Abstracted by Gary N. Calkins, author. 
Columbia University, New York. 
Uroleptus mobilis Engelm. 
III. A study in vitality. 
In the second of these studies (Jour. Exp. Zool., vol. 29, no. 2) 
it was shown that Uroleptus mobilis after conjugation has an 
initial optimum vitality which gradually diminishes with age 
until the protoplasm finally dies from the exhaustion of metabolic 
activities. In the present paper an analysis of seventeen series, 
all representing the same original protoplasm, shows that the 
differences between them in the matter of vitality are due to 
the age of the parents at the time of conjugation or, rather, to 
differences in vitality at different periods of the life-history. All 
series with an extremely low vitality come from parents which 
were in the period of old age at the time of conjugation; all series 
with high vitality, on the other hand, come from parents in the 
period of youth at the time of conjugation. Continued in-breed- 
ing has not as yet shown any deleterious effect on the vitality 
of the protoplasm under observation. There is some evidence 
that congenital weakness due to old-age conjugation is inherited 
by the later offsprings. 
