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Wilson, Edmund Beecher

WILSON, EDMUND BEECHER

(b. Geneva, Illinois, 19 October 1856; d. New York, N.Y., 3 March 1939)

cytology, embryology, heredity,

Wilson was among the most important and prolific biologists in the last part of the nineteenth and first part of the twentieth centuries. As an investigator of remarkable observational and analytical skill, he contributed significantly to an understanding of the structure and function of the cell. As a meticulous and exhaustive encyclopedist, he brought together and organized vast quantities of research related to the cell–its structural, hereditary, and developmental aspects. Wilson’s The Cell in Development and Inheritance (1896) is a monument to his comprehensive and profound understanding of major biological problems of the time, many of which are still unsolved. Born three years before the publication of Darwin’s Origin of Species, Wilson grew up in an era during which biology was transformed from a science dominated by natural history into one that was more and more concerned with rigorous and quantitative experimental analysis. His own work played a significant part in this transition.

Wilson was the son of Caroline Clarke and Isaac G. Wilson. His father, a graduate of Brown University and Harvard Law School, had gone west in the 1840’s to open a law practice. In later years he served as county judge, circuit court judge, and finally as chief justice of the Appellate Court of Chicago. Wilson’s maternal ancestors were descended from Thomas Clarke, reputed mate of the Mayflower who had settled at Plymouth, Massachusetts, in 1623. After the financial crash of 1837, Scotto Clarke (Wilson’s grandfather) moved from Boston to Geneva, Illinois, with his four children, of whom Caroline was the second youngest. She and Isaac Wilson were married in 1843 and had five children: Frank, Ellen, Charles, Edmund, and Harriet.

Wilson grew up in a cultured atmosphere that encouraged his two lifelong interests: the study of living things and music. When his father was appointed a circuit court judge in 1859, Wilson’s parents moved to Chicago and he was “adopted” by his mother’s sister, Mrs. Charles Patten of Geneva. Thus, from an early age Wilson had two homes, both of which encouraged his varied interests and provided him with, as he wrote, “four parents between whom I hardly distinguished in point of love and loyalty,” During his childhood he spent considerable time in the countryside around Geneva collecting specimens, which he stored in a special room provided for him in the Patten house. In the fall of 1872 his uncle suggested that young Wilson (he was not quite sixteen) take over the small country school that his brother Charles had taught the year before. Living with his aunt and uncle in Oswego, Illinois, he spent a year teaching everything from arithmetic to reading. It was a rewarding experience and strongly supported his desire for further education. Inspired by a cousin, Samuel Clarke, who was then attending Antioch college in Ohio. Wilson decided in the summer of 1873 to apply for admission to that institution. At Antioch he received his first formal instruction in zoology, botany, Latin, geometry, trigonometry, and chemistry, the latter with laboratory work that he Antioch College in Ohio, Wilson decided in the summer of 1873 to apply for admission to that institution. At Antioch he received his first formal instruction in zoology, botany, Latin, geometry, trigonometry, and chemistry, the latter with laboratory work that he found especially appealing. He paid his way partly by odd jobs, one of which was manufacturing the gas by which the college was lit. Instead of returning to Antioch the following fall, however, Wilson decided to begin a career in science by attending the Sheffield Scientific School at Yale, about which he had heard so much from Sam Clarke, who was enrolled there. Realizing that he lacked the proper background to enter Yale, he decided to live with his parents in Chicago for the next year (1874–1875) and attend the (old) University of Chicago for additional preparation.

Wilson entered the Sheffield Scientific School in 1875, and during his first year he took courses in zoology with A. E. Verrill and in embryology with Sidney I. Smith. At Yale he also had his first real exposure to the study of heredity and evolution, through a series of lectures given by William Henry Brewer, who made an indelible impression on Wilson and his classmates by lecturing “with the utmost fire and vehemence.”1 After receiving the bachelor’s degree (Ph.B.) in 1878, Wilson was invited to remain at Sheffield as a graduate student and assistant, which he did for one year; but soon Samuel Clarke once again found new and exciting horizons, this time at the newly opened Johns Hopkins University, where he was then enrolled. Clarke’s letters were so enthusiastic that Wilson and his close friend William T. Sedgwick, who also completed his studies at Yale, applied for and received fellowships to Hopkins beginning in the fall of 1878.

Wilson’s three years at Hopkins opened up a wholly new world–that of original investigation: he studied with the physiologist H. Newell Martin and the morphologist William Keith Brooks, both of whom emphasized research by continually pointing out the many unsolved problems in contemporary biology. Wilson received his Ph.D. in 1881, then remained at Hopkins for another year as assistant. In the spring of 1882 he went abroad for further study. For several months he was at Cambridge, where he met Michael Foster, William Bateson,and T. H. Huxley. Wilson then proceeded to Leipzig, where he worked in the laboratory of the invertebrate zoologist Rudolf Leuckart and attended lectures by the mechanistic physiologist Carl Ludwig. After leaving Leipzig he headed south to the zoological station at Naples. Through an arrangement with Williams College, where Samuel Clarke was then teaching, Wilson obtained a table in the laboratory for part of the year 1882–1883. The Naples station made a deep and lasting impression on him, for he met and became close friends with Anton Dohrn, the director, and with a number of embryologists and invertebrate zoologists, including Edouard Meyer and Arnold Lang. Like his friend T. H. Morgan, Wilson found that his first experience at the Naples station was one of the most exciting of his life, and set the direction for much of his future thinking about biological research. Many years later he wrote: “It was a rich combination of serious effort, new friendships, incomparable beauty of scenery, a strange and piquant civilization, a new and charming language, new vistas of scientific work opening before me; in short, a realization of my wildest, most unreal dreams.”2

On his return from Naples, Wilson taught for one year (1883–1884) at Williams College, replacing his cousin Sam Clarke, who was on leave to spend the year at Naples. The following year (1884–1885) he held a lectureship at the Massachusetts Institute of Technology, where he worked closely with his friend Sedgwick on a biology textbook they had begun planning several years earlier. In 1885 Wilson accepted an offer to head the biology department at Bryn Mawr College, where he remained until 1891, when he was appointed adjunct professor of zoology and chairman of the zoology department at Columbia. He remained at Columbia for the rest of his career, retiring as Da Costa professor of zoology in 1928.

Before assuming his official duties at Columbia, Wilson spent a year abroad, the first half with Theodor Boveri at Munich and the second half at Naples with the experimental embryologists Hans Driesch and Curt Herbst. During this and later years Wilson spent considerable time at marine stations and on collecting trips. His long association with the Marine Biological Laboratory, Woods Hole, Massachusetts (both as investigator and as trustee), and the Chesapeake Zoological Laboratory of Johns Hopkins were part and parcel of the importance he attached to studying living specimens, and especially marine forms as material for basic biological investigation.

A well-liked and eminently respected teacher, Wilson was known for his deep personal interest in his students. His lectures were highly polished and meticulously researched, possessing a balanced structure that demonstrated his strong sense of organization and aesthetics. Wilson’s success as a teacher stemmed partly from his enormous erudition and from the warm and articulate manner in which he conveyed his enthusiasms. He taught students at Columbia, both graduate and undergraduate, to see biology as a whole, as a series of fields–such as heredity, evolution, and embryology–at a time when many workers saw only separate disciplines. Among Wilson’s graduate students (or those who took some courses with him) at Columbia were G. N. Calkins, A. P. Mathews, C. E. McClung, H. J. Muller, Franz Schrader, and W. S. Sutton.

