The pronephros of Scyllium canicula. 263 
Fig. 52 (Section 2,40). The nature of the pronephros it not so 
clear on the right side of the embryo owing to the large glomus in this 
section; the groove-like nature of the organ is shown on the opposite 
side however. 
Fig. 53 (Section 2,41). This section passes through the middle of 
protovertebra VII. Whereas in the preceding figure the glomus seems to 
be fused with the inner lip of the primitive kidney groove, in this figure 
it seems to be fused with the outer edge, whereby the groove appears 
to open into the nephrocoel instead of into the general coelom. 
Fig. 54 (Section 2,42). In this and the next four sections a pronephric 
artery passes off from the aorta to the glomus. 
Fig. 55 (Section 2,43). Notice the relations of the pronephros on 
each side in this section. 
Fig. 56 (Section 2,44). This section and the next pass through an 
intersegmental region on the right side of the body, between somites 
VII and VIII. It will be seen that whereas the nephrotome region is 
metameric, the part of the mesoderm with which the pronephros is 
associated is unsegmented. 
Fig. 57 (Section 2,45). The groove-like kidney rudiment, which 
was quite obvious in the preceding section, is now assuming the appearance 
of a solid outgrowth on the right side of this figure. 
Fig. 58 (Section 2,46). The pronephros is now a solid outgrowth 
of the somatic mesoderm on each side of the body. 
Fig. 59 (Section 2,47). The glomus is closely approximated to the 
somatic mesoderm lateral to the pronephros. 
Fig. 60 (Section 2,48). An isolated vascular structure seems to be 
left in the region opposite the pronephros on the embryo’s right side. 
IDilattre223: 
Fig. 61 (Section 2,49). The vascular structure mentioned in connection 
with the last section is again in communication with the glomus. 
Fig. 62 (Section 2,50). Passes through the middle of protovertebra 
VIII on each side. 
Fig. 63 (Section 2,51). The pronephric groove appears to have an 
opening into the nephrocoel on the right side of this figure whereas in the 
section in front and in section 2,54 (Fig. 66) behind, the groove appears 
to open into the general coelom. This appearance is due to the projection 
of splanchnic mesoderm (homologous with that on the other side in 
section 2,39, Fig. 5l), which fuses with the upper edge of the groove 
in figs. 62 and 65, and with the lower edge in figs. 63 and 64. 
Fig. 64 (Section 2,52). Passes through somite VIII on each side. 
Fig. 65 (Section 2,53). The pronephrie rudiment on the left side 
of the figure is becoming differentiated into a proximal narrow tubule 
portion, and a distal rounded duct portion. 
