172 
be overlooked, particularly as similar 
difficulties are found in the tables of 
some of the other types of matings. 
That nomadism is hereditary, Dr. 
Davenport’s study goes far to prove. 
That it is hereditary as a sex-linked 
character, the study does not prove. 
Moreover, many of the facts cited by 
Dr. Davenport—for example, that the 
nomadic instinct fails late in life, just 
as the sexual instinct does—indicate 
that it is really a sex-limited rather than 
a sex-linked character; that its associa- 
tion with sex is not wholly a matter of 
accident, as he assumes that it is. 
If there is anyone who has not an- 
swered to his own satisfaction the 
question Why Girls Leave Home, we 
can at least give him a clue. It is 
because they inherit some of the 
qualities properly belonging to their 
more unstable, restless and nomadic 
brothers. 
INHERITANCE OF TEMPERAMENT 
Following his study of nomadism, 
Dr. Davenport undertakes an analysis 
of the distribution in families of tem- 
perament or its expression in mood. 
This is a problem of great fundamental 
importance, and it is a pleasure to note 
that eugenists are showing a tendency 
nowadays to attack such problems, 
instead of concentrating all their atten- 
tion on degenerate conditions or trivial 
traits of no concern to the race. 
We all recognize a certain average of 
normal temperament, says the writer, 
and we also recognize that this may 
change to an increased activity and 
elated emotional tone, on the one hand, 
or to a decreased activity and lower 
emotional tone on the other. He em- 
braces all moods in these two divisions: 
the ‘hyperkinetic state”’ is that marked 
by one or all of the following elements: 
destructiveness, exaltation, homicidal 
acts and. threats, irritability, psycho- 
motor excitement, and violence. The 
“hypokinetic state” is on the whole 
the opposite of this, marked by anx- 
iousness, worry, fear, slow movement, 
and so on. Finally, there is often an 
alternation of these two states. 
The existence of these two contrasted 
moods, and the fact that an individual 
The Journal 
of Heredity 
often passes from the one to the other, 
will be recognized by every one. But 
an examination of family histories shows 
that in some families there is a prevail- 
ing tendency for the one condition, in 
other families for the other. Dr. Dav- 
enport undertakes the task of bringing 
under one general scheme the inheri- 
tance of these various types of mood, 
and evolves the following hypothesis: 
There is in the germplasm a factor, &, 
which induces the more or less periodic 
occurrence of an excited condition (or an 
exceptionally strong reactibility to exciting 
presentations) and its absence, e, which 
results in an absence of extreme excitabi- 
lity. There are also the factor, C, which 
makes for normal cheerfulness of mood, 
and its absence, c, which permits a more 
or less periodic depression. Moreover, 
these factors behave as though in different 
chromosomes, so that they are inherited 
independently of each other and may 
occur in any combination. 
This hypothesis is tested on eighty- 
nine families, embracing 629 progeny, 
many discrepancies are ascribed to 
“imperfect dominance,’ and in con- 
clusion Dr. Davenport says “it is 
morally certain”’ that the hypothesis is 
correct. 
Even though the confession of a 
doubt be tantamount to a confession 
of immorality, the reviewer cannot 
accept the conclusion with as much 
confidence as Dr. Davenport does. It 
seems to him that the whole analysis of 
moods is open to attack from the 
psychologists, and that the formula 
used to explain the heredity would 
explain almost anything. In other 
words, the reviewer cannot help feeling 
that Dr. Davenport has made the case 
much simpler than it really is. 
He presents data on the inheritance 
of temperament in twins and the inher- 
itance of the suicidal impulse. Even 
though it may eventually be found 
that his analysis of the inheritance of 
mood is not exhaustive, he must be 
given credit for having attacked an 
interesting, complicated, and important 
problem, and for having shown that in 
our daily behavior, where the power of 
heredity would perhaps be little sus- 
pected, our reactions are largely due 
to the hereditary nature of our tem- 
peraments. 
