Hau.. — Mesonephros in Amphibia. 



PLATE 3. 



All figures, except 30, 34, and 35, are of cross-sections, and all are of Amhlystoma 

 unless otherwise indicated. 



Fig. 24. Through somite 18 of the right side of a young adult about 60 mm. long. 



X 75. 

 Fig. 25. Through a primary and a secondary mesonephric unit from the left side 



of a larva 25 mm. long. X 188. 

 Fig. 26. Through a primary and secondary mesonephric blastula from the 



eigliteenth somite of the right side of a larva 24 mm. long. X 350. 

 Fig. 27. Section of a primary, a secondary, and a tertiary unit from somite 18 of 



the right side of a larva 25 mm. long. X 195. 

 Fig. 28. Rana. Section of a mesonephric unit from the right side of the body. 



The same unit is reconstructed in Figure 30, a dotted hne in this figure 



indicating the level of the section shown in Figure 28. X 410. 

 Fig. 29. Rcnui. A section showing a tertiary blastula still connected with the 



Malpighian body of a secondary unit, from the right side of the body. 



X 410. 

 Fig. 30. Rana. A dorso-median view of a wax reconstruction of four mesonephric 



units and the Wolffian duct of the right side of the body. For a draw- 

 ing of a cross-section of the most posterior of the four units, see 



Figure 28. 

 Fig. 31. Larva I. A cross-section through the first pronephric nephrostome of 



the left side of a larva 23 mm. long. X 36. 

 Fig. 32. Larva II. Section passing immediately posterior to the first pronephric 



nephrostome of tlie right side of a larva 25 mm. long. X 48. 

 Fig. 33. The third section behind that shown in Figure 32. X 48. 

 Figs. 34, 35. Two drawings of a wax reconstruction of a mesonephric tubule of 



left side of the body of a larva 16 mm. long. Figure 34 is the anterior 



aspect ; Figure 35, the ventro-median. X 120. 

 Fig. 36. Larva III. Tlirough the first pronephric nephrostome of the right side of 



a larva 21.5 mm. long, showing the fundament of the anterior Miillerian 



evagination. X 147. Note. — By oversight of the lithographer the 



nuclei of the tubules are left unshaded. 

 Fig. 37. Through the second nephrostome of the left side of the larva shown in 



Figure 31. X 16. 



