﻿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.] 



Condition of embryo; living, 



or if preserved, 



direction of the sections. 



Alive 



KWve 



Alive 



Alive 



Alive 



Alive 



Alive 



Sagittal 



Transverse 



Horizontal 



Mounted entire 



Transverse 



Horizontal 



Sagittal 



Transverse 



Horizontal 



Sagittal 



Transverse .... 

 Mounted entire 

 Horizontal .... 

 Transverse .... 

 Horizontal .... 



Length of 

 embryos. 



1.6 



1.76 



2 



2-5 



2.8 



4 



5 



6 



6 



6 



6.5 to 7 



6.5 to 7 



9 t" 9-5 

 9 to 9.5 



9 to 9-5 



25 



2,S 



60 toicS 



Number of 

 embryos 

 measured. 



Longitu- 

 dinal 

 diameter. 



80 

 100 



135 

 190 

 170 

 2CO 



136 

 160 



108 

 108 

 114 

 120 



135 

 120 



192 



Vertical 

 diameter. 



15° 



134 



88 



70 



160 

 126 



106 



1 12 

 108 

 130 



160 

 IIS 



Axial diame- 

 ter from cor- 

 nea to oplic 

 nerve. 



Diameter. 



36 



48 



too 

 80 and 108 



99 



IIS 



88 



90 

 98 



109 



128 

 160 

 144 

 139 



16 to 48 



16 to 36 or none 

 18 to 50 or none 



Diameter 



of optic 



nerve. 



IS 

 17 



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



