602 SIDNEY I. KORNHAUSER 
development of the external genitalia, the oviduct and uterus, 
and the structure of the gonad of the female twin which becomes 
a free martin. Not only the interstitial cells of the testis pro- 
duce hormones, but it is known that the ovary likewise makes 
important secretions. Steinach (’12) feminized rats by cas- 
trating young males and implanting ovaries. These animals 
later displayed many female characteristics of skeleton and hair 
pattern; they developed mammary glands and psychic activities 
of the female, while the external genitalia remained small and 
undeveloped. Im birds Goodale (’16) has conclusively shown 
that the absence of the ovary allows the male secondary sexual 
characteristics of the species to be fully developed in the female. 
Goodale believes that the ovarian hormone acts as an inhibitor, 
which normally prevents the appearance of those characteristics 
that we associate with maleness. 
Since such intimate association of somatic characteristics with 
the presence or absence of gonads exists in the vertebrates, it is 
not surprising that the results on the castration of insects pre- 
senting absolute independence of somatic characteristics should 
be doubted and criticised. KKammerer (’12) would lead us to 
believe that those who followed in Oudemans’ (’98) footsteps 
and extended the work on the castration of insects, investigators 
who improved the methods and succeeded in the implantation 
of gonads of the opposite sex, had interpreted their results blindly, 
merely accepting the belief in the fixity of the somatic sexual 
characteristics of insects as propounded by Oudemans, and 
extending his observations and ideas without question as to 
their correctness. Certainly, Kammerer’s attitude seems rather 
extraordinary, for the researches of Meisenheimer (’09) and 
Kopeé (11, ’13, a, ’13, 6) seem strictly scientific, well planned, 
accurate, and convincing. But aside from these experiments, 
gynandromorphs, such as are occasionally met with in the ar- 
thropods, are convincing evidence of the independence of somatic 
development in this group of animals. One half of the body 
may be perfect in its male characteristics and the other half 
female, and within the abdomen there may be present either 
testes or ovaries or gonads of both sexes. In fact, all possible 
