350 s. HATTA : 



its caudal continuation {sd.) is the segmental duct ; while the inner 

 two layers {m.v. and 7ii.p.) present respectively tlie parietal and 

 visceral layers of tlie lateral plate. Below these structures, the 

 roof of tlie enteric canal covers the fore-gut (fff.) and the com- 

 mencement of the mid-gut which forms the passage of the enteric 

 cavity from the anterior slender portion to the posterior wide 

 cavity. In fig. 113 which represents the section next outside the 

 last, the lateral walls of the five myotomes from the first to the 

 fifth {int.I-V) are noticed ; the cell-mass {au.) seen next anteriorly 

 to the first myotome {mt.l) is a slice of the wall of the left auditory 

 pit. The cross-sections of the pronephric tubules from the second 

 to the fourth {pt.2-4) follow immediately behind the fifth 

 myotome ; an oblique section of the fifth tubule (pt.ô) and the 

 nephrostomal part of the sixth tubule (j^t.O) are also obvious 

 behind the fourth tubule. The nephrostomes of the second 

 {nst.2) and fifth {nst.ô) tubules are seen only in part, while a 

 larger part of the third, fifth and sixth nephrostomes is seen in 

 the next figure (fig. 114, 7ist.3, o, and 6') which represents a 

 section still further outside. The sixth tubule, which is of weak 

 development and has a wide nephrostome, is visible in these two 

 sections (figs. 113 and 114, pLG and nst.G). Except the first tubule 

 which has already disappeared without leaving any trace, the five 

 tubules are all thus seen in the dorso-lateral aspect of the hind 

 section of the fore-gut and the commencement of the mid-gut. 

 The pronephros is thus situated in the neck which connects 

 the head-protuberance with the globular abdominal portion. 

 Below the pronephros, the narrow passage of the fore-gut passes 

 through to unite the fore-gut with the wide space of the mid-gut, 

 where after \vards the liver [1.) is found. Underneath the passage 

 of the fore-gut, a group of mesenchymatous cells {mch.), which 



