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Riddle DL, Blumenthal T, Meyer BJ, et al., editors. C. elegans II. 2nd edition. Cold Spring Harbor (NY): Cold Spring Harbor Laboratory Press; 1997.

Cover of C. elegans II

C. elegans II. 2nd edition.

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Section VConclusions

Incorporation of C. elegans into a phylogenetic picture of the Metazoa reveals deep homologies in a set of building blocks for developmental modules that can be assembled in a variety of ways to construct “endless forms most beautiful and most wonderful.” Convergences are thus possible, and perhaps even likely if a mechanism is highly constrained. Conversely, diverged or analogous developmental mechanisms may underlie homologous features. Taking account of these issues in the context of questions such as “How have living things become what they are, and what are the laws which govern their forms?” (see p. 1 in Bateson 1894) requires both an understanding of how structure is determined by developmental genetic mechanisms and an understanding of the ways that these structures and elementary mechanisms can and have changed.

Incorporation of a model system into a phylogenetic framework informs both pursuits. We no longer need to be reproached because “those who are in contact with the facts and material necessary for this study care little for the problem, or at least rarely make it the first of their aims, and on the other hand those who care most for the problem have hoped to solve it in another way” (see p. 574 in Bateson 1894). Reconstructing the requisite phylogenetic framework for lineages nearly as deep as Metazoa itself is a daunting task. Yet, in combination with other kinds of phylogenetically informative characters and the biological variation within this enormously diverse phylum, molecular sequences promise to add a fundamentally important information base for approaching such problems.

Although the analysis of worm character evolution in the context of such a phylogeny is not likely to divulge the precise developmental genetic changes that transformed our hominoid ancestors into humans only a few millions of years ago, it will provide models for how evolution works with development to make living forms. From models arise predictions. Only then can we evaluate and incorporate notions about general mechanisms into the body of explanatory principles being built by integrative approaches in biology. Perhaps in this context, Ralph Waldo Emerson's words provide a special perception:

And, striving to be man, the worm
Mounts through all the spires of form.
May-Day (1867)

Copyright © 1997, Cold Spring Harbor Laboratory Press.
Bookshelf ID: NBK20000
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