Mendelian Heredity
57 objects illustrate this topic:

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"Probably Mendelian" and "Clearly Hereditary" traits (#994)
Raymond Pearl letter to Karl Pearson, about disagreement on hereditary theory and his removal as an editor of Biometrika (2/15/1910), multiple pages (#2130)
Raymond Pearl letter to Karl Pearson, discussion of conflict between biometrical and experimental approaches to study heredity (3/12/1910), multiple pages (#2133)
Sex-linked traits (#993)
Sketch of Carl Correns, Kaiser-Wilhelm Institute for Plant Breeding, one of the rediscovers of Mendel's work (#2262)
"Student Pedigree-Studies," (mechanical ability, by Margaret C. Mount; eye color, by Morris Steggerda), multiple pages (#1894)
"Taste Thresholds," Albert Blakeslee PTC tasting exhibit, 3rd International Eugenics Conference (#1076)
"The general formula of heredity", multiple pages (#945)
"The Inheritance of Mental Traits," from Evolution and Genetics, by Thomas H. Morgan, an early criticism of eugenics in an important text, multiple pages (#1917)
"The New Decalogue of Science," by Albert Edward Wiggam, multiple pages (#1349)
"Theory of Ancestral Contributions in Heredity," handwritten manuscript by Karl Pearson, published in Proceedings of the Royal Society (vol. 81:547), multiple pages (#1970)