348 s. HAïTA : 



besicles tlie cross-section of a duct (ed.), there is seen a pronephric 

 tubule {pt.6), tlie long axis of which is directed vertically to 

 the inner surface of the epiblast. It is found just beneath the 

 ninth myotome where the sixth tubule should be found. Al- 

 though the parts of it are also to be seen in two consecutive sections 

 (the one represented in fig, 86 and another preceding it), 

 the communication of its lumen with the collecting duct is not 

 to be found anywhere. In some embryos, the tubule loses the 

 connection with both the body-cavity and the duct. The structure 

 {pt.6) in question is, I believe, nothing else than the remnant of the 

 sixth tubule which is in a stage of degeneration, and the duct (cd.) is 

 doubtless the collecting duct between the tubules of the fifth and 

 sixth pairs. Compare the segmental duct (sd.) on the left side with 

 the collecting duct (cd.) on the right side just described ; the latter 

 has a wide circular lumen, whilst in the former it is slender and 

 compressed. This difference of character between these two 

 ducts is noticeable for some time in the younger stages. 



To sum up ilie results obtained in this stage the tubules of the 

 third to the ßj'th pairs are vigorously developed, ivhile the second 

 is very weak, the sixth retrograding, and the first has entirely 

 disappeared. 



In the present stage, a peculiar structure is observed inside 

 the walls of the body-cavity (figs. 77-85, pp.1-3). At some points 

 of the peritoneum, a thin plate which consists, in cross-section, of 

 one, two, or three cells, projects from the peritoneal wall into the 

 body-cavity; it will be called here shortly the '"''peritoneal parti- 

 tion.'''' A peritoneal outgrow^th is found at the level wehere the 

 coelomic projection passes over to the visceral layer of the lateral 

 plate ; at the same level, another peritoneal outgrowth starts up out 

 of the parietal layer. These two outgrowths meet at midway 



