1919] Rhodes: Binary Fission in Collodictyon triciliatum Carter 223 



but is not so evident with safranin; gentian-violet, orange G, or Mai- 

 lory's modified connective tissue stain. This area of cytoplasm is 

 not differential cytoplasm, for the interstitial material between or 

 bounding the protoplasmic vacuoles throughout the cytoplasm stain 

 thus deeply with all nuclear as well as plasma stains that I have tried. 

 It seems, therefore, to be merely the cytoplasm in which the nucleus 

 is suspended, being largely granular instead of vacuolar. This 

 denser cytoplasmic area just surrounding the nucleus is a condition 

 of the resting nucleus and not a mitotic phenomenon. 



The state of the microkaryosome is of help in determining the 

 progress of mitosis especially of the prophase; but the expanding of 

 the kinetic membrane is the best criterion of this. A chromatin halo 

 inside of the nucleus usually accompanies this. 



When division begins, or very soon thereafter, all undigested food 

 particles and other foreign bodies are extruded. There is no round- 

 ing up of the cell, the characteristic shape being retained throughout 

 mitosis. I have never seen pseudopodia or amoeboid protrusions from 

 the sulcal region in division stages. 



UNEQUAL CONSTRICTION OF THE KARYOSOME 



Preliminary to true mitosis, the karyosome usually elongates and 

 constricts into a dumb-bell shape with the knobs of unequal size. 

 These pull apart until connected only by a strand, which finally 

 breaks, accomplishing an unequal or differential division of the 

 karyosome (pi. 10, figs. 29, 30). The resulting large and small 

 daughter karyosomes are not equivalents either in size or behavior, 

 and by reason of their size I shall designate them macrokaryosomes 

 and microkaryosomes respectively (pi. 10, figs. 31, 32). 



During this preliminary unequal constriction of the karyosome, 

 I have been unable to detect any change in the blepharoplast, which 

 consists of two basal granules surrounded by granular archoplasm. 

 I have not seen anything resembling a splitting of the rhizoplast at 

 either end. The flagella are still four in number at this stage (pi. 10, 

 figs. 28-31, 34, 36). 



The macrokaryosome is homogeneous in appearance with all stains 

 used and contains no residual body. It may be regarded as consist- 

 ing of plastin impregnated with chromatin. Its behavior is passive. 

 It loses its surrounding hyaline area, and may round up or form a 

 crescentic mass around and outside of the kinetic membrane. It is 



