Later Victorian Yorkshire was home to a vigorous community of life science practitioners. In studying them, I reassess three dichotomies familiar to the contextualist historian of Victorian science: field and laboratory, science and society, and amateur and professional. I outline the refashioning of amateur and professional roles in life science, and I provide a revised historiography for the relationship between amateurs and professionals in this area and era. While exploring these issues, I examine the complex net of cultural and educational institutions where the sites for the practice of life science emerged and existed. Natural history practices shaded imperceptibly into other facets of civic culture. I present natural history as a leisure activity and as a resource utilised by the maturing provincial middle classes, one of a range of cultural activities within a network of voluntary associations. This thesis is arranged by institution: philosophical society, museum, civic college and field club. Each of these corresponds, loosely, to a site for science: respectively, lecture hall, museum, laboratory and field. The traditional `field versus lab' historiography ignores the many and varied sites for life science in this era, and conceals how far field-based natural history endured alongside the laboratory as it emerged as the hegemonic site for life science. I explore these and other issues by using the career of Louis C. Miall (1842-1921) as a narrative thread. Despite his activities as a lecturer, curator, field club president and laboratory biologist, Mall sought to construct a professional identity based solely on the authority of the laboratory, in contrast to that of the amateur naturalist. To take his partisan rhetoric at face value, however, is to ignore the variety and vitality of life science practices in Victorian Yorkshire.