56 THE VOYAGE OF H.M.S. CHALLENGER. 



No. of Times 

 Magnified. 



Plate. Fig. 



VIII. 1. Fifth Stage, continued. — First Section of a series taken hori- 

 zontally; this, the uppermost, shows the cavity of the 

 cranium up to the post-clinoid region, and the fore part 

 of the hind skull, with the medulla oblongata in section ; 

 in front, the rhinencephala are cut across over the nasal 



cavities, 12 diam. 



,, 2. Second Section. — Here, the olfactory nerves are cut across, 



and the sides of the great post-pituitary wall, . . . 12 ,, 



,, 3. Third Section. — This shows the whole width of the hinder 

 cranial region, and the roof of the nasal labyrinth is 

 removed below the fore part of the cranial cavity, . . 12 



,, 4. Fourth Section.^ — Here the nasal cavities are fully laid open, . 12 

 ,, 5. Fifth Section. — This section runs through the external nostrils 



in front, and the upper part of the ear-capsules behind, . 12 



,, 6. Sixth Section. — This is so far down as to cut across the noto- 



chord in the post-clinoid wall; only the hind part is drawn, 12 



„ 6a. Part of the same, . _ . . . . . . . . 36 



IX. 1. Seventh Section. — This is so low down as to reach the palatal 

 skin at one part in front, and behind to lay open the 

 " meatus internus," . . . . . . . 12 



„ la. Part of same, . . . : . . . . . 36 



,, 2. Eighth Section. — In this half-section the pterygoids and 



epipterygoids are reached, . . . . . . 12 



,, 2a. Part of same, ......... 36 



„ 3. Ninth Section. — This section opens the lower mouth of the 

 pituitary space, the median nasal passage, and internal 

 nares, .......... 12 



„ 3a. Part of same, . . . . . . . . . 72 



„ 4. Tenth Section. — Here the floor of the mouth is shown, and 



the foramen magnum is seen at its middle part, . . 12 

 ■„ 5. Eleventh Section. — This last section shows the mandibles in 



situ, and the occipital condyle enclosing the notochord, . 12 

 X. 1. Sixth Stage. — Sectional view of skull, seen from the inside, . 5-^ 



,, 2. Side view of skull, ........ 54 



