Returning to study after teaching
After years of teaching, Stevens enrolled at Stanford, earning a bachelor’s degree in 1899 and a master’s in 1900. She completed her doctorate at Bryn Mawr in 1903. Training in histology and cytology led her toward germ cells and heredity, with further experience at marine laboratories and in Europe.
Chromosome evidence from mealworms
In mealworms, Stevens identified a large and a small chromosome in the male complement and compared sperm types with female cells. She connected differences in offspring sex with chromosome combinations. This supplied cellular evidence alongside contemporary explanations that emphasized external conditions such as nutrition and temperature.
Carnegie funding and the 1905 report
Carnegie awarded Stevens $1,000 in 1904 and renewed the grant the following year. It published her 1905 Studies in Spermatogenesis with Especial Reference to the Accessory Chromosome. Edmund Beecher Wilson’s independent research that year also supported a chromosome–sex connection; Stevens independently developed and interpreted her evidence.
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Continuing comparisons among insects
Stevens became an associate in experimental morphology at Bryn Mawr in 1905 and continued studying insect germ cells. Her research career ended with her death in 1912. Comparative observations of chromosome numbers and forms made these structures concrete evidence for investigating hereditary phenomena.