LIST OF ILLUSTRATIONS 19 



FIG. PAGE 



56. Chiasmata 119 



57. Length-chiasma relation 120 



58. Chiasmata and crossing over 122 



59. Proofthat some chiasmata involve crossing over 123 



60. Cross over maps in maize 124 



61. Distribution of chiasmata and crossing over 125 



62. Chromosome interlocking 127 



63. Compound crossing over 128 



64. Crossing over in inversions 130 



65. Relational coiling and crossing over 132 



66. The equal division of the nucleus 138 



67. Organ-forming substances in Ascidians 142 



68. Right- and left-handed Gastropods 142 



69. Limnea 143 



70. Activation and differentiation centres in insects 144 



71. Gradients in echinoderm eggs 146 



72. Organizers in amphibia 148 



73. Organizers and pattern 150 



74. Specific differences and competence 151 



75. Acetabularia 153 



76. Polymeric genes 159 



77. Dihybrid ratios 161 



78. Dose-effect curve of bobbed 164 



79. Dosages of shaven 165 



80. Vortex 169 



81. Radish-cabbage hybrids 171 



82. Rates of development 174 



83. The anthocyanin molecule 176 



84. Eye colours in Drosophila 178 



85. Time-effect and dose-effect curves 181 



86. Pigment formation in Drosophila 183 



87. Evolution of dominance 185 



