298 Phillips on a Comparative Study of the 
71), which divides the cell into two, always, however, leav- 
ing a small pore at or near the centre through which the 
protoplasm of one cell is connected with that of the next. 
These observations, therefore, seem to show that two 
methods of division occur in the Cyanophycee. In one of 
these the nucleus does not pass beyond the net or spireme 
stage, which constricts itself into two nearly, though not 
necessarily equal parts. In the other method we have a 
very evident primitive state of karyokinesis, but no longi- 
tudinal splitting of the chromosomes, such as has been held 
to be necessary to equally distribute the hereditary materials 
in the higher plant cells. Whether there is any sequence 
to the occurrence of these different methods of division, so 
that one form might appear at one time in the life-history 
of the plant and the other at another cannot yet be asserted. 
There is no reason why such should not occur, however, 
for the Cyanophycez are evidently of a much more com- 
plex organization than we have hitherto supposed. But the 
fact that the two forms of division appear, and that each 
starts upon the way to karyokinetic division, one stopping 
in the spireme stage while the other goes on to the forma- 
tion of a rudimentary spindle, is significant. The fact that 
the division of chromatin is not always equal and never 
longitudinal or qualitative, seems to suggest that this pro- 
cess is not so essential to the division of the hereditary 
material as has been held in the past, but that it has rather 
been evolved as a convenient method of giving out to each 
daughter cell the quantitative, rather than the qualitative 
amount of chromatin which belongs to it. This is further 
suggested by the method of division, which does not pass 
beyond the net-spireme stage. It is not in any sense a 
fragmentation of the nucleus, since it is invariably followed 
by the formation of a division wall. This is laid down in 
the same way as in the cells which show typical karyokine- 
sis. It seems, therefore, that division in these forms is evolv- 
