DEVELOPMENT OF KIDNEYS AND FAT-BODIES IN THE FROG. 157 



Fig. 1. A 40 mm. tadpole dissected from the ventral surface to show 

 the condition of the head kidneys, "Wolffian bodies, 

 fat-bodies, and genital ridges. The dotted lines a a and 

 b b show the lines along which the sections in Figs. 8 and 

 9 are taken respectively : ( X 5). 



Fig. 2. Part of a transverse section through the Wolffian body of a 

 21 mm. tadpole, showing the whole length of one of the 

 nephrostomial tubules, with its openings into the ccelom 

 and into the renal vein : (x 120). 



Fig. 3. Part of a transverse section through the Wolffian body of a 

 40 mm. tadpole (cf. Figs. 1 and 9). The figure shows 

 the whole length of one of the nephrostomial tubules, 

 with its openings into the ccelom and into the renal 

 vein: (x 120). 



Fig. 4. Part of a transverse section through the kidney of a frog at 

 the commencement of the second year (cf. Fig. 7). The 

 figure shows the whole length of one of the nephro- 

 stomial tubules, with its openings into the ccelom and into 

 the renal vein : (x 120). 



Fig. 5. A tailed frog during the metamorphosis ; dissected from 

 the ventral surface to show the condition of the head 

 kidneys, Wolffian bodies, fat-bodies, and genital ridges : 

 (x 5). 



Fig. 6. The dorsal half of a transverse section through a 23 mm. 

 tadpole at the level of the fore limbs and the second 

 spinal nerve. The figure shows the head kidney with 

 the tubules enlarged and degenerating ; also the boxing 

 in of the glomerulus on each side by fusion of the lung 

 with the head kidney : (x 22). 



Fig. 7. A transverse section through the kidney of an adult male frog. 

 The figure has been constructed from four consecutive 

 sections. The dorsal surface is turned upwards in the 

 figure, and the ventral surface downwards ; the inner 

 border of the kidney is to the left, the outer border to 

 the right side of the figure. Three nephrostomial tubules 

 are shown ; in all three cases the peritoneal openings of 

 these tubules are drawn, and in the middle one of the three 

 the opening into the renal vein is shown as well : (X 45). 



