402 BOTANICAL GAZETTE [JUNE 
nuclear division, at the middle of the cell at the point where the 
old nucleus lay, and cuts across the cell at right angles to its long 
axis. It is only after the complete isolation of the two halves of 
the old cell that the new ends of:each Closterium grow out again 
to restore the symmetry of the chromatophore and cell outline in 
each individual. In each new end there lies a dense accumulation 
of cytoplasm, and in this is the daughter nucleus. FISCHER saw 
that immediately after nuclear division the daughter nuclei move 
back from the position occupied by the mother nucleus. They 
migrate out at right angles to the long axis of the cell, and move 
back from the equator of the cell to their new position in the form- 
ing furrow of the chromatophore. FiscHER watched this process 
eight times in living specimens of C. Delpontii, and found that the 
migration is a very rapid one and may occur along either the convex 
or concave side. In C. Delpontii this migration had frequently 
been completed before the two cells had pulled apart, and in C. 
moniliferum the nucleus frequently came to rest in the furrow in the 
chromatophore before that body had been entirely divided, the 
latter part of the process seeming to be completed under its direc- 
tion. In the passage backward around the chromatophore the- 
nucleus seems to press that body to one side to make room for it to 
pass. The granular protoplasm that had gathered at the middle 
of the mother cell forms the tip of each new half, and apparently 
assists as Mo.t’s embryonic substance in the very rapid growth 
of the new membrane. This new half rounds out, the protoplasm 
streams into it, and the plant soon takes on a symmetrical shape. 
The new end vacuole appears in the granular tip, which even in the 
adult remains without chlorophyll. In C. Delpontii the entire 
process, beginning at ne icra ai was completed and the two 
halves had become ical in about five hours. FIscHER points 
out the further interesting fact that in the young Closterium the 
chromatophore in either end grows so that the two halves become 
pressed on each other, forming an apparent, but of course not real, 
fusion, as the two halves of the chromatophore remain separate 
throughout the life of the individual. He also noted that these 
observations on cell division give the reason for the conformity 
of the ridges of the chromatophore on either side of the nucleus. 
