Bridges, Calvin Blackman

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Bridges, Calvin Blackman

(b. Schuyler Falls, New York, 11 January 1889; d. Los Angeles, California, 27 December 1938)


Calvin Blackman Bridges was the only child of Leonard Victor Bridges and Charlotte Amelia Blackman. His mother died when Calvin was two years old and his father a year later, so the boy was brought up by his paternal grandmother. When he was fourteen, he was sent to Plattsburg to attend high school. Because of his deficient primary school training and because he worked to help support himself, he did not graduate from high school until he was twenty. His record was good enough, however, for him to be offered scholarships at both Cornell and Columbia. He chose the latter and entered as a freshman in 1909. His record at Columbia was outstanding, and he graduated in three years in spite of largely supporting himself by outside work and, in the last half of the period, spending much of his time and energy on research with Drosophila. In 1912 he married Gertrude Ives. The couple had four children.

In his freshman year Bridges and the writer (then a sophomore) took the beginning course in zoology, which was given (for the only time during his twentyfour years at Columbia) by T. H. Morgan. This was the beginning of a very close association, among the three of us, which lasted until Bridges’ death.

Morgan’s work on the genetics of Drosophila began in earnest in the summer of 1910; and in the academic year 1910–1911 Bridges and I were given desks in his laboratory, a room 16 by 23 feet, which came to be known as “the fly room.” Here the three of us reared Drosophila for the next seventeen years. A steady succession of American and foreign doctoral and postdoctoral students also had desks there. From 1915 Bridges was a research associate of the Carnegie Institution of Washington, and in 1928 he moved from Columbia to the California Institute of Technology, where he spent the rest of his life.

At the beginning of this period the techniques were unsatisfactory, and Bridges was largely responsible for their improvement. He introduced the use of binocular microscopes instead of hand lenses, he developed dependable temperature controls, and he played the largest part in the improvement and standardization of the culture bottles and media.

The working material for the group was the series of mutant types, and their detection and isolation was one of the major concerns of all of us—but Bridges was so good at this that he contributed many more mutants than did the rest of us. He also had the skill and patience required to organize this material into a coherent body of detailed information and to produce a series of carefully planned and useful stocks of combinations of mutant types. This information and many of these stocks are still basic and are in constant use by students of Drosophila.

In the early work there were often found a few exceptions to the usual rules for the inheritance of sex-linked genes, and Bridges undertook a study of them. He published an account in 1913, giving the phenomenon the name “nondisjunction.” No satisfactory scheme emerged, until he made a microscopical study of the chromosomes (1914). Here, and especially in his doctoral thesis (1916), he produced a brilliant and characteristically detailed and convincing account that constituted a proof of the correctness of the chromosome theory of heredity.

Bridges followed this with a study of nondisjunction of the small fourth chromosome, and this led to his development of the idea of genic balance, which has played a large part in all later interpretations of the way in which genes influence development. The classic work in this field is Bridges’ study of the determination of sex in Drosophila, which he based on his combined genetical and cytological study of the offspring of triploid females—again a brilliantly conceived and convincingly thorough piece of work.

Bridges had made himself the outstanding authority on the cytology of Drosophila, but the chromosomes were very small and so lacking in structural detail that they could be used effectively in the analysis of only a few of the many chromosome rearrangements that were discovered by genetic means—most of them by Bridges.

In 1933 the work of Heitz and Bauer, and of Painter, showed that the chromosomes of the salivary glands of Drosophila and of some other flies had a wealth of structural detail far greater than that known in the chromosomes of any other organism. Bridges threw himself into the study of these chromosomes, and produced a series of drawings of them that are still the standards of reference. This, like much of his work, required great patience, accurate observation, technical skill and ingenuity, and an understanding of what was important. In 1936 he was elected to the National Academy of Sciences.

Bridges was a friendly and generous person. Politically he was rather far to the left—a circumstance related to his visit to Russia in 1931–1932. In his personal and social relations he was a nonconformist, largely as a matter of principle.


I. Original Works. Bridges wrote about 125 scientific papers, not counting numerous notes in Drosophila Information Service, which he and M. Demerec compiled and edited from 1934 to 1939. The list that follows is a selection of the more important contributions. A fuller listing may be found in Morgan’s biography (1941; see below).

