The essay-periodical and the novel both emerged as new literary genres in the eighteenth century. Yet there has been no full-length study of the formative role each genre played in the development of the other. This book uses the lens of periodical studies to reassess what we know about the history of prose fiction, examining how periodicals shaped fictionality and how they were influenced by it in return. It moves the dial on studies of the English novel, arguing that the vibrant interchange between these genres revolutionised the printed world. Over five chapters that contextualise key authors within London's cutthroat print marketplace, the book studies the idea of 'print ecologies' to explain the mutual dependence of the periodical and prose fiction, disrupting the often-held assumption that the novel emerges from this period sui generis.