Plate II 



Fig. 3 Paramoecium caudatum, (optical section) centrifuged 5 minutes; n^ r = 13,950 X 10*. 



Fig. 4 Ibid., centrifuged J hour; n-r = 6,200 X 10*. 



Fig. 5 Ibid., same scale, centrifuged 24 hours; rfi r = 742 X lo^ 



Fig. 6 a. P. caudatum fed on hens' egg yolk and centrifuged two days, nV = 764 X 10'. 6, the 

 same one day later, c, the same one day later. 



Fig. 7 Genealogical table of descendants of a, a P. caudatum mutilated in the centrifuge (6 days, 

 nV = 764 X xcf). h = homed and n = normal individual. 



Fig. 8 a = P. caudatum from old culture, h — the same two days later. 



Fig. 9 A pair of ex-conjugants showing deformities produced by conjugation. 



Fig. 10 Series of curves showing variation in length in P. caudatum and P. aurelia. a, P. cauda- 

 tum (218 individuals) from Hinkson Creek, Columbia, Mo. b, P. caudatum (234 individuals) from a 

 pond at Columbia, Mo. c, P. caudatum (219 individuals) from Ashland, Va., on maintenance, d, P. 

 caudatum (184 individuals) from Ashland, Va., well fed 24 hours, e, P .aurelia (297 individuals) from 

 old culture at the University of Missouri. /, P. aureha (127 individuals) from a drain ditch at Columbia, 

 Mo. 



