882 DEVELOPMENT AND STRUCTURE OF PINEAL EYE IN LACERTILIA, 



thrown into folds lined by loose connective tissue (which will 

 become the cutis vera). The embryonic connective tissue which is 

 to form this time skin, is arranged in a dense layer below the 

 columnar cells of the rete mucosum. 



The connective tissue surrounding the eye runs for the most 

 part parallel to the long axis of the head of the lizard ; it thus 

 meets the ends of the eye and forms a kind of suspensory band, 

 by wjiich the eye is firmly supported (fig. 12, Ct. B.) The pigment 

 of the skin has been developed at this stage, and runs in a broad 

 band to the ends of the eye, where it dips down and runs 

 beneath it {Ct. Pig.), no pigment being develoi»ed, however, 

 between the lens and the epidermis. 



Shape of the Eye. — The eye whether seen in longitudinal 

 vertical, or vertical transverse section has much the same appear- 

 ance. It is dorso-ventrally compressed, its long axis being 

 parallel to the long axis of the head. In section it has the 

 appearance of a small double-convex body placed in the con- 

 ca\ity of a larger concavo-convex one. The smaller boJy is 

 the lens, the larger the retina (fig. 12). 



Lens. — The lens is double-convex, the convexity on the internal 

 (inferior) aspect being much greater than on the external (superior), 

 so much so that the latter looks flat by comparison. The lens is 

 thickest at its optic axis, and from here it slopes rapidly away on 

 its internal surface, so that on reaching the retina it has diminished 

 to nearly one-half the thickness. 



Histology. — The lens is similar in structure to the lens in the 

 former stages, except that it seems to be composed of more layers 

 of columnar cells, or else the columnar cells have elongated, espe- 

 cially in the region of the optic axis. 



Retina. —The retina is now marked by the deposition of pig- 

 ment granules. The pigment, however, is deposited only in certain 

 regions as yet — viz., in (1) the lower ends of the rods (fig. 12, 

 R. Pig.), (2) the line of spherical elements {N') and (3) in the lowest 



