Career
In the latter year Johann Jakob Heckel published the livebearing freshwater Green swordtail (Xiphophorus helleri), since the early 20th century a common aquarium fish, from specimens Heller deposited in Vienna. Born in Moravia, Heller was a professor at the Theresianum in Vienna. Among Heller"s later works is his defense of Darwinism, Darwin und der Darwinismus, 1869.