II. The Cytology of the Gametophyte Generation. 199 
infrequent cases of polyspermy already referred to, could not be decided, 
as I have not yet seen the phenomenon in any of the control cultures. 
After a time the nuclei separate into two or more groups. As 
a general rule there is nothing more to be seen than a constriction of 
the kinoplasmic mass containing the nuclei, followed by the appearance 
of two groups instead of one ; these groups taking up the positions which 
in a normal segmentation would have been occupied by the two daughter- 
nuclei (Fig. 42). The plane of division of the cell becomes almost clear 
of chloroplasts, and after a time the dividing wall makes its appearance ; 
the early stage of this process is shown in Fig. 42. 
In a solitary instance nuclei were observed with connecting fibres 
between them (Fig. 38) ; these presented the additional peculiarity of 
being in the dispirem stage. Although it is very evident that the nuclei 
increase in number, the chromatin does not increase proportionately in 
amount. There is always a great difficulty in staining the nuclei, and 
in the later stages many of them are undistinguishable from cytoplasmic 
structures, excepting by their form. The multiplication of nuclei must 
be accomplished by direct division as, after the original multipolar figures, 
neither chromosomes, fibres, nor any other signs of mitosis are ever seen. 
Instead of first dividing into two cells each with its group of nuclei, 
the original cluster in rare cases separates into three or even four groups. 
The largest number of cells seen in a germling was six ; they were very- 
unequal in size, but every cell contained a cluster of nuclei. After a few 
divisions the germlings invariably died. It may be suggested that some 
of them may develop into mature plants in their natural habitats ; this is 
very unlikely, for the fertilized eggs in the same culture grow vigorously. 
General Considerations. 
A few general questions suggest themselves for consideration. At the 
present stage I do not intend to discuss them fully ; this will be done when 
the investigation of other Dictyotaceae has been completed. 
1. The Nucleolus. That this structure in all the cases discussed con- 
tains the bulk of the chromatin is fairly obvious. In most cases there 
is a quantity of substance which is not employed in building up the 
chromosomes. How is it that in unfertilized eggs the nucleolus breaks 
up directly into chromosomes, and how is it that no residual nucleolar 
substance is ever left over after the differentiation of the chromosomes? 
Can it be that in the mature egg the nucleolus has lost some of its 
capacity for metabolism, and that this can only be restored by the 
advent of the antherozoid ? 
2. The centrosome and radiations. It is clear from the foregoing 
description that, while the centrosome cannot be regarded as a mere 
condensation point at the focus of the system of radiations — its peculiar 
P 
