An Interview with Manuel F. Varela and Ann F. Varela: The Fly Room and Thomas Hunt Morgan: Who was he, and what did he investigate?

Nov 25, 2020 by

This was clearly a mutant and destined to become the most famous insect in scientific history.”

—Ian Shine and Sylvia Wrobel

There are three kinds of experiments—those that are foolish, those that are damn foolish, and those that are worse than that!”

—Thomas Hunt Morgan

Excuse my big yawn, but I just came from one of my own lectures.”

—Thomas Hunt Morgan

Michael F. Shaughnessy

1) Thomas Hunt Morgan—when and where was he born?

Thomas Hunt Morgan is considered one of the founding parents of modern genetics, which involves studying genes and their inheritance by new generations of living organisms. Charlton Hunt Morgan and Ellen Key Howard Morgan welcomed Thomas Morgan into their family on September 25, 1866.

The family home was in Lexington, Kentucky. Morgan has a curious family lineage. His father’s family traces back to confederate General John Hunt Morgan and the first millionaire west of the Allegheny Mountains, John Wesley Hunt. His mother’s grandfather was Francis Scott Key. After the Civil War, Morgan’s family struggled to find employment, as they were involved with the Confederacy. Eventually, his father was able to organize veteran reunions.

2) Now, I understand Morgan’s childhood was full of collecting all kinds of specimens, and his early days were full of explorations and examinations. What do we know about this and his early education?

Like many other scientists, Morgan showed a fascination for natural history as a youth. As early as ten years old, Morgan began collecting birds, birds’ eggs, and fossils while living in the country.

Morgan graduated from the University of Kentucky (known then as the State College of Kentucky) in 1886 with his B.S. degree. Morgan’s courses were heavily concentrated on science and mostly natural history.

His postgraduate studies brought him to Johns Hopkins University in Maryland, where he studied morphology under the tutelage of W. K. Brooks, and physiology with H. Newell Martin. His thesis work was focused on the embryology of sea spiders.

In 1887, Morgan worked in the laboratory of Alphaeus Hyatt near the coastline at Annisquam, Massachusetts.

In 1890 during the summer at the Marine Biological Laboratory (MBL) in Woods Hole, Massachusetts, Morgan spent some time studying mutations in mice. Soon after that, he earned his Ph.D. degree at Johns Hopkins University. Having been awarded the Adam Bruce Fellowship, he was off to Europe, Jamaica, and the Bahamas to conducted further research.

3) Morgan’s doctoral work was done not far from his birth—what did he study, and under who?

Morgan’s doctoral studies at Johns Hopkins dealt primarily with descriptive embryology. Starting in 1886, Morgan took a course in physiology taught by the biology department chair Dr. Henry Newell Martin. Professor Martin would influence Morgan on the principles of Darwin and evolution. Morgan also took a course in morphology taught by Professor William K. Brooks, who would become Morgan’s Ph.D. thesis graduate advisor. Brooks was an American and a noted zoologist and naturalist. Under Brooks, Morgan learned about the experimental approach to studying biology—using carefully designed experiments and data collection to test new hypotheses. Morgan also acquired the ability to change his mind if new data indicated that he was wrong about an idea. This style of thinking would later help him be a true convert to the notion of Mendelian genetics in later years.

Meanwhile, Morgan soon focused on embryology. He studied organismal development at the physiological and cellular levels, starting from an egg’s fertilization. His first publication was a short two-page article on the degradation of cockroach eggs’ outer layers using chitin solvents. Morgan then moved to new projects dealing with a variety of organisms. He studied the embryology of worms, frogs, and crabs. Morgan focused on their morphological descriptions and form development. Morgan published these works, as well, in serval prominent journals of the day, including the coveted American Naturalist.

While still a Johns Hopkins graduate student, Morgan went to Woods Hole (formerly Wood’s Holl), Massachusetts. Woods Hole was a tiny seaside resort village. Here, Morgan continued his work at the Marine Biological Laboratory (MBL), which was affiliated with the Baltimore campus at Johns Hopkins. Morgan studied the genus Pycnogonum, commonly known as the “sea spider,” because of its long spidery-like legs. Once complete, Morgan presented the work at an MBL-sponsored lecture series in 1890. The new study was published as a 76-page article in the university-sponsored journal titled “Studies from the Biological Laboratory of the Johns Hopkins University.” One source reported that the paper’s lengthiness nearly bankrupted the journal’s coffers. In any case, Morgan’s entire dissertation project was successfully defended. In the spring of 1890, Thomas Hunt Morgan was granted a Ph.D. from John Hopkins University.

