PINEAL EYE IN LAOERTILIA. 183 



In addition to the connective tissue within the foramen a 

 large blood-vessel is present, which, accompanying the optic 

 stalk till the foramen is reached, breaks up in this into nume- 

 rous branches ramifying in the connective tissue (B.v.), a branch 

 finally passing from either side in front of the eye (fig. 1), 

 whilst one pierces the connective-tissue dome. 



Structure of the Eye. — The eye is, though the size of 

 the two specimens of Hatteria and Varanus are so dif- 

 ferent (Hatter ia under 2 ft., Varanus 6 ft.), as nearly as 

 possible precisely the same size in both, measuring, in the 

 line of the optic axis, '4 mm., but in Varanus the eye is 

 compressed somewhat in this direction, so that it is broader 

 from side to side slightly than in Hatteria (cf. figs. 1 and 2). 



Lens. — The lens is distinctly cellular in structure, the cells 

 being elongated in the direction of the optic axis, and having 

 the appearance of stretching the whole breadth of the lens, 

 their nuclei, which are very prominent, being situated so that 

 in section (fig. 1) they form a well-marked line across the lens 

 from side to side somewhat nearer to the inner than the outer 

 surface. The whole lens has the appearance represented in 

 fig. 1, being thickest in the median line and thinning away 

 rapidly at each side where it joins the retina. 



Right in its very middle is present a large, more or less 

 globular mass of small spherical cells, deeply pigmented (fig. 1, 

 pig.), and lying directly in the optic axis. The presence of these 

 must of necessity interfere with the action of the organ as an 

 eye^ in fact, the whole structure is characterised by the presence 

 of a great amount of pigment deposited in every part. It is 

 this pigment in the lens which causes the eye seen through the 

 transparent cornea to appear like a black spot, and its presence, 

 which must be regarded as due to degeneracy in the tissues, 

 indicates that the organ is now in a rudimentary condition. 



Structure of Retina. — The rods line the cavity of the 

 vesicle and form a very definite layer, being deeply embedded 

 in pigment, which renders it difficult to distinguish their out- 

 lines. Processes pass from them, often accompanied by pig- 

 ment granules, into the extern al-ly ing 1 ayers . Asinftatteria 



