1919] Rhodes: Binary Fission in Collodictyon tricilidtum Carter 229 



tripod, ring, or double crescent (pi. 11, figs. 39, 40, 41, 42, 44). I 

 found one difficulty of technique here hard to overcome. The 

 chromatin cloud is usually so dense that whenever this is sufficiently 

 destained to see the skein, this latter is rendered unfit for detailed 

 interpretation. 



In Phrynotettix (Wenrich, 1916, p. 112) plasmosomes may change 

 into polar granules of chromosomes and vice versa. 



One of the most puzzling problems that cytologists have to deal with is the 

 behavior and function of the so-called "plasmosomes" or "nucleoli." They 

 apparently exhibit such a varietv of reactions to methods of technique, and 

 exhibit such varying relationships to other structures in the cell, that it is 

 almost hopeless even to attempt to classify them. That they play some import- 

 ant role in the physiology of the cell, there is not the slightest doubt, but what 

 that role is, 'or what relation they bear to the question of chromosome-individu- 

 ality, are problems that are far from a solution at the present time. 



There is hardly a close analogy between Phrynotettix and Collo- 

 dictyon, but here they offer a most interesting comparison. The 

 terminal knobs of the segmenting skein of Collodictyon lend them- 

 selves to the interpretation that they are elements at least of the 

 chromosomes. In Phrynotettix the individuality of the chromosomes 

 is traced by similar chromatin masses which, however, are not all 

 terminal and several of which may enter into the composition of a 

 chromosome. 



The blepharoplast divides during the middle or final prophase. 

 The rhizoplasts thicken and evidently split soon after the kinetic 

 membrane begins to expand (pi. 11, fig. 40). The spindle is not 

 organized until after the spireme and skein are far advanced. The 

 cytoplasm immediately surrounding the nucleus may become darker, 

 due to the presence of a chromidial cloud from extruded chromatin. 

 The nuclear membrane persists. The protoplasmic vacuoles may or 

 may not be large. They are as normal as in the vegetative stages 

 and their variations are largely the result of food vacuoles extruded 

 at the beginning of division. If one so cares, the prophase may be 

 regarded as beginning with the unequal constriction of the karyosome. 

 I have separated these stages arbitrarily for advantages of analysis. 



METAPHASE 



The nucleus becomes filled with a perfect spindle, which lies at 

 right angles to both the major axis of the cell and to the sulcal axis, 

 usually on one side or the other of the sulcus. The chromosomes are 

 now seven or eight in number (pi. 12, fig. 50). There is a general 



