PINEAL BYE IN LAOEETILIA. 201 



In connection with the eye a large blood-vessel (B. v.) is 

 developed which runs up by the side of the epiphysial process 

 to the foramen. 



Epiphysis. — The eye is, as far as could be told, completely 

 separated off from the brain ; the proximal part of the epi- 

 physis runs, as usual, at right angles to the dorsal surface of 

 the brain, whilst the median part corresponding to the pineal 

 stalk of other forms runs forward from the former along the 

 upper surface of the cranial cavity, ending blindly before the 

 foramen is reached (fig. 31, Ep^., Op. s.). 



Agama hispida, PI. XIX, fig. 39. 



The external indication of the eye is very clear in this form, 

 consisting, in a specially large scale placed medianly on the 

 head posteriorly to the paired eyes, in a slight depression and 

 surrounded by small tubercle-like scales. A raised white rim 

 encloses a circular space marked by a curious hour-glass 

 shaped, dark looking patch. 



Sections show that the organ lies within the parietal fora- 

 men and is almost spherical in shape ; above it the connective 

 tissue of the cutis vera is modified as in other forms (e. g. 

 Varanus bengalensis), and is entirely free from pigment, 

 the cells of the rete mucosum being also somewhat elongated 

 above the eye ; the latter is surrounded immediately by vacuo- 

 late tissue as in Cyclodus or Anolis (figs. 18 and 24). It 

 is difficult to determine the structure of the eye owing to the 

 fact that not only the rods, which are long and well marked, 

 but also the external part of the retina is deeply pigmented ; 

 it appears as if nearly all the elements lying external to the 

 rods had degenerated into pigment-bearing cells, amongst 

 which at intervals spherical elements corresponding to those 

 of other forms can with difficulty be distinguished. In many 

 cases processes, also pigmented, pass from the rods to the pig- 

 ment masses lying external to them. 



The lens is distinctly cellular and forms the transparent 

 anterior boundary to the optic vesicle, though as the walls of 

 the latter are comparatively thick the cavity is small ; even in 



