EFFECTS PRODUCED BY CUTTING PARAMECIUM CELLS

1. Paramecium caudatum may be easily cut with a scalpel, one, the larger, part, continues to live in about 30 per cent. of cases, and both parts never for more than 24 hours. If the nucleus is injured by the knife neither part lives for more than a few hours. The present paper is a summary of about 150 recorded experiments.2. Cells cut at either extremity are just as much demoralized as those cut in apparently more vital parts.3. The power of regeneration varies in different races of "giant" Paramecium. In one race only about 1 per cent. regenerated; in another race about 10 per cent., in a third race about 30 per cent. regenerated, and in a fourth race all, or 100 per cent. regenerated. This last race is not included in the present paper.4. There is strong evidence of a division zone in Paramecium which lies in the center of the cell. If the cell is cut anterior or posterior to this zone the fragment divides in the original plane into a truncated abnormal form and a normal form. The truncated form may di...