Music was of intense interest to Wilson throughout his life. He was a cellist of outstanding accomplishment, being, in the words of one contemporary musician, “the foremost non-professional player in New York.”3 To Wilson music was a solace, no less nor more beautiful than a living organism or a cell-something to which he owed, in his own words, some of the greatest pleasures of his life. In addition he loved sailing and skippered numerous collecting and pleasure expeditions out of Woods Hole, Bermuda, and other ports. He was also a linguist of considerable ability, with a knowledge of German, French, Italian, Spanish, and Arabic.

In 1904 Wilson married Anne Maynard Kidder, daughter of Jerome Henry Kidder, a friend of Spencer Fullerton Baird. Wilson had first met her at Woods Hole, where her family spent nearly every summer. The Wilsons had one daughter, Nancy, who became a professional cellist.

Although Wilson always worked concurrently on a variety of problems, his career can be divided roughly into three periods, each of which was dominated by a particular set of interests: 1879–1891, descriptive embryology and morphology (including studies of cell lineage); 1891–1903, experimental embryology (including the organization of the egg, the effects of various substances on differentiation, and artificial parthenogenesis); and 1903–1938, heredity (including the relation of Mendelism to cytology, sex determination, and evolution). To Wilson these various topics converged in a single problem: How does the individual organism lie implicit in the fertilized (or even unfertilized) egg? This problem could be broken down into a number of subsidiary and more specific questions: What is the mechanism by which the likeness of the parents is transmitted to the offspring? How is hereditary information transformed into a complete adult during embryonic development? How do the cell nucleus and its hereditary components direct the day-to-day activity of cells? How does the interaction between parts–nucleus and cytoplasm, egg and sperm, one embryonic tissue layer and another, the whole embryo and its environment –influence the final form of the adult organism? Early in his career Wilson saw that answers to all of these questions bring the investigator down to the level of the cell. He felt it was impossible fully to understand larger problems, such as those occurring on the tissue, organ, organismic, or population level, without a thorough knowledge of the cell–its structure, organization, and functions.

As a student of William Keith Brooks, Wilson was schooled in the aims and methods of morphology. Morphology, a discipline prominent in the late nineteenth century, utilized a variety of areas– embryology, systematics, comparative anatomy, cytology, heredity, and physiology–to determine phylogenetic relationships. Problems of embryology, for example, were not considered so much for their own value but, rather, for whatever light they might throw on the evolutionary history of various species. Although Wilson’s later work, particularly after 1891, gradually moved away from such overriding concern with phylogeny, his early papers strongly showed the influence of Brooks, whom he found an inspiring teacher. Brooks let his students alone, and Wilson was able to pursue whatever leads he wanted in the laboratory. Brooks also taught his students to think of biology in terms of problems still to be solved, rather than as a static and accumulated body of facts. He had a distinct philosophical bent that led him to think of problems-–biological or nonbiological–in a large framework.He seldom accepted any conclusion on its own, always examining not only the evidence on which it was based but also the underlying philosophical assumptions and points of view. Wilson wrote of his experience with Brooks: “It was through informal talks and discussions in the laboratory, at his house, and later at the summer laboratories by the sea that I absorbed new ideas, new problems, points of view, etc. . . . From him I learned how closely biological problems are bound up with philosophical considerations. He taught me to read Aristotle, Bacon, Hume, Berkeley, Huxley; to think about the phenomena of life instead of merely trying to record and classify them.”4

Descriptive Embryology and Morphology: 1879–1891. Although Wilson published two papers on the systematics of Pycnogonida (sea spiders) in 1879 and 1881, the result of work he had carried out for the Ph.B. at Yale, his earliest work of importance involved studies on the embryology and morphology of the coelenterate Renilla. This work was undertaken for his doctoral dissertation and consisted of comparing serial sections of embryos to determine the cellular changes occurring during development. Among other things, he observed that despite the regular division of the nuclei, the cytoplasmic cleavage of the egg was variable, either definitely segmenting the egg surface from the beginning or being relatively unexpressed until as late as the fourth division, when simultaneous formation of all cell boundaries might occur. By observing the development of various members of the Renilla colony (not all polyps were the same morphologically), Wilson drew some interesting physiological, ontogenetic, and phylogenetic conclusions. His presentation of the Renilla work wor the commendation of Huxley when Wilson was in England in 1882, and Huxley had the young man read the paper before the Royal Society (it was published in the Philosophical Transactions in 1883).5

During the two years following Wilson’s return to the United States, his teaching duties at Williams College and M.I.T. provided little opportunity for continuing his research. He did, however, complete the writing of a textbook, General Biology, with Sedgwick, based upon ideas they both developed from observing, H. Newell Martin’s approach to introductory biology at Johns Hopkins. General Biology, published in 1886, was an attempt to treat the study of living organisms from a more analytical and integrated viewpoint than had been customary. To this end Wilson and Sedgwick treated life as a manifestation of chemical and physical laws; the properties of life were a result of the properties of its constituent atoms and molecules. They also included both plant and animal material in their discussion, and tried to show how all organic processes involved an interaction of the living system with its environment. General Biology provides one of the earliest examples of Wilson’s broad perspective on biological problems, and as a textbook it was influential in bringing a new approach to the taxonomically and phylogenetically oriented introductory courses offered in most universities around the turn of the century.

After taking up his duties at Bryn Mawr in 1885, Wilson continued his studies on the cellular and morphological basis of early development with work on two annelids: Lumbricus, the earthworm, and Nereis, a marine polychaete. In his reports on Lumbricus (1887, 1889, 1890), he focused particularly on the origin of the mesoderm. He traced early development (cleavage through gastrula)in detail and demonstrated that the mesoderm is formed in a spiral or, as it was called, “mosaic” manner–that is, certain cells were set aside quite early to form the mesodermal tissues. These cells began to proliferate at the gastrula stage and all mesodermal tissues originated from them. Wilson’s work on Lumbricus settled an existing controversy on the nature of mesodern origin and showed, in conjunction with the subsequent work in Nereis, that spiral cleavage probably was characteristic of all annelids.

The earthworm proved to be a less than satisfactory organism for such studies. however, because it was difficult to follow the cells during successive cleavages. Following the lead of E. A. Andrews of Johns Hopkins, who had first pointed out the favorable nature of Nereis larvae (obtained at Woods Hole) for early embryological studies (these organisms show highly precise, regular, and easily observable cleavage patterns), Wilson carried out an exhaustive study of these forms. The Nereis Work, published in 1890 and 1892(although carried out mostly between 1885 and 1890), was a landmark both in the history of modern biology and in Wilson’s career.

