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



4. THE RELATIVE VITALITY OF PURE LINES 



Jennings ('13) has clearly shown that some races of Paramecium 

 derived from ex-con jugants continue to live in the particular en- 

 vironment of the experimental laboratory conditions, while other 

 races die. This fact indicates an initial difference in vitality in 

 different races and justifies the conclusion that conjugation does 

 not result in all cases in such a reorganization of cellular elements 

 as will enable the ex-conjugant to live as well as either of the 

 parents had lived with its organization prior to conjugation. Our 

 experience with many ex-conjugants confirms these observations 

 in general and leads to the further problem of the relative vitality 

 of different pure lines derived from a single ex-conjugant. We 

 will first consider the vitality of different ex-conjugants. 



We have examined more than 360 ex-conjugants in the course 

 of these experiments. Of these 18 per cent continued to live and 

 multiply normally for more than two months after conjugation; 

 20 per cent died within twenty-four hours after conjugation; 6.5 

 percent died in forty-eight hours; 8.5 per cent in seventy-two 

 hours; 4 per cent in ninety-six hours; 7 per cent in one hundred 

 and twenty hours; 18 per cent in ten days; 7 per cent in twenty 

 days; 5.5 per cent in one month and 2.5 per cent in two months. 

 The chance of life, therefore, is very good if the organisms live 

 through the first ten days during which the causes of death are 

 due in the main to faulty reorganization. The results show in 

 general that about 18 per cent of the ex-conjugants develop 

 progeny capable of living under the conditions of the experi- 

 ments a much lower percentage than that obtained by Miss 

 Cull (70 per cent) which may be explained in part by our use of 

 part wild, part cultured Paramecium. 



Our particular interest at present centers in the relative vital- 

 ity of the different pure lines derived from a single ex-conjugant 

 progeny of one of the 18 per cent that continued to live. Of 

 these the J series is the oldest and most important. 



From the outset it has been evident that the progeny from the 

 different quadrants vary in respect to both vitality and size. 

 The size variations will be considered in another section. The 

 vitality variations are indicated, in general, by the history of the 



