Born in 1910 to a family of staunch Presbyterians in Westfield, New Jersey, Jean Clark Dan graduated from Wilson College in Pennsylvania in 1932 where she studied biology.
[1] She pursued her graduate studies in invertebrate zoology at the University of Pennsylvania and spent her summers at the Marine Biological Laboratory in Woods Hole, Massachusetts.
At the Marine Biological Laboratory she met her future husband and scientific collaborator Katsuma Dan, the son of a prominent Japanese statesman.
[2] Jean and Katsuma then moved to Japan where they continued their research at the Misaki Marine Biological Station of Tokyo University.
[5] By combining these two types of microscopy along with electron photography Jean was able to make and document detailed qualitative observations about the process of fertilization in invertebrates.
Writing in her obituary for Nature, Arthur L. Colwin and Laura Hunter Colwin, who like Katsuma and Jean were a husband-wife team of embryonic researchers, described Jean on a personal level as a “warm and vital” woman, “a strong swimmer”, a fan of wild mushrooms and sweet potatoes, the owner of a dog and a “whole family of Siamese cats”, an enthusiastic idealist and educator, and the type of scientist who would decorate her laboratory with a flower in a beaker.