884 DEVELOPMENT AND STRUCTURE OF PINEAL EYE IN LACERTILIA, 



The antero-posterior axis of the eye becoming much greater, and 

 (2) the lens in the region of the optic axis becoming more convex 

 internally. 



While the eye has been undergoing these changes great alteration 

 has also taken place in the epiphysis. It is no longer the simple 

 hollow stalk which we saw in the first stages, but it has acquired 

 the complex form shown in fig. 9. Its end is seen to be separable 

 from the pineal eye by a considerable interval. This interval is, 

 however, not so great in the later forms, owing I think, to the 

 forward growth of the mid-brain pressing the pineal gland more 

 towards the eye. 



In examining the outward modification that takes place in 

 the adult lizards in reference to the pineal eye, we note the 

 following: — In Grammatophora (fig. 16), on the dorsum of the 

 head at a point which is the apex of a triangle whose base may be 

 considered as lying between the ])aired eyes, we find a white oval 

 scale which indicates the pineal locality. This white body is the 

 cuticle of the middle region of a scale, modified to form a cornea ; 

 it is quite devoid of pigment. On removing the cornea, we find 

 a dark spot (fig. 17) lying in the centre of a concavity. The dark 

 spot is the pineal eye lying in the j)arietal foramen, surrounded 

 by unpigmenced tLssue. Its appearance is shown in fig. 17. 



In Hinulid no modification takes place in the scale to form a 

 cornea, the only indication being a dark spot (fig. l-t, Pa. E.) in the 

 deltoid-shaped scale. A mass of pigment in the same scale, but 

 anteiior to the eye, might be mistaken for it. On removing the 

 scale the eye is seen as a black spot with a clear centre (lens) 

 placed in the parietal foramen (fig. 15). 



On comparing the forms which I have described, with those 

 forms described by Spencer, the following are some of the points 

 which are similar, or dissimilar : — 



(1) A scale is modified to form a cornea in Grammatophora, 

 this being similar to such forms as Calotes, Varanus, etc. 



(2) The lens is double-convex in outline, a point which appears 

 to be common to nearly all the forms in which the eye is known. 



