468 
ZOOLOGY: F. R. LILLIE 
and vasa deferentia, but no trace of uterus or vagina. The testes had 
descended and lay beneath the skin in the region of the groin. No 
scrotum was formed and the external parts were typically female. A 
free-martin described by Numan in 1844 was even farther transformed 
in the male direction, and the external parts were also modified. 
The various cases can be arranged in a series of increasing male- 
likeness, but the transformation of the female zygote owing to action 
of the male sex-hormones does not in the case of the free-martin, in the 
material at our command, proceed all the way to the normal male 
condition. It is perhaps worth noting that, if it ever did, we would be 
unable to detect it, except on a basis of much larger statistics than we 
possess. But the rarity of the more extreme detectable cases makes it 
seem very improbable that other cases jump all the way across the gap 
to the normal male. 
It follows from the data that the female zygote must contain factors 
for both sexes; the primary determination of the female sex must there- 
fore be due to dominance of the female factors over the male. If we think 
of this as a simple quantitative relation, as Goldschmidt^ (1916) has done, 
we can explain the intersexual condition of the free-martin as due to 
an acceleration or intensification of the male factors of the female zygote 
by the male hormones. The degree of the effect which is quite variable, 
as we have seen, would of course be subject to all quantitative variations 
of the hormone. Thus the case of the free-martin could come under the 
same general point of view as that of the intersexes of Lyman tria accord- 
ing to Goldschmidt with the one exception that the quantitative dif- 
ferences between the male and female factors of the female zygote 
necessary for the differentiation of female characters, are reduced in the 
free-martin by internal secretions instead of by variations of potency 
of the male factors in different varieties as in the intersexual hybrids 
of L3anantria. 
The case of the free-martin shows that a gonad with a primary female 
determination may form a structure which is morphologically a testis, 
(cf. Chapin 1917) through suppression of the cortex and over develop- 
ment of the medullary cords and urinogenital union under the influence 
of male sex-hormones. Lesser degrees of transformation are of course 
possible, so that it is certain that the gonad of a mammalian female 
zygote is capable of most, at least, of the series of transformations that 
may exist between an ovary and a testis. Whether the transformation 
in the male direction may proceed under such conditions to the pro- 
duction of true spermatocytes and spermatozoa is at least doubtful. 
Such elements have not hitherto been described for free-martins, if we 
