888 



THE BABBIT. 



connected with the ventral surface or floor of the fore-brain 

 (Fig. 155). 



The optic cup. On the tenth day, the doubling up of the 

 optic vesicle to form the optic cup commences, and by the 

 fourteenth day (Fig. 155) it is completed. The process of 

 doubling up takes place in very much the same way as in the 



AO VJ 



Fie. 155. — A transverse section across the head of a Rabbit Embryo of the 

 fourteenth day, the section passing through the eyes, the fore-brain and 

 the cerebral hemispheres, x 14. 



AO, central artery of retina, arising fi-om internal carotid artery. BD, fold of tlie 

 inner waU of the cerebral liemisphere, wliicli forms tlie hippocampus major. BI, corpus 

 striatum. BS, lateral ventricle, or cavity of the cerebral hemisphere. BU, optic 

 thalamus. FM, foramen of Monro, leading from the third ventricle to the lateral 

 ventricle. OC, inner or retinal wall of optic cup. OB, outer or pigment wall of optic 

 cup. Oil, lens. OM, upper eyelid. OO, lower eyelid. VJ", jugular vein. X, fold 

 of the inner wall of the cerebral hemisphere, wliich forms the choroid plexus of the lateral 

 ventricle. XD, blood-Vessels of the choroid plexus. 



chick ; and, although occurring simultaneously with the forma- 

 tion of the lens, it is to be ascribed rather to a complicated mode 

 of growth on the part of the walls of the optic vesicle itself, 

 than to mechanical inpushing by the developing lens. 



A choroidal fissure is formed along the ventral surface of the 

 optic cup, as in the chick ; the only important point of difference 

 being that, in the rabbit embryo, the process of folding or 



