674 GARY N. CALKINS 



of the different portions is enigmatical and I have no sugges- 

 tions to offer in interpretation. While the majority of the 

 macronuclei are deeply staining, granular and uniform in tex- 

 ture, this one portion is much less granular, stains lightly and 

 is more homogeneous than the denser portions. In some cases, 

 furthermore, there is no such difference between the different 

 portions, hence it may be only a transient or even a degenerate 

 condition. Opposed to the latter hypothesis is the fact that 

 the same texture is noted in the new nuclei formed as a result 

 of conjugation. In one case this lighter portion was found at 

 the extremities of the elongated macronucleus in division, where 

 it appeared something like the centrosphere of Noctiluca in 

 division but in other division figures there was no such differen- 

 tiation. 



In division, the central portion of the elongated strand be- 

 comes thinner until it finally breaks in the middle. The daugh- 

 ter nuclei do not round out then into definite homogeneous 

 nuclei, but the reconstruction is accompanied by a fragmen- 

 tation of the macronuclear material into from two to eight sep- 

 arated fragments of diverse size. Some of these portions are 

 extremely small, and when rounded out, have the appearance 

 of micronuclei, but no two cells are alike in this respect, a fact 

 which, together with their mode of origin, contradicts any in- 

 terpretation as to their micronuclear nature. The chromatin 

 of the macronucleus is finely granular and has the tendency 

 to collect about the periphery of the elongated strand, leaving 

 the central portion lighter, thus giving the impression of an 

 intranuclear canal. In one case the cell was of giant size, with 

 a macronucleus in the reconstruction stage of division, although 

 there was no evidence of division of the cell body (fig. 2). 



The end stage of division is characterized by the peculiar 

 twisting movements observed in so many ciliates, the last con- 

 necting strand of cortical plasm finally giving way and freeing 

 the two cells, each now with its full complement of cellular 

 organs, peristome, nuclei, and contractile vacuoles. 



