SAKGE^■T: THE OPTIC EEFLEX APPARATUS OF VERTEBRATES. 257 



EXPLANATION OF THE PLATES. 



Except where otherwise stated, all the figures are oriented so that the dorsal side 

 is uppermost, and tlie anterior end at the left. All the figures are drawings from 

 single sections, except where the contrary is noted. Each drawing was outlined 

 with an Abbe' camera lucida. 



ABBREVIATIONS. 



partial decussation of 

 tlie tractus tecto-cere- 

 bellaris. 



dorsal decussation of the 

 tectum opticum. 



epiphysial decussation. 



diacoele. 



dendrites. 



ependyma. 



epiphysis. 



Meynert's bundle. 



fasciculi of axons which 

 unite to form Reiss- 

 ner's fibre. 



ependymal fibres. 



habenular elements of 

 Reissner's fibre. 



neuroglia fibres. 



Reissner's fibre. 



median ventral fissure 

 between the lateral 

 lobes of the torus 

 longitudinalis. 



fundament of the epen- 

 dymal thickening. 



ganglion habenula 

 dextra. 



ganglion habenula 

 sinistra. 



pigment granules. 



hypophysis. 



infundibulum. 



hyaline layer, 

 limitans externa. 



limitans interna, 

 mesocoele. 



