Further light on the conjugation of Paramecium

Abstract

These experiments were undertaken to test the variability after conjugation of Paramecium caudatum in respect to the power to conjugate. An individual immediately after separating from conjugation possesses a new fertilization micronucleus and the old macronucleus. The new micronucleus divides into two, these two into four, the four into eight. During these three divisions the old macronucleus goes to pieces and the fragments are gradually absorbed in the protoplasm. Four of the eight new nuclei then metamorphose into four macronuclei, and then for the first time after conjugation, the cell divides. The progeny have two macro- and two micronuclei each. These cells immediately divide again without further nuclear division, forming four cells, each with one macronucleus and one micronucleus. The normal condition of Paramecium is then attained. The problem to be solved by experiment was: Do these four cells give rise to progeny which vary in respect to the power to conjugate? In order to get as many chances as possible the products of the first three divisions of each of the four cells were kept isolated, thus giving eight lines of cells from each of the original four. These sets of eight, thirty-two in all, I shall speak of as the 1st, 2d, etc., quadrants. The thirty-two lines were kept isolated in vials and fed at intervals of from six to eight days under conditions prohibitive of conjugation, from the 27th of last July to the present. From the outset marked differences in the size of the progeny of different lines were noted; the statistical proof, however, is not yet ready for presentation. A marked difference in division rate was also noted; for example, the daily division rate of representative individuals of all the lines was carefully kept for a period of 30 days in October and November.