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 Chapter 15. — Experimental Method of Investigating Heredity.. 81 



(a) Mendelism 81 '^ 



Simple Mendelian Segregation 86 



Dihybrids 87 



Trihybrids 88 



(b) Dominant and Recessive Characters 91^ 



Meaning of Dominant and Recessive 95 



The F Generation 96 



Conception of the Germ Cells 96 



(c) Additional Examples of Simple Mendelian 



Hybrids 96 



Maize 97 



Peaches and Nectarines 98 



Pin-eye and Thrum-eyed Primroses 98 



Colors in Live Stock 100 ^ 



(d) Abnormal cases of Mendelism ._. 101 



Imperfect Dominance 101 



Multiple Factors 102 



Compound Factors 104 



Linkage and Crossing-over 109 



Color blindness 110 



Drosophila Hybrids 112 



Hybrids of Dorset and Suffolk Sheep U4 



Hybrids of Abraxas moths 115 



Fo^^';l Hybrids 116 



Egg production in Fowls 118 



Laboratory Exercises with Drosophila 120 



Crossing-over 121 -^ 



(e) Endosperm Inheritance 124' 



(f) Breeding for Quality and Quantity of Milk.... 124 



(g) Atavism and Reversion 125 



(h) Inheritance in Aphids or Plant Lice 126 



Chapter 16. — Biologic Method of Investigating Heredity 129 



(a) The Cell in Heredity 129 



(b) Number of Chromosomes 131 



(c) Maturation and Reduction 133 



(d) The Chromosome Theory of Heredity 137 



(e) Structure of Chromosomes 139 



(f) Changes in Chromosomes 139 



(g) Heredity of Sex ..141 



(h) The Control of Sex 144 



Chajjter 17. — In-breeding 146 



Chapter 18. — A Comparison of Plant and Animal Breeding 152 



(a) Animal Improvement 152 



(b) Plant Improvement 154 



Selection of Fluctuations 156 



Canadian Grains 157 



Grain Breeding in Sweden 158 



Breeding Varieties of Plants that are Disease — 



Resistant 159 



Chapter 19. — Eugenics and Euthenics 161 



Mendelism of Human Characters 163 



Alcohol and Heredity 169 



Venereal Diseases and Heredity 170 



Chapter 20. — Important Events in the History of Genetics .. ..171 



Chapter 21. — Important Literature 174 



Glossary 1"7 



Index 1^^ 



