910 H. H. NEWMAN AND J. THOMAS PATTERSON 
THE HEREDITARY CONTROL OF SEX 
The only character that seems to be rigidly controlled—which 
does not vary at all in the members of a given set of foetuses— 
is the character of sex. Whether the set shall be male or female 
is apparently settled at the time of fertilization and has its physi- 
cal basis presumably in a dimorphism of the spermatozoa. Sex 
having been determined, there is no room for individual variation 
with regard to this character, unless there be such a thing as a 
more or less pronounced maleness or femaleness. If degrees of 
sex do exist they no doubt express themselves in terms of fertility. 
Along with the primary character of sex are predetermined all 
of the secondary sexual characters, but these are not so rigidly 
controlled. Probably no more highly variable characters exist 
than those that are associated with sex. In the armadillo the two 
sexes are remarkably alike with regard to somatic characters. 
So similar are the two sexes that we have never been able to tell 
them apart without examining the genitalia. A statistical 
study of the scutes has, however, revealed a sexual dimorphism 
in the scute numbers. The mean number of scutes in males is 
a little higher than that in females, but the difference is one of 
only four or five scutes in the whole banded region. A more 
pronounced dimorphism exists in the comparative variability of 
the two sexes. Not only in the species, but within the confines 
of the various fraternities, the males are decidedly more variable 
than the females. Is there any structural dimorphism of the 
hereditary materials that could be held to be in ahy way corre- 
lated with this variational dimorphism? 
A preliminary study of the spermatogenesis of this species has 
revealed that a dimorphism of the spermatozoa probably exists. 
If the results of a more extensive study support this tentative 
conclusion, it will be possible to bring the question of the pro- 
duction of male and female sets into line with the general conclu- 
sions already reached on sex-determination in the other forms in 
which a dimorphism of the sperms brings about a balanced 
chromosome complex in the female and an unbalanced one in the 
male. Can there be any underlying connection between the bal- 
