38 T. H. BURLKND, 



XI 



2,7 — 2,10 Nephrostome opening into coelom ; veiy short (in- 

 complete?) tubule. 

 2,13—2,19 At 2,14—2,16 a nephrotome opening of a tubule 

 which opens into the duct at 2,18. 

 XII? 2,22—2,27. Tubule opening into duct and nephrotome. 

 The tubules behind this are undoubtedlj' mesonephric. 



Right side. 



I Glomus begins 1,61. 



I Trace of pronephric duct and tubules at 1,59, 1,61 and 1,62. 

 YII 1,63—1,67 Nephrostome of a tubule at 1,67. 



j 1,72 — 1,79 Tubule with opening into duct at 1,74 ; nephro- 

 ^^^^ ( stome at 1,77 and 1,78. 



^[1,81 — 1,86 Tubule with opening into duct at 1,84 and 1,85; 

 I nephrostome at 1,84 and 1,85. 



I 1,90—1,99 Tubule with opening to coelom at 1,94 and 1,95, 

 I and into duct at 1,96. 



(2,3 — 2,10 Tubule having a nearly shut off nephrostome at 

 ^^ I 2,3 and 2,4 ; joins with the duct at 2,9. 



[ 2,12 — 2,18 Nephrostome opening into lower end of open 

 XII J nephrotome at 2,13 and 2,14. The tubule does 



I not reach the duct. 



Undoubtedly mesonephric tubules at 2,22, 2,32, 2,38 and 2,43. 

 The arrangement of the tubules with respect to the body- 

 segments is only provisional. If it is the true one, it would help 

 to confirm the view that in the region of segments X, XI and XII 

 the wide lower end of the nephrotome has at first no connection 

 with the general coelom, but that a connection is gained later, and 

 that this change is followed — after a much longer interval of 

 time — by a closing off of these nephrotomes from the coelom 

 at least in XI? and XII. 



Comparison of the kidney in embryos I, J, K, L, M, N. 

 These embryos range over a period extending from the time when 

 the developing Ghrysemys has 18 protovertebrae, up to the time when 

 segmentation has practically reached the posterior end of the body. 

 The development of the pronephric duct can be followed in these 

 embryos: the duct on each side growing further and fuither backwards 

 until it reaches the gut and gains a connexion with it in the region 

 of the neurenteric canal. 



