POLYTOMELLA CITRI, SP. NOV. 



219 



more and an indication of a spindle appears the chromatin knots 

 on the spireme have been reduced in number to nine and have 

 increased considerably in size. It cannot be said whether this 

 results from the side to side pairing of the eighteen earlier granules 

 or the contraction of alternate connecting strands as evidence was 

 found for both. The achromatic connections still exist between 

 these, the definitive chromosomes. The spireme is now near the 

 equator of the spindle, and in all later stages the strands between 

 the chromosomes have disappeared. The last figure which can 

 be classed as prophase shows the chromosomes lining up on the 

 equator to form a horse shoe around the spindle. The chromo- 

 somes which are first freed from each other by the disappearance 

 of the strands are considerably longer than they are broad. The 

 length is quickly reduced, so that when they split at the meta- 

 phase the two daughter chromosomes resemble two balls that are 

 in contact. Several very clear polar views of the metaphase were 

 found which indicated the number of chromosomes to be nine. 

 These are arranged in the horseshoe-shape which was noted in side 

 view. 



As noted above a centriole could not be demonstrated in the 

 resting cell. With the elongation of the nucleus and formation of 

 the spindle in the late prophase a granule appears at the poles of 

 the spindle (Figs. 13-15). On the anterior side of the nucleus a 

 line connecting the poles is seen on the nuclear membrane. This, 

 which we shall tentatively term a paradesmose, becomes much 

 more striking in the later stages. Hesitancy in definitely naming 

 this structure is due not to doubt concerning its occurrence, but 

 to the inconclusive demonstrations of a constant centriole, which, 

 presumably, would give rise to the paradesmose. 



With the progress of the chromosomes towards the poles the 

 spindle widens to equal the diameter of the horse shoe of chro- 

 matin until the band has traversed two thirds of the distance to 

 the poles. Some of the chromosomes now advance ahead of the 

 rest, which show a tendency to clump together. At the same 

 time the nuclear membrane is beginning to constrict at the 

 equator. A little later the dividing nucleus is drawn out into a 

 cylinder with pointed ends, and the chromosomes are clumped 

 into several masses at the ends of the slender cylinder. With the 



IS 



