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.
Biological depression is thought to be triggered by changes in the body with no contribution from external events. Periods of stress or trauma â a result of events such as losing a job or a loved one â are the most commonly cited triggers for the onset of depression in individuals.