382 Acton. — Studies on Nuclear Division in Desmids. I. 
The fact that the starch-sheath does not noticeably diminish in size 
during division of the nucleus, but only during division of the chromato- 
phore, suggests that the presence of a large quantity of starch in the cell is 
not in itself sufficient to induce division. The presence of two or more 
Illustrating successive stages in the division of the chromatophore and pyrenoid. 
pyrenoids in the cell is probably due to the fact that, although the conditions 
necessary for active starch-formation are present, the extra conditions 
necessary to induce nuclear division are absent, and additional pyrenoids are 
therefore formed to carry off the surplus starch. 
Botanical Laboratory, 
The University, 
Birmingham. 
DESCRIPTION OF PLATE VIII. 
Illustrating Miss Acton’s paper on Nuclear Division in Desmids. 
Fig. 1. End view of cell, showing chromatophore and pyrenoid. x 1,450. 
Fig. 2. Resting cell and nucleus, x 1,450. 
Figs. 3-5. Gradual disappearance of nucleolus and probable formation of spireme, x 1,450. 
Fig. 6. Appearance of chromosomes, x 2,000. 
Fig 7. Metaphase, x 2,000. 
Fig. 8. Anaphase, x 2,000. 
Figs. 9 and 10. Telophase, x 1,450. 
Fig. 11. Daughter nuclei beginning to migrate to the surface, x 1,450. 
Fig. 12. Nucleolus re-formed in the daughter nuclei. x 1,450. 
