144 NERVOUS SYSTEM OF VERTEBRATES. 



b 



FIG. 71. Histogenesis and structure of the retina. From Cajal. (Die Retina 

 der Wirbelthiere.) 



A, a section through the retina of a mouse embryo of 15 mm. a,b,c, neuro- 

 blasts; d,e, epithelial (Miillerian) cells; /, nucleus of rod cell. 



B, a section through the retina of a chick embryo of fourteen days, a, b, epi- 

 thelial cells; c, rod cell; d, deep granule; e,n, cone cells; m, bipolar cell; s,u, 

 amacrine cells. 



C, a section of the retina of a dog. a, cones; b, rods; c and e, bipolar cells 

 related respectively to rods and cones; /, giant bipolar cell; h, amacrine cell; 

 ;', centrifugal fiber; n, layer of ganglion cells. 



