268 PROFESSOR MARSHALL AND EDWARD J. BLES. 



Fig. 1 2. 9 mm. tadpole. A diagrammatic horizontal section through 

 the anterior part of the tadpole, showing the heart and 

 the vessels, both afferent and efferent, of the first three 

 branchial arches. On the left side, the section is taken 

 at a more dorsal level than that of the right side, and 

 the second and third branchial clefts are shown opening 

 to the exterior : (X 45). 



Fig. 13. 12 mm. tadpole. A diagrammatic figure of the anterior 

 part of the tadpole, seen from the right side, and showing 

 the condition of the heart and blood vessels : ( X 45). 



Fig. 14. 12 mm. tadpole. A diagrammatic horizontal section through 

 the anterior part of the tadpole, showing the heart and 

 the afferent and efferent branchial vessels in the floor of 

 the pharynx, seen from above : ( X 45). 



Fig. 15. 23 mm. tadpole. A diagrammatic transverse section through 

 the head, passing through the auditory organs, showing 

 the heart and branchial vessels in section. On the left 

 side, the section is taken at a level rather further back 

 than that of the right side of the figure : ( X 22). 



