GFP identified as protein, extracted from 10,000 jellyfish – “a protein giving solutions that look slightly greenish in sunlight though only yellowish under tungsten lights, and exhibiting a very bright, greenish fluorescence in the ultraviolet of a Mineralite, has also been isolated from squeezates.” Called “green protein.”

Reference: O Shimomura, FH Johnson, Y Saiga: Extraction, purification and properties of aequorin, a bioluminescent protein from the luminous hydromedusan, Aequorea. J. Cell. Comp. Physiol. 59 (1962) 223-29.