2096 Phillips on a Comparative Study of the 
a multiplication of the number of granules upon the net. 
Thereafter two modes of division may occur, even in the 
same species. In the first method (Figs. 1 to 5, 16 to 20), 
the central body or nucleus does not get beyond the network 
stage. This network draws together along the equator 
of the cell (Fig. 3), the net becoming finer and denser. 
It then begins to constrict in the middle (Figs. 4, 7). The 
side walls grow inward, first as a delicate collar of micro- 
somata, gradually becoming stronger and deeper, until 
finally the network is constricted entirely, and the micro- 
somata harden into a division wall. In this mode of divi- 
sion, the nucleus becomes constricted in dumb-bell fashion. 
The halves are usually as nearly equal as can be determined 
by the microscope, but at times one will appear considerably 
larger than the other. Lauterborn (47b) has noted that the 
nucleus of Dinoflagellates divided in the spireme stage, 
though there the divisions and the spiremes were more 
typically mitotic than in the Cyanophycee. 
The other method of division is undoubtedly a primitive 
mode of karyokinesis. The network is the same as has 
just been described for the first method of division, but 
instead of constricting itself into two parts while in the net 
stage, the chromatin network resolves itself into a single 
coiled linin thread (Figs. 8, 68), or spireme, upon which the 
balls of chromatin are arranged one against the other like a 
string of beads. This spireme arranges itself along the 
longitudinal axis of the cell, and breaks up into segments of 
about equal length (Figs. 9, 69). These segments might be 
termed chromosomes, though they do not form a nuclear 
plate, but are arranged along the whole of the segment 
in the form of the original beads of chromatin that were 
found in the net and spireme. That these beads cannot 
be termed chromosomes is evidenced by the fact that they 
usually retain their identity until after the daughter chromo- 
somes are formed, each daughter chromosome being com- 
posed of several of them. The segments do not converge to 
