Kingsbury, Brain of Nectunis. 205 



PLATE XI. 



Fig. 2S. Transection at the level of the optic nerves. The tract of the 

 supracommissure is also shown passing to the lateral walls of the cerebrum. 

 X 18+ . 



Fig. 2g, Transection slightly caudad of the portas. Fibers are shown col- 

 lecting from the caudal mesal walls of the hemicerebrum and from the dien- 

 cephal to take part in the dorsal commissure, the caudal edge of which is also 

 shown. The diatela is greatly expanded, x i8+. 



Fig. JO. Transection through the precommissure and the portas, through 

 which extend the paraplexuses, intruding from the supraplexus, which encloses 

 the paraphysis. The fibers of the dorsal commissure appear as a bundle roof- 

 ing the portas. Compare with the more caudal section, Fig. 42. x 18+. 



Fig. j>/. A transection just cephalad of the terma where the paracoeles are 

 limited in the mesal walls by endymal cells alone, x 18+. 



Fig. 32. Farther cephalad than section 31. The cinerea reaches the ectal 

 surface in the mesal walls, x 14+. 



Fig. ^j. A transection through the olfactory lobes showing the glomerules 

 and the ectal cinerea upon the ventral and dorsal aspects in this region, x 18+. 



Fig. 34. A frontal section through the prosencephal. x 6.6. 



Fig.j^. A frontal section at a more ventral level. It may be compared 

 with the preceeding and with Figs. 44 and 42 for the relations of the dorsal 

 commissure, x 6.6. 



Fig. ^6. A frontal section near the ventral surface of the brain. It shows 

 a decussation of a portion of the olfactory fibers ventrad of the precommis- 

 sure. X 6.6. 



Fig. jy. A frontal section through the chiasma. x 12.5. 



Figs. jS, J9 and 40. Sagittal sections through the brain, 38 the most near- 

 ly mesal. In Figs. 38 and 39 appear fibers of the dorsal commissure, in all, the 

 transverse commissure. Fig. 39 also shows Meynert's bundle and the postcom- 

 missure. x 11 — . 



Fig. 41. A mesal section through the brain of a larval Necturus, 4 weeks 

 old. Reconstructed from sagittal sections through the head, x 9. 



Fig. 42. A transection through the dorsal commissure. A portion of the 

 precommissure only is shown, so that the relations are not well represented in 

 transection, for which the mesal section should be consulted, Fig. 4. Fig. 42 

 is intermediate between Figs. 29 and 30. x 9. 



