No. 2.] FRESH-WATER PROTOZOA. 47 



Nassula Ehrbg. 



Ovate to cylindrical ; rounded posteriorly. Mouth 

 ventral, about one-third of the way from the anterior end. 

 On the left side, at the top of the mouth, is a depression. 

 From the mouth, extending forward to the left, is a zone 

 of stronger cilia. Pharynx armed with rods straight or 

 curved. Anus terminal. The animals usually contain 

 yellowish, brownish or violet drops, which are derived 

 from the Oscillaria which serve as their food. 

 N. ornata Ehrbg., Fig. 169. Fig. 170 shows the animal in 



the art of feeding upon a long filiamentous alga. 

 N. sp. ( ?), Fig. 164. A much smaller type with more evi- 

 dent trichocysts. 

 Ophryoglena Ehrbg. 



Ellipsoidal, with the posterior end somewhat acute. 

 Ciliation and striation regular. Mouth a third of the dis- 

 tance behind the anterior end, commonly closed, a cres- 

 cent-shaped or spiral slit, surrounded by a lip and lead- 

 ing into a short pharynx. Upon the left of the mouth 

 is a black homogeneous watch glass-shaped body. One 

 or more contractile vacuoles with well developed vessels. 

 Nucleus single, ellipsoidal or ribbon-shaped, and a spindle- 

 shaped secondary nucleus. 

 Op. sp. (?), Fig. 221. The placing of this animal in this 

 genus is tentative. 

 Frontonia Ehrbg. 



Ellipsoidal to elongated, somewhat acute behind. 

 Mouth not far from the anterior end, surrounded by ele- 

 vated ridges which extend backward and gradually vanish. 

 Pharynx short, with rods and two undulating membranes, 

 the left one serving as a grasping organ. Ciliation and 

 striation regular. Nucleus ellipsoidal. One or more sec- 

 ondary nuclei and usually one contractile vacuole." Trich- 

 ocysts present except in the groove extending from the 

 mouth. 

 Fr. sp. (?), Fig. 185. This is the largest holotrichous in- 

 fusorian I have seen, reaching a length of 400-500 /a. It 

 is found somewhat abundantly in New Haven and Mid- 

 dletown. 



