Note (return) — ORGANIC DIFFERENCES IN THE SEXES

In close connection with the foregoing we have the fact, reported by Maupas,16 that certain Infusorians are capable of reproducing asexually for a number of generations, but that, unless the individuals are sexually fertilized by crossing with unrelated forms of the same species, they finally exhibit all the signs of senile degeneration, ending in death.17 After sexual conjugation there was an access of vitality, and the asexual reproduction proceeded as before. "The evident result of these long and fatiguing experiments is that among the ciliates the life of the species is decomposed into evolutional cycles, each one having for its point of departure an individual regenerated and rejuvenated by sexual copulation."18