LIST OF ILLUSTJL\TIONS xvii 



PAGE 



57. Oenothera lamarckiana 347 



58. A Series Showing Oenothera lamarckiana and Several of Its 



Mutants Growing Side by Side 352 



59. Diagram Showing in Condensed Form the Genealogy of 



THE Oenothera lamarckiana Family and Its Various Mutants 357 



60. Some Divergent Types (Mutations) of Beetles Produced 



BY Subjecting the Germ Cells to External Influences 361 



61. Two Plants of Onagra biennis, Showing the Effect of 



Injections of Zinc Sulphate into the Ovule .... 362 



62. Polygon of Variation for the Total Number of Scutes in 



THE Nine Bands of the Armadillo 366 



63. BiMODAL Polygon Plotted from Data on the Earwig . . 369 



64. Correlation Table of 400 Plants of Sixty-Day Oats . 370 



65. Diagram of Galton's "Law of Ancestral Inheritance" . 372 



66. Scheme to Illustrate Galton's "Law of Filial Regression " 374 



67. Diagram Illustrating Behavior of Chromosomes in 



Mendel's Cross of Tall and Dwarf Peas 388 



68. Diagram Illustrating Behavior of First Hybrid Genera- 



tion When Inbred 389 



69. Diagram Illustrating Dihybrid Ratio 392 



70. Diagram Showing the Characteristic Pairing, Size Rela- 



tions, and Shapes of the Chromosomes of Drosophila 

 ampelophila 402 



71. Diagram of Mitosis in a Species Having Four Chromo- 



somes in Its Cells 4^4 



72. The Reduction Division as Represented for a Species 



Whose Diploid Number Is Four 406 



73. Diagram of Chromatin Interchange bet\\ten Homolo- 



gous Members of a Pair of Chromosomes 408 



74. Diagram Showing Consequences of Independent Segrega- 



tion OF Chromosomes in Drosophila ampelophila .... 409 



75. Diagram to Show Chromosome Relations in the Inherit- 



ance OF Sex in Drosophila ampelophila 4 1 1 



76. Diagram Showing How the Original Scheme Must Be 



Modified to Satisfy the Presence and Absence Hypothe- 

 sis ^'^ 



77. Diagram Showing How Presence and Absence Scheme Is 



Actually Used *^^^ 



78. Diagram Illustrating Blending Inheritance 416 