An associate professor of biology position awaited Morgan in 1891 at Bryn Mawr College for Women. He taught all of the morphology-related courses and conducted research there for thirteen years. His research dealt with sea acorns, ascidian worms, and frogs.

With a year’s sabbatical to conduct research, he worked at the Marine Zoological Laboratory (Stazione Zoologica) in Naples. There he met Hans Driesch and Curt Herbst, who undoubtedly influenced him to expand his studies to include experimental embryology.

In 1904, Morgan married Lilian Vaughan Sampson, a student at Bryn Mawr College, who often assisted him in his research. During the same year as his marriage to Lilian, Morgan was appointed professor of experimental zoology at Columbia University in New York. The Morgans had one son and three daughters. Lilian Vaughan Morgan would make many educational and scientific contributions in physiological embryology while at the MBL in Woods Hole.

4) Morgan’s most generative period was at Columbia, where he spent 24 years—what was his life’s work there all about?

Morgan’s next appointment was at Columbia University in New York, where he was Professor of Experimental Zoology. As you point out in your inquiry, his scientific contributions there were considerable. For twenty-four years, Morgan’s attention was focused on cytology’s relevance to the far-reaching characteristics of biological understanding.

His most significant studies at Columbia involved mutant fruit flies, Drosophila melanogaster. The Morgan research laboratory, room 613 of Schermerhorn Hall, a six-story building housing the Biology Department, at Columbia University, was affectionately called “The Fly Room.”

The laboratory was a small room, with eight desks and a center table for media preparations. The flies were cultured in vials containing fly cultures, a medium, and agar. See Figure 59. The Fly Room was crowded with laboratory workers and loose flies. Seldom were the escaped flies ever bothered with in terms of controlling them. It seemed rather hopeless to try managing the escapees because they would soon be replaced with additional fly escapees. A hanging stalk of bananas greeted visitors at the laboratory’s entrance. The bananas, which, when mixed with agar, were the preferred culture media of the fruit flies. Another characteristic of the Fly Room was the atrocious smell of rotting bananas. The fermenting bananas were a source of complaint by many associates who worked in the building.

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Figure 59. Drosophila larva and their culture media.

The Fly Room enjoyed other permanent dwellers: cockroaches. They were dedicated residents of the agar stocks. The cockroaches loved living in the agar, and they lived in the laboratory’s desk drawers. A lab worker and student of Morgan was Curt Stern. In later years Stern reported that the lab workers learned to look away while opening drawers to give the cockroaches time to scurry away into the dark! The Fly Room was infested with mice, too. Stern related another story that he once told Morgan that if he stomped his foot immediately, he would get a mouse—Morgan did.

Another story of the Columbia years deals with Morgan’s correspondence. Opened mail would form a large stack on Morgan’s desk. Periodically, Morgan would transfer the stack to a nearby student’s desk. When Morgan left the room, the stack would be moved back. For a time, the mail stack would be moved back and forth in this manner. One day the pile was thrown unceremoniously into the trash—the mail stack was said to have contained unopened letters.

The Fly Room had two morgues. One of the morgues had fly corpses deposited in a jar of oil. The second morgue was located on Morgan’s desk, and it consisted of a porcelain plate. Morgan’s morgue contained squashed and moldy fly carcasses. If anyone cleaned his morgue, as was periodically done by students’ wives, Morgan would quickly replenish it with more dead fruit flies.

Morgan was not concerned with his appearance. He was often disheveled, and he was known to delight in shocking others about it. He frequently wore tattered clothes, and he was once mistaken for a building custodian. Yet, Morgan was a founding establisher of modern genetics.

As you alluded above in your question, the contributions to the field of genetics by Morgan and his Fly Room workers was monumental. Their work touched on the very nature of the fly gene itself. Morgan’s work was relevant to gene combinations, which was Morgan’s phrase for linked genes, i.e., genes that resided closely together in a fly’s genome. Morgan was astute in finding associations between linked genes and their modes of segregating from each other during gametogenesis, a process of producing sex cells such as sperm and eggs during meiosis. Morgan discovered that the fruit fly’s chromosomes could harbor many genes, which determined their various fly traits. Lastly, the Morgan Columbia laboratory was able to assemble a genome map of the fly, which in itself is considered a monumental contribution to science, especially in genetics. Consequently, Morgan’s studies performed during the Columbia years established him as a founder of genetic’s fledgling discipline.

