THE IMMORTALITY OF THE PROTOZOA. 337 



these rudimentary organisms endowed with perennity 

 are the first living forms which have shown them- 

 selves on the surface of the globe, and that the}- have 

 no doubt preceded many others the multicellular, 

 for instance, which are liable, on the contrary, to 

 decay the conclusion is obvious: Life has long 

 existed without death. Death has been a pheno- 

 menon of adaptation which has appeared in the 

 course of the ages in consequence of the evolution of 

 species. 



The Death of Infusoria. We may ask ourselves at 

 what moment in the history of the globe, at what 

 period of the evolution of its fauna, this novelty, 

 death, made its appearance. The celebrated experi- 

 ments of Maupas on the senescence of the infusoria 

 seem to authorize us to give a precise answer to this 

 question. By means of these experiments we are 

 led to believe that death must have appeared 

 at the same time as sexual reproduction. Death 

 became possible when this process of generation 

 was established, not in all its plenitude, but in its 

 humblest beginnings, under the rudimentary forms 

 of unequal division and of conjugation. This 

 happened when the infusoria began to people the 

 waters. 



The Two Modes of Multiplication. Infusoria are, in 

 fact, capable of multiplication by simple division. 

 It is true to say that in addition to this resource, the 

 only one which interests us here, because it is the 

 only one which confers immortality, they possess 

 another. They present and exercise under certain 

 circumstances a second mode of reproduction, caryo- 

 gamic conjugation. It is a rather complicated 

 process in its detail, but it is definitively summed up 



