PINEAL EYE IN LAOERTILIA. ^13 



of differentiation into lens anteriorly and retina posteriorly ; the 

 hollow connection with the brain persisting through life. In 

 such forms again as Calotes, Seps, or Leiodera the same 

 differentiation into an optic organ with retinal elements takes 

 place as in Hatteria, but the connection with the brain is 

 lost. In a few forms further, such as Chameleo vulgaris 

 and Lyriocephalus scutatus, the development of the epi- 

 physis is carried to a great extent, resulting in a division into 

 three parts, as in Hatteria, but the distal vesicle is not 

 differentiated into an eye, its walls retaining their primitive 

 structure. 



In Varanus giganteus a peculiar modification takes 

 place, seen in no other form examined ; the pineal stalk, which 

 is well developed, breaking up into three divisions before 

 the eye is reached, whilst in V. bengalensis the eye is 

 apparently separated from the proximal portion of the epi- 

 physis, and the part equivalent to the pineal stalk of the other 

 species is hollow and ends beneath the optic vesicle in a slight 

 swelling. 



(2) State of Retinal Elements. — Dealing with the 

 state of development of the retinal elements, the eyes are found 

 to differ to no little extent in this respect; thus in Hatteria 

 it is better developed than in any other form examined : in 

 Varanus, on the other hand, while the elements can be dis- 

 tinguished the whole eye is marked by a great deposition of 

 pigment ; even in the centre of the lens a large globular mass 

 is present which must effectually prevent the entrance of light 

 to the vesicle in the line of the optic axis, whilst, in addition 

 to this, many of the retinal elements degenerate into pigment- 

 bearing cells. In others, such as Anolis, almost all the 

 elements are enveloped in pigment, whilst in others, as Agama 

 hispida, so great is the deposition that it is not possible to 

 distinguish any elements save the rods. In contrast to this we 

 find in some genera, such as Chameleo and Lyriocephalus 

 that no pigment is present at all, and, accompanying this 

 absence of pigment, it is found that the vesicle is 

 not developed into an eye, its walls retaining their 



