8 LORANDE LOSS WOODRUFF 



tion or artificial stimulation. This conclusion is based on the 

 fact that I have been able to breed a pedigreed race of Paramae- 

 cium aurelia for (so far) over six years or through more than 3800 

 generations without periods of physiological depression— the 

 animals of the present generation being in as normal morphologi- 

 cal and physiological condition as the specimen isolated to ini- 

 tiate the culture. It is apparent, however, that closely related 

 species, and different races. of the same species, are adapted to. 

 more or less diverse environmental conditions, and it is this fac- 

 tor which is undoubtedly at the foundation of the diverse results 

 which have been obtained by various students of the longevity 

 of infusoria in culture without conjugation (cf. Woodruff '11). 



Therefore, in the light of studies during the past decade, I 

 would interpret the cycle of my Oxytricha A culture as being the 

 result of the fact that the race of Oxytricha fallax which was em- 

 ployed was not adapted to live indefinitely ''when continuously 

 subjected to the same environment" of hay infusion ('05, p. 

 627). I believe that if an entirely suitable environment had been 

 secured this culture would have given evidence of unlimited 

 power of reproduction by division without conjugation as my 

 present P. aurelia race has done. In other words this culture 

 of O. fallax affords detailed data in regard to the cytological 

 changes which occur during a long period of gradual physiological 

 degeneration induced by the environment, which should be of 

 great value in determining variations in cell and nuclear size and 

 also the Kernplasmarelation under such conditions. 



III. METHODS 



The methods employed in conducting the cultures of this race 

 are stated in detail in the original paper and are similar to those 

 which I have subsequently used in all my pedigreed culture work. 

 It is only necessary to repeat here that the culture was started 

 by the isolation of a wild specimen on a depression slide in about 

 five drops of hay infusion and when this animal by division had 

 produced four individuals each of these was isolated to form one 

 of the four lines of this culture, O. fallax A. These four lines 



