54 THE EMBRYOLOGY OE THE EYE. 



nal prolongations of the inner stratum of 

 retinal cells just mentioned, may now be seen 

 to be continuous each with a nerve-fibre (Fig. 

 14). It is not possible to say whether the 

 nerve-fibres originate peripherically or cen- 

 trally, or whether they originate simultaneously 

 at both extremities. At the earliest period in 

 which I have found nerve-fibres they are ap- 

 parently equally developed in their entire 

 course. 



After the nerve-fibres appear, the vessels 

 soon develop. These spring from the vessels 

 in the nerve, and quickly spread over the en- 

 tire retina in the form of small capillaries lying 

 just beneath the limitans interna (Fig. 10 at 

 left). 



At this stage the differentiation of the retinal 

 cells becomes further advanced. The stratum 

 of cells next the limitans externa become 

 columnar with long oval nuclei which stain 

 deeply (Fig. 10). 



The mass of retinal cells have a round or 

 oval nucleus, staining moderately dark, and a 



