366 s. HATTA : 



clorsally when the development proceeds further (fig. Ill, co.sd. 

 and c.dv.). 



I have also met with two cases (figs. 00 and 111), in which 

 I have observed some epiblastic cells of the external lateral 

 walls of the blastopore multiplying actively and having mitotic 

 spindles [x) with axes directed perpendicularly to the plane of the 

 epiblast, while the duct comes in firm connection with that 

 point of the epiblast, — the connection is so firm that the duct 

 and the epiblast appear to form one and the same tissue. At 

 this point, thus, there is every appearance of epiblastic cells 

 partaking in the construction of the segmental duct. 



The collecting duct pertaining to the ninth somite forms 

 the segmental duct in that segment, having lost the connection 

 with the tubule. 



Up to Stage II, the duct is represented by the segmental 

 Anlagen in about 8 segments back of the ninth somite ; in Stage 

 III, these Anlagen are converted into the duct in about 10 an- 

 terior segments ; while in the course of Stage iv it opens out 

 into the cloacal cavity. 



From the above account, it is easily conceivable that the An- 

 lage of the segmental duet and that of the jjronephrie tubule are 

 perfectly homologous, and that the duet is a continuation of a series 

 of abortive pronephric tidmlex in the hind region. 



Underneath ten and more myotomes lying posterior to about 

 the fifteenth somite the proximal portion of the lateral plate, 

 which corresponds to the nephrotome, contains peculiar large 

 cells (figs. 87, 88, and 89, //r-.) loaded with an enormous quantity of 

 yolk-granules ; the other mesoblastic cells in this part, being 

 much flattened out, form a thin layer o^or these cells. These 



