72 



Scientific Proceedings (104). 



43 (1503) 



Age of parents and vitality in Uroleptus mobilis. 

 By Gary N. Calkins. 



[From the Department of Zoology, Columbia University.] 



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 re- 

 sulted 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 off- 

 spring series and represent the vitality remaining in the parental 

 protoplasm. 



High vitality in a series is indicated (1) 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, (1) and (2). 



High vitality was shown in all three ways by series C, F, J, 

 P, Ui, U 2 , and V. Low vitality was shown in all three ways by 

 series Q, R, and a, while series W and H were low in regard to 



