The pronephros of Scyllium canicula. 265 
Fig. 79 (Section 2,63). The groove on the left side of this figure 
(about the middle of somite VIII), is again open: the portion of the 
coelom into which it opens is apparently nephrocoelic, since it is segmental. 
The groove on the right side is just about to close. 
Fig. 80 (Section 2,64). The pronephric groove is now completely 
closed off from the coelom on each side, but has a solid connection 
with it. 
Fig. 81 (Section 2,65). The wall of the vitelline artery is no longer 
connected with the gut-wall; there is a solid connection between duct and 
coelomic lining on each side. 
Fig. 82 (Section 2,66). The duct on the right side of the figure is 
probably again open (the second left pronephric nephrostome). The duct 
is still closed on the other side. 
Fig. 83 (Section 2,67). The duct on the right side of the figure is 
shut off from, but has a solid connection with, the coelom; on the other 
side the duct is open to the coelom — the third right pronephric 
nephrostome. 
Fig. 84 (Section 2,68). The pronephros is open to the coelom for 
the last time on the left side of the figure, and since this nephrostome 
happens to be situated practically intersegmentally in position, it opens 
into the general coelom, not into the nephrocoel. On the right side of 
the figure the duct is completely shut off from the coelom, and has not 
even a solid connection with the coelomic lining. 
Plate 25 
Fig. 85 (Section 2,69). In and posterior to this section the pro- 
nephric duct on each side is quite distinct from the coelomic epithelium 
beneath. 
Figs. 86—96 are taken from successive sections of Embryo K, in the 
region of the degenerating pronephros. 
Fig. 86 (Section 3,65). The proximal end of the vitelline artery is 
seen in this section. 
Fig. 87 (Section 3,66). Notice the pronephros on each side as a 
groove of the coelomic lining. This section passes between somites VII 
and VIII on the embryo’s right side. 
Fig. 88 (Section 3,67). The glomus-like projection of the vitelline 
artery is tending to fuse with the upper inner edge of the pronephric 
groove. 
Fig. 89 (Section 3,68). Shows a vascular fusion on the left side of 
the figure between glomus and the upper edge of the pronephric groove. 
Fig. 90 (Section 3,69). The fusion is spreading to the ventral lip 
of the groove on the left side of the figure. A pronephric artery is 
also seen. 
