114 W. J. Hodgetts. 
water. The “cap” frequently remains adherent to the gelatinous 
sheath of the cell atone spot, empty sheaths with the caps attached 
in this way being quite commonly observed (see Fig. 1, G); 
frequently, however, the “ cap ” is pushed right out of the sheath. 
The vesicle surrounding the swarm-spores gradually dissolves, the 
latter escaping one by one; they were never seen to swarm in the 
vesicle. The pyrenoid disappears prior to the formation of 
zoogonidia and is apparently formed de novo in the young plant, 
since pyrenoids could not be detected in the zoogonidia, although, 
according to Hieronymus 1 one or several “ pyrenoids ” are formed 
in each zoogonidium before liberation from the mother-cell. The 
liberation of the zoogonidia was always observed to take place in 
the early morning, and was quite easily seen by mounting Callitriclie 
leaves, etc., which were covered with the alga, in water and keeping 
the slide in a damp chamber to prevent evaporation; many 
individuals were usually seen to have dehisced and the zoogonidia 
more or less active in the surrounding water when the preparation 
was examined early the next morning. Formation of swarm-spores 
took place freely in April, but during the warm weather which set in 
about the middle of May their formation was only rarely observed. 
Apparently spring is a time of active propagation with the alga. 
The zoogonidia (Fig. 1, J) are rounded or pear-shaped, 
uninucleate, 6’25-8'5ix in diameter, biciliate, the cilia being inserted 
at the somewhat pointed hyaline anterior end where, placed laterally, 
is the small red pigment-spot. The chloroplast is more or less 
parietal and contains small starch-grains, but no pyrenoid was 
observed ; one or more vacuoles are often present. The zoogonidia 
are actively motile only for a few minutes, soon becoming quiescent, 
settling down and forming new individuals as already described. 
On one occasion numerous swarm-spores, apparently derived from 
the Dicranochcete were observed to have four cilia, but as there 
was some doubt as to whether they actually did belong to the alga 
or not, their fate was not observed. However, at another time, in a 
preparation which contained large numbers of quiescent zoogonidia, 
undoubtedly of Dicranochcete, many of these were seen to be larger 
than usual (their longest diameter being about 11*3/*) and to possess 
two very conspicuous red pigment-spots (see Fig. 1, K). These 
had lost their cilia, but were certainly derived by fusion of two of 
the swarm-spores as they were exactly twice the size of the ordinary 
1 Iqc. cit., p. 366. 
