xiv Contents 



A DEFENCE OF MENDEL'S PRINCIPLES OF 



HEREDITY, 104208. 

 Introductory, 104. 



I. THE MENDELIAN PRINCIPLE OF PURITY OF GERM-CELLS 



AND THE LAWS OF HEREDITY BASED ON ANCESTRY, 108. 



II. MENDEL AND THE CRITIC'S VERSION OF HIM. 

 The Law of Dominance, 117. 



III. THE FACTS IN REGARD TO DOMINANCE OF CHARACTERS IN 



PEAS, 119. 



The normal characters : colours of cotyledons and seed- 

 coats, 120. Shape, 122. Stability and variability, 124. 

 Results of crossing in regard to seed-characters : normal and 

 exceptional, 129. Analysis of exceptions, 132. The "mule" 

 or heterozygote, 133. 



IV. PROFESSOR WELDON'S COLLECTION OF "OTHER EVIDENCE 



CONCERNING DOMINANCE IN PEAS." 



A. In regard to cotyledon colour: Preliminary, 137. 

 Xenia, 139. (1) Gartner's cases, 141. (2) Setou's case, 143. 

 (3) Tschermak's exceptions, 145. (3 a) Buchsbaum case, 145. 

 (3 b) Telephone cases, 146. (3 c) Couturier cases, 147. 



B. Seed-coats and Shapes. 1. Seed-coats, 148. 2. Seed- 

 shapes : (a) Rimpau's cases, 150. (6) Tschermak's cases, 152. 

 3. Other phenomena, especially regarding seed-shapes, in 

 the case of "grey" peas. Modern evidence, 153. 



C. Evidence of Knight and Laxton, 158. 



D. Miscellaneous cases in other plants and animals : 



1. Stocks (Mattkiola). Hoariness, 169. Flower- 

 colour, 170. 



2. Datura, 172. 



3. Colours of Rats and Mice, 173. 



V. PROFESSOR WELDON'S QUOTATIONS FROM LAXTON, 178. 



Illustration from Primula sinensis, 182. 



VI. THE ARGUMENT BUILT ON EXCEPTIONS, 183. 



Ancestry and Dominance, 185. 

 Ancestry and purity of germ-cells, 193. 

 The value of the appeal to Ancestry, 197. 



VII. THE QUESTION OF ABSOLUTE PURITY OF GERM-CELLS, 201. 

 CONCLUSION, 208. 



