150 ON THE RESTING-SPORES OF @DOGONIUM. 
gonium will present a contribution to the natural history of 
these lowly but interesting plants. 
Last summer I encountered, in a little collection of water 
in the neighbourhood of Upsala, some sterile Gidogonia, en- 
tirely covered over by Closteria. Chiefly with the view that 
these latter might develop themselves, I placed the mass of 
Algze in a little water, and, at the expiration of some weeks, I 
had the pleasure to find several hundreds of the Closteria in 
conjugation. I wished now to follow the further development 
of the newly formed spores ; but the rapacity of a little species 
of Cypris rendered this wish of no avail. During the time, the 
(Xdogonia also had begun to fructify; but as I had already 
had opportunity to observe the fructification in several species 
of Gidogonium, I paid no attention to it. This is the cause 
why I cannot give any description as to the species of the 
present Cidogonium, the development of which I observed. 
The water, wherein the Algze were kept, evaporated, so that 
towards the close of the month of September of last summer 
there remained behind but a green dry mass. This was laid 
aside till the middle of the month of January of the present 
year, when it was covered over with water. In the course of 
a month this green slime, which covered the bottom of the 
vessel, was examined, and in it, besides a quantity of minute 
green Algee of the genus Scenedesmus, were found also some 
minute @dogonium-plants, much resembling those which ori- 
ginate from the germination of the zoospores. This prompted 
me to try to discover the mode whereby they proceed from 
the spores ; but it was only in the month of March that I was 
able to find a sufficient number of germinating spores in order 
to follow out consecutively the remarkable mode in which 
they are developed. 
Previous to germination, the spore (PI. III, fig. 1) has an 
egg-shaped figure ; the cell-contents are densely crowded, and 
composed of minute brownish-green granules, closely sur- 
rounded by a distinct cell-membrane. Outside this membrane 
there is found, besides, a quite distinct cell-membrane. Upon 
germination there are formed in both membranes slit-like 
openings, whereupon the cell-contents emerge, surrounded 
by an extremely delicate hyaline covering (figs. 2 and 3). The 
cell-contents are composed, not of one, but usually of four 
green masses, each surrounded by its cell-membrane. Some- 
times also, as it appears, abnormally, the masses are two or 
three in number (figs. 6, 7). The four cells which proceed 
from germination possess an oval form, and their cell-mem- 
brane is hyaline. After the contents of the spore have 
emerged, there remains behind the outer membrane, enclosing 
