l68 C. M. CHILD. 



tions and interactions as the formative factors or by adopting a 

 vitalistic point of view. In any case the formative substances 

 are inadequate to produce the observed result. 



But the crystallization hypothesis has found no wide accept- 

 ance. Most authorities agree that the process of formation of 

 the various parts of organic structure is at least in most cases 

 either only very remotely similar to the process of crystallization 

 or differs totally from it. It may be that in certain cases the 

 process of morphogenesis is akin to crystallization but the results 

 of experimental work demonstrate that in very many cases it 

 certainly is not. 







ULTIMATE UNITS GROUPS OF DISSIMILAR MOLECULES. 



The other alternative under the preformation hypothesis, viz., 

 that which assumes the ultimate units or formative substances 

 to be something more than molecules or groups of like mole- 

 cules, also presents certain difficulties. 



These complexes must be either simply physical mixtures or 

 complexes or they must be molecular complexes of some other 

 kind. 



If we consider them as physical complexes then their formative 

 activity is the result of the relations between parts or of these 

 relations plus a given environment, /. c., none of the substances 

 can be regarded as in itself formative but only the complex as a 

 whole or the complex plus the environment. 



Now if the formative substance is a mixture or other physical 

 complex whose activity depends only or primarily on relations 

 between its parts why does its activity appear only at a certain 

 time? If we admit that the environment, /. e., relations with 

 other elements, etc., play a determining role then these relations 

 are just as truly formative as the complex on which they act. 

 Moreover, as in the case considered under the previous heading 

 we must either assume that the characteristic arrangement of the 

 elements in developed structure is due to physico-chemical rela- 

 tions between the different complexes or we must take refuge in 

 vitalism. But let us assume that the ultimate element is a com- 

 plex of molecules of some other sort, i. e., that it possesses a 

 certain " organization." Physics and chemistry recognize at 



