The spatial aspects of development, to which very much less attention is given, include regionalization or pattern formation, and morphogenesis. In practice, many French Flag patterns in biology are not simply terminal. Thus of the three examples mentioned in the introduction, obviously the early echiniderm embryo and the slime mould grex are transitory stages in more extended developmental sequences. While some insight into morphogenesis can probably be found along the lines just indicated, pattern formation is the least understood aspect of development. The capacity for the regulation of an axial pattern as illustrated by these examples can be observed in many other systems. The behaviour of such systems should be contrasted with the so-called ‘mosaic’ or non-regulative pattern formation in which removal of a part leads to a defect in the system, which is strictly related to the part removed.