LIST OF ILLUSTRATIONS. 



FIG. PAGE 



1. Outlines of the spinal cord with the dorsal and ventral roots in 



Petromyzon and in a mammal 14 



2. The brain of Heptanchus 15 



3. The medulla oblongata of the lake sturgeon (Acipenser rubi- 



cundus), to show the longitudinal zones 16 



4. Two views of the brain of the buffalo fish, Carpiodes velifer 



(Raf.); (i) from above; (2) from the right side. From C. 

 Judson Herrick after C. L. Herrick 17 



5. Simple diagrams of the branchial nerves of lower vertebrates 



as seen from the left side iQ 



6. A diagram of the lateral line canals and pit organs together 



with the nerves which supply them, in a ganoid fish (Amia 

 calva). After E. Phelps Allis 21 



7. A sketch of the brain of Chimaera monstrosa from the left side 



to show especially the position of the nerve roots 23 



8. The outline of the brain ventricles as seen from above; A, of 



a cyclostome fish, Lampetra Wilder! ; B, of a selachian, 

 Mustelus canis; C, of a young specimen of a bony fish, Co- 

 regonus albus; D, of a tailed amphibian, Necturus macu- 

 latus 25 



9. A diagram of one side of the forebrain in Mustelus to show 



what is believed to be the primitive relations of the wall and 

 ventricle 26 



10. The outline of the ventricles in man 26 



11. The mesial surface of the right half of the brain of a selachian, 



Squalus acanthias " ' 29 



12. A sketch of the brain of a cyclostome fish, Lampetra Wilderi, 



as seen from the left side 30 



13. Sections of the neural plate and folds in amphibia, Amblystoma 



tigrinum and A. punctatum 35 



14. Transverse section of the neural tube of Amblystoma puncta- 



tum just after closing 36 



xi 



