308 Illinois State Laboratory of Natural History. 



Fig. 4. The glosso-pharyngeal aud vagus nerves, com- 

 pletely uncovered and drawn apart so as to show the 

 lateral line nerve at E. II. Garman del. 



Fig. 5. Side view of brain of Polyodpn turned so as 

 to show the infundibulum. F, hypophysis cerebri; G, 

 saccus vasculosus. Other letters and figures as in Fig. 3. 

 H. Garman del. 



y ' ^' 

 Plate IV. 



Fig. 6. Side view of brain oi Acipenser 7'uMcimdus. B, 

 •olfactory lobe; C, C, pineal stalk terminating distally in 

 the pineal end organ; D, fore-brain; E, infundibulum; 

 F, hypophysis cerebri; G, saccus vasculosus ; H, swelling 

 on side of infundibulum; I, mid-brain; J, cerebellum; M, 

 medulla oblongata; O, spinal cord: 1, olfactory nerve; 2, 

 optic nerve; 3, oculo-motor nerve; 4, 4, trochlear nerves; 

 5, 5, origin of trigeminal nerve; 7, origin of facial nerve; 

 8, origin of auditory nerve; 9, origin of glosso-pharyngeal 

 nerve; 10, origin of vagus nerve. The small enclosed 

 area connected with 10 by an arrow, marks the origin 

 of the lateral line nerve, a part of 10. H. Garman del. 



Plate V. 



Fig. 7. The exposed channel in which the pineal end 

 organ and its stalk lie in Polyodon. A, aperture to the 

 exterior. (The skin covering the cartilage has been re- 

 moved.) B, end organ; C, cut end of stalk. H. Gar- 

 man del. 



Fig. 8. Pineal end organ and a part of its stalk in 

 Polyodon, removed from the channel in cartilage, and 

 the end organ turned so as to show the surface presented 

 to the exterior. A, end organ enclosed in sheath and 

 with part of the elastic bands remaining attached; B, 

 cut end of stalk. H. Garman del. 



Fig. 9. Pineal end organ and stalk of Polyodon shown 

 in place. A, end organ; B, cut end of stalk; C, sheath 