In 1928, Morgan accepted the Director of the G. Kerckhoff Laboratories position at the California Institute of Technology, at Pasadena. The Caltech years and the Morgan laboratory would similarly serve as a highly sought after locale for many young scientists seeking to learn molecular biology.

5) Morgan was awarded the Nobel Prize in 1933—specifically, what did the Nobel Prize Committee feel he did to receive this award?

Indeed, Thomas Hunt Morgan took the coveted Nobel Prize in 1933 in the Medicine or Physiology category for his scientific contributions to the chromosome theory of genetic inheritance. He had been nominated twice before, in 1919 and 1930, but did not receive the accolade. In 1933, however, Morgan was the sole recipient.

However, the start of Morgan’s work towards the Nobel was embroiled in controversy almost immediately upon arrival at Columbia University, where he had established the Fly Room. One dispute involved whether Gregor Mendel had been correct about his ideas for genetic inheritance. Initially, Morgan believed that Mendelian genetics was untrue. He would eventually change his mind with a history-changing arrival of an individual insect to his fly room.

In May of 1910, the historical event was the appearance of one fly, a mutant, in the Morgan laboratory. The mutant male fly had white eyes. All other flies in Morgan’s fly room had red eyes. The white-eyed mutant fly would alter the course of genetic and molecular biological history. See Figure 60.

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Figure 60. By Morgan T. H., Sturtevant A. H., Muller H. J., Bridges C. B. – Morgan T. H., Sturtevant A. H., Muller H. J., Bridges C. B. The Mechanism of Mendelian Heredity. – New York: Henry Holt and Company, 1915. Page 19, Public Domain.

The other conflict that Morgan was embroiled in centered on the driving force of specific fly traits, such as sex determination, eye color, body size, wing shapes, etc. One postulate held that male and female flies were determined by conditions in the environment, like food or temperature. The other postulate maintained that sex determination was inherited from generation to generation.

The mutant fly, with its white eyes, was studied genetically. Morgan and his graduate student, Fernandus Payne, conducted a series of mating experiments of the white-eyed mutant fly with wild-type females having red eyes. See Figure 61. The first mating was between the parental flies, i.e., the “P generation,” consisted of the white-eyed male mutant and the red-eyed female. The mating produced over 1,240 offspring, the so-called first filial generation, the “F1 generation,” all of whom had red eyes—except for three white-eyed individuals—more on this later. Morgan concluded that the red-eye color was dominant. Intriguingly, the ratios of eye color phenotypes in the new generations produced by the mating of offspring closely resembled the Mendelian genetics model.

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Figure 61. Diagram of reciprocal crosses between individual red-eyed (W+) and white-eyed (W) Drosophila in Morgan’s genetic experiments. In the sex-linked mode of inheritance, the alleles on the sex chromosomes (XY) are inherited following the rules of Mendelian-based patterns.

These offspring, the F1 generation, with mostly red eyes, were mated to each other. This F1 by F1 cross-mating produced an F2 generation. This new generation, the F2 flies, were 4,252 in total number. Of these F2 fruit flies, 3,470 had red eyes, and 782 had white eyes. The ratio of white eye color versus red eyes was suggestive of a Mendelian model for genetic trait inheritance.

Furthermore, Morgan found that the F2 individuals’ white eyes occurred only in male flies, in about half of the male offspring. Morgan reasoned that the red-eye gene (W+), called factors at the time, was located on the chromosome in a close physical location to the gene factor (X) that specified the sex of the flies. Morgan discovered an eye color gene, W, was linked to the sex determination gene, X.

Though it took Morgan awhile to accept it, the X genetic element was considered a sex-linked gene. In other words, the X gene was on the X-chromosome. That two gene factors, W and X, were linked (Morgan called them “combined”) to each other was another significant discovery.

The data were published in the 32nd volume of the journal Science in July of 1910. Morgan would later faithfully reproduce a famous diagram of the findings in his book “The Physical Basis of Heredity.” See Figure 62.

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Figure 62. Pages from The Physical Basis of Heredity, pp. 168-169, by Thomas Hunt Morgan.

Let us get back to the F1 data in which three white-eyed flies were produced. While it is unclear why all progeny were not red-eyed, as Mendelian genetics had predicted, some explanations are postulated. One possibility is that the three white-eyed flies had been contaminants that entered the culture test tubes, where the flies were kept. Another idea is that the white-eyed flies were new mutants.

