xii LIST OF ILLUSTRATIONS 



FIG. PAGE 



30. Three mutant types of chromosome-IV group of Drosophila 48 



31. Cross between haplo-IV and diploid eyeless fly . . ... 49 



32. Haplo-IV and triplo-IV female of Drosophila .... 50 



33. Cross between triplo-IV and diploid eyeless Drosophila 

 (upper half of diagram). Continuation of last (lower half of 

 diagram), mating of heterozygous triplo-IV to diploid eye- 

 less 51 



34. Primary non-disjunction. XX-egg fertilized by Y-sperm . . 53 



35. Non-disjunction. White-eyed XXY female fertilized by red- 

 eyed XY male 54 



36. Superfemale of Drosophila. (2n + 3X) 56 



37. Fertilization of egg with attached X (double yellow female) 



by sperm of wild-type male 57 



38. Sex-linked inheritance of the mutant type, white eyes of 

 Drosophila 60 



39. Sex-linked inheritance of a light-colored mutant type lacti- 

 color of Abraxas 61 



40. Head of mutant type of Drosophila, Lobe 2 (eye) .... 62 



41. Mutant type of Drosophila, Curly wings 63 



42. Oenothera Lamarckiana and 0. gigas 69 



43. Combs of domestic races of fowls 73 



44. Mutant type — Notch wings — of Drosophila 78 



45. Inheritance of Notch wings 79 



46. Notch- deficiency; duplication of not-vermilion; duplication 



of not-yellow 80 



47. Fertilization of egg-cell of flowering plant, and develop- 

 ment of endosperm 83 



48. Triploid condition of (a) two floury genes versus one flinty 

 gene; (a') two flinty versus one floury gene 84 



49. Types of bar-eye of Drosophila 87 



50. Diagram of bar female heterozygous for forked and fused, 



by forked bar fused male 88 



51. Diagram of crossing-over of bar; of infra-bar; of bar-infra- 

 bar 90 



52. Diagram of crossing-over of bar-infra-bar heterozygous for 

 forked and fused; of infra-bar-bar heterozygous for forked 



and fused 91 



53. Cross between two species of tobacco 96 



54. Cross between two species of snapdragon 97 



