Light in darkness is a powerful metaphor, and the production of light by living creatures has proved a fascinating subject across the span of recorded knowledge. For many outside the field, interest in current work was sparked most recently by Edith Widder's communicative videos documenting discoveries from the deep oceans over the last decade. Written from the point of view of an active researcher in the field, Michel Anctil's detailed and engaging book takes an essentially chronological approach to the gradual revelation of the biochemical processes underlying the phenomenon of bioluminescence. In some respects, as he notes early in the book, changes in the understanding of these processes parallel the emergence of biochemistry as a discipline, together with the concepts of enzymatic action. The later chapters of the book contain detailed and occasionally intensely personal anecdotes of the human beings whose lives and intellects were dedicated to this field of study. This is the author's second book telling the story of his own investigative fields: the first, The Dawn of the Newon, appeared in 2015.

The book documents the changing research questions, from the description of phenomena to the investigation of their generation and biological role. For the historian of science, this aspect of the book has an additional value. Although the approach tends to be selective of those questions which produced ‘successful’ results, it does illustrate a process of change in a well-defined area, traversing centuries of scientific thought and supported by a detailed bibliography. It also illustrates the motivations, personal and emotional, of those who pursued these research questions with method, creativity and wonder.

For the ancients, the distinction between organic and inorganic production of light became part of the approach to the understanding of light as a phenomenon. Light was often associated with heat, as in the light of the sun, or of a flame, but moonlight, starlight, the light from shining creatures, and the light associated with putrefaction were distinguished as cold. Approaching these issues, Anctil writes at the outset that he is coming to the topic as a long-term investigator of bioluminescence with a modern scientific background. In contrast to much recent historiography of science, he refers to superstition, religiosity and fantasy as characteristic of the earlier writings. The sixteenth and seventeenth centuries merit an intentionally brief survey, picking out those findings which in the author's estimation contributed with a certain degree of directness to later developments, and referring those seeking more detail to other parts of the literature. This approach does not prevent him from engaging with detailed observations made by the Jesuit polymath Athanasius Kircher or those recorded by Robert Boyle, the latter particularly commended for his insights, or with Gesner, Aldrovandi and Bartholin, who are commended primarily for their signposts to later work. Anctil does express a degree of empathy with those early writers who wondered at the lights from living creatures (life itself, with its metaphor of animating flame, being a subject for discussion, wonder and religious devotion) or by shining organic or inorganic materials.

The Enlightenment period is a more comfortable milieu for Anctil. Chemiluminescence required air, as was evident from the work of Robert Boyle, and confirmed as a need for oxygen by Lavoisier, commended with Priestley as one of Boyle's ‘true heirs’. Bioluminescence also required a ‘combustion’ ascribed by Boyle to biological processes, but how this occurred was a matter of continuing debate. Anctil also describes the work of Réaumur and other naturalists in accumulating more and more species manifesting luminescence, leading to instances of questions about taxonomy on the one hand and comparative studies on the other.

The sense of the flood of information generated by nineteenth-century naturalists of all stripes is given well by Anctil, whether it is what he describes as ‘slosh-and-slop’ methodology or something more rigorous. His engaging style makes his accounts of ocean voyages, recording ever more luminescent marine organisms, a pleasure to read. As well as detailed accounts of the discoveries, he includes telling glimpses of the personalities of the investigators and the social tensions arising on these lengthy oceanic circumnavigations. The later and more systematic voyages, with onboard laboratories, and the endeavours of the researchers on both sides of the Atlantic to leverage political support for their work, are described with increasing use of the illustrations which brought discoveries into the public eye.

Subsequent parts of the book focus on those individual scientists who worked both on deep-water species displaying luminescence and on those from other habitats and genera. The dynamic of the groups that surrounded the leading personalities and the discoveries of the biochemical mechanisms within the varying organs are detailed in each case. The sense of intellectual inheritance, and the conflicts and synergies established by the research groups, are evident throughout. Prominent among the individuals described is the American E. Newton Harvey, author of the only previous book-length account of the history of the subject. Harvey's students at Princeton established a laboratory which became central to the development of biochemical studies of bioluminescence and of its evolution. The branching nature of the disciplinary history of biochemistry, molecular biology and genetics can all be illuminated by the details of their application and stimulation through investigation of the phenomenon of bioluminescence.

The basis of bioluminescence has been reviewed comprehensively many times as additional data and hypotheses came to light, and Anctil includes many of these reviews in his extensive bibliography. It is clear from Anctil's account that many important concepts were clarified in the ‘cold light’ of bioluminescence. The most recent of these is the phenomenon of ‘quorum sensing’, in which gene expression fluctuates as a function of population density. This is still imperfectly understood and the subject of active investigations. In addition, the ‘usefulness’ of the study of bioluminescence has been demonstrated in the assays yielded for medicine and research using the luciferin/luciferase reaction (over two thousand cited in a recent search).

The story of the ‘cold light’ of bioluminescence is told by Anctil with the warmth of personal involvement. His account of the changing face of the field, while focusing on the successful, does not omit the dead ends, errors and failed experiments which characterize all research, and offers valuable insights into the processes behind the publications and success stories. For the historian of science with an eye to current historiographical method, some sifting of the approach is necessary. For this biochemist-turned-early-modernist, a little more on the earlier period would have been welcome. But the particular value of this book is in the detail of the accounts, the prevailing sense of wonder, and the delight and curiosity of the human intellects engaged in understanding the lights in the darkness.