250 University of California Publications in Zoology [VOL. 19 



Hartmann (1910) in his new group Binucleata adopted the con- 

 ception of an extranuclear division center located in the blepharoplast. 

 This seems to hold good for many polymastigotes. There is always 

 present a paradesmose, which is probably comparable to the centrodes- 

 mose of rhizopods or the "Binnenkorper" of free-living flagellates. 



KINETIC MEMBRANE 



The phenomenon of a membrane organizing around the micro- 

 karyosome, commensurate with the inner boundary of the hyaline 

 area, and expanding progressively during the prophase until it 

 approaches and becomes identified, identical except for the part where 

 the macrokaryosome rests, with the nuclear membrane, as is found in 

 Collodictyon, so far as I know, has been recorded in no other instance. 

 Achromatic radiations from the karyosome through the surrounding 

 hyaline area are found in the nuclei of some amoebas (usually de- 

 scribed as characteristic of protokaryon type of nucleus). These have 

 been interpreted as being related more or less closely to chromosome 

 formation. Sutton (1900) discovered what he designated "chromo- 

 some vesicles, ' ' surrounding the organizing chromosomes in an orthop- 

 teran insect. Carothers (1915) finds the same in the nuclei of Culex 

 and modifies the term to "chromomere vesicle." Wenrich (1916) 

 interprets these vesicles as expanded granules. 



In Collodictyon the nuclear membrane is not one of the most 

 evident features of the resting nucleus, but undoubtedly it is both 

 present and persistent. With the separation of the microkaryosome 

 and the beginning of organization, a second membrane, very faint but 

 evident, is formed immediately around the microkaryosome, and pro- 

 gressively expands. Just around this membrane is a progressively 

 expanding hyaline area, and ' inside is a more or less homogeneous 

 clouded area filling up the entire intramembranous space, in which 

 can also be distinguished the organizing microkaryosome, segmented 

 skein and spireme. No such membrane surrounds the macrokaryosome 

 and there is no evidence that any kinetic activity is present in or 

 around this mass of inert chromatin. 



R. S. Lillie (1902, p. 420) in discussing the oxidative processes of 

 the cell-nucleus, concludes that "in many tissues the nucleus is the 

 chief agency in the intracellular activation of oxygen . . . The active 

 or atomic oxygen is in general most abundantly freed at the surface 

 of contact between nucleus and cytoplasm." The nucleus in much 

 recent literature is regarded as the kinetic or metabolic center of cell 



