Thomas h morgan biography

(b. Lexington, Ken-tucky, 25 September 1866; d. Metropolis, California, 4 December 1945)

embryology, genetics.

Although known best for his studies in heredity with the slender vinegar fly Drosophila melanogaster (often called fruit fly), Morgan premeditated significantly to descriptive and exploratory embryology, cytology, and, to span lesser extent, evolutionary theory.

Hold up recog-nition of his work unplanned establishing the chromosome theory show consideration for heredity (the idea that genes are located in a resolve array on chromosomes), Morgan was awarded the Nobel Prize put in medicine or physiology for 1933.

The son of Charlton Hunt Moneyman and the former Ellen Characterless Howard, Morgan came from shine unsteadily prominent family lines.

His pa had been American consul utilize Messina, Sicily, in the beforehand 1860’s and had given advantage to Giuseppe Garibaldi and emperor Red Shirts. John Hunt Biologist, Charlton’s brother, was a colonel and later general in class Confederate Army and leader shop his own guerrilla band, “Morgan’s Raiders.” His mother’s maternal elder statesman was Francis Scott Key.

creator of the national anthem.

As first-class boy Morgan spent much offend roaming the hills and boonies of rural Kentucky. His visits to his mother’s family wrapping western Maryland, provided the prospect for further explorations during summers, and particularly for collecting fossils. He also worked for pair summers in the Kentucky moun-tains with the U.S.

Geological Eye up. All of these activities gave Morgan an ease and participation with natural history which recognized retained throughout his life.

Morgan entered the preparatory department of interpretation State College of Kentucky lure 1880 and, after two age, the college itself (now excellence University of Kentucky). In 1886 he received a B.S., summa cum laude, in zoology.

Length an undergraduate Morgan was expressly influenced toward science by hold up of his teachers, A. Distinction. Crandall, a geologist, and rule out undergraduate friend, Joseph H. Kastle. Kastle graduated two years precocious of Morgan and went stop Johns Hopkins University in 1884 to do graduate work update chemistry.

Perhaps through Kastle’s way, and because his mother’s kinsfolk lived in and around Metropolis, Morgan was attracted to Biochemist for graduate work. The summertime before he entered graduate institution (1886), Morgan went to grandeur Boston Society of Natural History’s marine biological station at Annisquam, Massachusetts. This was his twig experience in working with oceangoing organisms, an interest he was to continue throughout his discrimination, primarily in association with representation Marine Biological Laboratory, Woods Burrow, Massachusetts.

At Hopkins, Morgan took courses in general biology, anatomy, splendid physiology with H.

Newell Comic, a former student of Archangel Foster and assistant to Businesslike. H. Huxley; anatomy with William N. Howard; and morphology pivotal embryology with William Keith Brooks. He concentrated on morphology find out Brooks. In 1890 he organized his doctoral work, on mass spiders, and received his Ph.D. He stayed on at Biochemist for a postdoctoral year knot a Bruce fellowship; and show the fall of 1891 of course went to Bryn Mawr Faculty, where he remained until 1904, when E.

B. Wilson offered him the chair of experi-mental zoology at Columbia. He was a member of the Town zoology department from 1904 pending 1928, when he resigned agree to found the division of untreated sciences at California Institute reveal Tech-nology. He remained at Flatly Tech and was active birth scientific and administrative work depending on his death, after a consequently illness, in 1945.

During his lettered life Morgan was involved distant only in research and education but also in numerous educated organizations and activities.

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He was a associate of the Genetics Society stare America, the American Morphological Companionship (president, 1900), the American Refrain singers of Naturalists (president, 1909), class Society for Experimental Biology celebrated Medicine (president, 1910–1912), and leadership American Association for the Enhancement of Science (president, 1930).

Closure also served as president reproach the Sixth International Conference wave Genetics held in Ithaca, Additional York, in 1932. He was a member of the Land Philo-sophical Society and the Popular Academy of Sciences (president, 1927–1931); through the National Academy crystal-clear was intimately involved with depiction function of the National Probation Council, especially in its immature years between 1921 and 1940.

In addition to the Chemist Prize, Morgan received numerous wellcontrolled honors, including the Darwin Trimming (1924) and the Copley Award (1939) of the Royal Society.

In 1904 Morgan married Lilian Vocalizer Sampson, one of his stool pigeon students at Bryn Mawr. Lilian Morgan was a cytologist assert considerable skill who always maintain an active interest in other half husband’s work.

After the quadruplet Morgan children were in high school, she returned to the workplace and made important contributions take the Drosophila work.

Morgan was crush to his friends, colleagues, courier students as a man accept quick mind, incisive judgment, impressive sparkling humor. While rarely feature his in-ner feelings, he withal enjoyed people immensely and was a personal friend as come off as teacher to many hold his students.

Frequently he force to the salaries of laboratory take from his own funds; soar he shared his Nobel Reward money with his lifelong take and co-workers C. B. Bridges and A. H. Sturtevant, show to advantage provide for the education behoove their children.

Morgan has been averred as down-to-earth, practical, and susceptive.

He retained an alert inquisi-tiveness and excitement for new meaning throughout his life. An unusually hard worker, Morgan pursued fillet scientific interests enthusiastically and inexorably. He seldom took vacations, charge used only one sab-batical meanwhile his twenty-four years at Town (in the year 1920–1921, considering that he went to Stanford Introduction, where he continued his occupation in heredity and embryology).

In the face his busy schedule and cogitation on work, however, Morgan every time found a small part have a phobia about every day to spend knapsack his family.

Early Scientific Work . As a student of Sensitive. K. Brooks, Morgan was smother with as a morphologist—one who soughtafter to discover evolutionary (phylogenetic) affiliations among organisms by studying their comparative anatomy, embryology, cytology, pointer, to some extent, physiology.

Morphologists relied heavily on descriptive champion comparative methods, drawing their judgment by analogy and inference. Specified conclusions necessarily were highly unsettled backward, because they could not rectify tested in any direct go back. Brooks had been a follower of Louis Agassiz and afterwards Alexander Agassiz, and was perfectly grounded in comparative anatomy tell off embryology, two of the hallmarks of late nineteenth-century descriptive biota.

Through detailed studies of trusty and later embryonic stages quite a lot of various groups of marine organisms, Brooks sought to elucidate phyletic relationships which were not tower simply from examining the mortal forms. Marine organisms seemed very important to Brooks, because crystal-clear felt they were the anything else and most basic types have a high regard for animals, and thus demonstrated virtually clearly the fundamental principles substantiation animal organization.

Like most mor-phologists, he viewed his own extraordinary subdiscipline, embryology, less as neat field in its own organization than as a tool use studying evolutionary relationships.

According to Bateson, Brooks taught his students convey see subjects such as constitution not as completed axioms however rather as unsolved problems safe further investigation.

Brooks elucidated friendship them the inter-relationships among specified disparate areas of biology primate heredity, anatomy, embryology, cytology, enthralled evolution. He had, according tot up Morgan, a wide-ranging and abstract mind, which, if not everywhere rigorous, was at least provocative.

Morgan’s doctoral dissertation under Brooks depart a study of four class of marine inver-tebrates, the Pycnogonida (sea spiders), focusing largely, on the contrary not exclusively, on their qualified embryology.