To study early cleavage Wilson developed to a high degree a method known as “cell lineage.” It involved following the cell-by-cell development of young embryos from fertilization to blastula, cataloging the exact position of every daughter cell. From such studies it was possible to determine the exact ancestry of every cell in a blastula, and thus to determine the pattern by which cell division had occurred. Cell lineage studies are enormously intricate and detailed, and require considerable patience and observational skill (see Figure 1). The purpose of these studies was to apply the methods of comparative embryology to very early stages of development in different species. By accurately determining which cells in the early embryo came from which “lineage,” for example, Wilson was able to show that triploblastic animals (those having three germ layers) fall into two large groups in terms of the mode of mesodermal formation. One group, including the annelids, arthropods, and mollusks, showed the spiral or mosaic pattern he had observed in the earthworm. The other group, including the echinoderms, primitive chordates, and vertebrates, showed a pattern called “radial,” in which the mesoderm originates from pouches in the archenteron of the gastrula. Thus, cell lineage provided a means of establishing homologies in very early embryonic development that often were obscured in later stages. The work on Lumbricus and Nereis confirmed the study of cell lineage as an important embryological and morphological tool. It also established Wilson’s reputation as a biologist of considerable observational skill and interpretive ability.

Wilson’s detailed work also showed, however, that the problem of homologies, as many biologists were beinning to suspect,was more complex than had originally been thought when Ernst Haeckel proposed the biogenetic law in 1866. Although there might be many similarities among large animal phyla in cleavage patterns, there were some very important differences: structures obviously homologous in later embryonic stages sometimes derived from noncorresponding cells of earlier stages. Cell lineage patterns, like any other embryonic patterns, were not absolute criteria, and could suggest phylogenetic relationships only in the broadest outlines. Wilson recognized that embryonic processes(and structures) undergo evolution just as adults do, and that the present pattern of an organism’s development is not a fossilized repetition of its ancestral history.

The choice of problems in Wilson’s early work was largely influenced by the aims and methods of the morphologists, such as Brooks, under whom he was trained. Yet whatever problem he studied

always showed the distinct mark of his personality: a meticulous attention to detail and an eye for larger issues. At the same time, interested as he was in the grander problems of evolution, or the “nature” of life, he rigorously avoided flights of fancy or ungrounded speculation. He could work on cell lineage as a means of understanding evolutionary relationships, without committing himself unalterably to a strict and rigid interpretation of embryological homologies. To Wilson, the primary process in biological investigation was the accurate determination of what happened in any phenomenon. Once the process or structure was described and observed to be repeatable, then it could be related to larger issues and theories–the understandings– of how life is organized.

Experimental Embryology and Cytology: 1891–1903. Wilson’s first year as adjunct professor of zoology at Columbia was spent on leave in Europe (1891–1892). During the first half he worked with Theodor Boveri at Munich, and during the second half at the zoological station in Naples. From Boveri he learned much about the chromosomes and their relation to normal or abnormal development. He imbibed Boveri’s concern for the importance of the chromosomes in cell division and in determining the course of development. By the time Wilson reached Munich, Boveri had already concluded that the nucleus–specifically the chromosomes–was the most important element in determining an organism’s heredity. Further, Boveri argued that the chromosomes should be expected to influence development specifically–a thesis he was finally able to demonstrate in 1901 with experiments on doubly and triply fertilized sea urchin eggs. Particularly important during his stay in Munich were what Wilson learned about cytology and the strong personal relationship he developed with Boveri. To Wilson, Boveri was “far more than a brilliant scientific discoverer and teacher. He was a many-sided man, gifted in many directions, an excellent musician, a good amateur painter, and we found many points of contact far outside of the realm of science.”6 Wilson dedicated his major work. The Cell in Development and Inheritance (1896), to Boveri; and they remained close friends until Boveri’s death in 1915.

At Naples, Wilson was exposed to the new experimental embryology through the work of Hans Driesch and Curt Herbst, both of whom were testing Wilhelm Roux’s mosaic theory of development, put forth in 1888. Roux claimed that during cleavage, hereditary material is qualitatively divided among the daughter cells so that by the time the organism is fully differentiated, each cell has only one type of determinant (muscle cells have only muscle determinants, liver cells only liver determinants, and so on). Driesch, on the other hand, isolated cells from very young embryos–two-, four-, or eight-cell stage–and observed that each could develop into a normal larva, contradicting Roux’s premises. To Driesch, these findings emphasized the plasticity of the embryo and of the embryonic process. The embryo remained able to reconstruct itself, which suggested that all cells retained the full complement of hereditary information, which was not qualitatively restricted, as Roux supposed. The Roux-Driesch controversy focused on a new and important question: the mechanism of cell differentiation. Although this problem had been recognized for many generations (in fact, it had been implicit in preformation and epigenesis arguments from the seventeenth century on), it had been eclipsed as a prominent biological question by the increased interest in evolutionary questions (by morphology) in the latter half of the nineteenth century.

The questions of cell differentiation raised by the Roux-Driesch controversy greatly stimulated Wilson’s imagination, and turned his attention away from the more morphologically oriented studies and toward more critical questions of experimental embryology. Although he never abandoned the older methods of observation or the study of cell lineage, he began to see that embryology had important questions in its own right. Characteristically, Wilson kept his balance in the cross fire between the Roux and Driesch camps. He realized from his previous work on Nereis that although developmental processes are indeed determined, they also are plastic–they constantly reveal an interplay between the hereditary characteristics of the organism and the total environmental conditions to which it is exposed. The manner of development of a part, Wilson wrote in 1899, is “a manifestation of the general formative energy acting at a particular point under given conditions-the formative processes in special parts [being] definitely correlated with the organization of the entire mass.”7 He was acutely aware that embryonic parts continually interact, to differing degrees at various stages and varying from species to species.8 Although he reserved his final judgment until more critical evidence was available (unlike many other biologists, who quickly took sides), from the early 1890’s Wilson tended to agree with Driesch in opposing the seemingly very simplistic nature of the mosaic theory.9 The Roux theory was mechanically possible and logically consistent, but to Wilson it could not account for all the facts–for example, Driesch’s results or the phenomena of regeneration. Like Driesch, he saw that embryos have enormous abilities to restore themselves to normal function even if profoundly disturbed by experimental conditions. Unlike Driesch, however, Wilson did not take ultimate refuge in mystical forces and entelechies to explain these restorative capacities.

Exposure to the problems and methods of the new school of experimental embryology (called by Roux’s term, Entwicklungsmechanik, roughly translated as “developmental mechanics,” or simply as “experimental embryology”) raised in Wilson’s mind the question of how differentiation does take place if it is not the result of a simple segregation of hereditary material among daughter cells. He reasoned that if differentiation were not a mosaic process, the key to both its regularity and its amazing flexibility somehow must reside in the organization of the egg cell, particularly the cytoplasm. Assuming, as Boveri and others had shown, that every daughter cell receives the same number and kind of chromosomes as the parent cell, he concluded that differentiation must be triggered by variations in the cytoplasm in which each nucleus lies. Thus, the egg cell’s cytoplasm must be “preorganized” in such a way that regional localization of substances exists before cleavage begins. How the cytoplasm became structured in the first place was utter speculation, yet on the assumption of preorganization in the egg, Wilson could explain why some species seemed to show mosaic, and others nonmosaic, patterns of development. Those species appearing to have mosaic development simply showed cytoplasmic regionalization at a much earlier time in the embryo’s life than those that seemed to be nonmosaic.

