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ROBERT T. HANCE 



effect of conjugation shows conditions similar to the above. 

 Chart 6 illustrates graphically the relation between the division 

 rate and the percentages of animals possessing various numbers 

 of vacuoles. The very heavy line represents the division rate 

 and it can be readily seen how the percentage of two-vacuoled 



Chart 6 This graph compares the fluctuations of the number of two, three 

 and four-vacuoled paramoecia in a single culture for a period of nearly two 

 months with the daily division rate. The division rate was obtained by isolat- 

 ing a number of single animals in separate watch glasses in fluid filtered from 

 the main culture. At stated intervals an average of the number of divisions 

 that had occurred in all the watch glasses was struck. The figures in circles 

 at the extreme left of the chart indicate the number of divisions and the broad 

 black band traces the division rate across the graph. The other figures are the 

 same as have been used on previous charts. It is evident from this chart that 

 in general while the threes and fours increase as the division rate decreases 

 there is apparently another factor at work that cannot be accounted for on 

 this basis. 



animals rises and falls with the increase or decrease of the fission 

 rate. 



Age of the culture. To determine whether paramoecia divide 

 more rapidly in fresh hay infusion than in an old, worn out 

 medium, liquid was filtered from a culture nine months old. A 

 few drops of this fluid was placed in several watch glasses and a 

 paramoecium taken from the same culture as the liquid was iso- 

 lated in each. From this same old culture single paramoecia 

 were placed in similar amount of fresh hay infusion. In six 



