336 DESCRIPTION OF [Rotatoria. 



or frontal region of the animalcule, is broad, truncated, 

 and surrounded with a wreath of cilii, interrupted at the 

 mouth, which is lateral. On the frontal plane arise four 

 thick conical papillae, often furnished with an articulated 

 bristle, especially the two anterior, as seen in. figures 365, 

 366, and 368. The oesophagus is short and narrow, its 

 head, or bulb, has jaws, with teeth, and four muscles ; it 

 lies immediately within the mouth. The stomach and 

 rectum are oval (Gasterodela). Two spherical, pancreatic, 

 or salivary glands, are observed near the oesophagus, and 

 posteriorly an ovarium, often containing a large ovum, 

 which is expelled near the base of the tail. The ovate or 

 shortly-cylindrical body terminates in a long, thin, and 

 strong cylindrical foot-like tail, the end having a suction 

 disc. The gelatinous nucleus, or lorica, is only perceptible 

 in coloured water, except when infested with green para- 

 sitical Monads ; within it the animalcules can completely 

 withdraw themselves, their tails becoming thickened and 

 bent. (In the group, figures 365 to 368, the lorica is not 

 shewn.) There are no anterior muscles, but three pair of 

 posterior ones, which disappear near the rotatory organ ; 

 there is also a back pair and two lateral pairs. Several 

 transverse vessels appear connected with two anterior, 

 lateral, longitudinal vessels, which, Dr. Ehrenberg states, 

 must arise from a vascular network near the head, as in 

 Hydatina. He has also seen two spiral bands (gills), situated 

 posteriorly. Two beautiful red visual organs lie immediately 

 beneath the wreath of cilii, and behind them little oval 

 nervous ganglia. In the foot-like tail are two large wedge- 

 shaped glands, probably male organs. These creatures 