The concept of “prelocalization,” or “formative substances,” was strongly criticized by numerous workers, including T. H. Morgan, who objected that the idea simply pushed the problem of differentiation back another step by postulating that it had already taken place within the cytoplasm of the egg. Since there was no satisfactory explanation of how this localization was attained, the concept of cytoplasmic differentiation in the ovum seemed to be without substance. Yet Wilson retained a conviction that prelocalization was to some extent a reality, for his studies suggested that the cytoplasm was not a homogeneous mix but was, in fact, quite diverse in its local composition. Although it is recognized today that eggs (indeed, all cells) have regional localization, such as polarity or gradients of distribution of certain substances, it has become clear that in many species the organization of the cytoplasm has little to do with the process of differentiation.

As a result of his work with Boveri, Wilson developed a strong interest in the cytological events surrounding cell division, particularly those involved in the maturation of the egg. On returning to the United States, he took up the study of chromosome movements, particularly spindle formation and the origin of the centrosomes (today called cell centrioles). In a lengthy study done with his pupil A. P. Mathews (1895), Wilson produced solid evidence against Hermann Fol’s widely held theory of the “quadrille of the centers.” (For maintained that the sperm and egg centrosomes fuse after fertilization, then divide, moving through the cytoplasm, like dancers changing partners in the eighteenth-century square dance quadrille, to form the two poles of the spindle apparatus.) Wilson showed that in echinoderms (especially the sea urchin) the poles were formed only by division of the sperm’s centrosome. He went on to demonstrate in later papers that the centrosomes were formed within the cystoplasm, not within the nucleus, as had previously been thought. Close observation of the movements and doubling of centrosomes convinced Wilson that the replication of these bodies did not cause, and was not caused by, the replication of the chromosomes. The doubling of both sets of structures probably responded, he maintained, to some underlying rhythm in the cell’s activity. He demonstrated this clearly by comparing rhythmic changes in protoplasmic activity in fragments of fertilized eggs of the marine mollusk Dentalium. Parallel rhythmic changes could be observed in the fragments and in nucleated portions of the same egg, even though the two parts were no longer physically associated.

During his initial decade at Columbia, Wilson prepared the first edition of The Cell in Development and Inheritance (1896), the basis of which was a series of lectures he gave in 1892–1893. The Cell was much more than a compilation of all the relevant information on various parts of the cell and various cell processes. It was not only a synthesis of a great deal of information (the bibliography in itself represents a prodigious effort) but also reflected Wilson’s wide-ranging and balanced views of contemporary problems, and his special emphasis on the function of cytology in elucidating such topics as embryology, heredity, evolution, and general physiology. The primary aim of the work, according to Wilson, was no less grandiose than “to bring the cell-theory and the evolution-theory into organic connection.”10 He believed that a fundamental understanding of the cell in all its aspects (structure, development, and physiological functions) would provide a better understanding of those fundamental processes–heredity, vairation, and differentiation–on which evolution was ultimately based.

The book is organized to lead the reader to appreciate the role of the cell-the nucleus and chromosomes-in heredity. The opening chapter deals with cell structure in broad overview, the second with cell division. The following three chapters deal with the germ cells: their structure and mode of origin, the phenomenon of fertilization, and the maturation divisions by which the gametes are prepared for fertilization. The sixth chapter deals with cell organization-the structure of chromosomes and the evidence for their “individuality” -and with centrosome origin and astral formation. The seventh chapter reviews the physiological properties of the cell, and the eighth treats the maturation of the ovum and the general laws of cell division of which it is an expression. In the final chapter Wilson considers the basic phenomena of development (as elucidated by Roux, Driesch, Herbst, Chabry, and others)in terms of cell structure and function.

The central conclusion of the book is in the eighth and ninth chapters, where Wilson focused on an in-depth study of the cleavage of the fertilized egg and on the various experimental results that shed light on the underlying processes by which cleavage could produce cell differentiation. Thus, at the end of the book Wilson was able to muster many lines of evidence to demonstrate the key point: “that the nucleus contains the physical basis of inheritance; and that chromatin, its essential constituent, is the idioplasm postulated on Nägeli’s theory.”11 Several lines of evidence led Wilson to place the seat of heredity within the cell nucleus and particularly in the chromosomes. First, the persistent accuracy with which the chromosomes replicate and are distributed, in contrast with the often random division of the cytoplasm by region, indicates the importance of ensuring that each daughter cell receives a full complement of chromosomes. Although Wilson had not abandoned the idea of cell prelocalization, he recognized that compartmentalization of the cytoplasm through cleavage was a much less precise process than distribution of the chromosomes. The greater precision of the chromosome distribution mechanism suggested that it was intimately related to the hereditary process, which by definition must be a regular and highly accurate phenomenon.

Second, the work of Boveri in particular (1887) had suggested that chromosomes maintain their individuality and continuity from one cell generation to the next. Contrary to an idea prevalent in the 1870’s 1880’s he and others had shown that the chromosomes do not disintegrate between divisions, but have the same spatial arrangement after interphase as before. Although Wilson was not willing to conclude that the physical structure of the chromosomes was necessarily maintained unbroken from interphase to interphase, he did argue that all evidence pointed to the maintenance of hereditary integrity.

Third, abundant cytological evidence showed that while sperm and egg had enormously different cytoplasmic components (the sperm has virtually no cytoplasm), they seemed, on the whole, to affect the heredity of the offspring equally. Thus it would appear, Wilson pointed out, that the cytoplasm had relatively little hereditary function.

Fourth, experiments by M. Nussbaum, Gruber, Verworn, and others on many different types of cells (including Protozoa) indicated that enucleated cells did not function normally. Whatever the exact function of the nucleus, it was necessary to the normal maintenance of cell activity. It seemed evident that the control that the nucleus appeared to exert over the entire cell must be an expression of the cell’s heredity.

Even in 1896 Wilson recognized that the control of the nucleus over the cytoplasm was ultimately a matter of chemical interactions. Too little was known about the chemistry of chromatin for him to formulate a specific idea about how this might work, but he did maintain that the nucleus was the seat of constructive (anabolic), and the cytoplasm of destructive (catabolic), processes. This view came directly from Claude Bernard, who some twenty years earlier (1878) had postulated a similar division of chemical labor between nucleus and cytoplasm.12 To Wilson, inheritance (associated with the nucleus) “is the recurrence through the transmission from generation to generation of a specific substance or idioplasm which we have seen reason to identify with chromatin. If the nucleus be the formative center of the cell, if nutritive substances be elaborated by or under the influence of the nucleus while they are built into the living fabric, then the specific character of the cytoplasm is determined by that of the nucleus.”13

Yet Wilson was aware enough of biological phenomena in general to recognize that the cytoplasm also must profoundly influence the nucleus. The nucleus could not function, after all, if it did not have a cytoplasm upon which to act. But more than that, he saw that as the nucleus altered the cytoplasm (by building up certain substances), of necessity it also altered its own environment. Chemical change–interaction ;and modification– was always occurring between the nucleus and cytoplasm in a living cell. Development was nothing more than a highly ordered example of this interaction, in which the expression of hereditary information in each cell nucleus was successively altered as cleavage and morphogenetic changes occurred. To Wilson, the nucleus and the cytoplasm were intimately involved in the cell’s chemistry, heredity, and development. They had different but complementary functions, and had to be understood in relation to each other. Neither could, or should, be viewed in isolation.

