THE EVOLUTION OF SEX 27 



had been two hundred and fifteen generations, 

 produced by ordinary division, and since 

 these organisms do not conjugate with those 

 of the same stock, there had been no conjuga- 

 tion. At the date referred to, however, it was 

 observed that something had gone far wrong. 

 The individuals were being born old and debili- 

 tated ; the powers of nutrition were lost ; and 

 the asexual multiplication came to a standstill. 



Meanwhile, before the generations had 

 exhausted themselves, several of the individ- 

 uals had been restored to their natural 

 conditions, where they conjugated with unre- 

 lated forms of the same species. One of these 

 was again isolated and watched for five 

 months. In this case, up till the one hundred 

 and thirtieth generation, the organisms showed 

 themselves able to conjugate with unrelated 

 forms when removed to fresh conditions. 

 Later on, even this power was lost, and at the 

 one hundred and eightieth generation the 

 individuals of the same family were observed 

 making futile attempts to conjugate with each 

 other. 



What happened in these isolated colonies 

 was a wholesale degeneration, both in structure 

 and function. The individuals decreased in 

 size until they were only a quarter of their 

 original proportions, they showed very marked 

 nuclear degeneration, the powers of feeding 

 and dividing came to an end, the senile stock 

 finally died out. 



From all this Maupas drew a natural 

 inference that there is a limit to the number 

 of successive asexual divisions, and that 

 conjugation must occur, else the whole life 



