388 DEVELOPMENT OF ORGANS IN MAMMALIA. [CHAP. 



cavity of the vitreous humour (Fig. 128 acr). The sides 

 of the optic nerve subsequently bend over, and com- 

 pletely envelope this artery, which then gives off 



Fig. 128. 

 ri 



P^fi&^sMM/^^^>%^ 



of-n- 



m--^ 



.^m c 



Section through the Eye of a Rabbit Embryo of about 



Twelve Days. 



c. epithelium of cornea : I. lens ; mec. mesoblast growing in from 

 the side to form the cornea ; rt. retina ; a.c.r. arteria cen- 

 tralis retinse ; o/.n. optic nerve. 



The figure shews (1) the absence at this stage of mesoblast 

 between the lens and tlie epiblast ; the interval between the 

 two has however been made too great ; (2) the arteria centralis 

 retinse forming the vascular capsule of the lens and continuous 

 with vascular structures round the edges of the optic cup. 



