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.
There are various explanations for the causes of the great depression that started in 1929. Some of the most likely causes are given below: 1. OVER-PRODUCTION AND OVER-EXPANSION.