10 HEREDITY IN RELATION TO EUGENICS 



tion of the theory of unit characters in its application to 

 man opens up large social, legal and administrative ques- 

 tions and leads us in the interests of truth, to avoid classify- 

 ing persons and to consider rather their traits. 



2. The Mechanism of the Inheritance of 

 Characteristics 



That traits are inherited has been known since man be- 

 came a sentient being. That children are dissimilar com- 

 binations of characteristics has long been recognized. That 

 characteristics have a development in the child is equally 

 obvious; but the mechanism by which they are transmitted 

 in the germ plasm has become known only in recent years. 



We know that the development of the child is started by 

 the union of two small portions of the germ plasm — the egg 

 from the mother's side of the house and the sperm from the 

 father's. We know that the fertiUzed egg does not contain 

 the organs of the adult and yet it is definitely destined to 

 produce them as though they were there in miniature. The 

 different unit characters, though absent, must be represented 

 in some way; not necessarily each organ by a particle but, 

 in general, the resulting characteristics are determined by 

 chemical substances in the fertilized egg. It is because of 

 certain chemical and physical differences in two fertilized 

 eggs that one develops into an ox and the other into a man. 

 The differences may be called determiners. 



Determiners are located, then, in the germ cells, and 

 recent studies indicate a considerable probability that 

 they are to be more precisely located in the nucleus and 

 even in the chromatic material of the nucleus. To make 

 this clear a series of diagrams will be necessary. 



Figure 1 is a diagram of a cell showing the central nucleus 

 in which runs a deeply staining network — the chromatin. 

 In the division of a cell into two similar daughter cells the 



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