The Cell went through three editions and numerous reprintings. It is estimated that this book has been the single most influential treatise on cytology during the twentieth century. Many of the problems that Wilson clearly outlined (such as the relationship between the nucleus and cytoplasm in cell differentiation) are still being investigated. And no one has succeeded in posing those problems more clearly than he did in his many writings, particularly in The Cell. In reading The Cell, one is impressed not only by Wilson’s skill as a summarizer (an encyclopedist in the best sense of the word) but also with the enormous patience and effort on the part of hundreds of other workers as well, who over the past century have contributed to the growing knowledge of cell structure and function.

Studies on Chromosomes and Heredity: 1903–1912. Historically, one of the most important functions of The Cell was to pave the way for a more rapid acceptance of Mendelian theory, once it was reintroduced to the scientific community in 1900. By focusing attention on the cell nucleus, and particularly on the chromosomes as the seat of heredity, Wilson prepared many biologists-especially cytologists-to see the relationship between Mendel’s laws and the events of maturation of the sperm and egg. Recognition of the possible parallel between the segregation and random assortment of Mendelian “factors” (later called “genes”) and the chromosome reduction division (meiosis) that occurs during gametogenesis ultimately provided a material basis for the science of genetics.

Although two of the rediscoverers of Mendel’s work–Carl Correns and Hugo de Vries–had offered a chromosomal interpretation of their own and Mendel’s findings shortly after 1900, it was not based on much observational evidence. In 1900, however, H. von Winiwarter reported the occurrence of synapsis in early reduction division; and in 1901 T. H. Montgomery discovered that the chromosomes are present in germ cell nuclei (prior to reduction division) as pairs of homologues. With these observations Wilson and his group were ready by 1901 to seek possible connections between Mendelism and cytology. In fact, it was one of Wilson’s graduate students, Walter S. Sutton, who made the connection first and most cogently (1902). In studying synapsis (the intertwining of the two chromosomes in a homologous pair of chromosomes), Sutton showed that the visible behavior of the chromosomes afforded an explanation of the first and second Mendelian laws. His careful studies of chromosomal pairing provided cytological evidence that the chromosomes segregating in reduction division are the two members of a homologous pair, not any two random chromosomes. Thus each chromosome could be considered as the counterpart of a Mendelian factor, or at least a bearer of one factor. Wilson quickly came to see the importance of Sutton’s work, and supported his conclusions.

In 1902 another former student of Wilson’s, Clarence E. McClung, pointed out that the unpaired “accessory” chromosome (later called the X by Wilson), long known to exist in the males of some arthropods, might offer a clue to how sex was inherited. Wilson was intrigued by McClung’s work and set out to study the occurrence and distribution of the accessory chromosome in a number of species, mostly insects. In 1905 Wilson and, independently, Nettie M. Stevens of Bryn Mawr published extensive cytological evidence suggesting a chromosomal basis for sex determination.14 These works provided the missing link between cytology and heredity. Wilson and Stevens concluded that females normally have a chromosome complement of XX and males have one of XY. In oögenesis and spermatogenesis, the X and X (for oögenesis) and the X and Y (for spermatogenesis) separate, and end up, by meiotic division, in separate gametes. All eggs thus have a single X chromosome, while sperm can have either an X or a Y. When a Y-bearing sperm fertilizes an egg, the off spring is a male (XY); when an X-bearing sperm fertilizes an egg, the offspring is a female (XX).

Wilson and Stevens recognized that a few groups of organisms have variations (or reversals) of this scheme–for instance, species that normally lack a Y or in which the females are XY and the males XX (the latter case is true for months, butterflies, and birds). The 1905 papers by Wilson and Stevens not only cleared up a long-standing controversy on the nature of sex determination (for example, whether it was hereditarily or environmentally induced) but also were the first reports that any specific hereditary trait (or set of characteristics, such as those associated with sex) could be identified with one specific pair of chromosomes.

Wilson pursued studies on the chromosomes, particularly in relation to sex inheritance, over the next seven years (1905–1912), producing a series of eight papers entitled “Studies on Chromosomes.” In general these papers worked out the chromosomal theory of sex determination (essentially as it is understood today) in great detail, and supported its Mendelian nature. Among other things, Wilson showed that the Y chromosomes in different insect species are of widely different sizes in comparison with the X; in some species the X and Y are of virtually equal size, whereas in others the Y is very small, and in still others it is nonexistent. He also observed that in a species where the female is normally XX, some females have the combination XXY and some males have only a single X and no Y. Wilson interpreted these cases as having resulted from the failure of the X and the Y to separate during spermatogenesis in the organism’s male parent. When the same phenomenon was observed in Drosophila by C. B. Bridges in 1913, he and Wilson jointly coined the term “nondisjunction” for the failure of two homologues to segregate during meiosis. These and other results led Wilson to postulate that the Y chromosome had degenerated over the course of evolutionary history. He felt it represented either inactive chromatin material or an excess that was duplicated elsewhere in the chromosome group,15 Wilson considered the X to be the active member of the sex chromosome pair, and therefore the causal agent of sex determination. Although we know today that the matter is not so simple, he was essentially correct in judging that the Y has little actual hereditary function, in relation to sex or anything else.

Wilson speculated that the difference between the X and the Y might be due to the presence on the X (or associated with it) of a specific chemical substance (perhaps an enzyme) that produces a definite reaction on the part of the developing individual.16 Surprisingly, his idea that a chromosome might carry out its hereditary function by producing enzymes is close to the modern conception that genes (located on chromosomes) code for enzymes that catalyze specific biochemical reactions. Although Wilson was the first to point out, repeatedly, that too little was known about the chemistry of living cells to formulate any meaningful theory of how characteristics were determined, he saw the importance of phrasing hereditary or developmental problems in chemical terms.

Wilson’s studies on chromosomes provided the important cytological foundation upon which T. H. Morgan’s later chromosome theory of inheritance was based. In 1910 Morgan, Wilson’s close friend and colleague in the zoology department at Columbia, discovered a white-eyed male Drosophila in his laboratory culture (Drosophila normally have red eyes). Although initially skeptical of the Mendelian theory, Morgan found that Mendel’s assumptions provided the best means of accounting for the hereditary pattern observed in the white-eye condition. Moreover, he saw that white eyes seemed to occur mostly but not exclusively in males, a fact that could be explained only by assuming that the “factor” for eye color was located on the X chromosome. Wilson quickly saw the implications of this work, and in 1911 he used Morgan’s findings as further support for a chromosomal interpretation of sex. He also saw immediately what later came to be called sex-linked inheritance. Thus, the keystone to the chromosome theory of inheritance was laid in the Columbia laboratory, where Morgan from the animal-breeding side, and Wilson from the cytological side, provided evidence that hereditary units exist as material entities located on chromosomes in the nucleus.