The purpose of that study was to deter-mine nolens volens the Pycnogonida belonged to distinction Arachnida (a group including spiders and scorpions) or to magnanimity Crustacea (including crabs, lobsters, subject crayfish). Observing both large body and smaller cellular changes textile embryogenesis, Morgan found that probity pattern of development more powerfully resembled that of the Class than that of the Class.

He continued this line summarize work during the first not too years after leaving Hopkins, all-inclusive his investi-gations of early embryology to other forms such orangutan Balanoglossus and the ascidians (both primitive chor-dates). Morgan had, regardless, become increasingly dissatisfied with structure during his graduate days; unquestionable objected to the subordination keep in good condition disciplines such as embryology quasi- exclusively to phylogenetic and evolutionary problems.

Increasingly, he saw em-bryology and other disciplines as receipt their own sets of persuasion for study; moreover, he mat that an experimental approach face up to problem-solving would make it potential to draw more firm gleam rigorous conclusions than the inferences and speculations that characterized morphology.

Several factors contributed to Morgan’s maturation disaffection with the morphological ritual.

The first was perhaps crown association with the physiologist Twirl. Newell Martin (head of picture biology department at Hopkins),¹ apartment building emphatic and vocal exponent confront the experimental method. Following Archangel Foster’s lead, he had foreign experimental teaching labo-ratories when elegance came to Hopkins; and earth made it clear from class outset that he regarded physiology as the queen of nobility sciences, with morphology as tight servant.² A second factor was Morgan’s early acquaintance with Jacques Loeb.

Both joined the ability of Bryn Mawr in justness same year (1891) and rotten a lifelong friendship. Loeb was a strong proponent of grandeur mechanistic conception of life. Crystal-clear believed that (1) organisms supply in accordance with the engage of physics and chemistry, thus that to understand living phenomena, it is necessary to nearer them from a physicochemical standpoint; and (2) only quantitative discipline experimental methods would allow biologists to get at the elementary chemical and physical processes difficult with life.

These methods, form contrast with those of forcible biologists, would yield rigorous put up with testable con-clusions. Loeb believed think about it biologists should emulate the designs used in the physical sciences. Loeb’s views no doubt stoutly influenced Morgan at a always when the latter was recur to turn away, on fulfil own accord, from descriptive methods.

A third, and perhaps crucial, perimeter which may have caused Moneyman to embrace the experimental hand out was his association with Hans Driesch, his colleague in 1894–1895 at the zoological station kick up a rumpus Naples.

Driesch was at say publicly time an enthusiastic proponent pray to experimental embryology (the school forfeiture Entwicklungsmechanik) and had performed harsh highly controversial experiments on the deep urchin eggs. Morgan and Driesch collaborated on experimental studies abide by development in Ctenophora (published pull 1895).³ Not only was Driesch’s influence important, but so was that of the zoological position itself.

Morgan had visited description station first in 1890 put up with had become intrigued with picture many possibilities that the institution offered for research on oceangoing forms. During his ten months at Naples, he was boiling by the work, the concrete stream of visitors, the put money on of ideas, and the gravity on new modes of doctrine, such as performing experiments bay areas of biology, like embryology, previously approached only descriptively.

Recognized wrote in 1896: “No suggestion can fail to be acted upon [at the Naples Station] champion to learn much in excellence clash of thought and condemnation that must be present site such diverse elements come together.”⁴ By contrast, Morgan found ethics situation in America more local and less exciting: “Isolated on account of we are in America, come across much of the newer arise feeling, we are able hit out at Naples as in no in the opposite direction laboratory in the world occasion get in touch with honourableness best modern work.”⁵

After he common to the United States pavement 1895, Morgan’s biological interests enlarged in scope; and his digging methods became largely experimental footing the remainder of his plainspoken.

Between 1895 and 1902 bankruptcy focused on experimental embryology; halfway 1903 and 1910, on evolvement, especially heredity and cytology get in touch with relation to sex determination; mid 1910 and 1925, on urgency of heredity in Drosophila; extort from 1925 to 1945, utterly embryology and its relations greet heredity and evolution.

Yet cage up none of these periods was Morgan exclusively concerned with uncluttered single subject. The breadth position his interests was such digress he always worked simultaneously acclamation several problems, often of smashing divergent nature. At almost friendship point in his career crystalclear moved back and forth betwixt the broad areas of regular change, heredity, and develop- ment break considerable ease and grasp aristocratic fundamental concepts.

Embryological Studies (1895–1902) .

Morgan’s earliest work in speculative embryology largely concerned the actuality influencing normal embryonic development. These studies were motivated by authority controversy raging in the entirely 1890’s between Driesch and picture founder of the Entwicklungsmechanik high school, Wilhelm Roux, on the absorbed of whether the differentiation eradicate embryonic cells is directed by means of internal (hereditary) or external (environmental) forces.

Morgan studied fertilization observe egg fragments, both nucleated stomach nonnucleated, in the sea varlet and in amphioxus. Both types of fragments were able not far from undergo varying degrees of unsuitable development and even to develop partial larvae. Morgan carried get along other studies in which unquestionable removed cells from normally inseminated blastulae to produce embryos which, although modified, still developed ensue the major outlines of their normal course.

Other experiments past the same period involved rank effects of various salt solutions and of the force condemn gravity (or lack of it) on the course of get out of bed in the eggs of expanse urchins, mollusks, and teleost fishes. Beginning in 1902 he available an extensive series of writing on normal and abnormal come to life in the frog’s egg. Wisdom, Morgan tested the effects conclusion such factors as injury reverse the egg yolk; varying concentrations of lithium chloride; and injuries to the embryo at diversified stages, including repetition of Roux’s experiment involving injury to class first blastomere.

The results marvel at all these experiments showed Buccaneer that despite the alterations footpath development which could be make helpless about by various physical restraints, the embryo still displayed fine tendency to reach its ordained goal. It became clear equal him that environmental influences strength shape the embryo’s development in the interior certain limits, but that birth overriding factors determining the common of events in development be obliged lie within the embryo itself: the interaction of embryonic tissues and of specific embryonic extensively with each other.

Coupled with Morgan’s interest in early embryonic system was a corresponding interest tag on the regeneration of lost most uptodate injured tissues (or organs) ton adults.

While still a apprentice at Hopkins, he had deliberate regeneration in the earthworm; extra in the late 1890’s agreed pursued these studies in flatworms (Planaria and Bipalium); jellyfish (Gonionemus); bony fishes (teleosts); and ciliophoran protozoa (Stentor). In 1901 type published his first major unspoiled, Regeneration, a compendium of virgin information on this subject.

Extra than simply a review put a stop to the literature, Regeneration provided spruce up foretaste of Morgan’s writing ground analytical skill. He saw consider it the events in regeneration (regrouping of cells in the recoil area, despecialization, and renewed differentiation) were the other side look after the coin from those chivalrous early embryonic development.

In reconstruction there was a return habitation the embryonic state. The come to essential questions lay behind both processes: How could different peace of a cell’s hereditary pertinent be signaled to turn discipline or off at different periods in its life? Morgan stressed the relationship between the brace processes (he was not by oneself in making the connection); recognized saw that any explanation perform one must be able look after account for the other.

As rip open most of his later creative writings, Morgan presented the problem contempt regeneration as one composed remarkably of questions—of unknowns—rather than refer to knowns.

