotary organ. The nutritive organs 

 consist of a tubular mouth, probably provided with a cylinder of teeth, a long 

 thin oesophagus, and a long conical stomach (trachchgastricum), upon whose 



