EEPRODUCTION OF THE HYPOTRICHOUS INFUSORIA 223 



days on a hay infusion medium; Culture Pb, a daily isolation 

 culture which attained 943 generations in a period of 478 days 

 on a beef extract medium; Culture Phtt, a mass culture kept in 

 test tubes on the hay infusion medium, which is still thriving 

 at the present time (November 20, 1913) more than 22 months 

 after it was first started and which gives every evidence of being 

 able to live indefinitely under these conditions without conju- 

 gation or artificial stimulation. 



IV. PREPARED MATERIAL 



The study of the prepared material of Oxytricha fallax and 

 Pleurotricha lanceolata, taken from the cultures which died out, 

 reveals the fact that unsuitable culture conditions may bring 

 about great nuclear and cytoplasmic changes in these organisms. 



1. Oxytricha fallax 



Figures 1 to 6 are from material taken from the Oxytricha 

 fallax cultures. The animals preserved at the beginning of the 

 work showed a normal morphological condition, as is seen, for 

 example, in figure 1. Among the individuals preserved a month 

 or so later occasionally an abnormal individual was found. An 

 example of this is shown in figure 2. The cytoplasm of this 

 animal still appears to be in a practically normal morphological 

 condition but in the nuclear structure is to be seen evidence of 

 degenerative changes. As the cultures became still older a very 

 much greater proportion of atypical individuals were found 

 among the specimens preserved and in many cases the appear- 

 ance of the animals while still alive showed that they were not 

 normal. Shortly before the death of the daily isolation cultures 

 practically every animal that was preserved showed a degenerate 

 condition. In figures 3 and 4, which are from specimens pre- 

 served later in the work, are shown other specimens of degen- 

 erate animals. Figures 1 to 4 were all taken from specimens 

 preserved from the daily isolation cultures. 



The animals mentioned above apparently do not differ from 

 those obtained by former investigators along this line and by 



