PHYSIOLOGICAL DOMINANCE 125 



zation" of the species reduced to its lowest terms. The 

 minimal size can be altered widely even now by con- 

 trolling conditions, and I have no doubt that if we are 

 ever able to isolate single cells and to provide proper 

 nutritive and other conditions for them we shall find that 

 in many of the lower animals such cells are capable of 

 giving rise to new individuals, as they undoubtedly are 

 in many plants. 



Most investigators have regarded the minimal size 

 of pieces undergoing reconstitution as something abso- 

 lute and have failed entirely to note that it differs with 

 the physiological condition of the animal, the region of 

 the body, and the various external conditions which 

 affect metabolic rate. To determine the smallest piece 

 of animal capable of reconstitution under given con- 

 ditions is merely to determine one special case out of an 

 indefinite number of possible cases. 



CONCLUSION 



The experimental evidence demonstrates, first, the 

 essential independence of the apical region in both 

 plants and animals, and, secondly, determination and 

 control by this apical region of the developmental 

 processes at other levels of the major axis of the indi- 

 vidual. The reconstitution of pieces into new individ- 

 uals is fundamentally the same process as embryonic 

 development, and the same relation of dominance and 

 subordination exists in both. The different results of 

 reconstitution in pieces of different size, from differ- 

 ent levels, in different physiological conditions, under 

 different environmental conditions, etc., depend pri- 

 marily upon relations of dominance and subordination, 



