BRAIN REGENERATION IN AMBLYSTOMA 



205 



healed within the first twenty-four hours. Five days after the 

 operation a new wall had formed connecting the wall of the 

 right diencephalon with the wall of the left telencephalon. At 

 first this wall consists of a nari'ow band of new cells bridging 

 the interventricular foramen. As growth proceeds the narrow 



Fifl. 1 Transverse section of embryo five days after operation, hy which 

 the cerebral hemisphere was removed, leaving the nasal placode in place, .-^how- 

 inp: curtain of cells across the interventricular foramen. X 50. 



band of cells is drawn (nit into a thin plate, never more than two 

 or three cells thick, stretching across the foramen (figs. 1 and 3). 

 A careful inspection of a series of operated larvae makes it 

 (juite clear that the new tissue thus formed is derived from the 

 primary ependymal cells that line the neural tube. Figure 2 

 dra^^^l from a section of an operated larva of the second series 

 shows the origin of this new tissue from the margin of the dien- 



