NOTES ON CHAPTER I 



^ Page 3. See the discussion of this matter in H. F. Osborn, "Aristo- 

 genesis, the Creative Principle in the Origin of Species," American 

 Naturalist, Vol. 68, 1934, pp. 193-235. 



2 Page 6. For detailed accounts of the constitution of the germ plasm — 

 the chromosomes and genes — see some modern text-book of cytology; 

 for example, L. W. Sharp's Introduction to Cytology (New York, 

 1934), or E. B. Wilson's The Cell in Development and Inheritance 

 (New York, 1928). For details as to their relation to genetics, some 

 detailed text-book on that subject may be consulted, such as the author's 

 Genetics (New York, 1935), or Sinnott and Dunn's Principles of 

 Genetics (New York, 1932). A simplified account of both of these mat- 

 ters will be found in the present author's The Biological Basis of 

 Human Nature (New York, 1930). 



^ Page II. Practically all statements in biology are subject to exceptions. 

 A certain limited number of needed genes may be lacking in the set 

 supplied by one of the parents. 



* Page 13. As will be shown in Chapter III, some or all of these "mod- 

 ifications" of a particular gene may possibly be simply the same gene 

 in different relations to other genes, and yielding different effects on 

 account of these different relations. For the present the text follows the 

 account commonly given. 



^ Page 18. There is a tendency for two genes that are close together in 

 the maternal series or in the paternal series to remain together in the 

 offspring. But this is not fixed or absolute; genes that are side by side 

 may separate into different offspring. 



® Page 21. Description and plate on this in Wm. Bateson, Mendel's 

 Principles of Heredity, 1909, p. 294 and Plate VI. 



