The delectable freshwater eel, or unagi in Japanese, has long been a mysterious morsel. As far back as ancient Greece, people have wondered where eels come from because nobody had ever seen their eggs or larvae.
Clockwise from top left: An eel with huge eyes for long-distance spawning migration; Japanese eel; and two species of eels that live in the deep ocean.
© Courtesy of Michael J. Miller
Aristotle, studying the European eel more than 2,000 years ago, concluded that eels were born from the mud because they did not have full-fledged testes or ovaries. Spontaneous generation was repudiated long ago, but given the knowledge level of his time, Aristotle's explanation is remarkable for his use of scientific deduction.
