The organism in development

Developmental biology has resurfaced in recent years, often without a clear ly central role for the organism. The organism is pulled in divergent direc tions: on the one hand, there is an important body of work that emphasizes the role of the gene in development, as executing and controlling embryolog ical change; on the other hand, there are more theoretical approaches under which the organism disappears as little more than an instance for testing biological generalizations. I press here for the ineliminability of the org anism in developmental biology on explanatory grounds. I examine classical work concerned with growth and development, particularly in Drosophila and C. elegans. Some of this work is suggestive of modular development, and acc ordingly suggests a level below that of the organism as being explanatory. These are not the only type of case. There are other equally well-establish ed results, which indicate greater integration in the developing organism. Though with a modular organization the organism can be thought of as made u p of its constituent traits, and though the explanations of these traits ma y lie in terms of cells or genes, even with modular development the explana tions of "genetic" differences require an appeal to the organism. With non- modular organization the organism has an even more central role. This does not mean that these genetic or cellular contributions are unreal in any way , or that development requires some sort of vitalistic contribution; but th e genetic contributions make sense only as constituents of the organism, em bedded in a larger organic context.