EDMONDSON — PROTOZOA OF IOWA. 73 



Chilodon aicullulus is one of the common forms of stagnant 

 water and may also frequently be found in fresh water among 

 algae. 



Embryos of this species differ from the adult in several par- 

 ticulars. The body is greatly inflated and the inner end of the 

 pharynx is usually spirally twisted, while the nucleus is small, 

 round, and in the posterior extremity of the body. As age 

 advances the nucleus becomes larger, more oval in outline, and 

 occupies a position close to the inner end of the pharynx. 



The common method of reproduction is by transverse division. 

 Conjugation may often be observed. The organism feeds upon 

 algae, diatoms, etc., the endoplasm frequently being packed with 

 plants of low order. 



Chilodon caudatus Stokes. 



Body elongate-ovate, wider anteriorly, the left-hand anterior 

 extremity produced into a prominent lip-like extension. The 

 posterior extremity of the flattened ventral surface somewhat 

 acutely rounded, while the posterior extremity of the dorsal sur- 

 face is drawn into a short, more or less acutely pointed, tail-like 

 appendage, which is free from the corresponding ventral extrem- 

 ity. Oral aperture similar to that of Chilodon cuailliihis. 



Nucleus oval, posterior to the middle. Contractile vesicles 

 scattered. 



lycngth, 50-75 microns. (Figs. 114- 115, PI. XV.) 



This species as found in this state presents some individual 

 variations with respect to the posterior extremity. Frequentl}^ 

 one surface of the posterior extremity may be broadly rounded 

 while the other surface is acutely pointed. In other individuals 

 both dorsal and ventral surfaces may be acutely pointed. 



From a lateral point of view the posterior extremity is as repre- 

 sented in Fig. 115, PI. XV, the dorsal tail-like extension being 

 entirely free from contact with the ventral portion. 



The species has been found in pond water in a few localities 

 only in this state. 



Reproduction takes place b}' transverse fission. 



Chilodon fluviatilis Stokes. 



Body about twice as long as broad, rounded posteriorly, the 

 left-hand anterior border not produced into a prominent lip-like 



]ProC. D. a. S., Vol. XI.] 10 [May 29, 1906.I 



