"The gonadal region of the female is located on the ventral posterior portion of the body, where the tail joins the abdominal cavity. This slit includes both the anal and the genital openings. To be entered by the penis of the male, it must be pressed open, as it were, by the entering penis. The female has two mammary slits, one on each side of the genital slit. The nipples obtrude from the slits during suckling by the baby dolphin. The mammary glands themselves are buried deep within the body and extend anteriorly from the slits. The female has a bicornuate uterus, and although reports of single births predominate in the literature, Aristotle refers to the births of twins. Aristotle apparently knew these animals extremely well_we should not really look askance at anything he has related until we have evidence to the contrary; we have been able to corroborate some of his behavioral data which had been discounted by scholars during intervening centuries. "The testicles of the male are buried in the body, extending anteriorly from the genital slit on each side, and are amazingly large. We have recently dissected an animal in which the testicles were twelve inches long, about two inches in diameter, and cylindrical in shape. The penis of a fully developed male is approximately six inches long, and with eight inches maximum for length. The base, fore and aft, is about four to five inches, and the tip is only a couple of millimeters in diameter. "When a female and a male dolphin are confined in a relatively small area in captivity, the courting behavior is rather violent. If they are isolated with a movable barrier between them, they will resolve all kinds of problems in order to be together, e.g., opening a gate to gain access to another pool and closing it behind them. As soon as they are together they start pursuit games. The initial phases of this behavior appear violent and can continue for the first 24 hours. If the female is not receptive, the male continues to chase her, exhibits erections, rubs against her, and tries to induce her to accept him. They bite one another, they scratch each other's bodies with their teeth. During the mating procedure; they will develop lesions practically everywhere on their bodies specifically on the flippers, on the back, on the flukes, on the peduncle, and around the head region. "The erection in the male occurs with extreme rapidity. We have observed and timed it in our own tanks: it is something m the order of three seconds to completion, from the time the penis first appears in the slit. It can collapse almost as rapidly, and it looks almost as if it were being done in a voluntary fashion. It is very easy to condition a dolphin to have an erection. The stimulus, for example, can be a single visual signal. One trainer chose to raise his arm vertically as a signal, and the dolphin would turn over and erect his penis in response. If Elvar, one of our dolphins, is alone and a small ring, about a foot in diameter and an inch thick, is tossed into the water, he will have an erection, with his penis lift it off the bottom and tow it around the tank." excerpts from: Lilly, John C. 1966. "Sexual Behavior of the Bottlenose Dolphin." Brain and Behavior, Volume III. The Brain and Gonadal Function. R. A. Gorski and R. E. Whalens, Editors. UCLA Forum on Medical Science, University of California Press, Los Angeles, California. P. 72-76.