Field. — ProuepLirOj iu Amphibia. 



PLATE I. 



A portion of a cross section tiirough the anterior trunk region of one 



of the older embryos included under Stage I. X 110. 

 A cross section through the same embryo in the middle trunk region. 



X25. 

 A portion of a cross section through the middle trunk region of one 



of the younger embryos in Stage I. X 92. 

 A portion of a cross section through the hinder trunk region of one of 



the younger embryos belonging to Stage 11. X 92. 

 A portion of a cross section through the anterior trunk region of one of 



the older embryos from Stage II. The section passes through an 



interprotovertebral septum. X 110. 



6. A portion of a cross section from one of the older embryos in Stage III. 



The plane of the section passes through the middle of ^Somite III. 

 X 110. 



7. A small segment^of a cross section througli the embryo shown in Figures 



15-17 of Plate II. The Figure represents a portion of the ventro- 

 lateral ectoderm with three subjacent mesodermal cells. X 615. 



8. A portion of a cross section through the embryo shown in Figures 18-22, 



Plate III. It shows the fundament of the glomus. X 110. 



9. A portion of a cross section through a slightly older embryo, showing 



the glomus in a more advanced stage of development. X 110. 

 10. A portion of a cross section tiirough an embryo of Stage V., showing 

 a branch of the aorta which gives off a small vessel to the glomus. 

 X 150. 



