[Introduction] [letter one] [letter two] [posters] [Achievements]

Written by Dr. Shinya Inoué
Distinguished Scientist
Marine Biological Laboratory

June 1989


Among those who have devoted their lives to the study of fundamental biology of marine organisms, Professor Katsuma Dan shines uniquely above the others. Katsuma Dan made numerous landmark contributions, both through his own innovative research, and by stimulating the many colleagues and students that he trained. Indeed, the impact of the Dan school has been felt for decades throughout the biological community, not only in Japan, but widely around the world.

Katsuma Dan has made pioneering studies on marine organisms--their cell division, fertilization, early development, and eel' differentiation, in addition to lunar-influenced spawning cycles. By introducing a method for measuring the local expansion and shrinkage of the cell surface during cell division, Dan made possible the study of this ephemeral yet important cell activity on a quantitative basis. The study gave rise to his historic proposal that cell cleavage is initiated by elongation of the mitotic spindle, which physically draws in the furrow via the astral rays anchored to the furrow cortex and the spindle poles (Dan, 1943). By emphasizing direct microscopic observation of cell behavior in echinoderm embryos growing naturally, or as modified by elegantly simple experimental parameters, Dan with his trainees uncovered many fundamental aspects of cell behavior that underlie fertilization, organismic development, and morphogenesis (e.g., Dan and Okazaki, 1956). He and Dan Mazia were the first to succeed in the mass isolation of the mitotic apparatus, thus opening up the path for direct chemical analysis of the mitotic machinery (Mazda and Dan, 1952). Earlier, Katsuma and Jean Dan revealed the surprising impact of the lunar cycle on the spawning behavior of a sea filly, whose gamete spawning could be predicted to the hour on one unique day of the year (Dan and Dan, 1941). His contributions to our understanding of cell division still continue, focusing our eyes towards the mechanism of division and its developmental significance as elucidated by unequal cleavage (Dan et al., 1983). And today at the age of 85, he still commutes to the Misaki Marine Station to continue his dialogue with the sea urchins and quest for the nature of cell division.

From 1965 to 1973, as President of the Tokyo Metropolitan University, Professor Dan guided and led the faculty and students away from disruption through the turbulent years of academic upheavals. As a young scientist and father of a growing Japanese-American family, he protected and nurtured his family, in addition to his students, during the war-torn 1940s. These turbulent years, rather than intruding into his studies, in fact challenged Dan's spirit of independence, courage, and quest for truth, and saw his research and training flourish. The impact of his legendary contribution to Japanese and American science through his message at the Misaki Marine Station "the last one to go" (copy enclosed) should need no elaboration.

In brief, few throughout the history of biology have done as much as Professor Katsuma Dan to explore, and promote the exploration of, marine organisms in the quest of fundamental biology on a global scale.