The hemipenis of Chameleons

Chameleons possess two copulatory organs on the left and right sides, called hemipenes. These organs are situated in pockets at the base of the tail and can retract into them, controlled by a specific muscle that relaxes when the organ is extended. 

Erection o evertion of the hemipenes occurs through lymphatic flow rather than blood, as is the case in mammals. 

In freshly deceased male specimens of chameleons, the hemipenes can be artificially everted by injecting liquid into the hemipeneal pocket at the base of the tail. This procedure requires a syringe, a fine needle, and some experience. Once everted, the structure and form of the organ can be observed, noting features such as the rotulae and papillae on the top of the hemipenis. At its stem, known as the truncus, the hemipenis displays the sulcal side with the sulcus spermaticus and the asulcal part, which is covered with calyces.