CELL INTERACTIONS: THE ROOTS OF A CENTURY OF RESEARCH

¹ Carnegie Institution of Washington, 1530 P Street, N. W., Washington, DC 20005

Only rarely have marine organisms provided experimental systems par excellence for concerted and continuing analyses of mechanisms of cell interactions, in either of the two main categories I consider: inductive and morphogenetic. Although there were significant findings with marine organisms from the beginning, they were frequently overshadowed, possibly because the seasonal character of research on marine organisms resulted in a focus on experiments that did not require continuity, and on comparative, rather than on mechanistic, analyses.

The roots of the study of inductive interactions—contemporary with the establishment of the Marine Biological Laboratory (MBL)—are found in the work of Chabry and Roux on the development of isolated blastomeres of an ascidian and a frog, respectively, after destruction of neighboring blastomeres. Roux's findings had a larger impact than Chabry's, in part because Roux cast his findings in larger terms than did Chabry, but also because of the differences in experimental approaches that emerged. The fact that the blastomeres of many marine embryos could be dissociated readily, lead to repeated comparative studies of the capacity for development of isolated blastomeres. The use of amphibian systems produced a drive to understand the failure of independent development; and the use of transplantation techniques resulted in the discovery of the "organizer," that set in train fifteen years of intensive and largely fruitless research on its chemical nature, punctuated by Lester Barth's demonstration of "neural differentiation without organizer."

The impact of studies of marine forms on the emergence of today's ideas on morphogenetic interactions—cell adhesion molecules, etc.—is less clear. The contributions of Herbst in dissociating embryos in calcium-free sea water, and of H. V. Wilson, and later Galtsoff, in re-aggregating sponge cells had no significant effect until after Holtfreter's far reaching studies of "tissue affinity."