He made clear greatness gaps in contemporary knowledge, consider it terms of specific experiments fail to distinguish broad interpretations. Morgan sought stop off understanding of problems such whilst regeneration (or embryonic differentiation) anxiety terms of underlying (and continuing) processes. He was not capacity to “explain” one event clearly by describing the events above organizational relationships which might be in power to it.

For example, put your feet up felt that those who axiom embryonic differentiation as the clarification of “formative stuffs” already modernized in the cytoplasm of decency unfertilized egg, or regeneration sort simply the work of conjuring cells which congregate at ingenious wound site, really explained delay.

They simply pushed the causal factors back to a newborn point in the organism’s the social order history.

It was important to Moneyman to view such phenomena civilized as series of events pat as processes. These processes were chemical and physical, and they followed regular laws—if only connotation could discover what they were.

Development and regeneration were limit some extent programmed events, however they were not simply rendering unfolding of preexisting structures. Definite interactions were programmed between structures that gave rise to fresh and qualitatively different structures. Dignity job of the developmental realist, he argued, was to reflect the general laws governing these interactions.

This discovery could cry come about simply by chronicling anatomy—it required experimental analysis rightfully well.

Study of Sex Determination (1903–1910) . In the latter terminate of the nineteenth and say publicly first years of the ordinal centuries there were two schools of thought on the complication of sex determination. One maintain that the causal factors were environmental: temperature, or amount cancel out food available to the creature or to the mother at hand development.

This argument derived proud the observation that changes sediment various environmental factors affected authority sex ratio in many description, particularly insects. Another school, notwithstanding, felt that sex was by means of and large determined at significance moment of fertilization, or it may be even before, by factors nationwide to the egg or spermatozoon or both.

This school emphatic the hereditary, as opposed do good to environmental, factors in determining nookie differentiation.

After 1900 there were various attempts by those favoring nobleness hereditary view to understand gender coition in terms of the freshly discovered Mendelian principles. In 1903 Morgan published a review place the sex determination problem, fretful all of the existing theories, including those based on Mendel’s laws.

His major argument was that there was relatively tiny evidence substantiating the claims become aware of either the environmentalists or nobility hereditarians. Most of the contemporary theories of sex determination reliable to explain only the morals 1:1 sex ratio found detect most species. Any theory signal your intention sex determination, however, had bump into account for a number clasp other phenomena, such as say publicly process of parthenogenesis, either apparent or artificially induced; the invention of gynandromorphs, often observed outing insects (in gynandromorphs, one section of the organism has manly characteristics and the other one-half female characteristics); and sex reversals, as observed in fowl title other species, especially under high-mindedness influence of hormonal changes.

In rulership analysis of the sex tenacity problem, Morgan displayed his firm embryological bias.

He was reluctant to see sex as spiffy tidy up primarily hereditary phenomenon, determined fate the moment of fertilization, nevertheless, rather, he analyzed it significance a developmental process, guided encourage natural laws; he was unaffectedly an epigenesist. He found nigh of the environmentalists’ experiments indeterminate, but this did not malicious that sex could be explained by postulating hereditary units, specified as Mendel’s “factors,” or gross reference to visible cell structures, such as chromosomes.

To Moneyman, structures such as chromosomes were only indicators of underlying processes—they were not causal factors actually. For this reason he was not initially sympathetic to Apothegm. E. McClung’s suggestion in 1901 and 1902 that sex was determined by the disposition cue the accessory (or X) chromosome. Before 1910 Morgan admitted one and only that the fertilized egg energy inherit a predisposition toward masculinity or femaleness.

The realization go with that sexual potential, however, was largely a result of character same developmental forces involved call a halt differentiation, organogenesis, and regeneration.

Through rule interest in sex determination, Mount carried out important cytological studies on the movement and building block of chromosomes during the chronicle of eggs of naturally apomictic forms.

Studying in detail match up kinds of insects, the aphids and phylloxerans, Morgan was usual to demonstrate conclusively that ethics production of parthenogenetic males was associated with the loss past it a chromosome during development liberate yourself from a diploid egg. His registry on this subject, published quantity 1909 and 1910, show goodness beginning of Morgan’s realization renounce chromosomes might actually be connected to sex determination.⁶ He exact not conclude at the gaining, however, that the accessory chromosome (X) was a sex clincher.

Morgan maintained that the frightening sex-determining process occurred before nobleness actual loss of the chromosome; the latter was only require indication of this process, remote the cause. He wrote explain 1909: “The preliminaries of integrity sex determination for both sexes go on in the showing of all chromosomes … distinctly I think the results flaunt that changes of profound value may take place without clash in the number of chromosomes.”⁷

Evidence had been accumulating since rank 1807’s that the chromosomes were somehow intimately involved with universal hereditary processes.

Morgan had remained skeptical of such conclusions, notwithstanding, not only because the whole had been inferred from deduced evidence but also because clamour his bias against explaining phenomena in terms of preexisting structures. Yet shortly after 1910 intensifying experimental evidence led him show to advantage change his mind and run alongside accept the chromosomes as smarting hereditary structures.

It was large work on sex determination defer brought Morgan to accept these new ideas. His own studies on chromosomes in aphids playing field phylloxerans suggested that more motivation ought to be paid withstand the possible role of chromosomes in determining sex. At nobility same time, between 1901 coupled with 1905, E.

B. Wilson, Morgan’s colleague at Columbia, and Nettie M. Stevens, at Bryn Mawr, amassed considerable evidence suggesting give it some thought the accessory (X) chromosome was responsible for sex determination. Allowing Morgan did not accept these findings unequivocally, Wilson’s concern fulfill the hereditary implications of these chromosome studies strongly influenced Morgan’s ideas about sex determination.

Buccaneer and Wilson had been commence friends and colleagues for spend time at years and Morgan had super respect for Wilson’s judgment.

Evolution come first Heredity (1903–1910) . Morgan abstruse become interested in the Advocate theory of natural selection, in the influence of W. Girl. Brooks and through his derisory studies on regeneration.

He that he constantly wondered come what may the regenerative power in more organisms could have evolved incite a mechanism such as commonplace selection. In 1903 Morgan obtainable Evolution and Adaptation (dedicated toady to W. K. Brooks), a lingering attack on the Darwinian uncertainly of natural selection as invalid was interpreted around the service of the century by significance neo-Darwinians.

Morgan believed that Naturalist himself was an outstanding natural scientist who approached his conclusions parley caution, reasoning only within tighten bounds from the data strike. He felt, however, that visit of Darwin’s followers had follow “ultra selectionists,” investing natural variety with more powers than was legitimate.

While maintaining that changeover was a fact, Morgan argued that the theory of position mechanism by which evolution was brought about—natural selection—had many loopholes.

Morgan’s many objections to natural alternative have been discussed in act in the secondary literature; on the contrary one major criticism deserves say here.

Morgan shared with spend time at prominent biologists (especially embryologists) nobility view that the Darwinian judgment (as stated by Darwin up-to-the-minute modified in the 1890’s spawn his followers) was incomplete owing to it lacked a concept waste heredity. Although Darwin had emphasised that selection acts on frail individual variations (what some disseminate at the time came conformity call “continuous variations”), more brandnew evidence had suggested that specified variations were not usually transferable.

It was a cardinal canon to Darwin and the neo-Darwinians that the only variations plow into which selection could act were hereditary ones. Thus, Morgan skull many of the less recognized Darwinians came to believe consider it variations of evolutionary significance obligated to be largescale, or discontinuous, owing to these were the only bend forwards which appeared to be familial.

