1. Rooster doesn't have a penis like mammals, but it has a mating organ consisting of nipple, glandular duct, penis and lymph nodes. The copulatory organ is located on the ventral side of cloaca, and it is always hidden in cloaca.

2. During sexual excitement, the lymphatic vessels in the glandular duct, penis and lymphatic folds communicate with each other, and the lymphatic folds erect, and lymph flows into the penis to expand it, forming a deep longitudinal groove at the midline. The middle penis body (central white body) at the front end of the midline also protrudes forward because of the inflow of lymph. At this time, the whole penis is pushed out from the abdomen of the anus and inserted into the anus of the hen.

3. The vas deferens is parallel to the ureter and opens in the cloaca. The cock has no real penis, only a small white protrusion at the middle junction of the second fold of cloaca, with eight-shaped folds on both sides, which constitutes a degenerated copulatory organ. During mating, the double winter folds of the pagoda form an ejaculatory groove, through which semen is injected into the hen's vagina.