Blue whale penis
The blue whale has the largest penis in the animal kingdom. It is commonly cited as having an average penis length of to and a diameter of to . Morphology. The reported average penis length varies but is usually mentioned to have an average length of . The most common reported average length is roughly but the average diameter is only , making the penis proportionately very long and thin. However, its girth has also been reported to be nearer , with a single ejaculation estimated to be about , based on the size of its testes each weighing . "Average" for a  blue whale penis, however, is difficult to gauge given that the penis is unlikely to be able to be measured during sexual intercourse. The penis of the blue whale is normally hidden inside its body and jets out through a genital slit during intercourse. They are stated to be tough and fibrous (more than in any other mammal). It is believed that it uses the elasticity of this tissue to get an erection and not from any blood flow, though this hypothesis has not been confirmed by any scientific study. Scientific studies. With whales, the length of the penis can  be an indication of the maturity of the organism. Sei whales for instance are divided into categories such as immature, pubertal and mature. However, length is not the only factor as it is recorded in relation to the size of the whale's testes and its histology. For instance, research conducted off South Africa found that the longest penis of an immature categorized whale was and the smallest penis of a mature whale was . By comparison the average blue whale penis is nearly 3 times the size of that of a sei whale. Specimen measurements indicate that a blue whale  measuring in length had a vestigial mammary slit of width and length, with a penis measurement of . In another specimen in which the length of the whale was and weighed 50.9 metric tons, the brain weighed only . Largest specimen. The Icelandic Phallological Museum has a portion of a blue whale's penis measuring long and weighing , which "Iceland Review" has dubbed "a real Moby Dick". The specimen is just the tip, as the entire organ, when intact, would have been about long and weighed about , well above average for even a blue whale. By comparison, an adult elephant's penis  is the largest penis of any land animal at on average.