of Pilularia globulifera , Z. 245 
in a very short time. The protoplasm at the top increases in 
volume, and begins to push out the inner spore-membranes, so 
that the upper part of the spore becomes decidedly more con- 
vex than at first (Plate XIII, Fig. 24). At the same time the 
nucleus becomes much more nearly globular, and the amount 
of chromatin is seen to be evidently greater, as well as to have 
become more evenly distributed (Plate XIII, Fig. 25). This 
stage was observed in sections made four-and-a-half hours 
after the spores were placed in water. At this time the 
appearance of the protoplasm in the upper part of the spore 
had also changed, having entirely lost the reticulated appear- 
ance which it has in the ungerminated spore. 
This stage is figured by Arcangeli 1 , who did not, however, 
recognise the true nature of the nucleus, supposing it to be 
the beginning of the oosphere. 
The youngest stage in which it was possible to demonstrate 
positively the first division in the spore occurred sixteen-and- 
a-half hours from the commencement of germination. In 
this stage (Plate XIII, Figs. 26 <2, b ) the primary nucleus 
had completely divided, and a transverse wall, a, had formed, 
cutting off the mass of protoplasm at the top of the spore 
from the rest of the spore. This wall does not always have 
the same form, being sometimes convex above, sometimes 
decidedly concave. The next wall to appear is nearly parallel 
with the first, and is completed within three or four hours from 
the time the first is formed (Fig. 27, b). A few cases were ob- 
served where this second wall did not seem to have been 
formed, so that the central cell of the archegonium was in direct 
contact with the first-formed wall, but this is exceptional. 
Next are formed two walls in the upper cell, nearly per- 
pendicular to the wall b, and meeting each other so as to 
enclose a nearly circular central cell. When seen from above 
(Plate XIII, Figs. 33, 34) these walls appear nearly semicircular 
and concentric with the periphery of the prothallium. The 
nearly circular central cell is the mother-cell of the archegonium. 
M. c., Plate VII, Fig. 2. 
