CONTENTS 



CHAPTER VII 

 DEVELOPMENT OF ORGANISMS 



PAGES 



The Egg-cell or Ovum — Spermatozoon or Male Cell — Spermato- 

 genesis and Oogenesis — Reducing or Meiotic Division — Fertilisation — 

 Segmentation — Gastrula — Gastraea-theory — Organic Continuity or 

 the Continuity of the Germ-cells-^Recapitulation Doctrine — 

 Modern Trends in Embryology — Experimental Embryology illus- 

 trated — Spemann's Idea of Organisers — Organic Regeneration — 

 Life-histories — The Curve of Life — Factors determining life's Trajec- 

 tory — Alternation of Generations — Life-histories of Plants — Liver- 

 worts — Mosses — Pteridophytes — Seed-plants — Alternation of Gene- 

 rations in Plants — The Flower in Historical Retrospect — The 

 Meaning of Larvae — The Duration of Ante-natal Life — Viviparity — 

 Duration of Life — Longevity — The Biology of Death — The Play- 

 period among Animals — The Industries of Animals 715-816 



CHAPTER VIII 

 GREAT STEPS IN ORGANIC EVOLUTION 



The Ascent of Life — Palaeontological Sequence — The Successive 

 Geological Periods and their Characteristics — Great Steps in 

 Structural Advance — Origin of Organisms — The Divergence of 

 Plants and Animals — The Apartness of Bacteria — Differentiation 

 of Unicellular Organisms — The Cell-cycle — Beginnings of Reproduc- 

 tion — The Multicellular Body — Beginning of Natural Death — ^The 

 Origin of Sex — Internal Cavities — Bilateral Symmetry — Beginnings 

 of Brains — Origin of Land Plants — Origin of Seeds — Origin of Insects 

 — Origin of Birds — Effect of the Ice Ages — Vanished British Animals 

 — Anachronisms — The Changing World-environment — Often Re- 

 current Ice Ages as Evolutionary Factors — Palaeontography and 

 Present-day Distribution — Can there be Life beyond our World- 

 limits? 8 I 7-9 I I 



CHAPTER IX 



EVOLUTION 



History of Evolution Theory — Vague Greek Evolutionism — Aristotle 

 — Adumbrations of Evolutionism — Evolutionist Philosophers — Pre- 

 Darwinian Biological Evolutionists — Logical Position of the Idea of 

 Organic Evolution — "Evidences of Evolution" — Vestigial Structures 

 — Transformations of Structures — Persistence of Ancestral Habits — 

 Illustration of an Evolutionary Survey of Animals — Evolution of 

 Protozoa — A Theory of Variation in Plants — Growth, Form, and 

 Variation — Mutations in Snapdragons — A Change of Function, as 

 a Method of Evolution — Atavism and Reversion — Analysis of Rever- 

 sionary Phenomena — The Pulse of Evolution — What are Genes? — 

 The Biological Theory of Nurture — Nature and Nurture in Eugenics — 

 Changes of Behaviour among Living Animals — Are the Results of 



