Yasui.— On the Life-history of Salvinia natans. 473 
The uppermost cell of the young prothallium now divides into two 
cells by a more or less oblique cross-wall (Fig. 40), and the outer one of 
these is divided again by an oblique wall, forming an apical cell and an 
antheridium-mother-cell (Figs. 41--43). The inner cell is also divided trans- 
versely, giving rise to a sterile cell above and an antheridium-mother-cell 
below (Fig. 44). From each antheridium-mother-cell a small sterile cell or 
wall-cell is cut off by an oblique wall which extends from the side-wall to 
the lower transverse wall, and a larger cell, the central cell or sperm- 
grandmother-cell, is formed (Figs. 45-6). The antheridium is made up of 
a wall-cell and a central cell which later divides into four sperm-cells. A 
single spermatozoid is formed in each sperm-cell. Now the development 
of the male gametophyte, consisting of a root-cell, a prothallium-cell, an 
apical cell, and two antheridia which are separated by a sterile cell, is com- 
pleted (Figs. 47 - 53 )- 
In the dividing cell of the male prothallium, the number of chromo- 
somes has always been found to be eight. 
In his classical paper on Salvinia natans Pringsheim (’ 63 ) states that in 
a male prothallium a single antheridium with eight spermatozoids is formed. 
He gives a figure of the apical cell and two sperm-grandmother-cells, but 
he mentions neither the presence of the wall-cells nor the sterile cell. 
Arcangeli ( 76 ) takes the two antheridial cells for two antheridia. Prantl 
( 79 ) seems to be of the same opinion ; and he states : ‘ Ich glaube, die beiden 
vorderen Zellen ebenso gut als zwei Antheridia deuten zu konnen, deren jedes 
eine Gliederzelle des rudimentaren Prothalliums einnimmt.’ Campbell’s 
(’ 87 ) description of the mature male prothallium is as follows : ‘ Das ganze 
Antheridium (wenn wir den ganzen oberen Theil des Prothalliums als ein 
einziges Antheridium ansehen) ist jetzt aus fiinf oder sechs Zellen gebildet : 
zwei innern (Fig. 26, m), welche die Urmutterzellen der Spermatozoiden 
darstellen, einer Deckelzelle (d) und zwei oder drei anderen peripherischen 
Zellen (p).’ His ‘ peripherische Zellen’ correspond to the wall-cells, and 
are, according to him, two or three in number. However, when he found 
three wall-cells it is very likely, in my opinion, that he mistook the sterile 
cell for one of them (compare Campbell’s Fig. 26). According to Belajeff 
(’ 98 ) each male prothallium contains two antheridia which are separated 
from each other by a sterile cell. In regard to this sterile cell, Campbell 
(’ 05 ) states as follows : ‘ This cell, however, did not occur in the specimen 
studied by me, where the two groups of sperm-cells were usually in imme- 
diate contact (Fig. 233, e).’ In my material it was found that the sterile 
cell always separates the two groups of sperm-cells, and thus forms two 
antheridia in each prothallium instead of one, agreeing with the statement 
of Belajeff. 
When the sperm-cell is completely formed, a blepharoplast appears in 
its cytoplasm, and soon elongates towards the nucleus (Fig. 32). In the 
