EXPLANATION OF PLATES 



Figures 6-12, 14, 16-19, 22, and 25 are drawn from material killed in Schau- 

 dinn's fluid and stained in 0.1 per cent Bordeaux red preceding iron-alum 

 iaematoxylin. Magnification X 2100 (except fig. 2). 



PLATE 40 



Fig. 1. Camera lueida sketch of unstained flagellate, showing longitudinal 

 striations, plastids, gullet, and flagellum. 



Fig. 2. Diagrammatic enlargement of a camera lucida sketch. Note increase 

 in number of striations with the preparation for binary fission. 



Fig. 3. Posterior end of flagellate showing fourteen striations converging to 

 a point. 



Fig. 4. Anterior end; striations extend to edge of cytostome. 



Fig. 5. Optical section through posterior end ; the striations appear to be 

 elevated ridges in the pellicle. 



Fig. 6. Unstained flagellate, showing plastids at both anterior and posterior 

 ends. 



Fig. 7. Resting nucleus, showing aggregation of chromatin particles as the 

 prophase approaches. 



Fig. 8. Very early prophase; chromatin in form of flne threasls irregularly 

 coiled around the endosome. The ends of several threads can be seen. 



Fig. 9. Nucleus in prophase ; chromosomes show radial grouping around 

 endosome. Flagellum, blepharoplast, and rhizoplast are also shown. 



Fig. 10. Surface view of nucleus at about same stage as that shown in figure 9. 

 Note appearance of two blepharoplasts; only one rhizoplast could be traced. 



Fig. 11. Nucleus shows thicker chromosomes of later prophase. 



Fig. 12. Note the two blepharoplasts and rhizoplasts and the apparent split- 

 ting of the proximal part of the flagellum; this probably represents the beginning 

 of outgrowth of the new flagellum. Chromosomes are still radially arranged, but 

 appear to have increased in number with the beginning of metaphase splitting. 



Fig. 13. Later stage than figure 12. Nucleus shown in end view at about same 

 stage shown in figures 14 and 15. Several V-shaped chromosome structures are 

 seen. 



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