Field. — Pronephros in Amphibia. 



PLATE VII. 



Fig. 53. A portion of a cross section through the posterior trunk region of a larva 

 of Amblystoma belonging to Sta«e VI. The section shows the fun- 

 dament of the second primary mesonephric tubule (<ii. sp.). X 90. 



Fig. 54. A portion of a cross section through the middle trunk region of a larva 

 of Amblystoma belonging to Stage VI. The section shows one of 

 the "cords of cells" which occur between the mesonephros and the 

 pronephros ; it exhibits a case of nuclear mitosis in the peritoneum, 

 which suggests the origin of these cells. X 500. Zeiss apochr. 

 4 mm. Oc. 8. 



Fig. 55. A portion of a cross section through the anterior trunk region of an 

 embryo of Amblystoma belonj,'in<,' to Stage III. The pronephric 

 thickening is shown in the region of the middle of Somite II. 

 X 00. 



Fig. 56. A portion of a cross section from the same series. The pronephric 

 thickening is shown in the region of the posterior face of Somite II. 

 X 90. 



