646 PATTERNS AND PROBLEMS OF DEVELOPMENT 



independent of particular genes and of the nuclear or chromosomal pat- 

 tern. A discussion by Morgan (1919, pp. 241-46) under the heading, "The 

 Organism as a Whole or the Collective Action of the Genes," seems to 

 imply that organismic pattern is entirely a matter of gene action but does 

 not show how this is possible. In an earlier discussion a very different 

 view was advanced, that differentiation depends on reaction between 

 hereditary factors and regional differences in the egg and embryo which 

 are independent of them.' 



With progress of experimental analysis it has become increasingly difh- 

 cult to separate organism and environment. Not only functional patterns 

 of mature individuals but developmental patterns are highly susceptible 

 to environmental conditions, and it is impossible to conceive an organism 

 except in relation to environment. If life is "the continuous adjustment 

 of internal relations to external relations," as Spencer put it, or a con- 

 tinuous equilibration in reaction to environment, then life is the behavior 

 of protoplasmic systems, and developmental pattern represents certain as- 

 pects of that behavior (Child, 1924&). Surface-interior pattern is so ob- 

 viously a reaction to environmental factors that it need not concern us 

 further here. In addition to surface-interior pattern, all but the simplest 

 organisms possess axiate pattern, and evolution is very largely a matter 

 of modifications of this pattern and of the reactions within it. 



The view commonly held at present is that, whatever the nature of 

 embryonic pattern, it does not originate autonomously in the egg but 

 originates in relation to its intraorganismic environment, that is, to factors 

 in the relations of the oocyte to the parent organism.^ According to Gold- 

 schmidt, however, these factors are controlled by the gene system of the 

 parent. He regards the cytoplasmic pattern as a stratification, the differ- 

 ent levels provicUng substrata for activation of different genes. However, 

 cytoplasmic stratification involves quantitative or qualitative regional 

 metabolic differences; and these, rather than the stratification itself, are 

 the effective factors in development. On this basis heredity alone does 

 not provide a pattern for development but represents the potentialities 

 of the species- or individual-protoplasm ; for the realization of any of these 

 potentialities in development certain environmental conditions are neces- 

 sary. The course of embryonic development is altered when essential fac- 

 tors of the environment are altered; the potentialities realized under ex- 



■ This view appears unaltered in a revised edition of the book by Morgan, Sturtevant, et al., 

 1923 (first published in 1915). 



' See, e.g., E. B. Wilson, 1925, pp. 1021-25; Goldschmidt, 1938, pp. 200-262. 



