6o 



Scientific Proceedings (97). 



in 10 days, a difference in vigor amounting to more than 1 7 divisions 

 in ten days. In other words, if the two individuals, one of which 

 formed the J series, had not conjugated, they would have had 

 only enough metabolic vigor to divide at the rate of one division 

 in 40 days, but, having conjugated, their metabolic vigor was 

 such that they actually divided at the rate of 71.6 divisions in 

 40 days. This is an extreme case; if conjugation occurs before 

 vitality runs so low, the difference between parent and offspring 

 is less. Thus, the C, D and H series came directly from this same 

 A series, C from individuals in the 78th generation, D from the 

 137th and H from the 237th generation, of the parent series. 

 For the first 60 days of each filial series the mean division rates 

 for ten days of offspring and parent were :C 17.26, A 15.73 ;D 1716, 

 A 14.13; and H 17.33, A 12.53, the differences being 1.53, 3.03 

 and 4.80. 



Exactly similar results were obtained with the F 2 , F 3 and F 4 

 generations of the original A series, some of which are dividing 

 today with the optimum vigor of 17 -f- divisions in ten days. 



Directing attention again to the fact that all series are treated 

 in the same identical way as regards food and environmental 

 conditions, and that conjugations were invariably between two 

 individuals of the same age, the conclusion is incontestable 

 that one fundamental effect of conjugation is the renewal of 

 vitality, or rejuvenescence, of the protoplasm. 



37 (1412) 



Endomixis and size variations in pure lines of Paramecium 



aurelia. 



By Rhoda Erdmann. 



[From the Osborn Zoological Laboratory, Yale University, New 

 Haven, Conn.] 



Jennings 1 considers the mean size of a pure line as strictly 

 hereditary throughout the pure line; it belongs to one of the funda- 

 mental characteristics of this individual pure line. Eight years 



1 Jennings, H. S., Proc. Amer. Philos. Soc, 47, 393-546. 



