This article recounts the story of the development of pangenesis, a principle proposed by Charles Darwin to desctibe the rules of inheritance and the source of new variation, two concepts vital to his proposal of evolution by natural selection. Historical accounts such as this are infrequently included in texts and classroom discussions hut can serve a number of useful proposes. Pangenesis was ultimately shown to be an inaccurate idea, and one of Darwin's few errors, but this account is an interesting case study to illustrate both how science itself works and a rare glimpse into Darwin's thinking and personality.