Sargent. — Optic Keflex Apparatus. 



PLATE 6. 



Fig. 40. Amia calva, adult. Sagittal section, anterior at riglit, through the ante- 

 rior portion of tiie mesencephalic roof and posterior commissure, 

 showing the axons of tiie optic rcHex cells uniting in the ventricle. 

 Combined from several adjacent sections. X 41. 



Fig. 41. Polypterus bichir, adult. I'arasagittal section, anterior at right, througli 

 the anterior mesencephalic roof and posterior connnissure, showing the 

 relation of the optic rcHex cells to tiie posterior commissure, and the 

 axons uniting in the ventricle to form Reissner's fibre. Combined from 

 several adjacent sections. X 41. 



Fig. 42. Polypterus bichir, adult. Paras;igittal section, anterior at right, of the 

 anterior portion of the left optic lobe, some distance laterad of the pre- 

 ceding, showing some of the laterally lying optic reflex cells. X 87. 



Fig. 43. Anieiurua nebulosus, larva, 15 cm. Sagittal section of posterior end of 

 the spinal cord, showing Reissner's fil)re and two posterior canal-cells. 

 X 900. 



Fig. 44. Lepidosteus osseus, larva, 1st day after hatching, 10 mm. Sagittal sec- 

 tion anterior at left, of mesencephalic and diencephalic roof, showing 

 the optic reflex cells whose fine axons project into the ventricle. The 

 posterior connnissure is not j'et developed. X 205. 



Fig. 45. Lepidosteus osseus, larva, 15 mm. Parasagittal section (tangential), ante- 

 rior at right, of j)osterior portion of spinal cord, in part through the 

 central canal, showing the branches of Reissner's fibre entering the 

 cord. X 380 ca. 



Fig. 46. Lepidosteus osseus, larva, 25 mm. Sagittal section, anterior at left, of 

 the posterior end of spinal cord and ventriculus terminalis, showing 

 two posterior canal-cells. X ^"0 



