DEVELOPMENT OF THE EYE OF AMBLYOPSIS 



157 



THE EYE OF THE ADULT. 



The eyes of adult individuals from 25 to 75 mm. long were fully described in 

 a previous chapter, and the eyes of very old individuals were mentioned briefly. 

 The most highly developed eye found was that of an individual 75 mm. long. 

 This eye is much above the average in the development of its pigmented layer, 

 etc. Perhaps 25 mm. represents the stage at which the eye as a whole reaches its 

 maximum development. 



GROWTH OF THE EYE FROM TIME OF ITS APPEARANCE. 



The question of the rate and amount of growth of the eye from the time it 

 appears can best be answered by the following table of measurements of the eyes 

 of successive sizes of embryos. Attention should be called to the great varia- 

 bility of the size of the eye in any one stage or in successive stages of development. 



It is seen from this table that the eye reaches the full vertical and longitudinal 

 diameter of the adult when the embryo is only 2 mm. in length. Since the eye 

 does not make its appearance till the embryo has reached a length of 1.5 mm. 

 and the lens does not begin to develop until i mm. has been added to the length 

 attained by the embryo after the eye has reached its full size, that is, not until it 

 has reached a length of 2.5 mm., it is apparent that from the beginning the eye 

 is in longitudinal and vertical diameter equal to the full adult eye. 



Table of Measurements of the Eye from the Time of First Appearance to Maturity. 



[All measurements are given in micra, except lengths of embryos, which are in millimeters.] 



* The following gives the individual measurements of the eyes of the seven specimens whose average is here noted : 



