CONTENTS. XI 



PAGE 



Stereometrical Fundamental Forms of Crystals and of Organisms. — 

 Organic and Inorganic Forces. — Yital Force. — Growth and Adapta- 

 tion in Crystals and in Organisms, — Formative Tendencies of 

 Crystals. — Unity of Organic and Inorganic Nature. — Spontaneous 

 Generation, or Archigony. — Autogony and Plasmogony. — Origin of 

 Monera by Spontaneous Generation. — Origin of Cells from Monera. 

 — The Cell Theory. — The Plastid Theory. — Plastids, or Structm^al- 

 Units. — Cytods and Cells. — Four Different Kinds of Plastids ... 316 



CHAPTER Xiy. 



MIGEATION AND DISTRIBUTION OF ORGANISMS. CHOROLOGY 

 AND THE ICE-PERIOD OF THE EARTH. 



Chorological Facts and Causes. — Origin of most Species in one Single 

 Locality. — "Centres of Creation." — Distribution by Migration. — 

 Active and Passive Migrations of Animals and Plants. — Means of 

 Transport. — Transport of Germs by Water and by Wind. — Con- 

 tinual Change of the Area of Distribution by Elevations and 

 Depressions of the Groimd. — Chorological Importance of Geological 

 Processes. — Influence of the Change of Climate. — Ice or Glacial 

 Period. — Its Importance to Chorology. — Importance of Migrations 

 for the Origin of New Species. — Isolation of Colonists. — Wagner's 

 Law of Migration. — Connection between the Theory of Migration 

 and the Theory of Selection. — Agreement of its Results with the 

 Theoiy of Descent «•• ••• ..* ... 350 



