Saeoent. — optic Keflex Apparatus. 



PLATE 10. 



In all tlie fifjnres the anterior ond is at tlic rifjlit, anil tlip dorsal side is toward . 



the upijer left-lianil corner of the plate. 



Fig. 68. Morone aniericana, adult. Sagittal section through the posterior com- 

 missure and adjacent region. X 120. 



Fig. 09. Gasterosteus hispinosus, adult. Parasagittal section of tlie anterior por- 

 tion of tlie midbrain roof. X 87. 



Fig. 70. Microgadus tonicod, adult. Parasagittal section through the posterior 

 commissure region. X 100. 



