EDMONDSON — PROTOZOA OF IOWA. 63 



Although not common, Prorodon edentatus may be found in 

 pond water and stagnant infusions. 

 Reproduction is by transverse fission. 



TRACHELOPHYLLUM C. & Iv. 



Elongate, flask-shaped, flattened. Anterior region narrow, 

 neck-like, terminating in a minute conical process which is punc- 

 tured by the oral aperture. 



The pharynx may be traced backwards through the neck-like 

 region. Nuclei usually more than one. Contractile vesicle pos- 

 terior. 



Trachelophyllum tachyblastum Stokes. 



Body elongated, flexible, somewhat clavate when fully ex- 

 tended, flask-shaped when contracted. Oral aperture followed 

 by an indistinct pharyngeal passage. Cilia clothing the entire 

 surface and vibrating in an independent manner. Nuclei two in 

 number, spherical, not connected. Contractile vesicle in the pos- 

 terior region. 



Length, 175 microns. (Fig. 95, PI. XII.) 



This species is not uncommonly found in this state although it 

 has not so far been observed to be widely distributed. Found at 

 the bottom of old infusions of pond water, where it glides along 

 evenly and at a rapid rate. Another form, differing from the 

 above apparently chiefly in size, has been found in pond water in 

 Johnson county. Some individuals have exceeded 300 microns in 

 length. It may be identical with Trachelophyllum vestitiim Stokes, 

 but the external granular covering has not been apparent in the 

 Iowa species. 



DIDINIUM Stein. 



Usually ovate, cylindrical, rounded posteriorly, produced ante- 

 riorly into a short conical proboscis, and bearing a posterior and 

 anterior circle of cilia. Oral aperture puncturing the extremity 

 of the proboscis. 



DiDINIUM NASUTUM MiiU. 



Body oval, broadly rounded posteriorly. Anterior conical pro- 

 boscis longitudinally striate. One wreath of cilia near the base 

 of the proboscis, the other posterior to the middle of the body. 



