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 these rudimentary organisms endowed with perennity are the first living forms which have shown themselves on the surface of the globe, and that they 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 phenomenon 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 experiments 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, caryogamic conjugation. It is a rather complicated process in its detail, but it is definitively summed up