NOTES ON THE DEVELOPMENT OP THE NEWT. 255 



V sup. max. Superior maxillary branch of 5th nerve. V inf. max. Inferior 

 maxillary branch of 5th nerve. VII post-br. Post-branchial branch of 7th 

 nerve. IX post-br. Post-branchial branch of 9th nerve. VII pree-br. Prse- 

 brancbial branch of 7th nerve. IXpra-br. Prse-branchial branch of 9th 

 nerve, x. Fusion of 7th nerve with epiblast of gill-cleft. 



Figs. 1 — 7. — Series of transverse sections through an embryo, to show 

 the relations of the post-anal gut to the hind-gut ; Fig. 1 being the most 

 anterior, and Fig. 7 the most posterior. 



Fig. 1. A little in front of the blastopore, to show the origin of the 



post-anal gut from the hind-gut. 

 Fig. 2. Showing the post-anal gut completely separated from the hind- 

 gut. 

 Fig. 3. Through the blastopore. 

 Fig. 4. Behind the blastopore. 

 Fig. 5. Showing dilatation of the solid post-anal gut near the hind end 



of tiie tail. 

 Fig. 6. Showing fusion of the post-anal gut with the notochord and the 



neural canal. 

 Fig. 7. Showing fusion of the mesoblast with the other layers near the 

 extreme end of the tail. 

 Figs. 8 — 11 are taken from one series of transverse sections through the 

 anterior end of an embryo, to show the origin of the stomodseum, the pitui- 

 tary body, and thyroid body. Fig. 8 being the most anterior, and Fig. 11 the 

 most posterior. 



Fig. 8. Showing the origin of the stomodseum and pituitary body, and 



the fusion of the former with the anterior wall of the fore-gut. It 



also shows the root of the facio-auditory nerve, and its ventral fusion 



with the epiblast. 



Fig. 9. Showing the hind end of the stomodseum. 



Fig. 10. Showing the anterior end of the thyroid body as a solid rod of 



cells attached to the ventral wall of the fore-gut. 

 Fig. 11. Showing the thyroid body near its posterior end. 

 Fig. 12. — Longitudinal vertical section through the head end of an embryo, 

 to show the origin of the stomodseum and pituitaiy body as a solid ingrowth 

 of epiblast in front of the fore-gut. 



Fig. 13. — Transverse section through the trunk of an embryo shortly after 

 the closure of the medullary canal, to show the neural ridge. 



Fig 14. — Longitudinal vertical section through the head end of a somewhat 

 older embryo than that from which Fig. 12 was taken, to show the relations 

 of the stomodseum and the pituitary body to the fore-gut, infundibulum, and 

 notochord. 



Fig. 15. — Transverse section through the trunkof an embryo shortly before the 

 closure of the medullary canal, showing the epiblast continuous dorsally with it. 



