ALTERATION OF THE AXIAL GRADIENT. 221 



regions, does die. In shallow crystallizing dishes with a liter of 

 water fifty per cent, more or less of the cells may die, in more 

 extreme conditions a higher percentage, up to one hundred per 

 cent, in a closed flask, and under less extreme conditions a smaller 

 percentage. 



In all cases, however, where conditions are not too extreme a 

 certain percentage of the cells may remain alive, and after a time 

 resume growth and development. In short, these depressing 

 conditions if not too extreme may be used as a method of ob- 

 taining isolated cells of Griffithsia for purposes of culture. This 

 method is not new, for Tobler, '02, '04, has employed it for this 

 purpose, but the fact that such cell-separation is associated with 

 obliteration or reversal of the axial gradient is new. If, as I 

 believe (Child, '156), the axial gradient is the basis of physiologi- 

 cal polarity, and at the same time the primary integrating factor 

 in axiate individuation, the obliteration or reversal of the gradi- 

 ent must mean both obliteration or reversal of the original 

 polarity and physiological disintegration of the individual, in 

 other words, the elimination of the physiological order or pattern 

 associated with and resulting from the existence of the gradient. 

 With this physiological disintegration of the individual its com- 

 ponent parts, the cells, become more or less completely physio- 

 logically isolated (Child, '156). The fact that physiological 

 disintegration of the individual is soon followed by physical 

 separation of the cells is of great interest, as indicating the very 

 direct dependence in this simple individual, of the gross morpho- 

 logical order upon the dynamic integrating factor. 



Moreover, if the gradient is the basis of physiological polarity, 

 we may expect that the further growth and development of these 

 isolated cells will be influenced in one way or another by the 

 obliteration or reversal of the original gradient. If the original 

 gradient is completely or to a large extent obliterated in a cell, 

 a new gradient or gradients may be established by "chance" 

 differentials in external conditions, or may be determined 

 experimentally. If reversal of the original gradient persists for 

 any considerable time, the order and axiation in the further 

 development may be determined by this factor. In the following 

 section the development of some of these isolated cells is de- 

 scribed, and its relation to susceptibility gradients demonstrated. 



