290 



JAMES ROLLIN SLONAKER 



and fovea centralis, is observed at the optical axis. It appears 

 as a local thickening of the chorioid at the axis, and is distinct 

 from its general increase in thickness over the back of the eye. 

 This increase is due to a greater number of blood-vessels. (See 

 development of the fovea.) The formative cells of the scleral 



TABLE 3 



Showing the thickness of the different layers of the cornea, and the chorioid and 

 sclerotic coats in the developing and the adult eyes. Also the axial and equatorial 

 diameters of the whole eye at the same ages. 2 to 12 represent the ages in days 

 of the embryos used; H-2, H-4 and H-fl, represent, respectively, hatched two days, 

 four days, and just flying. All measurements were made in millimeters and 

 as nearly at right angles to the surface as possible 



plates appear more dense. The chorioid coat is still without 

 pigment. 



Two days after hatching (figs. 82 and 83) pigmentation of the 

 chorioid has begun, more prominently near the lens than at the 

 back of the eye. In this respect it corresponds to the pigmenta- 

 tion of the pigment layer of the retina which begins in the region 

 of the lens at a much earher age (see development of the retina) . 



