Boveri, Theodor Heinrich

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Theodor Heinrich Boveri

During his scientific career in Germany in the late 1800s and early 1900s, Theodor Boveri (1862–1915) worked in fields that then had no names. He was a professor of zoology at the universities of Munich and later Würzburg, but in modern terminology he would not be called a zoologist. He was really a cytologist (a scientist who studies cell structure), a geneticist (a scientist who studies heredity), and an embryologist (one who studies organisms at their earliest stages of development).

Boveri made several important discoveries concerning the growth and reproduction of organisms, but the most important one was that chromosomes—threadlike parts of cells that carry what we would now call genetic information during reproduction—were different from one another. In Boveri's words (as quoted on the website of the University of Würzburg's biology department), chromosomes were "independent individuals that retain this independence even in the core of a cell at rest." That insight helped lay the foundation for the entire modern understanding of how traits of an organism are transmitted from parents to offspring.

Boveri grew up in Bamberg, Germany, and except for several sojourns in Naples, Italy, spent his whole life in southern Germany. Despite his Italian last name, his family had lived in Germany's Franconia region for generations. His father Theodor was a doctor who gave up medicine in favor of music and art after his marriage, managing to squander most of a moderate family fortune in the process. Boveri's mother was also artistically inclined, and Boveri himself not only became a skilled pianist and painter but also exhorted his students to take special care with the prose and drawings of their scientific papers. One of his students, quoted in Fritz Baltzer's biography Theodor Boveri: Life and Work of a Great Biologist, recalled that Boveri returned the first draft of one of his papers with the comment "You must now treat it as a work of art."

Boveri attended elementary schools in Bamberg and went on to the Realgymnasium, school in Nürnberg, studying Latin and ancient Greek in addition to science and graduating in 1881. He went on to the University of Munich, living in a sort of glorified dormitory called the Maximilianeum that was reserved for top graduates of southern Germany's secondary schools, served as a pipeline to top academic and governmental jobs, and came with free room and board. This high-powered program allowed Boveri to find his true calling; whereas many European students followed (and still do follow) predetermined courses of study, Boveri started out studying history and philosophy but switched to natural science during his first year.

Won Seven-Year Fellowship

With his family's deteriorating finances in mind, he took anatomy courses and finished a Ph.D. degree in that field in 1885. (In the German educational system, a Gymnasium lies somewhere between high school and college levels in the U.S.) Boveri's doctoral thesis was called Beiträge zur Kenntnis der Nervenfasern (Contributions to the Study of Nerve Fibers). His work was recognized as exceptional by faculty at the university, who nominated him for a scholarship, the Lamont Fellowship, that gave him the opportunity to continue study and research and ended up supporting him financially for a period of seven years. This gave Boveri the chance to change his focus once again to the subject that fascinated him the most deeply, biology. And he did not let his faculty supporters down.

Working in the laboratories of the university's zoology department, Boveri plunged into one of the hottest areas of biological research at the time. As with many other scientists, his greatest discoveries were accomplished while he was still relatively young. The scientific understanding of the reproduction of organisms had taken great strides during the years when Boveri was completing his education. Investigators had established that when fertilization occurred, the nuclei of the male sperm and female egg cells fused to form a new nucleus containing material from both, and that this process was central to heredity. The existence of chromosomes was known as well, but the big picture of exactly what happened when sperm and egg united was murky.

Building on the work of the Belgian biologist Edouard van Beneden, Boveri filled in an important part of the picture. His work was done using the comparatively simple organism of the horse roundworm Ascaris megalocephala, which had only a few chromosome pairs. Chromosomes themselves were visible only during mitosis or cell division, and scientists were unsure of the exact role they played at different stages of the reproduction process. But Boveri noticed that the cells of this roundworm showed certain lobes or bulges as they divided, and he kept track of the details of these lobes as new cells were formed from an original cell. What he found was that the lobes seemed to recur in the same order on the surfaces of the new cells, suggesting not only that the chromosomes were present and active throughout the process, but also that they were individual entities whose sequence was important.

This discovery was entirely consistent with what Boveri's friends and associates knew of his particular character as a scientist. He was an observer who combined a scientist's rigor with an artist's eye. "When I sit down at the microscope, I suspend belief," Boveri said (according to his student Fritz Baltzer), and his scientific breakthroughs were based on careful reasoning, working with data obtained from detailed visual observations made without preconceptions.

