THE RELATION OF MORTALITY AFTER ENDOMIXIS TO THE PRIOR INTERENDOMICTIC INTERVAL IN PARAMECIUM AURELIA

¹ From the Department of Zoölogy, The Johns Hopkins University

1. Using an interendomictic interval of 20 to 30 days as a standard, it was shown that intervals approximately two, three, four, and five times this long resulted in progressive increases in mortality after endomixis until 100 per cent mortality occurred.

2. At intervals greater than this, the animals died before endomixis could be induced under conditions favorable for its induction.

3. The mean number of generations which non-viable lines survived the climax of endomixis was 5.0 to 5.9 generations when the previous interval was of normal extent. After an interval of 125 days, survival dropped greatly to a mean of 0.9 generation.

4. The results are shown to disagree with current interpretations of mortality at endomixis based on the concept of endomixis as a pathological process.

5. The results show that unusually long interendomictic intervals are, like other previously known conditions, a cause of "natural death" in Protozoa.

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