During the early 1870s a young zoologist who worked as a Privatdozent delivering lectures at different Prussian universities invested much of his family wealth and solicited his fellows' contributions to establish a research facility by the sea. The young zoologist happened to be called Anton Dohrn. From the time it opened its doors, the Anton Dohrn Zoological Station – or Naples Zoological Station, as it was originally called – played a crucial role in shaping life sciences as it facilitated research aimed at explaining the mechanics of inheritance. During the last quarter of the nineteenth century and the first decades of the twentieth, zoologists attempted to explain how evolutionary changes occur within a population and become stabilized. In so doing, they looked at developmental processes as well as environmental pressure, coming up with different hypotheses to explain inheritance. In some cases, their research was highly speculative, whereas in other cases they conducted cytological observations to identify the material basis of heredity. Research on evolution and development has been carried out in different places, and zoological stations like the one in Naples have played a major role in this story. However, numerous biological institutions active at the turn of the twentieth century have not received much attention from historians.

In the early twentieth century, American botanist Luther Burbank claimed that heredity is nothing else than stored environment. His claim evokes the key concepts of the books herein discussed: heredity and environment. This essay will also stress a concept in the claim: how the environment is stored in heredity, a process happening through development and evolution. In this narrative, heredity is a theoretical storage in which different concepts – namely evolution, development and environment – finally come together in a conclusive way. This essay discusses three books that have recently been published and that focus on three different aspects of the same story. De Bont's Stations in the Field illustrates in a nice cross-cutting way the places where most of this research was conducted; Hopwood's Haeckel's Embryos analyses the images Ernst Haeckel utilized to explain development and evolution; and Churchill's August Weismann is a biographical history of the concept of heredity, in which all pieces – evolution, development and environment – come together in Weismann's intellectual life. Although the books are heterogeneous in terms of their epistemic objects, the stories herein discussed occurred during the same time period and therefore share the same historical background.

In his book, published in 2015 by the University of Chicago Press, historian of ecology Raf de Bont reframes our understanding of biological stations, which have generally been described as places where scientists researched evolution and development, thus investigating inheritance in different ways. De Bont steps away from literature that has addressed the rise of laboratories to focus instead on the institutions that ‘provide researchers with their own scientific habitat, within the larger habitat of the organisms they study. Thus, they facilitate biologists both going outdoors and bringing organisms indoors’ (p. 2–3).

At the beginning of his book, de Bont makes it clear that biological stations are not a homogeneous group of institutions and, therefore, do not share common features. In particular, de Bont identifies a dichotomy between institutions that acted like standard laboratories with the exception that they were conveniently located by the sea to easily supply researchers with fresh organisms – as was the case of the Naples Zoological Station – and institutions that functioned as actual field stations where scientists could conduct fieldwork and thus research organisms in their natural habitats. De Bont engages his dichotomy further and describes the former institutions as focusing on artificial objects, and the latter as dealing with more genuine natural objects. In this narrative, laboratories appear to be institutions where research happens indoors in well-equipped facilities, whilst field stations are described as less organized places that act like a base for scientists' outdoor investigations.

De Bont's main case study is a station located in Wimereux, France, established in 1874 by Alfred Giard. Although research carried out at Wimereux focused on different themes, including morphology and evolutionary theory, de Bont stresses that animals' habits and conditions of life ‘became one of the focal points of scientific activities in Wimereux’ (p. 71). This focus on ecology is especially interesting because the Naples Zoological Station was originally aimed at the same scope, but historical scholarship on biological institutions has shown that in fact over time the Naples station became more and more focused on developmental processes, dismissing environmental factors. Therefore the Wimereux station appears quite peculiar in de Bont's story, as it constitutes a place for scientists to investigate marine organisms in their natural habitat as well as the multiple ways they interact with the environment.

The Wimereux station also constitutes a unique place due to its location close to a small river, which makes the nearby waters brackish and therefore worth investigating for their special biodiversity. According to de Bont's analysis, ecology and biodiversity have made the Wimereux station a unique research institution, one whose features do not overlap with the research focuses that have been widely described as typical of the major biological stations such as the Naples Zoological Station and the Marine Biological Laboratory in Woods Hole, Massachusetts.