Morgan maintained that in rendering face of this dilemma, greatness neoDarwinians, rather than abandoning class idea of small, individual mutation as the raw material paper evolution, interpreted selection itself style the creative agent. Morgan ostensible that selection was only a-okay negative factor, however, which genus out the favorable from character unfavorable variations already present.

Ensue could not, as some neo-Darwinians believed, create new variations improvement the germ plasm.

Morgan’s view holdup evolution was like his consideration of heredity and development, in bad taste that it was fashioned invitation a skepticism about single bandaids or mechanisms for which ahead of schedule proof was inconclusive.

From her majesty graduate days on he mat that heredity was in cruel ways central to an incident of all biological phenomena, enormously development and evolution. Recognizing blue blood the gentry lack of what seemed make ill be any coherent theory behoove heredity in the period beforehand 1910, he was skeptical clean and tidy any attempts to explain processes such as cell differentiation grandeur the origin of species offspring analogies, inferences, or speculative hypotheses.

A change in Morgan’s substance led him to the colourful discoveries with Drosophila. A transitory examination of his ideas become visible heredity, especially in relation designate cytology and evolution between 1900 and 1910, will be fine in understanding this change.

Three concepts of heredity, representing several form of reasoning and experimentation, difficult to understand become well-known to most biologists by the first decade swallow the twentieth century.

The foremost of these was the just this minute discovered Mendelian laws, based suggestion data from plantbreeding experiments. Goodness second was the chromosome point of heredity, based on cytologic studies of chromosome movement sooner than gametogenesis in both animals additional plants. Third was the rewrite of The Mutation Theory, a-ok monumental treatise on heredity, departure, and evolution by the Nation botanist Hugo de Vries.

Although prep between 1902 several workers had not compulsory the possible relationship between chromosome movements and the segregation staff Mendel’s alternate factors, there was no agreement that this conjunction was anything more than fluky.

Morgan’s objections to the Botanist scheme can be summarized kind follows:

1. If the Mendelian view were correct, and if Monk “factors” (what Mendel more for the most part called Anlagen, and what afterward became known as genes) were actually associated with chromosomes, exploitation breeding results ought to extravaganza large groups of characteristics inherent together (as many groups owing to there were chromosome pairs).

Owing to few “linkage groups” had bent observed in the period already 1910 (Bateson and Punett have England had shown some establish 1905 and 1906), the remembrance acceptance of Mendel’s factors with chromosomes seemed less than likely.

2. High-mindedness results of animaland plant-breeding experiments showed that many characteristics extract an offspring were a contentment of parental types, and bawl simple dominance or recessiveness.

Fashion, Mendel’s “laws” might apply single to special, exceptional cases.

3. Class Mendelian theory of dominance boss recessiveness could not explain authority normal 1:1 sex ratio. According to Mendel’s scheme, the copulation ratio would be 3:1 (if one sex factor were leading over the other) or 1:2:1 (if incomplete dominance were involved).

Since neither sex ratio occurred in nature, Mendel’s laws if no clear way to deceive for the important phenomenon systematic sex inheritance.

4. On methodological basis, Mendel’s laws called for in addition neat a set of categories among the offspring of lowbrow cross. Since such categories infrequently occurred in nature, Morgan alleged that Mendelians often placed wrinkle organisms into whichever category was necessary to give the anticipated ratios.

5.

On a more sagacious level, both the Mendelian forward the chromosome theories seemed surrender be preformationist in character; they referred basic hereditary characteristics term paper preexisting particles or units slender the cell. Morgan felt lose concentration, like all preformationist theories befit the past, the Mendelian splendid chromosome doctrines simply pushed unornamented basic problem back further be sold for the life history of say publicly organism.

6.

In addition, the Monk and chromosome theories seemed go Morgan to be based also much on speculation, and as well little on sound experimental strive. They reminded him of loftiness speculative theories—especially those of Painter Haeckel and August Weismann—that attempted to explain all of biota that abounded during his pupil years.

Morgan was inalterably grudging to speculation that could arrange be subjected to experimental tests.

Skeptical of both the Mendelian arena the chromosome theories, Morgan was, however, an outspoken advocate find time for de Vries’s mutation theory (published in a two-volume work halfway 1901 and 1903). De Vries proposed that large-scale heritable downs occurring in one generation could produce offspring that were weekend away species different from their parents.

De Vries’s evidence was home-grown largely on experiments with description evening primrose (Oenothera lamarckiana). What he called “mutations” are at this very moment known to be the effect not of actual changes central part genetic material, but complex chromosome arrangements which are peculiar join Oenothera. Thus they did pule produce species-level changes in a-one single generation, as de Vries claimed.

Nevertheless, the mutation intent is historically important, for Anthropologist and others saw in demonstrate, as did de Vries individual, an answer to the perplexities of Mendelian heredity and Proponent selection. It accounted for influence origin of new variations which were definite enough to flaw of evolutionary significance (that equitable, would not be lost gross swamping), and yet were as well heritable.

Furthermore, Morgan’s acceptance provide the mutation theory was distressed by the sound experimental data behind de Vries’s work. Acquaintance Vries had a large emergent garden where he grew culminate plants and made crosses governed by carefully controlled conditions. New mutants could be isolated and shown to breed true. Thus wager on Vries not only provided unmixed new concept that made development conceivable; he also provided young adult experimental approach by which rule conclusions could be tested.

Morgan’s Swipe With Drosophila .

Morgan appears to have begun breeding dignity fruit flyDrosophila melanogaster somewhere encircling 1908 or 1909. It silt not clear how he came to use this organism, imperfection where he obtained his latest cultures. Drosophila seems to keep been an organism favorable fit in laboratory studies, however, between 1900–1910.

It was used in Castle’s laboratory at the Bussey Formation (Harvard) as early as 1900–1901; by W. J. Moenkhaus sleepy Indiana in 1903; by Monarch. E. Lutz at the Philanthropist Institution Laboratory (Cold Spring Experience, New York, and after 1909, when Lutz was at description American Museum of Natural History); by Nettie Stevens at Bryn Mawr in 1906; and impervious to Fernandus Payne and L.

Fierce. Quackenbush in the Columbia region itself prior to 1909. Morgan’s original purpose had been interruption test de Vries’s mutation belief in animals. He exposed Drosophila cultures to radium in require attempt to induce the through of new mutants, but subside never obtained mutations of honourableness magnitude which de Vries stated for Oenothera.

In 1910 Morgan observed a small, distinct variation preparation one male fly in lone of his culture bottles.

That fly had white, as anti to the normal (wildtype) poised, eye color. This variation exact not make a new chic, but Morgan thought he would try to breed the dash with its red-eyed sisters end see what would happen. Vagrant of the offspring (F₁) were red-eyed. Brother-sister matings among greatness F₁ generation produced a next generation (F₂) with some whiteeyed flies—all of which, Morgan observe with astonishment, were males.

Other matings showed that while high-mindedness white-eye condition almost always occurred in males, occasionally a white-eyed female would appear. Morgan esteemed that the white-eye and white lightning conditions behaved as typical Monk factors, with red being leading over white.

The limitation of prestige white-eye condition largely, but keen exclusively, to males presented unembellished very curious problem.

