ORIGINS OF EMBRYONIC PATTERNS 645 



lem in terms of distribution of hypothetical hereditary units but tells us 

 nothing about the ordering and controlling principle determining the dis- 

 tribution so that an orderly organism of definite character results. It 

 would seem that this principle must be endowed with superhuman intelli- 

 gence and with knowledge of the end to be attained in order to get each 

 determinant into its proper cell and to supply the cell with accessory de- 

 terminants to provide for possible regeneration. The theory is implicitly 

 teleological. 



Driesch, assuming that developmental pattern is independent of en- 

 vironment in origin, drew the logical conclusion that a metaphysical order- 

 ing and controlling principle, the entelechy, is necessary. Various other 

 authors have assumed an inherent, form-determining principle, teleologi- 

 cal in character. As a matter of fact, the conception of developmental 

 pattern as independent of environment seems to demand a teleological 

 principle. If we reject the hypothesis of a metaphysical origin of organis- 

 mic order and pattern, the question whether autonomy of pattern is pos- 

 sible on any other basis arises. Can the gene system alone originate a 

 spatial pattern in a cell or a cell mass? Or is the intimate structure of 

 molecular or other character, so often postulated as the basis of pattern, 

 an inherent property of protoplasms? If not, can it arise spontaneously, 

 that is, without relation to any external factor? 



It was held by Rabl (1885) and others that the nucleus possesses polar- 

 ity coincident with the axis of the mitotic spindle, since the recurved 

 middle portions of the chromosomes lie toward the spindle pole. How- 

 ever, even if cell polarity is of this sort, it does not account for polarity 

 of a multicellular organism, for polarities of the two cells resulting from 

 division are in opposite directions. A nuclear polarity indicated by ag- 

 gregation of chromatin toward a certain region of the nuclear periphery 

 appears frequently under certain conditions or at certain stages but is ob- 

 viously a reaction to something outside the nucleus rather than a primary 

 factor of pattern. The general nuclear pattern and the chromosome pat- 

 terns are apparently entirely different from the pattern of the organism. 

 How a gene, a group of genes, or the whole gene system can originate 

 autonomously in the cytoplasm, a spatial pattern involving polarity and 

 symmetry or asymmetry, is not evident. Each nucleus supposedly con- 

 tains the whole gene system. "Each cell inherits the whole germ plasm" 

 (Morgan, 1919, p. 241). If different gene effects occur in different cells 

 or in different localized regions of the same cell, it seems that they must 

 be localized in relation to something, a differential or pattern of some sort 



