of Pihilaria globiiliferct, L. 239 
the resemblance between such a reduced fern-prothallium 
and that of Pilularia is evident at a glance. 
All the divisions in the central cell are by means of walls, 
there being no primordial cells formed as asserted by Han- 
stein 1 for Marsilia , and Arcangeli 2 for Pilularia . The first 
wall is nearly vertical, but generally more or less inclined, and 
divides the central cell into two nearly equal cells (PI. XIII, 
Fig. 5). This stage is reached at a temperature of about 
2o°C., in about ten hours from the time the spores are placed in 
water. Each of the two cells now divides by a wall at right 
angles to the first and also approximately vertical, so that the 
young antheridium at this stage, when seen from above, shows 
the central cell divided into four equal parts arranged like the 
quadrants of a circle (PL XIII, Fig. 6). Each cell next divides 
by a horizontal wall, so that there are two strata of cells, each 
composed of four similar cells. The position of the succeeding 
walls appears to vary more or less, but in general the next 
wall formed in each of the eight cells seems to be generally 
nearly parallel to its outer wall (PL XIII, Fig. 10 b\ thus dividing 
it into an inner and an outer cell. Each cell now divides once 
more, forming altogether thirty-two cells, the number of sperm- 
cells usually formed in the completed antheridium (PI. XIII, 
Fig. 11). The whole process of division occupies not far from 
thirty hours at a temperature of 18 0 to 20°C., but of course 
varies slightly in individual cases. The nuclei of the central 
cells color very intensely with haematoxylin, but those of the 
wall-cells of the antheridium are apparently very deficient in 
chromatin, to judge from the difficulty of demonstrating them 
satisfactorily. 
As already stated, it is an easy matter to free from the 
exosporium the full-grown male prothallium and antheridium 
by simply heating. The vegetative part of the prothallium (PI. 
XIII, Fig. 13) is separated by a firm wall. Above this lies the 
large basal cell of the antheridium, which like the vegetative 
1 Hanstein, Befruchtung und Entwicklung der Gattung Marsilia, in Pringsheim’s 
Jahrbiicher, iv. p. 197 . 
2 1. c., p. 339- 
