CONTENTS 



CHAP. 



I. Introduction. Relation of Heredity to other branches of 



knowledge. The questions to be answered . page 1 



II. Variation. Occurrence and kinds of Variation. Con- 



tinuous variation and methods of study. Discontinuous 

 variation. Inborn and acquired characters . 7 



III. The Causes of Variation. Mutation. Action of en- 



vironment on body and germ-cells. Variation on cross- 

 ing. Relative importance of * inherent' and 'acquired' 

 characters 22 



IV. The Statistical Study of Heredity. Two methods of 



studying Heredity. The biometrical method. Corre- 

 lation and Regression. Parental correlation and the 

 Law of Ancestral Heredity. Heredity in 'pure lines' 

 (Johannsen etc.). Inheritance of 'mental and moral' 

 characters in Man. Eugenics .... 32 



V. Mendelian Heredity. Mendel's Law illustrated. Segre- 



gation and Allelomorphism. Crosses concerning more 

 than one pair of characters. Examples of Mendelian 

 characters in Plants and Animals. Combs of Fowls. 

 The Andalusian Fowl 52 



VI. Mendelian Heredity (continued). The Inheritance 



of Colour. Concurrence of two factors in the pro- 



