Toothed whale brain size with the expected brain size based on such allometric analysis provides an encephalisation quotient that can be used as another indication of animal intelligence. Sperm whales have the largest brain mass of any animal on earth, averaging and in mature males, in comparison to the average human brain which averages in mature males. The brain to body mass ratio in some odontocetes, such as belugas and narwhals, is second only to humans. Dolphins are known to engage in complex play behaviour, which includes such things as producing stable underwater toroidal air-core vortex rings or "bubble rings". Two main
The Brain of Morbius the ruins. Morbius attacks the Doctor, but is knocked out by Solon's tranquilliser. As they carry the creature back to the castle, the Doctor tells Solon that Morbius's brain will be detached and returned to the Time Lords. The body of the dead Sister is brought back to Maren. Ohica reports that witnesses saw a creature and then the Doctor and Solon hunting for it. Maren realises that Solon has succeeded in his experiments and resurrected their ancient enemy. But Maren is too old and weak to leave the shrine, and she gives Ohica permission to lead the Sisters to