Other significant discoveries produced in Morgan’s fly laboratory at Columbia involved the fundamental nature of the gene. At the time of the 1910 Science article’s appearance, it was widely known that flies had four chromosomes. It was also believed that males had a Y chromosome and females had an X chromosome. Further, it was thought, inaccurately, that each of these chromosomes specified one trait. The problem with this notion was that fruit flies were observed to have too many characteristics to account for the limited number of chromosomes. Morgan reasoned that more than one factor, i.e., many genes, were located within a given chromosome. That is, chromosomes harbored many genes. This insight proved to be accurate.

Another significant discovery that emerged from the Morgan laboratory at Columbia involved his student Alfred Henry Sturtevant and segregation behaviors of combined, i.e., linked, genes. The new finding was that the linked genes segregated less often during gamete formation by meiosis. Morgan and Sturtevant found additional genes for sex determination, but they failed to segregate together with the X chromosome. He reasoned that the new genes were far apart, perhaps even on a separate chromosome.

Fortunately, genetic crossings could readily be performed. The data would shed light if their degrees of independence from chromosome segregation were measured. For instance, if two linked genes segregated with low frequency, it meant they resided physically close together along the chromosome. If the two linked genes showed higher segregation levels, then it indicated that they were located farther apart on the chromosome. However, if the genes showed complete independence from segregation, then the genes were found in entirely different chromosomes. Later evidence definitively indicated that many genes were located on altogether different chromosomes, just as Sturtevant and Morgan had postulated.

Starting with his lab assistant Sturtevant, Morgan, and others like Hermann Joseph Muller and Calvin B. Bridges would make another significant scientific contribution to genetics. They constructed a gene-map of the fruit fly genome. Using gene-linkage analyses and cross mating, they discovered how closely located certain genes for specific fly traits were connected along the individual chromosomes’ length. The gene mapping was a monumental undertaking, and it would spur other investigators to produce genome maps for many new organisms. The effort culminated in 2003 with a map of the human genome.

Interestingly, Morgan would refuse to attend the Nobel banquet commemorating Alfred Nobel on his December 10 date of birth. Morgan’s reasons for the refusals were wide-ranging. They included a dislike of the formal dress code. He said he simply could not leave the work behind. He was too busy establishing a new genetics program for biochemists. However, the likely reason was that Morgan learned of an alarming “rediscovery” of colossal fly chromosomes. Morgan had been eager to learn more about these giant chromosomes. In any case, Morgan would attend the requisite banquet during the following year.

6) Some of Morgan’s collaborators and co-workers deserve recognition—who were some of them, and what did they discover?

After the successes garnered with fly genetics, Morgan’s Fruit Fly Room became a calling beacon for many young investigators. Prominent among these was Alfred Sturtevant, who arrived in Morgan’s laboratory at Columbia University as a teenaged undergraduate student. Sturtevant would be a key investigator who pioneered the construction of the Drosophila melanogaster genome map.

Another young investigator was Calvin Bridges, who started as a bottle washer in Morgan’s Fly Room. Bridges later featured prominently in work dealing with the crossing over frequencies. One crossover event at a specific chromosome location would less frequently undergo a second crossover event near the first one. Bridges and Morgan called the phenomenon “interference.” Mr. Bridges was reported to have been involved in several scandals involving his personal life. Morgan was said to have played father figure to the young scientist.

When Morgan took the Nobel, he shared half of his monetary award with his children. The other half, he split between Sturtevant and Bridges. To Sturtevant, Morgan wrote a note accompanying the Nobel money that it was a gift for his (Sturtevant’s) children. Young Bridges was said to have used the bequest from Morgan to build a new automobile.

Hermann Joseph Muller, another young member of the Fly Room workers, had studied fruit fly wings and their genes as a graduate student under Morgan in the Ph.D. degree program at Columbia University. Muller would grow critical of Morgan, and they frequently had less than a close association. Muller would garner a Nobel of his own in 1946, involving his genetic mutation work. The Nobel nod would be only the second one bestowed to a geneticist—Morgan was the first.

The work of Morgan had inspired Max Delbrück. A great scientist in his own right, Delbrück was reported to have chosen Caltech as an institution to do his research because of Morgan’s example and his many successes with Drosophila genetics. At Caltech, Delbrück was tremendously successful in his studies of viral replication and genetic structure.

