Abstract
The process of sexual differentiation of the isopod, Armadillidium vulgare was studied morphologically during early stages of post-embryonic development. Sexual differentiation of gonads was first observed in the testes at the fourth stage. Male endopodites, which develop later into male copulatory organs as one of secondary sexual characters, started to elongate at the fifth stage. The androgenic glands were observed morphologically at the sixth stage. This study suggests that the gonadal primordia start to differentiate into testes in the absence of visible androgenic glands in male A. vulgare. The developmental process of male internal and external sexual characters in malacostracan Crustacea were discussed.
