Xll CONTENTS. 



CHAPTER III. 



THE CHANGES WHICH TAKE PLACE DURING THE FIRST DAY OF INCUBATION, 



PP- 4357- 



I. Variations in the progress of development. 2. The embryonic shield. 

 3. The formation of the epiblast, mesoblast and hypoblast. 4. The primitive 

 streak, the primitive groove. 5. The head-fold, the medullary groove, me- 

 dullary folds, and notochord. 6. The amnion ; the changes taking place in the 

 three layers. 7. The increase of the head-fold. 8. The closure of the me- 

 dullary canal. 9, 10. The cleavage of the mesoblast : formation of splanchno- 

 pleure and somatopleure. ir. The protovertebrse. 12. The formation of the 

 vascular area. 13. Recapitulation. 



CHAPTER IV. 



THE CHANGES WHICH TAKE PLACE DURING THE SECOND DAY, pp. 58 83. 



I. Increasing distinctness and prominence of the embryo. 2. The first cere- 

 bral vesicle. 3. The increase in the number of proto vertebrae. 4. The first 

 rudiments of the alimentary canal. 5. The formation of the heart. 6. The 

 formation of blood-vessels ; the omphalo-mesaraic veins and arteries, the sinus 

 terminalis. 7. Changes taking place in the cells of the several layers. 

 8. The rudiment of the Wolffian duct. 9. Recapitulation of the changes 

 during the first half of the second day. 10. Increasing prominence of the 

 embryo ; the tail-fold and the lateral folds. 1 1. Continued closure of the 

 medullary canal. 12. The optic vesicles. 13. The second and third cerebral 

 vesicles. 14. Change of position of the optic vesicles. 15. The vesicles of the 

 cerebral hemispheres. 16. The cranial flexure. 17. The rudiment of the ear, or 

 auditory sac. 18. Changes in the heart. 19. The primitive aortse and first 

 pair of aortic arches, the omphalo-mesaraic vessels, the sinus terminalis. 

 20. The second and third pair of aortic arches. 11. The Wolffian duct. 

 22. The amnion. 23. Recapitulation. 



CHAPTER V. 



THE CHANGES WHICH TAKE PLACE DURING THE THIRD DAY, pp. 84 140. 



I. The diminution of the albumen. 2. The spreading of the opaque and 

 vascular areas. 3. The vascular area. 4. The continued folding in of the 

 embryo. 5. The increase of the amnion. 6. The change in the position of 

 the embryo. 7. The curvature of the body. 8. The cranial flexure. 

 9* Growth of the vesicles of the cerebral hemispheres; the third ventricle, 

 pineal gland, infundibulum and pituitary body, the cerebellum and medulla 

 oblongata. 10. Changes in the spinal cord. n. The formation of the eye. 

 Histological changes in the retina, optic nerve, and lens. 12. The formation 

 of the ear. 13. The nasal pits* 14. The visceral clefts and folds. 15. The 

 aortic arches. 16. Changes in the heart; the Ductus Cuvieri and cardinal 

 veins. 17. The folding in of the alimentary canal; the formation of the tail. 

 1 8. The lungs. 19. The liver. 20. The pancreas and spleen. 21. The 

 thyroid body. 22. Changes in the trunk of the embryo. 23. Separation of 

 the muscle-plates from the protovertebrse. 24. Growth of the intermediate 

 cell-mass. 25. The cranial nerves. 26. The Wolffian duct. 27. Recapi- 

 tulation. 



