NUCLEAR OSMOSIS AS A FACTOR IN MITOSIS. 147 
supports the statement made above that the contractility of the fibrils is not the 
cause of the separation of the daughter chromosomes. 
In the stage represented in fig. 11 we see the two groups of daughter chromosomes 
lying at opposite ends of the cell, with a series of cytoplasmic threads stretching 
between them. My interpretation of these fibrils at the close of the anaphase is that 
they represent the same state of tension by the spindle in the metaphase and the 
radiating kinoplasm of the prophase—a tension caused in the first place by the 
diminution and final vanishing of the nuclear vacuole. 
The daughter chromosomes forming the two groups now agama more or less 
intimately united—a condition in which it is difficult to distinguish the individuals. 
With this massing together each chromosome loses its compact and homogeneous 
appearance by becoming vacuolated. This vacuolation of the daughter chromosomes 
was first described by the writer in the case of Passiflora and Equisetum (Lawson, 
1903), and was later confirmed by other writers (GRiGoIRE et WyGaERTs, 1903; 
YAMANOUCHI, 1906 and 1910; Gates, 1907). It would seem that this is a constant and 
normal occurrence in the organisation of daughter nuclei. YamaNnoucut (1910) regards 
this vacuolisation as either a secretion from the chromosomes or a dissolution of portions 
of them into liquid. In the light of the present researches I am inclined to regard the 
presence of these lacunze or vacuoles within the chromatin as due to the diffusion of 
endosmosis. In this connection I see no reason why the chromosomes should not still 
possess the plasmatic membrane with which they were enveloped in the later prophase 
(see p. 144 above). This vacuolisation proceeds until the membrane extends beyond 
the limits of the chromatin, as shown in fig. 12, and eventually each daughter nucleus 
consists mainly of a single large vacuole filled with karyolymph. As these two nuclear 
vacuoles increase in size there naturally follows a general relaxation of the tension set 
up in the cytoplasm at the prophase, and this relaxation is expressed in the loose curved 
appearance of the threads stretching between the daughter nuclei, as shown in fig. 13. 
GLADIOLUS. 
in contrast to the conditions found in Disporum, the spore mother-cells in Gladiolus 
are very large; and they have the additional interest of passing through a series of 
typical multipolar stages in the course of spindle formation, which has been described 
as occurring so frequently in the vascular plants. 
In fig. 14 we have represented a median section of a miscrospore mother-cell of the 
common garden species of Gladiolus. The large spherical nucleus occupies about half 
the volume of the cell-cavity. It is apparently at or near its maximum size, and, judging 
from its turgid appearance, it is evidently under high osmotic pressure. The chromo- 
somes appear as curved or bent rods many times longer than broad. A large globular 
nucleolus is also suspended in the karyolymph. The nuclear membrane stands out in 
sharp contrast as the inner limiting layer of cytoplasm against the clear nuclear sap. 
