48 THE EMBRYOLOGY OF THE EYE. 



onal folds are thrown out to form the cIHary 

 processes. 



The mesoblastic portion plays in the begin- 

 ning a more passive role in the development 

 of the iris and choroid. In Fig. 7 the rudi- 

 mentary cornea and the general mass of meso- 

 blastic tissue are seen to be entirely cellular. 

 In Fig. 8 the mesoblastic tissue next the 

 vesicle-wall is still cellular, more externally it 

 is beginning to be fibrous. In Fig. 9 the 

 fibrous layer is only separated from the 

 vesicle-wall by the capillaries of the rudi- 

 mentary choroid. The mesoblastic tissue of 

 the rudimentary iris at this stage forms a thick 

 cellular layer with many blood-vessels, some 

 of which are continuous posteriorly with the 

 choroidal vessels and anteriorly with the ves- 

 sels of the lens-sheath. This mesoblastic 

 cellular tissue later fills up the folds thrown 

 out in the epiblastic portion, and forms the 

 connective-tissue portion of the iris and ciliary 

 body. 



In Figs. II and 13 we see a wedge-shaped 



