540 NAOKI SUGITA 



lar, some having the apical process vertical, some oblique and 

 some in an inverted direction (Hatai '02). This arrangement 

 indicates possibly that this sublayer serves as a secondary sta- 

 tion for the migrating neuroblasts, where immature cells in part 

 mature and orient themselves, though most of them must have 

 finished their rotation while passing through the transitional 

 layers. But we cannot regard this sublayer as purely temporary, 

 for it remains all through life persisting as a special thin layer 

 containing large, polymorphous, deeply-staining cells, that is 

 the ental sublayer of the lam. mult. However, in this earlier 

 phase it contains transitional elements, since the number of 

 cells is greater here in younger than in the older brains, so 

 that in the newborn we see even seven or more rows of cells in 

 this sublayer, while in the adult only three or four rows appear. 

 The ectal sublayer of the lam. mult, has already in it polymor- 

 phous cells destined to become ganglion cells. These are round, 

 somewhat larger than the pyramids in the lam. pyr., their apical 

 processes all directed ectad. In this layer a relatively large 

 number of small, round cells, probably future glia cells, are also 

 to be seen, while we do not see as yet cells of this type in the 

 more ectal layers. 



In the newborn brain, there are one or in some earlier born, two 

 transitional layers between the lam. mult, and the ventricular 

 wall. At the earlier stage before birth there are always two such 

 layers (fig. 8, Tr.), afterwards but one, the ental layer having 

 disappeared. At birth, the wall of the ventricles consists of 

 germinal and indifferent cells, among which are many mitotic 

 figures. The thick layer of these crowded cells is the starting 

 place of the newly divided cells on their migration, during which 

 they rotate through 180° as they pass through the temporary 

 layers to their final station in the cortex. During the earlier 

 stages and when mitosis is most active (Allen '12), the neuro- 

 blasts are densely crowded both in the transitional layers and at 

 the cortex. The cells, crowded in the ventricular wall are small 

 in size, have deeply-staining nuclei and scanty protoplasm. 

 These cells poor in protoplasm form chains which fuse into a 



