Section IVConcluding Remarks

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The studies described here have shown that male-specific structures arise from rather complex lineages in which cells of many different types and characteristics are specified. Studies of cell fate specification in these lineages are proving to be a rich source of insight into general problems of development. One striking finding is that many genes (or pathways) affect cell fate specification in different cells. For example, lin-17 is necessary for a variety of asymmetric cell divisions, whereas lin-12 specifies alternative cell fates for many pairs of cells. Since the cell types produced are often quite different, comparison of different aspects of development might allow an understanding of how general mechanisms of cell fate specification interact with tissue-specific differentiation programs. How these cell types, once specified, differentiate into functional organs and structures should help us understand the principles of morphogenesis. The male nervous system affords a chance to relate nervous system structure to behavior. It will be invaluable to have a reconstruction of the male nervous system, but light microscopic methods might substitute in part. Comparisons of male and hermaphrodite development and behavior provide opportunities to analyze the sex specificity of gene action. Although a comprehensive understanding of the C. elegans genome will require insight into the role each gene has in both sexes, the beauty of their anatomy and subtlety of their behavior, coupled with their dispensability, make C. elegans males a worthy subject of study in their own right.