218 GEORGE ALFRED BAITSELL 



of Infusoria which might be present, and placed in test tubes. 

 On most of these new infusions the animals thrived very well 

 and were present in large numbers in the test tubes a few days 

 later. Some of the anunals were also kept as before on the beef 

 medium in the test tubes but these all died by May 20. The 

 other animals which had been transferred to the new media 

 from the beef medium showed for a time a great unprovement 

 and appeared to have recovered their normal division rate but, 

 about three weeks later, they again showed a low division rate 

 and other signs of degeneration and this time the culture died 

 out (June 10, 1912) after having been carried 231 days or almost 

 eight months. It has been shown, as mentioned above, that the 

 maximum time that these animals lived, in any of the daily iso- 

 lation cultures, was 112 days. We have, then, under the con- 

 ditions in the mass culture more than a doubling of the length of 

 the time of the so-called life cycle as found in the daily isolation 

 cultures. 



To summarize briefly the culture work with this race of Oxy- 

 tricha fallax: Three daily isolation cultures and one mass culture 

 in test tubes were carried, namely. Culture Ob, a daily isolation 

 culture which attained 131 generations in 115 days on a beef 

 extract medium; Culture Oh, a daily isolation culture which 

 attained 159 generations in 105 days on a hay infusion medium; 

 Culture Ove, a daily isolation culture which attained 150 gener- 

 ations in 80 days on a 'varied environment' medium; Culture 

 Obtt, a mass culture kept in test tubes which lived 231 days on 

 the beef extract medium. It is obvious from the experiments 

 with this race of Oxytricha fallax that, although it was impossi- 

 ble to prolong the life of the race indefinitely by any of the media 

 employed, nevertheless it was possible, by the use of the test 

 tube method to greatly extend the so-called life cycle. This 

 result supplies additional evidence that the length of the 'life 

 cycle' and the character of the culture methods are intimately 

 related. 



