Introduction to the Symposium: Principles and Problems of Pattern Formation in Animals

Abstract

This symposium, Principles and Problems of Pattern Formation in Animals brought the major ideas and recent advances in the growing field of pattern formation to the general scientific community for the first time. Recognition of the basic problems of pattern formation can be traced back to the very beginnings of the science of ex? perimental embryology. Hans Driesch (1908), from his experiments on the exten? sive regulative ability of sea urchin em? bryos, was led to the basic idea that cells behave as if they have information about their position within the whole. Today, we would say that the cells have positional in? formation. Unfortunately for the devel? opment of the field, Driesch became convinced that there was no physical basis for positional information, and instead, he in? voked a life force or entelechy to account for the organizational ability of embryos. After this, the level of interest in the field of pattern formation was extremely low and it was not until seventy or so years lat? er that it was rekindled by Lewis Wolpert (1969, 1971). His success in catalyzing the current wave of interest lay in the way in which he graphically laid out the basic problems, and in the way he showed that simple coordinate systems with boundary regions could provide the physical basis for positional information. Several principles emerged from Wolpert's 1969 paper which helped to open up the field for experimentation and theory. In the first place, he stressed a separation between the assignment of a positional val? ue to a cell within a coordinate system, and the interpretation which that cell might lat? er make of this positional value. The sig-