23、A dolphin（海豚）is always well-known as a clever and friendly animal. Recently another amazing（令人惊奇的） discovery made by the British marine（海洋的）biologist (生物学家) Alexis shows that dolphins, to our surprise, keep in touch with each other by calling each other's names among themselves something like human beings.
Alexis recorded over 1700 different kinds of dolphins' calls and made a careful analysis of them. The analysis shows each dolphin has his own sound signal referring specially to himself and used all the time when he gets in touch with others. What's more, one dolphin is even able to imitate another's cry in more or less the same way as sometimes human beings do while talking with birds, which is believed to be an important step towards language from animals' calls.