 The developments in genetics sketched in Part 1 prompted the question how philosophical models of scientific change could be applied to the case of biology from the late nineteenth century to the present, as they had been developed mainly based on cases from modern physics and chemistry and preceding traditions in natural philosophy. Were the major transitions in hereditary thought to be described as scientific revolutions (see entries on  scientific revolutions  and  the incommensurability of scientific theories)?  It seems that models of change emphasizing discontinuity and incommensurability among successive paradigms, such as Thomas Kuhn’s (1962), do not fit well with what can be observed in the history of genetics: Much terminology and many practices seem to remain intact despite constant theoretical novelty, and the developments do not appear to be perceived as discontinuous in a strong sense by the protagonists. Continuous models of change, developed earlier by logical empiricists and centered on the notion of reduction as a relation between earlier and later theories, were thus discussed as possible alternatives with respect to the history of genetics.