PARAMOECIUM POSSESSING EXTRA VACUOLES 299 



As stated above, as a rule two vacuoles are added at the time 

 of division (one to the anterior end and one to the posterior end). 

 a, e, i, j, and m represent cases where presumably such an addi- 

 tion has taken place. In b, c, f and g more than two vacuoles 

 have been added although as pointed out above this may be due 

 to post divisional additions rather than to additions at the time 

 of constriction, d, h, and 1 represent cases where only one vac- 

 uole, has been added, w^hile n indicates that there has been no 

 increase whatever. 



d. Effect of various conditions on the vacuole number 



Division rate. Early in the course of these observations it 

 appeared that in newly started cultures of fresh hay infusion 

 where the animals were increasing rapidly the percentage of 

 two-vacuoled forms was frequently very high. On the other 

 hand, in older cultures where the division rate was presumably 

 slower the percentage of multi-yacuoled animals outnumbered 

 the twos. To test this point more accurately, a number of 

 cultures were set up to see whether this condition was the rule. 

 From the time the cultures were well established records were 

 made of the percentage of individuals possessing two, three, 

 four or five vacuoles in each jar every day, or every few days, 

 extending over a period of from two to three months. These 

 records supplied the data for drawing up the accompanying 

 graphs. The results of these experiments have been plotted in 

 various ways to show conclusively that the mode of behavior is 

 essentially always the same. 



In all the charts the three-vacuoled animals are represented 

 by a heavy broken line, the twos by a heavy unbroken hne and 

 the fours by a light unbroken line and when the fives are drawn 

 in a light broken line is used. The figures placed across the 

 various curves in all the charts except No. 5 indicate the number 

 of vacuoles in the form which the curve represents. Chart 3 

 represents a single culture It can be. seen at a glance that 

 although the twos are at first more numerous their line drops 

 rapidly until it meets the axis of abscissas on March 10 while 



