. ON THE ORIGIN OF DEATH. 121 



might produce by fission a mass of protoplasm which 

 should weigh one kilogram, and that in thirty days the 

 number of kilograms would be represented by i with 

 forty-four zeros, or a mass of protoplasm a million times 

 larger than the volume of the sun. 



Cultures were made of no less than twenty different 

 species of Infusoria, and were maintained during periods 

 of time varying in different cases from two weeks to 

 between four and five months. He found that after 

 from fifty to one hundred generations had been pro- 

 duced by fission, there was clear evidence of a physio- 

 logical decline, which seemed to indicate the approaching 

 extinction of the culture. He withdrew some of the 

 Infusoria from the culture and allowed them to mix 

 with others of a different origin. With these they 

 conjugated, and their full vigor seemed restored. If, 

 on the other hand, they conjugated among themselves, 

 observation showed that decline was so far advanced 

 that the culture was doomed. 



Soon, the animals produced by fission were smaller — 

 often being less than half the normal size. At the 

 same time what might be called pathological changes 

 began to appear. The cilia were absent on parts of the 

 body, and the infusoria seemed weaker and less able to 

 digest food. In some species the micro-nucleus under- 

 went changes, finally falling to pieces, a phenomenon 

 which not unfrequently occurs in the cells of the Metazoa 

 when the tissue is undergoing degeneration. Also the 

 macro-nucleus was found to undergo marked pathological 

 changes, finally breaking down and disappearing. 



When this degeneration, which Maupas calls senile 

 degeneration, has reached its maximum, nutrition be- 



