SCIENTIFIC PROCEEDINGS. 
Abstracts of the Communications. 
Forty-second meeting 1 . 
Cornell University Medical College. February 15, iqii. 
29 (554) 
Cell Division and Cell Regeneration. I. Uronychia transfuga. 
By GARY N. CALKINS. 
[From the department of Zoology, Columbia University.] 
1 . Although many experimenters have studied the regenerative 
power of different kinds of protozoa no one has observed the 
variations in this power at different age periods after division. 
2. Uronychia transfuga is a marine hypotrichous ciliated pro- 
tozoon about lOOfx in length. It may be cut in any plane with a 
fine pointed scalpel and the pieces will live for several days, thus 
showing a hardiness which makes it a good subject for experi- 
mentation. 
Under conditions of culture in the laboratory (at Roscoff, 
France) the cell divides about once in 36 hours, the period between 
divisions being marked by definite changes in size of the cell and 
in arrangement of the nuclear elements (macronucleus and micro- 
nucleus) . 
3. Experiments to test the regenerative power were made upon 
cells immediately after division; on cells from 12 to 18 hours after 
division; on cells immediately before division; and on cells during 
division. The cells, in all cases, were cut with a scalpel under a 
microscope, full records of 75 experiments being kept. 
4. If cut immediately after division the fragments continue 
to live for at least three days, but that fragment alone regenerates 
which contains macronuclear material and the micronucleus. 
The other fragment contains a variable amount of macronuclear 
material but no micronucleus. In two of the thirteen successful 
experiments on cells in this stage, neither fragment regenerated. 
5i 
LIBRARY 
NEW YORK 
BOTANICAL 
GARDEN. 
5 
