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SCOTT. 



[Vol. I. 



EXPLANATION OF THE PLATES. (VIII, IX, X, and XI.) 

 Reference Letters. 



Hind-Brain. 

 Head Cavity. 

 Pituitary Body. 

 Optic Chiasma. 



Infundibulum. 



Organ of Jacobson. 



Lens. 



Lamina Terminalis. 



Mouth. 



Mid-Brain. 



Olfactory Epithelium. 



Lateral Nerve. 



Naso-palatal Canal. 



Olfactory Ganglion, 



Semicircular Canal. 

 , Superior Commissure. 



Spinal Cord. 



Spinal Ganglia. 



Ti-abecula Cranii. 



Choroid Plexus. 



Upper Lip. 



Errata. PI. VIII, Fig. 5, Opt points to the olfactory Epithelium, and 

 N.E. to the fore-brain. PI. IX, Fig. 14, the dotted line leading from In to 

 the optic tract should be erased. Fig. 21, for N. G. read N.E. 



PLATE VIII. 



Fig. I. Sagittal section through the head of an embryo Pctromyzon of the 

 17th day after impregnation. 



Fig. 2. Ditto of the iSth day. 



Fig. 3. Ditto of freshly hatched larva (4.S mm.). The cells in this draw- 

 ing are somewhat diagrammatic. 



Fig. 4. Enlarged view of the anterior portion of Fig. 3. 



Figs. 5 and 6. Other sections of the same specimen. These sections are 

 slightly oblique; in Fig. 6, the plane of section is median at the notochord, 

 but somewhat lateral at the nasal epithelium. 



Figs. 7, 8, and 9. Transverse sections through the fore-brain of a larva 

 6.8 mm. in length. 



Fig. 10. Section through the fore-brain of a larva 6 mm. long. 



