xNo. 477] 



HISTOGENESIS OF RETINA 



unstaining vesicle appears at the tip or outer segm 

 in the same size and shape during the remainder 

 ment of the rod. There is no evidence that it is o 

 in the chick, although Cameron descrihes it as su 

 The cytoplasm between this vesicle and the rod ini 

 elongates as development proceeds l)iit without 

 increase in anioinit since at the same time the dianu 

 and cventiiallv a conical cap of protoplasm develo| 

 end so that the unstaming vesicle appears like a fli 

 olc unl)C(ldc(l m the rod about a foin'th the way fr 



An interesting statement in this comiection is 

 nard, and repeated in more elaborate form by 



