32 THE EMBRYOLOGY OF THE EYE, 



which later lose their nuclei and become zonula- 

 fibres, and his view is supported by the study 

 of two specimens showing congenital anom- 

 alies of the zonula. I cannot see, however, 

 how such an explanation could hold good for 

 the so-called orbiculo-ciliary and the inter- and 

 intra-ciliary fibres which are not inserted into 

 the lens-capsule. 



4. Crystalline lens, — In Fig. i the primary 

 vesicle A is in apposition with the external 

 epiblast. In Fig. 2 the external epiblast has 

 become thickened. This section is somewhat 

 excentric and does not show the cupping, which 

 is clearly seen in Fig. 3. According to the 

 later writers a similar cupping occurs in most 

 mammals. The opening shown in the cup in 

 Fig. 3 soon closes, so that the external epi- 

 blast again forms a continuous layer and 

 the cup becomes a closed sac. 



This junction of two folds with the union of 

 the outer and inner layers, and the entire 

 separation of the two layers from each other, 

 is the same process that occurs in the first 



