AGE, DEATH AND CONJUGATION 565 



he followed thus its history from generation to generation. The crea- 

 tures divided every eighteen hours or so, and for about a liundred 

 generations they remained strong and healthy. Then sickly and de- 

 formed individuals began to appear here and there; these became more 

 and more numerous, till finally all had degenerated thus ; they died out 

 completely at the end of five months, after 215 generations. Another 

 series, beginning with an animal that had just conjugated, degenerated 

 and died at the end of 316 generations; and other series gave similar 

 results. 



Thus, said Maupas, it is clear that these creatures do get old and 

 die, just as higher animals do. The idea that they are potentially im- 

 mortal is a mistake ; death inheres in the process of life. 



But why then are not these creatures all dead ? How is it that they 

 exist at the present time? 



The key to this is found, according to Maupas, and according to the 

 suggestions of many before him, in the process of sexual union. As 

 fertilization saves the life of the egg and permits it to continue dividing 

 for many generations, so does conjugation put new life into the dying 

 infusorian, permitting it also to continue multiplication for many gen- 

 erations. The existence of sexual union in these creatures finds its ex- 

 planation in the fact that they, like ourselves, are mortal; and their 

 mortality is overcome, like our own, by the process of sexual repro- 

 duction. Their lives begin with the strength of youth, and inevitably 

 run down the incline of age, as do our own. 



But Maupas was one of those men who are not satisfied with a bril- 

 liant hypothesis; if conjugation actually restores vitality, he wanted to 

 see it done. He allowed one of his Stylonichias in the 156th genera- 

 tion to conjugate with another that he captured wild. Then he took 

 one from this pair and allowed it to multiply. Most unfortunately he 

 does not say (doubtless he did not know) whether it was the old one or 

 the fresh one that he allowed to continue. But this creature, which had 

 just conjugated, propagated itself for 316 generations before it finally 

 died of old age. Meanwhile, the rest of the old stock, which had not 

 been allowed to conjugate with fresh individuals, died out in 59 gen- 

 erations. 



Thus it appeared to be demonstrated that conjugation restores vi- 

 talit}^, that it rejuvenates. The brilliant hypothesis had seemingly be- 

 come the demonstrated reality. 



But it is interesting to the student of the history of science, and of 

 scientific certainty, to discover that many years before the time of 

 Maupas the function and effect of conjugation had been completely 

 worked out in detail, by the most painstaking investigations, so that in 

 1862 a statement for it could be made that, according to the competent 

 judgment of Engelmann, had been by a great abundance of observa- 



