Fig. 1. (a) T5 (Ma^niiHt-atioii x 48,000) (Courtesy of E. Ivelleuberger); (b) T2 (May- 

 iiification •; 31.500) (Courtesy of E. Kellenberger); (e) T3 ( Magiiificatioii •; (>3,000) 

 (Courtesy of K. Williain.s). 



