Organization 455 



factor of some sort, but it should be possible to describe this in more pre- 

 cise terms than does Gurwitsch. 



Fields of various sorts have often been postulated in animal develop- 

 ment, but in a somewhat more descriptive sense, as the developmental 

 influence of a given region over structures in it. If the rudiment of a 

 young and growing amphibian tail, for example, is transplanted at an 

 early age into the region of a leg it will grow into a leg since it is now in a 

 leg field. If it is somewhat older before transplanting it will become a 

 tail, since its own tail field is now operative. This conception of a morpho- 

 genetic field recognizes the formative influence acting within a given 

 region or throughout the embryo but offers little explanation of this 

 action. Fields have been discussed by Weiss (1950), Raven (1943), 

 and many other experimental embryologists. In botanical morphogenesis 

 the field concept has been employed by the Snows and Wardlaw to ac- 

 count for the localized development of lateral structures at the apical 

 meristem. 



More specific is the suggestion of Burr and others (1932) that the 

 morphogenetic field is a bioelectric one. Burr has found that around a de- 

 veloping structure, such as a fertilized egg in animals or a developing 

 ovary primordium in plants, a micropotentiometer will reveal an orderly 

 pattern of potential differences that is a correlate of the form which will 

 develop from them. Burr and Northrop (1935) support the view that 

 the primary entities in nature are fields and not particles and that the 

 former determine the activities of the latter instead of the other way 

 around. Both physical and biological phenomena certainly are electrical 

 in their ultimate nature, but Burr's theory goes much further than that 

 in assuming the organized biological pattern, manifest to our eyes, to 

 be the visible expression of an underlying bioelectrical pattern. The ori- 

 gin of such a pattern and what determines the changes in it are yet un- 

 known. 



One of the difficulties in accounting for an organic pattern is to see how 

 it can arise in a semifluid and formless protoplasmic system. How, one 

 asks, can such a flowing and unstable material as protoplasm produce 

 the very specific forms which come out of it? It is obvious that proto- 

 plasm, homogeneous though it seems to be, must have a structure of 

 some sort. The electron microscope is beginning to show what this 

 structure, at the macromolecular level, actually is (Weiss, 1956; Frey- 

 Wyssling, 1953). The organized pattern which we see emerging from 

 living stuff seems to be rooted in these submicroscopic configurations 

 of molecules. The developmental norm or pattern must in some way be 

 prefigured in the specific constitution of an organism's protoplasm. The 

 possibility that there may be a persisting pattern in the cytoplasm is sug- 

 gested by the work of Tartar (1956) on the ciliate protozoan Stentor, 



