Plate XII. Electron micrographs of some centrioles and 

 basal bodies. 



{a) A pair of centrioles from a human lymphosarcoma cell. 

 The centrioles are cut in longitudinal (above) and transverse 

 section, and lie in a characteristic position with their axes at 

 right angles. Note the triplets of fibrils seen in the transverse 

 section, and compare their arrangement and interconnexions 

 with those seen in Plates I and XI I la. Micrograph by 

 Bernhard. :: 145,000. 



(b) A stage in the duplication of a centriole of a Viviparus 

 spermatocyte. The parent centriole is shown in transverse 

 section, and the short procentriole is seen in longitudinal section 

 growing at right angles to its parent. From Gall (1961). 



X 145,000. 



(c) Longitudinal section through the basal part of a flagellum 

 of Blastocrithidia faniiliaris. The basal region of the flagellar 

 shaft lies in a reservoir at the anterior end of the flagellate. It 

 appears from some transverse sections that there may be a 

 complex transition zone between the shaft and the basal body; 

 this probably extends from near the proximal end of the central 

 fibrils through the part with the less dense centre to the basal 

 body proper, w^hich contains fibril triplets and a cartwheel 

 structure of hub and spokes. To the right of the basal body 

 is seen a short daughter basal body orientated at right angles 

 to its parent. : 56,000. 



{d) Longitudinal section of a basal body of B. familiaris with 

 a developing daughter basal body. The structure of the 

 transition zone of the flagellar base is again seen. The daughter 

 basal body has increased in length, compared with that in (r), 

 and has turned to lie parallel to its parent. x 38,000. 



Micrographs (c) and {d) by Vickerman. 



