KUPLOTES WORCESTERI: II. 319 



Metcalf describes the formation of chromatin spherules from the chromosomes 

 of Opalina in the course of each mitosis during tlie year, and suggests "that 

 these eliromatin spherules are nutritive — comparable to the granules of the macro- 

 nucleus of higher ciliata. Their formation and extrusion (in Opalina) is posi- 

 tively useful, being probably connected with nutrition and perhaps with the 

 formation of the refractive spherules of the endosarc." 



The cases of eliromatin elimination heretofore described do not compare 

 closely with the process occurring in Euplotes, since in this form there is 

 a complete solution of all the chromatin^ and not of a part onl_y. The 

 rapid and complete disappearance of affinity for stains from the region 

 affected indicates that the chemical nature of the chromatin is entirely 

 changed. Tlie possibility exists that a vegetative chromatin is removed 

 by osmosis during the stage of solution and that then the most active 

 .chromatin reassumes its original condition. However, it seems much 

 more probable that an interchange of materials between nucleus and 

 cytoplasm takes place which is of such a nature that the reconstructed 

 chromatin is essentially a new substance, not only relieved of the so- 

 called vegetative chromatin, but rejuvenated throughout by a physical 

 and chemical reconstitution. The more active condition of the chromatin 

 after the completion of this process is shown by its increased staining 

 power. 



It would seem that during tJic ordinary life and activities of the cell, 

 the chromatin either accumulates a certain amount of inert substance 

 which can play no part in the activities of division, and which it would 

 be useless, perliaps harmful, to carry over to the daughter cells ; or else 

 that a portion of the chromatin itself is so modified by its activities that 

 it loses some of the properties essential to its sharing in division, and 

 therefore is eliminated before or during that process. The latter view, 

 which is merely an expression of the fact that destructive metabolism 

 must occur in chromatin as in all other living substance appears most 

 reasonable. It also seems quite probable that these products of chromatin 

 metabolism may be so closely allied to the living substance of the cyto- 

 plasm as to be incorporated with it or, if considerably degenerated, to 

 serve as food for the cell. 



The reconstruction of chromatin by complete solution and reforma- 

 tion, such as occurs in Euplotes, is a process of a higher order, as regards 

 its effect on the nucleus, than that of the elimination of chromatin 

 spherules, as in Ojjalina. In the latter case, much of the chromatin 

 remaining may have been in the nucleus for a considerable time and ma}' 

 be practically senescent; in the fonner case the j)0ssibility exists that the 

 new chromatin may be entirely composed of new material derived from 

 the cytoplasm. As the cytoplasm itself is a constantly changing sub- 

 stance owing to its various katabolic and anabolic activities, an interest- 

 ing possibility that the new chromatin may be formed from materials 

 only recently entering the body is instantly suggested. 



