62 DAVENPORT ACADEMY OF SCIENCES. 



often with rod-like teeth. Nucleus oval or band-like. Cilia cov- 

 ering the entire body, sometimes longer on the posterior border. 



Prorodon TERES Ehr. 



Body oval, cylindrical. Oral opening terminal, provided with 

 minute, rod-like teeth. Nucleus spherical, centrally located; 

 contractile vesicle in the posterior region. 



Length, 150-200 microns. (Fig. 93, PI. XII.) 



This species has frequently been found in stagnant pond water. 

 An interesting phenomenon has come under observation with 

 reference to the division of Prorodon teres which takes place by 

 transverse fission. A large individual was discovered already in 

 the process of division, which continued until merely a narrow 

 isthmus of protoplasm connected the two portions. Suddenly 

 another constriction began to take place and in a few minutes a 

 very small individual separated from the anterior extremity of 

 the dividing organism and swam away. 



In the meantime the original constriction grew deeper and 

 deeper until but a mere thread, seemingly ready to break at any 

 moment, remained. But division was not to take place. All at 

 once there was a rush of endoplasm centrally from each extrem- 

 ity, the harrow connecting thread of protoplasm became inflated 

 and continued to broaden until the body reached its normal pro- 

 portions. 



This, apparently, is a case of defeated division. Probably the 

 small individual carried away with it the entire nucleus of the 

 anterior half, leaving only one nuclear mass for the two dividing 

 portions. 



Prorodon edentatus C. & L,. 



Body oval, cylindrical, equally rounded at both extremities. 

 Oral aperture eccentric, opening into a conical tube which reaches 

 far into the endoplasm. Cilia of the posterior border somewhat 

 longer than those of the general surface. Nucleus spherical, cen- 

 tral in position. Contractile vesicle posterior. 



Ivcngth, 125 microns. (Fig. 94, PI. XII.) 



In general appearance this species resembles Prorodon teres but 

 differs from it chiefly in the eccentricity of the mouth. 



