110 Dr Allen Thomson on the Vascular Si/stem 



«, Inferior maxilla. >j, The amnios, g, The chorion. x:-> The ductus 

 ■vitello intestinalis. 



Fishes. 



Fig. 1. (From Rathke) Supposed section of the foetus of the Blennius Vivi- 

 parus, at the middle of fcetal life. 



2. (From do.) The anterior part of the body of a very young embryo of 



the same fish magnified seven times, the sac of the yolk and inte- 

 guments covering it removed. 



3. (From do.) The same seen from below ; the heart removed ; the ab- 



domen opened to shew the intestinal tube. 



4. (From do.) Another embryo farther advanced. The operculum 



covering the first and second branchial plates. 



5. f From do!) The same seen from below. 



6. (From Monro) The foetus of the skate with the yolk sac, half the 



size of the original. A, Anterior part of the body of the natural 

 size, shewing the external gills suspended from the branchial aper- 

 tures on the lower side of the body. 



7. Anterior part of the foetus of the Squalus Max. ; half the natural size, 



seen from above, shewing the external gills. A, The extremity 

 of cue of the gill filaments magnified. 



Reptiles. 



1. Bairachia. 



8. Foetus of the Aquatic Salamander one day after its exit from the 



egg, seen from below. A, Natural size. 



9. (From Rusconi) Head, &c of the larva of the same animal at the 



time when the gills are nearly perfected, opened, and seen from 

 above. M agnified. 



10. (From the same) Shews the leaflets of the gills forming. 



11. (From do.) The vessels in the neck of the adult Salamander. 



12. (From Cams) The adult Salamander opened, to shew the urinary 



bladder or allantois, with the umbilical vein going from it to the 

 liver. 



13. The larva of the firog about 24 days old ; shews the connexion of 



the external with the internal gills, and the left lungs beginning 

 to be formed. A, The natural size. 



14. The larva of the frog at the time of the commencement of its trans- 



formation, twice the natural size. A, Exhibits the double row of 

 leaflets on the internal gilL 



15. (From Swammerdam) The principal arteries of the adult frog. 



16. The commencing lungs of the frog; A, in the tadpole on the 18th 



day, seen from below ; B, in the tadpole represented in Fig. 13. 

 seen from the side. 



2. Lizards, ^c. 



17. (From Emmert and Hochstetter) Ovum of the Lacerta agilis, shew- 



ing the foetus in its amnios, the yolk and allantois with their ves- 

 sels. 



18. (From Dutrochet) Supposed section of the ovum of the Serpent, 



shewing the allantois expanding. 



19. (From Bojanus) The heart and arterial vessels of the Testudo Eu- 



ropaea from behind. 



Birds. 



20. Anterior part of the foetus of the Duck four days and a-half old, seen 



on the right side. Magnified about seven diameters. 



