TEXT FIGURES 



FIGURE PAGE 



45. The inheritance of direction of coiling in snails 192 



46. Mitosis in the red and wliitc blood precursor cells of man 194 



47. The differentiation of nuclear behaviour in Scilla pollen grains 196 



48. Cleavage and chromosome fragmentation in Asciiris 197 



49. Co-operation bet\\-een pollen grains in Uvularia 199 



50. Types of embryo-sac in terms of cell gradients 200 



51. Haploid competition, including the Rcnner Effect 201 



52. Nucleus and cytoplasm in differentiation 204 



53. The three levels of genetic structure 221 



54. Differing balances in the homo- and hetero-gametic sexes of 

 hybrids 229 



55. Sex balance in Drosophila 231 



56. Chromosome behaviour and pollen fertility in Festtica-Lolium 

 hybrids 233 



57. Heterosis and inbreeding depression in maize 236 



58. Incompatibility in sweet cherries 244 



59. The mechanism of incompatibility 245 



60. Hetcrothally governed by two loci in fungi 246 



61. The efficiency of hetcrothally as an outbreeding mechanism 247 



62. Distyly in Primula 250 



63. Tristyly in Lythrtim 251 



64. The breakdown of incompatibility in Petunia 257 



65. Temperature and sex determination 264 



66. Sexual and non-sexual forms in Artemia 265 



67. The leaves o f triploid and hypo-triploid Taraxacum 266 



68. Sexuality and apomixis in Taraxacum species 267 



69. Types of twinning in plants and animals 270 



70. The release of potential variability 280 



71. The states of variability 281 



72. Litter size and fertility in pigs 284 



73. Selection in Drosophila 286 



74. Seasonal variation of gene frequency in Adalia 295 



75. The mechanism of correlated response to selection 299 



76. Geographical variation in Microtus 304 



77. Isolating mechanisms 307 



78. Inversion phylogeny in Drosophila 313 



79. The isolating effect of inversion 315 



80. Three types of interchange evolution 317 



81. Genetic changes in species formation 319 



82. Chromosome phylogeny in woody plants 325 



83. The Rhesus blood groups in man 333 



84. Sex-ratio inversions in Drosophila azteca 337 



85. The fatuoid series in oats 339 



86. Heterocaryosis in fungi 343 



87. Mating restrictions in plants, animals and man 357 



88. A and b. The distributions of the O blood group gene and the 



TH sound in Europe 362-3 



12 



