CONTENTS xi 



PART VII 



PAGE 



VARIATION STEPS 178 



Examples — Diverse Series of Variation Steps^ Variation Steps of the 

 First, Second and Third Degree — Symmetry and Variation Steps- 

 Relation between Mean Value and Variation Steps — Transformation 

 of a Monomorphic Curve into a Dimorphic or a Polymorphic one by 

 External Causes — Influence of Selection upon Variation Steps — Dis- 

 continuous Variation, Variation Steps and Specific Difference — Rela- 

 tion between Variation Steps and Phyllotaxis — Methods for the 

 Discovery of Variation Steps — Embryological Series — Parallel Varia- 

 tion : Mechanical Concordance, Embryological Parallelism, Parallel 

 Variation Steps 



PART VIII 



GRADATION 198 



Comparison between Living Beings and Crystals — The Axes of the 

 Crystals are Lines of Stability — The Axes of the Living Beings are also 

 Lines of Stability — Difference between both Sorts of Axes — Examples 

 of Gradation — Independence of the Primordia in Respect of Gradation 

 — Comparison between Gradation Curves and Embryological Curves — 

 The Axes of the Living Beings are Lines of Equilibrium, Ordonnance, 

 Gradation, Segmentation and Differentiation — Various Effects of 

 Gradation 



PART IX 



APPLICATION OF THE QUANTITATIVE METHOD — THE 



DESCRIPTION OF SPECIES 207 



Various Applications of the Quantitative Method — Breach of Continuity 

 in the Development of Biological Science — Vagueness and Incomplete- 

 ness of Specific and Generic Descriptions — Importance of Systematics 

 — Comparative Method — Morphology — Palaeontology — Importance of 

 Collections — Minute Details — The Notion of Species — Independence 

 of Species — Quantitative Description and Identification of Graminea — 

 Constants of Alopecurus pratensis — Tables of Constants — Examples — 

 Methods for using Tables of Identification — Bertillonage 



INDEX . . 223 



