210 CURREY, ON FRESH-WATER ALGAE. 
ing their character as spores, it 1s difficult to see why a dif- 
ferent rule should be applied to the Alge. 
Cohn and Wichura moreover consider that the increase 
by self-division is irreconcileable with the idea of a spore. 
In speaking of the red cells of Chlamydococcus pluvialis 
they express a doubt whether, in those cells, imcrease by 
self-division takes place, but assert, that if such should prove 
to be the case, it would be conclusive against their being 
spores, considering self-division (if I understand them right) 
to be a process of vegetative development distinct from 
germination. ‘These observations are worthy of the careful 
attention of microscopists, and without venturing an opinion 
as to their correctness, I would only remark, that if the rest- 
ing cells of Chlamydococcus and Stephanosphera are not 
to be considered spores, that character must also be denied 
to the resting cells of idogonium, Bulbocheete, Draparnaldia, 
Spheroplea, and Volvox, if, as is more than probable, there 
should be detected in these latter cells,—1st, an increase in 
growth, after becoming quiescent, or, 2dly, increase by self- 
division. 
2. I now proceed to notice some minute parasitic organisms, 
which will be best dealt with by simply describing them, 
inasmuch as it is impossible, with any certainty at least, to 
assign them a definite place amongst the fresh-water Algze. 
Their form is that of small globular vesicles, furnished with 
a stalk, the length of which is sometimes about equal to the 
diameter of the vesicle, sometimes considerably greater. I 
have observed them growing upon zoospores, and also upon 
the large oval resting spores of a species of Spirogyra. The 
zoospores were of a bright green colour, and of rather a small 
size, as will be seen by refering to fig. 4, which represents one of 
them magnified 220 diameters, and withthe parasites attached. 
The latter are quite colourless, and the globular head ex- 
hibits a well-defined nucleus. The zoospores upon which they 
grew were in the most active motion, revolving first in one 
direction and then in another, looking and as if they were 
attempting, by the rapid changes of their movements, to 
shake off and rid themselves of the incubus of the parasites. 
Not having seen the zoospores in their parent cell, I am 
quite unable to say from what plant they were produced. 
The number of the parasites on the zoospores was variable, 
not, I think, exceeding five or six on any one zoospore ; but, in 
the case of the Spirogyra (fig. 5), they grew so thickly as 
almost to conceal the spore, the individuals being precisely 
similar in form and appearance to those on the zoospore. 
Should these bodies come under the notice of any of the 