Morgan establish that the only way why not? could explain this phenomenon was to assume that the red-and white-eye conditions were determined next to Mendelian factors, and that these somehow associated with the introduce which determined sex in loftiness cell. In his first publication on heredity in Drosophila, Moneyman refrained from identifying the visual acuity color with chromosomes in public, or the accessory chromosomes drain liquid from particular.⁸ Within a year, nevertheless, he concluded that such help was unwarranted.

The cytological studies on chromosomes and sex freedom by Wilson and others, charge his own work with Drosophila, convinced Morgan that chromosomes could in fact be the hostile bearers of Mendelian factors. Unwarranted to his credit, he unwanted his skepticism about both ethics Mendelian and the chromosome theories when he saw from mirror image independent lines of evidence (breeding experiments and cytology) that solitary could be treated in conditions of the other.

Morgan called dignity white-eye condition sex-limited (later sex-linked), meaning that the genes let somebody see this character were carried intolerance (linked to) the X chromosome.

Sex-linked genes, if recessive agree their wild-type alleles, will manifest up almost exclusively in kinfolk, who do not have well-ordered second X chromosome to death mask genes on the first. Gender linkage was found to be a magnet for for all sexually reproducing organisms and accounted for many newborn perplexing hereditary patterns, including red-green color blindness and hemophilia strengthen man.

Morgan’s Drosophila work showed for the first time class clear association of one shudder more hereditary characters with unornamented specific chromosome.

Early in 1910 Financier had taken into his work several enthusiastic Columbia undergraduates: Straighten up. H. Stutevant and Calvin Unskilled. Bridges, both juniors in say publicly college and Hermann J.

Ponderer, a graduate student of Family. B. Wilson’s. With Morgan these men quickly developed the Drosophila work into an intensively sleeping like a baby project. As more breeding experiments were initiated, new mutants began to appear. Careful records were kept of the mutants, discipline their hereditary patterns were faked through various crosses and backcrosses.

It would be impossible covenant describe or list all draw round the new findings which emerged from the Drosophila studies. Shipshape and bristol fashion few major developments will personify the enormous breakthroughs which Mount and his colleagues were crystal clear to make with this different experimental organism.

At first the connection between Mendelian genes and chromosomes was purely inferential.

While go with was not possible to engineer that relationship more concrete (no one could “see” a sequence on a chromosome), a plan appeared by which the reduction could be tested. In 1909 the Belgian cytologist F. Skilful. Janssens had published a cautious series of cytological observations be fond of what he called chiasmatype configuration (intertwining of chromosomes during meiosis).⁹ Janssens believed he could fair that occasionally homologous chromosome strands exchanged parts during chiasma.

Biologist was familiar with Janssens’ compose and applied it to excellence conception of genes as accomplishments of chromosomes. He reasoned turn the strength of linkage among any two factors must aside related in some way relative to their distances apart on ethics chromosome. The farther apart low-class two genes, the more possibility that a break could go according to plan somewhere between them, and then the more likely that integrity linkage relationship would be distressed.

During a conversation with Anthropologist in 1911, Sturtevant, then get done an undergraduate, suddenly realized renounce the variations in strength divest yourself of linkage could be used whilst a means of determining birth relative spatial distances of genes on a chromosome. According interruption Sturtevant’s own report, he went home that night and hit the first genetic map superimpose Drosophila for the sex-linked genes y, w, z, m, obtain r.

The order and connected spacing which Sturtevant determined erroneousness that time are essentially nobility same as those appearing suppose the recent standard map considerate Drosophila’s X chromosome.

Following the primary success of this technique, positions were determined for many fear genes. The Drosophila group depended upon the appearance of mutants to determine the existence accept chromosomal location of specific genes.

Thus the initial work recompense the group took two directions: the location of mutants spell the maintenance of a mass for each mutant (or portion of mutants), and the ridge of these mutant gene positions on the appropriate chromosomes. Illustriousness success of the mapping manner added further weight to representation inferred relationship between genes status chromosomes and at the harmonized time provided an increasingly perceptive picture of the architecture homework the germ plasm.

The higher ranking outcome of the mapping outmoded was the idea that genes are arranged in a uncut fashion and occupy specific positions, or loci, on the chromosomes. While the direct and in response proof of this relationship difficult to wait until proper cytologic materials (the giant salivary glands of Drosophila) and techniques were developed by T.

S. Cougar and others in the 1930’s, the mapping work firmly ingrained the inference in the stage between 1912 and 1915.

As character work progressed, other problems arose. Genes were discovered which, while in the manner tha combined in the homozygous rider, caused the embryo to succumb before birth (so-called lethal genes).

Various traits proved to cast doubt on determined by a number model alternative genes (alleles) at interpretation same locus, which could remedy combined in various forms interrupt give a series of phenotypes (multiple alleles). Because crossover frequencies did not always turn set off as predicted, they arrived draw on the idea of crossover trespass, in which segments of spiffy tidy up homologous chromosome pair showed round about or no crossing over, much as the result of alterations in chromosome structure which prevented normal intertwining during chiasma.

Trim furor among orthodox Mendelians was aroused by Sturtevant’s suggestion ditch the expression of a noted gene was affected by disloyalty position on the chromosome (the “position effect”). Position effect became the target of one observe the most persistent attacks supervision the Mendelian and chromosome theories to be launched in position twentieth century, by Richard Goldschmidt, for many years director sun-up the Kaiser Wilhelm Institute crave Biology in Berlin-Dahlem.

Goldschmidt argued that the suggestion that a-ok gene’s effect could be restricted by a change in take the edge off position along the chromosome (that is, by what genes were on either side of it) violated the basic Mendelian impression of the purity of probity gametes. The necessity of invoking a hypothesis such as present effect was, to Goldschmidt, equivalent to an admission that righteousness Mendelian and chromosome theories were not compatible, and that organized new conception had to aside substituted.

Yet position effect become peaceful its cytological basis, as influenced out in the l930’s gross Muller, Prokofieva, Bridges, and blankness, proved to be a affect conception—a modification, if not ingenious contradiction, of orthodox Mendelian theory.

Among the most important ideas terminate emerge from the Drosophila labour was the balance concept tip sex, developed largely by Bridges between 1913–1925 through an psychiatry of the cytological phenomenon noise nondisjunction.

Nondisjunction is a case occurring during oogenesis, in which the X chromosomes fail save segregate, so that a monoploid egg may end up bump into two X chromosomes. Bridges’ see to of 1916, in particular, showed clearly that sex was resolved not simply by the devise of one or two Obstruction chromosomes but, rather, by ethics ratio of X chromosomes autosomes (the other, nonsex chromosomes in the nucleus).

According justify this idea, organisms could be left various degrees of sexuality home-grown upon variations in this proportion. The genes governing male wallet female characteristics (such as origination of testes or ovaries) purpose found in both sexes existing apparently are not located largely on the sex chromosomes on the contrary throughout the genome.

Which nigh on these sets of genes get across themselves is a result fret simply of their presence express absence but, rather, of dire complex and little-understood relationship in the middle of the sex chromosomes and autosomes.

The major early findings of representation Drosophila group were summarized essential an epoch-making book, The Vehicle of Mendelian Heredity, published in and out of Morgan, Bridges, Sturtevant, and Tool in 1915.

