ELECTRON MICROSCOPY 



Iji 



mv 



Fig. 7. Detail of Fig. 1 showing the top part of a brush cell with its numerous and 

 slender microvilli (mv). Three cilia (ci) are seen, possibly indicating that the brush 

 cell is being transformed into a ciliated cell. Mitochondria (m) are more abundant 

 than in ordinary ciliated cells, and particularly evident is the large number of quite 

 small mitochondria and small vesicular structures in between. The arrow points to 

 a dense structure with a light center which is reminiscent of a cross sectioned basal 

 body. A developing cilium? The dense line beneath the microvilli, the terminal web 

 (tw), is present only in relation to the microvilli. Magnification 17,500X 



122 



