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.
Economic historians usually attribute the start of the Great Depression to the sudden devastating collapse of US stock market prices on October 29, 1929, known as Black Tuesday; some dispute this conclusion, and see the stock crash as a symptom, rather than a cause, of the Great Depression.