Dictionary of Ichthyology  

jellied eels = pieces or steaks of eels cooked in brine or vinegar and salt with vegetables and seasonings and then packed in gelatin. Sometimes the fat or gelatin from the eel itself is sufficient to form the jelly. Eaten hot or cold and formerly a staple food for the poor in London. See also coller an eel.

Wikimedia Commons: http://commons.wikimedia.org/wiki/File:Eels_1385.JPG

Canadian Museum of Nature