This note discusses lecture plates at the Hugo de Vries Laboratorium that may be relevant to Hugo de Vries's claim to have independently discovered Mendel's law of segregation. Dating when the plates were made is problematic.

Galton greeted Darwin's theory of pangenesis with enthusiasm, and tried to test the assumption that the hereditary particles circulate in the blood by transfusion experiments on rabbits. The failure of these experiments led him to reject this assumption, and in the 1870s he developed an alternative theory of heredity, which incorporated those parts of Darwin's theory that did not involve the transportation of hereditary particles throughout the system. He supposed that the fertilized ovum contains a large number of hereditary elements, (...) which he collectively called the "stirp," a few of which are patent, developing into particular cell types, while the rest remain latent; the latent elements can be transmitted to the next generation, while the patent elements, with rare exceptions, cannot since they have developed into cells. The problem with this theory is that it does not explain the similarity between parent and child unless there is a high correlation between latent and patent elements. Galton probably came to realize this problem during his subsequent statistical work on heredity, and he quietly dropped the idea that patent elements are not transmitted in Natural Inheritance (1889). Galton thought that brothers and sisters had identical stirps, and he attributed differences between them to variability in the choice of patent elements from the stirp, that is to say to developmental variability. He attributed the likeness of monozygotic twins to the similarity of their developmental environment. Galton's twin method was to track the life history changes of twins to see whether twins who were similar at birth diverged in dissimilar environments or whether twins who were dissimilar at birth converged in similar environments. It is quite different from the modern twin method of comparing the similarities between monozygotic and dizygotic twins, on the assumption that monozygotic twins are genetically identical whereas dizygotic twins are not. It has been argued that Galton foreshadowed Weismann's theory of the continuity of the germ-plasm, but this is only true in a weak sense. They both believed that the inheritance of acquired characters was either rare or impossible, but Galton did not forestall the essential part of Weismann's theory, that the germ-plasm of the zygote is doubled, with one part being reserved for the formation of the germ-cells. (shrink)

Efforts to bring science into early 19th century breeding practices in Central Europe, organised from Brno, the Hapsburg city in which Mendel would later turn breeding experiments into a body of timeless theory, are here considered as a significant prelude to the great discovery. During those years prior to Mendel's arrival in Brno, enlightened breeders were seeking ways to regulate the process of heredity, which they viewed as a force to be controlled. Many were specialising in sheep breeding for the (...) benefit of the local wool industry while others were showing an interest in commercial plants, especially fruit trees and vines, and later cereals. Breeders explained their problems in regulating heredity in terms of (1) climatic influences (2) disruption due to crossing (3) sports or saltations. Practical experience led them to the concepts of 'inheritance capacity' and the 'mutual elective affinity' of parents. The former was seen to differ among individuals and also among traits; the latter was proposed as a means of adding strength to heredity. The breeders came to recognise that traits might be hidden and yet transmitted as a 'potential' to future generations. They also grew to understand that heredity would be strengthened when a quality was 'fixed' within a lineage by 'pure blood relations.' Continued selection of the desired quality might then lead to 'a higher perfection.' But the ultimate 'physiological' question about breeding, 'what is inherited and how?,' found no answer. Major figures in this development included Abbot Napp, the one who asked this question and who was due to receive Mendel into the monastery in 1843, and Professor Diebl whose lectures on agriculture and natural science at the Brno Philosophical Institute Mendel would attend in 1846. Here we analyse their progress in theorizing about breeding up until about 1840. In discussing this development, we refer to certain international contacts, especially with respect to information transfer and scientific education, within the wider context of the late Enlightenment. (shrink)

Efforts to bring science into early 19th century breeding practices in Central Europe, organised from Brno, the Hapsburg city in which Mendel would later turn breeding experiments into a body of timeless theory, are here considered as a significant prelude to the great discovery. During those years prior to Mendel's arrival in Brno, enlightened breeders were seeking ways to regulate the process of heredity, which they viewed as a force to be controlled. Many were specialising in sheep breeding for the (...) benefit of the local wool industry while others were showing an interest in commercial plants, especially fruit trees and vines, and later cereals. Breeders explained their problems in regulating heredity in terms of climatic influences disruption due to crossing sports or saltations. Practical experience led them to the concepts of 'inheritance capacity' and the 'mutual elective affinity' of parents. The former was seen to differ among individuals and also among traits; the latter was proposed as a means of adding strength to heredity. The breeders came to recognise that traits might be hidden and yet transmitted as a 'potential' to future generations. They also grew to understand that heredity would be strengthened when a quality was 'fixed' within a lineage by 'pure blood relations.' Continued selection of the desired quality might then lead to 'a higher perfection.' But the ultimate 'physiological' question about breeding, 'what is inherited and how?,' found no answer. Major figures in this development included Abbot Napp, the one who asked this question and who was due to receive Mendel into the monastery in 1843, and Professor Diebl whose lectures on agriculture and natural science at the Brno Philosophical Institute Mendel would attend in 1846. Here we analyse their progress in theorizing about breeding up until about 1840. In discussing this development, we refer to certain international contacts, especially with respect to information transfer and scientific education, within the wider context of the late Enlightenment. (shrink)

