LIST OF ILLUSTRATIONS xvii 



PIG. P^GE 



110. Chromosome groups of perennial and annual teosinte . . 196 



111. Chromosome groups of two species of poppies and that of 

 hybrid ■^^' 



112. Male and female chromosome groups of Protenor . . . 200 



113. Male and female chromosome groups of Lygaeus .... 200 



114. Diagram of XX-XY type of sex determination .... 201 



115. Sex-linked inheritance of white eyes of Drosophila . . . 202 



116. Chromosome groups in man 203 



117. Separation of X- and Y-chromosomes in spermatogenesis in 

 man 204 



118. Diagram of WZ-ZZ type of sex-determination .... 205 



119. Male and female chromosome groups in fowl 206 



120. Sex-linked inheritance in poultry 207 



121. Sex-linked inheritance in a moth, Abraxas 208 



122. Chromosomes of egg of moth, Fumea 209 



123. Sex-determination in dioecious plants 213 



124. Female and male prothallia of liverwort, with respective 

 haploid chromosome groups 215 



125. Method of combining male- and female-determining groups 



of mosses 217 



126. Separation of X-chromosome from autosomes in Ascaris . 219 



127. Diagram of sex detennination when the X-chromosomes are 

 united to autosomes 220 



128. Diagram of paternal inheritance in a fish, Lebistes, with 

 erossinsr-over between X and Y 223 



129. Diagram of inheritance of white versus red body-color of fish 224 



130. Diagram of second generation from last 225 



131. Diagram of inheritance of white and red body-color of fish 

 with crossing-over between X and Y 226 



132. Diagram of theoretical crossing-over between autosomes to 

 which the X-chromosomes are attached 227 



133. Two maturation divisions of bearberry aphid 229 



134. Polar spindle of male-producing egg, and polar spindle of 

 female-producing egg of Phylloxera 230 



135. Two maturation divisions of sperm-cells of Rhabditis . . 231 



136. Two maturation divisions (polar body formation) of egg 



of Rhabditis 232 



137. Parthenogenetic female, male-egg-producing female, sexual 

 egg-producing female, and male of Brachionus .... 234 



