GENETICS: C. B. DAVENPORT 457 
state may be due either to the absence of excitation or the absence of 
depression. 
Now each of the three states of hyperkinesis and its absence may be 
combined with any of the three states of hypokinesis and its absence, 
making nine combination-states. And since there are two parents in 
any mating the number of different matings possible will be the sum of 
the series 9 + 8 + + 1, or 45. 
To account for this variety of temperaments, hyperkinetic, hypoki- 
netic, normal and mixed, various hypotheses were tried and finally the 
following selected as most fitted to explain the facts on an hereditary 
basis. There is in the germ plasm a factor E which induces the more or 
less periodic occurrence of an excited condition {or an exceptionally strong 
reactihility to exciting presentations) and its absence, e, which results in a 
calmness. There is also the factor C which makes for normal cheerfiilness 
of mood, and its absence, c, which permits a more or less periodic depression. 
Moreover, the factors behave as though in different chromosomes, so that they 
are inherited independently of each other and may occur in any combination. 
What the nature of these factors is, whether they affect primarily 
the development of certain parts of the nervous system or the secretions 
of certain glands, is not known and is not involved in the hypothesis. 
It is even conceivable that each state may be due to more than the pair 
of factors here suggested; but if the hypothesis fits the facts it would 
indicate that in the factors E and C we have the predominating influences 
that control mood. 
For the test of the hypothesis 89 carefully described family histories 
were available, and these afforded 147 matings in which the mated pair, 
their parents (usually), and certain of their offspring were sufficiently 
described for the purposes of the test. 
The test of the hypothesis is found in a comparison of the expected 
and actual distribution of temperaments in the children of each sort of 
mating. Of the 45 possible matings 29 were realized. The relations of 
the sums of the observed to the sums of the expected distributions among 
the nine classes of temperaments is shown in the following table. 
choleric choleric choleric nervous nervous nervous calm calm calm 
cheerful phlegmatic melancholic cheerjul phlegmatic melancholic cheerful phlegmatic melancholic 
36 25 30 128 149 63 77 79 46 
41-6/8 46-7/8 19-5/8 98-4/8 154-6/8 72-6/8 51-4/8 97-3/8 49-7/8 
There are several reasons for not expecting a very close relation 
between observed and expected; but the chief one is that there are 
sometimes several 'expected' results; and in these cases the most varied 
result was taken as the 'expected.' Nevertheless, the relation between 
