SUMMARY OF DERIVATIVES OF ORGAN-FORMING AREAS 533 



E. Summary of Later Derivatives of the Major Presumptive Organ- 

 forming Areas of the Late Blastula and Gastrula 



1. Neural Plate Area (Ectoderm) 

 This area gives origin to the following: 



(a) Neural tube, 



(b) optic nerves and retinae of eyes, 



(c) peripheral nerves and ganglia, 



(d) chromatophores and chromaffin tissue (i.e., various pigment cells of 

 the skin, peritoneal cavity, etc., chromaffin cells of supra-renal gland), 



(e) mesenchyme of the head, neuroglia, and 



(f) smooth muscles of iris. 



2. Epidermal Area (Ectoderm) 

 This area gives origin to: 



(a) Epidermal tube and derived structures, such as scales, hair, nails, 

 feathers, claws, etc., 



(b) lens of the eye, inner ear vesicles, olfactory sense area, general, cu- 

 taneous, sense organs of the peripheral area of the body, 



(c) stomodaeum and its derivatives, oral cavity, anterior lobe of pituitary, 

 enamel organs, and oral glands, and 



(d) proctodaeum from which arises the lining tissue of the anal canal. 



3. Entodermal Area 

 From this area the following arise: 



(a) Epithelial lining of the primitive gut tube or metenteron, including: 

 (1) epithelium of pharynx; epithelium pharyngeal pouches and their 

 derivatives, such as auditory tube, middle-ear cavity, parathyroids, and 

 thymus; (2) epithelium of thyroid gland; (3) epithelial lining tissue 

 of larynx, trachea, and lungs, and (4) epitheUum of gut tube and gut 

 glands, including liver and pancreas, 



(b) most of the lining tissue of the urinary bladder, vagina, urethra, and 

 associated glands, 



(c) Seessel's pocket or head gut, and 



(d) tail gut. 



4. NOTOCHORDAL ArEA 



This area: 



(a) Forms primitive antero-posterior skeletal axis of all chordate forms, 



(b) aids in induction of central nerve tube, 



