Changing conceptions of organization and induction

SYNOPSIS. Oscar Hertwig (1896) noted that the central biological problem concerned preformation and epigenesis: which provides the basis for organic development? Does an organism begin preformed and just grow larger, or does form and organization emerge gradually? And how? The best scientific approach to the problem seemed to lie with Wilhelm Roux's program of materialistic experimental developmental mechanics, or "Entwickelungsmechanik." Yet that path did not lead directly to answers. Instead, embryology experienced a cycle of highs and lows throughout the first half of this century, and problems of morphogenesis have often faded into the background, regarded as old-fashioned, descriptive, and nonproductive science. A century later, morphogenesis has regained a central place within biology. A special issue of Science recently reported that "unlike human centenarians who are reaching the end of life, developmental biology is basking in its full-blown prime. Indeed the excitement and promise of the field have never been greater, as researchers close in on the secret of how a single fertilized egg cell goes through the complex and beautifully orchestrated series of changes that create an entire organism" (Baringa, 1994, p. 561). Despite their centrality to biology's experimental traditions, the pioneering work and research traditions of developmental biology have remained little explored. This project will take up that exploration, analyzing the changing ways central issues of development were addressed earlier this century. Against the background of similar questions, significantly different details in approaches, methods, techniques, and basic assumptions have pushed and pulled researchers in a variety of directions. This paper will focus on the emergence of four research traditions between 1890 and the 1930s, traditions that have waxed and waned in importance since then.