SCIENTIFIC PROCEEDINGS. 



Abstracts of Communications. 



Fifty-second meeting. 



Physiological Laboratory, College of Physicians and Surgeons, 

 February 19, 1913. President Ewing in the chair. 



46 (742) 



Further light on the conjugation of Paramecium. 

 By Gary N. Calkins. 



[From the Department of Zoology, Columbia University.] 



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 gradu- 

 ally 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 con- 

 dition 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 conjuga- 



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