THE LIFE CYCLE OF PARAMECIUM WHEN 

 SUBJECTED TO A VARIED 

 ENVIRONMENT 



DR. LORANDE LOSS WOODRUFF 

 Yale University 



Studies on the life cycle of Paramecium aurelia (cau- 

 datum) have been made by several investigators, the most 

 extensive work being that of Calkins. 1 As is well known, 

 his results showed that when Paramecium was bred con- 

 tinually in a culture medium of hay infusion, it passed 

 through more or less regular cyclical variations in general 

 vitality as measured by the division-rate. The marked 

 periodical depression periods occurred at about six-month 

 intervals and unless the organisms were "stimulated" at 

 this time the culture died" out. Minor depressions oc- 

 curred about every three months, but from these recovery 

 was autonomous. Joukowsky 2 and Simpson, 3 however, 

 apparently found that certain cultures of this organism 

 died out after being but a short time under culture condi- 

 tions. 



A constant culture medium is an important condition 

 for the study of the consecutive phases of vitality, and of 

 the effect of stimuli on the organism, but it is of interest, 

 however, in the light of the results obtained by this 

 method to determine the character of the life cycle of 

 Paramecium when subjected to a varied environment. 

 It is possible, of course, that some element is lacking in 



1 Calkins, G. N. Studies on the Life History of Protozoa. I, The Life 

 Cycle of Paramecium caudatum. Archiv f. Entwk., XV, 1, 1902. IV, Death 

 of the A Series. Journal Exper. Zool., I, 3, 1904. 



2 Joukowsky, T>. Beitrage zur Frage nach den Bedingungen der Ver- 

 mehrung und des Eintrittes der Konjugation bei den Ciliaten. Verh. Nat. 

 Med. Ver. Heidelberg, XXVI, 1898. 



'Simpson, J. Y. Observations on Binary Fission in the Life History 

 of Ciliata. Proc. Royal Society Edinb., XXIII, 1901. 



