CONTENTS. 



PAGI 



Layer and the Skin-fibrous Layer.— The Entoderm or Intestinal 

 Layer gives rise to the Intestinal-fibrous Layer and the Intestinal- 

 glandular Layer , , 181 



CHAPTER IX j 



THE VERTEBRATE NATURE OF MAN. | 



! 

 Relation of Comparative Anatomy to Classification. — The Family -rela- ' 



tionship of the Types of the Animal Kirgdcm. — Different Signi- 

 ficance and Unequal Value of the Seven Animal Types.— The 

 Gastraa Theory, and the Phylogenetic Classification of the Animal 

 Kingdom. — Descent of the Gastraea from the Protozoa. — Descent 

 of Plant-animals and Worms from the Gastraea. — Descent of i 



the Four Higher Classes of Animals from Worms. — The Verte- 

 brate Nature of Man. — Essential and Unessential Parts of the 

 Vertebral Organism. — The Amphioxus, or Lancelet, and the Ideal j 



Primitive Vertebrate in Longitudinal and Transverse Sections. — I 



The Notochord.— The Dorsal Half and the Ventral Half.— The ' 



Spinal Canal. — The Fleshy Covering of the Body. — The Leather- 

 skin (corium). — The Outer-skin (epidermis) . — Body-cavity {cceloma), ] 



— The Intestinal Tube. — The Gill-openings. — The Lymph-vessels. ] 



— The Blood-vessels. — The Primitive Kidneys and Organs of Se- ; 



production. — The Products of the Four Secondary Germ-layers ... 24'! i 



I 



CHAPTER X.  



i 



THE CONSTRUCTION OF THE BODY FROM THE GERM- • 



LAYERS. j 



I 

 The Original (Paliugenetic) Development of the Vertebrate Body from J 



the Gastrula. — Relatioa of this Process to the Later (Kenogenetic) 



Germination, as it occurs in Mammals. — The most important act in ] 



the Formation of the Vertebrate. — The Primary Germ-layers, and ! 



also the Secondary Germ-layers, which arise by Fission of the Prima- [ 



ries, originally foi'm Closed Tabes. — Contemporaneously with the ] 



Completion of the Yelk-sac, the Germ-layers flatten, and only later i 



again assume a Tabular Form. — Origin of the Disc-shaped Mamma- 



lian Germ-area. — Light Germ-area (area pellucida) and Dark Germ- , 



area {area ojjaca). — The Oval Germ-shield, which afterwards 



assumes the Shape of the Sole of a Shoe, appears in the Centre of 



the Light Germ-area (a, pellucida). — The Primitive Streak , 



s 



