§o L. Beeslcy. 
The life-cycle from zoospore to zoospore was watched day by 
day for many generations of zoospores, and no other method of 
reproduction was observed. Zoospores continue to be formed right 
through the winter, and no resting zoospores have been observed. 
They are not, however, formed in such large numbers during the 
winter, and do not germinate so readily. 
Many different species of diatoms grow on the coverslips along 
with the Alga, and filaments of the thallus in their growth may 
penetrate beneath the diatoms, or if the latter are small, may grow 
completely round them and enclose them. Many of these diatoms 
are of relatively very large size and may grow in enormous num¬ 
bers, and it may be noted in passing that in January and February, 
1903, they lost all their brown colouring matter and the contents 
appeared a vivid green. This was common apparently in most of 
the different species, and was of such frequent occurrence that 
coverslips were covered bright green to the naked eye solely by the 
diatoms. 
The copious growth of diatoms —which require a large amount 
of silica for their composition—the firmness with which the Alga 
becomes attached to glass coverslips, the fact that in the natural 
conditions the alga grows on grains of sand and flint, all point to 
the conclusion that the Alga is favoured by silica. This is con¬ 
firmed by the fact that while the Alga grows on glass coverslips 
immersed in the trough, it will not grow on the inner porcelain 
surface of the trough itself. 
It is interesting to notice that this Alga is attacked by what in 
all probability is one of the Chytridiaceous fungi, although the 
position of this fungus has not yet been determined. 
There may arise either from the tip of a filament of the Alga, or 
laterally, a small circular swelling or “ blister,” which grows slightly 
in size until it is about as large as a zoospore of the Alga. It is 
quite colourless, and its contents are twelve to twenty minute 
colourless spores. In time this sporangium bursts and the spores 
issue, the containing envelope with a rent in the wall being quite 
visible. In running water, these spores are at once swept away, and 
it seems reasonable to suppose that they are carried by the water 
current to fresh filaments of the Alga, and so infect them. This 
fungus may be seen attacking the Alga in all stages, from the fully 
grown thallus to the young filament which has just issued from 
the germinating zoospore (Fig. 12). The contents of a cell so 
attacked turn reddish-brown, plasmolize to the centre and the cell 
