NEAL, — Nervous Syst. Squalus, 
PLATE 2. 
All figures magnified 48 diameters and oriented as in Plate 1, The outlines 
were first made from the translucent embryos with camera lucida, and afterwards 
the embryos were studied as opaque objects. 
Fig. 4. An embryo with 4 somites viewed from the dorsal side. Locy’s segments 
are seen to be confined to the “marginal bands” of the cephalic plate. 
Fig. 6. An embryo with 10 or 11 somites viewed from the right side and partly 
from above. ‘The posterior part of the cephalic plate is seen to be 
sharply flexed ventrad on the right side. 
Fig. 6. An embryo with 12 somites viewed from the right side. The neural folds 
in the region of the cephalic plate have not yet met in the mid-dorsal 
line, The demarcation between cephalic plate and trunk is seen to be 
| sharp. The anterior three primary vesicles (encephalomeres I, II, and 
III) appear in surface study as shown in the figure. In neither this 
embryo nor in the one represented in Figure 5 do Locy's segments 
appear. 
