2()() 



H. SAXTON liVlUi 



('(>))lial()ii. It is ('()inj)()S('(l (Mitirclx' of tlic ty])ic;il colutuiiai' 

 cells thai make u]) the opeiulyiiui. As j»;r()vvth ])r()ceeds the 

 cells of the lunv nieiiil)nine lose their coluiiniar shape and be- 

 come metainor])hose(l into flattened quadrilateral cells. In the 

 three months old larva, a section of whose brain is shown in 

 figure 3, it is evident that this metamorphosis is accompanied 

 by a thinning of the tissue so that at this time the membrane is 



Fig 

 the same operation „ 

 diencephalon. X 50. 



'U^-^ ^ ^^ 



Portion of the regenerated curtain of an embryo seven days aiier 

 in figure 1, showing regeneration from the margin of the 



after 



composed of only a single layer of cells whose somewhat elon- 

 gated nuclei are parallel to the surface. 



It is evident from the above that the regenerated portion is 

 not made up of nerve cells but rather of the primitive germinal 

 epithelium which lines the neural tube, the only regeneration 

 that takes place being that necessary to close the wound made 

 by the removal of the hemisphere. We have then, forming as 

 a result of the operation, a curtain of primary ependyma across 

 the interventricular foramen. This is not nervous and hence 

 constitutes no true regeneration of the telencephalon. 



