TABLE yi. 



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

 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 



^^Sldn-stratiim, Baer), 



or 



Sen F cry layer. 



Lamina neurodermalis, H. 



n. 



Skin-fibrous layer 



(Flesh-stratum, Baer), 



or 



Flesh-layer. 

 Lamina inodermalis, U. 



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 (Protnne- 



phra) (a pair of simple ducts, 

 primitive kidney ducts). 



4. True skin (Corium) {Cutis and 



subcutis). 



5. Muscles of the trunk (dorsal 



and ventral muscles). 



6. Notochord (Chorda dorsalis'). 



7. E.xocoelar, or Parietal Co-lora- 



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

 (colourless blood). 



n. 



Intestinal laver 



(Vegetative germ- 

 layer, Baer). 

 Tximina gastralis, H. 



Entoderma. 



III. 

 Intestinal-fibrous layer 



(Vascular stratum, Baer), 

 or 



Vascular laver. 

 Lamina inogastralis, B. 



IV. 



Intestinal-glandular layer 



(Mucous stratum, Baer), 



or 



Mucous layer. 

 Lam:na mycogaslralis, H. 



9. Female sexual glands (Ovary). 



10. Kndoccelar, or Visceral Coe- 



lom-epithelium (the outer 

 cell-covering of the intestinal 

 tube.) 



11. Princip.il blood-vessels (primi- 



tive artery or dorsal vessel, 

 and the primitive vein or 

 ventral vessel). 



12. Mesentery. 



13. Muscular intestine wall (fi- 



brous intestinal wall). 



14. Intestinal epithelium (innel 



cell-covering of the intestinar 

 tute). 



15. Intestinal glandul.ir epithe- 



lium (liver-cells and other 

 intestinal glandular celLs). 



