118 
Arlow Burdette Stout 
In the spirem of the prophases the chromosomes are ellipsoidal or 
sphcrical masses. Although held rather closely together in a series, the 
ontlines of eaeh 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 ahgnment in which the indindual 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. 
Düring 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 beconie 
closely aggregated about it as is shown in figiu'es 8 and 9. The chromo- 
somes may thus beconie closely massed together, but theh- indmduahty 
and theh' serial arrangement is maintained, as is evident from a study 
of such a preparation as is represented in figiue 9. ATiclei in this stage 
are not so numerous as ai'e those in the carlier or the later stages, but 
the evidence is conclusive that this perinucleolar and centrally aggregated 
condition of the spirem regularly foUows 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. 
Oll the periphery of these as is shown in figures 5 6 and 6 there is a feit 
of fibres for the most part an'anged concentrically. Later the colorless 
area between this feit of fibres and the nuclear membrane is less sharply 
defined and the fibres extend throiigh it to the membrane. The fibres 
are now more parallel and tend to lie in the axis of the futiu'e spindle, 
Sonie of tlieni 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 110 Support from the phenoniena 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. Wlieii 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), 
