Theories of Rejuvenescence 147 



Paramecia which had conjugated did not reproduce faster, 

 but that, on the contrary, it was those that had not been 

 allowed to conjugate that multiplied more rapidly. Speak- 

 ing of the theory that conjugation increases the energy 

 of reproduction, Hertwig says : 



"The grounds on which this theory is based have already 

 been combated by Maupas ; he showed by extended experi- 

 ments that the power of multiplication of an infusorian is 

 neither decreased before conjugation nor increased after it. 

 ... I am compelled to say that Maupas was entirely right" 

 (1889, p. 222). 



What then did Maupas and Hertwig mean by holding that 

 conjugation does nevertheless rejuvenate? 



Maupas' theory is not easy to seize or to state in experi- 

 mental terms. He believed that without conjugation the 

 organisms became deformed and structurally degenerate, 

 although their power of reproduction remained unimpaired ; 

 at last they died. Conjugation, he believed, if it occurs 

 before degeneration has become evident, prevents the process 

 of degeneration. His own experiments showed him, as we 

 shall see, that after observable degeneration has begun con- 

 jugation does not remedy it. The only test for Maupas' 

 theory is formed by such experiments as those of Woodruff, 

 in which it is shown that even without conjugation the ani- 

 mals live indefinitely and do not degenerate. 



Hertwig (1889), taking the bull by the horns, held with 

 relation to Paramecium, that an increase in the rate of re- 

 production was one of the symptoms of degeneration; that 

 conjugation in restoring the balance decreased the rapidity 

 of fission. It is extraordinary that two such contradictory 

 views can be held of what conjugation does, as are these two 

 Hertwig on the one hand maintaining that conjugation 

 decreased the rate of reproduction, Calkins on the other 

 that it increases it both under the name of rejuvenescence! 



