Thomas Hunt Morgan at the marine biological laboratory: naturalist and experimentalist.

IN the early 1910s, researchers at the Marine Biological Laboratory (MBL) in Woods Hole, Massachusetts, might have wondered why a colleague, Thomas Hunt Morgan (Figure 1), began shipping fruit flies from his Columbia University lab to the MBL each summer. After all, the Woods Hole currents supplied the MBL with a rich variety of marine organisms and Morgan, an avid practitioner of experimental embryology, made good use of them. Yet those who knew Morgan well would not have been surprised by his insect stocks. A keen naturalist, Morgan studied a veritable menagerie of experimental animals—many of them collected in Woods Hole—as a student and later researcher at the MBL from 1890 to 1942. Moreover, Morgan always had a diversity of investigations going on simultaneously. ‘‘This was the way Morgan worked: he wasn’t happy unless he had a lot of different irons in the fire at the same time,’’ wrote A. H. Sturtevant, Morgan’s long-term collaborator (Sturtevant 2001, pp. 4–5). In Morgan’s first 3 decades at the MBL, for instance, he studied at least 15 different species, including the now-famous fruit fly, while investigating a variety of problems related to his central interests in development and heredity (Morgan 1888– 1937; Marine Biological Laboratory 1909). Morgan was also a vocal proponent of experimentalism, and at the MBL he (quite successfully) joined with Jacques Loeb in arguing for a quantitative, predictive foundation for biological studies (Allen 1969). Morgan was interested only in scientific problems that could be experimentally tested. Deeply wary of ungrounded hypotheses, he sought not overarching theories, but experimental methods that would allow him to identify proximate causes. This stance would triumph in Morgan’s work with the fruit fly, Drosophila melanogaster. Morgan initially began breeding this animal in his search for an experimental approach to evolution: he was testing an alternative to the theory of natural selection, which he felt was insufficient to explain the origin of new species. But when a sex-linked mutation appeared in his Columbia University stocks in 1910, Morgan’s attention was diverted to analyzing the material basis of sex determination and inheritance. By 1912, he and his colleagues were mapping the location of genes on chromosomes. These epoch-making studies launched the field of experimental genetics. Morgan’s penchant for maintaining multiple, diverse lines of investigation paid off in important ways, as this review of his work at the MBL up through the mid-1920s shows. First, Morgan was able to synthesize his research on many different organisms in his book Regeneration (Morgan 1901), which today provides a useful and insightful perspective on regenerative medicine. Second, evidence from originally distinct studies conceptually converged for Morgan. An example is his post1910 work at the MBL on the insects phylloxeran and aphid, which confirmed his early Drosophila results on the relationship of the chromosomes to sex determination and inheritance. Morgan’s dual characteristics as a ‘‘naturalist and experimentalist’’ (Figure 2) place him historically in an era when biology was transitioning from a descriptive and often speculative field to an experimental one (Allen 1969). Yet they may indicate also why Morgan was a successful scientist, one who received the first Nobel Prize ever awarded in genetics in 1933 and became the first in a now-long list of Nobel Laureates affiliated with the MBL. Morgan’s appreciation of natural diversity and his wide-ranging investigations, coupled with his skepticism toward a priori theories, could have left him flailing in a biological wilderness. What anchored him was his strict experimentalism, his insistence on choosing problems that could be analytically tested. Corresponding author: Office of the Director, Marine Biological Laboratory, 7 MBL St., Woods Hole, MA 02543. E-mail: [email protected]