FiBLD. — Prouephros iu Aiuphibia. 



PLATE IV. 



Fig. 28. Part of a cross section through the anterior trunk region of a larva 

 belonging to Stage VI. Tiie Figure shows the pronephros in the 

 region of the first nephrostouie. X 110. 



Fig. 29. Part of an oblique longitudinal section through a larva of Stage IV. The 

 plane of the section was directed so as to cut the somatopleure tan- 

 gentially along the line of the three nephrostoines. Its direction is 

 represented by the line 40 in Figure 20. X 110. 



Fig. 30. Part of a cross section tiirough the middle trunk region of a larva, 

 from which Figure 28 was also drawn. (Stage VI.) X 110. 



Fig. 31-38. A series of diagrams illustrating the convolution of the pronephric 

 tubules. These diagrams, which are based upon reconstructions 

 from cross sections, merely serve to show the number and approxi- 

 mate location of tlie loops in a longitudinal direction. No attempt 

 has been made to indicate in the diagrams the changes in position 

 undergone by the tubules in a transverse direction. The gray tint 

 represents the common trunk and the anterior portion of the seg- 

 mental duct. The first neplirostomal tubule and the collecting 

 trunk are colored pink. The second and third tubules are repre- 

 sented in yellow and orange respectively. 



Figs. 31-34 are from various larvae of Stage V. 



Fig. 32 is a diagram of tiie reconstruction shown in Figure 40. 



Figs 33 and 34 represent the right and the left pronephros respectively of the same 

 individual. 



Figs. 35-37 .are from various larvaj of Stage VI. 



Fig. 36 is a diagram of the reconstruction shown in Figure 41. 



Fig. 38 is from a larva of Rana halesina. 



Figs. 39-41. A series of reconstructions from cross sections of larva; in different 

 stages of development. In Figures 40 and 41, the common trunk 

 and the anterior portion of tlie segmental duct have been shaded 

 without color ; the collecting trunk and the first nephrostomal 

 tubule have been colored pink ; and the second and third nephro- 

 stomal tubules are respectively yellow and orange. X 65. 



Fig. 39. Eight pronephric pouch of a larva belonging to Stage IV., viewed from 

 the median side. The X's represent the position of the nephro- 

 stomes. The lines 18-21 show the various levels at which the sec- 

 tions represented in Figures 18-21 were made. 



Fig. 40. Eight pronephros of a larva belonging to Stage V., viewed from the 

 median side. 



Fig. 41. Right pronephros of a larva belonging to Stage VI,, viewed from the 

 ventral side, the e-xternal face being uppermost. 



