Neal. — Nervous Syst. Squalus. 



PLATE 1. 



All figures magnified 43 diameters, and oriented on the plate with the chief axis 

 horizontal, the anterior end of the embryo to the riglit. The embryo made trans- 

 lucent was drawn in outline with camera lucida and afterwards studied as an 

 opaque object. 



Fig. 1. A dorsal view of an embryo with 6 to 6| somites. The edges of the neu- 

 ral plate are seen to be irregularly lobed. The two deep depressions at 

 the anterior end of tlie cephalic plate mark the position of tiie future 

 fundus of the infundibulum. 



Fig. 2. A ventral view of the same embryo. Loc3''s segments are seen as lobings 

 of the ventrally recurved margin of the neural plate. 



Fig. 3. A ventral view of another embryo of the same stage of development. The 

 specimen was dissected to sliow the chorda, a rod in the median axial 

 line, on either side of which lie the somites, van Wijhe's seventh somite 

 being designated as 7. An asterisk (*) marks the posterior boundary of 

 the cephalic plate. 