Additionally, de Bont discusses the case of the Wimereux station in the context of the differences between French and German academic systems. In particular, de Bont notes that the Naples Zoological Station, a German station on the Italian coast, was established as a private institution where researchers could travel to conduct experiments, and that those researchers were usually not fully part of the German academic system in that they did not take part in decision-making processes. Those researchers were, in most cases, Privatdozenten (an academic position similar to temporary adjunct faculty positions in the current UK and US academic systems), and rarely had any chance to move up in the hierarchy. Thus the opportunity of working in private institutions was to German researchers a way to experience freedom in research, as well as a convenient way to boost their careers. In contrast, French stations were established as branches of major French universities to provide their academics with facilities to conduct fieldwork. As such, French stations were not independent institutions, but acted as satellites of major universities hosting their faculty members and students for educational and fieldwork purposes.

The rise of German biological stations happened in similar ways across Europe: those stations were established thanks to private efforts and funding, and they were generally located on territories that were not German, which gave them an international appeal. Additionally, German researchers engaged in the scientific community more widely than did their French colleagues, and their newer institutions attracted scientists from different countries.

De Bont's book addresses a very specific group of historians who are interested in biological stations, who have previously engaged with the existing literature. Those historians will find a nice unexplored perspective on biological stations, which sheds light on themes that have often been disregarded. In the book, the argument is not clearly stated. Overall, de Bont seems to claim that the way scholarship has generally addressed such institutions, describing them as mainly committed to experimentation, is not quite accurate. In de Bont's narrative, the Wimereux station plays a crucial role, with its peculiar features and its ecological scope, in showing that in fact there existed stations that served as mere facilities where professors could educate students in the field.

De Bont's book is rich with historical details about the rise of biological stations in Europe. Given such an enjoyable richness in historical detail, it is quite surprising that de Bont reiterates some inaccuracies throughout his book. In particular, in multiple instances de Bont mentions Otto Hermes, the director of the Berlin aquarium in 1870, and claims that Hermes ‘established a station in Trieste, which mainly served for the collection and shipment of specimens to Berlin’ (pp. 24–25). Archival evidence, along with primary and secondary literature, shows that Hermes indeed established a zoological station by the sea, but not in Trieste. The station that served the Berlin aquarium was instead located in Rovigno, a city that then belonged to Italy, whereas the Trieste Zoological Station was an Austro-Hungarian institution located on imperial territories to serve the universities of Vienna and Graz. Notwithstanding the inaccuracy, de Bont's book is undoubtedly worth reading, as it proposes a novel historical interpretation of the phenomenon of zoological stations by looking at institutions whose scopes had long been ignored.

Haeckel's Embryos relates to De Bont's book in that Ernst Haeckel is generally acknowledged as being more or less directly responsible for the rise of zoological stations in Europe. Haeckel is often reported as the initiator of the phenomenon of zoological stations in that during his trip to Messina, Italy, he discussed with his friend the idea of establishing actual stations where scientists could stop by while travelling for research purposes. Haeckel envisioned the stations to be located by the sea, so that scientists could get fresh marine organisms for their investigations. In Haeckel's idea the stations would act as facilities to accommodate scientists by providing them with working tables and various materials. In addition to his contribution to the phenomenon of zoological stations, Haeckel helped shape research on heredity by looking at embryos from an evolutionary perspective.

Historian of biology Nick Hopwood published his book in 2015 with the University of Chicago Press, and included numerous delightful images. The great number of images should not surprise the reader, though, as the entire book is about images. At the beginning of the book, Hopwood recalls an embryological anecdote that Charles Darwin mentions in the Origin of Species (1859), in which embryologist Karl Ernst von Baer stated that he had two small embryos but, after neglecting to note their names, he could not determine any more to which class each of the embryos belonged. Such episodes have played crucial roles in bringing embryology closer to evolutionary theory, and historians of science have paid much attention to the anecdote for multiple reasons that Hopwood discusses in his book. The claim implied in such an anecdote reached an enormous audience over the years after Haeckel published his embryological diagrams in 1868. Those diagrams eventually populated all science textbooks regardless of the different theories they accompanied. Notwithstanding various differences across their different editions, the diagrams represented a series of developing embryos that belonged to different species, and showed that in their early developmental stages, all embryos look very much alike and it is not until later that they acquire the traits of the different species to which they belong.

