Hydatinaea.] TH E INFUSORIA. 369 



vesicle ; the foot has two club-shaped muscles ; a central 

 ganglion exists between the rotatory clusters ; the appa- 

 rent articulations of the foot are very remarkable. 



625. SCARIDIUM longicaudum (Trichoda longicauda, 

 M.) Foot-tail twice as long as the body, toes half as long 

 as the foot ; it springs or leaps quickly, by a rapid move- 

 ment of the foot ; it does not appear to have a lorica, and 

 is remarkable from all other rotatory animalcules by the 

 length and bending in of the foot, which, as also the body, 

 is covered with a stiff skin. Behind the eye is a transverse 

 fold in the neck, where the head draws itself into the 

 body; the foot has also a transverse fold when it bends. 

 Fig. 423 represents the animalcule extended (right side) : 

 Jig. 424 is the oesophagal head, with unequal jaws, 

 &c., extended by pressure. Found amongst oscillatoria. 

 Entire length of the body 1-7 2nd ; without the foot, 

 l-216th. 



Genus CLVII. POLYARTHRA. The many-famed Ro- 

 tatoria have a single cervical eye, no foot, but are provided 

 with cirri, or pectoral fins; the rotatory organ consists of 

 four bundles of cilii, inserted in as many, muscular sheaths; 

 they sometimes appear like the double rotatory organ of a 

 Brachionus, and the form of the body resembles Anuraea ; 

 but it is, however, soft, and the rotatory organ double : 

 laterally, two longitudinal dorsal muscles are known ; the 

 frontal region has little horns, provided with bristles, and 

 upon the breast six strong styles, or beards, forming two 

 clusters, which move in a fin-like manner. The system of 

 nutrition consists of an oesophagal head, having two sin- 

 gle-toothed jaws, a short oesophagus, an alimentary canal, 

 with a stomach-like division, produced by a constriction, 



