Sakoent. — Optic KuUex Ajiparatus. 



< PLATE 10. 



In all tlie figures the anterior end is at tlio riglit, and tlie dorsal side is toward 



the upper left-liand corner of the plate. 



Fig. GH. Morone americana, adult. Sagittal section through the posterior com- 

 missure and adjacent region. X 120. 



Fig. 69. Gasterosteus hispinosus, adult. Parasagittal section of the anterior por- 

 tion of tlu' midbrain roof. X 87. 



Fig. 70. IMicrogadus tomcod, adult. Parasagittal section through the posterior 

 commissure region. X 100. 



