92 
LIFE HISTORY OF A FILIFORM ALGA. 
formed similar in size and appearance to the androspores, 
from which the dwarf male plants are seen to be produced. 
This ovate body, nestling within its parent cell, is seen to be 
furnished near its paler apex with vibratile cilia. When 
mature, the enclosing cell is ruptured, and the imprisoned 
zoospore, endowed with active motion, makes its escape. 
In its movements through the water it seems impossible to 
distinguish this new zoospore from the zoospores, or andro¬ 
spores, of the short cells. Life them, it moves about for 
some time, then becomes sluggish, and ultimately conies to 
rest. The cilia are absorbed, and the pale end of the zoospore 
is attached to some object but not as in the previous instance 
to any special cell of the parent plant, nor in any proximity to 
the oogonium. Alike as they are in size, form, and movement, 
they are different in their origin and in their destiny. 
When, at length, these asexually produced zoospores come 
to rest, they form at the base a kind of clasping radicle, or 
more or less lobed expansion, by means of which they attach 
themselves ; then there follows a lengthening or expansion 
upwards, which in process of time is cut off by a septum from 
the basal cell, and becomes the first cell of a new plant, or 
rather the second, including the basal cell, which is persistent 
and remains through the whole life of the plant. Hence 
the basal cell in all perfect filaments of (Edogonium threads, 
whether proceeding from an asexual zoospore or the zoospores 
of a resting spore, is always more or less bulging, or clavate, 
with a spreading, discoid, or somewhat lobed base. It is 
unnecessary to follow the growth of this young plant into a 
filament, in all respects resembling its parent. 
We now return to the fertilised resting spores from which 
we recently diverged. We will suppose that the old plant 
has decayed and nothing remains but these quiescent spores, 
which are now sunk to the bottom of the pond or nestling in 
the axils of some aquatic plant. In due time, but always 
after some period of rest, these spores exhibit evidences of 
vitality, at first by becoming more greenish in color. And 
soon it will be found that a special membrane has been 
formed around the cell contents. Upon germination slit-like 
openings are formed in the old spore membrane, and the new 
inner membrane, and the contents escape, surrounded by an 
exceedingly delicate covering. The contents are now not a 
single oval body, but composed of fcur greenish oval masses, 
each surrounded by a hyaline membrane. Now and then, by 
abortion, there are only two or three oval masses, but the 
normal number is four. After the four cells have remained 
some time enclosed in the hyaline covering, this becomes 
