REGENERATION AND REGULATION IN PARAMECIUM CAUDATUM

Abstract

1. When the anterior end of the cell was removed by a transverse cut through the peristome just in front of the macronucleus, thirty-four per cent. of the fragments regenerated the lost end and divided normally. When the posterior end was removed by a similar cut, back of the mouth, sixty-two per cent. of the nucleated fragments regenerated the lost end and formed a normal race.2. Removal of the anterior end resulted in irregular division in fifty per cent. of the nucleated fragments, while removal of the posterior end caused irregular division in only twenty per cent. of the pieces.3. Paramecia cut in half transversely usually die as the nucleus is forced out by the pressure of the knife. When the nucleus remains in one of the halves regeneration is followed in that half by normal division.4. Monsters develop from fragments composed of more than half of the protoplasm of a normal Paramecium, but never develop when a cell is cut exactly in half.5. A fixed division plane is present in the normal cell as early as two and a half hours after fission. It is possible in vegetative cells, where fission has been delayed for a period, that more than one plane is laid down. This would account for the fact that after cutting off one end of the cell several divisions follow in quick succession.6. The power of regeneration varies in different races, and in different individuals of the same race. It is the index of the condition of the cytoplasm.7. The removal of a portion of the cytoplasm does not result in the production of smaller individuals. After several generations have been produced the normal size is regained.