PINEAL EYE IN LACERTILIA. 203 



parative size. These poiuts are indicated in fig. 36 where the 

 eye is drawn as a solid object. It will be seen that it lies 

 close beneath the surface, the skin being here completely 

 devoid of pigment and quite smooth, forming in fact a cornea 

 {Cor.). As far as could be ascertained, though the point could 

 not be determined with certainty owing to the state of preser- 

 vation of the specimen, the eye is connected, as represented 

 diagrammatically with the proximal part of the epiphysis by 

 the solid pineal stalk (Op. s. ?). 



Leiodera nitida, PI. XVII, fig. 22; PI. XIX, fig. 38. 



External Appearance. — The specialised scale (PI. XIX, 

 fig. 38) forms a prominent feature in the median dorsal line of 

 the head, bearing in its centre a small dome-shaped structure 

 perfectly white, and hence standing out in clear contrast to 

 the deeply-pigmented scale, of which it is a specialised 

 portion. 



Position of the Eye. — The organ lies closely embedded 

 in connective tissue, and not really filling up the parietal 

 foramen, than which it is considerably smaller. The layers of 

 the skin above it are so modified as to form the external dome- 

 shaped structure already noticed, whilst pigment is markedly 

 absent from this part, though present on either side (fig. 22, 

 Ct, pig.). A very striking feature in section is the peculiar 

 elongation of the cells of the rete mucosum {R. M.), whose in- 

 ternal ends appear in many cases to be prolonged downwards, 

 each cell being so placed that its long axis is at right angles to 

 the surface at that particular spot. The connective tissue, 

 further, very closely invests the eye, whilst no such well- 

 developed blood-vessel is to be recognised as is met with in 

 most cases. 



Structure. — The organ has a very definite shape shown in 

 fig. 22, being depressed dorso-ventrally, as a result of which the 

 cavity of the vesicle is very small. 



Lens. — The lens is well developed, and, as usual, cellular, 

 the nuclei of its cells being prominent in section, and so 

 arranged that they form in the main a line from side to side. 



VOL, XXVII, PART 2. NEW SER. P 



