28 Life and Death, Heredity and Evolution 



merits referring to the process of exchange, and vice versa. 

 What was needed was some method of separating the two 

 processes, to see what effect each has by itself. 



In the meantime, taking conjugation as it occurs, without 

 this analysis, men attempted to find out: first, whether the 

 organisms do grow old and die if conjugation does not 

 occur; second, whether conjugation does save them, does 

 make them young, does cause them to reproduce more ener- 

 getically. 



The first question, as to whether without conjugation the 

 creatures degenerate and die, has cost an infinite amount 

 of labor to generations of investigators. It appeared that 

 as a matter of fact, if the animals were kept without con- 

 jugation they do die out in the course of time; such was 

 the result of the long continued labors of Maupas (1888, 

 1889). After some hundreds of generations without con- 

 jugation the animals weakened, became abnormal, sickened 

 and died. It is worth while to note Maupas' exact results 

 on this point. We may give them in the words of his own 

 summary : 



"I have kept six cultures until their final extinction by 

 senile exhaustion. The first (Stylonychia pustulata) be- 

 came extinct after 215 fissions; the second (Stylonychia 

 pustulata) after 316; the third (Stylonychia mytilus) after 

 319; the fourth (Onychodromus grandis) after 320 to 330; 

 the fifth (Oxytricha) after 320 to 330; the sixth finally 

 (Leucophrys patula) after 660." (Maupas 1888, p. 260). x 



But as other investigators took up the same sort of work, 

 a curious fact was found. As men began to be able to 



1 It is worth noting that different infusoria showed great diversities 

 as to length of life; Leucophrys patula lived in Maupas' experiments 

 for twice as many generations as any of the other species. It should 

 also be observed that Maupas did not carry out such experiments on 

 Paramecium, the organism that has been most used for such work since 

 his time. 



