Observations on the development of the excretory system in Turtles. 713 



Fig. 50. Section 18 of somite 9. Tubules on each side almost 

 closed by the distended lacunae of the glomera. 



Fig. 51. Section 9 (left) and section 8 (right) of somite 10. 

 On the right is the last tubule opening into the coelom (o. t) 

 and on the left is the first tubule completely shut off from 

 the coelom (c.t). This contains the cell tuft which forms the 

 glomerulus (gli). 

 Figs. 52 — 56. From cross sections of Platypeltis embryo XII (3). 



Fig. 52. Section 4 of somite 6, shows on the left the most 

 anterior element remaining of the pronephros (c. d), which is 

 non cut off from the coelom and imbedded in the sclerotome 

 near the aorta. 



Fig. 53. Section 23 of somite 6. Anterior end of the coelom 

 with glomera and on the left a pronephric tubule. 



Fig. 54. Section 1 of somite 7 shows a further development of 

 the cells of the tubule in which densely staining granules are 

 often found. The glomera project freely into the body cavity. 

 Thej" have now acquired more or les cellular tissue but are 

 still little more than a meshwork in which many blood cor- 

 puscles are caught. This is not shown by the even yellow 

 tinting. 



Fig. 55. Section 8 of somite 10. Last freely open tubules. 

 The cilia {cil) are conspicuous. 



Fig. 56. Section 16 of somite 10. On the left an incompletely 

 closed tubule with glomus. On the right is the first closed 

 tubule with distended end from which the glomerulus has been 

 lost in handling. 



Plate 48. 



Figs. 57 — 60. Cross sections of Platypeltis embryo XI (1). 



Fig. 57. Anterior end of metanephric blastema {met. bV), Wolffian 



duct {w.d) and mesonephric blastema {mes. hi). 

 Fig. 58. Several sections posterior to Fig. 57. The ureter is 

 seen at the lower outside edge of the metanephric blastema. 

 Fig. 59. Two sections behind Fig. 58. Near the point where 



the ureter branches from the duct. 

 Fig. 60. Seven sections behind Fig. 59. Branching of ureter 

 from the dorsal side of the Wolffian duct at the point where 

 the duct opens into the cloaca. 

 Figs. 61 and 62. From cross sections of Platypeltis XIV (1). 

 Fig. 61. Anterior end of metanephric blastema {met. hi).. Wolf- 

 fian duct {w. d), mesonephric blastema {mes. hl) and rudiments 

 of two mesonephric tubules. 

 Fig. 62. Ureter {ur) and metanephric blastema {met. hi), Wolf- 

 fian duct {w.d) and mesonephric blastema {mes. hi). 

 Figs. 63—68. Cross sections of P^«^z/;9e?^iS embryo XII (4). Earliest 

 stage of the branching of the ureter from the Wolffian duct. 



