Rachel Carson
After her first year of graduate school, Carson worked in a laboratory with rats and Drosophila, to earn money for tuition.  She wrote her dissertation for her master's degree on how the pronephros in fish developed early in their life.  She earned a master's degree in zoology in June 1932.  She wanted to continue for a doctorate, but in 1934 Carson had to leave Johns Hopkins to find a full-time teaching job to help support her family.  In 1935, her father died suddenly, and Carson had to take care of her aging mother.  This made the money problem even bigger (this was during the Great Depression, when jobs were hard to find).