Explain the evolution of female characters in movies during the 1930s and 1940s and explain why you think this?

1. From Lady Lou in She Done Him Wrong to Phyllis Dietrichson in Double Indemnity, we have encountered a remarkable diversity of leading female roles in Hollywood during the 1930s and early 1940s. Using at least three films from the group including the two above and Duck Soup, The Public Enemy, Mr. Smith, The Philadelphia Story, and Casablanca, identify a pattern in the evolution of female characters during this period and explain why you think this pattern developed.