118 Allow Burdette Stout 



In the spirem of the prophases the chromosomes are ellipsoidal or 

 spherical masses. Although held rather closely together in a series, the 

 outlines of each are clearly defined. There is no time when the sub- 

 stance of each is drawn out or when the chromosomes are merged to- 

 gether to make a dense homogeneous chromatic spirem. Such a spirem 

 as is here described and figured I shall call a discrete spirem. By 

 this term is here meant a serial alignment in which the individual chromo- 

 somes are clearly defined. At its most conspicuous stage this discrete 

 spirem appears as in figure 11. It is least in evidence in the stage shown 

 in figure 6. 



During the prophases the one or more nucleoles are still intact and 

 it is very clear that they do not break up into chromosomes or contribute 

 directly any chromatin substance for the growth of the chromosomes. 



The discrete spirem draws in toward the nucleole and may become 

 closely aggregated about it as is shown in figures 8 and 9. The chromo- 

 somes may thus become closely massed together, but their individuality 

 and their serial arrangement is maintained, as is evident from a study 

 of such a preparation as is represented in figure 9. Nuclei in this stage 

 are not so numerous as are those in the earlier or the later stages, but 

 the evidence is conclusive that this perinucleolar and centrally aggregated 

 condition of the spirem regularly follows the withdrawal of the spirem 

 from the periphery of the nucleus and precedes the equatorial plate. 



Early in the prophases the characteristic polar caps appear at oppo- 

 site sides of the nucleus in the position of the future poles of the spindle. 

 On the periphery of these as is shown in figures 5 & and 6 there is a felt 

 of fibres for the most part arranged concentrically. Later the colorless 

 area between this felt of fibres and the nuclear membrane is less sharply 

 defined and the fibres extend through it to the membrane. The fibres 

 are now more parallel and tend to lie in the axis of the future spindle. 

 Some of them appear to be in contact with the nuclear membrane. The 

 membrane breaks down first in such regions of contact and in doing so 

 appears to pass over into a fibrous material as is well shown in figures 8 

 and 11. Lawson's (1911b) conception that the nucleus is a vacuole whose 

 membrane during the prophases shrinks until it envelops the chromo- 

 somes finds no support from the phenomena in Carex aquatilis. 



The fibres of the cap continue to grow inward first through the cap 

 and then into the nuclear cavity. The successive stages of their deve- 

 lopment are shown in figures 6, 10, and 11. When the fibres first grow 

 into the nuclear cavity the spirem is somewhat looped or folded, the 

 loops extending in the direction of the long axis of the spindle (fig. 12). 



