PINEAL EYE IN LAOEETILIA. 181 



represents the originally hollow process uniting the proximal 

 with the distal portion of the epiphysis, and which, losing its 

 connection with the optic vesicle in some forms (e. g. Anguis), 

 is in others (e.g. Hatteria) transformed into a solid stalk 

 serving as the nerve of the pineal eye. It has been sufficiently 

 demonstrated that the latter is the distal portion of the epi- 

 physis, and we are thus presented with a new sensory structure 

 — the pineal eye — agreeing precisely with the paired eyes in 

 (1) its development as an outgrowth from the walls of the neural 

 canal, and (2) the formation of its nerve by the gradual solidifi- 

 cation of the primitively hollow tube connecting the distal 

 vesicle with the proximal portion of the outgrowth. In the 

 case of the paired eyes the whole of the outgrowth save the 

 vesicle is transformed into a nerve ; in the pineal eye only the 

 median part of the outgrowth is thus metamorphosed, the 

 proximal part retaining its originally hollow nature. 



Varanus giganteus, PI. XIV, fig. 1, fig. 6; PI. XV, 

 fig. 10 ; PI. XIX, fig. 34. 



External Appearance. — In a large specimen of this 

 animal, measuring six feet one inch from the snout to the tip 

 of the tail, which I was enabled to examine in the fresh state 

 through Professor Moseley's kindness, the external indication 

 of the eye is so clear that it is remarkable that no one has 

 hitherto examined the organ lying beneath. The head is 

 covered with small, deeply-pigmented tubercle-like scales, save 

 in the median line, where, somewhat posterior to the paired 

 eyes, a single large scale is present, standing out prominently 

 by reason of its creamy whiteness (fig. 10). 



The scale is roughly hexagonal in shape, measuring 5 mm. 

 across, and has upon it a slightly-raised circular rim, the area 

 within which has the appearance of a transparent membrane 

 drawn tensely over a cavity beneath. A dark circular spot in 

 the middle, visible in the living animal, indicates the position 

 of the eye, and is, as will subsequently be shown, due to the 

 presence of a mass of pigment in the lens. In the matter of 



