TABLE VI. 



Systematic Survey of the principal organs of tlie ideal Primitive Vertebrate, 

 the hypothetical parent-form of Vertebrates, and of their development 

 from the genn-layers. 



Primary Germ- 

 layers. 



Secondary Germ- 

 layers. 



Most important Organs of 

 the Primitive Veitebrato. 



L 



Skin-layer 

 (Animal germ-layer, 



Baer). 

 Lamina dermalis, E. 



Exoderma. 



\ 



I. 



Skin -sensory layer 



(^Skin-stratum, Baer), 



or 



Sen?ory layer. 

 Lamina neui-odermalis, 3, 



n. 



Skin-fibrous layer 



(Flesh-stratum, Baer), 

 or 



Flesh-layer. 

 Lamina inodermalis, H. 



3. 



Outer Bliin (Epidermis^. A 

 simple cell-covering of the 

 outer surface. 



Spinal tube {Tubus medul- 

 laris') (with the organs of 

 sense : the nose, eyes, organs 

 of hearing). 



Primitive Kidneys (^Protone- 

 phra) (& pair of simple ducts, 

 primitive kidney ducts). 



4. True skin (Coriurn) (^Cutis and 



subcutis). 



5. Muscles of the trunk (dorsal 



and ventral muscles). 



6. Notochord (^Chorda dorsalis). 

 1. Exocoelar, or Parietal Ccelora- 



epithelium (the inner cell- 

 covering of the bodj'-wall). 

 8. Male sexual glands (^Testes'), 



Coeloma, or Body-cavity. A space between the body-wall and the 

 intestinal wall, between the exoderm and the entoderm, filled with lymph 

 (colourless blood). 



IL 



Intestinal laver 

 (Vegetative germ- 

 layer, Baer). 

 Lariina gxstralis, H. 



Ilntoderma. 



in. 



Intestinal-fibrous layer 



(Vascular stratum, Baer), 



or 



Vascular laver. 

 lAimina inogastralis, E. 



IV. 



Int-^stinal-glandular layer 



(Mucous stratum, Baer), 



or 



Mucous layer. 

 Lam Ina mycogasLralis, B. 



1 



Female sexual glands (Orary). 



Endoccelar, or Visceral Coe- 

 lom-epithelium (the outer 

 cell-covering of the intestinal 

 tube.) 



Principal blood-vessels (primi- 

 tive artery or dorsal vessel, 

 and the primitive vein or 

 ventral vessel). 



Mesentery. 



Muscular intestine wall (fi- 

 brous intestinal wall). 



Intestinal epithelium (innel 

 cell-covering of the intestinar 

 tube). 



Intestinal glandular epithe- 

 lium (liver-cells and other 

 intestinal glandular cells). 



