456 
GENETICS: C. B. DAVENPORT 
shows that the periodic occurrence of maximum, far from being clock- 
like in its precision, is distinctly irregular in phase and in other details. 
^Mt. Wilson Contr. No. 92; Astrophys. J., 40, 448 (1914). 
2 A Study of the Light Curve of XX Cygni, Mt. Wilson Contr. No. 104; Astrophys. 
J., in press (1915). 
^Potsdam, Publ. Astrophysik. Obs., 22, Part III (1912). 
THE FEEBLY INHIBITED. III. INHERITANCE OF TEMPERA- 
MENT; WITH SPECIAL REFERENCE TO TWINS 
AND SUICIDES 
By C. B. Davenport 
STATION FOR EXPERIMENTAL EVOLUTION. CARNEGIE INSTITUTION OF WASHINGTON 
Presented to the Academy. June 29. 1915 
Mood or emotional tone depends largely upon temperament; and 
temperament, it is commonly recognized, has a constitutional basis — 
is hereditary; the temperament is as little alterable as stature. How- 
ever, there is a great diversity in temperaments; some persons are 
prevaihngly gay; others prevailingly somber; and still others pass 
through alternating cycles of elation and depression. Of so complex a 
phenomenon the explanation cannot be simple. It must account for 
the following three states: 
(a) the hyperkinetic state — i.e., a state of overactivity. Of this it 
will be convenient to distinguish two grades, a lesser and a greater. 
Following the terminology of an old psychology we may call the lesser 
grade of hyperkinesis nervous. The nervous person is active, energetic, 
irritable, excitable, ambitious, given to planning, optimistic; usually 
talkative and jolly. The greater grade of hyperkinesis is the choleric. 
A choleric person is apt to start a new line of work before he completes 
the old, brags, is usually hilarious, hyperotic, often profane, liable to fits 
of anger, brutal, destructive, assaultive, and even impulsively homicidal 
and suicidal. 
(b) The opposite state is the hypokinetic or depressed. Here too we 
may distinguish two grades. The phlegmatic person is quiet, serious, 
conservative, pessimistic. The melanchoHc person is unresponsive 
(often mute), lachrymose, given to worry, weak and incapable, feels 
life a burden, often longs for death as a relief. 
(c) The normal mood is shown in that the possessor is cheerful with- 
out being boisterous, calm, well balanced, and en rapport socially; he 
works and plays moderately, laughs quietly, does not weep easily, 
feels little drive, and is always responsive and cooperative. This 
