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ROBERT T. HANCE 



vacuoled forms tend to predominate, as fresh hay infusion was 

 used for each generation. As has been pointed out before, fresh 

 medium causes the animals to divide more rapidly and that 

 rapidity of division may be said in a general way to keep the 

 number of vacuoles low. 



232233233322323 2 



Chart 9 In this case the line was started with a three-vacuoled paramoecium. 



b. Effect of selection 



Selection has been carried on in three ways. 



First method. Individuals possessing two, three, four and 

 five vacuoles were isolated. When they had divided, the num- 

 ber of vacuoles in each was recorded and, in the case of the 

 two-vacuoled line, the paramoecium wdth the lowest number of 

 vacuoles was allowed to continue while in the three, four and 

 five-vacuoled lines the highest vacuoled animals were always 

 selected. The individuals not selected for continuing the lines 

 were discarded. This plan was carried on for a period of from 

 nine to fourteen generations and the results are given on chart 

 11. Here the vacuole number of the progenitor is placed at the 



