This study involved a comparative analysis of reforms in the organization and structure of curricula and instruction in science education in the United States during the last decades of the nineteenth and twentieth centuries. A review of literature of these periods revealed similar concerns and goals for science instructional reform in schools. With the use of primary and secondary sources from these decades, a comparison of the conditions surrounding the reform movements was made. The author explored such concerns as educational norms, aims, values, customs, curricula content, instructional methods, psychological bases and their relationships with the technological and scientific cultures of the times. This comparison characterized common factors associated with the two reform movements. A historical characterization of the two reform periods identified relationships and responses of science education reform to social, educational, scientific, technological, and economic influences. These relationships and responses represent some of the common factors that late-nineteenth century and late-twentieth century reform movements in science education share. The author determined that although the terms, phrases, and jargon used by late-nineteenth century science education reformers sound similar to those used today, the reform efforts are not as similar as they seem. Different meanings of reform terminology used by educators of the two time periods resulted in science education means and goals that are distinct for each period, although the terminology used to describe these ideals sounds and appears very similar. This study shows how science education reforms in the late-nineteenth and late-twentieth centuries responded to the world of which they were a part, and how under apparent similar conditions, responses of reformers appear similar, but in reality are different. / Ph. D.