Aside from his intellectual contribution to the chromosome theory of heredity, Wilson was influential as a strong supporter of Morgan and his group as they expanded the Drosophila work. As head of the zoology department, he encouraged all the “fly room” workers, especially graduate students, by his persistent interest in the work and by the obvious connections it bore to his earlier work on chromosomes. Most of the students who worked with Morgan (Muller, A. H. Sturtevant, Bridges, Edgar Altenberg) had been Columbia undergraduates and had taken Wilson’s courses or used his textbook in the introductory course taught by G. N. Calkins and James H. McGregor. In his teaching from 1906 on, Wilson particularly emphasized the relations between Mendelian heredity, chromosomes, and evolutionary theory, using as the text for his second-level one-semester course on heredity R. H. Lock’s provocative book Variation, Heredity and Evolution (1906). Far ahead of its time, Lock’s book treated Mendelian heredity, cytology, and Darwinian evolution in a completely integrated fashion, something few biologists did until after 1915.

Thus many of the students who came to work with Morgan after 1910 had been prepared by Wilson to see clearly the relationships between chromosomes, Mendelian theory, and the concept of natural selection in a way that not even Morgan himself was able to accomplish at the time. Wilson also supported the Drosophila group by incorporating its findings into his own work, and by championing the new ideas long before many other biologists began to follow Morgan’s lead. Although neither Wilson, Morgan, nor any other biologists at the time could “see” that Mendelian genes were parts of chromosomes, or that crossing-over and exchange of chromosome parts actually took place as the Drosophila group postulated, Wilson felt that the conclusions were sound because they were consistent and fitted all the data. In a lecture in 1913, he pointed out that although the hypothesis of crossing-over and chromosome mapping techniques based on it were bold ventures, they were justified because, pragmatically, they worked; that is, they accounted for all the data better than any other explanations. To Wilson it was by just such venturesome ideas that new possibilities of discovery were opened.17

Recognizing the importance to Morgan’s work of testing the assumption of crossing-over (in meiotic divisions), Wilson set out in 1912 (study VIII) to examine the cytological evidence for such a process. Obtaining preparations of germ tissue from F. A. Janssens (who had originated the hypothesis of crossing-over in 1909), A. and K. E. Schreiner, and McClung, Wilson showed that synapsis seemed to be a real phenomenon–that is, homologous chromosomes do appear to come together and wrap around each other prior to the first meiotic division. The evidence was not clear enough, however, to show any signs of the actual exchange of chromosome parts. It was not until 1931 that techniques were developed sufficiently for such workers with animals as Curt Stern and with plants as Barbara McClintock and Harriet Creighton to observe actual exchanges between strands and thus provide final proof that crossing-over was a real phenomenon.

The years between 1902 and 1912 marked the zenith of Wilson’s creative period. The eight studies on chromosomes were brilliant examples of his observational and analytical skill. In this work his broad-reaching mind incisively drew the connections between Mendelian theory and cytology, long before many other workers (including Morgan) were prepared to make the same bold leaps. The chromosomal concept of Mendelian heredity was a logical view for Wilson to maintain because it provided the link he had intuitively held for many years between the cell, heredity, and development. The main theme enunciated in The Cell (1896) was being realized in actuality by the parallel studies on chromosomes in Wilson’s laboratory and on the process of heredity in Morgan’s.

Later Work: 1912–1938. Wilson’s studies after 1912 were variations of a single basic question: What cell constituents other than the chromosomes affect the hereditary process? There were really two aspects to this question. One was that of extrachromosomal inheritance: the replicative function of such organelles as chloroplasts or mitochondria, which by 1920 were known to be able to reproduce themselves without nuclear control. The other question was the effect of the cytoplasm on the expression of genetic potential in the nucleus. In investigating the former, Wilson studied various cytoplasmic bodies in scorpions and insects: the Golgi bodies, chondriosomes (today called mitochondria), and vacuomes (today, vacuoles). From these observations he concluded that at least the Golgi bodies and chondriosomes increase in size and fragment, so that daughter cells get equal numbers with each division. Nevertheless, he maintained that these cytoplasmic bodies do not have genetic individuality as chromosomes do-they are all very much alike, and must be derived from the same genetic ancestry, with little or no divergence.18 In investigating the effect of the cytoplasm on expression of genetic potential, Wilson steadfastly stated his earlier view that it is impossible to make any rigid distinction between the nucleus and cytoplasm. What was important was to attempt to determine the precise ways in which the nucleus influenced the cytoplasm, and vice versa; in that way not only would it be possible to achieve a clearer understanding of how the cell functions to maintain itself day by day, but also it would be possible to see more clearly how such phenomena as cell differentiation might be brought about.

In his later years Wilson came more and more to view the cell as a plastic, ever-changing structure, continually building itself up and tearing itself down, a constant dialectic between stability and change, heredity and variation, maintenance and differentiation. In the flux of materials and changing structures, the constancy in cell life was an underlying organization of molecules and intramolecular associations that produced life.

The culminating work of Wilson’s later years was the complete revision and expansion of The Cell into a third edition (1925). So much information had accumulated regarding cytological phenomena in the quarter-century since the second edition that only Wilson, with his encyclopedic mind and incisive judgment, could have undertaken, let alone completed, such a task. Although Wilson’s health showed signs of decline after 1920, he nonetheless worked tirelessly on what was a monumental undertaking for a man in his mid-sixties. The completed volume of over 1,200 pages was published when Wilson was sixty-nine. “In it,” wrote H. J. Muller, “virtually the whole of cytology from the time of its birth more than half a century before, stood integrated.”19 The revised edition, under the title The Cell in Development and Heredity, was awarded the Daniel Giraud Elliot Medal of the National Academy of Sciences (1928) and the gold medal of the Linnean Society of London (1928). Perhaps the most significant testimony to its value is that it is still found on the bookshelves of cytologists, not only as a useful reference source for older literature but also because many of the problems it posed are still being investigated. The electron microscope, with all the resolution of fine detail and astounding discoveries it has made possible, has not yed many of the questions and problems that Wilson raised. Developments in cytology since 1925 have expanded upon, but not contradicted, the underlying concepts that he wove so skillfully into the fabric of The Cell.

In all three editions of The Cell Wilson related the phenomena of heredity, cell structure and function, and development to organic evolution and adaptation. To him the central problem of evolution as posed by Darwin was how hereditary variations come about. In 1896 he recognized the importance of August Weismann’s conception of the continuity of the germ plasm, and much of his future cytological work on chromosomes served to support the basic idea of a separation of germ and somatoplasm. Wilson’s insight into this problem lay in his recognition that heredity was a cellular phenomenon–something that Darwin and his followers also had recognized. The Darwinian theory of pangenesis was, after all, only a cellular mechanism for how variations could occur. From his early studies of cells and his growing awareness that the nucleus was the locale of a cell’s heredity, Wilson rejected the pangenesis theory. Because cell heredity was localized in the nucleus, specifically in the chromosomes, and because each set of chromosomes had continuity–that is, it transmitted its effects only vertically from one generation to the next–somatic variations could not be transmitted to the germ cells of the same organism.

