64 
PROFESSOR E. RAY LAXKESTER. 
division of the chlorophyll-corpuscle precedes and is invariably 
followed^ sooner or later, by the division of the protoplasm of 
the whole organism. 
At the same time it does not appear that there is any ground 
for regarding the green-coloured corpuscles of Archerina as 
ordinary cell-nuclei (or rather, one should say, Protozoon cell- 
nuclei) coloured green by chlorophyll. They have none of the 
distinctive characters of cell-nuclei as distinguished from 
chlorophyll-corpuscles. They do not exhibit any differentia- 
tion of chromatin substauce into fibrillae or loops at the period 
of division, and moreover they appear as a rule to divide not 
into two but into four. 
I am not sure that the complete division into two does not 
occur in the large individuals such as are drawn in figs. 7 and 
13 ; but it is quite certain that in some of these large forms 
(figs. 14 and 15), and in all the smaller phases of Archerina 
(figs. 20, 21, 22, 24), the dividing chlorophyll-corpuscle forms 
a tetrad. It is possible that the curious form presented by the 
chlorophyll-corpuscles in figs. 7 to 13 — when there is an 
appearance of two oval bodies which are joined by a superficial 
shell of green-coloured substance on one hemisphere of the 
organism — may be only preliminary to the breaking up of the 
chlorophyll-corpuscle into four, and may not really indicate, as 
it seems to do, a division into two. 
There are reasons for regarding these larger forms as excep- 
tional, inasmuch as they appear to have emerged but recently 
from the encysted condition (figs. 1, 2, 3, 4, 5, 6). When the 
Archerina has once fairly started on an active vegetative 
growth (as in the groups of smaller individuals) there is no 
doubt that the division of the chlorophyll-corpuscle usually 
and characteristically proceeds by the simultaneous fission 
of the corpuscle into four segments (fig. 25), and 
consequently produces groups of four daughter corpuscles (fig. 
21 ). 
In respect of this peculiar quadri-sectional division, the 
chlorophyll-corpuscle of the vegetating Archerina very closely 
resembles that of Hydra viridis, as may be seen by a 
