90 
LIFE HISTORY OF A FILIFORM ALGA. 
thread may have several oogonia, although they are usually 
scattered over the filament, and not contiguous. The striae, 
or caps, at the apex of the oogonium indicate that the oospore 
has been developed in one of the youngest cells. Near the 
top, or certainly above the middle of the oogonium, is a small 
hole perforated through the wall of the oogonium. It is 
through this opening only that any small body can find 
entrance to the enclosed oospore, and it is through this 
opening that fertilisation is effected. 
Leaving the oogonia for a while, we will traverse with our 
eyes one of the filaments, to see if we can trace any other 
cell modification, and by careful observation we at length find 
from four to six short cells, not more than half as long as 
broad, lying together in one part of the filament towards the 
apex, the whole six short cells not occupying so much in 
length as any one of the vegetative cells. These short cells 
are the spore cells, or androsporangia, of the male organs. 
As there is no other similar mode of reproduction amongst 
Algae, and this rather a complicated one, I must ask you to 
follow me into the details of the process. 
I have said that these four, five, or six short cells in the 
filaments are destined to produce the male organs; the 
female, or oogonium, containing the oospore, or unfertilised 
egg, being seated in the same filament, lower down. When 
mature and the fulness of time is come, the outer wall of 
each of these short cells, or androsporangia, is ruptured, and 
about two zoospores of a peculiar kind called androspores 
make their escape. These are green oval bodies, paler at 
one end, where they are furnished with a fringe of movable 
cilia. By means of these cilia, the newly-escaped zoo¬ 
spores move about in the water actively for a time, 
apparently enjoying their freedom, until at length they grow 
more and more sluggish until finally they attach themselves 
by the paler end, and another change takes place. It must 
be remarked here, that when these zoospores escape from 
their androsporangia, on a roving commission, they evidently 
have a definite work to accomplish, although they appear to 
be only indulging in frivolous pastime, because when they 
settle down and attach themselves by their paler end and 
abandon all frivolity, they invariably fix themselves to the 
cell immediately beneath the oogonium. I will leave you to 
explain or moralise upon this fact as you please, but to me it 
is one of extreme suggestiveness, that two or three or half-a- 
dozen active little bodies, without sense or sensibility, or 
instinct, should quit their parent cells and travel down the 
filament, it may be for half its length, and then attach them- 
