VITALITY 



249 



with which they have the potential of an indefinitely continued 

 existence. 



The experiments of Maupas (1888) to determine by isolation cul- 

 ture experiments whether Infusoria do actually grow old were not 

 convincing. He found, indeed, that a bit of protoplasm in the form 

 of a single infusorian cell if isolated in a suitable culture medium 

 would live, grow and divide. One individual cell formed by such 

 division, if similarly isolated, would repeat the process, and from 

 its progeny another representative bit of protoplasm would con- 

 tinue the race. Maupas found that, ultimately, such protoplasm 



Fig. 1.30. — Stylonychia pustulata, senile degeneration. B, C, degenerated individuals 

 without micronuclei. (After Maupas.) 



would lose its vitality and the race would die after morphological 

 and physiological evidences of degeneration (Fig. 130). In this 

 manner he followed the history of Stylonychia pustulata through 

 316 generations by division when the race died. Another species, 

 Stylonychia mytilus, died out after 319 generations; Leucophrys 

 patula after approximately 060 generations, etc. The single indi- 

 vidual was isolated in culture medium under a cover-glass and kept 

 in a moist chamber. Here it divided repeatedly during a period 

 of from two to six days until many individuals were present (in 

 one case 935) all descendants of the original ore. One of these was 

 then isolated and the process repeated. From these experiments 



