244 University of California Publications in Zoology [Vol. 19 



mata; (b) simply the freeing of the karyosome of sufficient chromatin, 

 which may here be regarded as passive and inert, to permit of un- 

 retarded kinetic activity on the part of the generative microkaryosome, 

 or (c) both. The second line of evidence points toward a separation 

 of the chromatin preliminary to a reorganization and growth of the 

 same. It is necessary for the peripheral chromatin as well as that 

 in the macrokaryosome to pass through solution, usually through the 

 stage of a chromidial cloud as well, before entering into the prophase 

 skein and the metaphase chromosomes whose organization takes place 

 within the metabolic membrane. The chromatin upon the equatorial 

 plate is much greater in amount than the mass of the original micro- 

 karyosome. Growth and organization have, therefore, definitely taken 

 place. Subsequently, growth proceeds much more rapidly in the 

 anaphase, during which time each daughter nucleus comes to contain 

 almost if not fully as much chromatin as the original nucleus (pi. 12, 

 figs. 52-55 ) . This would indicate that cell division was not initiated 

 by an unbalanced ratio and that the chromatin-cytoplasmic equilibrium 

 may be simply a metabolic phenomenon, not at all related to initiating 

 cell division. It would point, however, to the necessity of freeing the 

 microkaryosome to insure its better kinetic activity and that a dividing 

 nucleus seeks to be unretarded by surplus chromatin when organizing 

 for division. CoUodictyon thus presents evidence which tends to 

 contradict the nucleo-cytoplasmic ratio theory. 



The problem of dual chromatin is especially inviting. There are 

 two types of chromatin in CoUodictyon, differing clearly and unmis- 

 takably in behavior. Repeated efforts to get a differential stain for 

 the macrokaryosome and microkaryosome, however, have not succeeded, 

 and we have no evidence whatever of any chemical or physical differ- 

 ence between the chromatin of these structures. Observations upon 

 the microkaryosome lead me to interpret that body as consisting of the 

 generative chromatin. In its function at least, this chromatin is 

 different from that of the separated macrokaryosome, which is both 

 physiologically and morphologically passive. It required little specu- 

 lation to conceive, in fact it is perhaps probable, that with differentia- 

 tion in functioning, the chemical nature of the chromatin might be 

 sufficiently altered by purely metabolic changes to produce differential 

 staining of the two bodies. That such a differential staining has not 

 been achieved, points emphatically to the fundamental similarity and 

 chemical nature of all the chromatin of CoUodictyon. CoUodictyon 

 seems to present an example among flagellates of trophochromatin and 





