Rejuvenescence without encystment and without nuclear fusion in Uroleptus?

Abstract

Experiments made during the last two years on Uroleptus mobilis have shown that renewal of vitality follows conjugation, both parents, coming from the same protoplasm and all kept under identical conditions of food and environment. It was also shown that asexual reorganization occurring during encystment, likewise results in rejuvenescence.

It was argued that, since the only Mommon phenomenon in conjugation and encystment is the nuclear dissolution and absorption in the protoplasm, the renewal of vitality after each is due to the chemical and physical changes in the protoplasm set up by the addition of relatively large quantities of nucleoproteins added to it. To test this working hypothesis the following experiments were undertaken last April and May. Individuals of the same ancestry (P series) in the 140th generation, were allowed to conjugate; a normal ex-conjugant was isolated (V series), and this, with the parent P series, were maintained as controls, the latter to show the degree of vitality without conjugation, the former to show the effect of conjugation. Other pairs of conjugating individuals were isolated in a minute drop of culture medium, a pair at a time, and cut with a scalpel across the angle of the V made by the two individuals in conjugation. The detached angle of the V and one of the arms of the V were immediately fixed and stained to determine the stage of conjugation at the time of cutting. The other part was isolated in culture medium and set aside for observation. Seven pairs were successfully cut in this way, and in the desired plane; four of these died within 10 days, three continued to live forming the X series, the X6 series, and the X7 series.