All jellyfish are Cnidaria, an animal phylum that contains jellies, sea anemones, and corals, among others. There are more than 10,000 species of Cnidaria, and less than 4,000 of these are Medusazoa—those animals we think of as jellyfish. Those 4,000 jellyfish can be divided into four different groups.
In 1882 Edison helped form the Edison Electric Illuminating Company of New York, which brought electric light to parts of Manhattan. But progress was slow. Most Americans still lit their homes with gas light and candles for another fifty years. Only in 1925 did half of all homes in the U.S. have electric power.