Background
Clarence Erwin McClung was born on April 5, 1870 in Clayton, California. He was the son of Charles Livingston McClung, a mining engineer of Scots-Irish descent, and Annie Howard (Mackey) McClung, the daughter of a physician.
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Clarence Erwin McClung was born on April 5, 1870 in Clayton, California. He was the son of Charles Livingston McClung, a mining engineer of Scots-Irish descent, and Annie Howard (Mackey) McClung, the daughter of a physician.
Because his father's occupation required that the family travel considerably, Clarence's early education was acquired in several different places. After attending high school in Columbus, Kans. , he worked for two years in his uncle's drug store and studied pharmacy at the University of Kansas in Lawrence, from which he received the Ph. G. degree in 1892. He then spent several years working as a chemist in a sugar refinery in New Orleans each autumn and attending the University of Kansas each spring, to earn a liberal arts degree, which he finally received in 1896. An exceptionally gifted student, he was immediately appointed to the staff of the University of Kansas, as a substitute instructor in histology in 1896 and in botany in 1897. During those years he also spent one term studying with the cytologist E. B. Wilson at Columbia University and was awarded the M. A. degree from that institution in 1898. By that time the University of Kansas had appointed him assistant professor of zoology.
McClung was promoted to associate professor in 1900, to chairman of the Department of Zoology in 1901, to curator of paleontology in 1902, and to professor of zoology in 1906. While engaged in these teaching and administrative duties, he was also pursuing cytological research; that research won him a Ph. D. from the University of Chicago in 1903 but more important, it also won him a permanent place of honor in the history of genetics. The research in question was a study of spermatogenesis (cellular division leading to the production of sperm) in the grasshopper Xiphidium fasciatum. McClung had spent the summer of 1898 at the University of Chicago, in the laboratory of W. M. Wheeler. In 1912 McClung moved to the University of Pennsylvania, where he remained as professor of zoology and director of the Zoological Laboratories until his retirement in 1940. During this time he continued his research into the cytological aspects of chromosome behavior. For twenty years (1920 - 1940) he was also the managing editor of the Journal of Morphology. At the universities of Kansas and Pennsylvania he trained dozens of advanced students, many of whom went on to successful careers as biologists and teachers. McClung died on January 17, 1946 in Swarthmore, Pennsylvania.
As his career progressed, McClung became one of the most influential biologists in the United States. He was the first director of the Division of Biology and Agriculture of the National Research Council (1919 - 1921); in this position he helped to establish the pattern of governmental funding for biological research. As head of this division he also laid the original plans for an international biological abstracting service, which, as Biological Abstracts, has become a crucial reference tool. McClung was also very active in the development of the Biological Experiment Station at Woods Hole, Massachussets, one of the leading biological research facilities in the United States; he served Woods Hole (where he and his family spent many summers) in a wide variety of executive capacities.
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Wheeler, who had just completed a study of oogenesis (cellular division leading to the production of eggs) in the female of that species, urged his student to explore the parallel process in the males. McClung noticed that in the second division of spermatogenesis there was one chromosome that did not replicate itself, with the result that half the spermatids did not possess that chromosome; he named this the accessory chromosome, to indicate that it seemed an addition to the normal number for the species. Several other cytologists had already noticed the additional body, but no one before McClung had realized that it was in fact a chromosome. McClung's accomplishment stemmed, in part, from the excellence of his histologic preparations. As an observational feat this discovery was remarkable, but what made it particularly crucial for the history of genetics was McClung's guess purely hypothetical at the time that the accessory chromosome was, in fact, a determinant of the sex of the grasshopper. McClung's guess was based upon the fact that half the grown individuals of the species would possess the additional chromosome, and that the only characteristic that roughly divides the population in half is sex. McClung's guess was proven true three years after the publication of his paper, when in 1905 E. B. Wilson and Nettie Stevens published their extensive cytological researches into the chromosomal determination of sex. These discoveries came just a few years after the rediscovery in 1900 of Mendel's work on patterns of inheritance in sweet peas and were almost contemporaneous with the enunciation, in 1902, of the Sutton-Boveri hypothesis. This hypothesis suggested that the patterns of chromosomal division could be precisely related to the Mendelian patterns of trait distribution and that, consequently, the chromosomes must be the bearers of heredity.
a member of Episcopalian Church of the Messiah
McClung was an extremely skillful microscopist; some of the techniques that he developed for the histologic preparation of specimens and some of the devices that he suggested for the improvement of microscopes were major contributions to biology. As part of his work in microscopy he edited an influential handbook of microscopic technique, which went through several editions before and after his death.
McClung married Anna Adelia Drake, an accomplished pianist, on August 31, 1899; they had two daughters, Ruth Cromwell and Della Elizabeth.
April 5, 1877 – November 10, 1916 W. S. Sutton was an American geneticist and physician. He was a student of McClung's and of Wilson's; his hypothesis, which was stated almost simultaneously by the European biologist Theodore Boveri, is now one of the tenets of modern genetics.
