HUBRECHT. Pl. O. 
iw 
86 
J 
Fig. 83 to 86. Four longitudinal sections of Hypogeophis (after Brauer, 
‘97). In Fig. 83 the downward proliferation of the ectoderm (gw protochordal 
wedge) commences to fuse with the entodermic protochordal plate 4/. In Fig. S4 
the notogenesis has proceeded further; in Fig. 85 the segmentation cavity has 
coalesced with the enteric cavity; in Fig. 86 the ventral mesoblast a has also 
made its appearance and the entoderm ev has spread below the notochord xc, 
y yolk. 
