Calvin Blackman Bridges Unconventional Geneticist (1889-1938)

Cold Spring

Calvin changing a tire at Cold Spring Harbor.
During most summers, Calvin took the bus from California to New Jersey and then to Cold Spring Harbor. In 1935 he hoped to make the journey by driving his automotive invention, the “Lightning Bug,” but the car was not ready due to late arrival of parts from Japan.
Courtesy of Cold Spring Harbor Laboratory Archives

Calvin made his first visit to Cold Spring Harbor in 1914 while still a graduate student in Morgan’s lab and later recalls the visit as “full of very pleasant memories.” Frank Lutz, an early Cold Spring Harbor drosophilist, had already left for the American Museum of Natural History in 1909, but there was interchange between Carnegie Institution of Washington investigators at Cold Spring Harbor and Morgan’s fly lab. Charles Metz earned his Ph.D. in Morgan’s lab in 1916 and then went to Cold Spring Harbor, and Alexander Weinstein went back and forth between the two locations.

Bridges visited Cold Spring Harbor periodically over the years, but in 1934 he made his first sustained summer visit of about 8 weeks to work on his cytological maps of the Drosophila salivary gland chromosomes at the invitation of the Carnegie Institution’s Department of Genetics led by Albert Blakeslee (1874–1954) and then Milislav Demerec (1895–1966). Morgan was not entirely enthusiastic about Bridges continuing his mapping work at Cold Spring Harbor. In a 1934 letter to Charles Davenport at Cold Spring Harbor, Bridges says “I hope you were not too disconcerted by the reply you received from Dr. Morgan! As I wrote Dr. Demerec, the difficulties of my leaving here were rather great… I have arranged with Dr. Morgan for the execution of the jobs which were making him anxious for my pressure here, and hence can accept your kind offer with official sanction.” Calvin did not ask for much at Cold Spring Harbor, just “desk room with Dr. Demerec, for my equipment will be mostly records (on 3×5 cards) and a few lenses for the study of salivary chromosomes” so that he could make “a concentrated attack on my particular problem.” This was, of course, mapping the Drosophila salivary gland chromosomes.

At this point, Cold Spring Harbor was one of the three major centers of Drosophila research. Demerec had worked hard to establish a Drosophila stock center at Cold Spring Harbor, and in 1933 he enlisted Bridges join him to begin publication of the informal Drosophila Information Service. Demerec and Bridges described the DIS as “not a publication,” but instead a way to provide “the free exchange of material and information”

to the growing population of Drosophila geneticists. The first issue appeared in March 1934. (The DIS still provides practical information about techniques and mutants to drosophilists worldwide.)

Bridges was given a workspace in the Animal House (now McClintock Laboratory) for his research and was housed in the tents on the back lawn of Blackford Hall. Needless to say, Morgan was not happy about these perceived encroachments on his territory and thought Demerec was after his Rockefeller Foundation grant money. Demerec was indeed after Rockefeller Foundation money, looking for $9000 to establish and maintain a Drosophila stock center. With Morgan on the West Coast, it was important to have a stock center in the East too for the efficient distribution of fly stocks. With great progress being made, the Drosophila genetics field had become extremely competitive and the “Arcadian” days of the Fly Room were long gone. Bentley Glass has noted that the “stolid, conservative” Demerec and the “brilliant loose cannon” Bridges made a very unlikely pair, but

despite these differences they formed “an enduring friendship.” Even so, Demerec had concerns about Bridges’ personal life that he expressed in a 1934 letter — “As you know, the Cold Spring Harbor biological community is a small closed group… it is essential in case you can come to make a gentleman’s agreement that any mixups will be avoided with the female members of this community.”

Bridges returned to Pasadena at the end of September, 1934, and his work on the fly chromosomes prompted Blakeslee to ask the Carnegie for money to connect “the visual maps of genes in the salivary gland chromosomes with the intensive study of the gene Demerec has been carrying on,” as well as to study the evolution of chromosomes.

