Hall. — Mesonephros in Amphibia. 



PLATE 4. 



All figures are from cross-sections of Amll //stoma. 



Fig. 38. Larva IV. Through the second uephrostome of tlie left side of a larva 

 44 mm. long. X 118. 



Fig. 39. The fourth section posterior to that shown in Figure 38. It passes 

 through the neplirostonial cavity. X 118. 



Fig. 40. Larva V. Through the second nephrostome and the second Miillerian 

 evagination of the right side of a larva 41 mm. long. X 100. 



Fig. 41. Through the nephrostomal cavity and the fundament of the first ^liil- 

 lerian evagination of the left side of tiie larva represented in Figure 40. 

 X 118. 



Fig. 42. Larva VI. Through the anterior evagination of the right side of a larva 

 40 ram. long. X 200. 



Fig. 43. Third section posterior to that of Figure 42. X 200. 



Fig. 44. Larva VI 6. Tiirough the second nephrostome and the second (posterior) 

 evagination of the left side of a larva 42 mm. long. X 200. 



Fig. 45. Larva XII. Through the degenerate pronephroi of a larva 55 mm. long, 

 in which the gill-slits have closed. It shows, on each side, the glome- 

 rular cavity and the epithelial band some distance anterior to the 

 ostium. X 88. 



Fig. 46. A section posterior to that of Figure 45, showing the opening of the right 

 glomerular cavity into the coelome. X 118. 



Fig. 47. Through the ostium of the left side of the larva shown in Figures 45 and 

 40. X 118. 



Fig. 48. Larva VII. Through the right pronephros of a larva 35 mm. long, 

 showing the precoelomic duct. X 200. 



Fig. 49. Larva XL Through the first Miillerian evagination (retained to a very 

 late stage) of the left side of a larva 49 mm. long. X 156. 



Fig. 50. Larva IX. Section showing the process of fusion of " duct 1 " and 

 " duct 2" of the left side of a larva 50 mm. long. X 335. 



Fig. 51. A section anterior to that of Figure 50, passing through the second Miil- 

 lerian evagination of the left side. X 156. 



Fig. 52. Through the opposite side of the same larva as that represented by 

 Figure 49, showing a remnant of " duct 1 " and the epithelial band. 

 X 130. 



Fig. 53. The sixth section behind that drawn in Figure 44, showing the dwin- 

 dling end of " duct 2 " and the oviducal welt. X 250. 



