CHAPTER II 



THE PHYSIOLOGICAL BASIS OF AXIATE PATTERN 

 THE PHYSIOLOGICAL GRADIENT 



The cell is primarily an organism, though it may be 

 integrated with other cells to form a part of a multicel- 

 lular organism. While we have no positive knowledge 

 concerning the origin of cell pattern, the structure of 

 the cell in general suggests that it is primarily what we 

 may call a surface-interior pattern. If this is true, the 

 differentiation of nucleus and cytoplasm from the primi- 

 tive protoplasm, possessing in some degree the functions 

 of both, must have resulted in the first instance from 

 differences and relations between exterior and interior. 

 Some organisms appear to be even simpler in pattern 

 than the ordinary cell, but most of them are so minute 

 and show so little differentiation of parts that our 

 knowledge of their pattern is very fragmentary. Even 

 in the simplest organisms, however, we should expect 

 to find at least a surface-interior pattern. In the 

 absence of any positive data, further discussion of the 

 origin of cell pattern and of still simpler patterns is of 

 value only in the light of what we can learn concerning 

 other organismic patterns and is therefore postponed 

 (see p. 60) . 



The surface-interior pattern is primarily a com- 

 pletely radial, spherically symmetrical or centered 

 pattern and, assuming that organismic pattern arises 

 through relation between protoplasm and environment, 



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