Nettie Marie Stevens is shown here looking through a microscope while studying at the Stazione Zoologica in Naples, Italy, in 1909. In 1904, soon after getting her Ph.D. in biology, Stevens was awarded a grant from Carnegie Science. Her 1905 paper “Studies in Spermatogenesis with Especial Reference to the Accessory Chromosome” produced some of the first work offering cytological evidence demonstrating that the X and Y chromosomes were associated with sex determination. Image Courtesy Bryn Mawr College Special Collections.
