644 Lewis . — The Life History of Griffithsia Bornetiana. 
cells become smaller toward the apex of the filament, the number of nuclei 
becomes correspondingly less. A subterminal cell of average size contains 
about ioo nuclei; an exceptionally large subterminal cell may contain as 
many as 5 co nuclei. In the newly formed terminal cell the number is 
much less, varying from 12 or 15 to 50, or even 75. The terminal cells, 
however, like the other vegetative cells, are always multinucleate. 
The occurrence of multinucleate cells is rather general in the older 
portions of the thallus of other Florideae, while the terminal cell is usually 
uninucleate (Davis, 22 ; Oltmanns, 59 , ii, p. 89). Schmitz, who first called 
attention to this fact ( 67 ), showed also that in the different species of a 
single genus the number of nuclei in the cells varies greatly. For example, 
in the genus Callithamnion , all the cells in the thallus of C. plumula are 
uninucleate ; in C. corymbosum the older cells are multinucleate ; in 
C. Borreri even the youngest cells have two or more nuclei. Obviously, 
then, the number of nuclei in the cell is no index of relationship in the 
red algae. 
The nuclei of Griffithsia Bornetiana are pretty uniformly distributed 
through the cytoplasm. While the distance separating them varies 
somewhat with the age and condition of the cell, usually it is 35-30 /x. Not 
infrequently several nuclei, with the cytoplasm immediately surrounding 
them, form small clumps which project into the central vacuole (Fig. 7). In 
the cytoplasmic pad on the cross- wall 10-15 nuclei usually form a ring 
around the intercellular pore (Fig. 8). 
The size of the nuclei varies considerably with the age of the cells, as 
has been shown by Berthold to be the case in the coenocytes of Codium (6). 
In the young cells the resting nucleus is, on an average, about 4^ in 
diameter just before nuclear division and less than half that just after 
mitosis. In the older cells the average diameter of the nucleus is 2-3 
In the young sporelings the nuclei are very small, measuring 1-2 //. in 
diameter. 
The resting nucleus is nearly spherical or somewhat flattened against 
the cell-wall. It shows a large, densely staining chromatin-nucleolus in the 
centre. The size of the nucleolus varies from one-fifth to two-thirds the 
diameter of the nucleus. It is smallest at the time of complete rest of 
the nucleus, and grows larger as the time for mitosis draws near. Around 
the periphery of the nucleus a faint linin network is visible. This is con- 
nected with the nucleolus by faint radiating strands (Fig. 10). Immediately 
enveloping each nucleus is a zone of cytoplasm, which appears denser than 
the cytoplasm elsewhere, and which is probably to be considered of kino- 
plasmic nature. The thickness of this zone is quite variable. It often 
becomes about one-third the diameter of the nucleus. 
Nuclear division occurs regularly by mitosis, being found most frequently 
in the terminal cell. It occurs also commonly in the subterminal cell, less 