George Beadle, who had pioneered the so-called “one gene-one enzyme” hypothesis, had written fondly about Morgan. In an autobiographical essay, Beadle wrote that during the Great Depression, his Caltech salary was reduced by a third to $1,500. Beadle discovered years later that it had been Morgan all along who had provided the salary with his private money. Like Morgan and Delbrück, Beadle would earn a Nobel Prize. In short, Morgan would inspire new generations of young geneticists and molecular biologists, a multitude who never met Morgan but read of his exploits in famous biographies. One compelling memoir, in particular, penned by Ian Shine and Sylvia Wrobel, was titled “Thomas Hunt Morgan: Pioneer of Genetics.”

7) Regeneration and the hermit crab seemed to follow his career—why is “regeneration” an essential construct in science and his career?

Morgan’s educational foundations were rooted in Darwinian’s notion of evolution, natural selection, and adaptation led to his scientific contributions to the field of regeneration. He developed an interest in grafting and regeneration during his Bryn Mawr years. Morgan studied worms, tadpoles, and fish. At Woods Hole, he spent time studying Asterias forbesii, known as sea stars. These organisms are famously known to regenerate intact individuals from a severed arm.

Morgan’s work with the famous hermit crab, Eupagurus longicarpus, was trendy. He observed that their two front crab legs could regenerate at their breakage points, especially in natural conditions. If these crab legs had become injured, the legs would fall off at the injured points. If severed by amputation under laboratory conditions using scissors, the leg stump would faithfully regenerate a new leg portion. He further found that the regeneration was possible regardless of whether hermit shells protected the severed parts. Such work was at odds with another investigator, August Weismann. Earlier, Weismann had erroneously postulated that regeneration was an evolutionary adaptive response, rather than a fundamental one to embryogenesis and growth, as Morgan had maintained.

He would repeatedly return to his regeneration work as a hobby of sorts for the rest of his career, publishing periodically on his findings, even immediately before his death in 1945.

At Caltech, Morgan studied the salamander of the genus Triturus. He was also interested in echinoderms known as brittle stars. Widely regarded as a regeneration expert, Morgan was invited to deliver lectures on the topic he developed into a book, Regeneration (1901). Morgan had gained an insight dealing with gradients and morphogenesis during regeneration. He had demonstrated that neuronal tissue was necessary for regeneration to proceed to completion.

Translating these sorts of studies by Morgan to the regeneration of lost or new human tissue is still a long way off. The conditions that favor regenerative growth in Morgan’s test subjects lack specific inhibitors of new tissue growth. In humans, growth inhibitory factors are continuously present. Significant differences exist between severed versus crushed spinal cords, with the latter being more common and problematic.

There is a tremendous interest in the regeneration of nerve tissue from spinal cord injuries. Studies of severed spinal cords in laboratory rats have a limited degree of promise with nerve implants and nerve growth proteins like fibroblast growth factor, which can encourage new axonal connections. However, unlike the case with hermit crabs, growth inhibitory factors are confounding elements in the spinal cord, and they prevent nerve growth outside of the implants. The nerve growth implants have benefited more recently from fibrin, which has permitted new connections between the implants and spinal cord ends. However, most of the laboratory rats are still unable to walk or even stand. Sadly, much more cell and molecular studies need to be performed before tissue regeneration is feasible in many human tissues.

One exception is the human liver. Loss of significant liver sections can be restored with the growth of new liver tissue by hepatocyte growth factor (HGF). This protein starts the development of new liver cells after hepatectomy, the surgical removal of liver tissue.

8) His later years—what did he investigate or write about?

Morgan wrote: The Scientific Basis of Evolution (2nd. ed., 1935), Experimental Embryology (1927), The Theory of the Gene (1926), Evolution and Genetics (1925), Embryology and Genetics (1924), The Physical Basis of Heredity (1919), and Heredity and Sex (1913), all of these being widely considered classics in the literature of genetics. During his notable career, Morgan authored 22 books and 370 scientific papers. Because of his work, Drosophila became a primary classic organism in modern-day genetics.

In 1919, Morgan became a Foreign Member of the Royal Society of London, and in 1922 he delivered the Croonian Lecture. In 1924, Morgan was bestowed the Darwin Medal. Morgan was given the 1933 Nobel Prize for his discoveries concerning the nature of fly chromosomes and how they are associated with heredity. In 1939, Morgan received the Copley Medal.

For biographical information regarding this parent of genetics, Thomas H. Morgan, visit:

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