Cambridge, March, 1911.

CONTENTS

CHAPTER I
PAGE
The Problem [1]
CHAPTER II
Historical [8]
CHAPTER III
Mendel's Work [17]
CHAPTER IV
The Presence and Absence Theory [29]
CHAPTER V
Interaction of Factors [42]
CHAPTER VI
Reversion [59]
CHAPTER VII
Dominance [68]
CHAPTER VIII
Wild Forms and Domestic Varieties [79]
CHAPTER IX
Repulsion and Coupling of Factors [88]
CHAPTER X
Sex [99]
CHAPTER XI
Sex (continued) [115]
CHAPTER XII
Intermediates [125]
CHAPTER XIII
Variation and Evolution [135]
CHAPTER XIV
Economical [153]
CHAPTER XV
Man [170]
APPENDIX [187]
INDEX [191]

ILLUSTRATIONS

PLATES
PLATE PAGE
Gregor Mendel Frontispiece
I. Rabbits To face [60]
II. Sweet Peas " [64]
III. Sheep " [78]
IV. Sweet Peas " [80]
V. Fowls " [107]
VI. Butterflies " [146]

FIGURES IN TEXT
FIG.
1. Scheme of Inheritance in simple Mendelian Case [21]
2. Feathers of Silky and Common Fowl [30]
3. Single and Double Primulas [31]
4. Fowls' Combs [32]
5. Diagram of Inheritance of Fowls' Combs [37]
6. Fowls' Combs [39]
7. Diagram of F2 Generation resulting from Cross between two White Sweet Peas [46]
8. Diagram illustrating 9 : 3 : 4 Ratio in Mice [52]
9. Sections of Primulas [55]
10. Small and Large-eyed Primulas [55]
11. Diagram illustrating Reversion in Pigeons [67]
12. Primula sinensis × Primula stellata [68]
13. Diagram illustrating Cross between Dominant and Recessive White Fowls [72]
14. Bearded and Beardless Wheat [75]
15. Feet of Fowls [76]
16. Scheme of Inheritance of Horns in Sheep [76]
17. Abraxas grossulariata and var. lacticolor [99]
18. Scheme of Inheritance in Abraxas [102]
19. Scheme of Inheritance of Silky Hen × Brown Leghorn Cock [105]
20. Scheme of Inheritance of Brown Leghorn Hen × Silky Cock [106]
21. Scheme of F1 (ex Brown Leghorn × Silky Cock) crossed with pure Brown Leghorn [107]
22. Scheme for Silky Hen × Brown Leghorn Cock [108]
23. Scheme for Brown Leghorn Hen × Silky Cock [109]
24. Diagram illustrating Nature of Offspring from Brown Leghorn Hen × F1 Cock [111]
25. Scheme to illustrate Heterozygous Nature of Brown Leghorn Hen [111]
26. Scheme of Inheritance of Colour-blindness [117]
27. Single and Double Stocks [122]
28. F2 Generation ex Silky Hen × Brown Leghorn Cock [127]
29. Pedigree of Eurasian Family [131]
30. Curve illustrating Influence of Selection [159]
31. Curve illustrating Conception of pure Lines [162]
32. Brachydactylous and Normal Hands [170]
33. Radiograph of Brachydactylous Hand [170]
34. Pedigree of Brachydactylous Family [173]
35. Pedigree of Hæmophilic Family [175]