Cnidaria is a phylum within Kingdom Animalia which consists of hydras, jellies (or jellyfish), sea anemones, and corals. All cnidarians are radially symmetrical, and there are two main radially symmetrical body types.
The stock market crash, on black Tuesday (October 29, 1929) began the Great Depression.
Thus began the worldwide Great Depression. The onset of the contraction led to the end of the stockmarket boom and the crash in late October 1929. However, the stock market collapse did not cause the depression; nor can it explain the extraordinary length and depth of the American contraction.