498 G. N. CALKINS AND L. H. GREGORY 



7. NOTES ON THE CONJUGATION TESTS 

 A. So-called 'maturity^ of Paramecium in rich cultures 



Some interesting data have accumulated in connection with 

 the conjugation tests on a phenomenon which for lack of a better 

 term we may call 'maturity.' This does not mean maturity in 

 the sense used by Maupas, namely, that a certain number of 

 generations must elapse before the progeny of an ex-conjugant 

 can again conjugate. The experience of numerous observers has 

 shown that if a line has the ability to conjugate at all, such con- 

 jugations may occur at any time. Jennings, for example, has 

 shown that closely related individuals of Paramecium in the 16- 

 cell stage after conjugation may conjugate again. In our G 

 series abundant conjugations appeared in the progeny three weeks 

 after conjugation of the parent cell; in the H' series, five weeks 

 after; and in the L and Q series six weeks after conjugation. 'Ma- 

 turity' in the Maupas sense, therefore, is not a necessary condi- 

 tion for conjugation. Our experiments show that the organism 

 must remain a certain length of time in the rich cultures where 

 rapid multiplication takes place under certain conditions, one of 

 which is abundant nourishment. When ready for conjugation 

 under these conditions we may say that the organisms are ma- 

 ture. Table 5 and the frequency polygon based upon it show this 

 very clearly (diagram 7). Of the 129 observations, 40 fall in the 

 period from five to nine days, that is, in the curve of the region 

 of. the mode; 52 in the period from one to four days; and 37 in the 

 period from ten to twenty-one days. The curve has little value 

 statistically because different races are included and because ob- 

 servations are so unevenly distributed. These 4 observations on 

 the fifth day gave over 1000 pairs, whereas on the sixth day, 3 

 observations gave only 17 pairs. This discrepancy is due to the 

 fact that different series are grouped together. Nevertheless, 

 the differences are so clearly marked that the conclusions are 

 perfectly obvious. Thus 52 observations made on Paramecium 

 from one to four days in the rich cultures gave only 242 pairs, 

 while 38 observations made on material from five to eight days 

 in rich cultures gave 8578 pairs. From this it appears that ma- 



