His work with sex linked traits in fruit flys Drosophila suggested that chromosomes contained genes. Later Nettie Maria Stephens was able to prove this hypothesis by examining the chromosomes of the fruit flys. Bridges wrote a couple of papers presenting the proof. He thanked her as "Miss Stevens" without stating what her contribution was nor referring to her PhD.
He died on December 27 1938. Reports differ as to whether this was due to syphilis, or to heart failure as a complication of a heart valve infection.