568 THE POPULAR SCIENCE MONTHLY 



2. But if he did keep tliem free from such products, by changing 

 the fluid every day or oftener, no degeneration took place. He thus kept 

 Glaucoma for 683 generations, without a sign of degeneration, and 

 similar results were reached with other species. 



Enriques concluded that the results of Maupas and Calkins are ex- 

 plained by these observations. In their experiments, he holds that the 

 continued action of bacterial products was the cause of the degenera- 

 tion. 



Every one with experience in such work must I believe agree with 

 Enriques that bacterial action is a most important factor in producing 

 degeneration and death. But it seems clear that he was in error in 

 holding that this is the only cause. The most significant feature of his 

 results was the fact that he kept his organisms more than twice as long 

 as did Maupas, with no degeneration whatever. He kept them for very 

 nearly the same number of generations as did Calkins, but in the latter's 

 cultures there had been several crises of degeneration, which finally 

 ended in destruction. Enriques's work indicated strongly that this de- 

 generation was not inevitable, though he may not have explained with 

 full adequacy why it occurs. Enriques drew the general conclusion 

 that there is no such thing as senile degeneration in these organisms; 

 they might enjoy perpetual youth and live without end, if only the 

 conditions are kept healthful. 



Then came the work of Woodruff, with which you are acquainted; 

 work which appears to be definitive for the part of the problem with 

 which it deals. WoodrufE investigated the possibility that the degene- 

 ration observed by Maupas and Calkins may have been due to too great 

 uniformity in the cultural conditions ; or to the fact that the conditions 

 employed lacked something necessary to the continued health of the 

 animals. 



He therefore carried on a set of experiments wherein certain lines 

 were subjected to frequent changes in conditions, while others were 

 kept uniform. As you know, this gave the key to the problem. At 

 last accounts, the progeny of a single individual were flourishing in 

 generations subsequent to the 2,500th, after four years and three months, 

 without conjugation. They had been at that time kept for about four 

 times as many generations as had Calkins's culture when it died out, 

 yet the animals in Woodruff's experiment showed no indication of de- 

 generation. Later work by Woodruff seems to show that if only the 

 culture medium is properly selected, no degeneration occurs even if the 

 conditions are kept uniform. 



The work of Woodruff demonstrates that the very limited periods 

 within which Maupas and Calkins observed degeneration has no sig- 

 nificance for the question as to whether degeneration is an inevitable 

 result of continued reproduction without conjugation. In other words, 

 it annihilates all the positive evidence for such degeneration, drawn 