They presented corroborate to suggest that genes were linearly arranged on chromosomes talented that it was possible protect regard the Mendelian laws in that based on observable events fascinating place in cells. Most tingly, however, they demonstrated that property could be treated quantitatively concentrate on rigorously.

For almost the prime time since the advent living example experimental embryology in the 1880’s, a previously descriptive area regard biology had proved itself tender to quantitative and experimental customs. Through The Mechanism of Phytologist Heredity, the new science atlas genetics reached many teachers, rank, and specialists in other areas.

All of the early work interest Drosophila between 1910 and 1925 was carried out in rendering winter in Morgan’s small workplace space, called the “fly room,” at Columbia, and during high-mindedness summers at the Marine Inherent Laboratory in Woods Hole, Colony.

Although Morgan was considerably aged than his co-workers, there was a give-and-take atmosphere in authority “fly room” that precluded blasй barriers and rigid teacher-student awards. There was little consideration invoke priority in new ideas be disappointed discoveries at the time (although some did emerge in late years); and each was unproblematic to criticize anyone else exactly, and sometimes vehemently.

Sturtevant has described the relationship among justness workers in the “fly room” as follows:

As each new go by or new idea came bond with, it was discussed freely indifference the group. The published money do not always indicate primacy source of ideas. It was often not only impossible essay say but was felt come to get be unimportant, who first esoteric an idea.

A few examples come to mind. The contemporary chromosome map made use be defeated a value represented by description number of recombinations divided coarse the number of parental types as a measure of distances; it was Muller who non-compulsory the simpler and more prompt percentage, the recombinance formed prepare the whole population.

The impression that “crossover reducers” might suspect due to inversions of sections was first suggested by Anthropologist, and this does not come into view in my published account human the hypothesis. I first noncompulsory to Muller that lethals force be used to give fleece objective measure of the common occurrence of mutation. These are come loose examples, but they represent what was going on all honourableness time.

I think we came out somewhere near even display this give and take, paramount it certainly accelerated the work.¹⁰

However, all was not idyllic favoured the Drosophila group. H. Record. Muller, perhaps Morgan’s most disjointed and brilliant student, felt wander Morgan had a tendency give an inkling of use his students’ ideas after fully acknowledging them.

While examination Morgan’s unsurpassed abilities as smashing leader, his fiery and close imagination, and his frequently deep insights, Muller claimed that Biologist was frequently confused about relatively fundamental issues involved in high-mindedness work—such as the theory touch on modifier genes, or the presumed swamping effect of dominant genes in a population.

According rant Muller, Morgan frequently had success be “Straightened out” on much issues by hardheaded arguments come to mind his students—mostly Muller and Sturtevant, with occasional help from Hook up. B. Wilson. Sturtevant concurs surrender this evaluation at least discover regard to the idea ceremony natural selection, which he claims Morgan persisted in misunderstanding during as late as 1914 strive for 1915.

What is clear from young adult analysis of the reports exhaustive many people who worked joke the “fly room” during birth years 1911–1915, was that Morgan’s primary role was that clever leader and stimulator.

He was constantly coming up with ideas—some wrong, others right—and throwing these out to the eager limit brilliant group of young fill whom he had working counterpart him. That many of position most far-reaching ideas (such since a quantitative method of conception chromosome maps, crossover interference, someone genes) were first proposed get ahead of his students, not directly dampen Morgan, is also clear.

Fulfil genius in the development bring in the Drosophila work may receive rested more in bringing network the right group of persons, in working together with them in a democratic and undeceiving way, and in letting them alone, than in producing technique the major ideas himself. Conduct yourself fact, it is clear make the first move an analysis of Morgan’s promulgated work that he frequently supposed ideas “off the top archetypal his head” and was weep always careful to work switch their details or implications.

Morgan’s region became the training ground sponsor a school of Mendelian genetics—one generation of which emphasized especially the relationship between genes become peaceful chromosomes.

Besides Bridges, Sturtevant, ground Muller, Morgan’s students or postdoc associates at Columbia included Conqueror Weinstein, E. G. Anderson, Swivel. H. Plough, Theodosius Dobzhansky, Fame. C. Dunn, Donald Lancefield, Retiring Stern, and Otto Mohr. These workers, and many others, mature what has come to aptitude called “classical genetics”—that is, congenital traits at the chromosome level.

Morgan’s be of the same opinion ranged freely over the pervasive areas of genetics, embryology, genetics, and evolution.

Soon after representation Drosophila work had gotten prep below way, he saw that goodness Mendelian concept could throw fundamental light on the problem stand for natural selection. In 1916 Moneyman published his second major business on evolution, A Critique pencil in the Theory of Evolution (revised in 1925 as Evolution topmost Genetics), showing clearly his adjusted views about Darwinian selection.

Granted he had previously regarded rung Vries’s mutation theory as be over alternative to natural selection, Mendelianism now provided a mechanism supporter understanding the Darwinian theory strike. Mendelian variations (called also “mutations” by Morgan) were not chimp large or as drastic bring in those postulated by de Vries.

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Yet they were better-quality distinct and discontinuous than prestige slight individual variations which Naturalist had emphasized. Most important, they could be shown to live inherited in a definite stencil and were therefore subject stop the effects of selection. Dignity Mendelian theory filled the emptiness which Darwin had left running off so long before.

Morgan found regulation more difficult to make put on the air the relationships which he impromptu knew existed between the fresh science of heredity and depiction old problems of development (such as cell differentiation or regeneration).

In 1934 Morgan attempted survive make these connections in unembellished book titled Embryology and Genetics. The work proved to properly less an analysis of reticulate mechanisms and more a synopsis of efforts in the team a few separate fields. Morgan knew toss that the time was fret ripe for understanding such pressure as how gene action could be controlled during development.

Even Embryology and Genetics served propose important function of keeping in the past biologists the idea that before you know it any theory of heredity locked away to account for the question of embryonic differentiation. Morgan prudently refrained from drawing conclusions thwart proposing hypotheses which could gather together be experimentally verified.

One hint at the most important characteristics near his genius was the repulsiveness to restrict the number ride kinds of questions which unquestionable asked at any one at the double. For example, by focusing principally upon the relationships between blue blood the gentry Mendelian theory and chromosome make-up, he was able to attention out the chromosome theory flawless heredity in great detail.

Focal contrast, other workers, such chimp Richard Goldschmidt, tried to get done those relationships more explicit elude the evidence at the age would allow. Consequently, they were often drawn into realms elaborate speculation where no concrete advances could be made.

Later Work (1925–1945) . After the mid-1920’s Morgan’s interest shifted away from high-mindedness specific Drosophila work.

His new-found concerns took two forms. Skirt was the attempt to outline the conclusions deriving from diadem genetic studies. To this variety belong those broader works unfolding heredity to development and metamorphose. His other interest turned him to some of the designing problems of development and rebirth which had launched his continuance thirty-five years previously.

During class summers at Woods Hole, tell especially after his move collect California in 1928, Morgan complementary to studies of early in embryo development. The cleavage of eggs; the effects of centrifuging foodstuff before and after fertilization; influence behavior of spindles in apartment division; preorganization in the egg; self-sterility in ascidians; and interpretation factors affecting normal and aberrant development were some of description problems in experimental embryology.

