176 On the Double Type of the Respiratory Organs. 



c. Part analogous to the operculum of. fishes, which, by its pos- 

 terior extremity, covers the first opening of the neck : the two 

 other openings are more behind. 



d. The aorta. 



e. The ventricle of the heart. 



f, The auricles. 



g, The first vestiges of a liver. 

 k. The first trace of a wing. 



Fiff. 2. Embryo of the fifth day, magnified one time, and repre- 

 sented in its natural position. 



Fig. 8. Id. aaa a, b, c, d, e,f, g, h, as in fig. 7« 



i, A part of the amnios. 



k, A part of the sac of the yelk. 



I, The pelvic extremity. 



m, The tail. 



Fig. 3. Embryo of a pig of three weeks, magnified one time. 



Fig. 9. Id. aaa, the branchial openings. 



b. The heart. 



c. The liver. 



d. The supra-renal capsule. 



e. The extremity of the common integuments of the abdomen, 

 in which is found the anus. ^ 



Fig. 11. Id. The anterior part slightly magnified, and seen from 

 the inferior aspect. 

 a. The nostril. 

 6, Lower jaw. 

 cccc, Branchial openings. 



d. Ventricle of the heart. 



e, Auricle. 

 f, Aorta. 



f. Vena cava, 

 'ig. 4. Embryo of a horse, magnified half a diameter. 

 Fig. 10. Id. a, The heart. 

 6, The left lung. 



c, The liver ; there is seen on the fore part of the liver a parj 

 of the diaphragm. 



d, The left supra-renal capsule. 



e, The penis. 



f, A part of the integuments of the abdomen. 



f, Section of the symphysis pubis, 

 ig. 5. Anterior part of the body of a very young embryo of the 

 Blennius viviparus, intended to show the resemblance existing be- 

 tween the gills of these foetuses, and the branchial openings of the 

 embryos of birds and mammalia. 



Fig. 6. Embryo of the lacerta viridis, viewed from the right 

 side, and magnified four times, The intestinal canal, and the sac 

 of the yelk, which hang mostly out of the belly, have been remov- 

 ed. The heart is wtuated below the neck, which presents on each 

 side three branchial openings ; the vesicle at the posterior extre- 

 mity of the embryo is the allantois. 



