CURREY, ON FRESH=-WATER ALG. 211 
readers of this Journal, I would venture to express a hope 
that they may be carefully watched. It is not, I think, im- 
probable that they may prove to be undeveloped forms 
either of some species of Chytridium or Rhizidium, or of the 
genus Pythium; but without following out their develop- 
ment, this point cannot be decided. The only plant I know 
which at all resembles them is Chytr idium apiculatum 
described in Dr. Braun’s monograph of the genus Chytridium, 
and figured by him in Pl. V , fig. 10, of that monograph ; but 
it will be seen, by comparing his ‘ficures with fig. 4, above 
referred to, that there is a marked diffe erence In fori between 
his species and the present organisms. 
Pythium is a genus separated from Achlya and Saproleg- 
nia, by Dr. Pr inesheim, in his paper on the Saprolegniez, 
in the last part of the ‘ Jahrbiicher ftir wissenschaftliche 
Botanik.’ The distinctive features of the genus are—l1st; 
that the contents of the sporangium are ejected before the 
formation of the zoospores, and out of the mass thus ejected, 
but which adheres to the sporangium, the zoospores are 
subsequently developed; 2dly, that the oogonia, or spore 
cases, produce only one resting spore, instead of several, as is 
the case in Saprolegnia and Achlya. 
I have stated that the parasitic Alge just described weré 
attached to a species of Spirogyra, and I may mention (as it 
has not been often seen), that several of the resting spores 
of the Spirogyra, to which the parasites were not attached, 
commenced germination during my observations. The ger- 
mination of these spores is a matter of some interest. It 
was first mentioned by Vaucher fifty years ago; afterwards 
Dr. Hassall, in his ‘ British Fresh-water Algze,’ considered 
Vaucher to have been altogether mistaken; but some years 
later the germination was again noticed by Dr. Pringsheim 
and by the late Professor Smith, and the correctness of 
Vaucher’s observations placed beyond doubt. In figs. 6; 7, 8; 
and 9, Pl. IX, [have drawn some of these germinating spores. 
At the period of germination they consist of three membranes, 
the imner one enclosing the cell contents, which become 
green just before the germ breaks forth. In fig. 7; the outer 
membrane, which is seen loosely attached, was colourless ; 
the second membrane, which (see figs. 7 and 8), has opened; 
to give exit to the germ, was at this period of a pale brown 
colour, and transparent. In fig. 8 the young germ has be- 
come three- celled, and there is a slight tendency in the 
endochrome to assume a spiral form, and the remnant of the 
spore is still attached. In fig. 9 the germ has become free, 
and the endochrome more visibly spiral. 
