catfish: any of numerous mostly freshwater bottom-living fishes of Eurasia and North America with barbels like whiskers around the mouth
soft-finned fish: any fish of the superorder Malacopterygii
michelson-morley experiment: a celebrated experiment conducted by Albert Michelson and Edward Morley; their failure to detect any influence of the earth's motion on the velocity of light was the starting point for Einstein's theory of relativity