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.
Causes of the Great Depression of 1929-1939. There is no single cause or obvious set of factors that can explain why the. depression occurred. Historians, economists and political scientists have come. up with various explanations that place different emphasis on different factors.