Rejuvenescence as a Result of Conjugation 87 



was put into a small glass vial containing liquid similar to that 

 from which they had been taken, and these vials were marked in 

 such a way as to indicate the connection between the various 

 individuals. These vials were examined and the animals counted 

 every few days for a month, and a fresh but not a new food medium 

 was given them each time, the same being used for all the 

 organisms. 



Ninety-three pairs of these wild conjugants were isolated at 

 different times and of that number at the end of one month repre- 

 sentatives of sixty-five pairs, or seventy per cent, were alive. At 

 least one of the original conjugants remained of each pair, in the 

 majority of cases both had given rise to offspring. 



Forty pairs of conjugants from long-continued cultures living 

 in the laboratory on hay infusion were isolated by Calkins (loc. 

 cit.) and examined from time to time. Only six pairs, or twelve 

 per cent of these paramecia were represented by living forms 

 at the end of a month. A comparison of -these observations with 

 those now made on the "wild" material would seem to indicate 

 that the fertility of conjugation is dependent upon the condition 

 of vitality in the individuals pairing, for, in both cases, the medium 

 was the same. On the other hand, the explanation may lie in the 

 fact that both conjugants had lived in the medium for many 

 months, so that their chemical composition was too similar to pro- 

 duce a new compound by fusion of their nuclei, this new com- 

 pound being, perhaps, the source of energy for reorganization. 



A study of the mortality of these paramecia showed that at the 

 end of one week the strains of both conjugants had died out en- 

 tirely in six percent of the original ninety-three pairs. After three 

 weeks had passed thirteen pairs, or approximately thirteen per 

 cent, had died. These facts confirm Calkins' observation that 

 conjugation is by no means always successful in producing reju- 

 venescence. 



The point which interested me chiefly in these experiments was 

 that of double or reciprocal fertility — do both conjugants possess 

 new power and ability to carry on the activities of life, or is but one 

 of them fertilized as is the case among higher organisms .? The 

 statistics which were gathered with this in mind show that, at the 



