xii Contents 



CHAPTER PAGE 



IX. Gametic Coupling and Spurious Allelomorphism . 148 



Pollen-Shape and Flower-Colour. Axil-Colour and Sterile Anthers — 

 ( Hooded Standard and Flower-Colour in Sweet Peas. 



X. Heredity and Sex . . 164 



Evidence from Breeding Experiments. Bryonia — Sex-limited Heredity. 

 The Horns of Sheep — Colour-Blindness — Sex and Spurious Allelo- 

 morphism. The Currant Moth — The Cinnamon Canary — The Silky 

 Fowl — Aglia tau — Cytological Evidence — Summary. 



XL Double Flowers 196 



Miscellaneous Cases. Recessive and Dominant Doubling — *'Hose-in- 

 Hose" Flowers — The Special Case of Double Stocks. 



XII. Evidence as to Mendelian Inheritance in Man . 205 



Normal Characters — Diseases and Malformations. Dominants — Sex- 

 limited Dominants — Recessives — Notes on collecting Evidence. 



XIII. Intermediates between Varieties and the "Pure 



Lines" of Johannsen 235 



Intermediates as Heterozygous Forms — Subtraction-Stages of Dominants 

 — Interfering Factors — Fluctuational Forms — "Pure Lines." 



XIV. Miscellaneous Exceptional and Unconformable Phe- 



nomena 245 



Crosses breeding true without Segregation. Parthenogenetic or Apo- 

 gamic Forms. Hieracium — Sexual Forms — Numerical Aberrations 

 — Irregularities of Dominance — Alternation of Generations — Mater- 

 nal Characters in certain Seeds. 



XV. Biological Conceptions in the Light of Mendelian 



Discoveries 266 



Nature of Units — Nature of Segregation — Moment of Segregation — 

 Differentiation of Parts compared with Segregation — Reversion and 

 Variation. " Bush " and " Cupid " Sweet Peas — Mendelian Segre- 

 gation and Species — Discontinuity in Variation — Mendelism and 

 Natural Selection. 



XVI. Practical Application of Mendelian Principles . 291 



Meaning of Pure-bred — Roguelng — Raising Novelties — A Practical Ex- 

 ample — Unfixable Types — Technical Methods — Sociological Appli- 

 cation. 



Appendixes 307 



PART II. 



1. Biographical Notice of Mendel 327 



2. Translation of the Paper on Hybridisation . . . 335 



3. Translation of the Paper on Hieracium .... 380 



Bibliography 387 



Index of Subjects 403 



Index of Authors 411 



