8 - Pulling together some threads

Summary

The purpose of this chapter is to take an overview of the morphogenetic enterprise and to consider some aspects of the subject that are common to the many developing systems that we have examined. To a great extent, the topics considered here derive from the dynamic framework just put forward, but, before doing this, we will consider how one should approach the problem of analysing morphogenesis and what we should expect of morphogenetic theory and its theoreticians. In doing this, I shall assert that the process of tissue formation is in many ways the cellular equivalent of molecular self-assembly and that the appropriate language in which to analyse morphogenesis is that of the differential equation, even though it is usually impractical even to formulate let alone solve the actual equations that describe these processes. We will therefore spend some time using this formalism to examine the various dynamic aspects of morphogenesis and will then consider the relationship between morphogenesis and growth. The chapter ends with a brief discussion of a question the answer to which will guide a great deal of future work: what is the relationship between the information stored in the genome and the morphogenetic phenotype? It is worth trying to answer this question correctly because we need to know which experimental approaches will be helpful in increasing our understanding and which will give empty information.