William Hunter and the eighteenth-century medical world

divergence of the two disciplines and Sander with their reconciliation in developmental genetics. Allen summarizes much of the work on this subject and speculates that American breeding interests were responsible for providing impetus for the separation. He states that "the dichotomy between embryology and genetics was inevitable" and that Morgan was the "unplanned agent" of this separation. Sander's analysis of both past and present attempts at reconciliation start at the opposite conclusion: "This strict separation of disciplines-one studying transmission, the other the expression of hereditable traits-may have contributed to scientific progress for a time, but it is by no means a requirement imposed by Nature herself .... Aloof from these hagglings stood Edmund B. Wilson and his Cell. Its first two editions (1890, 1900) antedated the schism and, if heeded by the opponent parties, might have suppressed it from the beginnings." Sander also describes contemporary research that bears upon one of the most important conceptual undertakings ofmodern developmental biology: relating differential gene activity to the generation ofpattern. Another contemporary developmental geneticist, Eric Davidson, shows briefly how modern research is indebted to the principles established by Theodor Boveri, and Edward Yoxen looks at the relationship of genetics and embryology as seen in the career ofC. H. Waddington. Robert Olby, looking at a similar period, identifies three research programmes (colloid chemistry, histochemistry, and X-ray crystallography) to study structures existing between the ultramicroscopic and molecular size ranges of the cytoplasm. Witkowski, Wallace, and Wolpert detail the history of the "form-problem" from R. G. Harrison onward. That all three authors are from British institutions is not surprising, given the eminence of England in this field. Why this should be so would make an interesting study, but it is not addressed herein. Witkowski reviews Harrison's intellectual career, stressing the interaction between problem and technique. The contributions on pattern formation (Wolpert) and regeneraton (Wallace) are too short to do justice to their subjects. Wolpert gives an excellent summary of the turn-of-the century work on gradients, but he stops short of discussing many of the conceptual advances made in his own laboratory. Wolpert's contributions are detailed in the last chapter by the philosopher N. W. Tennant, whose essay on reductionism, holism, and determinism is written in a well-organized, non-technical style, which can even be read by scientists for whom nothing is real unless an antibody can be made against it. Tennant also respects the heterogeneity of developing …