TABLE YI. 



Syshematic Survey of the principal organs of the ideal Primitive Yertebrate, 

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

 from, the germ. layers. 



Primary Germ- 

 layers. 



Secondary Germ- 

 layers. 



Most important Organs of 

 the Primitive Vertebrato. 



I. 



Skin-layer 



(Animal germ-layer, 



Baer). 

 Lamina dermalis, H. 



Exoderma. 



\ 



I. 



Skin-sensory layer 



(Skin-stratum, Baer), 



or 



SeriPory layer. 

 Lamina neurodermalis, H. 



n. 



Skin-fibrous layer 



(Flesh-stratum, Baer), 

 or 



Flesh-layer. 

 Lamina inodermalis, H. 



1. Outer skin {Epidermis^. A 

 simple cell-covering of the 

 outer surface. 



2. Spinal tube {Tubus medul- 

 laris') (with the organs of ' 

 sense : the nose, eyes, organs 

 of hearing). 



3. Primitive Kidneys {Protone- 

 phra) (a pair of simple ducts, 

 primitive kidney ducts). 



4. True skin (Corium') {Cutis and 

 suhcutis^. 



5. Muscles of the trunk (dorsal 

 and ventral muscles). 



6. Notochord {Cliorda dorsalis'). 



7. Exoccelar, or Parietal Coelom- 

 epithelium (the inner cell- 

 covering of the body-wall). 



\ 8. Male sexual glands {Testes^ 



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

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

 (colourless blood). 



n. 



Intestinal laver 



(Vegetative germ- 

 layer, Baer). 

 Lamina gastralis, H. 



Entoderma. 



IIT. 



Intestinal-fibrous layer 



(Vascular stratum, Baer), 

 or 



Vascular laver. 

 Lamina inogastralis, H. 



10. 



11. 



\ 



12. 

 13. 



TV. 



Intestinal-glandular layer 



(Mucous stratum, Baer), 

 or 



Mucous layer. 

 Lamina mycogastralis, H. 



14. 



15. 



Female sexual glands (Ovary'). 



Kndocojlar, 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). 