Bridges’ works include “Dilution Effects and Bicolorism in Certain Eye Colors of Drosophila,” in Journal of Experimental Zoology, 15 (1913), 429–466, written with T. H. Morgan; “Non-disjunction of the Sex Chromosomes of Drosophila,” in Science, 37 (1913), 112–113; “Direct Proof Through Non-disjunction That the Sex-linked Genes of Drosophila Are Borne by the X-Chromosomes,” in Science, 40 (1914), 107–109; “A Linkage Variation in Drosophila,” in Journal of Experimental Zoology, 19 (1915), 1–21; The Mechanism of Mendelian Heredity (New York, 1915), written with T. H. Morgan, A. H. Sturtevant, and H. J. Muller; “Non-disjunction as Proof of the Chromosome Theory of Heredity,” in Genetics, 1 (1916), 1–52, 107–163; Sex-linked Inheritance in Drosophila, Carnegie Institution of Washington publication 237 (Washington, 1916); “Deficiency,” in Genetics, 2 (1917), 445–465; “The Constitution of the Germinal Material in Relation to Heredity,” in Carnegie Institution of Washington Year Book, XV-XXXVIII (Washington, 1917–1939)—written with T. H. Morgan and A. H. Sturtevant through 1929 and with T. H. Morgan and J. Schultz from 1930, these annual reports give a picture of the work in progress and are often the only published accounts of ideas and experiments.

Also see “The Second-chromosome Group of Mutant Characters” and “The Origin of Gynandromorphs,” Carnegie Institution of Washington publication 278 (Washington, 1919), pp. 1–304; “Specific Modifiers of Eosin Eye Color in Drosophila melanogaster,” in Journal of Experimental Zoology, 28 (1919), 337–384; “Proof of Non-disjunction of the Fourth Chromosome of Drosophila melanogaster,” in Science, 53 (1921), 308; “Triploid Intersexes in Drosophila melanogaster,” in Science, 54 (1921), 252–254; The Third-chromosomeGroup of Mutant Characters of Drosophila melanogaster. Carnegie Institution of Washington publication 327 (Washington, 1923), written with T. H. Morgan; “The Translocation of a Section of Chromosome II on Chromosome III,” in Anatomical Record, 24 (1923), 426–427; “Crossing Over in the X-Chromosomes of Triploid Females of Drosophila melanogaster,” in Genetics, 10 (1925), 418–441, written with E. G. Anderson; “The Genetics of Drosophila,” in Bibliographia genetica, 2 (1925), 1–262, written with T. H. Morgan and A. H. Sturtevant; “Sex in Relation to Chromosomes and Genes,” in American Naturalist, 59 (1925), 127–137; “Some Physicochemical Aspects of Life, Mutation, and Evolution,” in Colloid Chemistry, 2 (1928), 9–58, written with J. Alexander; “The Genetic Conception of Life,” an address given before the Academy of Science, Leningrad (1931); “Specific Suppressors in Drosophila,” in Proceedings of the 6th International Congress on Genetics, II (1932), 12–14; “The Mutants and Linkage Data of Chromosome Four of Drosophila melanogaster,” in Biologicheskii zhurnal (Moscow), 4 (1935), 401–420; “Salivary Chromosome Maps—With a Key to the Banding of the Chromosomes of Drosophila melanogaster,” in Journal of Heredity, 26 (1935), 60–64; “The Bar ‘Gene’ a Duplication,” in Science, 83 (1936), 210–211; “A Revised Map of the Salivary Gland X-Chromosome of Drosophila melanogaster,” in Journal of Heredity, 29 (1938), 11–13; “A New Map of the Second Chromosome. A Revised Map of the Right Limb of the Second Chromosome of Drosophila melanogaster,” ibid., 30 (1939), 475–476, written with P. N. Bridges; The Mutants of Drosophila melanogaster, Carnegie Institution of Washington publication 552 (Washington, 1944), completed and edited by K. S. Brehme.

II. Secondary Literature. T. H. Morgan wrote four biographical accounts of Bridges: in Science, 89 (1939), 118–119; in Journal of Heredity, 30 (1939), 355–358; in Genetics, 25 (1940), i-v; and in Biographical Memoirs. National Academy of Sciences, 22 (1941), 31–48. The last three have two different photographs of Bridges, and the last has a full bibliography.

Additional biographical works are H. J. Muller, in Nature, 143 (1939), 191–192; J. Schultz, an unsigned article in National Cyclopedia of American Biography, 30 (1943), 374; A. H. Sturtevant, in Biological Bulletin, 79 (1940), 24. There are also numerous references in A. H. Sturtevant, A History of Genetics (New York, 1965).

A. H. Sturtevant

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Calvin Blackman Bridges