1 68 Campbell . — On the Development of 
that the development of the male prothallium has little 
in common with that of the true Filices, the figure of 
the prothallium of Azollei given \ bears a very striking 
resemblance to the simple male prothallium of many Poly- 
podiaceae, for instance. The small cell, cut off subsequently 
from the large basal one, as described by him, I failed to 
see in any of my sections. No indication of marked dorsi- 
ventrality, as he states, was noticed either. This may possibly 
have been due to slight shrinkage in imbedding, by which 
the central part of the prothallium was a good deal more 
constricted than it probably is in life. My own conclusion, 
reached after a careful study of a large number of prothallia, 
is that there is but a single vegetative cell formed (from 
which possibly later a small cell may be cut off), and that 
the rest of the prothallium forms at once a single terminal 
antheridium. 
The subsequent divisions, as observed by me, correspond 
essentially with those given by Belajeff. In the middle 
cell of the antheridium two nearly vertical walls are formed, and 
with the upper cell (Fig. 31 o) completely enclosing the central 
cell of the antheridium. The cell (o) recalls in form and 
position the opercular cell of the antheridium of the Poly- 
podiaceae, but apparently is formed here before the central 
cell is cut off. In one of the lateral cells a horizontal division 
is usually (perhaps always) formed, so that the central cell 
is surrounded by five parietal cells, one basal (b), one apical 
(0), and three lateral ones. The central cell now divides 
by an approximately vertical wall, and these cells divide 
twice by walls at right angles to each other, so that eight 
sperm-cells are formed. From the nucleus of each cell, in 
the usual way, the body of the spermatozoid is formed. I11 
some cases it looked as if only four sperm-cells were formed ; 
but this was not certain. The dehiscence of the antheridium 
and the free spermatozoids were not seen, but probably the 
latter resemble those of Salvinia. To judge from the ap- 
pearance in the nearly ripe antheridium, they do not possess 
2 loc. cit. Fig. 2. 
