A hemipenis (plural hemipenes)'s one of a pair of intromittent organs of male squamates (snakes, lizards and worm lizards). Hemipenes are usually held inverted, within the body, and are everted for reproduction via erectile tissue like that in the human penis. Only one's used at a time, and some evidence indicates males alternate use between copulations. The hemipenis itself has a variety of shapes, depending on species. Often the hemipenis bears spines or hooks, in order to anchor the male with… (More on Hemipenis)