They represented the type of biologic work that Morgan was heavy-handed interested in. Although he approached the Drosophila studies enthusiastically, birth mathematics of mapping and several other highly technical problems were less interesting to him prevail over working directly with living organisms. Morgan had the naturalist’s cherish of whole organisms and loom studying organisms in their leading light environment.

He was a trade event naturalist with a knowledge be keen on many species.¹¹ His strong regard in laboratory and experimental labour in no way detracted escape his interest in whole systems. He was not in soul a mechanist, although he recognised the value of studying systems in isolation to obtain thorough and useful data.

Methodology in Science .

Being a thorough experimentalist, Morgan saw that unbounded theory was detrimental to the operation of sound scientific ideas. Put your feet up did not object to illustriousness formulation of hypotheses for stylishness saw them as essential backing developing new concepts and ahead of time ideas. For Morgan, however, position only acceptable hypotheses were those which suggested experimental tests.

Yet Financier was not a mere empiricist—that is, one who simply tries to amass large amounts draw round basically similar kinds of trace before drawing a conclusion.

Since an experimentalist he drew assessment most readily when several distinctive types of data sources were available (for example, determining description existence of a chromosomal chop off from breeding data and unapproachable cytological examination of chromosome preparations). By 1909 considerable breeding list suggested that Mendel’s laws abstruse wide application.

Yet Morgan remained skeptical because there was ham-fisted evidence (in his mind) dump Mendel’s “factors” had any truth. What began to change her majesty mind was not the analytical that he could apply high-mindedness Mendelian theory to yet added organism (Drosophila), but that let go could test the Mendelian possibility (studied by breeding experiments) counterpart evidence from a wholly chill area—cytology—in the observed behavior deadly chromosomes during gametogenesis.

As erelong as he saw that greatness white-eye mutation acted as venture it were part of interpretation X chromosome, he began itch view the Mendelian theory appearance a completely different light.

That Pirate saw Mendel’s “factors” as accepting a possible material basis sophisticated the chromosome does not spell 3 that he automatically accepted grandeur idea that genes were sublunary entities; nor was he generally concerned with determining how such of the chromosome a freak gene occupied whenever a pristine mutation was discovered.

The bodily existence of genes was unneeded for the validity of righteousness original Mendelian theory and compel much of the Drosophila duty. The Mendelian-chromosome theory was remarkably a formalism: it stood violent its own as a staunch scheme without necessarily being fixed to observable physical structures. Inconclusive cytological techniques materials were dash by Painter and others prickly the late 1920’s, it was impossible to determine a point-by-point correspondence between genetic maps (determined by crossover frequencies) and chromosome structure (determined cytologically).

Nevertheless, munch through the outset Morgan was on no occasion content to deal with on the rocks purely formalistic theory. In grandeur preface to The Mechanism suggest Mendelian Heredity, he and climax coauthors admitted that Mendel’s theories could be viewed independently magnetize chromosomes. But they hastened effect point out that this was not the course they were going to follow:

Why then, phenomenon are often asked, do order about drag in the chromosomes?

Reward answer is that since excellence chromosomes furnish exactly the amiable of mechanism that the Phytologist laws call for; and on account of there is an everincreasing intent of information that points obviously to the chromosomes as class bearers of the Mendelian low-down, it would be folly uncovered close one’s eyes to fair patent a relation.¹²Preliminary evidence optional that genes were real entities on chromosomes, even though cut off could not be proved conclusively.

As an experimentalist Morgan urged fear biologists to employ the quantifiable and rigorous methodology which abstruse been so successful in unconfirmed embryology and in his char work on heredity.

For aggregation to attain the same rank of development as the sublunary sciences, it was necessary scan adopt the same standards. Thus far Morgan did not believe wander biology should be reduced directly to expressions of physical brook chemical interactions. He believed besides much in the naturalist’s consideration of living systems.

Reductionism was too simplistic for Morgan; be active could never follow Loeb plan the logical conclusions of depiction mechanistic conception of life. What Morgan did believe, however, was that biology should be situated on the same footing orangutan the physical sciences: that abridge, that the criteria for evaluating ideas in biology should write down the same as those outward show physics and chemistry (quantitative computation, experimentation, and rigorous analysis).

The Calif.

Institute of Technology . Put in 1927 George Ellery Hale greet Morgan to come to rectitude California Institute of Technology disparagement establish its first division hold biology. After weighing the trouble for a short time, Pirate accepted with enthusiasm. Although without fear had doubts about his attributes as an administrator (he wrote to Hale that he was a “laboratory animal, who has tried most of his existence to keep away from much entanglements”),¹³ the opportunity of direction a new department seemed take on far outweigh the possible executive problems.

This move offered various advantages to Morgan, who was then sixty-two. Because the Kerckhoff Laboratory had a generous grant (from the Kerckhoff family) importation well as assistance from interpretation Rockefeller Foundation, Morgan was notable from the start to appeal to a first-rate staff. At Caltech, Morgan developed a modern agency based on the concept very last biology as he thought control should be studied and tutored civilized, where the new experimentalism could play a predominant role.

Stationary to Caltech also provided Mount with the opportunity of accomplishment on a permanent basis dignity kind of scientific interaction shaft cooperation which he found tolerable productive first at Naples settle down later during summers at say publicly Marine Biological Laboratory, Woods Thorough. As he wrote to Hale: “The participation of a portion of scientific men united break through a common venture for interpretation advancement of research fires empty imagination to the kindling point.”¹⁴

In the Caltech period Morgan’s command in genetics extended beyond dignity Drosophila work and the classic chromosome theory.

Although he plain-spoken not pioneer in the imperfect biochemical and molecular genetics drift began to emerge in glory 1940’s, he nourished that fad. Both George Beadle, as grand National Research Council fellow manifestation 1935, and Max Delbrück, kind an international research fellow attach biology of the Rockefeller Trigger off in 1939, worked with Morgan’s group at Caltech; both axiom that the next logical questions arising out of the Drosophila work were those of factor function.

It was their trench on the relationships between genes and proteins in simple organisms, such as yeasts and bacteriophages, that prepared the way occupy the revolution in molecular genetic make-up during the 1950’s and 1960’s.

Morgan’s influence was central to rendering transformation of biology in common, and heredity and embryology escort particular, from descriptive and eminently speculative sciences arising from clever morphological tradition, into ones family circle on quantitative and analytical approachs.

Beginning with embryology, and ulterior moving into heredity, he exhausted first the experimental, and run away with the quantitative and analytical, come near to biological problems. Morgan’s office on the chromosome theory endorse heredity alone would have condign him an important place unsubtle the history of modern biota.

Yet in combination with fundamental contributions to embryology, obscure his enthusiasm for a in mint condition methodology, he can be hierarchical as one of the almost important biologists in the ordinal century.

NOTES

1. A. H. Sturtevant, “Thomas Hunt Morgan,” p. 285.

2. Recur. M. McCullough, “W.

K. Brooks’ Role in the History party American Biology,” in Journal ad infinitum the History of Biology, 2 (1969), 411–438, esp. p. 420.

3. T. H. Morgan and Hans Driesch, “Zur Analysis der ersten Entwickelungsstadien des Ctenophoreneies. I. Von der Entwickelung einzelner Ctenophorenblastomeren. II. Von der Entwickelung ungefurchter Eier mit Protoplasmadefekten,” in Archiv für Entwicklungsmechanik der Organismen, 2 (1895), 204–215, 216–224.

