METHODS OF PHYSIOLOGICAL ANALYSIS 8i 



arisen in connection with amphibian gastrulation and induction (see pp. 

 154, 477). Presence of axial functional differentials has been demonstrated 

 or indicated in many organisms and organs in many ways. Functional 

 dominance of apical or anterior regions is a familiar fact. In planarians 

 and hydroids any body -level dominates, to some degree, more basal or 

 more posterior levels, provided more apical or anterior regions are absent. 

 The central nervous system in general, the ctenophore plate row and its 

 conducting path, the heart, the mammalian alimentary tract, and particu- 

 larly the small intestine, all present somewhat similar relations of domi- 

 nance. 



Study of the physical condition of protoplasm may show regional dif- 

 ferences or chronological changes in viscosity, gelation, etc., which are re- 

 lated in some way to developmental pattern. Certainly the colloidal dif- 

 ferences between the cell surface and interior are fundamental factors in 

 the pattern of the cell as an organism. With the aid of polarized light and 

 X-rays much has been learned concerning the ultra-structure of many 

 morphological differentiations and products of living protoplasms, muscu- 

 lar and other fibers, both permanent and temporary, membranes, chromo- 

 somes, cellulose, hair, etc. The crystalHne or other orientations of mole- 

 cules or micellae discovered or inferred appear, in general, to be character- 

 istic of rather highly differentiated protoplasms or products or related to 

 local conditions, mechanical tensions or pressures, surfaces, or interfaces. 

 Up to the present no fundamental ultra-structure of a protoplasm that 

 might be regarded as the foundation of organismic and developmental pat- 

 tern has come to light. Many of these ultrastructural patterns are more 

 or less continuously forming and disappearing in protoplasms, and those 

 that are persistent and associated with morphological differentiation are 

 apparently derivatives rather than fundamental factors of pattern. 



METHODS OF ANALYSIS OF DEVELOPMENTAL POTENTIALITIES 

 AND POTENCIES 



As the words are used here and in following pages, "potentiality" 

 means possibility and "potency" means power or ability. Not all develop- 

 mental potentialities are realized in development under natural condi- 

 tions, for realization of all potentialities development in all possible en- 

 vironments is essential; it is impossible to determine what the potential- 

 ities are in any other way. Developmental potency, the ability to develop 

 in a certain way, represents the potentiality which is realized in a particu- 

 lar environment, intraorganismic or external. In the course of develop- 



