PINEAL EYE IN LACERTILIA. 235 



joining into one and tlie two main strands tiieu uniting to form the solid pineal 

 stalk. The large blood-vessel accompanying the stalk enters the foramen, 

 together with the latter. 



Fig. 2. — Longitudinal vertical section through the connective tissue capsule 

 containing the pineal eye of Hatteria punctata. The right side is the 

 anterior, the left the posterior, the external surface of the head being parallel 

 to the breadth of the plate. The capsule is formed anteriorly by the con- 

 nective tissue filling up the parietal foramen. Into the capsule passes a 

 blood-vessel, which ramifies amongst loosely scattered connective-tissue fibres. 

 The anterior part of the capsule is comparatively empty, but special fibres 

 pass from the walls to the sides of the lens. The optic vesicle is cut through 

 in the median line, showing the cone-shaped lens and the elements of the retina 

 together with the pineal stalk entering posteriorly. 



Fig. 3. — Section through the retina of Hatteria punctata. The left is 

 the internal, the right the external surface. Internally the shade indicates 

 the fluid within the vesicle, bounding the cavity of which are the rods lying 

 in pigment. External to the rods lie the inner spherical-shaped elements, 

 then the molecular layer, and external to the latter larger spherical bodies 

 together with conical and spindle-shaped bodies, the latter two being in con- 

 nection with nerve-fibres. (In the figure the nerve-layer has been drawn so 

 as to appear more prominent than it is in reality.) 



Fig. 4. — Section through the portion where the pineal stalk enters the walls 

 of the vesicle. The specialised bundle of rods lying in the optic axis, with 

 the nuclei in connection with them, are seen together with the retinal elements 

 around the entrance of the nerve-fibres of the stalk. The fibres run round 

 in front of the capsular-like structure which contains the specialised nucleated 

 elements, sending some to these on either side, the remainder passing on and 

 either (1) entering into connection with the elements nearest to the pineal 

 stalk, or (2) passing farther on to form a layer of nerve-fibres on the external 

 surface of the vesicle. 



Fig. 5. — Separated rods from the retina of the pineal eye of Hatteria 

 punctata. The pigment is so deposited as to produce the effect of 

 striations. 



Fig. 6.— Section through the retina of Varanus giganteus. The rods 

 lie embedded in pigment on the internal surface, passing into the cavity of 

 the vesicle ; the shade on the left indicates the humour within the latter. The 

 reticular nature of the retina external to the rods is seen, the nuclei of the 

 spherical elements being coloured red. The internal spherical elements are 

 situated within the molecular layer ; amongst the external ones are large 

 masses of pigment ; more external still is a thin layer of nerve-fibres, and 

 outside this the connective-tissue fibres enclosing the optic vesicle. 



VOL. XXVU, PART 2. NEW SER. K 



