ABSTRACT

Most instances of regionalisation are accompanied by morphogenesis, as for instance when the neural tube becomes regionalised into the fore-, mid- and hind-brains, which swell into their characteristic vesicular shapes; and there are many instances in the appearance of bristles in definite patterns on parts of an insect’s body. Some molecular biologists, flushed with their success in discovering the outlines of the process of the control of gene activities in bacteria, have suggested that the problem of development and differentiation in higher organisms would soon yield to attacks along similar lines. At the molecular level there seems to be only two clearly definable notions allied to the general concept of growth, namely the replication of the genetic material and the production of certain specified molecules or categories of molecules. This logical structure of the theory of histogenesis was developed before the discovery of the D N A-R N A-protein story.