xviii LIST OF ILLUSTRATIONS 



PAGE 



79. DIAGRAM ILLUSTRATING COMPLEMENTARY FACTORS .... 418 



80. DIAGRAM ILLUSTRATING BEHAVIOR OF INHIBITORY FACTOR . . 421 



81. DIAGRAM SHOWING SOME POSSIBLE COMBINATIONS IN F a WHEN 



Fj OF FIGURE 80 Is INBRED 422 



82. DIAGRAM SHOWING THE HETEROZYGOTE SITUATION .... 422 



83. DIAGRAM ILLUSTRATING THE ACTION OF A SUPPLEMENTARY 



FACTOR 423 



84. DIAGRAM ILLUSTRATING NILSSON-EHLE'S EXPLANATION OF THE 



15:1 RATIO IN F a OF HYBRID BETWEEN RED- AND WHITE- 

 GRAINED WHEAT 425 



85. ANOTHER METHOD OF VISUALIZING NILSSON-EHLE'S 15:1 RATIO 426 



86. DIAGRAM OF NILSSON-EHLE'S 63 : i RATIO 427 



87. SEX-LINKED INHERITANCE OF WHITE AND RED EYES IN Droso- 



phila. 434 



88. RECIPROCAL CROSS TO THAT SHOWN IN FIGURE 87 . . . . 435 



89. DRAWING SHOWING THE FOUR PAIRS OF CHROMOSOMES SEEN IN 



THE DIVIDING EGG OF Drosophila 436 



90. DIAGRAM SHOWING THE LOCATION IN THE FOUR PAIRED CHROMO- 



SOMES OF Drosophila, OF THE GENES FOR VARIOUS MENDELIZ- 

 ING CHARACTERS, AS DETERMINED BY MORGAN 437 



91. SEX-LINKED INHERITANCE OF BARRED AND UNBARRED (BLACK) 



PLUMAGE IN POULTRY 438 



92. RECIPROCAL CROSS TO THAT SHOWN IN FIGURE 91 .... 439 



93. DIAGRAM TO SHOW THE MECHANISM OF CROSSING OVER . . . 443 



94. AN ARMADILLO EGG ABOUT Six WEEKS AFTER FERTILIZATION, 



SHOWING THE QUADRUPLET FOETUSES 451 



95. A TYPICAL OPPOSITE-SEXED PAIR OF CATTLE TWINS . . . . 455 



96. A PEDIGREE OF BRACK YD ACT YLISM 460 



97. A PEDIGREE SHOWING TRANSMISSION OF CATARACT .... 461 



98. A PEDIGREE SHOWING HEREDITY OF FEEBLE-MINDEDNESS . . 463 



99. ANOTHER PEDIGREE SHOWING HEREDITY OF FEEBLE-MINDED- 



NESS 464 



100. PEDIGREE SHOWING HEREDITY OF INSANITY 465 



101. PEDIGREE SHOWING HEREDITY OF INSANITY AND NEUROTIC 



TENDENCY 465 



