xvi LIST OF ILLUSTRATIONS 



FIG. PAGE 



82. Diploid and triploid Drosophila 135 



83. Constriction of egg of Triton isolating one half with a 

 single sperm 140 



84. Haploid plant of Datura 143 



85. Diagram of two maturation divisions of egg of bee, and fer- 

 tilization of egg by sperm 144 



86. Two maturation stages of the germ-cell of the honey bee . 146 



87. Parthenogenetic female, sexual female, and male, of Hyda- 

 tina 147 



88. Chromosomes of diploid, tetraploid, and hexaploid wheats . 151 



89. Normal maturation divisions of Einkorn, Emmer, and Vul- 

 gare wheats 153 



90. Maturation divisions of hybrid between Emmer and Vulgare 

 wheats 154 



91. Same as last, illustrating a somewhat different account of 

 process 155 



92. Multiple chromosome groups of roses 159 



93. Maturation division of pollen cells of a hybrid rose . . . 161 



94. Maturation division of egg-cell of a hybrid rose .... 162 



95. Five types of hybrid canina roses 164 



96. Maturation of pollen of Hieracium 166 



97. Chromosomes of chrysanthemums 167 



98. Nuclear sizes of varieties of chrysanthemums 168 



99. Chromosomes of chrysanthemums 168 



100. Oenothera lata, heterosomic type 173 



101. Mutant types of seed capsules of Datura 178 



102. Normal and heterosomic (2n -f 1 and 2n -f 2) types of seed 

 capsules of Datura 179 



103. Tetraploid and heterosomic tetraploid types of Datura . . 183 



104. Union of chromosomes in Primary and Secondary types of 

 Datura 184 



105. Diagram of hypothetical reversal of conjugating chromo- 

 somes 185 



106. Conjugation of chromosomes of Primary and Secondary 

 heterosomic types of Datura 186 



107. Imaginary relation of mutant types to specific chromosomes 



in Oenothera 188 



108. Diploid and haploid chromosome groups of Drosera . . . 191 



109. Chromosome groups of Crepis setosa and C. biennis and that 



of hybrid 195 