Darwin's ideas on variation, heredity, and development differ significantly from twentieth-century views. First, Darwin held that environmental changes, acting either on the reproductive organs or the body, were necessary to generate variation. Second, heredity was a developmental, not a transmissional, process; variation was a change in the developmental process of change. An analysis of Darwin's elaboration and modification of these two positions from his early notebooks (1836-1844) to the last edition of the /Variation of Animals and Plants Under Domestication/ (1875) (...) complements previous Darwin scholarship on these issues. Included in this analysis is a description of the way Darwin employed the distinction between transmission and development, as well as the conceptual relationship he saw between heredity and variation. This paper is part of a larger project comparing commitments regarding variation during the latter half of the nineteenth century. (shrink)

August Weismann is famous for having argued against the inheritance of acquired characters. However, an analysis of his work indicates that Weismann always held that changes in external conditions, acting during development, were the necessary causes of variation in the hereditary material. For much of his career he held that acquired germ-plasm variation was inherited. An irony, which is in tension with much of the standard twentieth-century history of biology, thus exists – Weismann was not a Weismannian. I distinguish three (...) claims regarding the germ-plasm: (1) its continuity, (2) its morphological sequestration, and (3) its variational sequestration. With respect to changes in Weismann’s views on the cause of variation, I divide his career into four stages. For each stage I analyze his beliefs on the relative importance of changes in external conditions and sexual reproduction as causes of variation in the hereditary material. Weismann believed, and Weismannism denies, that variation, heredity, and development were deeply intertwined processes. This article is part of a larger project comparing commitments regarding variation during the latter half of the nineteenth century. (shrink)

Recent studies have shown that Hugo de Vries did not rediscover Mendel's laws independently and that the classical story of the rediscovery of Mendel is largely a myth. Until now, however, no satisfactory account has been provided of the background and development of de Vries' views on heredity and evolution. The basic tenets of de Vries' Mutationstheorie and his conception of Mendelism are still insufficiently understood. It has been suggested that de Vries failed to assimilate Mendelism and that he wrote (...) his Mutationstheorie in a state of confusion. In this paper I argue that we can arrive at a better understanding by adopting a more symmetrical approach. My analysis will concentrate on three important aspects of de Vries' thinking which have been insufficiently appreciated until now. The first is that de Vries' reading of Mendel compelled him to change his conception of the hereditary particles, the pangenes, in a fundamental way. The second is de Vries' use of the notion of ‘hereditary force’. The third revolves around de Vries' typological species concept, which has been the source of much confusion in the literature. I shall conclude that de Vries did succeed in incorporating ‘Mendelism’ into his wider views on heredity and evolution, and that he did manage to handle his evidence in a consistent way. Yet I shall also conclude that Mendelism, in de Vries' interpretation, had nothing to do with ‘normal’ heredity and was mainly a laboratory phenomenon. (shrink)

This paper aims to give an impression of how biologists, at the turn of the twentieth century, came to conceptualize and define the hidden entities presumed to govern the process of hereditary transmission. With that, the stage was set for the emergence of genetics as a biological discipline that came to dominate the life sciences of the twentieth century. The annus mirabilis of 1900, with its triple re-appreciation of Gregor Mendel’s work by the botanists Hugo de Vries, Carl Correns, and (...) Erich Tschermak, can be seen as the watershed after which theorizing about heredity and experimentation—selecting pure lines and Mendelian crossing—became tightly connected. As to concepts before this, this paper will analyze Carl von Nägeli’s ‘idioplasm’, Hugo de Vries’s ‘pangenes’, and August Weismann’s ‘germ plasm’. Carl Correns’s Anlagen and Wilhelm Johannsen’s ‘genes’ would replace them in the decade after 1900.Keywords: Idioplasm ; Pangenes ; Germ plasm ; Anlagen ; Gene; Genotype. (shrink)

William Bateson (1861-1926) has long occupied a controversial role in the history of biology at the turn of the twentieth century. For the most part, Bateson has been situated as the British translator of Mendel or as the outspoken antagonist of W. F. R. Weldon and Karl Pearson's biometrics program. Less has been made of Bateson's transition from embryologist to advocate for discontinuous variation, and the precise role of British and American influences in that transition, in the years leading up (...) to the publication of his massive Materials for the Study of Variation (1894). In this paper, I first attempt to trace Bateson's development in his early career before turning to search for the development of the moniker "anti-Darwinist" that has been attached to Bateson in well-known histories of the neo-Darwinian Synthesis. (shrink)

