284 H. S. JENNINGS 



other day. In some experiments two individuals of each hne 

 were transferred to the new sUde, in others only one; the remainder 

 being destroyed. 



The slides w^ere kept in moist chambers, on strips of glass 

 which were supported above water covering the bottom of the 

 vessel. 



Records. At each transfer the number of fissions undergone 

 since the last transfer was recorded; so that these records were 

 made either every day or every other day. Since either one or 

 two individuals had been left on the slide at the previous trans- 

 fer, there was no difficulty in determining how many fissions had 

 occurred. In some cases of course the same number of fissions 

 had not occurred in the two individuals left the day before, but 

 this made absolutely no difficulty in practice. If, for example, 

 ten individuals were found on the slide, invariably four of these 

 were distinctly smaller than the other six. This showed that 

 each of the two original individuals had divided twice, producing 

 8, and that two of these 8 individuals had divided again, giving 

 the four small specimens out of the ten. If therefore two of 

 these small individuals were transferred to the new slide (as would 

 usually be done in such a case), the number of fissions was re- 

 corded as three. 



For keeping records of large numbers of cultures (the numbers 

 ran up to 480 in some cases), the following procedure is con- 

 venient. Procure hollow ground slides of which the upper sur- 

 face has been ground, so that one can write on them with a lead 

 pencil. Then at transfer write upon the new slide (besides the 

 designation of the line) the number of specimens found in the 

 old slide, the number left in the new one, and an indication of 

 the generation to which they belong. Thus in the case just 

 cited, where 10 individuals were present and two of the smaller 

 ones were transferred, the legend on the new slide would be simply 

 '10 (16)-2'; which indicates that 10 were present; that 2 wer 

 retained, and that if the fission from which these two resulteu^ 

 were complete, there would have been 16 on the slide. After 

 all the slides have been thus transferred, labeled, and placed in 



