58 GEORGE ALFRED BAITSELL 



the animals on a stock slide would die in the course of two or three 

 days. In the other stock slides, on which a sufficient number of 

 animals were present, numerous pairs of conjugants would be seen. 

 (2) The appearance of the animals in the culture. Conjugation 

 had not been present in the culture many days before it could 

 plainly be seen that in many of the non-conjugants a degenerative 

 process was taking place. Such animals were more sluggish, not 

 normal in shape and they were considerably darker in appearance. 

 In the days just preceding the death of the culture this condition 

 became more and more intensified and it became increasingly diffi- 

 cult to find normal, active animals in the culture. Many of the 

 animals isolated in the main lines, instead of dividing, would 

 degenerate and die. An apparently normal individual isolated 

 in the morning would, in many instances, by the afternoon of the 

 same day have passed through degenerative stages resulting in a 

 decrease in size, change of shape, decrease in activity, etc. Exam- 

 ined again later in the evening of the same day it was very 

 evident that these changes were more intensified and they gen- 

 erally resulted in the death of the animal that same night. This 

 degeneration was observed in a very large number of non-conju- 

 gants especially in the days shortly before the death of the culture. 

 As soon as it was noted that the division rate of the culture was 

 rapidly falling, various other media were used in an endeavor to 

 stimulate some of the animals. The Sb culture was continued on 

 the beef extract medium as formerly but from it sub-cultures were 

 started by isolation and placed on a number of other media such 

 as hay infusions of varying strengths, the 'varied environment' 

 medium, and solutions of beef extract of different strengths. The 

 effect of different temperatures was also tried. From all these ex- 

 periments the results obtained were entirely negati^^e, none of the 

 sub-cultures thriving as well as the original culture kept on the 

 regular beef medium and all dying out within a few days. In a 

 number of instances the change of medium caused an almost in- 

 stantaneous death. The protoplasm of the non-conjugants ap- 

 peared to be in a condition in which it was impossible for it to 

 withstand any changes. The fact that the Protozoa, when in a 

 weakened condition, are unable to endure a change of medium has 