Throughout his book, Hopwood investigates what arguments Haeckel was able to make by utilizing those diagrams. Hence there are at least two levels of interpretation. First, Haeckel used his diagrams to sustain his thesis that development could be used to demonstrate evolution and that ontogeny, or the developing embryo, recapitulates phylogeny, or evolutionary history. With his diagrams, Haeckel was able to establish a relationship between development and evolution. Additionally, those diagrams played an even more decisive role than just facilitating a theoretical statement: ‘Haeckel sought confrontation by having the illustrations express the most provocative claims’ (p. 85). What were these provocative claims? Haeckel was the German advocate of the evolutionary theory, and his book reached large audiences at a time when evolution was far from being widely accepted. Thus Haeckel's diagrams served a dual goal, in that they helped establish a causal connection between development and evolution, and they visually facilitated the understanding and the overall acceptance of the evolutionary theory. And they did so because they look appealing and very intuitive.

Hopwood next discusses the accuracy of Haeckel's diagrams and analyses the critiques that those images have received at different times. In contextualizing such critiques, Hopwood shows that Haeckel's drawings are taken partly from nature and partly from other images, thus resulting in an ideal synthesis between what eyes can see and what an evolutionist's mind sees. According to Hopwood's argument, Haeckel's diagrams did not involve a conscious fraud, but they resulted in fraud due to their author's attempt to simplify and show how developmental stages illustrated evolution.

Hopwood goes farther in his analysis and discusses the debate between Haeckel and Wilhelm His. His was one of Haeckel's strongest opponents, and had widely criticized his drawings as being inaccurate and therefore an act of forgery. Hopwood shows that His had built his embryo models out of clay and wax, and he had then dissected them. Thus His's embryo models more accurately reflected the way embryos develop and how their parts fold. Additionally, in his embryological studies His focused on how environmental forces influence embryos' growth, whereas Haeckel did not take environment into account. Thus form was looked at in an analytic fashion in His's embryology, whereas form was a synthetic result in Haeckel's embryological diagrams. Hopwood clarifies the tension in the His–Haeckel debate reporting His's words: ‘the freedoms taken are such that they serve the desired identity’ (p. 123). Although His is clearly charging Haeckel with forgery, Hopwood does a great job unpacking the two different types of reasoning and work underlying the debate.

Finally, in recovering the history of Haeckel's diagrams and assessing the role they played in spreading the evolutionary theory within and outside the scientific community, Hopwood points out that evolutionism – just like any other product, either ideal or material – targets a particular market, and Haeckel's diagrams ultimately played a decisive role in selling the evolutionary theory. It is a fact that Haeckel's diagrams continued to be used in multiple circumstances, and published in a myriad of science textbooks way after the accusation of forgery. In his book, Hopwood asks why they have remained around for so long, and he finds that the market argument helps explain the popularity of those diagrams. At different times, Haeckel's embryological diagrams have helped in the battle against creationism as they magnificently illustrate evolution through the argument that embryos of different species look much alike in their early developmental stages.

Not only does Hopwood's book address a broad audience, it also proves engaging throughout its 388 pages due to its numerous images and clarity. Additionally, the book does not appear to be too technical, but in fact is a valuable scientific contribution to the literature on Haeckel's diagrams, and a very enjoyable one.

Heredity and inheritance processes constitute a more or less explicit fil rouge that ties together the books herein reviewed. Frederick Churchill published August Weismann: Development, Heredity, and Evolution in 2015 with Harvard University Press. The book is reportedly an intellectual biography, or a historical account of Weismann's career, and it focuses on the decades between 1859, when Darwin published his Origin of Species, and 1914, when the First World War started. Churchill's choice of such a time frame clearly suggests that his book is not only the biography of a scientist, but also the biography of a concept – heredity – as it relates to development and evolution: Weismann ‘focuses his attention on how the fields of embryology, heredity, and evolution must ultimately be understood as a comprehensive whole’ (p. xi). More precisely, in Churchill's book heredity not only is a concept that relates to both development and evolution, but in fact also represents the very link between development and evolution.