Published Chromosome Observations

Boveri's discoveries about roundworm cell development were published in installments between 1885 and 1890; the centerpieces were three Zellenstudien (Cell Studies), of which the second (1888) contained his important chromosome observations. The third study extended the observations Boveri made in the second, confirming van Beneden's guess that egg and sperm contribute equal numbers of chromosomes to the new fused nucleus or zygote. He also clarified the role of a structure, which he termed the centromer or centrosome, that formed a temporary center between the halves of a dividing cell. American cytologist Edmund B. Wilson, a student of Boveri's and one of the great biologists of the 20th century, noted that Boveri's experiments provided a working model for almost all cell-based interpretations of genetic phenomena.

During the winter of 1887 and 1888, Boveri worked at a zoological research station in Naples, Italy, operated by the German scientist Anton Dohrn and pleasantly situated on a beach at the city's edge. For Boveri the trip was the beginning of a lifelong love affair with the ancient and scenic southern Italian city—or love-hate affair, for even then Naples was a chaotic place filled with street people and small-time con artists. Boveri would return to Naples in 1889, 1894, 1896, 1901, 1905, 1910-12, and 1914.

Boveri's name was well known in German scientific circles by this time, and in 1887 he had passed his Habilitationsschrift examinations, a kind of postdoctoral dissertation defense that qualified him to teach in a German university. In 1891, as the expiration of his long scholarship approached, Boveri was offered the post of Assistant in the Zoological Institute of the University of Munich by his longtime advisor, Professor Richard Hertwig. Although the post did not allow him to focus full-time on his own specific research interests, he accepted; his father was suffering from what became a terminal illness, and he faced the need to become financially independent. In the fall of 1892, however, a prized zoology professorship at the University of Würzburg became vacant, and Boveri was named to the post the following March. The only cloud on his horizon was the recurrence of an illness, variously described as influenza or neurasthenia, that had begun to trouble him in 1890.

Married American Professor

At Würzburg, Boveri began to attract top students, some of them German but others visitors from foreign countries. One of his students was an American woman, Marcella O'Grady, who was a professor at Vassar College in Poughkeepsie, New York. Her scientific activities stirred up some controversy in the generally all-male world of the German university community, and Boveri's mother was not pleased by her son's growing friendship with his American colleague. Nevertheless, the pair were married in Boston on October 5, 1897, and the new Mrs. Boveri became an active participant in her husband's scientific endeavors. She became well versed in the development of sea urchin embryos, a subject Boveri had begun to study on the beach in Naples, and in 1903 she published a paper of her own on the subject. The couple had one daughter, Margret.

Other famous foreign biologists who came to study with Boveri included Edmund Wilson and Nettie Stevens, whom Boveri (according to the University of Würzburg biology website) disliked and called a "bloodsucker." His appeal to top-flight graduate students was not hard to explain, for confirmations of his observations regarding chromosome individuality came thick and fast after he had pointed investigators in the right direction (and after the work of the unknown Austrian monk Gregor Mendel was rediscovered in 1900 after having been buried in an obscure publication for 34 years). Some of those confirmations came from Boveri himself; he remained active as a scholar for the rest of his life, even as the crush of teaching and administrative responsibilities at the university grew greater.

In 1902 he published a paper summarizing the results of experiments in which he intentionally double-fertilized sea urchin eggs. Boveri surmised correctly that divisions of the egg cells in this situation would tend to leave the new divided cells with unequal numbers of chromosomes, and he observed that the sea urchin embryos that developed after this double fertilization were abnormal. Thus he had further evidence that specific chromosome sets were necessary for the reproduction of organisms. Boveri also hypothesized that cancers resulted from malfunctions in the genetic material of cells, an important step in identifying the nature of a disease that at the time was not well understood. He published many other papers through the 1900s and the first part of the 1910s dealing with cell structure and differentiation.

Boveri had an energetic, even feverish attitude toward his own research and often demanded the same from his students. It was only illness that finally slowed him down. In 1912 he was considered for the directorship of one of Germany's top scientific institutions, the Kaiser Wilhelm Institute for Biology in Berlin, but turned the position down after flare-ups of his intermittent ailments left him partially paralyzed on his right side. He was also distressed by the outbreak of World War I, during which he supported the German cause but correctly foresaw the war's unfavorable outcome. His health deteriorated further. "My wife has from the beginning maintained that the war has made me ill, and perhaps there is something in it," he wrote in a letter quoted by Baltzer. "So many people are dying unexpectedly these days." Gall bladder surgery failed to improve his condition, which manifested itself in fever and lung inflammation. He died on October 15, 1915, and was eulogized by several of the scientists who would soon build on his discoveries and create new branches of science.

Books

Baltzer, Fritz, Theodor Boveri: Life and Work of a Great Biologist (translated from the German by Dorothea Rudnick), University of California Press, 1967.

Gillispie, Charles Coulston, editor in chief, Dictionary of Scientific Biography, Scribner's, 1970.

World of Anatomy and Physiology, Gale, 2002.