No. 477] HISTOGENESIS OE RETINA 633 



3. Only the row of ,o-erniinal nnclei has the power of division. 



4. There are three well defined periods of growth: xn the 

 period of cell multiplication, second to eiolith day; iln the period 

 of readjustment, eiohth to tenth dav; ir) die perio.l of final ditfer- 

 entiation, tenth day to end of incui.ation. 



:>. Tp to the end of the Hrst peri..d the retina grows from 

 within outward by the deposition of an additional row of luiclei 

 with each successive generation. 



6. After this, karyokinetie figures are found only at the mar- 

 gins. 



of any given retina arc reprcscntc.l all the different stagvs through 

 which it has passed; the nearer the margin, the yoimger the stage. 

 9. The ganglion-cell layer consists at first of three rows of 



10. These fall into line in the direction of the internal limiting 

 membrane so as eventually to form but one layer. 



11. In the inner nuclear layer ditlcrcntiation into horizontal 

 cells, fibers of MiT.ler, ami bij'x.Iar cells tako place pari i>a.s,sii 



arranged as one with the stretching out of the surface area. 



