HOLOTRICHA 



759 



Genus Disematostoma Lauterborn. Somewhat similar to Fron- 

 tonia; pyriform; with broadly rounded, truncate or concave anterior 

 end and bluntly pointed narrow posterior end; preoral canal wide; 

 a dorsal ridge in posterior region of body; macro nucleus sausage- 

 form; a micro nucleus; contractile vacuole in middle of body, with 

 long collecting canals; in fresh water. 





Fig. 323. a-c, Frontonia leucas (Bullington) (a, aboral view showing a 

 contractile vacuole, collecting canals, macronucleus, four micronuclei and 

 trichocysts, X220; b, oral view, showing the cytostome with undulating 

 membrane and groove, X165; c, portion of pellicle with wart-like projec- 

 tions over trichocysts); d, F. branchiostomae, X490 (Codreanu); e, Disem- 

 atostoma butschlii, X340 (Kahl); f, Lembadion bullinum, X170 (Kahl); g, 

 Tetrahymena pyriformis, X950 (Furgason). 



