The shingled girl: Catherine Janet Hill and her contributions to embryology.

Catherine J. Hill is best remembered for her dedication to cataloguing the comprehensive embryological collection of her father J. P. Hill. Yet, her own research, during the interwar years, is little known. She made a significant contribution to interpreting the autonomic innervation of the gut, work that was presented to The Royal Society and earned her a PhD. Working in her father's laboratory, she then set about solving the sequence of secretions from the tubal epithelium and uterine glands that contributed the two layers of egg albumen and three shell layers of the monotreme egg. She was also the first to understand twinning in the marmoset and how two embryos came to share a single extraembryonic coelom, work that often is credited to J. P. Hill. Here. I explain how that happened and explore the context in which she and other female scientists worked at the time.