ON THE RESTING-SPORES OF HDOGONIUM. 151 
the inner one, as shown in figs. 8,9. After the four cells 
have remained some time enclosed in the hyaline covering, 
this becomes resorbed subsequently, and the four cells lie still 
and motionless; but after the course of a short time there 
sets in a remarkable change—the cells burst, namely, at one 
end, by means of an annular slit, and the apex, separated 
thereby from the remainder of the cell-membrane, becomes 
raised up like a lid. Through the circular opening the cell- 
contents now emerge, which, at the part turned towards the 
opening, is colourless (fig. 11). This apex moves with vigorous 
motion backwards and forwards, and, after the brief space 
of an hour, the cell-contents, in the form of a zoospore, leave 
their place of detention, which we now find to be a doubly 
contoured cell-membrane (figs. 1O—13). The little zoospore 
wheels in a lively manner about with a circling movement, 
whereby the colourless point becomes directed downwards 
towards the mirror of the microscope. Its appearance is 
puzzlingly like that of an ordinary zoospore, and, like it, it 
possesses an oval form and a lighter apex, furnished with a 
crown of cilia, which during the motion is always directed 
forwards. After the course of some time the movements 
become faint, and finally cease altogether. The cilia disap- 
pear, and the light end becomes elongated into a root, which 
sometimes becomes formed into an organ of attachment, 
quite like that which is produced in the germination of the 
ordinary zoospores (figs. 14—19). The rounded end of the 
germinating zoospore acquires a little point-like apex (figs. 
15—18), indeed, herein much resembling the ordinary zoo- 
spores. This young unicellular growth becomes divided by 
a transverse septum, and a little two-celled Gidogonium has 
now originated. 
From each spore produced by fructification there are thus 
formed, in general, four Cidogonium-plants. 
Through Pringsheim’s researches we already know the 
development of the resting spores of an algal species, Bulbo- 
chete intermedia, which much approaches CEdogonium ; but 
though, indeed, its development agrees with Cdogonium, 
there are likewise found considerable dissimilarities. Ac- 
cording to Pringsheim,* the mature Bulbochete-spore ger- 
minates in the following manner :—The spore, after its exit 
from the sporangium, assumes an oval form, whereupon its 
contents become divided into four masses. The cell-mem- 
brane increases in size, but simultaneously diminishes in 
thickness, whereupon the four masses become surrounded 
* * Jahrbiicher fiir wissensch. Botanik,’ p. 55 (1858). 
