This thesis explores the use of biological analogies in the works of three German economists of the late 19th and early 20th centuries. Albert Schäffle (1831-1903), Werner Sombart (1863-1941), and Ernst Wagemann (1884-1956) stand out among their contemporaries for explicitly introducing concepts, images, principles, and theories from biology into their economics. The three economists borrowed the concept of tissues, images of the nervous system and the blood circuit, principles of development, and theories of cell metabolism from popular zoologists, physicians, and neurologists of their time. Their borrowings were heavily criticized by their fellow economists and were largely dismissed as unscientific by historians of economics. This thesis challenges these verdicts and argues for a central epistemological value of biological analogies in the works of the three economists. The main claim of the thesis is that Schäffle, Sombart, and Wagemann introduced biological analogies because they were unable to represent the variety (Mannigfaltigkeit) of the economy with the existing theoretical framework. In a world where most economists sought unity in variety, Schäffle, Sombart, and Wagemann were looking for variety in unity. In their pursuit to represent variety in unity, the three economists used biological analogies as tools to create systems, schemas, and networks. With these novel creations, they were able to conserve in their theory the variety of commodities, collectives, firms, and branches and investigate their interplay. By conserving variety, they shaped an alternative or ‘conservative’ style of thought in economics. This style is missing in neoclassical economic theory but still resonates with recent heterodox approaches.