524 



C. I'. Aricns Kappers 



<5^\ 















^^ 



é* 





"O 4t^'.^ 





''•*''', ^* ;.; 



' ,5^ 



Biondi (fig. l/j, 

 was able to demóns- 

 trate the controlate- 

 ral root-cells to pro- 

 ^ ceed from a migra- 

 ^ tion of homolateral 

 ^' neuroblasts through 

 ¿- the raphe ^. 

 5 This process, ac- 



;€ cording to Biondi., 

 '^ presents the follo- 

 "5 wing aspects: 

 •- At first, in the 4 



■y. ' ~ 



X. days chick embryo, 



c all neuroblaste are 



.= lying at a distance 



^ from the raphe (figu 



5 re 171. On the 6th 



5 day of incubation 



_¿ however, part of the 



'3 neuroblasts begin to 



= shift towards the ra- 



£. phe, passing through 



"P it to the other side. 



-z So, on the Jth day, 



:5 \ve may see in the 



•- raphe a current ot 



íjc root-cells, which has 

 I. 



"2 ' Bok made the 



> same observation, 

 '/^ though he could not 

 1^ ascribe the origin of 

 ^■f¡ all crossed root-fibres 

 — to a migration of cells, 

 some of them growing 

 out as crossinff axons 

 from controlateral neu- 

 roblasts. 



