PLATE8 



All of the sections from which the following illustrations were made are stained 

 with hematoxylin and orange G and are six microns in thickness. Figures 2 to 9, 

 11, and 16 to 26 inclusive are camera lucida sketches drawn with a 2 mm. oil immer- 

 sion objective and a no. 8 ocular. Figures 1, 10, 12 to 15, and 27 to 3.5 were pro- 

 duced with the aid of the Edinger Projection Aj^paratus. All of the figures were 

 drawn as nearly as was possible at one plane of focus or optical section. 



PLATE 1 



EXPLAXATIOX OF FIGURE 



1 Transverse section of a 11 mm. toad embryo through the head at the le\el 

 of the eye. Series 35, slide 1, row 9, section 5. X 150. Reduced to X 75. 



REFERENCES 



/., ventral cephalic lymph sinus ./.r/., ./..?., right and left external jugular 

 /./., /./., lateral extensions or wings of veins 



the sinus which are joined to it fur- mx., mouth cavity 



ther forward 



184 



