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[Vol. L 



Paramecium can datum during depression. In either case 

 if a labile protoplasm can be restored resulting in cliemical 

 activities which ultimately bring about dissolution of 

 these formed products, then renewed vitality is the out- 

 come. Asexual reorganization effects this result, but the 

 same result was produced artificially by the use of salts 

 in my experiments with Paramecium caudatum during 

 conditions of depression, and in cases where the cell body 

 was visibly loaded with products which it could not auto- 

 matically dispose of. The splendid results which Bass has 

 obtained in cultivating Plasmodium in vitro and in the 

 presence of sugar, indicate the possibility of malaria 

 organisms while in a stabile condition being similarly 

 changed into a labile condition by changes in the blood 

 content of the host. Changes thus set up might well be 

 the equivalent of asexual reorganization or partheno- 

 genesis, or the equivalent of fertilization in restoring 

 vitality. 



In this sketch of the protozoan life cycle I have endeav- 

 ored to give a comprehensive though somewhat specu- 

 lative account of the different phases of vitality which may 

 apply equally well to any type of Protozoa. Cell division, 

 reorganizing encystment or its equivalent, and conjuga- 

 tion, are all regarded as phenomena of the same general 

 character but differing in degree, the effect in each step 

 being the restoration of the protoplasm to a condition 

 more or less free from cumulative metabolic differentia- 

 tions. 



REFERENCES 