Bridges was invited back to Cold Spring Harbor in 1935 and he accepted, saying, “I feel that last summer’s work was very profitable.” He arrived in July, and this summer Bridges’ son Philip, a student at Wesleyan, was appointed as his assistant. Calvin stayed for 11 weeks that summer.

He paid $2 per week for tent rental and $7 per week for his meals at Blackford Hall; he was provided with $300 for travel and living expenses. For his 1936 stay, he was offered $100 per month “in lieu of travel and living expenses for a minimum 6-week stay” that was not to exceed $300.

For the next two years he maintained the same summer work schedule at Cold Spring Harbor with Philip. Bentley Glass related Bridges’ working method — “…periodically on the hour, Bridges would straighten up from his cramped hunch over the microscope, shrug the kinks out of his shoulders, raise his arms high and wide, exclaim ‘God, what a life!’ and then bend back to his task.”

Calvin came again in the summer of 1938, but he had a heart attack at Cold Spring Harbor that summer and was hospitalized. When Bridges returned to Pasadena he had a second episode early in December and died on December 27th. In a January 23, 1939, letter to Morgan, Demerec said “We were ready to hear the worst but still when the news came it was difficult to realize that he, who was among us only a few weeks ago, is gone forever. Bridges left Cold Spring Harbor cheerful and apparently vigorous and no one here had the slightest premonition of what was to happen so soon.” Edward Novitski, who only knew Bridges briefly, related that “I did not know then what I do now, that his illness was terminal and he knew it.” Morgan in a letter to Tove Mohr said that the postmortem had shown that Bridges’ heart valves “had become infected and were gradually breaking up.”

Bridges left behind a huge amount of unfinished work – the cytological mapping of the salivary chromosome bands, revision of the genetic maps of the chromosomes, and completion of the genetic symbols for fly mutants. In a letter to Morgan, Demerec noted that Bridges had said to him “after completing these problems he believed his contribution to science would be great enough to justify his working at a somewhat slower pace.” Demerec made the case that this work should be completed at Cold Spring Harbor and Morgan protested. But Morgan’s interest in the fly was waning at this point, his lessening interest certainly intensified by Bridges’ death — he told Demerec that “Bridges’ death has been a very severe blow to us.” In a 1967 Science reminiscence, Jack Schultz says that Morgan told him “he thought perhaps Bridges had made the solidest contribution of them all.”

After a series of misunderstandings about Demerec’s intentions, Morgan eventually conceded much of this work to Demerec. Demerec assured Morgan that “There is no doubt that when the book is published it will have heavy use as a reference book.” The salivary gland maps would be completed by Philip Bridges and the genetics symbols project would be coordinated by Kitty Brehme at Cold Spring Harbor. Again Morgan protested, this time that “I do not regard Miss Brehme as a person experienced enough to handle this material.” However, Demerec pushed on with the appointment of Kitty. When the job was offered to her by Demerec, Kitty replied “There is nothing I would rather do than the project you outlined of preparing the Drosophila mutant material of Bridges for publication.” Kitty Brehme collated all of the information Calvin had collected on 3×5 index cards. The result was

The Mutants of Drosophilia melanogaster, which was published in 1944. As Demerec predicted, it was THE Drosophila reference for several decades. The book later morphed into the D. L. Lindlsey and E. H. Grell “Genetic variations of Drosophila melanogaster” and eventually the online resource FlyBase.

E.B. Lewis noted that Bridges’ repeat hypothesis led to the discovery of the bithorax and antennapedia complexes and eventually to the HOX homebox genes, which are conserved in all higher animals. Lewis, who was a co-recipent of the 1995 Nobel Prize for these discoveries, noted that the conservation of HOX “points to evolution of the HOX-C by a repeated gene duplication and diversification… I believe Bridges would have liked that.”

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