Indirect routes by which gonadal hormones influence sexual differentia
tion are considered. In rats, differentiation may depend on the way in
which the mother responds to the hormonal condition of her pups, and
this has implications for the interpretation of the data for humans. I
nteraction between gonadal hormones and light experience in chicks is
compared with the mammalian systems covered in Fitch & Denenberg's rev
iew.