36 Spieazines 



transmitted to the new chromosomes that are 

 being formed within the nucleus. The spirazine 

 hypothesis, on the other hand, teaches that the 

 seat of heredity must always consist of a coordi- 

 nated system of spirazines, and that the urea and 

 guanidine derivatives which may at times be lib- 

 erated by certain configurations of spirazines in 

 the nucleus can serve only as chemical messengers 

 or intracellular hormones by means of which the 

 various configurations of spirazines in the nu- 

 cleus can exert their specific influences upon the 

 other portions of the cell. It appears from the 

 spirazine hypothesis that heredity takes place in 

 two different ways. The inheritance of major 

 characteristics, such as the arrangements of the 

 various tissues and organs by which the larger 

 groups of plants and animals are distinguished 

 from one another, is probably determined directly 

 by the cross-sectional pattern of the nuclear 

 spirazine structures and would not be subject to 

 MendePs laws; whereas the inheritance of minor 

 or modifying characteristics, such as the colors 

 or textures of tissues or organs already present, 

 is probably determined by substances in a dis- 

 persed or molecular state which have been liber- 

 ated by the nuclear spirazine structures, and the 

 inheritance of such minor characteristics would 

 be governed by Mendel's laws. 



