LIST OF ILLUSTRATIONS xxiii 



FIGUBE PAGE 



57. Diagram Illustrating Dihybrid Ratio 244 



58. Diagram Showing How the Original Scheme Must Be Modi- 



fied To Satisfy the Presence and Absence Hypothesis . 254 



59. Diagram Showing How Presence and Absence Scheme Is 



Actually Used 255 



60. Diagram Illustrating Blending Inheritance .... 256 



61. Diagram Illustrating Behavior of Complementary Factors 258 



62. Diagram Illustrating Behavior of Inhibitory Factor . . 261 



63. Diagram Showing Some Possible Combinations in F_, When 



Fj of Figure 62 Is Inbred 262 



64. Diagram Showing the Heterozygote Situation .... 262 



65. Diagram Illustrating Action of Supplementary Factor . 263 



66. Diagram Illustrating Nilsson-Ehle's Explanation of the 



15:1 Ratio in F 2 of Hybrid between Red- and White- 

 Grained Wheat 265 



67. Another Method of Visualizing Nilsson-Ehle's 15:1 Ratio 266 



68. Diagram Illustrating Nilsson-Ehle's 63 : 1 Ratio . . . 267 



6q. Sex-Linked Inheritance of White and Red Eyes in Droso- 



pl/ilii 280 



70. Reciprocal Cross to That Shown in Figure 60 ... 281 



71. Sex-Linked Inheritance of Barred and Unbarred (Black) 



Plumage in Poultry 282 



72. Reciprocal Cross to That Shown in Figure 71 . . . . 283 



73. Diagram Showing the Mechanism of Crossing-over . . 291 



74. The Chromosome Map of Drosophila melanogaster .... 295 



75. Oenothera lamarckiana 314 



76. A Series Showing Oenothera lamarckiana and Several of Its 



Mutants Growing Shoe by Side 319 



77. Diagram Showing in C< >ndensed Form the Genealogy of the 



Oenothera lamarckiana Family and Its Various Mutants . 324 



78. Fierasfer acus, Penetrating the Anal Openings of Holothur- 



IANS 35S 



79. Kallima, the "Dead-Leaf Butterfly" 364 



80. Three Aquatic Types of Vertebrate, To Illustrate Con- 



vergent Adaptation 367 



81. Pedigree Showing Heredity of Brachydactyly .... 451 