By his further work on chromosome structure and variation, approached cytologically and framed in Mendelian terms, Wilson tried to show how new heritable variations arose and could be acted upon by selection. The most significant support that he gave to the Darwinian theory was his conviction that heredity (and its correlate, variation) was ultimately a cellular (chromosomal) phenomenon. By emphasizing this relationship and by providing, through cytological studies, a material basis for Mendelian heredity, Wilson paved the way for a comprehensive theory of evolution, which emerged after 1930.20

Despite his strong interest in evolution, Wilson was somewhat skeptical of certain aspects of the Darwinian theory of natural selection. Like many of his contemporaries, he greatly admired Darwin’s work as a naturalist and his synthetic powers as expressed in The Origin of Species. He felt, however, that Darwin had placed too much emphasis on evolution by the accumulation of small variations (what Darwin called “individual differences”) that could not be shown to be inherited. By failing to distinguish adequately between inherited and acquired variations, Darwin had not provided a mechanism for the origin of adaptations. Wilson also was bothered by the emphasis that Darwin’s theory placed on “chance” in the origin of species. Strongly influenced as he was by his old teacher, he stated in 1907 that Brooks’s epigram was true, that “the essence of life is not protoplasm but purpose.”21 Wilson did not believe in teleological principles or in vitalistic driving forces in evolution. Nevertheless, like many biologists raised in the era of Haeckel, Weismann, and the other German Darwinians, it was difficult for him to believe that purpose was altogether lacking in evolutionary processes. The evolution of adaptations as intricate and functional as the vertebrate eye, simply by the accumulation of numerous chance variations, seemed to defy reason. As late as 1930 Wilson wrote: “[I am] not yet quite ready to admit that higgledy-piggledy can provide an adequate explanation of organic adaptations.”22 Yet when confronted with alternative explanations of adaptation, Wilson always found himself forced to return to Darwin. In 1915 he wrote, “We have made it the mode to minimize Darwin’s theory . . . but. . . we should take heed how we underestimate the one really simple and intelligible explanation of organic adaptation, inadequate though it may now seem, that has thus far been placed in our hands.”23

Wilson’s Scientific Methodology. Although Wilson was trained as a morphologist, he embraced the quantitative and experimental side of biology early in his career, following his 1891–1893 stay in Europe, particularly at the Naples station. Along with a number of younger biologists around the end of the nineteenth century, he felt that for biology to make any progress, it had to avoid vapid speculation and the construction of all-embracing theories that had no basis in empirical evidence. To him careful observation, hypothesis formulation, and experimentation were the only true means of reaching valid conclusions. Experiment alone was never enough–experiments had to be designed to test something, and that something was a particular hypothesis. In Wilson’s view, however, hypotheses had to be testable. If they were not, then oversimplified and misleading ideas could gain a vast following, as had happened with the speculative theories of Haeckel and Weismann. The strong advocacy that Wilson and many of his contemporaries (including T. H. Morgan, Ross G. Harrison, Jacques Loeb) made in behalf of experimental biology was in some part a reaction to the nonexperimental, speculative methodology characteristic of a previous generation.

Behind Wilson’s experimentalism lay a firm belief that “the scientific method is the mechanistic method.”24 By mechanistic he meant, as did most of the younger workers at the time, that phenomena should be subject to experimental analysis and that biological processes should be investigated in physicochemical terms. Wilson did not argue that the only meaningful explanation of a biological process was one couched in terms of chemical equations. He knew full well that such explanations were not then possible for most biological phenomena, yet he firmly believed that they should be sought as much as chemical theory and technology would allow. He was not a crude mechanist and could not share the extreme mechanical bias of Jacques Loeb. Nevertheless, he felt that until biologists could understand the complex events characterizing cell life in chemical terms, they could not gain much understanding of the nature of life or its immense complexities.

Philosophically, Wilson believed that the scientific method was the only way to understand the world–inside or outside the laboratory; but he did not think that scientific truths are final truths, for truth itself, he claimed, is relative. To Wilson the fundamental concepts of science had no finality. “The profound significance of what we call natural laws lies in the fact that they tersely sum up our experience of the world at any given moment. . . .”25 Science was for him a creative process, the ideas running in advance, to some extent, of the hard facts. Wilson’s own artistic and aesthetic sense allowed him to see science as no different, in its creative aspects, from music, art, or literature: “At every point the material world overflows with half-revealed meanings about which science is forever weaving her imaginative fabrics; and at their best these have all the freedom, boldness and beauty of true works of art.”26 Wilson the musician and Wilson the cytologist were one and the same person, applying different skills at different times but with the same aesthetic delight and by the same intellectual methods. For Wilson internal beauty had to be matched with external reality. Music to him was not simply a theory–it was the reality of notes played on an instrument, filling a room and affecting human beings. Science also was not theories–fossilized answers–it was the reality of what could be observed, predicted, and repeated by living, imaginative people. Both music and biology had their theoretical sides, but the theories had meaning only as they were applied in practice on a day-to-day basis.

In his teaching, as in his investigation and his writing, Wilson emphasized that science was not accumulated knowledge, but a process of reasoning, understanding, and testing that understanding against natural phenomena. He saw life as a whole, in all its manifest complexities, harmonies, and apparent inconsistencies. He was willing to let an issue rest unresolved rather than propose a solution that was untested or untestable. Yet in his emphasis on process, he saw the human side of science–that it was ultimately the activity of human beings, not monuments of static information. Externally, he lived the life of the classic reserved scholar; but beneath this formality was a fire that, as Muller put it, was rigorously channeled into self-discipline. Nevertheless, it was this fire that shone through even the most meticulous pages of cell lineage studies, or the most detailed analysis of mitotic patterns. It transformed details into the comprehensive and exciting fabric of biological ideas that Wilson wove throughout his life.

NOTES

1. T. H. Morgan, “Edmund Beecher Wilson,” 318.

2.Ibid., 320.

3. H. J. Muller, “Edmund B. Wilson–an Appreciation,” 166.

4. Morgan, op. cit., 319

5. E. B. Wilson, “The Development of Renilla.

6. Morgan, op. cit., 321.

7. Muller, op. cit., 17.

8. E. B. Wilson, “Amphioxus and the Mosaic Theory of Development,” in Journal of Morphology,8 (1893), 579–638, esp. 636–638.

9. The “mosaic theory” of Roux and Weismann is not to be confused with the “mosaic” or spiral pattern of cleavage Wilson had discussed in his earlier (1887, 1889, 1890) work on annelid embryology. The Roux-Weismann “mosaic” theory held that differentiation during ontogeny was caused by the qualitative nuclear division of hereditary material during cleavage; as development progressed, cells gradually lost more and more hereditary potential in terms of the kinds of adult tissues they could form.

10. E. B. Wilson, The Cell in Development and Inheritance, intro., 11.

11.Ibid., 302.

12.Ibid., 247; Bernard’s work is in his Leçons sur les phénomènes del la vie,I (Paris, 1878), 523.

13. Muller, op. cit., 35.

14. E. B. Wilson, “The Chromosomes in Relation to the Determination of Sex in Insects” ; N. M. Stevens, “Studies in Spermatogenesis With Especial Reference to the ‘Accessory Chromosome’” Publications. Carnegie Institution of Washington, no. 36 (1905).

