Karl Bogislaus Reichert (1811-1883)
Crucial to our understanding of the evolution of mammals is the origin of the bones of the inner ear from what were elements of the jaw articulation in reptiles. This was worked out in 1837 by the German embryologist Karl Bogislaus Reichert. Zofia Kielan-Jaworowska (previous post) notes this is all the more remarkable in view of the primitive tools available at the time. Later Ernst Gaupp built on this work and the supposed origin of the inner ear bones is known as the Reichert-Gaupp theory.
Reichert's membrane (Rm) in the placenta of the capybara
From Kanashiro et al. Reprod Biol Endocrinol 2009; 7: 57 (here)
Students of the placenta will be more familiar with the name of Reichert through the eponymous membrane that lies between the trophoblast and the endoderm of the parietal yolk sac in rodents and insectivores. It was first described by Reichert in the guinea pig (Abh Akad Wissensch Berlin 1862; pp. 97-216).