1919] Rhodes: Binary Fission in Collodictyon triciliatum Carter 251 



activity. It is usually concluded, on account of this, that the chromatin 

 is the substance upon which metabolism is dependent. Collodictyon 

 presents evidence bearing on this point. The macrokaryosome, con- 

 sisting of separated chromatin, appears wholly passive during the 

 prophase. The microkaryosome, on the other hand, consisting of 

 chromatin which organizes the skein, is the center of great activity. The 

 radius of this activity is bounded by the metabolic membrane. If this 

 activity be regarded as due to the entering into solution of peripheral 

 chromatin and related nuclear substance, which must pass into the 

 interior, the so-called membrane must be either merely a static atomic 

 equilibrium zone, through which outer and inner activities are counter- 

 balanced, or it must be a definite membrane organized by great pres- 

 sure from within and without, through which, by the process of 

 osmosis, the peripheral solution passes into the inner sphere of organ- 

 ization, where the pressure is relieved and less than on the outside, by 

 the condensation and precipitation of chromatin on the organizing 

 skein. The latter seems the more plausible interpretation. In this 

 light the generative chromatin is the kinetic factor, at least in mitosis 

 probably in protozoan metabolism. The free chromatin is non-active 

 and non-kinetic, acting in a purely passive way in the prophase. Since 

 no food is engulfed and all inclusions are extruded, nutritive pro- 

 cesses seem suspended in Collodictyon during mitosis. Oxidative 

 (katabolic) processes would naturally be at their height, and better 

 subject to analysis since they are here separate from the anabolic. 

 Since the chromatin of the macrokaryosome shows no kinetic 

 phenomena, chromatin as such may be eliminated as the center of 

 ' ' activation of oxygen. ' ' But since this oxidative katabolism is a part 

 of nuclear activity, it is possible that it may be performed by the 

 generative chromatin in Collodictyon, possibly in other protozoans; 

 while anabolic or constructive processes of intussusception may find 

 their center in chromatin. 



There seems little doubt that the metabolic membrane found in 

 Collodictyon is related in some way to the chromosome vesicles of the 

 Metazoa, especially the radiations from the karyosome in a proto- 

 karyon type of nucleus. By its unity and simplicity I judge it to be 

 more primitive. The chromosome vesicles fuse as mitosis progresses 

 in higher forms; in Collodictyon it begins as a unit and ends in 

 becoming practically continuous with the nuclear membrane. It 

 may not be too imaginative to regard the nuclear membrane itself, 

 with its peculiar phenomena of persistence or disappearance in mitosis. 



