Growth Integration 107 



port of the strictures here placed upon the value of this 

 explanation of growth is well brought out by Moeser, who 

 says, probably with literal truthfulness, "One will not find 

 two germinating plants (Keimpflanzen) which would have 

 exactly the same growth curve, even though they proceed 

 from seed of absolutely the same weight and grow under 

 exactly the came conditions." 



The kernel of this criticism is that even though it should 

 be established, as very likely it will be, that autocatalytic 

 action is an essential factor in all growth, it can be a causal 

 explanation in only a partial and subordinate sense. This is 

 so because although K is a constant for a particular indi- 

 vidual as observed, it assumes different values for different 

 groups, partly at least because no account is taken of size 

 or configuration. Moreover, even if these factors were con- 

 sidered, there would be nothing corresponding to a physical 

 constant (depending only on autocatalytic action), since 

 one of the most distinctive things about organic growth is 

 that it is differential, the differentials corresponding to the 

 taxonomic group to which the individuals belong. 



Even though we are still much in the dark as to what the 

 causal nexus is between the growth processes and the quan- 

 titatively graded series so widely seen in nature, it seems 

 certain that some such nexus exists, and that its operation 

 constitutes a true integrational factor in the individual. It 

 appears, too, that this type of integration is about the 

 simplest and that it accompanies the simplest type of dif- 

 ferentiation, the two together constituting the simplest type 

 of organization above the organization of the cell. But into 

 this interesting subject we can not now go. 



Axial Metabolic Gradients as Integrative Phenomena 



For the most thorough and sustained experimental inves- 

 tigation of the primary intcgrative processes in growing 



