200 Journal of Comparative Neurology. 



Von Bechterew's observations were confirmed and ex- 

 tended by Paton in 1901, who has studied the early develop- 

 mental history of the cortical layers in the foetal pig, though he 

 did not demonstrate the structure of the process in order to ex- 

 plain it as a dendritic outgrowth. He considers, however, the 

 supposed axone of previous observers as nothing more or less 

 than a process of a spongioblast upon which the ganglion cell 

 lies. For this reason, he decides against the axone as follows: 

 "I do not believe that at this period the neuroblasts have any 

 basal process or axone," .... "there is in my opinion con- 

 clusive proof that the dendrites are the first processes of the 

 cerebral ganglion cells to develop." 



The present writer arrived at the same conclusion from the 

 study of the developing neurones of the cerebral cortex of 

 foetal cats. The observations were made on the same prepara- 

 tions which had been used for a previous investigation on the 

 mitosis ('01) in the nerve cells; besides this foetal rats and pigs 

 were used for comparison. The present paper deals only with 

 the observations mentioned above, and further studies on the 

 histogenesis of the cortex will appear later on. 



Figure i was taken from the cross section of the cerebral 

 cortex near the middle of the hemisphere of a foetal cat. For 

 convenience, it is divided into six layers emunerated from the 

 ventricle towards the periphery. 



The first layer is composed entirely of primitive ectodermal 

 cells which present a somewhat cylindrical shape. Among 

 these spherical cells, or "germ-cells", are noticeable here and 

 there. 



The second layer is composed of spherical or oblong cells. 

 Numerous mitotic figures are noticeable in this layer. In this 

 second layer the outline of the cell-body is hard to demonstrate, 

 especially in the cells which lie nearer the first layer. On the 

 other hand the cells which lie near the third layer show a fairly 

 distinct outline of the cell-body. This becomes clearer as we 

 pass further and further away from the ventricles into the up- 

 per layers. The cell-bodies of the second layer are densely 

 crowded. According to some investigators the daughter cell 



