VIVIPAROUS ANIMALS. 409 
examined, rather of a doubtful character, or leading to a 
conclusion somewhat different from the one which they are 
brought forward to support. 
If the determination of the sex takes place at the period 
of impregnation, the common origin of the testicles and 
ovaria only indicate that in the foetus there is a peculiar 
situation appomted where the production of the essential 
parts of the reproductive system is to take place; since 
previous to the organisation of any part of that system, 
it is fixed whether a testicle or an ovarium is to be pro- 
duced. Again, if the sex is thus determined in the im- 
pregnated ovum, we might expect the peculiar characters 
of the sex more strongly impressed upon the foetus than 
they are known to be; and instead of finding the clitoris, 
(upon the supposition that it is capable of being changed 
into a penis,) of such singular dimensions, its total ab- 
sence in the female might rather be expected. Both 
these circumstances rather intimate, that the ovum is 
neuter, that the sexual organs are in part developed 
previous to the determination of the particular sex, or, 
in other words, after the ege has germinated, and the or- 
gans are in some measure evolved. There are some facts, 

same sex. It may also account for twins being most commonly of the same 
sex ; and, when they are of different sexes, it leads us to inquire whether 
the female, when grown up, has not in some instances less of the true fe- 
male character than other women, and is not incapable of having children. 
It is curious, and in some measure to the purpose, that in some countries, 
nurses and midwives have a prejudice that such twins seldom breed. 
“‘ This view of the subject throws some light on those cases where the 
testicles are substituted for the ovaria; since whenever the impregnation 
fails in stamping the ovum with a perfect impression of either sex, the part 
formed will neither be an ovarium nor a testicle, sometimes bearing a great- 
er resemblance to the one, sometimes to the other; and may, according to 
circumstances, either remain in the natural situation of the ovaria, or pass 
into the situation proper to the testicle, whether it is the scrotum of the 
male, or the labia pudendi of the female.” 
