Age of parents and vitality in Uroleptus mobilis

Abstract

Previous studies on the vitality of Uroleptus mobilis have shown that all ex-conjugants start with an initial high vitality as measured by the division rate. From this initial high rate, vitality gradually decreases during the life cycle until the race dies a natural death. After the first fifty days of a cycle endogamous conjugation may occur at any time with a resulting renewal of vitality in the ex-conjugants. Sufficient data have now been obtained to indicate that there is a difference in vitality of offspring given off at different age periods of the parental series, and a summary of such data is shown in the accompanying table.

Line 1 gives the total number of generations, or divisions, in in each series; line 2 the total number of days required for those divisions; line 3, compared with line 5, indicates the extent of the renewal of vitality resulting from conjugation; line 4 gives the average division rate for any ten days of the entire life cycle on the assumption that divisions are equally distributed; line 6 gives the age of parents in days, at the time of conjugation which resulted in the offspring series, and line 8 the age in generations; lines 7 and 9 give the number of days and the number of divisions subsequent to the time of conjugation which resulted in the offspring series and represent the vitality remaining in the parental protoplasm.

High vitality in a series is indicated (I) by a high division rate which represents high metabolic activity; (2) by the large number of generations, or divisions, which the series undergoes, indicating a combination of high metabolic activity and endurance or lasting capacity; and (3) by endurance or long length of life of a series in days which may be combined with, or independent of, (I) and (2).