Otxytrichina.] THE INFUSORIA. 319 



two series of setae, and a large round mouth. This species 

 resembles O. pelionella, but is distinguished by the setae, 

 the two or three contractile vesicles, and sexual glands. 

 This creature is active, and runs nimbly along aquatic 

 plants in fresh and brackish water. Figure 336 is an under 

 view, 337 a side view. Size l-240th. 



539. OXYTBICHA pullaster ( Trichoda pullaster, Kerona 

 pullaster, M.) The water-hen Oxytricha. Body whitish, 

 lanceolate, ends obtuse ; ventral surface naked at the 

 middle; the head, indicated by a constriction, is hairy, like 

 the tail. The mouth is a narrow fossa. Found in water 

 vessels and infusions. Size 1 -430th. 



540. OXYTRICHA cicada (Trichoda cicada, M.) The 

 water-cricket Oxytricha. Body ovate or almost hemis- 

 pherical, back furrowed and notched, under surface flat. 

 Found upon the surface of stagnant water. Size l-1440th 

 to 1 -860th. 



541. OXYTRICHA lepus. The water-hare Oxytricha. 

 Body whitish, elliptical, smooth, flat, ciliated anteriorly, 

 and provided with setae posteriorly ; the mouth and dis- 

 charging orifices not distinct ; Ehrenberg has not seen the 

 male generative apparatus. Found in standing water. 

 Size 1-540-th to l-96th. 



Genus CXXVI. CERATIDIUM. The horned Animal- 

 cules have cilii, horns on the frontal region, but no styles 

 or uncini. But little of their organization is known, and 

 therefore the situation of the species is uncertain. It 

 requires a power not less than 350 to exhibit it. 



542. CERATIDIUM cuneatum. The wedge-shaped Cera- 

 tidium. Body triangular, front truncated, as also the two 

 horns, upper side smooth. Ehrenberg found this whitish 



