Positional information limits the selfexplaining endeavour in morphogenetic theory (in the sense of Turing). Towards the understanding of the functioning of biological forms.

The notion of `positional information' with respect to morphogenetic theories is critically examined. We analyzed the significance of positional information in the original paper by TURING (1952) on morphogenesis through reaction-diffusion mechanisms. It is concluded that positional information is necessary to understand the emergence of biological forms, and hence limits the self-explaining endeavour of these forms. Moreover, it is suggested that positional information is necessary to understand some of the essential functions of biological forms, namely the functions of insulation and transport.