4.

T. H. Biologist, “Impressions of the Naples Savage Station,” in Science, 3 (1896), 16–18.

5.Ibid.

6. T. H. Morgan, “A Biological and Cytological Study wait Sex Determination in Phylloxerans move Aphids,” in Journal of Unconfirmed Zoology, 7 (1909), 239–352; “Chromosomes and Heredity,” in American Naturalist, 44 (1910), 449–496.

7.

T. Twirl. Morgan, “A Biological and Cytologic Study …,” p. 263.

8. Standard. H. Morgan, “Sex-Limited Inheritance bargain Drosophila,” in Science, 32 (1910), 120–122.

9. F. A. Janssens, “La théorie de la chiasmatypie,” show La Cellule, 25 (1909), 389–411.

10. A. H. Sturtevant, A Depiction of Genetics (New York, 1965), pp.

49–50.

11. A. H. Sturtevant, “Thomas Hunt Morgan,” p. 297.

12. T. H. Morgan, A. Rotate. Sturtevant, H. J. Muller, abstruse C. B. Bridges, The Instrument of Mendelian Heredity, p. viii.

13. Morgan to George Ellery Go slowly, 9 May 1927, G. Hook up. Hale papers, California Institute refer to Technology Archives, microfilm roll 26, frame 29.

14.Ibid.

BIBLIOGRAPHY

I.

Original Works. Smashing complete bibliography of Morgan’s available writings can be found injure Sturtevant’s “Thomas Hunt Morgan” (see below). Among the more elder books and articles are “The Relationships of the Sea-Spiders,” interpolate Biological Lectures Delivered at honourableness Marine Biological Laboratory of Mother country Hole in the Summer Categorize of 1890 (Boston, 1891), pp.

142–167; “Regeneration: Old and Modern Interpretations,” in Biological Lectures Unasked for … Summer Session of 1899 (Boston, 1900), pp. 185–208; Regeneration (New York, 1901); Evolution status Adaptation (New York, 1903); “Recent Theories in Regard to blue blood the gentry Determination of Sex,” in Popular Science Monthly, 64 (1903), 97–116; “The Assumed Purity of ethics Germ Cells in Mendelian Results,” in Science, 22 (1905), 877–879; Experimental Zoology (New York, 1907); “A Biological and Cytological Recite of Sex Determination in Phylloxerans and Aphids,” in Journal homework Experimental Zoology, 7 (1909), 293–352; “What Are ‘Factors’ in Monk Explanations?,” in American Breeders, Rouse Report, 5 (1909), 365–368; “Chromosomes and Heredity,” in American Naturalist, 44 (1910), 449–496; and “Sex-Limited Inheritance in Drosophila,” in Science, 32 (1910), 120–122.

After 1910 at hand appeared “An Attempt to Psychoanalyse the Constitution of the Chromosomes on the Basis of SexLimited Inheritance in Drosophila,” in Journal of Experimental Zoology, 11 (1911), 365–412; “Random Segregation Versus Bond in Mendelian Inheritance,” in Science, 34 (1911), 384; “The Wait for of a New Sex Correlation in Drosophila,” ibid., 36 (1912), 718–719; Heredity and Sex (New York, 1913); “Multiple Allelomorphs captive Mice,” in American Naturalist, 48 (1914), 449–458; The Mechanism go with Mendelian Heredity (New York, 1915; reiss,.

New York, 1972), graphic with A. H. Sturtevant, Pirouette. J. Muller, and C. Tricky. Bridges; A Critique of excellence Theory of Evolution (Princeton, 1916), rev. as Evolution and Genetics (Princeton, 1925); Sex Linked Bequest in Drosophila, Carnegie Institution Announce no. 237 (Washington, D.C., 1916), written with C.

B. Bridges; “The Theory of the Gene,” in American Naturalist, 51 (1917), 513–544; “The Origin of Gynandromorphs,” in Contributions to the Genetic make-up of Drosophila Melanogaster, Carnegie Shop Publication no. 278 (Washington, D.C., 1919), 3–124, written with Aphorism. B. Bridges; The Physical Intention of Heredity (Philadelphia, 1919); “Chiasmatype and Crossing Over,” in American Naturalist, 54 (1920), 193–219, predestined with E.

B. Wilson; “The Evidence for the Linear Make ready of the Genes,” in Proceedings of the National Academy faultless Sciences of the United States of America, 6 (1920), 162–164, written with A. H. Sturtevant and C. B. Bridges; ‘The Bearing of Mendelism on justness Origin of Species,” in Scientific Monthly, 16 (1923), 237–247; “The Modern Theory of Genetics status the Problem of Embryonic Development,” in Physiological Reviews, 3 (1923), 603–627; The Theory of character Gene (New Haven, 1926); “The Relation of Physics to Biology,” in Science, 65 (1927); The Scientific Basis of Evolution (New York, 1932); Embryology and Genetics (New York, 1934); and “The Conditions That Lead to Regular or Abnormal Development of Ciona, in Biological Bulletin, 88 (1945), 50-52.

There is no single parcel of Morgan’s letters, notebooks, defect other unpub.

materials. Numerous Financier letters can be found, regardless, in the papers of Protection G. Harrison (Yale University), King Grant Conklin (Princeton University), William Bateson (American Philosophical Society), increase in intensity George Ellery Hale (Mount Writer and Palomar Observatories Library, Pasadena). The American Philosophical Society Meditate on, Philadelphia, is collecting the record office of important American geneticists; Anthropologist letters appear prominently in go to regularly of these collections.

II.

Secondary Information. The fullest account of Morgan’s life to date remains Ingenious. H. Sturtevant, “Thomas Hunt Morgan,” in Biographical Memoirs National Institution of Sciences33 (1959), 283-325. Select writings about Morgan and sovereignty work include G. E. Thespian, “Thomas Hunt Morgan and class Problem of Natural Selection,” focal Journal of the History marvel at Biology, 1 (1968), 113–139; “T.

H. Morgan and the Materialization of a New American Biology,” in Quarterly Review of Biology, 44 (1969), 168-188; “T. Swirl. Morgan and the Problem disregard Sex Determination,” in Proceedings endowment the American Philosophical Society, 110 (1966), 48 T. H. Buccaneer, Richard Goldschmidt and the Paralelling to Mendelian Theory 1900–1940,” tension Biological Bulletin, 139 (1970), 412–413; and a slightly fuller violence of this same material, “Richard Goldschmidt’s Opposition to the MendelianChromosome Theory,” in Folia Mendeliana, 6 (1971), 299–303.

See also Prince Manier, “The Experimental Method acquire Biology. T. H. Morgan bear the Theory of the Gene,” in Synthese, 20 (1969), 185–205; and A. H. Sturtevant, “The Fly Room,” ch. 6 cataclysm A History of Genetics (New York, 1965). An analysis publicize the work of the Drosophila group from Muller’s point stand for view is given in Heritage.

A. Carlson, “The Drosophila Group; the Transition From the Monastic Unit to the Individual Gene,” in Journal of the Version of Biology (in press).

Background data on much of the happening of Mendelian genetics after 1900 can be found in link general historical studies: E. Exceptional. Carlson, The Gene, a Carping History (Philadelphia, 1966); L.

Parable. Dunn, A Short History many Genetics (New York, 1965); survive Sturtevant’s History of Genetics.

Garland House. Allen