No. 2.] FRESH-WATER PROTOZOA. 45 



Prorodon Ehrbg. 



Ellipsoidal to ovate, with rounded ends, and occasion- 

 ally somewhat flattened. The terminal mouth leads into 

 a short or a long pharynx which is covered with a rod- 

 like or a smooth membrane. Anus terminal ; one or more 

 contractile vacuoles ; nucleus ovate to ribbon-like. Lon- 

 gitudinal striations; uniform ciliation, except that fre- 

 quently there is a tuft of longer posterior cilia. 



Pr. niveus Ehrbg., Fig. 136. 



Pr. armatus C. & L., Figs. 137 and 137a. 



Pr. griseus C. & L., Fig. 144. 



The genus Prorodon presents wide variations in shape 

 and size. Figs. 136 and 137 represent two extreme types 

 that I have associated with specific names as above shown. 

 Many intermediate forms between these are found. 

 Trachelophyllum CI. & L. 



Body much flattened, appearing flask-shaped upon the 

 broad side, with an elongated neck-like anterior end. A 

 small retractile proboscis in front, upon which is the 

 rnouth leading into a pharynx extending through the 

 neck. Ciliation uniform, with longer cilia around the 

 mouth. Contractile vacuole terminal and many nuclei. 



Fig. 156 represents a very large infusorian that does 

 not seem to agree exactly with any described genus. It 

 differs from Trachelophyllum in not showing the proboscis, 

 and in having the vacuole divided into many parts. For 

 similar reasons it cannot be placed with Lacrymaria, while 

 the other flattened infusorian, Trachelocera, is described as 

 being only marine. I therefore place it provisionally with 

 this genus. 

 Lacrymaria Ehrbg. 



Form flask-shaped but changeable ; with a short or a 

 long, highly contractile neck, and a rounded posterior end ; 

 not flattened; with a plug-like projection carrying the 

 mouth, which is surrounded with a crown of long cilia. 

 Pharynx, a long or short tube frequently longitudinally 

 striped. Body striped longitudinally or spirally ; anus 

 terminal or sub-terminal. 



L. olor Miill., Fig. 149. Fig 149a is the same animal with 

 its neck contracted. 



