Feces are discharged through the anus or cloaca during defecation. Adults have cylindrical gonads, opening into the cloaca. Excretory tubules are formed and enter the mesonephric duct, which ends in the cloaca. The male inserts one clasper into the female cloaca during copulation. The bursa develops as a Dorsal diverticulum of the proctadael region of the cloaca. All have paired, internal gonads, connected by ducts to the cloaca. When not in use, the penis is retracted inside a preputial sac in the cloaca. These snakes will also discharge a malodorous, musky-scented secretion from a gland near the cloaca. Overfeeding can sometimes be diagnosed by observing feces trailing from the fish's cloaca. Reproductive organs are found within the cloaca of reptiles. A pair of protonephridia open into a bladder that drains into the cloaca. Chickens have a vaginal aperture that opens from the vertical apex of the cloaca. Most adult placental mammals have no remaining trace of the cloaca. There are two sharp points beneath the cloaca known as the pelvic bone. Some turtles rely on cutaneous respiration from around the cloaca during underwater hibernation.