3o6 SCOTT. [Vol. I. 



PLATE IX. 



Fig. II. Horizontal section through the anterior part of the head of a 

 larva of i6 dajs (lo mm.). 



Fig. 12. Sagittal section through head of a larva of 12 mm. 



Fig. 13. Lateral sagittal section through brain of a 13 mm. larva. 



Fig. 14. Median sagittal section of the same. 



Fig. 15. Horizontal section through the superior portion of the brain of 

 22 mm. larva. 



Fig. 16. The same, taken in a more ventral plane. 



Fig. 17. Transverse section through the infundibulum and pituitary body 

 of a larva of 53 mm. 



Fig. 18. Sagittal section through the olfactory organ, showing the organ 

 of Jacobson (larva of 12.5 mm.). 



Fig. 19. Horizontal section through the same. 



Fig. 20. The same ; larvae of 20 mm. 



Fig. 21. Sagittal section in the median plane through the nasal capsule 

 and fore-brain of adult Petromyzon. The epidermal cells are diagrammatic. 



