THE INFUSORIA 



177 



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ura 





Structure and activities of paramoecium. 



A, spiral path of paramoecium. h, paramoecium at rest, showing cilia motionless 

 against a cotton fiber. C, paramoecium at rest against a mass of bacteria (o) showing cur- 

 rents produced by the cilia. D, P. calkinsi, external contours and buccal groove. E. 

 P. calkinsi, internal structure. F, P. caudatum, section perpendicular to surface. G, sur- 

 face of pelhcle showing cilia and trichocysts. H, section through cytostome and gullet, 

 /, trichocysts before (left) and after (right) discharge. 



c, cilia with basal granules; cu, contractile vacuole; ec, ectoplasm; en, endoplasm; 

 fv, food vacuole; ma, macronucleus; mi, micronucleus; n, nucleus; t, trichocysts which 

 form in endoplasm and migrate to ectoplasm; um, undulating membrane. {A, B, and C 

 from Jennings, "Behavior of the Lower Organisms," reprinted by permission of Columbia 

 University Press; D and E, after Woodruff; F to H, after Maier; I, after Khainsky.) 



