I9I2] Lorande Loss Woodruff 399 



cell may be self-sufficient to perpetuate itself indefinitely, and 

 eliminates the phenomenon of conjugation or fertilization as a 

 fundamental inherent necessity of protoplasm for its continued 

 existence (cf. plate VI). 



II 



It being established that this race of ParamcEcium may be bred 

 indefinitely on a culture medium which is frequently varied, the fol- 

 lowing question suggested itself: Is the longevity on a varied 

 environment dependent upon intrinsic Stimuli from the frequent 

 changes of the medium, or is a constant medium of hay infusion 

 unfavorable because it lacks some elements which are essential for 

 the continued existence of this protozoon. 



To test this point it was necessary to find, if possible, a suitable 

 constant culture medium that contains all the elements which the 

 organism demands, and to determine its effect on the vitality of 

 Paramcecnifn when subjected to it for a considerable length of 

 time. If such a suitable medium could be secured on which para- 

 msecia would live indefinitely, it is apparent that the possible con- 

 tinual daily Stimulation afforded by varied culture media is not the 

 crucial factor in the determination of the longevity of this culture. 

 Further, and aside from this interesting theoretical consideration, 

 such a favorable constant culture medium would be valuable for 

 breeding paramsecia in many lines of experimental work, since it is 

 well established that the reactions of paramsecia to various reagents, 

 etc., are greatly modified by their past and present environment. 



The favorable results secured first by Calkins^ with strong Solu- 

 tions of beef extract as a temporary stimulant for degenerating 

 paramaecia cultures in infusions of hay, and later by WoodrufiF^ 

 with Oxytricha under similar conditions, suggested the use of a 



* Calkins : loc. cit. 



'Woodruff: An experimental study on the life history of hypotrichous In- 

 fusoria. Journ. Exper. Zoology, vol. 2, no. 4, 1905. 



