PARAMOECIUM POSSESSING EXTRA VACUOLES 



317 



top of the line in a diamond-shaped frame. Directly beneath 

 it is the number of vacuoles in the selected descendents. To the 

 left of this line is placed the number of vacuoles in the sister 

 cell. At first sight it would seem that selection has some effect 

 but figuring the percentage of animals with twos, threes, fours 

 and fives in each line it is found that they vary little more than 

 10 per cent. 



Chart 10 A four-vacuoled paramoecium gave rise to paramoecia possessing 

 the number of vacuoles indicated on this chart. 



Second method. The same difficulty was experienced with se- 

 lecting by the first method as was found in following all the ani- 

 mals for several generations, i.e., the danger of losing an impor- 

 tant individual through drying. By the second method each 

 animal was allowed to multiply for a considerable number of 

 generations. A large number would then be examined and the 

 percentage of twos, threes, fours and fives noted. One would 

 then be isolated to start a new line. In an experiment where 

 selection was carried on for nearly three months according to 



