▼1 OONTENTB. 



CHAPTER XVL 



THK ANCESTEY OF MAN. 

 L Fbom thb Moneba to thb Gastbaa. 



FAOl 



Relation of the General Inductive Law of the Theory of Descent to 

 the Special Deductive Laws of the Hypotheses of Descent. — Incom- 

 pleteness of the Three Great Eecords of Creation : Palaeontology, 

 Ontogeny, and Comparative Anatomy. — Unequal Certainty of the 

 Various Special Hypotheses of Descent. — The Ancestral Line of 

 Men in Twenty-two Stages : Eight Invertebrate and Fourteen Verte- 

 brate Ancettors. — Distribution of these Twenty-tw© Parent-forms 

 in the Five Main Divisions of the Organic History of the Earth. — 

 First Ancestral Stage : Monera. — The Structureless and Homo« 

 geneons Plasson of the Monera. — Differentiation of the Flasson 

 into Nucleus, and the Protoplasm of the Cells. — Cytods and Cells 

 as Two Different Plastid-forms. — Vital Phenomena of Monera. — 

 Organisms without Organs. — Second Ancestral Stage : Amoebse. 

 — One-celled Primitive Animals of the Simplest and most Un- 

 differentiated Nature. — The Amoeboid Egg-cells. — The Egg is Older 

 than the Hen. — Third Ancestral Stage : Syn-Amoeba, Ontogeneti- 

 cally reproduced in the Morula. — A Community of Homogeneous 

 Amoeboid Cells. — Fourth Ancestral Stage : Planaea, Ontogeneti cally 

 reproduced in the Blastula or Planula. — Fifth Ancestral Stage : 

 Gastraea, Ontogenetically reproduced in the Gastrula and the Two- 

 layered Germ-disc. — Origin of the Gastraea by Inversion (^invagi- 

 natio) of the Planssa. — Haliphysema and Gastrophysema. — Extant 

 Gastrssada ... ... ... ... .^ ... 94 



CHAPTER XVIL 



THE ANCESTRAL SERIES OF MAN. 



n. Fbom the Pbimitiye Wobm to the Skulled Animal. 



The Four Higher Animal Tribes are descended from the Worm Tribe. 

 — The Descendants of the Gastraea; in one direction the Parent 

 Form of Plant- Animals (Sponges and Sea-Nettles), in the other 

 the Parent Form of Worms. — Radiate form of the former, Bilateral 

 form of the latter. — The Two Main Divisions of the Worms, 

 Acoelomi and Coelomati : the former without, the latter with, a 

 Body Cavity and Blood-vessel System. — Sixth Ancestral Stage : 

 Arohelmiuthea, most nearly allied to Tnrbellaria. — Descent of the 



