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Plate I: Fig. 1 — Pachytene showing homozygous abnormal 10. Carmine smear. The proximal jjortion of 

 the extra chromatin is euchromatic as is a smaller distal piece. A large and conspicuous knob lies between 

 the two euchromatic portions. Fig. 2 — Metaphase I in microsporocyte homozygous for abnormal 10. 

 Carmine smear. The ten bivalents each have their true centric regions co-oriented on the spindle. The 

 onset of neo-centric activity is manifest in the second, sixth, and seventh bivalents from the right. The 

 third and fourth bivalents from the right are somewhat superimposed. Figs. 3 and 4 — .\naphase I in mi- 

 crosporocyte homozygous for abnormal 10. Carmine smear. Some of the dyads are undergoing a normal 

 anaphase separation while in others the neo-centric regions are pulling the ends poleward. Note that 

 the normal ap[)earing dyads are slower in their poleward migration. F'^ig. 4.2 is a drawing of Fig. 4 above. 



