 Also in 1910, however, he was studying many different kinds of organisms in pursuit of explanations of heredity as well as differentiation. A white-eyed male Drosophila fly famously caught his attention, and led him to the conclusion that some inherited factors must, indeed, cause expression in the emerging organism (Morgan 1910b). It is not that Morgan changed his mind about how to do science, but rather that the evidence carried him in new directions (Maienschein 1991a).