Hydatinaea.} TH E INFUSORIA. 359 



hermaphroditism. In two species a projecting respiratory 

 tube at the frontal region indicates the existence of the 

 vascular system ; the red eye, upon a nervous ganglion, 

 indicates the presence of a system of sensation in all the 

 species. 



591. MONOCERCA rattus (Trichoda rattns, M.) The 

 rat Monocerca. Body ovate, oblong, truncated anteriorly, 

 and unarmed ; foot styliform, the length of the body. This 

 creature swims slowly, in a stiff manner ; when stationary, 

 it throws the styliform foot backwards and forwards. The 

 ovarium has a reddish colour; behind it lies a roundish 

 contractile vesicle. The foot has a short base, with a 

 cordate internal muscle, and four unequal bristles. Found 

 amongst conferva, &c. Length 1-1 20th. 



592. MONOCERCA bicornis. The two-horned Monocerca. 

 Body ovate, oblong, truncated in front, armed with two 

 spines ; foot styliform, a little shorter than the body ; the 

 oblique oesophagal head exhibits delicate transverse cor- 

 rugations ; it has a bent and straight jaw, with probably 

 three teeth in each. Fig. 399 represents an animalcule 

 (right side) -^ Jig. 417 another, contracted, and having its 

 rat-like tail bent. Length 1-7 2nd. 



593. MONOCERCA (?) valga ( Vorticella valga, M.) The 

 little Monocerca. Body small, almost cubical, with dis- 

 tinct head, an elevation on the back, and a conical foot, 

 unequally forked ; the rotatory organ, during contraction, 

 shews four muscular sheaths, and the distinct red eye is 

 placed upon a less distinct ganglion ; the oesophagal head 

 is not evident. Length 1 -288th. 



Genus CLIV. NOTOMMATA. The neck-eyed Rotatoria 

 have a single eye upon the neck, a bisulcated foot, resem- 