15. E. B. Wilson, “Studies on Chromosomes. V. The Chromosomes of Metapodius, a Contribution to the Hypothesis of the Genetic Continuity of Chromosomes.”

16.Ibid.

17. Muller, op, cit., 156.

18.Ibid., 160.

19.Ibid., 161.

20. For Wilson’s more explicit attempts to discuss cytology and Darwinism, see his “The Cell in Relation to Heredity and Evolution” ; and his “Biology.”

21. Muller, op, cit., 153.

22.Ibid., 153–154.

23.Ibid., 153.

24.Ibid., 24.

25. E. B. Wilson, “Science and Liberal Education,” in Science,42 (1915), 625–630.

26.Ibid.

BIBLIOGRAPHY

I. Original Works. There is no complete, or even selected, collection of Wilson’s writings, although a bound set of his reprints, with only minor omissions, is in the library of the Marine Biological Laboratory, Woods Hole, Mass. A complete bibliography is in T. H. Morgan’s obituary (see below).

Wilson’s books are General Biology (New York, 1886), written with William T. Sedgwick; An Atlas of Fertilization and karyokinesis of the Ovum (New York,) (1895); The Cell in Development and Inheritance (New York, 1896; 2nd ed., 1900; 3rd ed., rev. and enl., The Cell in Development and Heredity. 1925)–1st ed. repr., with intro. by H. J. Muller, as Sources of Science, no. 30. (New York, 1966).

Among his most important journal articles are “A Problem of Morphology as Illustrated by the Development of the Earthworm” (abstract), in Johns Hopkins University Circulars (May 1880), 66; “The Development of Renilla,” in Philosophical Transactions of the Royal Society,174 (1883),723–815; “The Embryology of the Earthworm,” in Journal of Morphology3 (1889), 387–462 “The Cell–Lineage of Nereis. A Contribution 361–480; “The Mosaic Theory of Development,” in Biological Lectures. Marine Biological Laboratory, Woods Hole,1893 (1894), 1–14; “Maturation, Fertilization, and Polarity in the Echinoderm Egg. New Light on the ‘Quadrille of the Centers,” in Journal of Morphology,10 (1895), 319–342, written with A. P. Mathews; “On Cleavage and Mosaic-Work,” in Archiv für Entwicklungsmechanik der Organismen3 (1896), 19–26; “The Structure of protoplasm,” in Biological Lectures, Woods Hole Marine Biological Laboratories for 1898 (1899), 1–20; “Cell Lineage and Ancestral Reminiscence,” , ibid 21–42; “Some Aspects of Recent Biological Research” in international Monthly (June 1900). 1–22 “Mendel’s Principles of Heredity and the Maturation of the Germ-Cells,” in Science,16 (1902), 991–993; “Mr. Cook on Evolution, Cytology and Mendel’s Laws,” in Popular Science Monthly (Nov. 1903), 188–189; “The Problem of Development,” in Science,21 (1905), 281–294, presidential address, New York Academy of Sciences, 19 Dec. 1904; and “The Chromosomes in Relation to the Determination of Sex in Insects,” ibid.,22 (1905), 500–502.

Wilson’s eight “Studies on Chromosomes” are in Journal of Experimental Zoology,2 (1905), 371–405; II. “The Paired Microchromosomes, Idiochromosomes and Heterotropic Chromosomes in Hemiptera,” ibid., 507–545; III “The Sexual Differences of the Chromosome-Groups in Hemiptera, With Some Considerations on the Determination and Inheritance of Sex,” 3 (1906), 1–40; Iv. “The ‘Accessory’ Chromosome in Syromastes and Pyrrochoris With a Comparative Review of the Types of Sexual Differences of the Chromosome Groups,” 6 (1909), 69–99; V. “The Chromosomes of Metapodius, a Contribution to the Hypothesis of the Genetic Continuity of Chromosomes” ibid., 147–205; VI. “A New Type of Chromosome Combination in Metapodius,9 (1910), 53–78; VII. “A Review of the Chromosomes of Nezara ; With Some More General Considerations,” 12 (1911), 71–110; VIII, “Observations on the Maturation-Phenomena in Certain Hemiptera and Other Forms, With Considerations on Synapsis and Reduction,” 13 (1912), 345–448.

Other papers are “Mendelian Inheritance and the Purity of the Gametes,” in Science,23 (1906), 112–113; “Recent Studies of Heredity,” in Harvey Lectures (1906–1907), 200: “Notes on the Chromosome Groups of Metapodius and Banasa,” in Biological Bulletin,12 (1907), 303–313; “Differences in the Chromosome Groups of Closely Related Species and Varieties, and Their Possible Bearing on the ‘Physiological Species,’” in Proceedings, Seventh International Congress of Zoology (1909), 1–2; “The Cell in Relation to Heredity and Evolution,” Fifty Years of Darwinism (New York, 1909). 92–113; “The Chromosomes in Relation to the Determination of Sex,” in Science Progress,16 (1910), 570–592; “Some Aspects of Cytology in Relation to the Study of Genetics,” in American Naturalist46 (1912), 57–67; “Observations on Synapsis and Reduction,” in Science,35 (1912), 470–471; “The Bearing of Cytological Research on Heredity,” in Proceedings of the Royal Society,88 (1914), 333–352, the Croonian lecture for 1914; “Chiasmatype and Crossing Over,” in American Naturalist,54 (1920), 193–219, written with T. H. Morgan; “The Physical Basis of Life,” in Science,57 (1923), 277–286; and “Biology” , in A Quarter Century of Learning ; 1904–1929 (New York, 1931), 241–260.

II. Secondary Literature. The standard obituary is T. H. Morgan, “Edmund Beecher Wilson, 1856–1939,” in Biographical Memoirs, National Academy of Sciences,21 (1941) 315–342, condensed in Science,89 (1939), 258–259; also New York Times (4 Mar. 1939), 15, col. 1.

Perhaps the best single evaluation of Wilson’s life and especially of his career, and the source that has been particularly helpful in preparing this article, is H. J. Muller, “Edmund B. Wilson–an Appreciation,” in American Naturalist,77 (1943), 5–37, 142–172. Muller’s familiarity with Wilson’s work is thorough, and his assessment of Wilson’s place in the history of twentieth-century biology is authoritative. A shorter version of this “appreciation” is in Muller’s intro. to the 1966 repr. of The Cell in Development and Inheritance.

Despite his importance to twentieth-century biology (and American science especially), there is a surprising lack of biographical or critical material on Wilson’s life and work.

Garland E. Allen

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Wilson, Edmund Beecher

Edmund Beecher Wilson, 1856–1939, American zoologist, b. Geneva, Ill., grad. Yale (Ph.B., 1878), Johns Hopkins (Ph.D., 1881). He taught at Bryn Mawr (1885–91) and at Columbia (1891–1928), where he initiated research in genetics and attracted many followers. His principal work was on the function of the cell in heredity and on the role of the chromosomes (including the significance of the sex chromosome). He also studied embryology and experimental morphology. His works include The Cell in Development and Heredity (1896, 3d ed. 1925) and The Physical Basis of Life (1923).

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