Hatai, Cerebral Cortex. 2or 



sends a process towards the ventricle, and this process, sooner 

 or later, rotates half way at or near the ventricular layer (the 

 second layer of the present paper). 



The cells in the third layer, as well as the layers above it 

 show a distinct outline of the cell-body and the characteristic 

 structure of the various elements can here be seen. In this 

 layer, the cell-bodies of both spongioblast and neuroblast are 

 sparsely distributed as Figs, i and 2 show. Figure 2 shows 

 this layer under a high magnification. The neuroblasts and 

 spongioblasts are readily distinguishable by their size and form. 

 The neuroblast (a) has a large nucleus and the outline of the 

 cell-body is very distinct, while the spongioblast (b) exhibits 

 a smaller nucleus as well as an indistinct cell outline. A most 

 important feature which can be seen in this figure is the definite 

 direction of the cell-process of the neuroblast. All the cell pro- 

 cesses turn towards the periphery or cortical surface. The cells 

 are strictly monopolar. The cytoplasn is hardly visible around 

 the nucleus except at the one point, where the processes come 

 out. The shape of the nucleus is variable, sometimes spherical 

 and sometimes oblong in form. In general, the nucleus tapers 

 towards the process. The process stains more deeply than the 

 surrounding structures; though in some cases, one can trace the 

 process to quite a distance, yet in most cases, it disappears 

 abruptly, owing, very probably, to a bending at the tip. 



In the fourth layer, the cell-bodies are crowded more dense- 

 ly than in the case of the third layer. Though one can see 

 somewhat similiar cells whose processes turn towards the peri- 

 phery, yet the majority of them show a quite different arrange- 

 ment as well as a more complex structure. This is shown clearly 

 in Fig. 3, which has been drawn from this layer under a high 

 power. In most cases, instead of being monopolar, the cell- 

 body has distinctly two processes from its two ends, thus show- 

 ing a bipolar structure. One process is exactly the same in 

 shape and size as well as staining reaction as the process de- 

 scribed for the cells of the third layer, while the other process 

 is extremely delicate and much shorter than the former. It 

 stains rather faintly. Curiously enough, in this layer the main 



