IN THE EYES OF CEETAIN IIEPTILES. 
7 
transparent point situated as usual, and close to the edge of 
this duplication of the retina : and, in a small variegated 
lizard, with lobated feet, I observed the foramen or <pomt 
very distinctly *. 
In the lizard called by naturalists the Gecko, the mar- 
supium is very small, and the foramen centrale, or trans- 
parent point, is wanting. Neither could I perceive it in 
the lizard called by naturalists Lanins (the Lacerta Ma- 
huyd) ; in them also the marsupium is very small, though 
distinct. We thus discover that the foramen of S(emme- 
niNG is found in a particular family of lizards, whilst it is 
wanting in others. Analogy would lead us to suspect its 
presence in the Chameleon, whose eye I have not yet had 
an opportunity of examining. It remains also to be dis- 
covered, whether the same anatomical distribution extends 
to the higher orders of lizards, as the Iguana, Tupinambis, 
and Crocodile f. 
There remains only a single additional fact which I wish 
to communicate in this notice ; it regards the supposed ex- 
istence of vessels passing between the foramen of SceMME- 
BiNG and the vitreous humour. With the view of deter- 
mining this point, I opened the eye-ball in situ with the 
greatest care, and watched the removal of the humours 
from the retina ; but however frequent the examination, I 
<;ould never discover the smallest appearance of blood- 
vessels, lymphatics, or membranes, connecting at this point 
the retina and vitreous humour. 
* These lizards belong more strictly to the class of true or proper Lizards 
than either the Supercilipsa or Calotes, 
•j* I have since ascertained that neither marsupium nor foramen centrale 
are present in the Crocodile. 
Edinburgh, ) 
Ju7ie W. 1823, j 
