76 C. M. CHILD 



The conclusion that the organism consists fundamentally of 

 a single reaction system which is most closely represented morpho- 

 logically by the apical region or head, or its dominant part, is 

 forced upon us by the facts. Moreover, it is the only conception 

 which enables us to account satisfactorily for the definite, orderly 

 character of development, its progression in general from anterior 

 to posterior regions, the dominance of the growing tipin plants 

 and of the head in animals, and various other morphological 

 and physiological characteristics of organisms. On the other 

 hand, there are no real facts which indicate that the organism 

 consists fundamentally of a multitude of independent determi- 

 nants, factors or entities of any sort. Even the Mendelian phe- 

 nomena do not demonstrate the existence of independent factors 

 as entities, but merely indicate the existence of different capaci- 

 ties in a system, or of a variety of different systems. The locali- 

 zation of the visible realization of a capacity impHes nothing as 

 to the localization of the capacity. Any corpuscular theory of 

 heredity and development demands the assumption of an an- 

 thropomorphic mechanism or 'vitahstic' principle of some sort 

 for the management of the corpuscles. The conception of a 

 fundamental reaction system as the basis of inheritance and 

 development avoids all these as well as other difficulties; is de- 

 veloped from experimental data and brings into line a great 

 number of facts which are very generally ignored by current 

 theory. 



The fundamental reaction system, dominance of the apical 

 region and the axial gradient are all merely different aspects of 

 the same general idea, viz., that the specific protoplasm of any 

 organism consists fundamentally of a single physico-chemical 

 reaction system which we may, if we desire, conceive as made 

 up of a larger or smaller number of fundamentally similar partial 

 systems. This system is the basis of inheritance and its dynamic 

 capacities, the foundation of hereditary characters. The first 

 step in organization and in embryonic development results from 

 the establishment, in one way or another, of some region or 

 portion of this protoplasmic reaction system as a region of higher 



