342 s. H ATTA : 



67 (p/.2). The shape, which tlie tnhules of the second pair (fig. 06, 

 pt.2) assume at about this stage, is a characteristic triangle, 

 whose two angles, the one directed dorsally and the other directed 

 medially, are acute and whose outer (lateral) angle is obtuse 

 (see the left side of fig. 59 and the right side of fig. (^ß,pl;.2) ; so 

 much so that we can easily determine by this feature the fact 

 of their being the second pair. This peculiar shape of the second 

 tubule is retained for a considerable time as will be seen further 

 on. On the right side of fig. 67, the collecting duct (cd.) is cut 

 through transversely ; on the left, the same duct {rd.) and the 

 hind part of the second tubule {pt. 2) are seen. 



At the point where the nephrostome oj^ens to the peritoneal 

 cavity, the visceral peritoneum at the median corner of the latter 

 projects out between the myotome and the hypoblast (figs. 66 and 

 67, c.p.) ; beneath the collecting duct, however, no such structure 

 is detected (see the right side of figs. 6f5 and 67). 8uch a pouch 

 is repeated in each nephrotome (see figs. 66-75, c.p.) and is what 

 has been called above the coelomic projection.^' 



The next following sections shown in figs. 68 and 69 show 

 the third pair of the tubules {pt.3) to be of the same structure. 

 In these two sections the tubules are cut through lengthwise, and 

 the nephrostomes {nst.3) on the two sides come into view in sym- 

 metrical manner. The tubules are so simple as to need no further 

 explanation. Fig. 70 represents a section through the intersomitic 

 plane between the sixth and the seventh somites, and next posterior 

 to fio;. 69. It shows on either side the cross-section of only the 

 collecting duct (ed.), consisting of radially arranged cells. Fig. 

 71 is from a section through the seventh somite and is the third 



1) In this series of sections^ we often see the coelomic projection on sections passing 

 tlirongh the intersomitic plane; Init this is the piece of it belonging to eitlier the anteriorer 

 the posterior somite. 



