PHYSIOLOGICAL VARIATIONS IN PARAMECIUM 517 



The conjugating pair dealt with was derived from the line 

 known as Al in Calkins' experiments of 1901-02. This line had 

 been continuously cultivated on slides for 369 generations (from 

 February 1 to December 8, 1901). On December 7 conjugations 

 were found in the stock left over after isolation of the culture 

 individuals and a pair was isolated. On December 8 the two 

 conjugants had separated. One individual lived for fourteen 

 days, dividing 11 times before it died. The other lived for nine 

 months, undergoing 376 divisions during this period. With this 

 line therefore, we have the conditions necessary to test rela- 

 tive vigor of an ex-conjugant and a non-conjugant control 

 from which the conjugant was derived. The ex-conjugant was 

 treated for twenty-four hours with beef extract on December 9, 

 the A series with beef extract on December 14, January 8 and 

 15. They thus had similar initial treatment, the control line A 1 

 receiving three treatments with beef extract, the ex-conjugant 

 onlj^ one. 



The iiumbers of divisions in ten-day periods of both control 

 and ex-conjugant lines are given in table 8. 



The ex-conjugant and control (non-conjugant) lines were car- 

 ried along under identical conditions of environment, both sets 

 in the same moist chamber, both were cultivated in the same media 

 and changed at the same times. The ex-conjugant showed a re- 

 markably heightened vigor as contrasted with that of the pure 

 line from which it came. This contrast is well shown in the ac- 

 companying graph (diagram 8) in which the divisions in succes- 

 sive periods of ten days are plotted for both. 



Reference to table 8 will show furthermore, that the non-con- 

 jugating line (A 1) is weaker than the ex-conjugant line in both 

 halves of the total period. Thus in the first one hundred and 

 thirty days the ex-conjugant divided 173 times, the non-conju- 

 gant control only 150 times. In the last one hundred and forty 

 days the ex-conjugant divided 196 times, the control only 127, 

 giving a total of 396 divisions for the ex-conjugant and only 277 

 divisions for the non-conjugant control. The evidence thus is 

 very strong for the conclusion that increased vitality or rejuve- 

 nescence was brought about through conjugation. 



