176 W. BALDWIN SPENOEE. 



In the account which follows the structure of the organ is 

 described separately in the diflferent forms examined; this 

 structure, as might have been expected to be the case in an 

 organ of this kind (which must be regarded as in a more or 

 less rudimentary condition), shows considerable variation, even 

 amongst species of the same genus, I hope on a future occa- 

 sion to describe the organ in other forms of Lacertilia. 



Hatteria punctata, PL XIV, figs. 2, 3, 4, and 5; PI. XV, 

 figs. 7 and 8; PI. XX, fig. 7. 



(1) External Appearance. — There is in Hatteria but 

 very little external trace of the eye, no special scale being 

 modified into a " cornea f an absence of pigment, however, in 

 the skin of the median line, slightly posterior to the level of the 

 paired eyes, indicates the position of the parietal foramen; this 

 external indication being more evident in some than in others. 



(2) Position of the Eye. — The foramen itself is filled 

 up by a plug of connective tissue, which, notwithstanding the 

 absence of pigment, must effectually prevent the organ lying 

 beneath from functioning as an eye in the ordinary sense of 

 the word ; light would more easily penetrate the skin at this 

 than at any other portion of the surface of the head, but yet it 

 is perfectly impossible for an image to be formed upon the 

 retina. The fibres of the connective tissue in the foramen 

 may be divided into two sets — (1) an outer set (PI. XV, fig. 7, 

 Cf^) arranged on the whole at right angles to the surface of 

 the head, and which on the inner side of the foramen are con- 

 nected with (2) an inner set lying immediately in front of the 

 eye, and arranged so as practically to form a hemisphere, part 

 of the internal surface of which forms the anterior boundary of 

 a capsule enclosing the eye (figs. 2, 7, and 8, CP). The 

 hinder half of the capsule which thus lies in the lower part of 

 the foramen is formed of somewhat loosely aggregated fibres 

 with well-marked nuclei scattered irregularly amongst them, 

 and is drawn out in the direction of the optic stalk, which, 

 together with a blood-vessel, pierces the capsule wall at its 



