• EDMONDSON — PROTOZOA OF IOWA. 47 



Petaloino7ias mediocanellata is to be found frequently in fresh 

 water among aquatic plants. Its movement is smooth and glid- 

 ing, the tip of the long flagellum being vibratile. Due to the 

 groove in the median line of the body food particles are con- 

 ducted to the posterior region where digestion takes place. It is 

 in this region that the spherical nucleus is to be found. The 

 contractile vesicle is lateral to the oral groove in the anterior 

 region, which is comparatively free from granular particles. 



ANISONEMA Dujardin. 



Body ovate, flattened, persistent in form. Oral aperture lead- 

 ing into a long pharynx. Flagella two in number, the vibratile 

 one arising from the ventral border, and directed forward, the 

 posterior one long, arising posterior to the vibratile one and curv- 

 ing backward in a trailing manner. Contractile vesicle or vesi- 

 cles anterior, nucleus posterior. 



Anisonema acinus Duj. 



Body with ventral surface flattened, wider posteriorly, the 

 anterior flagellum short, vibratile, the posterior one with a thick- 

 ened base, long, trailing. Oral opening near the base of the 

 anterior flagellum. Endoplasm transparent, contractile vesicle 

 and nucleus conspicuous. 



Length, 25 microns. (Fig. 78, PI. XI.) 



This species of the genus is widely distributed, being found 

 nearly everywhere in pond water, among diatoms and other 

 aquatic plants. Its movement is usually forward in a straight 

 line, the trailing flagellum serving as a rudder directing the 

 course. Reproduction takes place by longitudinal division. 



Anisonema ludibundum S. K. 



Body nearly oval, narrower at the anterior extremity. Fla- 

 gella two in number, about twice the length of the body, inserted 

 at some distance from the anterior end. Contractile vesicles 

 often more than one. 



Length, lo microns. (Fig. 79, PI. XI.) 



This smallest species of the genus has come under my observa- 

 tion but a few times. By means of the posterior flagellum the 

 organism may temporarily attach itself. Progress is made by 

 short oscillating movements. 



