PARAMOECIUM POSSESSING EXTRA VACUOLES 



313 



It is of considerable interest to note that when conjugation 

 did take place in cultures to which a minute quantity of sea salt 

 had been added the epidemic did not last nearly as long as in 

 the untreated infusions. In one set of experiments conjugation 

 lasted for twelve days in the unsalted culture while in the cul- 

 ture containing 0.1 per cent sea salt it died out in three days. 

 Another time an untreated medium maintained conjugation for 

 thirty-three days against thirteen and nineteen days in two salt 

 cultures. The length of one of the periods of conjugation is 

 figured on chart 7. 



Chart 7 This chart was drawn from records obtained from a single culture 

 and illustrates the percentage of conjugants to unfused forms found during a cycle 

 of conjugation. The figures in the circles at the extreme left of the chart indi- 

 cate the percentage of conjugants and the heavy black band traces the fluctua- 

 tions of the percentage of conjugants across the graph. The other curves repre- 

 sent either individuals or conjugants and are labeled on the chart. It will be 

 noted that when the number of conjugants is high the percentage of three and 

 four-vacuoled forms decrease and increase as conjugation dies out. 



In brief, conjugation has been obtained in cultures that 

 have been started with single individuals under the following 

 conditions. 



1. Conjugation appeared in practically all cases when the 

 culture was evaporated rapidly causing the metabolic products 

 to concentrate considerably. 