William Bateson has long occupied a controversial role in the history of biology at the turn of the twentieth century. For the most part, Bateson has been situated as the British translator of Mendel or as the outspoken antagonist of W. F. R. Weldon and Karl Pearson's biometrics program. Less has been made of Bateson's transition from embryologist to advocate for discontinuous variation, and the precise role of British and American influences in that transition, in the years leading up to (...) the publication of his massive Materials for the Study of Variation. In this paper, I first attempt to trace Bateson's development in his early career before turning to search for the development of the moniker "anti-Darwinist" that has been attached to Bateson in well-known histories of the neo-Darwinian Synthesis. (shrink)

According to the traditional account Mendel's paper on pea hybrids reported a study of inheritance and its laws. Hence, Mendel came to be known as The Father of Genetics. This paper demonstrates that, in fact, Mendel's objective in his research was finding the empirical laws which describe the formation of hybrids and the development of their offspring over several generations. Having found these laws (and not the laws of inheritance that he is generally credited with) he proposed a theoretical scheme (...) involving the formation of germinal and pollen cells in hybrids and their combination in fertilization competent to explain why his laws took the form that they did. Mendel's research shows a pattern of development closely paralleling the stages of empirical investigation beginning at the level of qualitative description in common language rising through four levels of increasing abstraction and culminating in a fifth level, his simple mechanical theory. This mechanism met all the tests that a theory of this type must pass. In that respect Mendel was highly successful and this success might be the reason why he did not push his theory to a higher level, a sixth level involving the use of particulate determiners; despite this fact, Mendel was credited with having taken exactly that step. (shrink)

Summary In 1979, Robert C. Olby published an article titled ?Mendel no Mendelian??, in which he questioned commonly held views that Gregor Mendel (1822?1884) laid the foundations for modern genetics. According to Olby, and other historians of science who have since followed him, Mendel worked within the tradition of so-called hybridists, who were interested in the evolutionary role of hybrids rather than in laws of inheritance. We propose instead to view the hybridist tradition as an experimental programme characterized by a (...) dynamic development that inadvertently led to a focus on the inheritance of individual traits. Through a careful analysis of publications on hybridization by Carl Linnaeus (1707?1778), Joseph Gottlieb Koelreuter (1733?1806), Carl Friedrich Gärtner (1772?1850), and finally Mendel himself, we will show that this development consisted in repeated reclassifications of hybrids to accommodate anomalies, which in the end allowed Mendel to draw analogies between whole organisms, individual traits, and ?elements? contained in reproductive cells. Mendel's achievement was a product of normal science, and yet a revolutionary step forward. This also explains why, in 1900, when the report he gave on his experiments was ?rediscovered?, Mendel could be read as a ?Mendelian? (shrink)

Recently, the nature of science (NOS) has become recognized as an important element within the K-12 science curriculum. Despite differences in the ultimate lists of recommended aspects, a consensus is emerging on what specific NOS elements should be the focus of science instruction and inform textbook writers and curriculum developers. In this article, we suggest a contextualized, explicit approach addressing one core NOS aspect: the human aspects of science that include the domains of creativity, social influences and subjectivity. To illustrate (...) these ideas, we have focused on Charles Darwin, a scientist whose life, work and thought processes were particularly well recorded at the time and analyzed by scholars in the succeeding years. Historical facts are discussed and linked to core NOS ideas. Creativity is illustrated through the analogies between the struggle for existence in human societies and in nature, between artificial and natural selection, and between the division of labor in human societies and in nature. Social influences are represented by Darwin’s aversion of criticism of various kinds and by his response to the methodological requirements of the science of that time. Finally, subjectivity is discussed through Darwin’s development of a unique but incorrect source for the origin of variations within species. (shrink)

Mendel's work in hybridization is ipso facto a study in inheritance. He is explicit in his interest to formulate universal generalizations, and at least in the case of the independent segregation of traits, he formulated his conclusions in the form of a law. Mendel did not discern, however, the inheritance of traits from that of the potential for traits. Choosing to study discrete non-overlapping traits, this did not hamper his efforts.

In Darwinism's Struggle for Survival Jean Gayon offers a philosophical interpretation of the history of theoretical Darwinism. He begins by examining the different forms taken by the hypothesis of natural selection in the nineteenth century and the major difficulties which it encountered, particularly with regard to its compatibility with the theory of heredity. He then shows how these difficulties were overcome during the seventy years which followed the publication of Darwin's Origin of Species, and he concludes by analysing the major (...) features of the genetic theory of natural selection, as it developed from 1920 to 1960. This rich and wide-ranging study will appeal to philosophers and historians of science and to evolutionary biologists. (shrink)

For twenty years there has been controversy over the level at which Gregor Mendel understood the implications of his experiments for heredity. We argue that he was a hybridist in the tradition of the nineteenth century who (1) designed innovative experiments in plant hybridization and (2) formulated a fundamental new theory for the transmission of traits from parents to offspring based on hypothetical determinants present in germ cells. His own summary, that '...pea hybrids form germinal and pollen cells that in (...) their composition correspond in equal numbers to all the constant forms resulting from the combination of traits united through fertilization', is tantamount to the discovery of what are now called the 'laws' of segregation and independent assortment. Mendel is therefore rightly credited with formulating a new theory of heredity. (shrink)