The biologist who studies heredity is very much like a mathematician who is studying a very complex function with the aid of partial differential equations and who tries to analyze the properties and the function about a point without being able as in the case of an elementary function to study it in itself, directly in all its respects.

Annual Report of the Board of Regents of the Smithsonian Institution, (1916), The Present State of the Problem of Evolution (p. 330)