ifi the Foetus of Vertebrated Animals. 32 5 



9. (From Baer) Longitudinal and transverse sections of the embryo 

 and germinal membrane. 



10. Appearance of the embryo at the 26th hour. 



11. Ssctions of the same. 



12. Embryo of the Chick, when the heart begins to appear, about the 



30th hour. A (From Prevost and Dumas.) B (From Pander.) 



13. (From Baer) Sections of the germinal membrane, about the 35Lh 



hour. The intestinal folds below the head and tail, and the com- 

 mencing amnios, are seen. 



14. (From Prevost and Dumas) The foetus and heart from above, at the 



36th hour. 



15. Foetus of the Turkey at a period corresponding to the 40th hour in 



the chick, seen on the abdominal side. 



16. The vascular area about the COth hour. 



1 7. The foetus of the Goose after five days and a half incubation. 



The remaining figures represent the appearance of the heart at the dilFe. 

 rent hours, indicated by the numbers attached to them, viz. at the 27th, 30th, 

 35th, 40th, 45th, 55th, 65th, 75l.h, 85th and 95th hours. 



Fig. 18. The commencing fold of the septum of the auricles, seen from be- 

 hind. 



19. The heart of the Goose of five days and a-half, when the septum of 



the ventricle commences. A, The anterior side. B, The poste- 

 rior. A section being made through the ventricles at the upper 

 part, C represents the basilar part, D the part towards the apex. 



20. Heart of the goose on the 6th day, when the right ventricle and 



septum are increased in size. A, Anterior view. C, The ante- 

 rior part of the ventricles removed. A hair is passed behind the 

 septum from one ventricle to the other. 

 2L Heart of the goose more advanced. In B, the upper part of the 

 auricles is removed, so as to shew the septum between them. A 

 probe is passed through the opening of the vena cava inferior, and 

 the projecting fold corresponding to the tubercle of Lower, and 

 the eustachian valve, is seen before it. E, The side view of the 

 same heart. 



22. The heart of the chick, when nearly completely formed, after six 



days and a half incubation. The fore parts of the auricles are 

 drawn aside, so as to shew the aorta, innominatoe, pulmonary ar. 

 teries and ductus arteriosi. 



23. The folds forming the auriculo-ventricular valves, before the septa 



are complete. 



2. Fishes. 

 Fig. 1. (From Prevost) The primitive trace of the foetus of the Mulus gobio 

 in the cicatricula. 



2. (From Rathke) Section of the ovum of the Blennius, shewing the 



embryo and the layers of the germinal membrane. 



3. The heart of the same animal, when divided into an auricle andven. 



tricle. 



