PINEAL EYE IN LAOERTILIA. 21 1 



proximal portion of the epiphysis by a fibrous strand, such as 

 is represented by De Graaf as connecting the distal with the 

 proximal portion of the epiphysis in Bufo cinerea. 



Seps chalcidica, PI. XVIII, fig. 32; PL XX, fig. 5. 



External Appearance. — The external modification is not 

 so evident in this form as in some others. If one of the 

 median scales posterior to the paired eyes on the dorsal surface 

 of the head be examined it will be found to have upon it a 

 dark-coloured oval patch (hence distinguishable from the 

 yellow-brown surface of the scale) ; this, which has the charac- 

 teristic appearance of a membrane stretched over a space 

 beneath, indicates the position of the eye lying beneath it. 



Position of the Eye. — The eye lies somewhat on the inner 

 side of the foramen (PI. XVIII, fig. 32), there being as usual 

 no pigment between it and the external surface. It is remark- 

 able in being the only one in the forms yet examined, which is 

 larger than the foramen ; its relation to this is shown in the 

 figure, where it is seen that the parietal bones overlap it on each 

 side to a small extent ; if by any reason the foramen became 

 closed then the eye would be situated intracranially, whilst in 

 Amphibia the position is always extracranial, when the distal 

 vesicle of the epiphysis becomes, as in Anura, separated off 

 from the proximal. The eye is surrounded immediately by a 

 great development of pigment bearing tissue which fills up 

 what part of the foramen is not occupied by the organ itself. 



Structure. — The whole eye is, in longitudinal vertical 

 section, seen to be elliptical in shape, the long axis correspond- 

 ing in position with that of the head and hence forming a strong- 

 contrast to such an eye as that of Anolis (PI. XVIIJ, fig. 24). 



Lens. — The lens is distinctly cellular, the nuclei of the 

 constituent cells forming a line prominent in section across 

 from side to side, slightly nearer to the inner than to the 

 outer surface ; the whole is doubly convex in shape, thickest 

 in the line of the optic axis, and thinnest where it is continuous 

 with the retina. 



Retina. — The specimen not being in very good order histo- 