In the first few chapters of his book, Churchill portrays Weismann during his childhood and early schooling, when his mother introduced him to arts and music while supporting his fascination for butterflies. It thus appears a natural consequence of such early education that Weismann soon became interested in insect development, and in particular in how larvae complete their development into their adult forms. Following this path, Weismann later built on Luis Agassiz's insect research and described imagined disks as the precursors of specific body parts in insect larvae. Such contributions show that, since his early career, Weismann had been focusing his attention on units of development.

As a young researcher, Weismann was tied in friendship to his contemporary, Ernst Haeckel, who also focused his work on development and evolution. However, Churchill illustrates how their careers diverged following the differing views on heredity that the two scientists engaged and ‘the different objects they investigated and the research approaches they selected’ (p. 63). Churchill analyses both unpublished correspondence and published material to document the way their relationship changed over the years. In particular, Churchill reports a remarkable critique that Haeckel published in 1893 against Weismann's theory of heredity. Haeckel criticized Weismann's claims that germ-plasm, which contains the units of heredity, was continuous. Additionally, Haeckel rejected Weismann's claim that in organisms soma and germ-plasm were separated.

Churchill does a great job in this book of analysing the context in which Weismann's theory of heredity became established. After discussing the relationships Weismann entertained throughout his life with his contemporaries and the institutions he visited, Churchill focuses on the very concepts that have shaped the theory of heredity, and he illustrates the history of that theory. Thus Churchill introduces the germ layers theory as well as the study of mammal eggs and the emergence of cytology, and he discusses how those theories and approaches explained heredity and how they contributed to Weismann's explanation of heredity. Then Churchill discusses the meaning and significance of the idea of continuity within Weismann's heredity framework. ‘In Weismann's mind, an understanding of heredity went far beyond an identification of the union of the nuclei in fertilization. Central to his thinking was the rise of germ cells’ (p. 303). How are germ cells different from other cells, and how are they created? Darwin's theory of pangenesis was clearly an attempt to answer such a question; however, it did not explain ‘how the germ cells were anything more than a mélange of unorganized gemmules’ (p. 303). To address this problem, Weismann argued that there must be continuity from parents' germ cells to the offspring's germ cells. In Weismann's theory, continuity was a major requirement to account for how the germ-plasm is responsible for inheritance.

Following Weismann's 1892 publication of Das Keimplasma, the germ-plasm theory underwent multiple revisions from 1900 to 1914, when Mendel's research on the hybridization of peas was rediscovered and new concepts became available to explain inheritance processes. However, Churchill shows that during those years Weismann was mainly concerned with his neo-Darwinian agenda. For this reason, Churchill claims that ‘for Weismann and Weismannians Mendel's results seemed interesting but not central to the process of heredity. Their importance increased, however, as the meaning of the chromosomes changed and the cytological understanding of reduction division deepened’ (p. 546).

Churchill's book is a rare find, in that it is valuable both to scholars of history and philosophy of science and to the general public. August Weismann is not just a biographical book as it does not simply recover Weismann's life, but it goes beyond to illustrate with historical evidence the complex and fascinating history of an idea: heredity in the context of evolution, development and environmental factors.

Over multiple decades, zoologists have devoted much of their energy to explaining what heredity is. They did so in specific institutions that facilitated research on marine organisms in different ways; using images that eventually became controversial, although highly evocative; building on previous knowledge and constructively addressing critiques. By focusing on places, images and theories, this essay has aimed at situating valuable, recently published books within a cohesive narrative that informs their significance. To us, heredity appeared to be such a narrative.

The three books herein reviewed are quite representative of a threefold historiographical trend. In particular, due to its focus on images and how images convey science, Hopwood's book seems to somehow fit in a general trend of science and media studies, although from a historical perspective. In contrast, de Bont's book appears to respond to a general renewed interest that institutions over the past few years have shown in marine biological research. Finally, Churchill's book seems to fit in the trend of exploring the history of the concept of heredity and inheritance, at a time when genetic research and genetic theories receive much funding and attention.