A field is a region of physical influence. Fields are not a form of matter, rather, matter is energy bound within fields. In current physics, several kinds of fundamental fields are recognized: the gravitational and electro-magnetic fields and the matter fields of quantum physics.
The field concept in biology has its origin in the work of Hans Driesch, although the concept itself was elaborated by A. Gurwitsch and P. Weiss. (see account in Gerry Webster and Brian Goodwin, Form and Transformation, pp 94-100) For Joseph Needham, fields are "wholes actively organizing themselves."
In the last decade of the nineteenth century, the embryologist Wilhelm Roux proposed a "developmental mechanics" (Entwicklungsmechanik ) to account for origin and maintenance of organisms through a causal morphology that would reduce them to a "movement of parts," and would prove that biology and physics were completely one with each other. Roux sought to transform biology from a purely historical into a causal discipline through analytic thought and experiment. His "mosaic theory" described development as the self-differentiation of hereditary potentialities with the irreversible functional differentiation among cells. This hypothesis was supported in part by Roux's own experiments at the marine biological station in Naples. When he killed one of the first two cleavage cells in a frog's egg, the surviving cell, as he expected, gave rise to only half of a normal embryo.
in 1891, while working at the Naples station with a different organism, Hans Driesch obtained radically different results. Driesch demonstrated that, contrary to the Roux-Weismann hypothesis, each cell of a sea urchin embryo, when isolated at the two-cell stage, does not produce a half-embryo but a complete, miniature pluteus larva of normal form. (see mechanism / vitalism for philosophical interpretations of these experiments.)
The sea-urchin embryo, therefore, possesses powers of self-regulation such that a normal form will be produced following a variety of experimental perturbations. These experiments involve the isolation and transplantation of the material of developing organisms, that is, changing the spatial relations of the material, and lead to the aphorism "Developmental fate is a function of position." Thus it would seem that the morphogenetic field causes changes in the properties of the material. Hans Spemann pioneered the experimental idea of the "organizer," which moulds the region of its morphogenetic field. Contemporary scientists such as Lewis Wolpert describe "positional information" as a way the morphogenetic field acts as a source of spatial order. Stuart Kaufmann also discusses positional information and "fate maps."
In the early stages of embryos, up to gastrulation, and in certain species that remain capable of regeneration, like the hydra, the embryo acts as a unitary field. However, with the onset of neurulation, secondary fields appear, sometimes called individuation fields. At this point, the embryo has become a spatially organized mosaic of relatively autonomous regions, each region corresponding to a future part or organ system. These regions will produce the same morphological features even when transplanted. Each of these can be thought of as a field with its own powers of regulation.
In Rupert Sheldrake's hypothesis of formative causation, morphic fields, are extensions of the concept of physical fields. For Sheldrake, these fields are themselves influenced and stabilized by morphic resonance from all previous similar morphic units.
Brian Goodwin also uses the term morphogenetic field, but in contradistinction to Sheldrake's nonphysical fields. Goodwin is interested in the ways mechanical forces and chemical influences result in spatial organizing activities and pattern formation. (see How the Leopard Changed its Spots, pp 94-98, 148) Morphogenetic fields can result in generic (or typical) shapes.
Goodwin also refers to some of the more mysterious aspects of quantum fields, however, notably non-local causality, and in this respect comes closer to the "occult" qualities of Sheldrake.