Vito Volterra (1860-1940), an Italian mathematician who strongly influenced the modern development of calculus, played also a decisive and widely acknowledged role in the developments of theoretical biology. This volume presents the correspondence between Volterra, an Italian mathematician, and numerous scientists in the field of theoretical biology, accompanied with an introductory essay by Ana Millan Gasca, which presents a general survey of the research in the field of mathematical biology in the first decades of the twentieth century. The correspondence contains the transcripts of 425 letters of 19 scientists, published in the original language (french, italian, english). Each correspondence is presented by a biographical profile of the correspondent and accompanied by notes containing information and references to facilitate understanding. The modern developments in mathematical biology took place roughly between 1920 and 1940, a period now referred to as the Golden Age of Theoretical Biology . The eminent Italian mathematician Vito Volterra played a decisive and widely acknowledged role in these developments. Volterra’s specific project was to transfer the model and the concepts of classical mechanics to biology, constructing a sort of rational mechanics and an analytic mechanics of biological associations. The new subject was thus to be equipped with a solid experimental or at least empirical basis, also in this case following the tried and tested example of mathematical physics. Although very few specific features of this reductionist programme have actually survived, Volterra’s contribution was decisive, as is now universally acknowledged, in encouraging fresh studies in the field of mathematical biology. Even today, the primary reference in the literature of the field of population dynamics consists of Volterra’s work and the descriptive schemata (the models , in modern parlance) he proposed. The present book aims to fill this historiographic gap by providing an exhaustive collection of the correspondence between Volterra and numerous other scientists on the topic of mathematical biology. The book begins with an introductory essay by Ana Millan Gasca, which aims at giving a picture of the research field of biomathematics in the Golden Age , and shows the importance of the correspondence in this context. This is followed by a transcript of the correspondence ordered by the correspondent’s name. Each item is preceded by a biographical profile of the correspondent and accompanied by notes containing information and references to facilitate understanding. The book will be found useful not only by science historians but also by all those - in particular, biomathematicians and biologists - with an interest in the origins of and events in a branch of learning that has undergone an astonishing development. Many of the problems discussed - in particular that of empirical verification - appear extremely topical even today and in some cases could even fuel reflection on topics still open to research.