A NEW CRANIAL NERVE IN SELACHIANS. 55 



PLATE VI. 



Fig. 10. Frontal view of the brain of an embryo of Squalua acanthias 25 mm. long. X about 26. 



Fig. 11. Right half of the brain of an embryo of Squalus aeanthias 38 mm. long, to show the course of the new 



nerve and its connection with the lateral division of the olfactory nerve. This stage is before the 



appearance of the olfactory lobe. X about 20. 



Fig. 12. Ventral view of the brain of an embryo of Squalus acanthias 40 mm. long. X about 8. 

 Fig. 13. Dorsal view of the brain of an embryo of Squalus acanthias 68 mm. long. On the right side a dissection 



has been made of the new nerve and the bundles of the olfactory. X about 7. 

 Fig. 14. Dorsal view of a brain of an embryo of Squalus acanthias 47 mm. long. As in Figure 13, a dissection 



has been made on the right side. X about 8. 



Fig. 15. Dorsal view of the brain of Squalus acanthias in the "pup " stage, 150 mm. long. X about 4. 

 Fig. 16. Dorsal view of the brain of a half-grown Squalus acanthias. Compare with Figure 15. Note the be- 

 ginning of the olfactory tract. Compare also with Figure 1 (PL V). X about 1J. 

 Fig. 17. Partly diagramatic figure of a horizontal section of the brain of Squalus acanthias at the "pup" stage, 



showing the branches of the new nerve within the brain substance. X about 5. 

 Fig. 18. Sagittal section of the brain of Squalus acanthias at the "pup" stage, showing the course of the fibres 



of the new nerve as seen from the side. X about 5. 

 Fig. 19. Cross-section of the brain of Squalus acanthias at the "pup" stage, showing the position of the main 



branches of the new nerve. X about 5. 



