628 Lorande Loss Woodruff. 



of high reproductive activity and progressively increasing in size 

 as "degeneration" advances. In the last couple of generations 

 before death ensues the size is secondarily reduced by a shrinking 

 of the cytoplasm. 



11. A disappearance of one of the micronuclei occurred at 

 certain periods of high reproductive activity. 



12. These cultures strongly suggest that it is customary to 

 regard the structure most frequently observed in "wild" Infusoria 

 as too constant in character, and to overlook the fact that, under 

 varying conditions, modifications may occur which are in no way 

 abnormal. 



13. Throughout the entire period of the cultures no tendency 

 to conjugate was shown in any of the series, and experiments for 

 endogamous and exogamous syzygies failed to produce a single 

 case. 



14. Experiments with KH3PO,, K,HPO„ KCl, KBr, K^SO^, 

 MgS04, and NaCl gave evidence of the extreme sensitiveness of 

 Protozoa to solutions of electrolytes. Initial stimulation with 

 KH2PO4, K2SO4, and KBr in y^^ solutions caused in each case a 

 slight acceleration of the division-rate; while initial stimulation 

 with yto K2HPO4, KCl, NaCl, and MgSO^ caused a slowing of 

 the rate. Daily stimulation with the same solutions of each of 

 these salts invariably caused a marked inhibition of the fission- 

 rate. Initial stimulation with KH2PO4 y^y^ showed no change 

 in the rate while K2HPO4 y^y^ produced a marked increase. 

 K2SO4 gfo^ accelerated division; and KCl and NaCl each in ^ 

 solutions, retarded it; while KBr -^ accelerated the fission-rate. 

 Comparison of the effects of the two solutions of each salt shows 

 that, almost without exception, the more dilute solution produced 

 the greater variation in the rate from the control. 



15. Stimulation with K2HPO4 ytes g^ve different results at 

 various periods of the life-cycle, which indicates that the state 

 of the general vitality of the culture, and also the rhythms, are 

 factors which must be taken into account in experimental work 

 of this nature. 



16. Light has little or no direct effect on the division-rate of 

 Oxytricha fallax. 



Zoological Laboratory, Columbia University, 

 New York, 1905. 



