ORIGINS OF EMBRYONIC PATTERNS 703 



without any pre-existing regional differentiation, and it represents the 

 most primitive pattern of organismic behavior in reaction to an external 

 factor. If a region of primary activation persists, the gradient may per- 

 sist and become a physiological axis, that is, a pattern in which axiate 

 development is possible. Many lines of evidence indicate that axiate or- 

 ganismic pattern in its simplest terms is such a gradient, but it does not 

 follow that individual development always begins with pattern in its 

 simplest terms. Many eggs at the beginning of embryonic development 

 are far beyond this stage. 



The gradient pattern represents the "organism as a whole" in its sim- 

 plest terms. It is the primary and fundamental correlating and integrating 

 factor on an organismic scale. That the organism is more than the sum 

 of its parts is undoubtedly true, for it consists not only of the parts but 

 of the ordering and integrating factors of the gradient system. The unity 

 or wholeness, factor of wholeness, morphe, etc., of the organism, is pri- 

 marily the gradient system and the relation of dominance and subordina- 

 tion resulting from it; this makes possible the spatial and chronological 

 order of development.''^ 



Again it must be emphasized that embryonic development constitutes 

 only a small part of the problem of developmental physiology and, so far 

 as beginnings of developmental pattern are concerned, not the most im- 

 portant part. An adequate theory of developmental pattern must include 

 all types of development and must be based on the simpler, not on the 

 most highly specialized, types. There must be a fundamental identity of 

 developmental pattern underlying development of an individual from an 

 isolated piece of another individual, from a bud, from an aggregate of dis- 

 sociated cells, and from an egg. The concept of developmental pattern 

 as primarily a dynamic gradient system or pattern is an attempt, based 

 on much evidence, to formulate that identity in general physiological 

 terms. Can we conceive all the reconstitutions of wholes from parts — 

 either parts of an egg or embryo or parts of a mature individual — except 

 in terms of an essentially quantitative gradient system, unless we are 

 willing to follow Driesch in postulating a metaphysical ordering and inte- 

 grating principle, a sort of god in the machine, which we may name 

 "entelechy" or something else, as we please? Driesch argued that an or- 

 ganism is not a "machine," that is, a physicochemical system, because 

 isolated parts of a machine cannot make a whole machine, but isolated 

 parts of many organisms can become wholes. But Driesch was thinking 



■''* Cf. Ritter, 1919; von Bertalanffy, 1932. 



