AGU, DEATH AND CONJUGATION 569 



from work on the infusoria. It justifies the statement that the evi- 

 dence is in favor of the power of these organisms to live indefinitely, if 

 they are kept under healthful conditions. It shows that Weismann was 

 correct in what he meant by speaking of the potential immortality of 

 these organisms. 



Thus I believe that we may feel that one of our two main questions 

 has been definitely answered. Old age and death have no necessary 

 place in the life of these creatures, even without conjugation. 



But this brings the second question back to us with greater force 

 than ever. What then is the efEect of conjugation? "What role does it 

 play in the life of these creatures ? Are we wrong in looking upon sex- 

 ual union as a token of mortality? 



This is the question to which I have addressed my own investiga- 

 tions, and with your permission I will speak next of these. 



Before taking up directly the effects of conjugation, I would like to 

 mention two subordinate points. First, in regard to the question that 

 we have just discussed. Five years ago I started cultures from separate 

 single individuals. During all that time there has been no opportunity 

 for conjugation with unrelated animals, such as Maupas held to be 

 necessary for continued life. Yet these cultures are still alive and 

 flourishing. Thus the progeny of a single individual may certainly 

 continue to multiply for five years without admixture from outside. 

 This then agrees with Woodruff's results, save that Woodruff knows 

 that there has been no conjugation of even related individuals in the 

 line which he follows. But Maupas found, as we saw, that conjugation 

 among the progeny of a single individual does not help, but is actually 

 harmful; if such individuals conjugated, their doom was sealed. 



But is this result of Maupas generally true ? Is inbreeding among 

 the progeny of a single individual injurious ? Or did Maupas's animals 

 die merely because they conjugated when in a dying condition ? 



To test this point, I caused the progeny of a single individual to 

 conjugate together frequently. There was no evil result whatever from 

 this. To carry the process to an extreme, I caused nine conjugations 

 in succession within a single line, each pair being in every case the 

 progeny of one member of the preceding pair. Thus the forefathers 

 of the existing race have gone through the process of conjugating to- 

 gether nine times. Yet the progeny are as strong and well as ever. 



It seems clear therefore that conjugation with close relatives is not 

 harmful in itself, in these creatures, though repeated many times. It 

 is of course possible that there are differences on this point among the 

 infusoria, just as there appear to be among higher organisms. But it 

 is certainly not a principle of general validity that inbreeding is 

 harmful. 



But now we come to the main question. What difference does con- 

 jugation make in the life of the race ? 



VOL. i,xiiiii. — 38. 



