Bateson's work published before 1900 systematically studied the structural variation displayed by living organisms and the light this might shed on the mechanism of biological evolution, and was strongly influenced by both Charles Darwin's approach to the collection of comprehensive examples, and Francis Galton's quantitative ("biometric") methods. In his first significant contribution, he shows that some biological characteristics (such as the length of forceps in earwigs) are not distributed continuously, with a normal distribution, but discontinuously (or "dimorphically"). He saw the persistence of two forms in one population as a challenge to the then current conceptions of the mechanism of heredity, and says "The question may be asked, does the dimorphism of which cases have now been given represent the beginning of a division into two species?”