BY W. J. McKAY. 879 



but a single layer of squames resting on a layer of culjical cells 

 represents the epidermis. There are no signs of pigment beneath 

 the epidermis. The eye with the end of the epiphysis causes a 

 marked bulging on the sui-face. 



Shape of the Eye. — The eye is at this stage ovate in longitudinal 

 vertical section, its long axis being placed parallel to the long axis 

 of the head of the lizard, and it is slightly dorso-ventrally compressed. 

 The following are the parts into which it is differentiated : above 

 the lens, below the retina, and between these two the optic vesicle. 



Lens. — The lens is concavo-convex in shape, the convexity 

 being on the superior side. It is nearly the same thickness 

 throughout, though where it becomes continuous with the retina it 

 is slightly thinner. It is cellular in structure, and is composed of 

 two layers of columnar cells with round nuclei. The nuclei stain 

 very darkly, and lie in two rows about the optic axis ; but at the 

 place where the lens joins the retina the nuclei lie as a single row 

 close to the external limit of the lens. 



Retina. — The retina at this stage could be very well investigated 

 histologically. It is composed of the following layers : — 



First Layer. — Composed of rods (fig. 6, S.), occupying about ^ 

 of the whole thickness of the retina. These rods are closely placed 

 side by side, and form the boundaiy to the optic vesicle ; distinct 

 oval nuclei with granular contents coidd be seen lying in the 

 middle and lower portions of the rods, These nuclei do not stain 

 very deeply. The rods end inferiorly by tapering to a point, 

 and processes run from these points down into the retina below. 



Second Layer (iV'). — Is composed of spherical nucleated bodies. 

 These bodies do not stain very deeply. They run round to where 

 the lens joins the retina and then stop. Processes are given off 

 from these elements, some of which run up to the rods, but the 

 majority run down to the other retinal elements below. 



Third Layer (iV^"). — A layer of spindle-shaped bodies staining very 

 deeply. No nucleus could be detected owing to the in tenseness with 

 which these bodies took the stain ; 1)ut they seem to represent the 



